Visions of Spaceflight: Circa 2001 (1984)

The Mars Orbiter and Mars Lander (center) cast off the Interplanetary Vehicle (upper left) before aerobraking in the upper atmosphere of Mars. Image credit: Michael Carroll.

The year 1984 was nearly equidistant between the first Moon landing of 1969 and the evocative year 2001. The Space Shuttle, flown into orbit for the first time on 12 April 1981, had been declared operational by President Ronald Reagan at the end of its fourth mission on 4 July 1982. In his 25 January 1984 State of the Union Address, Reagan gave NASA leave to use the Shuttle to launch and assemble its long-sought, long-postponed low-Earth-orbit (LEO) Space Station.

Space supporters could be forgiven for believing that, after a gap in U.S. piloted space missions that spanned from Apollo-Soyuz in July 1975 to the first Shuttle mission, a new day was dawning: that Shuttle and Station would lead in the 1990s to piloted flights beyond LEO. Surely, Americans would walk on the Moon again by 2001, and would put boot prints on Mars not long after.

There were, of course, some problems: despite being declared operational, Shuttle operations had yet to become routine. Despite some high-flown rhetoric at the time it was announced — President Reagan spoke of following "our dreams to distant stars" — the Station the White House agreed to fund was meant to serve as a microgravity laboratory, not a jumping-off place for voyages beyond LEO. Hardware for any "spaceport" function it might eventually have would need to be bolted on later, after some future President gave the word.

In addition, NASA's robotic exploration program remained a shadow of its former self. There would, for example, be no U.S. robotic probe in the international armada to Halley's Comet in 1985-1986.

Nevertheless, with American astronauts in space again and concept artists hard at work on tantalizing visions of sprawling space stations, very few foresaw rough waters ahead. It seemed the perfect time to revive advance planning for missions to the Moon and beyond, which had been virtually moribund in the U.S. since the early 1970s.

Advance planning revived first outside of NASA. Participants in the 1981 and 1984 The Case for Mars conferences, mindful of how Apollo had left no long-term foothold on the Moon, developed a plan for establishing and maintaining a permanent Mars base. The Planetary Society, with 120,000 members the largest spaceflight advocacy group on Earth, helped support the conferences.

The Planetary Society had grown rapidly following its founding in 1980 in large part because its President was planetary scientist Carl Sagan. His 1980 PBS television series Cosmos had done more to popularize space exploration than any public outreach effort since Wernher von Braun's 1950s collaborations with Walt Disney and Collier's weekly magazine.

In 1984, The Planetary Society asked the Space Science Department of Science Applications International Corporation (SAIC) in suburban Chicago, Illinois, to outline three piloted space projects for the first decade of the 21st century. These were: an expedition to scout out a site for a permanent lunar base; a two-year journey to a near-Earth asteroid; and, most ambitious, a three-year mission to land three astronauts on Mars.

The three projects were not meant to occur in the order in which they were presented, and any one of them could stand alone. In its report to The Planetary Society, the six-man SAIC study team declared that "any. . .would be a commanding goal for future U.S. space exploration."

The Planetary Society paid SAIC a modest fee. In their foreword to the SAIC report, Sagan and his lieutenant, Jet Propulsion Laboratory engineer Louis Friedman, called the team's work "a labor of love."

Space missions of an international character were of interest to The Planetary Society; it saw in them a means of reducing geopolitical tension on Earth and of dividing the cost of exploration among the space-faring nations. In their foreword, Sagan and Friedman wrote of their hope that the study would "stimulate renewed interest in major international initiatives for the exploration of nearby worlds in space." The SAIC team did not, however, emphasize this; apart from the European Space Agency-provided Spacelab modules from which the pressurized modules of its spacecraft would be derived, there was little evidence of international involvement in its proposed projects.

The SAIC team assumed that NASA would convert the Space Station into an LEO spaceport at the turn of the 21st century. The U.S. civilian space agency would use the Space Shuttle fleet to launch to the Station hangars, living accommodations for crews in transit to destinations beyond LEO, remote manipulators, propellant storage tanks, and auxiliary spacecraft such as Orbital Transfer Vehicles (OTVs). Parts and propellants for the team's piloted Moon, asteroid, and Mars spaceships would also reach the Station on board Shuttle Orbiters.

For its lunar base site survey mission, the SAIC team assumed no Space Shuttle upgrades. The standard Shuttle Orbiter could in theory carry up to 60,000 pounds (27,270 kilograms) to LEO in its 15-by-60-foot (4.6-by-18.5-meter) payload bay. Of this, 5000 pounds (2268 kilograms) would comprise Airborne Support Equipment (ASE) — that is, hardware for mounting payloads in the payload bay, providing them with electricity, thermal control, and other required services, and deploying them in LEO.

Schematic of a mission to deliver cargo to the lunar surface. The mission is described in the post text. Please click on the image to enlarge. Image credit: Science Applications International Corporation.

Schematic of a mission to deliver astronauts to the lunar surface and return them to Earth after 30 days. The mission is described in the post text. Please click on the image to enlarge. Image credit: Science Applications International Corporation.

SAIC's lunar mission closely resembled the one it had presented in its December 1983 report to the National Science Foundation (please see "More Information" below). The mission — for which SAIC gave no start date — would need a total of 12 Shuttle launches and four piloted and automated "sorties" to the Moon.

SAIC planners assumed that the beefed-up LEO Station would normally include in its fleet of auxiliary vehicles two reusable OTVs, each with a fully fueled mass of about 70,400 pounds (32,000 kilograms). These would suffice for the lunar project, but more OTVs — including some considered expendable — would be needed for the asteroid and Mars missions.

At the start of each lunar sortie, a "stack" comprising OTV #1, OTV #2, and a lunar payload would move away from the Station. OTV #1 would fire its twin RL-10-derived engines at perigee (the low point in its Earth-centered orbit) to push OTV #2 and the lunar payload into an elliptical orbit. OTV #1 would then separate and fire its engines at next perigee to lower its apogee (the high point in its orbit) and return to the Space Station for refurbishment and refueling. OTV #1 would burn 59,870 pounds (27,215 kilograms) of propellants.

OTV #2 would fire its engines at next perigee to place the lunar payload on course for the Moon. Depending on the nature of the payload, OTV #2 would then either fire its engines to slow down and allow the Moon's gravity to capture it into lunar orbit or would separate from the lunar payload and adjust its course so that it would swing around the Moon and fall back to Earth.

The SAIC team envisioned that OTV #2 would be fitted with a reusable aerobrake heat shield. After returning from the Moon, it would skim through Earth's upper atmosphere to slow itself, then would adjust its attitude using small thrusters so that it would gain lift and skip up out of the atmosphere. At apogee, it would fire its twin engines briefly to raise its perigee out of the atmosphere. OTV #2 would then rendezvous with the Station, where it would be refurbished and refueled for a new mission.

The SAIC team's lunar base survey mission would begin with Sortie #1, which would include no crew. OTV #2 would swing around the Moon after releasing a payload comprising a one-way lander bearing a pair of nearly identical 15,830-pound (7195-kilogram) lunar surface vehicles. Each vehicle would comprise a pressurized rover and a trailer. The lander would descend directly to a soft landing in the proposed lunar base region.

Like Sortie #1, Sortie #2 would include no crew. Unlike Sortie #1, Sortie #2 would see OTV #2 capture into a 30-mile-high (50-kilometer-high) lunar orbit. There it would deploy an unfueled single-stage Lunar Excursion Module (LEM) lander. OTV #2 would then fire its twin engines to depart lunar orbit for Earth. After aerobraking in Earth's atmosphere, it would return to the Station.

The first piloted sortie, Sortie #3, would see OTV #2 deliver to lunar orbit four astronauts in a pressurized crew module. They would pilot the OTV #2/crew module combination to a docking with the waiting LEM. The crew would board the LEM, load it with propellants from OTV #2, then undock. OTV #2 would fire its engines to depart lunar orbit, fall back to Earth, aerobrake in the atmosphere, and return to the Station.

The astronauts, meanwhile, would descend in the LEM to a landing near the one-way lander. After unloading the twin rover-trailers, the four-person crew would split into two two-person crews and begin a 30-day survey of candidate base sites within the 30-mile-wide (50-kilometer-wide) proposed lunar base region.

In addition to providing living quarters, the rover-trailers would each carry 2640 pounds (1200 kilograms) of science instruments for determining surface composition, seismicity, and stratigraphy at candidate base sites, plus a scoop or blade for moving large quantities of lunar dirt. They would rely on liquid oxygen-liquid methane fuel cells for electricity to power their drive motors.

The rover-trailers would travel together for safety; if one broke down and could not be repaired, the other could return all four astronauts to the waiting LEM.

Travel in harsh sunlight would be avoided. SAIC assumed that the rover-trailer combinations would spend most of the two-week lunar daylight period parked at a "base camp" under reflective thermal shields, venturing out for only a few 24-hour excursions. They would travel continuously during the two-week lunar night, however, their way lit by headlights and sunlight reflected off the Earth.

Sortie #4 would see OTV #2 and the crew module return without a crew to lunar orbit. The crew, meanwhile, would park the rover-trailers under the base camp thermal shields, load the LEM with samples, photographic film, and other souvenirs of their rover-trailer traverses, and ascend in the LEM to lunar orbit to rendezvous and dock with the OTV #2/crew module combination. They would then undock from the LEM, depart lunar orbit, aerobrake in Earth's atmosphere, and rendezvous with the Station. The SAIC planners proposed that the orbiting LEM and parked rover-trailers be put to use again during the initial phase of lunar base buildup.

Asteroid mission Earth departure would require five OTVs operating in series over 48 hours. SAIC proposed a similar departure method for all three of its missions. Please click on the image to enlarge. Image credit: Science Applications International Corporation.

For its piloted asteroid mission, SAIC considered eight mission plans taking in two asteroids in the Main Belt between Mars and Jupiter and four Earth-approaching asteroids. Three of the Earth-approaching asteroids were hypothetical — asteroid hunting was ramping up in the early 1980s, so the SAIC team sought to anticipate new discoveries. The team settled on a two-year voyage that would include a wide swing out into the Main Belt. There the spacecraft would fly past asteroid 1577 Reiss.

The main target of the mission would, however, be the Earth-approaching asteroid 1982DB, in 1984 the most easily accessible Earth-approaching asteroid known. Now named 4660 Nereus, nearly 40 years after its discovery it remains among the most accessible known asteroids.

Nine upgraded Shuttle Orbiters would launch parts and propellants for the asteroid mission spacecraft and the OTVs necessary to launch it from Earth orbit. The "65K" Shuttles SAIC invoked would be capable of launching 65,000 pounds (29,545 kilograms) to the Space Station. As with the lunar base survey mission, ASE would make up 5000 pounds (2268 kilograms) of the total. Following assembly and checkout, the piloted asteroid mission spacecraft/OTV stack would move away from the Station.

A total of five OTVs would be needed to launch the asteroid mission spacecraft out of Earth orbit. OTV #1 would ignite at the stack's perigee to raise its apogee. It would then separate and fire its engines at next perigee to lower its apogee, re-circularizing its orbit so it could return to the Station. OTV #2 would ignite at next perigee to boost the stack's apogee higher, then would detach and aerobrake in Earth's atmosphere to return to the Station. OTV #3 and OTV #4 would do the same.

The time between perigees would increase with each burn: the five-burn sequence would need about 48 hours, with nearly 24 hours separating the OTV #4 and OTV #5 perigee burns. On 5 January 2000, OTV #5 would fire its twin engines at perigee, launching SAIC's asteroid mission spacecraft onto a Sun-centered path toward 1577 Reiss and 1982DB. OTV #5, its propellant tanks empty, would then be cast off.

Of the spacecraft SAIC proposed, the asteroid mission spacecraft would venture farthest from the Sun. Please click on the image to enlarge. Image credit: Science Applications International Corporation.

With the Earth-Moon system shrinking behind them, the three-person crew would spin up their spacecraft. Twin 81.25-foot-long (25-meter-long) hollow arms, each carrying a solar array and a radiator panel, would link twin habitat modules to a cylindrical central hub. Habitats, booms, and hub would spin three times per minute to create acceleration in the habitats, which the crew would feel as a continuous pull of 0.25 Earth gravities.

SAIC lacked data on whether 0.25 gravities would be sufficient to mitigate the deleterious effects of weightlessness (indeed, such data do not exist at this writing). The team explained that its choice of 0.25 gravities constituted "a compromise between the desire to have a near normal gravity, a short habitat arm length, and a slow spin rate."

A logistics supply module and two propulsion systems would be linked to the central hub's aft end. The main propulsion system, which would burn liquid methane and liquid oxygen, would be used for course corrections during the long trip from Earth to 1982DB and for departure from 1982DB. The storable-bipropellant secondary system would be used to perform 1982DB station-keeping maneuvers and course corrections during the short trip from 1982DB to Earth.

The hub's front end would have linked to it an experiment module, an "EVA station" airlock module for spacewalks, and a conical Earth-return capsule with a 37.4-foot (11.5-meter) flattened cone ("coolie hat") aerobrake. The experiment module would carry attached to its side a 16.25-foot (five-meter) radio dish antenna for high-data-rate communications.

The modules and propulsion systems on either end of the hub would spin as a unit in the direction opposite the hub, arms, and habitats, so would appear to remain motionless. Astronauts inside the hub-attached parts of the asteroid mission spacecraft would experience weightlessness.

The crew would point the Earth-return capsule aerobrake and the asteroid spacecraft's twin solar arrays toward the Sun, placing radiators, propulsion systems, logistics module, hub, hollow arms, experiment module, EVA station, and Earth-return capsule in protective shadow. In the event of a solar flare, the crew would use the spacecraft's structure as radiation shielding: they would retreat to the logistics module, placing aerobrake, Earth-return capsule, EVA station, experiment module, hub, and logistics module between themselves and the active Sun.

During their two-year mission, the asteroid mission crew would spend about 23 months carrying out "cruise science." Four hundred and forty pounds (200 kilograms) of the spacecraft's 1650-pound (750-kilogram) cruise science payload would be devoted to studies of human physiology in space, and 375 pounds (170 kilograms) would be used to perform solar observations and other astronomy and astrophysics studies. In addition, the spacecraft would carry 55 pounds (25 kilograms) of long-duration exposure samples on its exterior. These swatches of spacecraft metals, foils, paints, ceramics, plastics, fabrics, and glasses would be retrieved by spacewalking astronauts before the end of the mission.

SAIC's asteroid mission spacecraft would fly past 4.2-kilometer-wide 1577 Reiss at a speed of 2.8 miles (4.7 kilometers) per second 14 months into the mission (2 March 2001) and would intercept 1982DB just over six months later, on 12 September 2001. The 1577 Reiss flyby would occur while asteroid and spacecraft were 216.7 million miles (348.7 million kilometers) from the Sun. The spacecraft would spend 30 days near 1982DB, during which time Earth would range from 55 million miles (90 million kilometers) distant on 12 September 2001 to 30 million miles (50 million kilometers) away on 12 October 2001.

While close to 1577 Reiss, the crew would for the first time activate the "asteroid science" equipment packed in the experiment module. They would bring to bear on the Main Belt asteroid a 220-pound (100-kilogram) package of remote-sensing instruments, including a mapping radar and instruments for determining surface composition. They would also image 1577 Reiss using high-resolution cameras with a total mass of 110 pounds (50 kilograms).

The asteroid science instruments would be put to use again as the spacecraft closed on 1982DB. During approach, the crew would locate the asteroid precisely in space, determine its rotational axis and rate, and perform long-range mapping. They would then despin the spun parts of their spacecraft and, using the secondary propulsion system, halt a few hundred miles/kilometers from 1982DB to perform detailed global mapping. This would enable selection of sites for in-depth investigations.

The astronauts would then use the secondary propulsion system to place the spacecraft in a "stationkeeping" position a few tens of miles/kilometers away from 1982DB. Every three days they would move even closer — to within a few miles/kilometers — so that a pair of space-suited astronauts could leave the EVA station module airlock to explore the asteroid's surface.

The astronauts would each use a Manned Maneuvering Unit (MMU) to transfer from the spacecraft to 1982DB. The asteroid mission MMUs, modeled on the MMU first tested during Space Shuttle mission STS-41B (3-11 February 1984), would use gaseous nitrogen as propellant.

The exploration of Earth-approaching asteroid 1982 DB. Image credit: Michael Carroll.

The SAIC team noted that 1982DB would have "negligible gravitational attraction," so the asteroid mission spacecraft would be unable to orbit it in a conventional sense. Spacecraft and asteroid would instead share nearly the same orbit around the Sun. 1982DB would, meanwhile, rotate at some unknown rate. The asteroid's rotation would mean that astronauts at a site of interest on its surface would tend to be move away from their spacecraft. In fact, if 1982DB rotated quickly enough, astronauts on its surface might pass out of sight of the spacecraft during their four-hour "asteroid-walks."

The SAIC team judged that loss of radio and visual contact with the surface crew would be undesirable, so proposed that the astronaut left behind on the spacecraft perform station-keeping maneuvers to match 1982DB's rotation; that is, that the astronaut keep his or her shipmates in sight by maintaining a "forced circular orbit" around 1982DB. The team budgeted enough secondary propulsion system storable propellants for a velocity change of 32.5 feet (10 meters) per second per surface visit.

If 1982DB were found to rotate slowly, then the velocity change needed to maintain the spacecraft in its forced orbit would be reduced. In that case, only astronaut stamina, the supply of MMU propellant, and the mission's planned 30-day stay-time near 1982DB would limit the number of surface visits. The SAIC team envisioned that the astronauts might explore as many as 10 sites. After each surface excursion, the spacecraft would resume stationkeeping several tens of miles/kilometers away from 1982DB.

The SAIC team assumed that 1982DB would measure 0.62 miles (one kilometer) in diameter. They noted that an asteroid of that size would have roughly the same area as New York City's Central Park (1.32 square miles/3.41 square kilometers). Based on this comparison, they judged that "a 30-day stay time should provide ample time to complete a thorough investigation of the object." (I would argue that 10 four-hour visits to Central Park would be nowhere near sufficient to characterize it, but presumably 1982DB would lack the many unique amenities and diverse population of that iconic urban oasis.)

During their surface visits, the astronauts would deploy four small and three large experiment packages on 1982DB and would collect a total of 330 pounds (150 kilograms) of samples. The 110-pound (50-kilogram) small experiment packages would each include a seismometer and instruments for measuring temperature and determining surface composition. The 220-pound (100-kilogram) large packages would include a "deep core drill," a sensor package for insertion into the core hole, and a mortar.

After the spacecraft resumed station-keeping for the last time, the crew would remotely fire the mortars in succession to send shockwaves through 1982DB. The seismometers would register the shockwaves, enabling scientists to chart the asteroid's interior structure.

On 12 October 2001, the asteroid mission spacecraft would use the primary propulsion system for the last time to depart 1982DB. Using the secondary propulsion system, the crew would bend its trajectory so that it would almost intersect Earth. They would then spin up the spacecraft to restore artificial gravity in the hollow arms and habitats.

Three months later, they would load their samples, film, and other data products into the Earth-return capsule and undock from the spacecraft. On 13 January 2002, almost exactly two years after Earth departure, the crew would aerobrake their capsule in Earth's atmosphere and pilot it to a rendezvous with the Space Station. Meanwhile, the abandoned asteroid mission spacecraft would swing by Earth and enter a disposal orbit around the Sun.

Although designated the Mars Exploration Vehicle in this illustration, SAIC designated this three-part spacecraft the Mars Outbound Vehicle (MOV) in its report text. It would become the Mars Exploration Vehicle only after it cast off the Interplanetary Vehicle (lower left). Please click on the image to enlarge. Image credit: Science Applications International Corporation.

SAIC's third proposed project, the first piloted Mars landing, would employ a four astronauts and six spacecraft (not counting OTVs). The largest spacecraft combination, the 265,880-pound (120,600-kilogram) Mars Outbound Vehicle (MOV), would comprise the 43,870-pound (19,600-kilogram) Interplanetary Vehicle (spacecraft 1), the 25,130-pound (11,400-kilogram) Mars Orbiter (spacecraft 2), and the conical 83,555-pound (37,900-kilogram) Mars Lander (spacecraft 3). The Mars Orbiter and Mars Lander together would comprise the Mars Exploration Vehicle.

The Interplanetary Vehicle would resemble the SAIC team's asteroid mission spacecraft, though it would lack an Earth-return capsule and would move through space with its logistics module pointed toward the Sun. The Interplanetary Vehicle's hub, twin hollow arms, and twin habitats would revolve three times per minute.

The Interplanetary Vehicle's EVA station would link it to the Mars Orbiter, a bare-bones, non-rotating vehicle made up of a single habitat module and hollow arm, a solar array, a radiator, a radio dish antenna, an EVA station, an unspecified propulsion system, and the conical Mars Departure Vehicle (spacecraft 4). The Mars Orbiter EVA station would link it to the Mars Lander ascent stage. The Mars Lander would include a 175.5-foot-diameter (54-meter-diameter) flattened-cone aerobrake.

The Earth Return Vehicle would leave Earth first but reach Mars 30 days after the Mars Outbound Vehicle. Please click on the image to enlarge. Image credit: Science Applications International Corporation.

SAIC's second, smaller Mars mission spacecraft combination, the 94,600-pound (43,000-kilogram) Earth Return Vehicle (ERV) (spacecraft 5), would resemble the asteroid mission spacecraft even more closely than would the Mars mission Interplanetary Vehicle. The ERV, which would include the 9750-pound (4430-kilogram) Earth Return Capsule (spacecraft 6), would depart Earth ahead of the MOV, on 5 June 2003, but would follow a Sun-centered path that would cause it to reach Mars after the MOV, on 23 January 2004. It would leave LEO with no crew on board.

A total of five Shuttle launches, each capable of putting into LEO 60,000 pounds (27,270 kilograms), would launch ERV and OTV parts and propellants to the Station. ASE would make up 5000 pounds (2268 kilograms) of each Shuttle Orbiter payload.

Three OTVs (two based permanently at the Station plus one assembled specifically for the Mars mission) would then launch the ERV toward Mars. Each OTV would in succession ignite its engines at perigee to increase the ERV's apogee, then would separate. OTV #1 would use its twin engines to return to the Station after separation, OTV #2 would rely on its aerobrake heat shield, and OTV #3 would expend all of its propellants to place the ERV on course for Mars and be discarded. The ERV's three-orbit Earth-departure sequence would last about six hours.

The MOV with four astronauts on board would leave Earth orbit 10 days later, on 15 June 2003. Thirteen Space Shuttle launches would place MOV and OTV parts and propellants into Earth orbit. Seven OTVs would perform perigee burns over the space of a little more than two days to boost the 265,300-pound (120,600-kilogram) MOV toward Mars. Following separation, OTV #1 would ignite its engines at perigee to return to the Station; OTVs #2 through #6 would return to the Station after aerobraking; and OTV #7 would burn all of its propellants and be discarded.

The MOV would arrive at Mars on 24 December 2003, 30 days ahead of the ERV. Assuming that telemetry from the ERV indicated that it remained able to support a crew, the MOV crew would cast off the Interplanetary Vehicle (this is depicted in the image at the top of this post), strap into the Mars Lander ascent capsule, and aerobrake in the martian atmosphere. The abandoned Interplanetary Vehicle would swing past Mars and enter solar orbit.

Following aerobraking, the two-part Mars Exploration Vehicle would climb to an apoapsis (orbit high point) of 600 miles (1000 kilometers). The Mars Orbiter and Mars Lander would then separate. One astronaut would remain on board the Mars Orbiter. He or she would ignite its propulsion system at apoapsis to raise its periapsis (orbit low point) to 600 miles (1000 kilometers), giving it a circular orbit about the red planet. The three astronauts in the Mars Lander, meanwhile, would fire its engine briefly at apoapsis to raise its periapsis to an altitude just above the martian atmosphere.

As the planet rotated beneath the Mars Lander, the three astronauts would prepare for atmosphere entry and landing. As the target Mars landing site came into range, they would ignite the Mars Lander engine at apoapsis, lowering their periapsis into the atmosphere. They would cast off the aerobrake after atmosphere entry and lower to a soft landing using the Mars Lander descent engine.

Immediately after touchdown, the crew would deploy a teleoperated rover. Trailing power cables, the rover would carry a small nuclear reactor a safe distance away from the Mars Lander and bury it. The crew would then remotely activate the reactor to supply their encampment with electricity.

SAIC's Mars mission would, of course, have a range of cruise, Mars orbital, and Mars surface science objectives. The study team explained that, during the six-month Earth-Mars cruise, the astronauts on board the Interplanetary Vehicle would have at their disposal a cruise science payload identical to that carried on board the asteroid mission spacecraft.

Human physiology studies during the trip to Mars would, in addition to any scientific objectives, have a prosaic operational goal: they would emphasize keeping the Mars landing crew in good shape for strenuous activity on the planet. The astronauts would also observe the Sun for science and to detect solar flares that might cause them harm.

The one-person Mars Orbiter and three-person Mars Lander crews would have many objectives at Mars, some primarily scientific and others primarily operational. The "primary duty" of the lone astronaut on board the Mars Orbiter would be to support the surface crew, the SAIC team explained. Four hundred and forty pounds (200 kilograms) of remote sensors would enable her or him to spot threatening weather conditions near the landing site and generate detailed maps of landing site terrain and surface composition for both the crew on Mars and scientists and mission controllers on Earth.

The surface crew would have as "a major goal" the selection of a future Mars base site, the SAIC team explained. They would have at their disposal 1980 pounds (900 kilograms) of science equipment, including a 220-pound (100-kilogram) Mobile Geophysics Lab rover, 110 pounds (50 kilograms) of high-resolution cameras, four small deployable science packages with a mass of 110 pounds (50 kilograms) each, and three large deployable science packages with a total mass of 880 pounds (400 kilograms) each.

The small packages would measure temperature, detect Marsquakes, and determine surface composition, while the large packages would include a 440-pound (200-kilogram) deep-core drill, a 220-pound (100-kilogram) sensor package for insertion down core holes, and a mortar for generating shock waves that the seismometers in the small packages would register, permitting scientists on Earth to understand the subsurface structure of the landing site. The surface crew would also set up an inflatable "tent" in which they would begin examination of the 550 pounds (250 kilograms) of Mars samples they would collect for return to Earth.

As their stay on Mars reached its end, the surface crew would load their samples, film, and other data products into the Mars Lander ascent stage and blast off to rendezvous and dock with the Mars Orbiter. The nuclear reactor they left behind would power equipment long after they departed. The SAIC team suggested, for example, that it could provide electricity to a device that would extract oxygen from the martian atmosphere and cache it for future Mars base builders.

The ERV, meanwhile, would close in on Mars. Like the asteroid spacecraft, it would move through space with its Earth-return aerobrake pointed toward the Sun.

After docking with the Mars Orbiter, the reunited crew would transfer their surface and orbital Mars data products to the Mars Departure Vehicle, then would undock from the Mars Orbiter and set out in earnest pursuit of their ride home. Because launching it back onto an interplanetary path after crew recovery in Mars orbit would demand considerable quantities of propellants, the ERV would not enter Mars orbit.

Instead, to reduce overall Mars mission mass (and thus the number of Shuttle launches needed to launch it into LEO and and the number of OTVs needed to place it on course for Mars), the crew would rendezvous with the ERV as it raced past the planet on a free-return trajectory that would take it back to Earth after 1.5 orbits around the Sun and 2.5 years of flight time. This approach, which SAIC termed Mars Hyperbolic Rendezvous (MHR), resembled the Flyby Landing Excursion Mode put forward by Republic Aviation engineer R. Titus in 1966. SAIC did not reference his pioneering work.

As might be expected, the SAIC team felt it necessary to study possible contingency modes for crew recovery in the event that MHR failed. If, for example, the unmanned ERV malfunctioned en route to Mars before the crew discarded the Interplanetary Vehicle and aerobraked the Mars Exploration Vehicle into Mars orbit, the astronauts could perform a powered Mars swingby maneuver using the Mars Lander and Mars Orbiter propulsion systems, bending their course so that they would intercept Earth 2.5 years later. The crew would separate in the Mars Lander near Earth and use its aerobrake to capture into Earth orbit.

Assuming, however, that all occurred as planned, the Mars Departure Vehicle would dock with the ERV a few hours after leaving Mars orbit. As Mars shrank behind them, the astronauts would transfer to the ERV with their samples and other data products, cast off the spent Mars Departure Vehicle, and spin the ERV's arms and habitats to create acceleration.

During the 2.5-year cruise home to Earth, the astronauts would study human physiology, the Sun, and astrophysics using a science payload identical to that carried on board the Mars mission Interplanetary Vehicle and the asteroid mission spacecraft. The SAIC team suggested that they might also continue study of the samples they had collected on Mars, though they did not indicate how this would be accomplished in the absence of a sample isolation lab, instruments, and tools.

On 5 June 2006, three years to the day after they left Earth, the crew would undock in the Earth Return Capsule, aerobrake in Earth's atmosphere, and rendezvous with the Space Station. The abandoned ERV, meanwhile, would swing past Earth and enter solar orbit.

SAIC offered preliminary cost estimates for its three projects and compared them with the cost of the Apollo Program, which encompassed 11 piloted missions, six of which landed two-man crews on the Moon. A dispassionate observer might be forgiven for believing that SAIC's cost estimates were unrealistically low. Partly this was the result of Shuttle cost accounting. Taking its lead from NASA, the SAIC team calculated that the 18 Shuttle flights needed for its Mars mission would cost only $2 billion, or about $110 million per flight.

The lunar base site survey would, the SAIC planners calculated, cost only $16.5 billion, or about a quarter of the Apollo Program's $75 billion cost in 1984 dollars. The asteroid mission would be slightly cheaper, coming in at $16.3 billion. The Mars mission, not surprisingly, would be the most costly of the three. Even so, it would only cost about half as much as Apollo; SAIC estimated that it would cost just $38.5 billion.

Launch of Space Shuttle Orbiter Challenger on 28 January 1986. Image credit: NASA.

Just 15 months after SAIC turned over its study to The Planetary Society, the optimistic era of piloted mission planning that had begun with the first Space Shuttle launch drew to a close. Following the loss of the Shuttle Orbiter Challenger on 28 January 1986, at the start of the 25th Shuttle mission, advance planning did not stop; in fact, it expanded as NASA sought to demonstrate that the Shuttle and Station Programs had worthwhile long-term objectives, and thus should continue in spite of Challenger.

The rules, however, had changed. After Challenger, few planners assumed that the Space Station President Reagan had called for in January 1984 would ever become an LEO spaceport, and even fewer assumed that Shuttle Orbiters alone would suffice to launch the components and propellants needed for piloted missions beyond LEO.

Post-Challenger plans would call for a purpose-built LEO spaceport to augment the Station and Shuttle-derived heavy-lift rockets to augment the Shuttle. Both of these would increase the estimated cost of piloted exploration beyond LEO.

Color artwork in this post is Copyright © Michael Carroll (http://stock-space-images.com/) and is used by kind permission of the artist.

Sources

Manned Lunar, Asteroid, and Mars Missions - Visions of Space Flight: Circa 2001, A Conceptual Study of Manned Mission Initiatives, Space Sciences Department, Science Applications International Corporation, September 1984.

"Visions of 2010 - Human Missions to Mars, the Moon and the Asteroids," Louis D. Friedman, The Planetary Report, March/April 1985, pp. 4-6, 22.

More Information

NASA Glenn Research Center's 2001 Plan to Land Humans on Mars Three Years Ago

High Noon on the Moon (1991)

Near-Term and Long-Term Goals: Space Station and Lunar Base (1983-1984)

A New Step in Spaceflight Evolution: To Mars by Flyby-Landing Excursion Mode (1966)

Moon Suit: 1949

Image credit: R. A. Smith/The British Interplanetary Society.

The British Interplanetary Society (BIS), founded by Phillip Cleator in Liverpool in 1933, is the world's oldest organization devoted to the promotion of spaceflight. In 1936, the BIS moved its headquarters to London and launched a Technical Committee, which soon began design of a Lunar Spaceship. The Society published results of its Lunar Spaceship study in its journal in 1939, then suspended its activities for the duration of the Second World War.

A decade later, on 19 November 1949, the reconstituted and always prescient BIS hosted the Symposium of Medical Problems Associated with Space-Flight. The third paper presented was a collaboration between self-taught engineer H. E. Ross and artist R. A. Smith, two men instrumental in the pre-war Lunar Spaceship study. It focused on the problems of designing a space suit for lunar surface exploration.

The Moon, they explained, has no atmosphere (they added, however, that an atmosphere might be "present below the surface, in the caverns, galleries, and pipes of an extinct volcanic system"). Its surface undergoes extremes of temperature during its nearly month-long day/night cycle. At noon on the lunar equator, the temperature soars to an "oven-high" 120° Celsius (C). At night, it plummets to a "ferocious" -150° C.

Ross and Smith wrote that the Moon's night hemisphere has a uniform temperature. During lunar day, on the other hand, landscape "cragginess," color, and composition could create local temperature variations. This disparity meant that designing separate space suits for night and day would likely be easier than designing a single day-and-night suit (and that designing a night suit might be easiest of all). Nonetheless, Ross and Smith elected to take on the challenge of designing an "ensemble" capable of protecting its wearer at any point in the day/night cycle and anywhere on the lunar surface.

The "skin" of their Moon suit would comprise four layers: a thin, smooth exterior layer (or "cuticle") of closely woven cloth (A in the drawing below); a "thickish" layer of "cellular heat-resisting material," such as wool (B); a rubber "airtight sheath" (C); and, for the wearer's comfort, a soft inner layer (D) that would not absorb moisture. To enhance mobility, the layers would form bellows joints at knees, ankles, hips, elbows, shoulders, and wrists.

Persons familiar with the Apollo A7L lunar suit will note the absence of any active cooling layer for carrying away body heat generated during exertion. In the Apollo suit, this took the form of a fabric layer laced with water tubes. As was typical of space suit designers until at least the mid-1960s, Ross and Smith underestimated the significance of heat generated by the suit wearer's body. They assumed that air flow through an air conditioning unit (8) and, under the hottest conditions, through an auxiliary air-cooling "refrigerator" (10), would, if combined with passive moderation of absorbed or radiated heat, be sufficient to control their Moon suit's internal temperature.

Cutaway of Ross and Smith's lunar space suit including a closeup of its "skin" structure (lower right). Number and letter call-outs are defined in the post text. Image credit: R. A. Smith/The British Interplanetary Society.

The suit would be colored black from just above the knees up to the shoulders (20) and silver elsewhere (19). Black fabric would, of course, absorb sunlight, while silver fabric would reflect it. It would include a silver cape (22) that the wearer could draw over the black area to reflect sunlight or hold in escaping heat, "studs" protruding from the chest (23) to separate the cape from the suit's outer surface (thus creating a vacuum barrier), a silver helmet (3) with a vacuum barrier between its inner metal and outer plastic layers, and pull-on boots (18) with four-centimeter-thick asbestos soles (17) and narrow treads (16) to retard heat transfer through contact with the Moon's surface.

If handling hot or cold tools or rocks became necessary, the lunar explorer could don mitts to protect his suit's permanently attached gloves. Knee pads could be added for kneeling or crawling.

Ross and Smith settled on a pure oxygen atmosphere at a pressure of 160 millimeters of mercury (for comparison, Earth's air mix is about 21% oxygen and 79% nitrogen at 760 mm of mercury). At the start of any moonwalk, the backpack would carry enough compressed gaseous oxygen to supply the lunar explorer for 12 hours.

The suit wearer would, of course, exhale carbon dioxide and water vapor, neither of which could be permitted to build up within the suit. Ross and Smith considered continuously venting "foul air" from the suit and replacing it with pure oxygen. (The Berkut suit Alexei Leonov wore during the world's first spacewalk on 18 March 1965 used this approach.) After rejecting continuous venting — it would, they calculated, require either a prohibitively large oxygen supply or very short moonwalks — they adopted a sodium peroxide-based system that would absorb exhaled carbon dioxide and water vapor and release supplemental oxygen as a by-product.

Ross and Smith proposed that, rather than exit and enter through an opening sealed by a zipper — which would tend to leak — the moonwalker should squeeze into the suit through its neck opening. The helmet would then lock into place, sealing the wearer inside. To prevent eye damage from exposure to harsh sunlight, they envisioned a helmet with only a narrow slit for viewing (28) and a bill and a pull-down visor (1). The suit would employ "internal body-hardness" to stop air pressure within it from pushing the helmet upward; this would keep the slit at the suit-wearer's eye level. Shoulder pads (7) would prevent Moon suit rigid components from chafing. How one might squeeze into the suit through a rigid neck and shoulder structure was not explained.

A collapsible chest-mounted airlock (24) and arm holes large enough to permit the lunar explorer to extract his arms from the suit arms (9) would enable him to pass objects in and out of the suit. These might include Moon rocks needing close examination and food and drink. An electric lamp (25) for lighting the way at night and in stark daytime shadow would be mounted on the chest above the round airlock hatch. Internal (14) and external (not shown) pockets would hold adhesive patches the wearer could apply if the suit became punctured by a micrometeoroid or torn by a tumble on sharp rocks.

Ross and Smith chose not to apply their considerable creativity to providing their Moon suit with means for accommodating two important bodily functions: specifically, urination and defecation. They wrote that their suit might be worn continuously for days during "camping trips" away from the Lunar Spaceship, so this omission is difficult to explain.

During camping trips, a suited explorer would not sleep on the ground or in direct sunlight; instead, to help maintain a comfortable temperature inside the suit, he would rest on a simple "camp-bed" in an unpressurized tent made of silver fabric. Similarly, he would not rest during long hikes by sitting on hot or cold boulders. The suit wearer would instead carry a walking stick, the handle of which could unfold to turn it into a one-legged stool (see image at top of post). The handle might be electrically heated for night use.

A radio antenna (4) atop the suit's backpack would permit both private communication between individuals and "party" communication among members of a group up to the distance of the lunar horizon (about 1.5 miles away on a level lunar plain, Ross and Smith estimated). The suit wearer could communicate directly with an antenna on the 50-foot-tall Lunar Spaceship at a distance of up to six miles on a level plain. If communication beyond the horizon or in an area with many surface obstructions — for example, hillocks and large boulders — became necessary, the moonwalker could leave behind small radio repeater stations as he moved over the surface.

The moonwalker would wear a "telephone head-set" (5) and a "laryngaphone" (throat microphone) (27). The radio, located at the top of the backpack directly beneath the antenna, would be controlled using knobs on the lower part of the backpack (11).

Ross and Smith ended their paper by estimating their Moon suit's weight. It would, they calculated, have an Earth weight of about 150 pounds. On the Moon, however, where gravity pulls with less than 20% as much force as on Earth, the suit would weigh about 25 pounds.

In July 2019, in time for the 50th anniversary of the Apollo 11 lunar landing (and the 70th anniversary of the Ross and Smith Moon suit presentation), the British National Space Center unveiled a life-size replica of the Ross and Smith Moon suit built in collaboration with the BIS and historical costume-maker Stephen Wisdom. For more information on the replica, visit the BIS website by following the link below.

Images in this post are Copyright © The British Interplanetary Society (https://bis-space.com) and are used by kind permission.

Sources

"Lunar Spacesuit," H. E. Ross and R. A. Smith, Journal of the British Interplanetary Society, Vol. 9, No. 1, January 1950, pp. 23-37; paper presented at the BIS Symposium of Medical Problems Associated with Space-Flight in London, United Kingdom, 19 November 1949.

High Road to the Moon: From Imagination to Reality, "The Collected Paintings of R. A. Smith with Text by Bob Parkinson," The British Interplanetary Society, 1979, pp. 22-24.

More Information

High Noon on the Moon (1991)

The Spacewalks That Never Were: Gemini Extravehicular Planning Group (1965)

Chrysler's Transportation and Work Station Capsule (1965)

"Without Hiatus": The Apollo Applications Program in June 1966

Raw material for a post-Apollo space program. Image credit: NASA.

Elsewhere in this blog, I have described how Apollo began in 1959 as a mainly Earth-orbital program (see "More Information" at the bottom of this post). As originally conceived, Apollo included a Mission Module that could serve as a small laboratory in Earth orbit. NASA anticipated that Apollo spacecraft would ferry astronauts, experiments, and supplies to a temporary Earth-orbital laboratory before the end of the 1960s decade; an Apollo spacecraft might also fly around the Moon without stopping in lunar orbit (that is, perform a circumlunar flight). After 1970, a new program would build on experience gained through Apollo, leading to either a permanent Space Station or a piloted lunar landing and voyages to the planets.

President John F. Kennedy's call for a man on the Moon by 1970 (25 May 1961) made Apollo the U.S. lunar landing program. Aware that Kennedy was not enthusiastic about space for its own sake, NASA Administrator James Webb was careful not to assume a national commitment to spaceflight beyond the Apollo lunar program.

Even as NASA came to terms with the Moon goal, however, it sought to keep alive the Space Station option. In April 1963, for example, the space agency tasked Apollo Command and Service Module (CSM) contractor North American Aviation with a study of how the CSM might serve as a Space Station crew rotation and logistics resupply vehicle. Some believed that, if Apollo accomplished a piloted Moon landing in 1967, then NASA might shift to the Space Station track in 1968.

In early 1964, new President Lyndon Baines Johnson called on NASA to declare its plans for U.S. piloted spaceflight after Apollo reached the Moon. In response, Webb formed the internal ad hoc Future Programs Task Group.

In January 1965, the Task Group submitted a report that favored a post-Apollo program built upon a technological foundation of Apollo CSM and Lunar Module (LM) spacecraft and Saturn IB and Saturn V rockets. The Task Group had drawn upon the expertise of Bellcomm, NASA's Apollo planning contractor, which that same month submitted a plan for 55 Saturn-launched Apollo test missions, Apollo lunar missions, post-Apollo lunar and Earth-orbital missions, and Voyager robotic Mars/Venus missions.

Image credit: NASA.

Image credit: NASA.

Image credit: NASA.

The Johnson White House accepted NASA's Apollo-based post-Apollo concept; the NASA Headquarters Office of Manned Space Flight (OMSF) then established the Saturn-Apollo Applications (SAA) Program Office in August 1965. A month later, SAA named the post-Apollo program the Apollo Applications Program (AAP).

Congress did not warm to AAP despite its promise to explore space for the benefit of people on Earth. The forces that would truncate the Apollo Program — for example, the human and fiscal cost of war in Indochina — were building. Though President Johnson went to bat for AAP in Fiscal Year (FY) 1966, he concurred when Congress requested a postponement in major funding for the program. Congressional leaders promised that, if possible, the funding delay would be made up in FY 1967 and subsequent years.

In June 1966, the SAA Program Office described in a memorandum dispatched to officials at the Manned Spacecraft Center (MSC), Marshall Space Flight Center (MSFC), and Kennedy Space Center (KSC) an AAP which, it said, would "continue without hiatus an active and productive post Apollo Program of manned space flight and. . .exploit for useful purposes. . .the capabilities of the Saturn Apollo System." The memorandum — a snapshot of a program undergoing rapid, chaotic change in response to funding challenges — explained that the plan it outlined was based on proposals NASA had submitted to President Johnson's Bureau of the Budget a month earlier.

AAP objectives fell into two basic areas. The first, Long-Duration Flights, would "measure the effects on men and on manned systems of space flights of increasing duration" and permit NASA to "acquire operational experience with increasingly longer manned space flights" so that it could "establish the basic capabilities required for any of the projected next generation of manned space flight goals (earth orbital space station, lunar station, or manned planetary exploration)."

The second emphasis area, Spaceflight Experiments, would emphasize space life sciences, astronomy, space physics, advanced lunar exploration, and space technology applications and development. AAP lunar exploration would support objectives proposed at the July 1965 meeting of space scientists in Falmouth, Massachusetts. The Falmouth meeting was one of a series of important lunar science planning meetings that began with the interdisciplinary Iowa City meeting in 1962.

At the time the SAA Program Office circulated its memo, the first Apollo lunar landing attempt was expected in late 1967 or early 1968. NASA, the memo explained, had ordered from its contractors 21 CSMs, 15 LMs, 12 Saturn IBs, and 15 Saturn Vs for delivery between 1966 and 1970. Most were intended for ground and flight tests.

The SAA Program Office assumed that four Saturn IBs (designated AS-209 through AS-212), six Saturn Vs (AS-510 through AS-515), and their associated CSM and LM spacecraft would remain unused after the first successful piloted Moon landing, and that these would immediately become available for AAP missions. Basic Apollo CSM and LM spacecraft would be modified to achieve new goals by the installation of "overlay kits."

Building upon these assumptions, the June 1966 memo described two possible AAP Program schedules. The Case I schedule assumed that no Saturn-Apollo hardware beyond that ordered for the Moon program would become available before late 1968 and that only enough AAP missions would be flown to accomplish minimal AAP goals. Case I missions would not necessarily serve as a bridge for linking Apollo lunar missions with a new piloted program in the mid-to-late 1970s. Even with these limitations, the SAA Program Office envisioned that Case I would see 21 Saturn IB and 16 Saturn V launches in the AAP by the end of 1973.

The more ambitious Case II schedule would see "an early extensive utilization of Saturn Apollo capabilities, with an earlier focus on a post-Apollo national space objective (such as a prototype of a space station or a planetary mission module)." Case II would see 26 Saturn IB and 17 Saturn V rockets launched from KSC before the end of 1975.

Both the Case I and Case II schedules would begin in 1968 with missions AS-209, AS-210, AS-211, and AS-212. AS-209 and AS-210, concurrent 14-day Earth-orbital life sciences/crew training missions launched on Saturn IB rockets, would kick off AAP. Their CSMs would dock for crew transfer and an orbital rescue test.

AAP spent-stage Workshop comprising (left to right) a Saturn IB rocket S-IVB stage, a drum-shaped Spent Stage Experiment Support Module (SSESM), and a docked Apollo Command and Service Module (CSM) spacecraft. Image credit: NASA.

The third 1968 AAP mission, AS-211, would see the launch of the first AAP spent-stage Workshop. The crew would detach their CSM from the Saturn IB S-IVB second stage that propelled it into Earth orbit, then would turn and dock with a Spent Stage Experiment Support Module (SSESM) mounted on the front of the stage.

In addition to docking ports, the SSESM would include solar panels for making electricity, an airlock for spacewalks, experiment equipment, and tanks of gaseous oxygen for purging and filling the S-IVB's 20-foot-diameter hydrogen tank so that it could serve as a habitable volume. The astronauts would conduct biomedical and astronomy/space physics experiments on board the CSM and inside the SSESM and hydrogen tank for from 28 to 56 days.

AAP missions in 1968/1969 would re-fly experiment apparatus first flown on short-duration (no more than 2 weeks) Earth-orbital Apollo Moon program test flights in 1966/1967. These would, the memorandum stated, include experiments in particles and fields, ion wake physics, X-ray astronomy, and UV spectroscopy. At the time the SAA Program Office wrote its memorandum, the first of these test flights, dubbed AS-204, was scheduled for liftoff in late 1966 with Mercury/Gemini veteran Gus Grissom, Gemini veteran and first U.S. spacewalker Ed White, and rookie astronaut Roger Chaffee on board.

Three Pegasus satellites were launched to gather data on the the meteoroid environment of low-Earth orbit. Pegasus 3, with a wingspan of 29 meters, included meteoroid-capture panels designed for retrieval by Gemini or Apollo astronauts; it would, however, not receive visitors before it reentered the atmosphere in August 1969. Image credit: NASA. 

The final 1968 AAP mission, AS-212, would see a CSM deliver supplies to the AS-211 spent-stage Workshop. It would then rendezvous with Pegasus 3, a 1.45-metric-ton satellite that was launched atop a Saturn I rocket on 30 July 1965. The AS-212 crew would spacewalk to retrieve meteoroid-capture and thermal coating test panels mounted on the satellite.

The Case I AAP schedule had the disadvantage of not permitting continuous rocket and spacecraft production and launch operations between AS-212 and the missions that would follow it. This, the memorandum explained, meant that Saturn-Apollo production and operations would be required to "phase down" during 1969-1970 and build up again in 1971. Case I missions after AS-212 would occur from three to nine months later than in Case II. The SAA Program Office favored and thus provided more details for the Case II schedule than for Case I. For this reason, from here on this post focuses exclusively on Case II.

The first of four 1969 AAP missions, AS-213, would be a near-duplicate of the AS-211 Workshop mission. On the second 1969 mission, AS-214, a CSM and the first LM-derived Apollo Telescope Mount (ATM) would carry out a 14-day solar astronomy mission. The ATM would reach orbit within the Spacecraft LM Adapter (SLA), the tapered shroud that linked the CSM with the top of the S-IVB rocket stage. AAP flights in 1968-1970 would occur during solar maximum, when activity on the Sun would peak, so in general their astronomy programs would emphasize solar observations. The AS-214 CSM would then undock from the ATM and dock with the AS-213 spent-stage Workshop to provide resupply and crew rotation.

In the June 1966 memorandum, the SAA Program Office assumed that LM-derived ATMs, labs, and carriers would launch with and operate while docked with piloted CSMs. As 1966 progressed, however, AAP planning increasingly emphasized ATM, lab, and carrier dockings with spent-stage Workshops. Such dockings would enable NASA to build up capable interim space stations and gain experience with in-space assembly of multi-modular spacecraft.

AS-214 would include the first Apollo Telescope Mount (ATM). Two astronauts would operate the ATM from the LM Ascent Stage; astronomical instruments would fill the stripped-out LM Descent Stage. Image credit: NASA.

The proposed AAP Laser Communications lab was not specifically mentioned as a payload in the June 1966 AAP program plan, though its design was typical of proposed LM-derived AAP labs. Image credit: Perkin Elmer.

The proposed AAP Optics Lab as it would appear stowed for launch in the SLA. Note that experiment equipment (mainly telescopes) and a square "platform" with attachment points at its corners for linking to the SLA completely replace the Descent Stage. Image credit: NASA.

The third 1969 mission, AS-215, was envisioned as a meteorology-oriented mission dubbed "Applications-A." It would probably have operated in an orbit steeply inclined relative to Earth's equator and employed an experiment/sensor carrier based on the LM design.

The AS-510 mission, the final 1969 AAP mission and the first AAP mission to launch on a Saturn V rocket, would place a CSM into geosynchronous Earth orbit (GEO) for communications, biomedicine, and Earth observation experiments. The rocket's S-IVB third stage, modified to permit two restarts, would ignite in low-Earth orbit to boost the CSM into an elliptical transfer orbit, then would fire again 5.5 hours later to circularize the CSM's orbit at the GEO altitude of 35,870 kilometers.

Five AAP Saturn IB missions would fly in 1970. These would include a 135-day stay on board a spent-stage Workshop in Earth orbit, two resupply visits to the spent-stage Workshop as part of other AAP missions, two solar ATM flights, a Biomed Lab mission, a fluids lab for studying weightless propellant behavior, the Applications-B Earth observation mission, and the introduction of an "Extended Capability CSM" for independent 45-day flights. Extended Capability CSM modifications would include long-life, high-capacity fuel cells for making electricity and water, an oxygen-nitrogen breathing mixture to replace Apollo's pure oxygen atmosphere (this was a concession to aerospace physicians, who worried about the health effects of breathing pure oxygen for long periods), and a long-life C-1 rocket engine in place of the Apollo CSM's Service Propulsion System main engine.

The Biomed Lab would be based on the Apollo LM or a "refurbished Command Module." The latter was envisioned as a used Command Module (CM) stripped of its heat shield, parachutes, and other systems, fitted out as a small pressurized laboratory, and launched a second time on a Saturn IB with a piloted CSM.

Four AAP Saturn V missions would fly in 1970, of which three would voyage to the Moon. These would be the first lunar missions since Apollo's end. The AS-511 Saturn V would launch a piloted mapping mission to lunar polar orbit. It would orbit for up to two weeks while the Moon rotated beneath it. This would enable the CSM to pass over nearly the entire lunar surface (and fly over half the surface in daylight).

The refurbished Command Module (CM) Lab came in dependent (upper left) and independent (lower right) forms. The "cruciform" was included in the design to provide attachment points linking the dependent CM Lab to the SLA. Image credit: North American Aviation.

Apollo CM pressure vessel. Image credit: NASA.

The AS-512 CSM would transport to lunar orbit an LM Shelter containing living quarters, supplies, and exploration gear (a small rover, a core drill, and an advanced sensor package). Once in orbit about the Moon, the LM Shelter would undock from the CSM and land automatically, then the piloted CSM would return to Earth. Less than three months later, the AS-513 Saturn V would launch an Extended Capability CSM and an LM Taxi to the Moon. The latter would land near the LM Shelter with two astronauts on board, including the first scientist-astronaut to reach the Moon. They would explore their landing site for 14 days.

The year 1970 would end with the AS-514 launch, which would place the first modified ("Mod") S-IVB Workshop into Earth orbit. The Mod S-IVB Workshop was a step up from the spent-stage Workshop; it would launch with no propellants in its tanks and its hydrogen tank outfitted with living quarters, supplies, and experiment gear. The four Saturn IB-launched AAP missions in 1971 would, the memorandum explained, support a one-year stay by a single crew on board the AS-514 Mod S-IVB Workshop.

In 1971, the AS-515 Saturn V would launch an Extended Capability CSM and an ATM on a 45-day mission to GEO to conduct stellar and solar astronomy, relativity, and space physics experiments. AS-516 (the first Saturn V built specifically for AAP) and AS-517 would launch an advanced lunar exploration mission similar to the AS-512/AS-513 pair, and AS-518 would launch a second Mod S-IVB Workshop.

The four Saturn IBs launched in 1972 (AS-225 through AS-228) would support stays on the second Mod S-IVB station. One of these missions would also test Command Module modifications meant to replace Apollo ocean splashdowns with cheaper land landings. Modifications would include steerable parachutes.

AS-512 in 1970 would deliver the LM Shelter to the lunar surface; AS-513 would see two astronauts arrive separately in an LM Taxi and live in the LM Shelter for 14 days. The LM Shelter would include a rover (shown stowed and in release position) and a core drill (shown deployed). This image dates from January 1965 but is applicable to the June 1966 AAP plan. Image credit: NASA.

Apollo CM with deployed parawing. Image credit: North American Aviation.

From 1972 through 1975, the memorandum explained, AAP missions would support a transition to an unspecified post-AAP piloted "follow-on program." NASA would increase its Saturn IB launch rate to six per year by 1973, and would continue to launch Saturn V rockets at a rate of four per year. The latter would launch four missions to GEO to conduct stellar astronomy, physics, and technology applications experiments (1972-1973), the automated Voyager Mars probes (1973), and a lunar mission similar to the AS-512/AS-513 pair each year through 1975. Two of the GEO missions would include ATMs. AS-520/AS-521 would launch the 1972 lunar mission pair and AS-525/AS-526 the 1973 pair.

The SAA Program Office envisioned that ATM missions might lead in late 1973 to an AAP astronomy mission featuring a reflecting telescope with a mirror measuring from 60 to 100 inches across. This, the memorandum explained, might serve to verify the mirror design ahead of its use in planned orbiting National Astronomical Observatories, sophisticated space telescopes expected to reach Earth orbit in the late 1970s.

As mentioned above, NASA began AAP amid increasing fiscal pressures. After pushing off a formal start to AAP as requested by Congress in FY 1966, President Johnson submitted a $5.01 billion NASA budget for FY 1967, of which $270 million was meant to fund AAP. Congress slashed the FY 1967 AAP budget to $83 million.

Observers of the U.S. space program were surprised when President Johnson went to bat for AAP again the following year. He requested that NASA's FY 1968 budget total $5.1 billion, with $455 million allotted to AAP. On 27 January 1967, the day after NASA OMSF director George Mueller briefed the press corps on the planned rapid ramp-up in AAP development, fire broke out inside the AS-204 Apollo CSM crew cabin during a test on the launch pad. Fed by the CSM's pure oxygen atmosphere, it immediately became an inferno. A poorly designed hatch trapped astronauts Grissom, White, and Chaffee inside, so they perished.

After the fire, NASA came under close scrutiny and was found wanting. Congress could not "punish" the agency by cutting the Apollo Program budget — to do so would have endangered achievement of President Kennedy's goal of a man on the Moon by 1970 — but it could express its displeasure by cutting programs meant to give NASA a post-Apollo future. The agency's FY 1968 appropriation was slashed to $4.59 billion, with AAP receiving only $122 million.

Under President Richard Nixon, NASA's budget slide accelerated. The Saturn rocket production lines were placed on standby in January 1970. At the same time, AAP became the Skylab Program. NASA Administrator Thomas Paine, who saw Skylab as a step toward a late 1970s 50-to-100-man Earth-orbiting Space Base, cancelled the Apollo 20 Moon mission so that its Saturn V (AS-513) could launch Skylab, a Saturn IB S-IVB-derived Orbital Workshop (OWS) resembling the AAP Mod S-IVB Workshop. Two years later, in January 1972, Nixon called for new-start funding for the Space Shuttle, which became NASA's main post-Apollo piloted program.

Work toward using Saturn-Apollo hardware in post-Apollo missions continued, though on a much-reduced scale. Apollo 17 (December 1972) saw the sixth and last piloted Moon landing of the 20th century and the last flight of the LM. NASA designated its Saturn V SA-512. On 14 May 1973, SA-513, the last Saturn V to fly, launched Skylab. An ATM for solar studies — the design of which was not based on the LM — reached orbit permanently attached to the OWS, and the Multiple Docking Adapter (MDA) replaced the SSESM. Three Saturn IBs (SA-206 through SA-208) launched three-man crews to Skylab in Apollo CSMs. The final Skylab crew splashed down on 8 February 1974, after 84 days in space.

The SA-210 Saturn IB, the last Saturn rocket to fly, launched the last Apollo CSM to fly. Its July 1975 mission to dock with a Soviet Soyuz spacecraft in low-Earth orbit brought the Apollo era to a close.

Source

"Saturn/Apollo Applications Program Summary Description," memorandum with attachments, MLD/Deputy Director (Steven S. Levenson for John H. Disher), Saturn/Apollo Applications, NASA Headquarters, to George M. Low, Manned Spacecraft Center, Leland F. Belew, Marshall Space Flight Center, and Robert C. Hock, John F. Kennedy Space Center, 13 June 1966.

More Information

A Forgotten Rocket: The Saturn IB

Space Station Resupply: The 1963 Plan to Turn the Apollo Spacecraft Into a Space Freighter

Apollo Extension System Flight Mission Assignment Plan (1965)

"Assuming That Everything Goes Perfectly Well in the Apollo Program. . ." (1967)

The First Voyager (1967)

"Still Under Active Consideration": Five Proposed Earth-Orbital Apollo Missions for the 1970s (1971)

Flying Brickyard Postponed: A 1972-1973 Study of an Interim Ablative Space Shuttle Heat Shield

Space Shuttle Orbiter during atmosphere reentry as conceived by North American Rockwell (NAR) in July 1972. The following month, NASA would make NAR the Space Shuttle prime contractor. Image credit: NASA.

Launch, ascent to orbit, and Earth atmosphere reentry are the most risk-fraught phases of most piloted space missions to date. They are also the mission phases that most tax the ingenuity of engineers who design reusable spacecraft.

Aerodynamic heating creates challenges during reentry and, to a lesser degree, during ascent to orbit. Before the Space Shuttle, almost all piloted spacecraft designed to operate for some portion of their mission in an atmosphere withstood such heating by employing single-use ablative heat shields. (The only exception was the X-15A-2 rocket plane, which, for part of its career, included a replaceable ablative heat shield — please see "More Information" at the end of this post.) During reentry, ablative heat shields char and break away, carrying away heat.

The Space Shuttle, approved for development by President Richard Nixon on 5 January 1972, marked a dramatic departure in heat shield technology. Originally conceived as a fully reusable, economical Space Station resupply and crew rotation vehicle, Nixon's partially reusable Shuttle had as its only approved goal a dramatic reduction in the cost of launching things into space. A reusable heat shield was believed to be essential for achieving that objective.

Over the decades, engineers have considered many reusable heat shield concepts, typically in combination. High on the list was a layer of overlapping "shingles" made of exotic metal alloys. Other approaches included liquid or solid heat sinks, thick metal or composite adjoining plates, or even an "active" system with cooling fluid circulating through a network of tubes behind a metal-alloy hull.

Unfortunately, all of these concepts would be heavy. To compensate for a heavy heat shield, engineers could design a more powerful booster system or could cut back on payload capacity (or both). Both approaches would boost development and operations costs. The Nixon White House had made clear that the Shuttle development budget of $5.15 billion was carved in stone, leaving NASA with little choice but to find new approaches — including some that accepted a significant increase in eventual operations cost.

Partial cutaway of the NAR ("NR") Shuttle Orbiter showing optional jet engine module installed in the aft portion of the Payload Bay, main engines, fore and aft reaction control system thruster clusters, aluminum wing structure, twin robot arms, crew module, and ring-shaped, nose-mounted docking unit forward of the crew module. Image credit: NASA.

For the Shuttle Orbiter, NASA and contractor engineers chose a lightweight combination of fabrics and brittle silica ceramic tiles, which they dubbed Reusable Surface Insulation (RSI). The tiles could withstand temperatures of up to 2300° Fahrenheit. Reinforced Carbon-Carbon composite panels would protect the Orbiter's wing leading edges, nose, and other areas subject to the highest reentry temperatures (as high as 3000° Fahrenheit).

Though RSI was meant to block almost all heat, enough would get through that, combined with aerodynamic buffeting, the Orbiter's mostly aluminum skin would tend to warp and flex ("flutter"). This meant that large ceramic panels affixed to the skin would crack, leaving it vulnerable to reentry heating.

Shuttle engineers sought to avoid damage by gluing RSI ceramics to a flexible fabric "strain isolator" layer glued to the Orbiter's skin and by making individual ceramic elements small in size. By resorting to many small "tiles" in place of a relatively few large panels, engineers designed an RSI heat shield that was in effect "pre-cracked."

The tiles, each milled to conform to its place on the Orbiter's complexly curvaceous hull, would number in the tens of thousands. By late in the 1970s decade, when their number hovered around 31,000, the tiles earned the Orbiter the nickname "The Flying Brickyard."

Some engineers harbored doubts about RSI; enough that NASA Langley Research Center in Hampton, Virginia, paid the Denver Division of Martin Marietta Corporation (MMC) to examine an alternative. Between May 1972 and August 1973, MMC engineers sought to determine whether Space Shuttle Orbiters could employ an ablative heat shield.

The ablative shield was seen as a stand-in system meant to provide NASA with more time for RSI development should problems arise. In his October 1975 report on the ablative heat shield study, Rolf Seiferth, who managed the MMC study between 5 September 1972 and its conclusion on 31 August 1973, envisioned that the ablative shield might fill in for RSI for five years. Based on a November 1972 NASA-generated Space Shuttle traffic model, this meant that 151 flights between 1979 and the end of 1983 would rely on the stand-in ablative system.

Seiferth noted that, in past programs, ablative heat shield materials had been glued directly to the spacecraft hull. This was, he explained, a cost-saving, weight-saving approach; scraping away a used directly applied ablative shield would, however, add time to Orbiter refurbishment between flights and generate considerable debris, including invasive dust.

In addition to the directly applied heat shield, MMC examined three types of "mechanically attached" ablative panels. These had ablative material glued to panels made of aluminum, magnesium, graphite composite, or beryllium/aluminum "Lockalloy" sheet or honeycomb.

The panels would be joined to oversized holes in the Orbiter's skin using nut-and-bolt fasteners, enabling entire panels to be replaced as necessary. The oversized holes would allow for thermal expansion of the heat shield components.

The simplest mechanically attached ablative panel would see ablative material glued to a metal or composite sheet. Adhesive and sheet would together measure only about 0.06 inches thick. Attachment points for the sheet panel design would typically occur five inches apart over much of the Orbiter, though larger spacings (up to 20 inches) were also possible.

The two more complex mechanically attached ablative panels substituted metal or composite "honeycomb" for the metal or composite sheet. One had ablative material glued to the honeycomb, which was then bolted to oversized holes in the Orbiter's skin.

The other — to which MMC gave considerably less attention — added rib-like standoffs to the Orbiter's skin. The honeycomb was then mechanically attached to oversized holes in the standoffs, leaving a gap between the underside of the honeycomb and the Orbiter skin.

Honeycomb panel attachment points would typically occur 10 inches apart over much of the Orbiter. Larger (up to 20 inches) and smaller (down to five inches) spacings were possible.

Seiferth's team used computer models to determine required ablator thickness, which would vary depending on its location on the Orbiter. All models assumed a maximum reentry deceleration equal to 2.5 times Earth's surface gravity (that is, 2.5 G) and a maximum allowable Orbiter aluminum skin temperature of 350° Fahrenheit, variables which indicated a relatively benign reentry environment (as compared to an Apollo lunar-return reentry, for example).

MMC used for its calculations properties of several types of ablative material it had developed for other missile and space projects (notably, the Titan missile family and the Viking Mars lander). It found that, for most locations on the Orbiter, its least robust ablator would be sufficient.

The ablative layer for most locations could be surprisingly thin. For the simplest mechanically attached panel design, for example, the MMC computer models indicated that a point on the Orbiter's underside on the fuselage centerline 50 feet aft of its nose would need a layer of ablative material only 1.7 inches thick.

Assessing the cost of the ablative designs relative to RSI was difficult in part because Space Shuttle Program cost estimation was, for want of a better term, eccentric. Seiferth supplied no development or operations cost estimate for RSI in his report, though he did provide estimates for several of MMC's ablative designs.

A system with an ablator glued directly to the Orbiter's aluminum skin would, Seiferth estimated, cost a total of $164.8 million for 151 flights over five years. Of this, installation and removal would account for $27.9 million.

A mechanically attached system comprising an aluminum sheet, adhesive, and an ablator (that is, the simplest mechanically attached ablative system) with attachment points five inches apart would cost $168.3 million with an installation and removal cost of $21.9 million. The aluminum honeycomb system with no standoffs and attachment points five inches apart came in at $187.1 million with $25.7 million for installation and removal.

NASA provided MMC with an RSI weight estimate of 30,240 pounds, enabling an RSI/ablative system weight comparison. The MMC study determined that an ablator directly attached to the Orbiter's skin would weigh 27,199 pounds, while the sheet and honeycomb (no standoffs) mechanically attached systems would weigh 32,577 pounds and 32,158 pounds, respectively.

Seiferth noted that modifications to the Orbiter's aluminum skin design would need to be put in place soon if mechanically attached ablative panels were used. Delaying until after the Orbiter's skin was in place would make prohibitive the cost and difficulty of adopting the ablative Space Shuttle heat shield. By the time Seiferth's report saw print in October 1975 — more than two years after the MMC study concluded — a stand-in ablative heat shield, never high on NASA's list of Space Shuttle priorities, was in fact no longer an option.

Late in the 1970s decade, problems with the Space Shuttle Main Engine, RSI, computers, and other systems contributed to delays in STS-1, the Space Shuttle's orbital maiden flight. RSI problems in particular became very public in March 1979, when the Space Shuttle Orbiter Columbia was flown from California to NASA Kennedy Space Center (KSC), Florida, atop its 747 carrier aircraft. It was the first Orbiter's first visit to its home base. At the time, Columbia was scheduled to carry out STS-1 in November 1979.

Columbia rolls into the Orbiter Processing Facility at Kennedy Space Center, Florida, on 25 March 1979. Though the image displays only the area around the front of the fuselage, many RSI gaps are evident. Image credit: NASA.

For the cross-country flight, about 26,000 permanent RSI tiles were installed on Columbia, along with about 5000 foam "dummy" tiles. By the time the Orbiter/747 combination set down on the Shuttle Landing Facility strip at KSC on 25 March 1979, Columbia had lost more than 200 RSI tiles. Many were lost as more than 4800 of the dummy tiles tore loose, a condition which would not occur during space flight.

Some permanent RSI tiles had, however, fallen off Columbia for other reasons. Close examination revealed tile manufacturing flaws, installation errors, and an overall unexpected degree of fragility. Even as Columbia entered the processing flow for STS-1, NASA conceded that the flight might be delayed until 1980.

Much was made of the "zipper effect," a hypothetical catastrophic failure mode that would begin with the loss of a single tile during reentry. The Orbiter was believed likely to survive loss of a single tile unless it occurred in an especially critical area. Loss of a single tile anywhere would, however, weaken surrounding tiles, potentially leading to a cascading loss of thermal protection. In fact, few tiles fell off Orbiters during the series of 135 Shuttle missions that began with Columbia's first launch on 12 April 1981.

The RSI system did, however, prove prone to impact damage during processing, launch, landing, and transport. The most extreme example before January 2003 occurred during STS-27 (2-6 December 1988), a classified Department of Defense mission. Eighty-five seconds after liftoff, debris broke free from the right Solid Rocket Booster, battering the right wing of Orbiter Atlantis. More than 700 RSI tiles were damaged and one was lost. Because the mission was classified, the near-disaster was not widely known for nearly 20 years.

This closeup of the right wing of the Orbiter Discovery was taken from the International Space Station (ISS) during STS-114 (26 July-9 August 2005), the first post-Columbia "Return-to-Flight" Mission. After the Columbia accident, NASA modified the External Tank design to eliminate the possibility of debris separation; nevertheless, two pieces of icy foam insulation broke free during STS-114, with one striking Discovery. In addition to a tile repair kit, which the STS-114 crew tested during a scheduled spacewalk, Discovery carried a Shuttle Remote Manipulator ("robot arm") extension that enabled its crew to inspect its RSI surfaces; it also performed a slow flip near the ISS so that astronauts on the station could inspect and photograph it. Though no damage was found, NASA prudently grounded the Shuttle fleet for another year after STS-114 returned to Earth so that it could continue its efforts to solve the External Tank debris problem. Image credit: NASA.

The Space Shuttle Orbiter Columbia lifted off on 16 January 2003 at the beginning of mission STS-107, its 28th flight and one of the few remaining non-ISS missions NASA had scheduled for the Shuttle fleet. During ascent, a piece of water ice-impregnated insulating foam weighing almost two pounds broke free from the External Tank to which Columbia was mounted. It struck the Reinforced Carbon-Carbon leading edge of the Orbiter's left wing, punching a hole at least 10 inches wide.

The debris strike was captured on video and immediately became the subject of urgent debate within the Shuttle Program. Knowledge of the strike was not shared widely. The viewing angle meant that the strike area was not visible in launch video recorded from the ground and its location meant that the STS-107 crew could not see it. Managers decided that Columbia's wing leading edge was probably intact.

The hole admitted hot gas as Columbia reentered on 1 February 2003. Its internal structure compromised, NASA's oldest Orbiter broke up over east Texas and western Louisiana, killing its seven-person crew and grounding the Space Shuttle fleet for 30 months.

The following January, President George W. Bush declared that the Space Shuttle would be retired after it performed its last International Space Station (ISS) assembly mission. The final Shuttle flight, STS-135 (8-21 July 2011), saw Atlantis, veteran of the STS-27 near miss, deliver supplies to ISS ahead of an anticipated gap in U.S. piloted space flights of indefinite duration.

Sources

"Space Shuttle Orbiter and Subsystems," D. Whitman, Rockwell International Corporation; paper presented at the 11th Space Congress in Cocoa Beach, Florida, 17-19 April 1974.

Ablative Heat Shield Design for Space Shuttle, NASA CR-2579, R. Seiferth, Denver Division, Martin Marietta Corporation, October 1975.

"Thermal Tile Production Ready to Roll," R. O'Lone, Aviation Week & Space Technology, 8 November 1976, pp. 51, 53-54.

"First Orbiter Ready for Florida Transfer," B. Smith, Aviation Week & Space Technology, 5 March 1979, pp. 22-23.

"Thermal Tile Application Accelerated," C. Covault, Aviation Week & Space Technology, 21 May 1979, pp. 59, 61-63.

"Space Shuttle Orbiter Status April 1980," S. Jones, NASA Johnson Space Center; paper presented at the 17th Space Congress in Cocoa Beach, Florida, 30 April-2 May 1980.

STS-27R OV-104 Orbiter TPS Damage Review Team, Volume I, Summary Report, NASA TM-100355, February 1989.

More Information

X-15: Lessons for Reusable Winged Spaceflight (1966)

Where to Launch and Land the Space Shuttle? (1971-1972)

What If a Space Shuttle Orbiter Had to Ditch? (1975)

What If a Space Shuttle Orbiter Struck a Bird? (1988)

Revival: A Piloted Mars Flyby in the 1990s (1985)

An Orbital Transfer Vehicle (OTV) carrying a drum-shaped Command Module aerobrakes in Earth's atmosphere in this NASA painting by Pat Rawlings. 

In the 1960s, NASA expended nearly as much study money and effort on piloted Mars and Venus flyby mission planning as it did on its more widely known plans for piloted Mars landings. Italian aviation and rocketry pioneer Gaetano Crocco had described a free-return piloted Mars/Venus flyby mission in 1956. Piloted flyby studies within NASA began with the EMPIRE study the Marshall Space Flight Center (MSFC) Future Projects Office initiated in 1962 and culminated in the NASA-wide Planetary Joint Action Group (JAG) piloted flyby study of 1966-1967.

The Planetary JAG, led by the NASA Headquarters Office of Manned Space Flight, brought together engineers from MSFC, Kennedy Space Center, the Manned Spacecraft Center (MSC), and Washington, DC-based planning contractor Bellcomm. It issued a Phase I report in October 1966 and continued Phase II study work in Fiscal Year (FY) 1967. The Phase I report emphasized a piloted Mars flyby mission in 1975, but included Mars and Venus flyby missions tailored to low-energy mission opportunities through 1981. All would be based on hardware developed for the Apollo Program and its planned successor, the Apollo Applications Program (AAP).

The piloted flyby spacecraft would carry automated probes, including one that would land on Mars, collect a sample of surface material and launch it back to the flyby spacecraft for immediate analysis. A leading point in favor of the piloted flyby mission was, in fact, the ability of the flyby crew to examine a Mars sample for signs of life less than an an hour after it left the martian surface.

Red planet off the port bow: a piloted flyby spacecraft based on Apollo spacecraft hardware releases probes as it passes Mars. Image credit: Douglas Aircraft Company.

According to Edward Clinton Ezell and Linda Neumann Ezell, writing in their 1984 NASA-published history On Mars: Exploration of the Red Planet, 1958-1978, NASA MSC was largely responsible for the demise of 1960s piloted flyby mission planning. On 3 August 1967, the Houston, Texas-based center, home of the astronaut corps and Mission Control, distributed to 28 aerospace companies a Request for Proposal (RFP) for a piloted Mars flyby spacecraft sample-returner design study. By doing this, MSC appeared to disregard warnings from Congress that no new NASA program starts would be tolerated.

In the summer of 1967, NASA was preoccupied with recovery from the 27 January 1967 Apollo 1 fire, which had killed astronauts Virgil Grissom, Roger Chaffee, and Ed White. Many in Congress felt that NASA had been lax in enforcing quality and safety standards at North American Aviation, the Apollo Command and Service Module spacecraft prime contractor, so deserved to be "punished" for the accident. Other members of Congress were angered by NASA's apparent failure to share its concerns regarding NAA's performance so they could exercise Congressional oversight. They did not, however, wish to cut Apollo funding and endanger accomplishment of Apollo's very public goal of a man on the Moon by 1970.

In addition, by August 1967, the Federal budget deficit for FY 1967 had reached $30 billion. Though negligible by modern standards, this was a shocking sum in 1967. The deficit was driven in large part by the cost of fighting in Indochina, which had reached more than $2 billion a month, or the entire Apollo Program budget of $25 billion every 10 months.

After learning of the MSC RFP, long-time House Space Committee Chair and NASA supporter Joseph Karth declared angrily that "a manned mission to Mars or Venus by 1975 or 1977 is now and always has been out of the question — and anyone who persists in this kind of misallocation of resources. . .is going to be stopped." On 16 August, the House cut all funding for advanced planning from NASA's FY 1968 budget bill and slashed the budget for AAP from $455 million to $122 million. Total cuts to President Lyndon Baines Johnson's January 1967 FY 1968 NASA budget request amounted to more than $500 million, or about 10% of NASA's FY 1967 budget total.

Though he opposed the cuts, President Johnson bowed to the inevitable and signed the budget into law. The Planetary JAG and Bellcomm tied up loose ends of the piloted flyby study during FY 1968, but most work on the concept ended within a few months of the Houston center's ill-timed RFP.

It is ironic, then, that NASA's next piloted Mars flyby study took place in Houston, at Johnson Space Center (JSC), as MSC had been re-christened following President Johnson's death in January 1973. Barney Roberts, an engineer in the JSC Engineering Directorate, reported on the study to the joint NASA-Los Alamos National Laboratory (LANL) Manned Mars Missions workshop in June 1985.

The workshop, held at NASA MSFC, was a significant step in the revival of piloted Mars exploration planning within NASA after the long drought of the 1970s. Unfortunately, in their plan for a piloted Mars flyby in the 1990s, NASA JSC engineers demonstrated little sign of awareness of the 1960s piloted flyby studies. As a result, their proposed mission was less credible than it might have been.

Roberts explained that the NASA JSC flyby plan aimed to counter a possible Soviet piloted Mars flyby. He cited a 1984 Central Intelligence Agency (CIA) memorandum that suggested (without citing much in the way of evidence) that the Soviet Union might attempt such a mission in the 1990s — possibly as early as the 75th anniversary of the Bolshevik Revolution in 1992 — in order to garner international prestige. The CIA study had been performed at the request of Apollo 17 moonwalker Harrison Schmitt, whose chief spaceflight interest in the early-to-mid 1980s was a piloted Mars mission.

NASA's piloted Mars flyby would be based on space hardware expected to be operational and readily available in the late 1990s. Space Shuttle Orbiters would deliver to NASA's Space Station an 18-ton Mission Module (MM) and a pair of expendable propellant tanks with an empty mass of 11.6 tons each. The MM, derived from a Space Station module, would carry a 3000-pound solar-flare radiation shelter, 7000 pounds of science equipment, and 2300 pounds of food and water.

Going for a ride: a piloted Mars flyby spacecraft prepares for launch from Earth orbit in the late 1990s. A = twin Orbital Transfer Vehicles (OTVs); B = twin strap-on propellant tanks; C = Command Module; D = Mission Module. Image credit: NASA/David S. F. Portree.

The MM would be docked to a six-ton Command Module (CM) and two 5.75-ton Orbital Transfer Vehicles (OTVs). The OTVs would each include an aerobrake heat shield and two rocket engines derived from the Space Shuttle Main Engine. The JSC engineers had assumed that the CM and OTVs would be in space already as part of a late 1990s NASA Lunar Base Program. The strap-on tanks would be joined to the MM/CM stack by trunnion pins similar to those used to anchor payloads in the Space Shuttle Orbiter payload bay, then Space Station astronauts would perform spacewalks to link propellant pipes and electrical and control cables.

Shuttle-derived heavy-lift rockets would then deliver a total of 221 tons of cryogenic liquid hydrogen and liquid oxygen propellants to the Space Station to fill the piloted flyby spacecraft's twin tanks. The propellants would be pumped aboard just prior to departure from Earth orbit to prevent liquid hydrogen loss through boil off. Mass of the piloted flyby spacecraft at the start of its Earth-departure maneuver would total 358 tons.

As the launch window for the Mars flyby opportunity opened, the piloted flyby spacecraft would move away from the Space Station using small thrusters on retractable arms, then the four OTV engines would ignite and burn for about one hour to put it on course for Mars. The only propulsive maneuver of the baseline mission, the burn would empty the OTV and strap-on propellant tanks. Roberts advised retaining the spent tanks to serve as shielding against meteoroids and radiation for the MM and CM during the year-long flight.

Roberts told the workshop that the flyby spacecraft would spend two-and-a-half hours within about 20,000 miles of Mars. Closest approach would bring it to within 160 miles of Mars. At closest approach, the spacecraft would be moving at about 5 miles per second.

The spacecraft would then begin its long return to Earth. Roberts provided few details of the interplanetary phases of his piloted Mars flyby mission.

As Earth grew from a bright star to a distant disk, the Mars flyby astronauts would discard the twin strap-on tanks. They would then undock one OTV by remote control and re-dock it to the front of the CM. After entering the CM and sealing the hatch leading to the MM, they would discard the MM and second OTV, then would then strap into their couches to prepare for aerobraking in Earth's upper atmosphere and capture into Earth orbit. After the OTV/CM combination completed the aerobraking maneuver, the crew would pilot it to a docking with the Space Station.

Almost home: the piloted Mars spacecraft prepares for the aerobraking maneuver in Earth's atmosphere at the end of its epic year-long interplanetary voyage. A = OTVs; C = Command Module bearing crew; D = discarded Mission Module (attached to discarded OTV). Image credit: NASA/David S. F. Portree.

Roberts told the NASA/LANL workshop that Earth return would be the most challenging phase of the piloted Mars flyby mission. The OTV/CM combination would encounter Earth's upper atmosphere at a speed of 55,000 feet (10.4 miles) per second, producing reentry heating well beyond the planned capacity of the OTV's heat shield. In addition, the crew would suffer "exorbitant" deceleration after living for a year in weightlessness.

Roberts proposed a "brute-force" solution to these problems: use the OTV's twin rocket motors to slow the OTV/CM to lunar-return speed of 35,000 feet (6.6 miles) per second. The braking burn would, however, increase the Mars flyby spacecraft's total required propellant load to nearly 500 tons. He calculated that, assuming that a Shuttle-derived heavy-lift rocket could be designed to deliver cargo to LEO at a cost of $500 per pound (an optimistic assumption, as it would turn out), then Earth-braking propellant would add $250 million to his mission's cost.

Roberts briefly considered partially compensating for the large mass of braking propellants by substituting an MM derived from a five-ton Space Station logistics module for the 18-ton MM. This would mean, however, that the crew would have to spend a year in cramped quarters with no exercise or science equipment.

Planners in the 1960s had wrestled with and prevailed over the same problems of propellant mass and Earth-return speed that NASA JSC engineers faced in their 1985 study. Bellcomm had, for example, proposed in June 1967 that the Planetary JAG's piloted Mars flyby mission conserve propellants through assembly of the flyby spacecraft in an elliptical orbit, not circular Space Station orbit. The elliptical assembly orbit would mean, in effect, that the flyby spacecraft would begin Earth-orbit departure even as it was being assembled.

In addition, returning the crew directly to Earth's surface in a small Apollo-type capsule with a beefed-up heat shield would greatly reduce the quantity of braking propellants required; it could eliminate the braking maneuver entirely. It would also enable an aerodynamic "skip" maneuver that would reduce deceleration stress on the astronauts.

TRW Space Technology Laboratory had proposed as early as 1964, during the EMPIRE follow-on studies, that NASA use a Venus flyby to slow spacecraft returning from Mars. Crocco had described the concept in 1956, in fact, though in a form that turned out to be unworkable because of errors he made when he calculated his flyby spacecraft's orbit about the Sun.

Exploiting a Venus flyby to reduce speed would, of course, limit Earth-Mars-Earth transfer opportunities to those that would intersect Venus on the return leg, but would also eliminate the costly end-of-mission braking burn and enable Venus exploration as a bonus. The Planetary JAG's October 1966 report described Mars-Venus and Venus-Mars-Venus flyby missions in the late 1970s. Bellcomm determined in late 1966 and 1967 that Mars/Venus flyby opportunities are not rare.

Sources

"Soviet Plans for a Manned Flight to Mars," C. Cravotta and M. DeForth, Office of Scientific and Weapons Research, Central Intelligence Agency, 2 April 1985.

"Concept for a Manned Mars Flyby," Barney B. Roberts, Manned Mars Missions: Working Group Papers, Volume 1, NASA M002, NASA/LANL, June 1986, pp. 203-218; proceedings of a workshop held at NASA Marshall Space Flight Center, Huntsville, Alabama, 10-14 June 1985.

On Mars: Exploration of the Red Planet, 1958-1978, NASA SP-4212, Edward Clinton Ezell & Linda Neuman Ezell, NASA History Office, 1984, pp. 117-118.

Humans to Mars: Fifty Years of Mission Planning, 1950-2000, Monographs in Aerospace History #21, NASA SP-2001-4521, David S. F. Portree, NASA History Division, February 2001, pp. 11-12, 15, 60-62.

More Information

After EMPIRE: Using Apollo Technology to Explore Mars and Venus (1965)

Relighting the FIRE: A 1966 Proposal for Piloted Interplanetary Mission Reentry Tests

Apollo Ends at Venus: A 1967 Proposal for Single-Launch Piloted Venus Flybys in 1972, 1973, and 1975

Triple Flyby: Venus-Mars-Venus Piloted Flyby Missions in the Late 1970s/Early 1980s (1967)

Astronaut Telescope Servicing at Earth-Sun L2 (1999)

Interplanetary space showing the positions of the Sun, Earth, Earth's orbit about the Sun, the Moon, the Moon's orbit about the Earth, and the five Earth-Sun Libration Points. Image credit: NASA.

The Earth-Moon and Sun-Earth Libration (L) points are not places in the sense that one can land on them and pick up rocks. Because of this, some space exploration planners perceive them to be unsatisfying destinations. The L points have, however, long been proposed as space transportation way stations and as radio relay and scientific instrument sites.

In 1999, the Decadal Planning Team (DPT), a secretive NASA-wide study group chartered by President William Clinton's Office of Management and Budget, identified astronomical observatories in "halo orbits" around the Sun-Earth L points as a key NASA goal for the early 21st century. These large and complex instruments would, among other tasks, seek to observe Earth-like worlds around other stars.

The NASA Exploration Team (NExT), the DPT's immediate successor, subsequently sought to incorporate the Sun-Earth L point emphasis into its piloted spaceflight planning. In a 20 December 1999 presentation to the NeXT, for example, NASA Johnson Space Center exploration planner Bret Drake examined ways that the Sun-Earth L points might aid future piloted Mars missions.

An automated solar observatory orbiting the Sun-Earth L1 point, 1.5 million kilometers from Earth, could provide Mars crews with early warning of solar flares, Drake explained. Radio relays in halo orbit about Sun-Earth L4, 60° ahead of the Earth along its Sun-centered orbit, and Sun-Earth L5, 60° behind the Earth along its orbit, could enable continuous radio communication between Earth and crews exploring Mars during superior conjunctions, when the Sun blocks line-of-sight radio contact between the two planets.

Drake hastened to add that the Sun-Earth L points would not be good staging places for piloted Mars missions. He explained that the trip to and from a Sun-Earth L point would add almost two months to the typical duration of a roundtrip Mars voyage that started from low-Earth orbit (LEO).

Piloted missions to Sun-Earth L points might, however, serve as experience-building intermediate steps between piloted LEO missions and piloted Mars missions. Drake suggested that L point missions could enable astronauts to experience interplanetary conditions (for example, solar radiation undiminished by Earth's magnetic field), yet would have one-way trip times as short as 25 days.

Drake proposed that NASA astronauts carry out a 100-day telescope-servicing mission to Sun-Earth L2, 1.5 million miles from Earth. The mission would employ Solar-Electric Propulsion (SEP) technologies and techniques first proposed in 1998 for NASA's Mars Design Reference Mission.

The mission would begin with the unmanned launch to LEO of a 32,975-kilogram telescope-servicing spacecraft comprising a 14,450-kilogram inflatable "mini-Transhab" crew module, a 4271-kilogram Apollo Command Module-shaped Earth Return Vehicle (ERV), and a 14,164-kilogram two-stage Chemical Propulsion Module. The spacecraft would reach LEO within the streamlined shroud of a next-generation expendable rocket called an Evolved Expendable Launch Vehicle-Heavy (EELV-H).

A Space Shuttle Orbiter would rendezvous with the telescope-servicing spacecraft in LEO so that astronauts could oversee inflation of the doughnut-shaped single-deck mini-Transhab and deployment of its twin electricity-generating solar arrays. They would install equipment and furnishings in the mini-Transhab and stock it with supplies, then would return to Earth.

A second EELV-H would place a 33,000-kilogram automated Solar-Electric Propulsion (SEP) Vehicle into LEO, where it would automatically deploy solar-array wings and dock with the telescope-servicing spacecraft. Over the next seven months, the SEP Vehicle would operate its electric-propulsion thrusters at perigee (the low point in its orbit about the Earth) to raise its apogee (the high point in its orbit).

The result of these SEP Boost Phase maneuvers would be a highly elliptical orbit loosely bound to the Earth. The SEP Vehicle would then detach from the telescope-servicing spacecraft and operate its thrusters at apogee to return to LEO for refurbishment and reuse.

Use of the SEP Vehicle to place the telescope-servicing spacecraft into a highly elliptical Earth orbit would dramatically reduce the quantity of chemical propellants required to leave LEO for Earth-Sun L2. SEP thrusters produce little thrust but can do so over long periods and expend little propellant. This approach would greatly reduce overall mission mass and the number of EELV-H and Shuttle Orbiter flights required to place the telescope-servicing spacecraft into LEO.

The telescope-servicing spacecraft would carry no crew during the SEP Boost Phase because it would pass through Earth's radiation belts repeatedly. Over time, this would subject the crew to an unacceptably high cumulative radiation dose.

Drake inserted into his telescope-servicing mission assembly-and-launch sequence an optional piloted mission that would fly only if the telescope-servicing spacecraft needed repairs following the SEP Boost Phase. A Shuttle Orbiter would deliver to LEO a maintenance crew, a small lifting-body Crew Taxi, and a chemical-propulsion rocket stage. The stage would rapidly boost the Taxi into a highly elliptical Earth orbit matching that of the telescope-servicing spacecraft.

The maintenance crew would rendezvous and dock with the telescope-servicing spacecraft. After completing the needed repairs, they would undock, fire the Crew Taxi's rocket motors at apogee to lower its perigee into Earth's atmosphere, perform reentry, and glide to a landing.

If, however, flight controllers on Earth determined that the telescope-servicing spacecraft in highly elliptical Earth orbit was healthy and that no repairs were needed, the Crew Taxi would deliver a four-person crew to the telescope-servicing spacecraft. After casting off the Taxi, they would ignite the telescope-servicing spacecraft's first chemical-propulsion stage at perigee to escape their loosely bound highly elliptical orbit and begin the 25-day voyage to Sun-Earth L2. They would then cast off the spent stage.

In the Sun-Earth L2 Operations Phase, the telescope-servicing spacecraft would enter a "halo parking orbit" centered on Sun-Earth L2. For 50 days the astronauts would service large next-generation telescopes in halo orbits around Sun-Earth L2, much as Space Shuttle crews in 1993, 1997, 1999, 2002, and 2009 serviced the Hubble Space Telescope in LEO. Drake suggested that during their down time between servicing calls they might conduct unspecified scientific research.

Their mission completed, the astronauts would ignite the second stage of the telescope-servicing spacecraft's Chemical Propulsion Module to begin return to Earth. About 25 days later, they would strap into the ERV capsule, undock from their home of the previous 100 days, reenter Earth's atmosphere, and parachute to a landing. The other components of the telescope-servicing spacecraft would burn up in Earth's atmosphere.

Even as Drake presented his Earth-Sun L2 servicing mission concept, NASA engineers conceived of a Gateway space station in halo orbit about Earth-Moon L1 as a base for observatory servicing and as a stepping stone to points all over the lunar surface. They envisioned that observatories needing servicing would ignite small thrusters to begin a slow transfer from their Earth-Sun L1 and L2 halo orbits to the vicinity of the Gateway. Once at Earth-Moon L1, they would be serviced by spacewalking astronauts, "cherry picker" booms, and teleoperated systems.

Flying formation with teleoperated systems, an advanced space telescope arrives in the vicinity of the Earth-Moon L1 Gateway. The twin red spheres carry imagers that supply information on the telescope to astronauts inside the Gateway. As they escort the telescope, a boxy teleoperated robot with several jointed appendages moves into the shadow cast by its multi-layer sunshield. Partially silhouetted against the Moon, the Gateway includes six solar arrays, a doughnut-shaped pressurized mini-Transhab habitat module, multiple docking ports, servicing equipment, and three rocket stages for unspecified missions. Please click on the image to enlarge. Image credit: NASA.

Cislunar space showing the positions of Earth, the Moon, the Moon's orbit about Earth, and the five Earth-Moon Libration Points. Image credit: NASA.

In January 2004, in the aftermath of the STS-107 Columbia Space Shuttle accident (1 February 2003) and at the start of the 2004 election cycle, President George W. Bush called for a new NASA program to take humans to the Moon and Mars. At first, the Vision for Space Exploration (VSE), as it became known, incorporated many elements of DPT/NExT.

Soon after Michael Griffin became NASA Administrator on 13 April 2005, however, the VSE veered away from DPT/NExT and toward the Constellation Program, which Griffin called "Apollo on steroids." Bush showed little interest in the VSE after he announced it, so did not intervene to keep his program on track.

Constellation and the VSE were mostly abandoned in 2009-2010 under President Barack Obama. The global economy was in crisis following the collapse of the U.S. housing market in 2008 and the near-collapse of the global financial system. Spaceflight, rarely a high priority, took a distant back seat to repairing the U.S. economy.

When Obama unveiled a new space plan in 2010, it resembled DPT/NExT more than Constellation. The Bush Administration's decision to cancel the Space Shuttle led to the most significant deviation from the DPT/NExT architecture: retention of Constellation's large rocket under the name Space Launch System. Resembling an oversized EELV-H, SLS replaced the Shuttle Orbiter and the solar-electric tug of the DPT/NExT plan. The Orion Crew Exploration Vehicle (CEV) replaced the lifting-body taxi.

Meanwhile, China launched a program to explore the Moon using robots. Chang'e 1 orbited the Moon in 2007-2009; Chang'e 2 orbited the Moon in 2010-2012 before leaving lunar orbit for a flyby of the Near-Earth Asteroid 4179 Toutatis; and Chang'e 3 landed on the Moon in late 2013.

Chang'e 4, targeted for the lunar farside hemisphere, landed successfully in January 2019. It transmits radio signals to Earth via the Queqiao satellite, which reached a halo orbit around Earth-Moon L2 in June 2018. In addition to relaying signals from Chang'e 4 and its rover to Earth, Queqiao also serves as a radio observatory remote from the radio noise of Earth.

A radio-relay satellite in Earth-Moon L2 halo orbit enables communication with spacecraft out of line-of-sight radio contact on the hidden farside hemisphere of the Moon. Image credit: NASA.

Sources

"Future Missions for Libration-point Satellites," R. Farquhar, Astronautics & Aeronautics, May 1969, pp. 52-56.

"Strategic Considerations for Cislunar Space Infrastructure," IAF-93-Q.5.416, W. Mendell and S. Hoffman; paper presented at the 44th Congress of the International Astronautical Federation, 16-22 October 1993.

"Representative Human Missions to the Sun-Earth Libration Point (L2) '100' Day Class Mission," SEL2 Ver. R, Bret G. Drake, NASA Johnson Space Center, presentation materials, 20 December 1999.

"'Invisible Planets' Gain Favor as Real Estate in Space," L. David, Space.com, 19 January 2000.

More Information

Solar Flares and Moondust: The 1962 Proposal for an Interdisciplinary Science Satellite at Earth-Moon L4

Lunar GAS (1987)