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)