21 June 2017

Thirty Years of Spaceflight Outreach

Staffing the tables at Flagstaff's annual Science in the Park event, September 2012. Image credit: Lisa Gaddis
The first satellite, Sputnik 1, reached Earth orbit in 1957, and in 1987 NASA was recovering from the January 1986 Challenger accident while the Soviet Union added to the newly launched Mir space station Kvant, its first add-on module. Three decades separate those events.

I think about that eventful 30-year span when I want to feel ancient. In 1987, I began my first paid space outreach project. Now it's 2017, 30 years on, the same period of time that separated Sputnik from Mir's early days. Throughout that 30-year period, I've always had some paid space outreach activity under way, be it a freelance job writing Astronaut Hall of Fame museum text, a Fellowship at NASA Goddard producing Earth & Sky radio programs, an article assignment for Air & Space Smithsonian covering NASA space suit tests, star parties at Navajo Reservation schools as part of Lowell Observatory's outreach programs, or teaching kids to launch rockets as part of a university summer enrichment program (to name just a few of my gigs). Typically, I've had several projects aimed at "selling" spaceflight going on at any one time.

My first paid spaceflight outreach work was an Astronomy magazine article. In it, I called on people interested in space to organize and interact with people with no interest in space. Break out of the space "fandom" and share the thrill of space exploration, in other words. The article grew out of my experiences as I struggled to deal with the Challenger accident, which I felt as a harsh blow and a strong motivator to do what I could. I think I received $50 as payment. At the time I wrote the article, I was finishing my graduate degree in History in the aptly named town of Normal, Illinois.

Thirty years on, I work at the U.S. Geological Survey's Astrogeology Science Center in Flagstaff, Arizona. I am a U.S. Federal government employee working alongside and providing operational support to planetary scientists and cartographers. I'm mainly an archivist and map librarian, but I also maintain our exhibits and give tours. Yesterday I received a 10-year service pin; tomorrow I'll show 42 teachers from 19 U.S. states, Puerto Rico, and Canada around our facility. I can hardly wait.

The first big turning point in my peripatetic career was a telephone call I received from NASA Johnson Space Center (JSC) in May 1992. At the time, I was freelance writing - the Star Date radio show was a regular client - and presenting planetarium shows to school groups. The call came as a shock since I had not answered any sort of job solicitation.

It turned out that the deputy director of a part of JSC responsible for their History Office had asked her husband's best friend's brother, who was one of my editors, to recommend someone for a job that was part technical writing, part history. JSC management in its wisdom had decided to close the History Office, but there were dissenters. I was flown down to Houston for an interview in July, and on 10 August 1992, I became part of their devious plot to keep the invaluable JSC History collections intact and available.

Eventually, the pendulum swung back; a new JSC Director wanted to do a big oral history project. When those employed to carry it out went looking for documents so that they could research the careers of the people they meant to interview, the folks who had hired me magically produced the JSC History collection out of thin air.

By then, I'd moved on, launching a freelance writing career that was to last a dozen years. I'd be at it yet today, had it not been for another big turning point in my career (and, indeed, in my life). On 7 July 2007, a sleeping driver rammed my wife's car head-on on the highway a mile or so from our rural Flagstaff home, killing himself, his passengers, and my wife, and gravely injuring our daughter, who was four years old at the time.

Despite massive brain damage and seven fractures scattered across her body, she's now a normal teenager, if such a thing exists. If you're going to be nearly killed in a car crash, do it at age four, when your brain can rewire itself to bypass much of the damage. Though she needs special education help to overcome perceptual barriers, through hard work she routinely earns a place on the Honor Roll. She likes science and writing; next year, in fact, she's taking Honors Science and Honors English.

I sense a pattern emerging. Can a desire to write about science-y stuff be inherited?

I've described the kinds of paid spaceflight outreach I did in the past and what I do today. What of the future?

Raising the Kiddo, contending with the sudden loss of my dear wife, and working a steady job so our child could have health insurance despite her obvious preexisting conditions killed off the three book projects I had under way 10 years ago. I want to get back to those. As she grows older, the Kiddo becomes increasingly self-sufficient, potentially freeing up some of my time for new freelance projects. I have no desire to neglect her even as she becomes more self-sufficient, however.

There's also my status as a Federal government employee to consider. I am bound by ethics rules designed to prevent corruption. These require that any "moonlighting" I do be vetted first by ethics officials to avoid a conflict of interest. I have already had a project vetted and approved, so I am hopeful that I will in the next few years be able to publish a new book. It would be my first since my 2001 NASA-published opus Humans to Mars: Fifty Years of Mission Planning, 1950-2000.

To end this self-serving little anniversary essay, I want to acknowledge the many, many people who have made my adventures in the past 30 years possible. Some of you read this blog; your encouragement and stimulating comments keep it alive. I'll not name names in order to protect the innocent and to avoid forgetting anyone. You know who you are. Thank you, every one of you.

20 June 2017

Safeguarding the Earth from Martians: The Antaeus Report (1978-1981)

The Viking 2 landing site in Utopia Planitia, a northern plain where water frost is seen on winter mornings. The lander touched down on 3 September 1976. A three-meter arm with a scoop on the end dug into the martian surface near the lander, collecting dirt to feed into its three biology experiments. The arm was also used to push rocks and dig trenches that enabled scientists on Earth to study the top 20 centimeters or so of the martian surface. Had the arm been able to dig down deeper - perhaps as little as 30 centimeters deeper - it would have encountered water ice and the history of Mars exploration could have been very different. Image credit: NASA
In the summer of 1978, 16 university professors from around the United States gathered at NASA's Ames Research Center near San Francisco to spend 10 weeks designing an Earth-orbiting Mars sample quarantine facility. It was one of a series of similar Ames-hosted Summer Faculty Design Studies conducted since the 1960s.

At the time, NASA actively considered Mars Sample Return (MSR) as a post-Viking mission. Agency interest flagged as it became clear that no such mission would receive funding, so publication of the 1978 design study, titled Orbiting Quarantine Facility: The Antaeus Report, was delayed until 1981.

The Summer Fellows noted that the three biology experiments on the Viking landers had found neither organic carbon nor clear evidence of ongoing metabolic processes in the soil they tested on Mars. Furthermore, the Viking cameras had observed no obvious signs of life at the two rather dull Viking landing sites.

Nevertheless, the Summer Fellows argued, "the limitations of automated analysis" and the fact that "the landers sampled visually only a small fraction of one percent of the planet's surface" meant that there could be "no real certainty" about whether Mars was lifeless. This, they argued, meant that, "in the event that samples of Martian soil are returned to Earth for study, special precautions ought to be taken. . .the samples should be considered to be potentially hazardous to terrestrial organisms until it has been conclusively shown that they are not."

Their report listed three options for attempting to ensure that samples would not accidentally release martian organisms on Earth. The MSR spacecraft might sterilize the sample en route from Mars to Earth, perhaps by heating it. Alternately, the unsterilized sample might be quarantined in a "maximum containment" facility on Earth or in Earth orbit, outside our planet's biosphere.

The Summer Fellows noted that each of these three options would have advantages and disadvantages; sterilizing the sample, for example, might ensure that no martian organisms could reach Earth, but would likely also damage the sample, diminishing its scientific utility. The scientists explained that the Antaeus study emphasized the third option because it had not been studied in detail previously.

The Summer Fellows explained the significance of the name they had selected for their Orbiting Quarantine Facility (OQF) project. Antaeus was a giant in Greek mythology who forced passing travelers to wrestle with him and killed them when he won. The Earth was the source of Antaeus' power, so the hero Hercules was able to defeat the murderous giant by holding him above the ground. "Like Antaeus," they explained, a martian organism "might thrive on contact with the terrestrial biosphere. By keeping the pathogen contained and distant, the proposed [OQF] would safeguard the Earth from possible contamination."

Five 4.1-meter-diameter cylindrical modules based on European Space Agency Spacelab module hardware would form the Antaeus OQF. The Summer Fellows assumed that the modules and many of the other components needed to assemble and operate the OQF would become available during the 1980s as the Space Shuttle Program evolved into a Space Station Program.

OQF assembly in 296-kilometer-high circular Earth orbit would need two years. It would begin with the launch of drum-shaped Docking and Logistics Modules together in a Space Shuttle Orbiter's payload bay.

The 2.3-ton Docking Module, the OQF's core, would measure 4.3 meters long. It would include six 1.3-meter-diameter ports with docking units derived from the U.S. version of the 1975 Apollo-Soyuz "neuter" design. Outward-splayed guide "petals" and a system of shock absorbers and latches would enable identical docking units to link together.

The Antaeus Orbital Quarantine Facility. Image credit: NASA
In addition to the Logistics Module, Power, Habitation, and Laboratory Modules would link up with Docking Module ports. When completed, they would form what the Fellows called a "pinwheel" design. The remaining two Docking Module ports would enable Shuttle dockings, spacewalks outside the OQF with the Docking Module serving as an airlock, and attachment of additional modules if necessary.

The 4.3-meter-long Logistics Module would weigh 4.5 tons loaded with a one-month supply of air, water, food, and other supplies. After a crew took up residence on board the OQF, a Shuttle Orbiter would arrive each month with a fresh Logistics Module. Using twin robot arms mounted in the Orbiter payload bay, the Shuttle crew would remove the spent Logistics Module for return to Earth and berth the fresh one in its place.

The second OQF assembly flight would see the Shuttle crew link the 13.6-ton Power Module to the Docking Module's aft port. The Power Module would then deploy two steerable solar arrays capable of generating between 25 and 35 kilowatts of electricity. Spinning momentum wheels would provide OQF attitude control and small thrusters would fire periodically to counter atmospheric drag, which would otherwise over time cause the quarantine station to reenter. The Power Module would also provide OQF thermal control and communications.

The OQF's five-person crew would live in the 12.4-meter-long, 13.6-ton Habitation Module, which would arrive on the third assembly flight. The OQF's "command console," five crew sleep compartments, and workshop, sickbay, galley, exercise, and waste management/hygiene compartments would be arranged on either side of a central aisle. The Hab Module would provide life support for all the OQF's modules except the Laboratory Module.

The Lab Module, delivered during the fourth and final OQF assembly flight, would measure 6.9 meters long and, like the Hab and Power Modules, would weigh 13.6 tons. Not surprisingly, the Ames Faculty Fellows devoted an entire chapter of the Antaeus report to the Lab.

Spacelab pressurized modules included a central corridor running their entire length. Experiment equipment lined their walls. The Spacelab-based OQF Lab Module, on the other hand, would have a central experiment area running most of its length with corridors along its walls. Most of the experiment area would be located within glass-walled "high-hazard" "Class III" biological containment cabinets similar to those at the Centers for Disease Control in Atlanta, Georgia.

The Antaeus OQF Lab Module included an independent life support system to help prevent contamination of adjoining modules. Grills in the floor and ceiling lead to air filters. The Mars Sample Return sample canister would enter the central experiment area from above. Visible are at least three microscopes. Image credit: NASA
Analysis equipment within the cabinets would include a refrigerator, a freezer, a centrifuge, an autoclave, a gas chromatograph, a mass spectrometer, incubation and metabolic chambers, scanning electron and compound light microscopes, and challenge culture plates. The crew would operate the equipment from outside the cabinets using sleeve-like arms with mechanical grippers.

The Summer Fellows provided no obvious aids for crew positioning. In the illustration of the Lab module above, scientists are shown floating without handgrips or feet or body restraints. Given the delicate and sensitive nature of the work they were meant to perform, this would probably turn out to be a significant omission.

The Lab Module would include an independent life support system with "high efficiency particle accumulator" (HEPA) filters. Experimenters would enter and exit the Lab Module through a decontamination area, where they would don and doff respirator masks and protective clothing. If a mishap contaminated the Lab Module, the module could be detached from the OQF and boosted to a long-lived 8000-kilometer circular orbit using a Laboratory Abort Propulsion Kit delivered by a Shuttle Orbiter.

Following the two-year assembly period, a rehearsal crew would board the OQF to test its systems and try out the Mars sample analysis protocol using biological samples from Earth. The Summer Fellows set aside up to two years for these practice activities. At about the time the rehearsal crew boarded the OQF, a robotic MSR spacecraft would depart Earth on a one-year journey to Mars.

Two years later and four years after the start of OQF assembly, a small Mars Sample Return Vehicle (MSRV) containing one kilogram of martian surface material and atmosphere samples would fire rocket motors to enable Earth's gravity to capture it into a high orbit. The sample would ride within a sample canister, the exterior of which would have been sterilized during Mars-Earth transfer. Meanwhile, a Shuttle Orbiter would deliver to the OQF the first five-person sample-analysis crew. It would comprise a commander (a career astronaut with engineering training) and four scientists with clinical research experience (a medical doctor, a geobiologist, a biochemist, and a biologist).

A Shuttle-launched remote-controlled Space Tug would collect the sample canister from high-Earth orbit and deliver it to a special "docking cone" on top of the Lab Module. This is not shown in the illustration of the completed OQF; in its place, one finds a cylindrical "Sample Acquisition Port." The canister would then enter the experiment area through a small airlock.

The first sample analysis crew would cut open the canister using "a mechanism similar to a can opener." They would immediately place 900 grams of the sample into "pristine storage." Over the next 60 days, they would execute an analysis protocol that would expend 100 grams of the sample. Twelve grams each would be devoted to microbiological culturing and challenge cultures containing living cells from more than 100 Earth species; six grams each to metabolic tests and microscopic inspection for living cells and fossils; 10 grams to chemical analysis; and 54 grams to "second-order" follow-up tests.

If the 60-day analysis protocol yielded no signs of life in the test sample, a Shuttle Orbiter would carry the 900-gram pristine sample from the OQF to Earth's surface for distribution to laboratories around the world. Based on highly optimistic 1970s NASA estimates of Shuttle, Spacelab, and Station costs, the Summer Fellows placed the total cost of OQF assembly and operations for this "minimum scenario" at only $1.66 billion.

If, on the other hand, OQF scientists detected life in the Mars sample, then analysis on board the OQF could be extended for up to six and a half years. Throughout that period, Shuttle Orbiters would continue to deliver a steady stream of monthly Logistics Modules; they would also change out OQF crews at unspecified intervals. In all, about 80 Logistics Modules would reach the OQF by the time its mission ended. The cost of this "maximum scenario" might total $2.2 billion, the Ames Summer Faculty Fellows optimistically estimated.

Source

Orbiting Quarantine Facility: The Antaeus Report, D. DeVincenzi and J. Bagby, editors, NASA, 1981

More Information

Clyde Tombaugh's Vision of Mars (1959)

Peeling Away the Layers of Mars (1966)

What Shuttle Should Have Been: NASA's October 1977 Space Shuttle Flight Manifest

Making Rocket Propellants from Martian Air (1978)

Astronaut Sally Ride's Mission to Mars (1987)

31 May 2017

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

Probe release: the astronauts on board the Apollo Applications Program Venus flyby spacecraft release the last of their atmosphere-entry probes a few hours before closest approach to the cloudy planet. Meanwhile, their optical telescope, scanning radar, and other instruments switch to high-rate data-collection mode. Image credit: William Black.
For many space planners in the early 1960s, piloted Solar System exploration using large "post-Saturn" rockets and nuclear-powered spaceships seemed a natural follow-on to the Apollo lunar program. In November 1964, however, NASA Headquarters announced that its post-Apollo space program would emphasize Earth-orbital space stations based on Saturn/Apollo hardware. Their chief aim: to find space benefits for people on Earth. Agency officials explained that this was in keeping with the wishes of President Lyndon Baines Johnson. NASA critics, meanwhile, derided what they saw as its lack of an overarching goal beyond finding new uses for Apollo hardware.

The Headquarters announcement, the first high-level step on the road to the Apollo Applications Program (AAP), undermined planetary exploration planning. Even before the announcement, however, die-hard Mars planners had begun to study how Saturn/Apollo hardware could be applied to planetary voyages. In February 1965, just three months after the Headquarters announcement, NASA Marshall Space Flight Center's Future Projects Office completed the first study of Apollo-based piloted Mars and Venus flyby missions.

In February 1967, Jack Funk and James Taylor, engineers in the Advanced Mission Design Branch at NASA's Manned Spacecraft Center (MSC) in Houston, Texas, proposed as AAP's "final goal" a series of three Apollo-based piloted Venus flybys. The missions would depart Earth during 30-day launch periods beginning on 4 April 1972, 14 November 1973, and 7 June 1975. Each would require a single unmodified three-stage Saturn V rocket of the type used to launch Apollo missions to the moon, a lightly modified Apollo Command and Service Module (CSM), and a Mission Module (MM) based, perhaps, on the Apollo Orbital Research Laboratory (AORL) under study at the time.

MSC's piloted Venus flyby missions were intended to replace the piloted Mars and Mars/Venus flybys under study by the intercenter NASA Planetary Joint Action Group (JAG). MSC favored a piloted Venus flyby mission followed by a Venus orbiter because they would be of shorter duration and would need less propulsive energy than the Planetary JAG's missions. In MSC's plan, piloted Mars orbiter and piloted Mars landing missions in the late 1970s would follow successful piloted Venus flyby and Venus orbiter missions.

Funk and Taylor's 1972 AAP Venus flyby mission would begin with launch from Cape Kennedy on 2 April 1972. The Saturn V's S-IVB third stage would inject a 66,308-pound CSM with three astronauts on board and a 27,783-pound MM into a 100-nautical-mile circular parking orbit.

The stage would be restarted a few hours later to place itself and its payload into an elliptical orbit with a 70,000-mile apogee (high point above the Earth) and a 48-hour period. Payload injected into the elliptical orbit would total 107,578 pounds, or about 263 pounds beyond expected Apollo Saturn V capacity; Funk and Taylor shrugged off the shortfall, however, saying that it was so small as to be "in the noise level" of their calculations.

Venus or bust. A = J-2 rocket motor; B = Saturn V S-IVB third stage; C = Spacecraft Launch Adapter (contains Mission Module); D = Apollo Command and Service Module spacecraft. Image credit: NASA
After S-IVB shutdown, the astronauts would detach their CSM from the Spacecraft Launch Adapter (SLA) shroud, turn it end for end, and dock with the MM, which would occupy the volume within the SLA that would contain the Lunar Module during Apollo moon missions. They would use the CSM to pull the MM free of the spent S-IVB stage, then would transfer to the MM to deploy its twin solar arrays, check out its systems, and perform navigational checks during the 24-hour climb to apogee.

The next day, the astronauts would return to their couches in the CSM as the flyby spacecraft neared apogee. They would then fire the Service Propulsion System (SPS) main engine in the CSM's Service Module (SM) to raise the perigee (low point above Earth) of their spacecraft's orbit and tilt its orbital plane relative to Earth's equator. The drum-shaped SM would contain 40,000 pounds of propellants, enabling a total velocity change of 4800 feet per second.

In addition to refining the flyby spacecraft's trajectory for the Venus injection burn, which would occur at perigee, the apogee maneuver would test the SPS. If the engine failed, the astronauts would abort the mission by discarding the MM and lowering the CSM's perigee into Earth's atmosphere by firing special aft-mounted auxiliary attitude control thrusters near apogee. When the CSM approached perigee 24 hours later, they would cast off the SM and reenter in the conical Command Module (CM).

Trans-Venus Injection scenario. See text for explanation. Image credit: NASA
If, on the other hand, the SPS performed the apogee maneuver successfully, the flyby spacecraft would reach perigee outside Earth's atmosphere traveling at 9710 feet per second. The astronauts would then ignite the SPS a second time to add a little more than 3000 feet per second to the flyby spacecraft's velocity and depart Earth orbit for Venus on 5 April 1972. Abort using the SPS would remain possible for six minutes after the completion of the Trans-Venus Injection burn; return to Earth following a post-injection abort could last up to two days.

Immediately after the Trans-Venus Injection burn, the astronauts would shut down the CSM to extend its lifetime and move back to the MM. They would reactivate the CSM three times during the 109-day flight to Venus so that they could perform small course correction burns using the SPS. Course correction navigation would be by Earth-based radar backed up by a hand-held sextant and a navigational computer in the MM.

Funk and Taylor calculated that the CSM would need 2000 pounds of extra meteoroid shielding for a Venus mission. Shielding - probably in the form of a Whipple Bumper (a thin layer of metal or plastic sheeting suspended a few inches from the hull that would break up meteoroids, reducing the damage they could inflict on the spacecraft) - would cover the entire CM and the SM tanks and SPS.

Artist William Black's interpretation of the AAP Venus flyby Mission Module (left) is a clever synthesis and expansion of two candidate designs portrayed in only modest detail in Funk and Taylor's report. The first was a drum-shaped module wasteful of the limited volume within the Spacecraft Launch Adapter (SLA); the second was bell-shaped and thus structurally complex.  
Emphasis on the Mission Module: following detachment from the Saturn V S-IVB stage, the AAP Venus flyby Mission Module would deploy its appendages. These would include four dish antennas for receiving data from atmosphere-entry probes (the probes are shown here arrayed around a circular airlock hatch); a mapping radar antenna (see previous image); twin rectangular solar arrays on booms for making electricity; a tracking optical telescope; and a high-gain radio antenna for communication with Earth. Image credit: William Black
Funk and Taylor based their mission's 3400-pound science experiment package on the Mars flyby science package proposed in the October 1966 Planetary JAG report. It would include impactor probes for obtaining atmosphere measurements during descent, soft landers, cameras, and, if weight growth during its development could be strictly controlled, a 40-inch telescope, but would lack the Mars flyby mission's sample-returner lander. The MIT-built CSM guidance computer would be upgraded and equipped with a tape recorder to allow it to collect and store data from the science instruments for return to Earth.

The astronauts would perform solar, space environmental, and astronomical observations during the Earth-Venus transfer and would begin deploying automated probes a few days before the 23 August 1972 Venus flyby. Closest approach to the planet would occur over the day side.

Using the SPS, the astronauts would perform three small course corrections during the 250-day voyage to Earth. As the homeworld grew in their viewports, the astronauts would transfer to the CSM and undock from the MM. On 30 March 1973, just 359 days after Earth launch, they would carry out a final course correction, then would detach the CM from the SM and re-enter Earth's atmosphere. A beefed-up heat shield would permit the CM to withstand atmosphere reentry at up to 45,000 feet per second (that is, about 9000 feet per second faster than Apollo lunar return speed).

Trajectory and key dates for the Venus flyby mission departing Earth on 5 April 1972. Venus flyby occurs on 23 August 1972; Earth return on 30 March 1973. Image credit: NASA
The second mission in the series would depart Earth on 14 November 1973 and fly past Venus 104 days later. It would reach Earth 252 days after that, for a total mission duration of 356 days. The third mission would leave Earth on 7 June 1975. Passage to Venus would need 115 days and return to Earth 252 days, for a total duration of 367 days.

The 1973 mission Venus flyby spacecraft would need the most propulsive energy to depart Earth orbit for Venus - a total of 12,150 feet per second, or about 70 feet per second more than the 1972 spacecraft and 300 feet per second more than the 1975 spacecraft. The 1972 CM would have the fastest Earth-atmosphere reentry speed (45,000 feet per second), while the 1973 CM would reenter moving at 44,500 feet per second and the 1975 CM at 44,000 feet per second.

Funk and Taylor's AAP Venus flyby plan stands out from the many 1960s plans for piloted flybys because it has been brought to life as fiction. In his 2017 alternate history Island of Clouds: The Great 1972 Venus Flyby, author Gerald Brennan puts narrative meat on the technical skeleton Funk and Taylor presented in their MSC Internal Note.

Told in the first person by a believable fictional Buzz Aldrin, Brennan's tale owes much to the Apollo 11 moon-walker's autobiography Return to Earth (1973). Its focus on exploration far from rescue puts Island of Clouds in a class with Hank Searls' classic 1964 adventure The Pilgrim Project (described elsewhere in this blog - click on the last link under "More Information" below).

Six months after Funk and Taylor completed their study, AAP bore the brunt of more than $500 million in Congressional cuts to NASA's Fiscal Year 1968 budget. The program, which for a time in 1966 had been planned to include some 40 Earth-orbital and lunar missions, shrank rapidly during 1968-1969. It was officially renamed the Skylab Program in February 1970. Between May 1973 and February 1974, three three-man crews occupied the Skylab Orbital Workshop in Earth orbit for a total of 173 days.

Robot probes, not astronauts, explored Venus in the 1970s. The Soviet Union's Venera 8 took advantage of the 1972 launch opportunity, leaving Baikonur Cosmodrome in Central Asia on 27 March 1972. The armored probe landed on Venus and transmitted data on its brutal surface conditions for 50 minutes. The U.S. Mariner 10 probe (launched 3 November 1973) flew past Venus en route to Mercury on 5 February 1974.

After skipping the 1973 Venus opportunity to launch Mars probes, the Soviets launched Venera 9 and Venera 10 on 8 and 14 June 1975, respectively. Each consisted of an orbiter and a lander. The Venera 9 lander transmitted the first picture of the Venusian surface on 22 October. Venera 10's lander set a new endurance record on 23 October, returning data from the surface for 65 minutes before its orbiter passed out of radio range.

The first, fourth, and fifth images in this post are Copyright 2017 by William Black (http://william-black.deviantart.com/) and are used by special arrangement with the artist.

Source

Preliminary Mission Study of a Single-Launch Manned Venus Flyby with Extended Apollo Hardware, MSC Internal Note No. 67-FM-25, J. Funk & J. Taylor, Advanced Mission Design Branch, Mission Planning and Analysis Division, NASA Manned Spacecraft Center, Houston, Texas, 13 February 1967

More Information

EMPIRE Building: Ford Aeronutronic's 1962 Plan for Piloted Mars-Venus Flybys

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

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

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

Space Race: The Notorious 1962 Proposal to Launch an Astronaut on a One-Way Trip to the Moon

16 May 2017

Venus As Proving Ground: A 1967 Proposal for a Piloted Venus Orbiter

Mariner II during its final days on Earth, July-August 1962. Image credit: NASA
NASA won a significant prestige victory over the Soviet Union on 14 December 1962, when Mariner II flew past Venus at a distance of 22,000 miles. The 203.6-kilogram spacecraft, the first successful interplanetary probe in history, left Cape Canaveral, Florida, on 27 August 1962. Controllers and scientists breathed a sigh of relief as it separated from its Atlas-Agena B launch vehicle; failure of an identical rocket had doomed its predecessor, Mariner I, on 22 July 1962.

Astronomers knew that Venus was nearly as large as Earth, but little else was known of it, for its surface is cloaked in dense white clouds. Many supposed that, because it is a near neighbor and similar in size to our planet, Venus would be Earth's twin. As late as 1962, some still hoped that astronauts might one day walk on Venus under overcast skies and perhaps find water and life.

Data from Mariner II effectively crossed Venus off the list of worlds where astronauts might one day land. As had been suspected since 1956, when radio astronomers first detected a surprising abundance of three-centimeter microwave radiation coming from the planet, Venus's surface temperature was well above the boiling point of water. Mariner II data indicated a temperature of at least 800° Fahrenheit over the entire planet. Cornell University astronomer Carl Sagan explained the intense heat: Venus has a dense carbon dioxide atmosphere that behaves like glass in a greenhouse.

Venus's role in piloted spaceflight thus shifted from a destination in its own right to a kind of "coaling station" for spacecraft traveling to and from Mars. Mission planners proposed ways that a piloted Mars spacecraft might use Venus's gravity to alter its course, slow down, or speed up without expending rocket propellants.

Some also began to view Venus as a proving ground for incremental space technology development. In 1967, NASA Lewis Research Center (LeRC) engineer Edward Willis proposed a manned Venus orbiter based on an "Apollo level of propulsion technology" for the period immediately after the Apollo moon missions.

Willis rejected piloted Mars and Venus flyby missions, which were under consideration as a post-Apollo NASA goal at the time he wrote his paper, in large part because he believed that they would not provide enough exploration time near the target planet. Though he sought a piloted Venus orbiter, Willis questioned the wisdom of launching an equivalent mission to Mars. "It is generally felt," he explained, "that the. . .objective of a manned Mars flight should be a manned landing and surface exploration," not merely a stint in Mars orbit.

The NASA LeRC engineer calculated that the mass of propellants needed for a piloted Venus orbiter would be considerably less than for a piloted Mars orbiter even in the most energetically demanding Earth-Venus minimum-energy transfer opportunity. This meant that a piloted Mars orbiter would always need more costly heavy-lift rocket launches to boost its propellants and components into low-Earth orbit than would a piloted Venus orbiter.

A piloted Mars landing mission, for its part, would be "still heavier than the [Mars] orbiting mission," so probably would "best be done using nuclear propulsion." Whereas chemical rockets generally need two propellants - fuel plus oxidizer to "burn" the fuel - nuclear-thermal rockets need only one working fluid. Liquid hydrogen is most often cited, though liquid methane is also mentioned.

Because they need to lug around the Solar System only one propellant, nuclear-thermal rockets are inherently more efficient than chemical rockets. Nuclear-thermal propulsion would, however, need more development and testing before it could propel humans to Mars. Nuclear-thermal propulsion was unlikely to be ready by the time Apollo ended; therefore, Willis wrote, "in terms of [technological] difficulty and timing, the Venus orbiting mission has a place ahead of the Mars orbiting and landing missions."

The key to a Venus orbiter with the lowest possible propellant mass, Willis explained, was selection of an appropriate Venus orbit. Entering and departing a highly elliptical orbit about Venus would need considerably less energy (hence, propellants) than would entering and departing a close circular Venus orbit. He thus proposed a Venus orbit with a periapsis (low point) of 13,310 kilometers (1.1 Venus radii) and a apoapsis (high point) of 252,890 kilometers (20.9 Venus radii).

The 129,250-pound (dry weight) Earth-departure stage (A in the cutaway drawing above) and the Venus orbiter spacecraft would be launched into Earth orbit separately. After the stage was loaded with 942,500 pounds of propellants in orbit, it would link up with the spacecraft. The stage would expend 930,000 pounds of propellants to increase the spacecraft's speed by 2.8 miles per second, launching it out of Earth orbit toward Venus. It would stay attached to the spacecraft until after a course-correction burn halfway to Venus that would expend an additional 12,500 pounds of propellants. The 332,000-pound Venus orbiter spacecraft, which could reach Earth orbit atop a single uprated Saturn V rocket, would comprise 10,000 pounds of Venus atmosphere probes (B), the 103,000-pound Venus arrival rocket stage (C), a 30,000-pound Venus scientific remote sensor payload (D), the 95,120-pound Venus departure rocket stage (E), the 4,000-pound Venus-Earth course-correction stage (F denotes tanks; engines are too small to be seen at this scale), the Command Module (G) for housing the crew, and the Earth atmosphere entry system (H), a 15,250-pound lifting-body with twin winglets for returning the crew to Earth's surface at the end of the mission. Of the Command Module's 66,000-pound mass, food, water, and other expendable supplies would account for 27,000 pounds. Image credit: NASA
Willis calculated that a Venus orbiter based on Apollo-level technology, departing from a 400-mile-high circular Earth orbit, staying for 40 days in his proposed Venus orbit, and with a total mission duration of 565 days, would have a mass of 1.412 million pounds just prior to Earth-orbit departure in the energetically demanding 1980 Earth-Venus transfer opportunity. An equivalent Mars orbiter launched in 1986, the least demanding Earth-Mars transfer opportunity of any Willis considered, would have a mass in Earth orbit about 70% greater - about 2.4 million pounds.

As the spacecraft approached Venus, its crew would turn it so that the Venus arrival stage faced forward, then would ignite the stage as it passed closest to Venus to slow the spacecraft by 0.64 miles per second. This would enable Venus's gravity to capture the spacecraft into its elliptical operational orbit. The maneuver would expend 91,950 pounds of propellants. The spent arrival stage would remain attached to the spacecraft at least until the Venus atmosphere entry probes were released.

The spacecraft would complete two orbits of Venus during its 40-day stay. Time within 26,300 kilometers (three Venus radii) of the planet would total two days; that is, several times longer than a piloted Venus flyby could spend near the planet (Willis's Venus orbiter would, however, not pass as close to Venus as would a Venus flyby spacecraft). Throughout their stay in orbit, the crew would turn remote sensors toward Venus. During the two periapsis passes, the astronauts would use radar to explore the mysterious terrain hidden beneath the Venusian clouds.

Farther out from the planet, near apoapsis, they would deploy the Venus atmosphere entry probes. Their spacecraft's distant apoapsis, combined with Venus's slow rotation rate (once per 243 Earth days), would enable them to remain in direct radio contact with their probes for days - unlike a piloted Venus flyby spacecraft, which could at best remain in contact with its probes for a few hours.

At the end of their stay in Venus orbit, the crew would cast off the Venus scientific payload and ignite the Venus departure stage at periapsis, expending 86,970 pounds of propellants and adding 1.14 miles per second to their speed. During the trip home, which would take them beyond Earth's orbit, they would discard the Venus departure stage and perform a course correction, if one were needed, using the small course correction stage attached to the Command Module.

Near Earth, the crew would separate from the Command Module in the Earth atmosphere entry lifting-body and enter the atmosphere at a speed of 48,000 feet per second. After banking and turning to shed speed, they would glide to a land landing, bringing to a triumphant conclusion humankind's historic first piloted voyage beyond the moon.

Source

Manned Venus Orbiting Mission, NASA TM X-52311, E. Willis, 1967

More Information

Centaurs, Soviets, and Seltzer Seas: Mariner II's Venusian Adventure (1962)

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

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

Floaters, Armored Landers, Radar Orbiters, and Drop Sondes: Automated Probes for Piloted Venus Flybys (1967) 

Things to Do During a Venus-Mars-Venus Piloted Flyby Mission (1968)

Two for the Price of One: 1980s Piloted Mars-Venus Missions With Stopovers at Mars and Venus (1969)

10 May 2017

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

The Skylab 2 Apollo CSM and Saturn IB launcher stand ready atop the "milk stool" on Pad 39B at NASA's Kennedy Space Center, May 1973. Image credit: NASA
From its conception in 1959 until President John F. Kennedy's 25 May 1961 call to put a man on the moon, Apollo was seen mainly as an Earth-orbital spacecraft. NASA intended to use Apollo in the second and third phases of its planned 1960s piloted space program. The first phase, characterized by suborbital flights lasting minutes and sorties into Earth orbit lasting at most a few days, would be accomplished by brave pioneers in missile-launched single-seater Mercury capsules.

In the second phase, three astronauts would live and work on board Apollo spacecraft for ever-longer periods. They would use a pressurized Mission Module (MM) launched attached to their spacecraft as a small space station. The third phase would see Apollo spacecraft transport crews to and from an Earth-orbiting space station. Cargo bound for the station would ride in the MM. An Apollo circumlunar mission - a flight around the moon without capture into lunar orbit - was an option, but was considered unlikely before 1970.

Simplified cutaway of the General Electric D-2 Apollo, perhaps the most widely known of the pre-Apollo lunar landing program Apollo designs. Colored lines represent separation planes: orange is the spacecraft/launch vehicle separation plane; red is the abort separation plane (two "pusher" solid-propellant abort rockets are visible on the outside of the Service Module); green is the shroud/Service Module separation plane; and blue is the Mission Module/Command Module separation plane. In the event of a launch abort, the part of the Service Module to the right of the red line would remain attached to the launch vehicle. During reentry, the spacecraft would first split along the green line, then the Command Module would separate from the Mission Module along the blue line. The shroud would remain with the Mission Module. The Command Module would lower on parachutes and perform a land landing while the Service Module and Mission Module/shroud would burn up. Image credit: General Electric/DSFPortree 
Following studies that lasted six months, in mid-May 1961 General Electric (GE), The Martin Company, and Convair submitted Apollo spacecraft designs suited to NASA's three-phase plan. In the event, none of the designs left the drawing board; after Apollo became NASA's lunar landing mission spacecraft, the agency funded new studies and selected North American Aviation (NAA) as its Apollo spacecraft contractor.

Initially, NASA intended to land NAA's Apollo on the moon atop a descent stage with landing legs. In July 1962, however, after more than a year of sometimes acrimonious discussion and study, the space agency selected Lunar Orbit Rendezvous (LOR) as its lunar landing mission mode. NAA's Command and Service Module (CSM) spacecraft became the LOR mission's moon-orbiting mother ship, and to Grumman's bug-like Lunar Module (LM) went the honor of landing on the moon.

Before the Lunar Module. Image credit: NASA
As flown, the CSM, which measured a little more than 11 meters long, comprised the conical Command Module (CM) and the drum-shaped Service Module (SM). The MM of the May 1961 GE, Martin, and Convair designs was judged unnecessary for lunar landing missions. In fact, at first some sources perceived the LM as the MM's replacement.

The CM's nose carried a probe docking unit, and at the aft end of the SM was mounted the Service Propulsion System (SPS) main engine. The SPS remained sized for CSM launches from the lunar surface, which meant that it was more powerful than necessary for CSM insertion into and escape from lunar orbit.

Technical details of the Apollo Command and Service Module (CSM) spacecraft configured for lunar missions. Image credit: NASA
The CM also included a pressurized crew compartment, crew couches, flight controls, a compact guidance computer, rendezvous aids, a bowl-shaped heat shield for Earth atmosphere reentry, reentry batteries, and parachutes for descent to a gentle splashdown at sea.

The SM, which was discarded before atmosphere reentry, included propellant tanks, fuel cells for making electricity and water, fuel cell reactants (liquid oxygen and liquid hydrogen), four attitude-control thruster quads, radiators for discarding excess heat generated by on board systems, a high-gain radio antenna, and room for a Scientific Instrument Module (SIM) Bay. An umbilical housing linked CM and SM.

Almost all piloted Apollo Earth-orbital missions were launched atop two-stage Saturn IB rockets. The sole exception was Apollo 9 (3-13 May 1969), which used NASA's fourth Saturn V. All Apollo lunar missions left Earth on three-stage Saturn V rockets.

Apollo 7 and Apollo 9 were test flights, so their CSMs operated exclusively in low-Earth orbit. This image shows the CM of the Apollo 9 CSM Gumdrop as viewed from the LM Spider in May 1969. Apart from thruster quads and antennas, very little of Gumdrop's SM is visible. No other Apollo spacecraft would operate only in low-Earth orbit until the Skylab 2 CSM flew in May 1973. Image credit: NASA
The United States began to abandon the technology of piloted lunar exploration by late 1967, nearly a year before the first astronauts reached Earth orbit in an Apollo CSM (Apollo 7, 11-22 October 1968). Abandonment of the moon began with deep cuts in the Apollo Applications Program (AAP), the planned successor to the Apollo lunar program. Ambitious two-week stays on the moon were among the first AAP missions to feel the budget-cutters' blades.

In early 1970, NASA brought together the parts of AAP that survived - several space station-related Earth-orbital missions - to form the Skylab Program, which was expected to include at least one and possibly two temporary Skylab Orbital Workshops. The first, Skylab A, was meant to receive at least three Apollo CSMs, each bearing a three-man crew, over a period of about nine months.

By late 1970, with just two Apollo moon landings (Apollo 11 and Apollo 12) and the Apollo 13 accident under its belt, NASA cancelled three lunar landing missions. Apollo 20, the planned final Apollo lunar mission, was cancelled in early 1970 to free up its Saturn V rocket to launch Skylab A. Apollo 15, the planned fourth and last walking mission, was cancelled in September 1970, as was Apollo 19. NASA Administrator Thomas Paine dropped the missions at least partly in an attempt to curry favor for a permanent Space Station from President Richard Nixon. The space agency renumbered the surviving missions so that Apollo lunar exploration would end with Apollo 17.

On 27 August 1971, Philip Culbertson, director of the Advanced Manned Missions Program Office at NASA Headquarters in Washington, DC, dispatched a letter to Rene Berglund, Manager of the Space Station Project Office at NASA's Manned Spacecraft Center (MSC) in Houston, Texas. In it, he outlined five Earth-orbital CSM missions for the 1970s that were "still under active consideration" at NASA Headquarters.

Culbertson explained that his letter was meant to "emphasize the importance" of statements he had made in a telephone conversation with Berglund on 19 August. Based on his letter, Culbertson had phoned Berglund in an effort to impress on him the seriousness of NASA's budget situation.

Space Base: a large permanent Space Station, c. 1980. The nuclear-powered station would have had a crew of from 50 to 100 persons. Image credit: NASA
Berglund and his predecessor at MSC, Edward Olling, had throughout the 1960s remained staunch advocates of a large permanent Earth-orbiting space station. MSC Director Robert Gilruth was also a station supporter. They regarded AAP as at best a not-too-necessary rehearsal for a Space Station; they saw it at worst as a waste of time and money. They anticipated that before the mid-1970s AAP would draw to a close, freeing up funds for a real Space Station.

By mid-1971, however, it was increasingly obvious that a permanent Space Station was of interest neither to Nixon's White House nor the Congress. In fact, a reusable Space Station logistics resupply and crew rotation vehicle - a Space Shuttle - was by then emerging as the preferred post-Apollo program. The Space Station - if it were built at all - would have to wait until the Shuttle could launch its modules and bring them together in Earth orbit.

Culbertson referred to an unspecified new contract MSC had awarded CSM contractor North American. He told Berglund that, in "the early stages of your contract. . .you should concentrate on defining the CSM modifications required to support each of the [five] missions and possibly more important defining the effort at North American which would hold open as many as possible of the options until the end of the [Fiscal Year] 1973 budget cycle." Fiscal Year 1973 would conclude on 1 October 1973.

Culbertson's five missions were all to some degree Space Station-related. The first and simplest was an "independent CSM mission for earth observations." Earth observation by astronauts was often mentioned as a Space Station justification. The mission's CSM would probably include a SIM Bay fitted out with remote-sensing instruments and cameras. At the end of the mission, an astronaut would spacewalk to the SIM Bay to retrieve film for return to Earth in the CM.

A SIM Bay was part of the final three Apollo lunar CSMs. The image above shows the Apollo 15 CSM Endeavour in lunar orbit with its rectangular SIM Bay (upper center) open to space. Image credit: NASA
The second mission on Culbertson's list was an Apollo space station flight that would have been almost unimaginable at the time Kennedy diverted Apollo to the moon. It would see a CSM dock in Earth orbit with a Soviet Salyut space station.

Salyut 1, the world's first space station, had reached Earth orbit on 19 April 1971. The 15.8-meter-long station remained aloft as Culbertson wrote his letter, but had not been manned since the Soyuz 11 crew of Georgi Dobrovolski, Viktor Patseyev, and Vladislav Volkov had undocked on 29 June 1971, after nearly 24 days in space (at the time, a new world record for human space endurance). The three cosmonauts had suffocated during reentry when a malfunctioning valve caused their capsule to lose pressure, so the Soviet Union halted all piloted missions while the Soyuz spacecraft underwent a significant redesign.

The third Earth-orbital CSM mission on Culbertson's list combined the first two missions. The CSM crew would turn SIM Bay instruments toward Earth before or after a visit to a Salyut.

Culbertson's fourth CSM mission would see CSM-119 dock first with a Salyut for a brief time, then undock and rendezvous with the dormant Skylab A Orbital Workshop. After docking with and reviving Skylab A, CSM-119's crew would live and work on board for an unspecified period.

Image credit: NASA
NASA planned that, during the three CSM missions to Skylab A in the basic Skylab Program, CSM-119 would stand by as a rescue vehicle capable of carrying five astronauts (Commander, Pilot, and the three rescued Skylab A crewmen). The Salyut-Skylab A mission, which would include no rescue CSM, was planned to begin 18 months after Skylab A reached orbit, or about nine months after the third Skylab A mission returned to Earth.

The fifth and final Earth-orbital CSM mission was really two (or possibly three) CSM missions. A pair of "90 day" CSMs would dock with the Skylab B station while a rescue CSM modified to carry five astronauts stood by. NASA had funded partial assembly of Skylab B so that it would have a backup in the pipeline in case Skylab A failed. Reflecting uncertainty about the availability of Saturn rockets and CSMs, Culbertson gave no date for the Skylab B launch.

Of the five missions Culbertson declared to be on the table in August 1971, none flew. In January 1972, Nixon called on Congress to fund Space Shuttle development, and Congress agreed. Shuttle costs and continued NASA budget cuts pushed even the least complex and cheapest of Culbertson's five missions off the table.

For a short time, his second mission looked to be within reach. Formal joint U.S./U.S.S.R. planning for an Apollo docking with a Salyut was under way when Culbertson wrote his letter. In early April 1972, however, shortly before finalizing its agreement with NASA to conduct a joint Apollo-Salyut mission, the Soviet Union declared the concept to be impractical and offered instead a docking with a Soyuz.

NASA was disappointed to lose an opportunity for an early post-Skylab space station visit; the Nixon White House, on the other hand, saw the mission as a poster child for its policy of detente with the Soviet Union, so any sort of piloted docking mission would do. At the superpower summit in Moscow on 24 May 1972, Nixon and Soviet Premier Alexei Kosygin signed the agreement creating the Apollo-Soyuz Test Project (ASTP).

Skylab A, redesignated Skylab I (but more commonly called simply Skylab), reached orbit on 14 May 1973 on a two-stage Saturn V. It suffered damage during ascent, but NASA and its contractors pulled it back from the brink.

Skylab in a photograph taken by the second crew to live on board. Signs of damage the Orbital Workshop suffered during ascent to low-Earth orbit are obvious: one solar array wing is missing (left) and a hastily improvised solar shield stands in for the reflective meteoroid shield that would have protected Skylab's crew volume from the Sun. Image credit: NASA
The three CSM missions to Skylab spanned 25 May-22 June 1973, 28 July-25 September 1973, and 16 November 1973-8 February 1974, respectively. Leaks in attitude control thrusters on the second CSM to dock with Skylab caused NASA to ready CSM-119 for flight, going so far as to roll it and its Saturn IB rocket out to the launch pad; the leaks stopped by themselves, however, so the rescue CSM remained earthbound.

In August 1973, with Skylab functioning well in Earth-orbit, NASA began to mothball its backup. Several plans were floated for putting Skylab B to use in Earth orbit. In December 1976, however, NASA donated its second space station to the newly opened Smithsonian National Air and Space Museum on the National Mall in Washington, DC.

Apollo CSM-111 was the ASTP prime spacecraft, while CSM-119 was refitted to serve as its backup. In the event, the backup was not needed. CSM-111, officially designated "Apollo" (but sometimes informally called Apollo 18), docked with Soyuz 19 on 17 July 1975. CSM-111 did not include a SIM Bay. The last CSM to reach space undocked on 19 July and, after a period during which its crew performed experiments in the CM, splashed down in the Pacific Ocean near Hawaii on 24 July 1975, six years to the day after Apollo 11, the first moon landing mission, returned to Earth.

Artist concept of the Apollo-Soyuz docking in Earth orbit, 17 July 1975. Image credit: NASA
Sources

A Summary of NASA Manned Spacecraft Center Advanced Earth Orbital Missions Space Station Activity from 1962 to 1969, Maxime Faget & Edward Olling, NASA Manned Spacecraft Center, February 1969

Letter, Philip E. Culbertson to Rene A. Berglund, 27 August 1971


Skylab News Reference, NASA Office of Public Affairs, March 1973, pp. IV-6 - IV-8


Living and Working in Space: A History of Skylab, NASA SP-4298, W. David Compton and Charles Benson, NASA, 1983


Thirty Years Together: A Chronology of U.S.-Soviet Space Cooperation, NASA CR 185707, David S. F. Portree, February 1993, pp. 9-26 (http://ntrs.nasa.gov/search.jsp?R=19930010786 - accessed 10 May 2017)


Mir Hardware Heritage, NASA RP 1357, David S. F. Portree, March 1995, pp. 33-35, 65-72 (http://history.nasa.gov/SP-4225/documentation/mhh/mhh.htm - accessed 10 May 2017)


"Skylab B: Unflown Missions, Lost Opportunities," Thomas Frieling, Quest, Volume 5, Number 4, 1996


More Information

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

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

"A True Gateway": Robert Gilruth's June 1968 Space Station Presentation

Apollo's End: NASA Cancels Apollo 15 & Apollo 19 to Save Station/Shuttle (1970)

A Bridge from Skylab to Station/Shuttle: Interim Space Station Program (1971)

Skylab-Salyut Space Laboratory (1972)

What If a Crew Became Stranded On Board the Skylab Space Station? (1972)

Reviving & Reusing Skylab in the Shuttle Era: NASA Marshall's November 1977 Pitch to NASA Headquarters

29 April 2017

Two for the Price of One: 1980s Piloted Missions with Stopovers at Mars and Venus (1969)

The authors of the dual-stopover study did not design a spacecraft. The 6.4-year cycle of mission opportunities they identified repeats endlessly, however, so the NASA image above, which shows a present-day design for a piloted Mars spacecraft, can be pressed into service to illustrate this post. With relatively minor changes, this spacecraft might orbit both Mars and Venus during a single mission. 
The piloted flyby missions NASA studied in the 1960s often included close encounters with both Mars and Venus. The October 1966 NASA Planetary Joint Action Group report Planetary Exploration Utilizing a Manned Flight System, for example, emphasized a piloted Mars flyby mission departing Earth orbit during the September 1975 free-return opportunity, but also noted an opportunity to launch a Earth-Venus-Mars-Venus-Earth flyby in February 1977 and an Earth-Venus-Mars-Earth flyby in December 1978.

Piloted flybys in the 1970s were intended to clear a path to piloted "stopover" missions in the 1980s. Stopovers - a category which included Mars and Venus orbiters and Mars landings - almost always emphasized a single objective. That is, each mission would travel to a single world, then return to Earth. The closest stopovers came to visiting more than a one planet was when a Mars stopover mission performed a Venus "swingby" to bend its course, slow its approach to Earth to enable a safe direct Earth-atmosphere reentry, or accelerate toward Mars.

During a Venus swingby, a Mars stopover spacecraft might explore the cloudy planet much as piloted Venus flybys were meant to do. That is, it might drop off probes insulated and armored against Venusian temperatures and pressures and scan the hidden Venusian surface with radar.

That a piloted spacecraft might stop at both Mars and Venus during a single mission was unthinkable. It was widely accepted that such a mission would demand enormous quantities of propellants, all of which would need to be launched into Earth orbit atop costly heavy-lift rockets.

In a brief September 1969 NASA Technical Memorandum, E. Willis and J. Padrutt, mathematicians at NASA's Lewis Research Center (LeRC) in Cleveland, Ohio, sought to overturn the prevailing view of what would be possible during stopover missions. Lead author Willis was no stranger to NASA piloted Mars mission planning: he had designed interplanetary trajectories at LeRC at least since early 1963.

Willis and Padrutt's mission design would see a piloted spacecraft depart a circular low-Earth orbit and capture into an loosely bound high-apogee elliptical orbit around Mars or Venus. It would then transfer to a loosely bound high-apogee elliptical orbit around Mars (if the first stopover was at Venus) or Venus (if the first stopover was at Mars). From there, the spacecraft would transfer back to Earth, where the crew would reenter the atmosphere directly in a small capsule. Its usefulness ended, the dual-stopover spacecraft would, meanwhile, swing past Earth into a disposal orbit around the Sun.

The mission plan was designed to reduce the amount of energy required to move between worlds, thus conserving propellant. The piloted dual-stopover spacecraft would travel between planets only when an opportunity for a minimum-energy transfer occurred; that is, only when the planets moved into positions relative to each other necessary for a minimum-energy transfer. Loosely bound orbits would reduce energy needed to capture into and escape from orbit. Direct reentry into Earth's atmosphere would ideally require only enough energy to deflect the capsule's course so that it would intercept Earth after it separated from the dual-stopover spacecraft.

The LeRC mathematicians calculated the total "propulsive effort" necessary to carry out the seven dual-stopover missions in the 1979-1986 cycle. They measured propulsive effort in terms of the total velocity change firing the dual-stopover spacecraft's rocket motor would produce. Firing the motor would expend precious propellant, so most of the time small velocity changes were to be preferred over large ones.

They explained that they had discovered a repeating 6.4-year cycle of seven potentially useful dual-stopover mission opportunities. The seven opportunities varied only slightly from one 6.4-year cycle to the next. The first, fourth, and sixth opportunities would begin with an Earth-Mars transfer, while the second, third, fifth, and seventh would begin with an Earth-Venus transfer. In most cases, the minimum propulsive effort needed to perform Earth-Venus-Mars-Earth dual-stopovers would be less than that needed for Earth-Mars-Venus-Earth dual-stopovers. In their paper, Willis and Padrutt emphasized the 6.4-year cycle that would begin in late 1979.

A hand-drawn illustration from Willis and Padrutt's NASA Technical Memorandum outlines the dual-stopover mission beginning in late 1979. 1 = departure from circular low-Earth orbit on a minimum-energy path to Mars. 2 = Arrival in high-apogee elliptical Mars orbit at the beginning of a 78-day stopover during which Mars's position changes as it orbits the Sun. 3 = Mars departure on a minimum-energy path to Venus. 4 = Arrival in high-apogee elliptical Venus orbit at the beginning of a 177-day stopover during which Venus's position changes as it orbits the Sun. 5 = Venus departure on a minimum energy path to Earth. 6 = Arrival at Earth. Image credit: NASA
A spacecraft launched during the late 1979 dual-stopover mission opportunity would spend 78 days at Mars and 177 days at Venus. During each stopover, the planet would orbit the Sun, eventually reaching the correct position to enable the spacecraft to make a minimum-energy transfer to its next destination planet. The Earth-Mars, Mars-Venus, and Venus-Earth tranfer legs of its voyage would together require 638 days. Adding the time spent at Mars and Venus to the time spent between worlds would yield a mission duration of 894 days - that is, slightly less than two and a half years. Total propulsive effort would amount to 9.382 kilometers per second (kps).

The second opportunity of the 6.4-year cycle would occur in the first half of 1980. The dual-stopover spacecraft would depart Earth on a minimum-energy path to Venus. It would spend 180 days at Venus, 10 days at Mars, and 669 days between worlds, for a total mission duration of 860 days (two and a third years). This made it the shortest dual-stopover mission of the seven-mission cycle.

Because short missions limited the time available for hardware breakdowns and the crew biomedical problems, they were to be preferred to long ones. Willis and Padrutt acknowledged, however, that the opportunity's short stopover at Mars would provide little time for exploration. Total propulsive effort would amount to 8.738 kps.

The third opportunity would occur in late 1981. The dual-stopover spacecraft would leave Earth for Venus, where it would spend about 265 days. It would stop over for 133 days at Mars, and spend 629 days between worlds, yielding a total mission duration of 1027 days (nearly three years). Total effort would equal 8.7 kps.

The fourth opportunity would occur at the end of 1981. The dual-stopover spacecraft would leave Earth for Mars. It would spend about 274 days at Mars, 340 days at Venus, and 680 days between planets, for a total duration of about 1294 days (a little more than three and a half years). Total propulsive effort would equal 9.252 kps.

The fifth opportunity would occur in the first half of 1983. The dual-stopover spacecraft would leave Earth for elliptical Venus orbit, where it would spend just 10 days. It would spend 601 days at Mars and 619 days between worlds, yielding a mission duration of 1230 days (a little less than three and a half years). Total propulsive effort would total 8.896 kps. The short stopover at Venus might make the opportunity undesirable; on the other hand, the mission's Mars stopover would be the lengthiest in the 6.4-year cycle, enabling a long period of exploration.

The sixth opportunity would see the dual-stopover spacecraft depart Earth for elliptical Mars orbit in early 1984. The spacecraft would spend 200 days at Mars, 250 days at Venus, and 639 days between planets, for a total mission duration of 1089 days (a little less than three years). Total propulsive effort would amount to 9.339 kps.

The seventh and last opportunity of the 6.4-year cycle would occur in mid-1985. The dual-stopover spacecraft would spend 767 days in elliptical Venus orbit before voyaging to Mars for a 78-day stopover. It would spend 599 days between worlds - the shortest travel time of the seven opportunities. The long Venus stopover would, however, result in a mission duration of 1444 days (about four years), making it the lengthiest of the seven dual-stopover missions. Total propulsive effort would amount to 9.321 kps.

The 6.4-year-cycle Willis and Padrutt studied in detail would end just before the first dual-stopover opportunity of the next 6.4-year cycle. That opportunity, very similar to the late 1979 Earth-Mars-Venus-Earth opportunity, would occur in the first half of 1986.

Willis and Padrutt compared the total propulsive effort necessary to accomplish four of the dual-stopover missions in the 1979-1986 period with that needed to carry out four Mars stopover/Venus swingby missions. They sought to reduce dual-stopover mission duration, however, so permitted increased propulsive effort. This would enable shorter stays at planets and shorter transfers between planets. The Mars stopover/Venus swingby missions - all of which would include a 30-day Mars stopover - were assumed to leave Earth on approximately the same dates as the dual-stopover missions.

They found that the first dual-stopover mission, the December 1979 Earth-Mars-Venus-Earth mission, would need a total propulsive effort of about 13 kps to reduce its duration to 700 days. A Mars stopover/Venus swingby mission launched at about the same time could be performed in 700 days with a total propulsive effort of only eight kps. The same missions could be carried out in 575 days with propulsive efforts of 20 kps and a little less than 11 kps, respectively. These numbers indicated that the first opportunity in the 6.4-year dual-stopover cycle was not a favorable one for dual-stopover missions of reduced duration.

Dual-stopover missions launched in the other three opportunities compared more favorably with Mars stopover/Venus swingby missions. The fourth mission of the 1980s dual-stopover cycle - another Earth-Mars-Venus-Earth mission - could be shortened to 700 days if a total propulsive effort of about 12 kps were permitted, while a 700-day Mars stopover/Venus swingby mission departing Earth at about the same time would need a propulsive effort of about 10 kps.

The sixth dual-stopover mission (Earth-Mars-Venus-Earth) could be accomplished in just 625 days with a total propulsive effort of a little more than 10 kps. Willis and Padrutt calculated that a 625-day Mars stopover/Venus swingby mission launched at the same time would actually need a greater total propulsive effort: a little less than 12 kps.

The seventh dual-stopover mission in the cycle - an Earth-Venus-Mars-Earth mission - could be shortened to 675 days with a total velocity change of about 10 kps. A 675-day Venus swingby/Mars stopover mission launched at the same time would need a velocity change of eight kps.

Willis and Padrutt conceded that the minimum propulsive effort required to carry out a dual-stopover mission would almost always exceed that of a single mission that traveled from Earth to either Venus or Mars and back to Earth. They noted, however, that the minimum propulsive effort of a separately launched Earth-Venus-Earth stopover mission and a separately launched Earth-Mars-Earth stopover mission combined would always exceed that of a single dual-stopover mission. The two separate missions would together need a minimum propulsive effort of at least 17 kps; that is, nearly double the minimum propulsive effort of a typical dual-stopover mission.

Sources

Round Trip Trajectories With Stopovers At Both Mars and Venus, NASA TM X-52680, E. Willis and J. Padrutt, NASA Lewis Research Center, September 1969

Planetary Exploration Utilizing a Manned Flight System, NASA Office of Manned Space Flight, 3 October 1966

More Information

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

NASA Marshall's 1966 NERVA-Electric Piloted Mars Mission

To Mars by Way of Eros (1966)

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

Humans on Mars in 1995! (1980-1981)

Footsteps to Mars (1993)

14 April 2017

Geosynchronous Drift: Krafft Ehricke's Destination Mankind Apollo Mission (1972)

Apollo 17 launch, 7 December 1972. Image credit: NASA
In May 1972, Krafft Ehricke, Executive Advisor in the Space Division of North American Rockwell Corporation, proposed that the last piloted lunar landing mission, Apollo 17, scheduled for the end of 1972, be postponed until the U.S. Bicentennial in July 1976 and dispatched to a new destination: a geosynchronous orbit (GSO) 22,300 miles above the Earth. An object in a GSO requires one day to complete one revolution of the Earth. Since Earth revolves in one day, an object in equatorial GSO appears to hang over one spot on the equator.

"The mission into geosynchronous orbit," Ehricke declared, would provide "additional return on America's investment in Apollo" by dramatizing "the usefulness of manned orbital activities." He added that his proposal, which he dubbed Destination Mankind, "would inspire many, as did the lunar missions before it, but in a different, perhaps more direct manner, because of its greater relevance to some of the most pressing problems of our time."

Ehricke's emphasis on practical benefits over lunar exploration reflected a significant shift in the public perception of spaceflight - one which had gained momentum throughout the 1960s. President Richard Nixon had articulated this shift in his "Statement About the Future of the United States Space Program" on 7 March 1970. The 37th President stated that he believed that the U.S. space program should proceed at a measured pace (not on "a crash timetable") and should be devoted to scientific exploration (mainly using interplanetary robots, but with man on Mars as a "longer-range goal").

In addition, NASA should emphasize international cooperation, cost reduction, and, crucially, "practical application - turning the lessons we learned in space to the early benefit of life on Earth." Nixon declared that results of space research should be "used to the maximum advantage of the human community." He listed among the practical applications of spaceflight "surveying crops, locating mineral deposits, and measuring water resources."

Ehricke described a representative 12-day Destination Mankind mission. Reaching GSO would require about as much propulsive energy as reaching lunar orbit, he noted. The three-stage Destination Mankind Apollo Saturn V rocket would lift off from Launch Complex 39 at Kennedy Space Center, Florida, at about 8:30 p.m. local time. Following first and second stage operation, the S-IVB third stage would fire briefly to place itself, the Apollo Command and Service Module (CSM), and a Payload Module (PM) into 100-nautical-mile parking orbit. Ehricke did not describe the PM design.

One orbital revolution (about 90 minutes) later, the S-IVB would ignite again to perform Transynchronous Injection (TSI). After S-IVB shutdown, the astronauts would separate their CSM and turn it 180° to dock with the PM, which would be attached to the top of the S-IVB in place of the Apollo Lunar Module (LM). They would then extract the PM, maneuver away from the S-IVB, and settle in for the 5.2-hour coast to GSO.

Deep Space Climate Observatory (DSCOVR) image of Africa, the Middle East, India, Europe, and adjacent seas and oceans. Cairo, close to the northern limit of the Destination Mankind Afro-Eurasian Station, is located near the center of the image. DSCOVR images Earth every two hours from Sun-Earth L1, not from geosynchronous orbit. Image credit: NASA
The Destination Mankind CSM would ignite its Service Propulsion System (SPS) main engine to enter a GSO at 31° east longitude. This would place it over the equatorial nation of Uganda - if the CSM entered an equatorial GSO. The mission's GSO would, however, be inclined 28.5° relative to Earth's equator, so the CSM would oscillate between 28.5° south latitude (over South Africa's east coast) and 28.5° north latitude (southwest of Cairo) and back every 24 hours. The CSM would reach its southern limit at 10 a.m. local time and its northern limit at 10 p.m. local time. This 57°-long stretch of the 31° east longitude line would, Ehricke explained, constitute Destination Mankind's "Afro-Eurasian Station."

Destination Mankind mission objectives would fall into three general areas: science, technology, and public relations. Science objectives would draw upon an Apollo Geosynchronous Scientific Experiment Package (AGSEP) carried in the PM. The crew might assess the astronomical value of a GSO observatory, perform high-energy particle experiments, and observe and image the Earth. At the Afro-Eurasian Station, the astronauts could view Africa, Europe, the Middle East, Central Asia, and India. Earth imaging and observation might be conducted in collaboration with observers at "ground truth" sites on land and on ships at sea.

Ehricke emphasized the technology objectives of his Destination Mankind mission. He was particularly enamored of a solar illumination experiment that would see a circular reflector assembled by spacewalking astronauts. The experiment would provide reference data for design and operation of future space-based reflectors, he explained. He calculated that a 100-meter reflector in GSO could light Earth's surface one-tenth as brightly as a full moon in a selected area. This level of illumination, though "subvisual," would be useful for night meteorology and surveillance of border and coastal areas, Ehricke wrote.

The astronauts would also erect "Manstar," a 500-to-700-foot-diameter reflective balloon visible over a wide area of Earth's surface as a modestly bright star. Ehricke called Manstar "a visible manifestation for all mankind of the potential value of space."

Ehricke called public relations "Public Exposure." Destination Mankind astronauts would become television stars. They would describe their Earth observations - "especially aspects useful and of interest to regional populations" - via TV broadcasts from GSO. Their spacewalks would also make for good TV fare, Ehricke judged.

Apollo 17 Command Module Pilot Ronald Evans retrieves film and data cassettes from the Scientific Instrument Module Bay built into the side of the Apollo 17 CSM America. Evans' 17 December 1972 spacewalk was the last performed beyond low-Earth orbit. Ehricke's Destination Mankind mission would have included several spacewalks in GSO, where none has yet occurred. Image credit: NASA
DSCOVR image of North America, South America, and Central America with adjacent oceans and seas. New Orleans, near the northern limit of the Destination Mankind Panamerican-Pacific Station, is located near the center of the image. Image credit: NASA
The Destination Mankind CSM and PM would remain at the Afro-Eurasian Station for an unspecified period (perhaps two days), then the astronauts would fire the CSM's SPS to climb to a slightly higher orbit and begin a two-day "drift" westward across the Atlantic to their Panamerican-Pacific Station. Upon reaching their new station, located at 90° west longitude, the crew would fire the SPS to lower their orbit and halt their drift.

The CSM and PM would oscillate between 28.5° south (over the Pacific off northern Chile) and 28.5° north (over the Gulf of Mexico south of New Orleans), again reaching the southern limit at 10 a.m. local time and the northern limit at 10 p.m. local time. Equatorial crossing would occur above the Galapagos Islands. The astronauts would spend their time much as they did at the Afro-Eurasian Station, then would fire the SPS again to drift westward across the Pacific.

DSCOVR image of Australia, east Asia, east Africa, the Middle East, India, and adjacent bodies of water. The Destination Mankind Australo-Asian Station's southern limit would occur over the Indian Ocean off the coast of Perth, Australia, in the lower half of the image, just right of center. Image credit: NASA
The last stop on the Destination Mankind crew's world tour would be the 98° east longitude line, which Ehricke dubbed the Australo-Asian Station. They would reach the north point in their south-north oscillation over southern China and the south point over the east Indian Ocean west of Perth. Near the end of their stay at the Australo-Asian Station, they would discard the PM.

The Destination Mankind crew would return to Earth from the Australo-Asian Station. Using the SPS, they would perform a Trans-Earth Injection burn as their CSM crossed the equator near Sumatra moving north at 4 p.m. local time. Fall to Earth would last 5.2 hours, and splashdown would occur in the Pacific west of Hawaii at just after 6 a.m. local time.

Sources

"Destination Mankind: Proposal for a Saturn V - Apollo Mission into Geosynchronous Orbit," K. Ehricke, North American Rockwell, 10 May 1972

The American Presidency Project, "Statement About the Future of the United States Space Program," Richard Nixon, 7 March 1970 - http://www.presidency.ucsb.edu/ws/index.php?pid=2903&st=Future+of+the+United+States+Space+Program&st1= (Accessed 14 April 2017)

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