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

Wernher von Braun in his office at NASA Marshall Space Flight Center. Image credit: NASA.

At the 7th International Astronautical Congress, held in Rome in September 1956, Italian aviation and rocketry pioneer Gaetano Crocco described a piloted space mission in which a spacecraft would conduct a reconnaissance flyby of Mars, swing past Venus to bend its course toward Earth, and, one year to the day after departing Earth orbit, reenter Earth's atmosphere. After Earth-orbit departure, the spacecraft would need no additional propulsion. Crocco told the assembled delegates that an opportunity to commence such a mission would next occur in June 1971.

A little less than six years later, in May 1962, the Future Projects Office (FPO) at NASA's Marshall Space Flight Center (MSFC) in Huntsville, Alabama, awarded manned Mars mission study contracts worth $250,000 each to General Dynamics, Lockheed, and the Aeronutronic Division of Ford Motor Company. General Dynamics was instructed to study Mars orbital missions, Lockheed to look at Mars flyby and orbital missions, and Aeronutronic to study dual-planet (Mars-Venus) flybys. The combined study effort was known as EMPIRE, an evocative (if somewhat tortured) acronym that stood for Early Manned Planetary-Interplanetary Roundtrip Expeditions.

EMPIRE took place against the backdrop of the Apollo lunar program. One year before its start, in a speech before a special joint session of Congress, President John F. Kennedy had put NASA on course for the Moon. He had given the U.S. civilian space agency, which had been founded less three years earlier, until the end of the 1960s to achieve his goal. It was hoped, however, that an American could land on the Moon as early as 1967, during Kennedy's second term in office.

As EMPIRE began, NASA had nearly completed the contentious 14-month process of choosing the fastest, most reliable, and cheapest way of placing men on the Moon. The Lunar Orbit Rendezvous mode, which would rely on MSFC's Saturn C-5 rocket, was selected in July 1962, before EMPIRE reached its conclusion. C-5 was soon renamed Saturn V.

MSFC was fertile ground for NASA's first major manned planetary mission study. The Huntsville Center's director was Wernher von Braun, a famous advocate of piloted flight to the Moon and Mars. Von Braun's efforts in the 1950s to popularize spaceflight had helped to prime the American public for the 1960s Space Race with the Soviet Union.

EMPIRE was, however, not merely the whim of a long-time Moon and Mars fan; it was also part of a strategy to protect and promote MSFC. The Huntsville Center's specialty was rocket development. Its engineers hoped to develop rockets larger than the Saturn V, which they dubbed Nova and Supernova. Von Braun knew that, unless a post-Apollo program was in place as MSFC's Apollo responsibilities wound down in 1966 and 1967, his center would suffer deep staff and funding cuts, not develop new big rockets.

The Saturn family of rockets was expected to lead to larger Nova and Supernova rockets by the end of the 1960s. In the illustration above, dating from early 1962, the three-stage C-1 and four-stage C-5 are anemic predecessors to the Apollo Saturn IB and Saturn V designs. The Apollo-Saturn rockets later adopted features of the proposed (but never flown) Nova depicted; in particular, the Nova rocket's 22-foot-diameter third stage. Image credit: NASA.

Besides calling for a man on the Moon, President Kennedy's May 1961 speech had requested new funding for nuclear propulsion. MSFC was involved in joint NASA/Atomic Energy Commission (AEC) nuclear rocket development through the Reactor In Flight Test (RIFT) program. The precise form the RIFT mission would take changed rapidly; for a time, it aimed to launch a 33-foot-diameter rocket stage with a NERVA nuclear engine on a Saturn V in 1967. Another goal of EMPIRE was, thus, to create a justification for NERVA and RIFT.

In the introduction to their December 1962 EMPIRE final report, Aeronutronic's engineers praised NASA for its "forward thinking approach." They added that

[b]y attacking the areas of interest at this early date[,] it will be possible to obtain a clearer picture of the requirements for early manned planetary and interplanetary flight. Thus the nation's resources, and the NASA and other United States space programs[,] can be oriented toward long range goals at an early date. [EMPIRE] represents an unusually early attack on this type of analysis.

Aeronutronic looked at two interplanetary trajectories for its dual-planet piloted flyby mission. The first was dubbed the Crocco trajectory because it was based on the scenario in Crocco's 1956 paper. The second was the symmetric trajectory, which would see the flyby spacecraft swing around the Sun one-and-a-half times. It would fly past Mars halfway through its mission and would cross the orbit of Venus once before the Mars flyby and once after. It would swing past Venus during one of the orbit crossings.

Interplanetary trajectory types Ford Aeronutronic considered for its Mars/Venus flyby mission. Image credit: Ford Aeronutronic/NASA.

Aeronutronic engineers found that Crocco had been mistaken when he wrote that an opportunity to start an Earth-Mars-Venus-Earth voyage would occur in June 1971. They determined that a dual-planet Crocco mission could depart Earth in mid-to-late August 1971. A symmetric Earth-departure opportunity would occur sooner: between 16 July and 19 August 1970.

The Crocco trajectory would require more propulsive energy than the symmetric trajectory, Aeronutronic found. The amount of energy required would depend on the moment during the launch opportunity that the spacecraft left Earth orbit. Aeronutronic, however, selected single representative values for preliminary design purposes.

Assuming a departure from a 300-kilometer-high circular Earth orbit, a Crocco spacecraft launched in August 1971 would need to increase its speed by 11.95 kilometers per second to achieve the desired dual-planet flyby trajectory. A symmetric mission launched in the July-August 1970 window would, by contrast, need a velocity increase of only 5.3 kilometers per second.

Low departure velocity meant reduced propellant requirements. In short, a symmetric mission would have a much lower mass than a Crocco mission. A low-mass spacecraft would need fewer launches to place its components and propellants into Earth orbit. Fewer launches would mean lower mission cost and less chance that a launch vehicle would fail and destroy its payload, perhaps placing the assembly campaign in Earth orbit in jeopardy. It would also mean less complex orbital assembly (or perhaps no assembly at all, if a Nova rocket were used), further trimming mission risk.

Aeronutronic found that no dual-planet Crocco mission could last only 365 days; for design purposes, the study team assumed that a mission launched in the August 1971 opportunity would last 396 days. Though longer than Crocco had estimated, this was much less than the 611-day representative duration Aeronutronic selected for the July-August 1970 symmetric opportunity.

Aeronutronic's engineers determined that radiation and meteoroid shielding and life support masses, which would increase with trip time, would not approach the mass of the propellant required to launch the Crocco mission out of Earth orbit; they thus accepted the symmetric mission's greater duration.

The symmetric mission would have a low Earth-departure speed, but would pay for it by having a high Earth-atmosphere reentry speed. As a general rule, the faster a spacecraft is moving as it plummets into Earth's atmosphere, the more reentry heating it will undergo. Greater heating calls for more massive thermal control systems; basically, active cooling employing coolant loops and radiators and a thick heat shield that ablates (that is, chars and erodes away, carrying away heat). The re-entering spacecraft might also use a braking rocket to slow itself before reentry.

The Aeronutronic engineers did not consider the difference between the Crocco and symmetric Earth-atmosphere reentry speeds to be significant. For a symmetric mission launched between 16 July and 19 August 1970, reentry speed would top out at 15.8 kilometers per second; the corresponding figure for the August 1971 Crocco opportunity was 13.5 kilometers per second. The propellant mass and Earth-to-orbit launch vehicles saved as a result of the Crocco mission's somewhat slower Earth atmosphere-reentry speed were minimal compared with the mass and launchers saved by the symmetric mission's dramatically reduced Earth-departure velocity.

Dual-planet flyby spacecraft size comparisons. Note comparison with Mercury-Atlas rocket and spacecraft (lower right). Mercury was the only piloted U.S. spacecraft that had flown at the time Ford Aeronutronic completed its study. Image credit: Ford Aeronutronic/NASA.

Aeronutronic calculated that, based on the mission design values that it had selected, the nuclear Crocco dual-planet flyby spacecraft would have a fully assembled, fully fueled mass of 1121.5 tons, while an equivalent nuclear symmetric spacecraft would have a mass of only 188 tons. This would place the latter within the planned payload capacity of a single Nova rocket, eliminating Earth-orbit assembly entirely.

The Aeronutronic engineers did not bother to determine the mass of a chemical Crocco spacecraft because they knew that it would be even greater than that of the nuclear Crocco spacecraft. They calculated, however, that the chemical symmetric spacecraft would have a mass of 350.5 tons (nearly twice that of the nuclear symmetric spacecraft) or 929.5 tons (nearly as much as the nuclear Crocco spacecraft) depending on the thrust capability of its rocket motor. The company thus selected the nuclear symmetric mission for more detailed study.

Aeronutronic envisioned a 156-foot-long, 33-foot-wide symmetric dual-planet flyby spacecraft with a single 18,300-pound NERVA engine capable of generating 50,000 pounds of thrust. A tungsten shield at the front of the drum-shaped NERVA reactor would create a radiation shadow that would encompass the crew modules during Earth-orbit departure.

The engine would need to operate for nearly 48 minutes to boost the spacecraft's speed by 5.3 kilometers per second and place it onto its symmetric trajectory. Aeronutronic identified the lengthy burn time as a possible show-stopper; available reactor materials, it explained, could not withstand such prolonged operation. Increasing thrust would reduce required burn time, but the company was not confident that a nuclear engine with more than 50,000 pounds of thrust could be developed in time for the July-August 1970 symmetric launch opportunity.

The nuclear symmetric spacecraft became Ford Aeronutronic's dual-planet flyby mission baseline design. Image credit: Ford Aeronutronic/NASA.

Two tank clusters would supply liquid hydrogen propellant to the NERVA engine. The first-stage cluster, which would contain 56.2 tons of propellant, would comprise a core propellant tank to which the NERVA engine would be mounted and six detachable "perimeter" tanks. After expending the first-stage propellant and discarding the perimeter tanks, the spacecraft would have a mass of 127.7 tons.

Eight second-stage tanks would then supply a total of 38.3 tons of liquid hydrogen to the NERVA engine. After it expended its second-stage propellant, the NERVA engine would detach along with the empty first-stage core tank.

The empty second-stage tanks, with a total mass of 5.2 tons, would be retained to shield the Aeronutronic flyby spacecraft's cylindrical central core from meteoroids. After NERVA engine/first-stage propellant separation, the spacecraft would have a mass of 76.7 tons and would measure about 78 feet long.

From aft to front, the core would comprise twin SNAP-8 nuclear reactors for generating electricity, the spacecraft's navigational stable platform, a small compartment for weightless experimentation, and a 20-ton command center/solar flare radiation shelter clad in 50 centimeters of polyethylene plastic. Four tanks containing a total of 10.9 tons of chemical trajectory-correction propellants would surround the command center/shelter, providing additional radiation shielding. A two-stage reentry braking propulsion module ("retro-pack") and the Earth-atmosphere reentry vehicle would be attached to the command center/shelter at the front of the spacecraft.

Earth-orbit departure completed, the six-man crew would reconfigure their spacecraft for the interplanetary voyage. The twin cylindrical living modules, each with an empty mass of 4.5 tons, would extend on hollow telescoping arms, and one SNAP-8 would deploy a radiator panel and begin generating electricity (the other would be held in reserve in case the first failed).

The crew would then spin their spacecraft about its long axis at a rate of three revolutions per minute to create acceleration in the living modules which they would feel as gravity. Sixteen-meter-diameter dish antennas would unfurl from the aft end of both living modules to ensure continuous radio communication with Earth. Aeronutronic noted that, when the spacecraft was farthest from Earth, one-way radio-signal trip time would reach 22 minutes.

The nuclear symmetric spacecraft would undergo configuration changes as it carried out its mission, casting off parts that were no longer useful and deploying power, communications, and artificial-gravity systems. The spacecraft would spend most of the flight in the configuration labeled "on-orbit spacecraft." Please click on image to enlarge. Image credit: Ford Aeronutronic/NASA.

Based on experience with nuclear submarine crews, Aeronutronic allocated 750 cubic feet of living space to each astronaut, except inside the command center/radiation shelter, where it judged that 50 cubic feet per man would suffice. The twin living modules and command center/shelter would each have an independent life support system designed to recycle all air and water. The company estimated that life support mass would total 10.9 tons, of which food would make up nearly five tons.

The six-man crew would follow a complex schedule designed to combat boredom while providing adequate rest and recreation. Except for sleep, crew activities would occur in two-hour blocks. The crew would include a Commanding Officer, an Executive Officer, a Flight Surgeon, and three astronauts identified simply as "crew members." All six would take it in turns to serve as duty officer in the command center/shelter, maintenance and repair crewmember, and scientific activity crewmember. The Commanding Officer and Flight Surgeon would not, however, take part in hazardous repairs (for example, those involving spacewalks).

Symmetric Mars-Venus piloted flyby trajectory: 1 = Earth launch; 2 = Venus orbit crossing (possible flyby); 2* = second Venus orbit crossing (possible flyby); 3 = Mars orbit crossing; 3* = second Mars orbit crossing; 4 = Mars flyby/Earth position during Mars flyby; 5 = Earth return. Image credit: Ford Aeronutronic/NASA.

A symmetric dual-planet flyby mission departing Earth in the 16 July-19 August 1970 opportunity would fly first past Venus between 97 and 102 days after launch from Earth orbit. Departure at the start of the launch opportunity would yield the shortest trip time on each leg of the interplanetary voyage (and shortest total trip time — 611 days); departure at the end of the opportunity would yield the longest trip time on each leg (and longest total — 631 days). Earth-departure near the start of the opportunity would yield a Venus flyby distance of about 4890 miles; the corresponding figure for the end of the opportunity would be 7520 miles.

As the spacecraft approached Venus, the crew would fire the trajectory-correction motors, changing their speed by about 650 feet per second to ensure an on-target flyby. The spacecraft would carry enough course-correction propellants to change its velocity by a total of 2000 feet per second.

Citing a November 1961 report planetary astronomer Gérard de Vaucouleurs had prepared for the U.S. Air Force, Aeronutronic allotted 1000 pounds for scientific equipment for studying Venus and Mars. The company declined, however, to define a scientific payload for its spacecraft, arguing that the EMPIRE mission's science objectives at Mars and Venus would be shaped by data from NASA robotic spacecraft launched between 1962 and 1968.

The Mars flyby would occur between 191 and 199 days after the Venus flyby, at the midpoint of the symmetric mission. During Mars approach, the crew would perform a second trajectory-correction burn, changing their spacecraft's speed by 330 feet per second. Mars flyby distance would range from about 2740 miles for an Earth departure at the beginning of the July-August 1970 opportunity to 4220 miles for a departure at its end.

An EMPIRE ground rule was that the contractors should use Apollo hardware and techniques wherever feasible, though this was not strictly enforced. The conical Apollo Command Module (CM) with its bowl-shaped ablative heat shield was considered a prime candidate for use as EMPIRE's Earth-reentry vehicle, but Aeronutronic rejected it.

The company opted instead for a 14.75-ton lifting-body with a pointed nose and a two-stage chemical-propellant retro-pack. Aeronutronic had determined that the lifting-body shape was more tolerant of reentry errors — that is, that it would be less likely to burn up or skip off the atmosphere — than the Apollo capsule. The lifting-body would, Aeronutronic noted, also offer a broader choice of land landing or sea splashdown sites because of its enhanced ability to maneuver in the atmosphere.

Ford Aeronutronic's preferred Earth-return reentry vehicle configuration. Image credit: Ford Aeronutronic/NASA.

Landing/splashdown site flexibility would become especially useful if an abort during Earth departure became necessary. Aeronutronic found that the retro-pack, intended to slow the reentry vehicle as it neared Earth at the end of the mission, could return the crew to Earth no later than 16.7 hours after Earth-orbital launch provided that an abort was initiated before the flyby spacecraft passed beyond about 12,000 miles from Earth.

If, however, the mission unfolded as planned, the astronauts would return to Earth between 312 and 343 days after passing Mars. Prior to reentry, they would perform the final trajectory-correction burn of the mission, changing their spacecraft's speed by about 360 feet per second. Shortly thereafter, the astronauts would strap into the Earth-reentry lifting-body and fire small solid-propellant rocket motors to separate it from the flyby spacecraft. The abandoned flyby spacecraft would subsequently swing past Earth and enter a disposal orbit around the Sun.

After properly orienting the Earth-reentry vehicle, the crew would ignite the two stages of its nose-mounted retro-pack in succession, steering the lifting-body toward its reentry corridor and reducing its reentry velocity by 2.8 kilometers per second to 13 kilometers per second. The stages would detach in turn as they expended their propellants.

During reentry, the hottest part of the vehicle would be its small pointed nose, which Aeronutronic expected would be actively cooled to prevent melting. A blowtorch-like plume of superheated plasma would trail from the nose beneath the lifting-body, but would not contact its concave underside.

The astronauts, who would recline facing away from the nose, would experience deceleration equal to 10 Earth gravities, which they would feel against their backs. After deceleration and descent into the lower atmosphere, the lifting-body would deploy parachutes and descend more or less vertically.

Aeronutronic provided a detailed development schedule and cost estimate for its nuclear symmetric dual-planet flyby mission. The company placed the mission's cost at $12.6 billion, or about half the projected Apollo Program cost. Cost savings would be due in large part to experience gained and hardware developed during Apollo. Peak funding year, with expenditures totaling about $3.5 billion, would be 1966.

Aeronutronic estimated that development of a 50,000-pound-thrust NERVA engine capable operating continuously for 60 minutes would need to begin on 1 January 1963 (that is, 10 days after the company completed its final report for MSFC FPO), as would development of the Earth-reentry lifting body. NERVA engines would be tested at the Nuclear Rocket Development Station (NRDS) at Jackass Flats, Nevada, beginning in mid 1965. Earth-reentry vehicles would be drop-tested over the dry lake bed at Edwards Air Force Base in California beginning in mid-1966 and would be flight-tested with and without a crew using Saturn C-1 boosters beginning a year after that.

Flyby spacecraft development would begin in early 1964, shortly before crew selection and the start of Nova development. Beginning in mid-1967, Saturn C-5 rockets would launch three symmetric dual-planet flyby spacecraft without Earth-reentry vehicles into Earth orbit for testing.

A total of 13 Nova rockets would be required for ground and flight testing between mid-1966 and late 1969. Of these, the first four would be Nova development flights and the last three would launch complete manned symmetric dual-planet flyby spacecraft into Earth orbit for testing and crew training. The fourteenth Nova, designated N9, would launch the mission spacecraft and crew into 300-kilometer-high Earth orbit on 15 July 1970, the day before the symmetric launch opportunity was set to begin.

In a paper presented 10 months after Ford Aeronutronic delivered its final report to MSFC FPO, Franklin Dixon declared that development of an improved NERVA engine should have begun no later than July 1963 if it was to become available in time for the 16 July-19 August 1970 symmetric dual-planet flyby launch opportunity. Dixon had not participated in EMPIRE; on 1 July 1963, Ford had placed Aeronutronic under its Philco division, and Dixon had become Philco Aeronutronic's Manager for Advanced Space Systems.

Cutaway illustration of NERVA nuclear-thermal rocket engine. Image credit: NASA.

NERVA development lagged behind the schedule Dixon said was necessary in part because of Kiwi-B nuclear rocket engine failures in December 1961, September 1962, and November 1962. As the name implies, the Kiwi series engines were not meant for flight. In fact, though they each included a nozzle and blasted super-hot hydrogen gas into the air, they were considered nuclear reactors, not nuclear rocket engines. 

The three failures were similar in nature: liquid hydrogen moving through the hot reactor core caused vibration which broke and eroded the reactor's uranium fuel rods. Hot gaseous hydrogen exhaust then blew uranium fragments out through the engine nozzle. The melting fragments sparkled as they sprayed into the open air.

The Kiwi-B failures set off a duel between the President's Science Advisory Council and the Bureau of the Budget on the one hand and NASA and the Atomic Energy Commission, championed by New Mexico Senator Clinton Anderson, on the other. Democrat Anderson's state contained Los Alamos National Laboratory, which led the AEC side of the nuclear rocket program.

President Kennedy visited the NRDS in early December 1962 to size up the situation. On 12 December 1962, two weeks before Ford Aeronutronic completed its EMPIRE study, he indefinitely postponed RIFT. Citing fiscal restraint, Kennedy's successor, Lyndon Johnson, cancelled RIFT altogether in December 1963, and made NERVA a wholly ground-based research and development effort.

In December 1967, the NRX-A6 NERVA ground-test engine operated for 60 minutes without a hitch; that is, for longer than would have been required to boost Aeronutronic's dual-planet flyby spacecraft out of Earth orbit and onto its symmetric trajectory. Nevertheless, President Richard Nixon cancelled NERVA in 1972 after program expenditures totaling $1.4 billion.

The Nova rocket experienced a less protracted and costly demise. By June 1964, von Braun called publicly for piloted planetary flyby missions using Saturn V rockets and Apollo-derived hardware, thus acknowledging that the Lunar Orbit Rendezvous decision of July 1962 had all but doomed large rockets like Nova.

Later in 1964, the Bureau of the Budget declared Nova rocket development to be of low priority, and called for NASA's post-Apollo program to be confined to Earth orbit and based on hardware developed for Apollo. The MSFC FPO would publish a feasibility study of an Apollo-derived piloted flyby mission in early 1965.

Sources

EMPIRE: A Study of Early Manned Interplanetary Expeditions, NASA Contractor Report 51709, Aeronutronic Division, Ford Motor Company, 21 December 1962.

"The EMPIRE Dual Planet Flyby Mission," Franklin P. Dixon, Aeronutronic Division, Philco Corporation; paper presented at the Engineering Problems of Manned Interplanetary Exploration conference, 30 September-1 October 1963.

"EMPIRE: Early Manned Planetary-Interplanetary Roundtrip Expeditions Part I: Aeronutronic and General Dynamics Studies," Frederick I. Ordway III, Mitchell R. Sharpe, and Ronald C. Wakeford, Journal of the British Interplanetary Society, May 1993, pp. 179-190.

More Information

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)

Flyby's Last Gasp: North American Rockwell's S-IIB Interplanetary Booster (1968)

McDonnell Douglas Phase B Space Station (1970)

Image credit: MDAC/NASA.

In the autumn of 1966, NASA asked President Lyndon Baines Johnson's Bureau of the Budget (BOB) for $100 million in Fiscal Year (FY) 1968 to begin Phase B contractor studies of Earth-orbital space stations. With the Apollo Program's culmination drawing near, the U.S. civilian space agency was eager to establish post-Apollo goals, and topping its wish-list was a space station — an Earth-orbiting laboratory for testing the effects on men and machines of long-term exposure to space conditions and for performing scientific and technological experiments and Earth and space observations.

NASA had performed internal Phase A space station studies almost since it opened its doors in October 1958. If NASA had had its way, a space station would have preceded Apollo's reach for the Moon. President John F. Kennedy's May 1961 call for a man on the Moon ahead of the Russians and before the end of the 1960s had, however, preempted space station development. The FY 1968 funding request was in some sense a plea to restore NASA's program to the traditional station/Moon/Mars progression spaceflight thinkers had promoted since the 1920s.

The BOB turned down NASA's request: then, in January 1967, the Apollo 1 fire profoundly altered the space policy environment. NASA came under increased scrutiny and funding for post-Apollo space goals became even more elusive. Congress dealt the only approved post-Apollo manned program — the Apollo Applications Program (AAP), which would re-apply Apollo lunar mission hardware to new goals, including a series of Earth-orbiting laboratories based on spent Saturn IB S-IVB rocket stages — a nearly half-billion dollar funding cut in August 1967.

NASA recovered from the fire — in November 1967, the successful first flight of the three-stage Saturn V Moon rocket did much to restore confidence — but funding for post-Apollo programs was still not forthcoming. When NASA Administrator James Webb, who had led the agency from Apollo's beginning, announced in September 1968 that he would step down, he told journalists that he left NASA "well prepared. . .to carry out missions that have been approved." He added, however, that "[w]hat we have not been able to do under pressures on the budget has been to fund new missions."

After he stepped down, Webb's new deputy, Thomas Paine, became acting NASA Administrator. Webb, whose earliest Federal government experience dated to 1932, had deftly piloted NASA through Washington's political shoals; Paine, by contrast, had just seven months of experience in government service when he took over as NASA boss. Paine displayed his inexperience almost immediately by pressing President Johnson for a space station decision in the final weeks of his Administration. Johnson deferred the decision to the next President.

Soon after President Richard M. Nixon's January 1969 inauguration, Democrat Paine submitted his resignation as was customary. Republican Nixon, however, surprised everyone by keeping him on and appointing him as Webb's formal replacement. Paine then made another space station pitch. He apparently hoped that Apollo Program successes would induce the new President to give NASA a blank check for future projects.

5 March 1969: standing in front of a bust of U.S. rocket pioneer Robert Goddard, President Richard Nixon (left) announces that he has appointed Thomas Paine (center) to be NASA Administrator as Vice President Spiro Agnew looks on. The Senate would confirm Paine on 20 March. Image credit: NASA.

Though the Apollo 8 Command and Service Module (CSM) had triumphantly orbited the Moon and returned its three-man crew safely to Earth less than a month before his inauguration, Nixon refused to commit to new NASA programs. Instead, he postponed any decision on NASA's future direction at least until after the newly appointed Space Task Group (STG) completed its report in September 1969. Paine was a voting member of the STG, which was chaired by Vice President Spiro Agnew.

It is widely assumed today that Nixon kept Paine on in case Apollo failed. In the event that the first Moon landing ended in grief, he wanted a holdover from the Democratic Johnson Administration upon whom he could hang the blame. At the time, however, even as savvy an aerospace trade publication as Aviation Week & Space Technology assumed that Nixon was impressed with Paine's abilities. Nixon, it must be said, was less impressed with the talents of the people with whom he surrounded himself than he was with their obedience.

Paine chose not to await the outcome of the STG's deliberations. In January-February 1969, he oversaw creation within NASA of a Space Station Task Force, a Space Station Steering Group, and an independent Space Station Review Group. These bodies prepared a Phase B Space Station Study Statement of Work (SOW), which NASA released to industry on 19 April 1969.

The SOW solicited proposals to study a 12-man Space Station, the design of which would eventually serve as a building block for a 100-man Earth-orbital Space Base. The 12-man Station was to reach orbit on a Saturn V rocket in 1975 and to remain in operation for 10 years.

Of the contractor effort expended in the Phase B study, 60% was to be devoted to the 12-man Space Station, 15% to its future role as part of the 100-man Space Base, 15% to an interim logistics spacecraft for delivering early crews and supplies to the 12-man Space Station, and 10% to 12-man Space Station interfaces with an advanced logistics system (specifically, a fully reusable Space Shuttle, design to be determined).

Grumman, North American Rockwell (NAR), and McDonnell Douglas Aerospace Company (MDAC) submitted proposals in response to the SOW. On 22 July 1969 — two days after the successful Apollo 11 Moon landing — NASA awarded to NAR and MDAC Phase B Space Station study contracts worth $2.9 million each. This was a far cry from the $100 million Webb had sought in late 1966 to fund Phase B Space Station studies.

Phase B study work began formally in September 1969, though the contractors had begun to put together subcontractor teams and to spend their own money on the study even before NASA issued its SOW. The MDAC and NAR Phase B study teams each included more than 30 subcontractors. NAR and MDAC were eager to move forward at their own expense because they expected that the eventual Phase C/D Space Station development contract would be extremely lucrative.

Image credit: NASA.

NASA's Manned Spacecraft Center (MSC) in Houston managed the NAR Phase B study, while Marshall Space Flight Center (MSFC) in Huntsville, Alabama, managed MDAC's work. This division of labor reflected pre-existing center/contractor relationships. MSC managed NAR's contract to manufacture Apollo CSMs, while MSFC managed MDAC's contract to build the 6.6-meter-diameter S-IVB-based AAP Orbital Workshop.

AAP was renamed the Skylab Program in February 1970. The new name reflected AAP's abandonment of all missions not related to the S-IVB-based Orbital Workshop. The two planned Skylab Orbital Workshops were designated Skylab A and Skylab B.

In early June 1970, as the Phase B study effort neared its planned conclusion, NASA and European Space Research Organization (ESRO) officials met in Paris to discuss future cooperation in space with emphasis on the Space Station. Paine and ESRO Director General Hermann Bondi chaired the meeting, during which NAR and MDAC representatives presented briefings on their Phase B study results.

The U.S. Department of State had come out cautiously in favor of NASA's proposed Space Station/Space Shuttle Program in March 1969 because it expected that it would open up opportunities for international cooperation. With that in mind, NASA had invited foreign representatives to participate in Phase B Station study quarterly reviews. The Paris meeting gave ESRO an opportunity to return the favor and to confirm its desire to participate in a NASA-led Space Station Program.

C. J. Dorrenbacher, MDAC's Vice President for Advance Systems and Technology, began his presentation by drawing links between his company's 12-man Space Station design and Skylab A, which he said was scheduled to launch during 1972. The Skylab Program, he told the Paris meeting, would see NASA piloted spaceflight evolve from "cockpit to ship accommodations." He explained that Skylab would contain "many systems that are prototypes of those to be used on the Space Station," and added that "experience in the operation, maintenance, and habitability of [Skylab] will significantly extend our knowledge and, thus, our confidence in the Space Station Program."

Cross-section of MDAC's Phase B 12-man Space Station in launch configuration. Black triangular structures located midway along the Station's length are twin Isotope/Brayton nuclear power units. Image credit: MDAC/NASA.

Like Skylab, MDAC's Space Station would leave Earth on top of a two-stage Saturn V. Designated INT-21, the rocket would comprise S-IC and S-II stages measuring 9.2 meters in diameter. This established the maximum diameter of MDAC's Space Station. The S-II second stage would inject the bullet-shaped 34-meter-long Station into a 456-kilometer-high circular orbit inclined 55° relative to Earth's equator. Its labors completed, the S-II stage would then detach and deorbit itself over a remote ocean area.

Dorrenbacher explained that MDAC's Station would comprise two main modules: the two-deck, roughly conical artificial-gravity module at its front end and the four-deck, drum-shaped core module. The 15-meter-long core module would be divided into two independent sections, each with a research deck and a living deck.

The artificial-gravity module would also include research and living decks. Each of the three sections would have an independent life-support system and could house the entire Station crew in an emergency. The artificial-gravity and core modules would also each include a conical unpressurized module. On the artificial-gravity module, this would be called the equipment module; on the core module, it would be called the power and equipment module.

Soon after reaching orbit, MDAC's Station would discard a streamlined nose cone covering its front docking port. A "telescoping spoke" linking the artificial-gravity and core modules would then extend to separate the two modules by a few meters. This would expose the core module power and equipment module, enabling four large radio dish antennas to deploy and exposing waste heat radiators for the Station's twin Isotope/Brayton (I/B) nuclear power units. The I/B units, which would each produce 10 kilowatts of electricity, would be designed to jettison from the Station in an emergency and safely reenter Earth's atmosphere.

By the time of the Paris briefings, NASA had pushed back the planned launch of the 12-man Space Station from 1975 to 1977. Though the move was inspired by increasingly disheartening NASA budget projections, space agency officials hoped that the two-year slip would also help to ensure that the Space Shuttle would be ready to deliver astronauts, supplies, equipment, and experiment modules to the orbiting Station, eliminating any need to pay for an interim logistics vehicle. For its study, MDAC assumed a Shuttle consisting of a piloted winged Booster and a piloted winged Orbiter with a 4.6-by-18.3-meter cargo bay.

Cross-section of MDAC's Crew/Cargo Module. Image credit: MDAC/NASA.

A Crew/Cargo Module maneuvers from the payload bay of a visiting Space Shuttle Orbiter to an axial docking port on MDAC's Phase B Space Station. Image credit: MDAC/NASA.

Flight controllers on Earth would remotely check out the Station's vital systems. If it checked out as habitable, then 24 hours after it reached orbit its first 12 residents would lift off from Cape Kennedy on board a Shuttle Orbiter. Eight hours later, their Orbiter would rendezvous with the Station and open its cargo bay doors. The Station crew would depart the cargo bay inside an 18,000-kilogram Crew/Cargo Module (CCM).

MDAC's CCM, an independent spacecraft larger than the Apollo CSM, resembled designs for drum-shaped cargo spacecraft and small station modules based on Gemini spacecraft hardware which McDonnell Aircraft had put forward as early as 1962. McDonnell had manufactured the Gemini spacecraft, 10 of which carried two-man crews into Earth orbit in 1965-1966, before the company's April 1967 merger with Douglas Aircraft created MDAC. Probably MDAC viewed the 12-man CCM as a way of salvaging its Gemini-based designs or of saving time and effort during its Phase B study by partially reusing old designs.

The CCM would deploy four side-mounted engine modules and maneuver to a docking at the Station's aft port on the core module. The astronauts would then enter the Station through the port's 1.5-meter hatch (the standard Station hatch size) and begin checking out its systems. If initial Station manning came off without a hitch, the Orbiter, which would remain close by the Station but would not dock, would commence its return to Earth about 25 hours after the CCM bearing the first Station crew left its cargo bay.

A Shuttle Orbiter would deliver a CCM to MDAC's Station every 90 days with a new crew and supplies. Of the CCM's mass, about 13,000 kilograms would comprise cargo. After a new CCM docked at a side port carrying a new crew, the astronauts already on board the Station would board their CCM, undock, maneuver to the waiting Orbiter, and enter its cargo bay. The Orbiter would then hinge shut its cargo bay doors and return to Earth.

Central tunnel of the MDAC Phase B Space Station core module. The CCM docking port is located at the bottom of the bottom, adjacent to Level 1. Image credit: MDAC/NASA.

MDAC Phase B Space Station core module. Image credit: MDAC/NASA.

The hatch through which the first astronauts would enter their new home would lead into the core module's "central tunnel." Besides forming the main "artery" linking the core module's four pressurized decks, the three-meter-diameter cylindrical tunnel would provide emergency living quarters for the entire 12-man crew, a 180-day supply of emergency food, a passageway for ducts and conduits, radiation-shielded photographic film storage, and space suit storage. MDAC thus opted for a "fall-back" shelter where the crew could await rescue in place of a separate Space Station lifeboat that could evacuate the crew in the event of trouble while a Shuttle Orbiter was not present.

At the forward end of the core module tunnel, a hatch would open into a cylindrical airlock at the center of the core module's unpressurized power and equipment module. A hatch in the airlock wall would open into the power and equipment module, which would contain liquid and gas storage tanks, the twin I/B power units and their waste heat radiators, power conditioning and distribution systems, and storage for equipment and supplies able to tolerate vacuum.

A hatch in the airlock ceiling would open into the telescoping spoke linking the core module with the artificial-gravity module. The spoke would link to a hatch leading into the artificial-gravity module's central tunnel, which would provide access to the artificial-gravity module's two decks.

A hatch at the forward end of the tunnel would open into a cylindrical airlock at the center of the artificial-gravity module's unpressurized equipment module. A hatch in the airlock's side would provide access to unpressurized storage, gas and liquid storage tanks, and small thrusters and propellant tanks. The equipment compartment would also include a place for eventual installation of a third I/B power unit. A 1.5-meter hatch in the airlock ceiling would provide access to the MDAC Station's exterior and serve as the Station's front docking port.

Artificial-gravity module. Image credit: MDAC/NASA.

Dorrenbacher told the Paris meeting that the Station's first crew would almost immediately begin a 30-day artificial-gravity experiment. This would entail extending the telescoping spoke to its maximum length. Six crew members would take up residence in the artificial-gravity module, while "some" would occupy a small "zero-gravity cab" inside the spoke at the Station's center of gravity.

The astronauts would then ignite the small thrusters in the artificial-gravity module's equipment module to set the Station spinning end over end at a rate of four rotations per minute. This would produce acceleration which the crew would feel as gravity.

On deck 1 of the core module, 19.2 meters from the center of gravity, the astronauts would feel acceleration equivalent to 0.35 Earth gravities. On the artificial-gravity module's living deck (Deck 6), 39.3 meters from the center of gravity, the astronauts would feel 0.7 Earth gravities.

During the artificial-gravity experiment: MDAC Phase B station with docked CCM (left) and extended artificial-gravity module (right). Image credit: MDAC/NASA.

After a month of artificial-gravity experimentation, the astronauts would halt the Station's rotation using the small thrusters to restore it to a zero-gravity condition. The artificial-gravity module thrusters would carry enough propellants to permit up to four similar experiments.

Dorrenbacher described the 12-man Space Station as "a research facility to accommodate all experiment disciplines. . .a general-purpose laboratory." It would include three lab decks. Deck 2 would at launch from Earth be dedicated to the study of living things in weightlessness. It would include the Station's medical dispensary and isolation ward.

Deck 4 would serve both scientific support and engineering experimentation roles. It would include a drum-shaped experiment and test isolation facility, a mechanical lab, an electronics/electrical lab, a hard-data processing facility, an optics facility, and a small experiment airlock. Deck 5 would include a centrifuge with a pair of cabs large enough to accommodate men and experiments.

Deck 2: the life sciences laboratory. Image credit: MDAC/NASA.

Image credit: MDAC/NASA.

Based on NASA input, MDAC defined eight experiment disciplines for its Phase B Station. These were astronomy, space physics, space biology, Earth survey, aerospace medicine, space manufacturing, engineering/operations, and advanced technology. Not all disciplines could be accommodated simultaneously; for example, the artificial-gravity experiment series would preclude experiments that would need a stable platform and weightlessness.

Dorrenbacher then provided a rough schedule of the Station's experiment programs. Biomedical experimentation would begin with the arrival of of the first crew and continue without pause throughout the Station's planned 10-year lifetime, as would "man-system integration" experiments. In general, early research not associated with the artificial-gravity experiment series would focus on Station operations and habitability. "Component test" experiments would end in early 1978, "maintenance and logistic" experiments would conclude in late 1978, and "occupancy and space living," "contamination," and "exposure" research would end in mid-1979.

CCMs would deliver new experiment apparatus to replace and augment that launched with the Station, Dorrenbacher told the Paris meeting. Disused experiment hardware and other unwanted equipment and furnishings would be packed into CCMs for return to Earth. He suggested that, following the conclusion of artificial-gravity experiments in late 1978, furnishings on Deck 6 should be returned to Earth in CCMs so that it could be converted into a physics & chemistry laboratory using new apparatus delivered in CCMs.

By then, the first Attached Modules (AMs) and Free-Flying Modules (FFMs) would arrive at MDAC's Station in Shuttle Orbiter cargo bays. One AM, devoted to Ultraviolet (UV) Stellar Astronomy, would dock with a port on the core module's side linking it to Deck 4. Another AM, devoted to Earth Surveys, would dock either at Deck 4's second port or at a port on Deck 2.

Two FFMs, devoted respectively to Solar Astronomy and High-Energy Stellar Astronomy, would dock with the Station's front port on the artificial-gravity module when they needed servicing; for example, after they had expended their photographic film. AMs would rely on the Station for electrical power, while FFMs would each sport a pair of electricity-generating solar arrays.

Image credit: MDAC/NASA.

CCMs, meanwhile, would deliver non-human biology experiment subjects beginning in early 1979. They would transport to the Station small vertebrates such as rats and invertebrates such as fruit flies. Vascular plants would first reach the Station later that same year.

Also in late 1979, the general Stellar Astronomy FFM would arrive near the Station. MDAC envisioned that UV Stellar Astronomy and High-Energy Stellar Astronomy would conclude at the beginning of 1981, while Solar Astronomy, general Stellar Astronomy, and small vertebrate, invertebrate, and plant studies would continue until the Station reached its planned end-of-life in 1987. Biomedical centrifuge and fluid physics AMs would arrive in late 1981, with the former remaining with the Station until end-of-life and the latter departing in late 1985. Small Vertebrates Centrifuge and Infrared Stellar AMs would arrive in late 1982 and remain docked until Station end-of-life.

Late 1983 would see arrival of the Remote Maneuvering Satellite (RMS), which would take up residence in a "hangar" in the airlock at the Station's front port. Dorrenbacher called the RMS a "subsatellite," but did not otherwise describe its role. RMS operations would cease in late 1986.

Also in late 1983, the X-Ray Telescope FFM and advanced particle and plasma physics experiment apparatus would arrive. The X-Ray Telescope FFM would operate through Station end-of-life. Some advanced physics experiments would cease in early 1985; all would end by late 1986. Late 1985 would see the arrival of materials science experiment apparatus and the Cosmic-Ray Physics FFM, both of which would remain in operation through Station end-of-life.

Dorrenbacher described how the vast quantity of data Station experiments generated would reach Earth. MDAC estimated that 9070 kilograms of magnetic tape, microfilm, exposed photographic and X-ray film, and photographic plates would need to be returned to Earth each year. The Station's four large dish antennas would enable continuous two-way television communication through ground stations or through relay satellites so that Station and Earth researchers could work together continuously in real time. The antennas would be capable of transmitting up to a trillion bits (one terabyte) of data to Earth each day.

The Station's impressive experiment capability would demand careful management of crew time. MDAC assumed that Station crews would work around the clock, with six men on duty and six off duty at all times. Each crew would include eight scientist-engineers and four Station flight-crew crewmembers. Two flight-crew and four scientist-engineers would work during each 12-hour shift.

One scientist-engineer would serve as principal scientist. He would work closely with the flight-crew commander, who would have responsibility for the safety of the entire crew, to ensure that science interests were taken into account during Station operations.

Two scientist-engineers would serve as principal investigator representatives. They would use the Station's considerable communications capabilities to work directly with scientists on Earth.

Image credit: MDAC/NASA.

Off-duty Station crew members would spend most of their time on the living decks (Decks 1, 3, and — during the artificial-gravity experiment series — 6). There, Dorrenbacher explained, they would have at their disposal private staterooms with 4.6 meters of floor space for "relaxation, recreation, study, and meditation." Each living deck would include six staterooms, which together would take up about half the deck's volume. Staterooms would each include a small viewport for watching the Earth go by, a folding bunk, a desk, and storage cabinets for personal belongings.

When not in their staterooms, off-duty crew members could hang out in their living deck's multipurpose wardroom, which would include portable dining tables with zero-gravity restraints in place of conventional chairs. Dorrenbacher told the Paris meeting that the wardoom could be "quickly and easily" converted into a gym, theater, meeting room, or recreation room.

Image credit: MDAC/NASA.

Visible in the wardroom are three large observation windows, an exercise device to simulate weightlifting, zero-gravity "seats" both stowed (left) and in use, a round 1.5-meter hatch to which CCMs can dock (right), and a visiting Vulcan scientist. Image credit: MDAC/NASA.

Cabinets in the galley, adjacent to the wardroom, would be kept stocked with enough food for 90 days. Crew-members could choose to serve themselves or could take it in turns to prepare meal trays for their crew-mates. Food would be "selected for maximum palatability with various degrees of wet or even fresh foods."

The three living decks would each include a hygiene facility. Apparently configured for men only, these would include a toilet, two urinals, two hand-washing units, a shower, a clothes-washing machine, and a clothes-dryer. Hygiene facilities would be located next to water-recycling life-support machinery on each living deck.

MDAC proposed a novel approach to station orbit maintenance. Some processed wastewater would be electrolyzed (split into oxygen and hydrogen using electricity) and the hydrogen used to fuel low-thrust resistojets on the Station's hull. MDAC calculated that water delivered to the Station in food would be sufficient to maintain its orbital altitude.

MDAC placed core module control consoles on the living decks adjacent to the wardrooms. The artificial-gravity module would include an identical control console on Deck 5. The primary control console — the Station's "bridge" — would be located on Deck 3. The control consoles on Decks 1 and 5 would serve as backups for the Deck 3 primary console, and would also support experiments; they might, for example, be used to monitor data arriving from the FFMs.

Dorrenbacher then described an arbitrarily selected moment in the MDAC Phase B Station's 10-year career to illustrate possible activities of on-duty and off-duty crew-members. At 2030 hours Greenwich Mean Time on 26 March 1985, the flight-crew commander would be at work conducting safety checks on space suits stored in the core module central tunnel. The shift's other on-duty flight-crew astronaut would, meanwhile, sample the Deck 1 water system to ensure that it contained no harmful bacteria.

Two of the on-duty scientist-engineers would work in the Deck 2 labs and two elsewhere. The physician would analyze crew blood and urine samples in the biomedical lab, while the psychologist would analyze data on "crew skill retention in extended zero gravity" in the man/system integration lab. The geologist/photo-optical engineer, meanwhile, would install and align sensors in the Earth Survey AM docked to Deck 2, and the astronomer/systems engineer would monitor data from the X-Ray Telescope FFM at the secondary control console on Deck 5.

The six off-duty crew-members, having just finished their late meal, would all be found on Deck 3. The operations director, a flight-crew crew-member, would take a shower in the hygiene facility while the physician, a scientist-engineer, would watch a videotaped television program in his stateroom before going to sleep.

The other off-duty crew would be in the wardroom. The station controller, a flight-crew astronaut, would compete against the astrophysicist, a scientist/engineer, in a simulated time-distance race on stationary exercise bikes. Nearby, the biologist and the electro-mechanical engineer, both scientist-engineers, would compete in a game of "computer football."

Dorrenbacher concluded his presentation by assuring Paine, Bondi, and the other NASA and ESRO officials that MDAC's 12-man Phase B Space Station would be a "low-cost, flexible, international research facility" built using known technology (that is, mostly adaptations and upgrades of Skylab hardware). Furthermore, its module designs would be readily adaptable to future NASA/ESRO joint missions; specifically, they could serve as building blocks making up the 100-man Space Base of the mid-to-late 1980s.

Conceptual art of 100-man Space Base in orbit over Australia and New Guinea. The two truss-work arms hold at their ends nuclear reactors and their rectangular waste heat radiators. A free-flying large space telescope orbits nearby. Image credit: NASA.

As noted earlier, NASA had instructed MDAC to design its 12-man Station to be launched on a Saturn V. Dorrenbacher failed to mention in his briefing that NASA Administrator Paine had announced on 13 January 1970, six months before the Paris briefing, that Saturn V production and test facilities would be mothballed, and that the fifteenth and last Saturn V of the Apollo buy, previously assigned to the Apollo 20 Moon mission, would instead launch Skylab A. He also neglected to mention that NASA had directed NAR and MDAC in early May to begin considering designs for Space Stations that could be assembled solely from modules launched in the Shuttle Orbiter's cargo bay.

On 30 June 1970, NASA extended the MDAC and NAR Phase B Saturn V-launched Station contracts for six months. A month later, two highly significant events took place: Paine resigned the post of NASA Administrator effective 15 September (28 July) and NASA formally directed MDAC and NAR to shift their attention to studying Shuttle-launched modular Station designs within the scope of the Phase B contract, which, as has been discussed, already included provisions for Shuttle-launched research modules (29 July).

Just before he stepped down, Paine announced that Saturn V production would be permanently halted. Soon after he departed, the Space Station groups he established drew up an SOW for a focused Phase B Extension study of a Shuttle-launched modular Station. NASA released the SOW on 16 November 1970. MDAC, NAR, and their respective subcontractors began Phase B Extension work on 1 February 1971.

NASA also moved to toe the line on the Nixon Administration's slowly emerging space policy. That policy gave lukewarm support to the Space Shuttle and left the Space Station it was meant to serve in limbo.

Aware that the Station enjoyed almost no support in the Nixon White House, NASA directed MDAC and NAR to study research modules that would operate attached to a Shuttle Orbiter. The modules would each carry a small team of scientists and enough expendables (for example, reactants for the Orbiter's electricity-generating fuel cells) to stretch the period of time the Orbiter could spend in space to 30 days. This became known as the "sortie lab" concept.

On 5 January 1972, NASA Administrator James Fletcher announced that President Nixon's FY 1973 NASA budget request included modest funds to begin development of a partially reusable Space Shuttle. Though little mention was made of a Space Station, the Phase B Extension studies lingered on until late in the year.

On 29 November 1972, Fletcher formally abolished NASA's Space Station Task Force and established the Sortie Lab Task Force. In August 1973, NASA and ESRO agreed that the latter should develop the Sortie Lab, which became known subsequently as Spacelab.

Cutaway art of Spacelab pressurized module in Space Shuttle payload bay. Image credit: NASA.

Sources

"NASA Plans Five-Year Fund Rise," W. Normyle, Aviation Week & Space Technology, 14 October 1968, pp. 16-17.

"Pace of Post-Apollo Planning Rises," W. Normyle, Aviation Week & Space Technology, 3 February 1969, p. 16.

"NASA Aims at 100-Man Station," W. Normyle, Aviation Week & Space Technology, 24 February 1969, pp. 16-17.

"Against the Tide," Aviation Week & Space Technology, 17 March 1969, p. 15.

"Shuttle Group Readies Proposal Requests," Aviation Week & Space Technology, 19 January 1970, pp. 17-18.

Development and Use of a 12-Man Space Station, MDC G0583, C. Dorrenbacher, McDonnell Douglas Astronautics Company, Briefing to the European Space Research Organization on Space Station Plans and Programs in Paris, France, 3-5 June 1970.

Astronautics and Aeronautics 1968, NASA SP-4010, pp. 212-213.

Astronautics and Aeronautics 1970, NASA SP-4015, pp. 193-194.

Space Stations: A Policy History, J. Logsdon, George Washington University, NASA Contract NAS9-16461, NASA Johnson Space Center, no date (1980), pp. I-16, II-1-5, II-8-10, II-13-15, II-18-33.

More Information

Space Station Gemini (1962)

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

Keep My Memory Green: Skill Retention During Long-Duration Spaceflight (1968)