NASA's Planetary Joint Action Group Piloted Mars Flyby Study (1966) (2)
MSSR after touchdown on Mars. A = sample container attached to ascent vehicle third stage; B = ascent vehicle with three rocket stages with toroidal tanks (numbered in reverse order of use); C = ascent vehicle protective cover/shield protecting deployed science compartment during ascent vehicle liftoff; D = deployed science compartment; E = descent motor cluster. Image credit: NASA/DSFPortree.The Planetary JAG proposed four sample collectors of different designs in the hope that at least one would successfully sample the unknown surface materials of Mars, plus a single rock drill for collecting subsurface samples and a filter for sampling airborne dust. Of the four collectors, three — two with rotating cylinders intended to scrape the surface and a "vacuum cleaner" — assumed a dry and dusty Mars, while a fourth — the "sticky string" collector — would serve well if Mars turned out to be "tacky or viscous." About two pounds (0.9 kilograms) of material would be collected. A color film camera would automatically photograph the sampling sites then would transfer its film to the MSSR sample container.
Meanwhile, the other probes would arrive at Mars. The solar-powered Orbiter, with a 200-pound (90-kilogram) camera, would use a three-stage liquid-propellant propulsion system to slow down and capture into a 185-mile (300-kilometer) near-polar orbit four hours before flyby spacecraft periapsis. The Lander would reach Mars two hours before periapsis. An hour after landing it would launch a 50-pound (23-kilogram) solid-propellant sounding rocket to an altitude of about 45 miles (70 kilometers). The three Aerodynamic Drag/Impacters would enter the martian atmosphere six minutes before periapsis. Their missions would end when they struck the martian surface.
The three-stage MSSR ascent vehicle would lift off in daylight 11.5 minutes before flyby spacecraft periapsis. Stage 1 would burn out and separate 5.5 minutes later, when the sample container was about 1540 miles (2480 kilometers) behind the flyby spacecraft. Stage 2 would then burn for 4.5 minutes, closing the distance to about 540 miles (870 kilometers). After a pause, Stage 3 would burn for about a minute, placing the sample container very near the piloted flyby spacecraft over the night side of Mars five minutes after periapsis. The astronauts would extend an arm-mounted docking ring, capture the sample container and third stage, and swing them to a linkup with a port on the biology lab located inside the EM.
Flyby spacecraft periapsis would occur about 125 miles (200 kilometers) above Mars, at which time the spacecraft would be moving at about 30,000 feet per second (9140 meters per second). At that altitude, the spacecraft's telescope would, with motion-compensation slewing, in theory be capable of discerning surface features 1.5 feet (0.5 meters) across. During the flyby, Mars's gravity would bend the spacecraft's course by only 17°.
The MSSR, Lander, and Orbiter probes would continue to explore Mars as the piloted flyby spacecraft moved outward past the planet, at first relaying data at a high rate via the flyby spacecraft and then transmitting directly to Earth at a lower rate. The authors of the PDP hoped that they could continue to return data from Mars for several years.
Assuming Earth departure on 5 September 1975, the flyby crew would need a further 537 days to return to Earth. Early in that period, they would spend much of their time examining the Mars samples. Later, they would return to their wide-ranging astronomy studies. The Planetary JAG suggested that they could study 12-mile-wide (19.75-kilometer-wide) asteroid 149 Medusa at a distance of about 20 million miles (32 million kilometers) 170 days after Mars periapsis and 75-mile-wide (120-kilometer-wide) asteroid 156 Xanthippe at a distance of about 14 million miles (22.5 million kilometers) 150 days after that. They might also discover new asteroids and comets.
The flyby spacecraft would be on the opposite side of the Sun from the Earth when it reached aphelion at 2.2 times the Earth-Sun distance. The Planetary JAG anticipated that data the astronauts collected from their unique vantage point could be combined with data collected simultaneously on Earth to generate a full Sun portrait for the first time.
During the long flight, the crew could expect to observe many solar flares. Some would be directed toward the piloted flyby spacecraft. At such times, the crew would shelter in the thick-skinned EEM. Toroidal tanks containing PM course-correction propellants and spherical tanks containing MM life support gases and liquids would surround and provide additional radiation shielding for the EEM.
The piloted flyby spacecraft would return to Earth between 18 and 26 July 1977. The four astronauts would enter the EEM with the Mars samples and separate from the piloted flyby spacecraft. They would use the attached PM to nudge their course toward Earth, then would cast it off. The abandoned flyby spacecraft would swing past Earth and enter solar orbit; the EEM, meanwhile, would enter Earth's atmosphere at a speed of 49,100 feet per second, decelerate, and descend on parachutes to a land landing. Solid-propellant rocket motors would soften touchdown.
The Planetary JAG envisioned that its series of four piloted flybys would pave the way for piloted Mars landing and Venus orbital missions using nuclear-thermal rockets. These could begin as early as 1980 and might continue into the 1990s, when a Mars outpost might be established.
With the PDP in circulation, planning began for a new phase of Planetary JAG activity. In the minutes of a meeting held on 12 October 1966 at NASA Headquarters, Edward Z. Gray proposed spending $1.7 million of NASA's $8.45-million advance planning budget on the piloted flyby concept in Fiscal Year (FY) 1967. Of this, $250,000 would be spent to prepare for release to U.S. industry of contracts for an MSSR study in FY 1968.
The pace of piloted flyby planning picked up in November and December 1966. On 17 November 1966, Gray called an advance planning meeting at NASA Headquarters for 6 December 1966. In a telex message dated 2 December, he explained that "the purpose of continuing activity in the manned planetary area is to be in a position to initiate a flyby project in FY 1969." He wrote that "to accomplish this end, we need to prepare a project proposal by mid-April 1967, in time for consideration in the FY 1969 budget cycle."
The next Planetary JAG meeting was held at NASA MSC on 17 January 1967. In the early afternoon on 27 January, in response to issues raised during that meeting, Gray dispatched a telex in which he called on participants in the Planetary JAG to address "soft areas" in the 3 October 1966 report by mid-April. He called "experiment return from a flyby mission. . .one of its major attractions and an area which has received many searching questions." A little more than five hours after Gray sent out his message, fire raged through the AS-204/Apollo 1 spacecraft at Cape Kennedy, Florida, killing astronauts Virgil "Gus" Grissom, Edward White, and Roger Chaffee.
Piloted flyby planning became a casualty of Congressional backlash from the fire, which generated searching questions for NASA more pressing and immediate than any associated with the piloted flyby mission. Planetary JAG work did not, however, end immediately. In fact, in May 1967, Edward Z. Gray and his deputy Franklin Dixon felt confident enough to go public with the piloted flyby mission at the 5th Goddard Memorial Symposium in Washington, DC. They called for the 1975 piloted Mars flyby to be made a formal new start program in NASA's FY 1969 budget.
Gray and Dixon eschewed the term "flyby," which had become closely associated with robotic probes after Mariner IV, in favor of calling the proposed mission a "retriever" or an "encounter." Whatever it was called, the piloted flyby concept — and, indeed, all NASA planning designed to give the space agency a future beyond Apollo — was in deep trouble by the summer of 1967. In September 1967, goaded by a Request For Proposals (RFP) NASA MSC distributed to industry aimed at selecting contractors for the MSSR study, Congress zeroed out all funding for NASA advance planning in FY 1968. NASA MSC collected RFP responses from industry but awarded no contracts.
Meanwhile, the Jet Propulsion Laboratory (JPL), with assistance from the Illinois Institute of Technology Research Institute (IITRI), completed a study of an all-robotic Automated Mars Surface Sample Return (AMSSR) mission. The small study team had begun work toward their 15 March 1967 report, a direct response to the Planetary JAG's 3 October 1966 PDP, on 26 October 1966. The team argued that an AMSSR mission based on Voyager technology and requiring but a single Saturn V launch could be much cheaper than a piloted flyby with MSSR. It was the first U.S. study of an robotic Mars Sample Return (MSR) mission.
If an AMSSR probe ever flew, however, it would not be derived from Voyager, for that program had come to be seen as an expensive foot in the door leading to an even more expensive piloted Mars mission. Congress cancelled Voyager in August 1967, just before it slashed NASA advance planning funding.
In large part because the Soviet Union had declared that it would explore the Solar System with robots, U.S. robotic Mars exploration fared better than did piloted flybys. Negotiations with Congress in September 1967 led to a promise of funding in FY 1969 for a pair of Mariner Mars orbiter missions in 1971 and a pair of reduced-cost Mars lander/orbiter missions in 1973 in a new program dubbed Viking. SourcesMemorandum, J. West, AD/Chief, Advanced Spacecraft Planning to Distribution, "Planetary Exploration Program Study — request for review and comments on systems parameters," NASA Manned Spacecraft Center, 9 May 1966.
Memorandum, R. Hock, DP/Chief, Advanced Programs Office (PPR-2) to Distribution, "Minutes of Joint Action Group Meeting on June 29 and 30, 1966," NASA Kennedy Space Center, 8 July 1966.
Planetary Exploration Utilizing a Manned Flight System, NASA Office of Manned Space Flight, 3 October 1966.
Memorandum, MT/Director, Advanced Manned Missions Program to NASA George C. Marshall Space Center, NASA Manned Spacecraft Center, and NASA John F. Kennedy Space Center, "FY 1967 Advanced Studies Planning," 27 October 1966.
Telex, Edward Z. Gray, Dir, Advanced Manned Missions Program, NASA Office of Manned Space Flight, to NASA MSFC Huntsville, NASA MSC Houston, and NASA KSC FLA, 2 December 1966.
Telex [Priority], E. Z. Gray, Director Advanced Manned Missions Program to NASA MSFC Huntsville ALA, Kennedy Space Center FLA, and MSC Houston TEX, 27 January 1967.
Humans to Mars: Fifty Years of Mission Planning,1950-2000, NASA SP-2001-4521, Monographs in Aerospace History #21, David S. F. Portree, NASA Headquarters History Office, February 2001, pp. 23-32.
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