The PSAC then addressed piloted Mars exploration, writing that "[p]rudence suggests that the possibility of undertaking a manned voyage to Mars be kept in mind but that a national commitment to this project be deferred at this time." 88 The STS, it expected, "could place the equipment needed for the Mars mission in orbit with one or two dozen launches and at a cost substantially below that of a single Saturn V." It also recommended that the permanent space station it said should precede a piloted Mars mission be deferred until after the STS could be used to assemble it. 89 Despite the heavy reliance it placed on the STS, the PSAC recommended deferring a decision to build it until FY 1972.
In July 1970, Paine submitted his resignation. On 15 September the first anniversary of the release of the STG and NASA reports, George Low took over as Acting NASA Administrator. In February 1971, Presidential Assistant Peter Flanigan was ordered to find a NASA Administrator who would "turn down NASA's empire-building fervor and turn his attention to . . . work[ing] with the OMB and White House." 90
The Last Mars Study
The PMRG, meanwhile, continued low-level Mars expedition planning. NASA's post-Apollo Mars aspirations died with a whimper—a call to NASA Centers participating in the PMRG for reports summing up their work. PMRG work at MSC resided in the Engineering and Development Directorate's Advanced Studies Office under Morris Jenkins. MSC Associate Director of Engineering Maxime Faget reviewed Jenkins' February 1971 report. In his introduction, Jenkins explained,
Official statements regarding the manned Mars mission have always been conditioned by an emphasis that there was no set time frame for it. This together with problems of budget constraints on the more immediate future programs and the overall posture of the space program, influenced formal support for this study. Justifiably, the formal support was always very small and . . . non-continuous . . . . 91
The guiding principle of MSC's PMRG study was austerity. In general configuration its Mars ship resembled Boeing's 1968 behemoth, but chemical propulsion stood in for nuclear. According to Jenkins, "everything [was] done to make [this study] a useful point of departure when national priorities and economic considerations encourage the mounting of a manned Mars expedition." 92 MSC targeted its 570-day Mars expedition for the 1987-88 launch opportunity, following an 11-year development and test period beginning in the mid-1970s.
Figure 17—Last gasp (for a while): NASA's 1971 Mars spaceship design, the last until the 1980s, proposed to reduce cost by using projected Space Shuttle technology and rejecting nuclear engines in favor of cheaper chemical propulsion. (Manned Exploration Requirements and Considerations, Advanced Studies Office, Engineering and Development Directorate, NASA Manned Spacecraft Center, Houston, Texas, February 1971, p. 5-2.)
<!-- image -->MSC assumed availability of a fully reusable Space Shuttle based on Max Faget's "flyback" design. The flyback shuttle would include a winged orbiter launched on a winged booster. Both booster and orbiter would carry astronauts. MSC envisioned a booster the size of a 747 and an orbiter on the scale of a DC-9.
The study rejected launching Mars spacecraft components in the 15-foot-diameter payload bay of the orbiter because as many as 30 modules would have to be launched separately and brought together in orbit, necessitating a "complex and lengthy assembly and checkout process." 93 Instead, MSC proposed launching the Mars ship's three 24-foot-diameter modules on the back of the Shuttle booster with the aid of Chemical Propulsion System (CPS) stages. Three CPS stages would be launched into orbit without attached modules.
The Shuttle booster would carry the CPS and attached module (if any) partway to orbit, then separate to return to the launch site. The CPS would then ignite to achieve Earth orbit. Each CPS would weigh 30 tons empty and hold up to 270 tons of liquid hydrogen/liquid oxygen propellants. In keeping with the principle of austerity, the CPS stages would use the same rocket engine and propellant tank designs as the Shuttle booster and orbiter, and do double duty as Mars ship propulsion stages. Assembling the expedition's single ship would need 71 Shuttle booster launches. Six would launch the ship (three modules and six CPS stages), and the remainder would carry Shuttle orbiters serving as tankers for loading the CPS stages with propellants.
The assembled Mars ship would include a hangar for automated probes and a MEM based on the 1968 NAR design. For redundancy, its 55-ton, four-deck Mission Module would be split into two independent pressurized volumes, each containing a duplicate spacecraft control station. Deck four would be the ship's solar flare radiation shelter. The 65-foot-long Electrical Power System module would contain pressurized gas storage tanks and twin solar arrays. The crew would rotate the Mars ship end over end about twice per minute to produce artificial gravity in the Mission Module equal to one-sixth Earth's gravity (one lunar gravity).
Earth departure would require a series of maneuvers. Maneuver 1 would expend two CPS stages to place the Mars ship in elliptical "intermediate orbit." Maneuver 2 and Maneuver 3 would use one CPS stage—the first would place the ship in elliptical "waiting orbit," and the second would adjust the plane of the departure path. Space tugs would later recover the three discarded CPS stages for reuse. Maneuver 4 would place the ship on a 6-month trajectory to Mars. The fourth CPS would enter solar orbit after detaching from the Mars ship and would not be recovered.
Slowing the ship so that Mars' gravity could capture it into a 200-mile by 10,000-mile orbit would expend the fifth CPS. The elliptical orbit would require less propellant to enter and depart than a circular one. The five-person crew would spend 15 days in orbit studying Mars and preparing the MEM for landing; then three crewmembers would separate in the MEM, leaving behind two to watch over the mothership.
The MEM crew would explore their landing site using a pair of unpressurized electric rovers resembling the Apollo Lunar Roving Vehicle, which was slated to be driven on the Moon for the first time on Apollo 15 in July 1971. During Mars surface excursions, one crewmember would remain in the MEM while the other two took out one rover each. This "tandem convoy" arrangement would allow the Mars explorers to avoid the "walk back" limit imposed on single-rover traverses in the Apollo program. Walk back distance was limited less by astronaut stamina than by the amount of water and air the space suit backpacks could hold. If one Mars rover failed, the functional rover would return both astronauts to the MEM. Each rover would include a hook for towing the failed rover back to the MEM for repairs.
Rover maximum speed would be 10 miles per hour, and total area available to two rovers would amount to 8,000 square miles, compared to only 80 square miles for a single rover. Once every 15 days, a 36-hour traverse of up to 152 miles would occur, with the astronauts sleeping through the frigid Martian night on the parked rovers in their hard-shelled aluminum space suits. Jenkins did not attempt to estimate the amount of sleep the astronauts might actually be able to achieve during their overnight camping trips.
The astronauts would collect samples of rock and soil with emphasis on finding possible life. According to the MSC report, "[t]he potential for even elementary life to exist on another planet in the solar system may . . . be the keystone to the implementation of a manned planetary exploration program . . . man's unique capabilities in exploration could . . . have a direct qualitative impact on life science yield." 94
After 45 days of surface exploration, the crew would blast off in the MEM ascent stage and dock with the mothership. Any specimens of Mars life collected would be transferred to a Mars environment simulator. The crew would discard the ascent stage; then the sixth and final CPS would ignite to push the ship back toward Earth. The MEM astronauts would remain quarantined in one pressurized volume until the danger of spreading Martian contagion to the other astronauts was judged to be past.
The MSC PMRG report received only limited distribution within NASA and virtually none outside the Agency. Formal studies within NASA aimed at sending humans to Mars would not occur again until the Manned Mars Missions exercise in 1984 and 1985.
Chapter 5: Apogee
NERVA Falls, Shuttle Rises
The OMB's FY 1972 request for NASA was $3.31 billion. The budget slashed NERVA funding in favor of continued Space Shuttle studies. Combined AEC-NASA nuclear rocket funding plummeted to $30 million split evenly between the two agencies. NASA and the AEC had together requested $110 million. The allotted budget threatened to place the NRDS on standby and was considered by many sufficient only to shut down the program.
In February 1971, Clinton Anderson held a hearing on the cut in NASA's NERVA funding. In his introductory remarks, he lauded the nuclear rocket program as "one of the most successful space technology programs ever undertaken" and pointed to the $1.4-billion investment in nuclear propulsion technology since 1955. 95 Senator Alan Bible (Democrat-Nevada) then pointed out that the STG report called for nuclear rockets. 96
Acting NASA Administrator George Low took his marching orders from the highest levels of the Nixon White House. The Earth-orbital Shuttle had to come first, he said—without it NERVA had no ride to space. He told the Senators that, "NERVA needs the Shuttle, but the Shuttle does not need NERVA." 97
Low denied that the funding cut would kill the program, explaining that "useful work on long lead-time items" could be accomplished. 98 There would, however, be no technical progress during FY 1972, and possibly none in FY 1973. "We have not, as yet, been able to look forward beyond that," Low added. 99
Two months later, in May 1971, 21 members of Congress wrote to President Nixon requesting more funds for NERVA in FY 1972. When the White House failed to respond, Congress of its own accord budgeted $81 million for nuclear rockets, of which NASA's portion was $38 million. In October, however, the OMB refused to release more than the $30 million the Administration had requested. In November the OMB stood by its FY 1972 nuclear propulsion request despite protests from the Senate floor. 100
On 5 January 1972, President Nixon met with James Fletcher, Tom Paine's successor as NASA Administrator, at the "Western White House" in San Clemente, California. Afterward, Fletcher read out Nixon's statement calling for an FY 1973 new start on the Shuttle. The announcement's venue was significant—California, a state of many aerospace firms, was vital to Nixon's 1972 reelection bid. 101 Nixon pointed out that "this major new national enterprise will engage the best efforts of thousands of highly skilled workers and hundreds of contractor firms over the next several years." Fletcher added that it was "the only meaningful new manned program that can be accomplished on a modest budget." 102 First flight was scheduled for 1978.
Nixon sent his FY 1973 budget to Capitol Hill on 24 January 1972. As its supporters had feared, the budget contained no funds for NERVA. Anderson, nuclear propulsion's greatest champion, was ill and could not defend it. The last NERVA tests occurred in June and July of 1972. Anderson retired from the Senate at the end of 1972. The FY 1974 budget terminated what remained of the U.S. nuclear rocket program. 103
With both NERVA and Saturn V gone—the last Saturn V flew in May 1973—NASA's piloted space flight ambitions collapsed back to low-Earth orbit. Yet the Agency did not cease to strive toward Mars. As we will see in the next chapter, NASA's robot explorers conducted the first in-depth Mars exploration in the 1970s, holding open the door for renewed piloted Mars planning.