Blueprint for 1970s planetary exploration (1968)

In August 1967, Congress refused to support NASA's plans for the 1970s. Citing fiscal restraint, it rejected piloted Mars/Venus flyby missions in 1975 and 1977 and canceled the Voyager Mars/Venus program, NASA's only robotic program planned for the decade. The Apollo Applications Program, which had been tapped as the agency's main 1970s piloted program, suffered a cut of half a billion dollars.

This assault on NASA's future was partly the result of the deadly Apollo 1 fire (January 1967), which undermined confidence in the U.S. civilian space agency. A growing Federal budget deficit fueled by the escalating war in Indochina also played a role.

NASA's detractors argued that piloted flybys, Voyager, and AAP were stealthy steps toward an early commitment to costly piloted Mars landing missions. Others complained that NASA's program lacked "balance." This criticism meant different things coming from different people. For some, it meant that NASA gave to astronauts tasks that robots could perform more cheaply and with less risk; for others, it meant that NASA placed too much emphasis on the moon and Mars and not enough on the rest of the Solar System.

NASA officials met with Congressional leaders in late September 1967 to try to negotiate a replacement for Voyager. NASA Administrator James Webb and others reminded them that, with Voyager gone, the U.S. would have no robotic planetary program after the Mariner 1969 Mars flyby missions, leaving to the Soviet Union the prestige benefits of Solar System exploration. Congress relented partially, agreeing to initiate funding in Fiscal Year 1969 for a pair of Mariner 1971 Mars orbiters and a pair of Mariner-based Mars orbiter/lander missions in 1973.

This concession, combined with the successful first unmanned flight of the Apollo Saturn V rocket (Apollo 4) in early November 1967, encouraged some within NASA to look for ways of accommodating the detractors while continuing planning for piloted Mars missions. In late November-early December 1967, NASA's Office of Manned Space Flight asked J. Downs and W. Thompson of Bellcomm, NASA's Apollo planning contractor, to develop a plan for a feasible "balanced manned and unmanned planetary program through 1980." Their blueprint, completed in late February 1968, included Mariner-based robotic Mars and Venus spacecraft as precursors to piloted Mars and Venus flybys and robotic pure science missions to Mercury, Jupiter, Saturn, and beyond.

Downs and Thompson kicked off their program with a Mariner Venus flyby in 1970. The spacecraft, which would be built from "spare parts" left over from Mariner Mars 1969, might use Venus's gravity to speed it toward a flyby of the planet Mercury. The next year, NASA would launch the Mariner Mars orbiters it had discussed with Congress. The Bellcomm engineers called for them to be launched on Titan III-C rockets (bottom image below) so that they could each carry to Mars a 350-pound rough-landing probe bearing 13 pounds of instrumentation. The probes would begin the in-situ search for life on Mars.

Next up, in 1972, a Titan III-C would launch a Venus orbiter with an atmosphere probe. In keeping with NASA's agreement with Congress, two more Titan III-C rockets would launch one Mars orbiter with probe each in 1973. Downs and Thompson expected that the 1971 landing probe would have found life on Mars, so the instruments on the twin 1973 probes could focus on learning about that life. In addition to Mars, the orbiters would image Phobos and Deimos, the two small martian moons.

The year 1973 would also see a Mariner spacecraft fly past Venus and release a 600-pound probe designed to survive landing on the cloudy planet's harsh surface. With help from Venus's gravity, the Mariner would then fly past Mercury. Downs and Thompson noted that placing a spacecraft into orbit around Mercury would demand a great deal of energy (hence propellant), and advised that the decision about whether to fly a Mercury orbiter should be postponed until after the 1973 flyby. They also noted that the next Venus-Mercury flyby opportunity would not occur until 1982.

In 1974, NASA would expand its horizons to the stars by launching a 600-pound "Galactic Jupiter Probe" on an Atlas rocket with a Centaur upper stage. As envisioned by engineers at NASA's Goddard Space Flight Center in Maryland, the Galactic Jupiter probe would explore Jupiter and use a gravity assist from that giant planet to gain speed and bend its course. The spacecraft would climb above the plane of the ecliptic to explore interplanetary particles and fields and, ultimately, escape the Solar System entirely to wander derelict among the stars.

In the Downs-Thompson blueprint, 1975 was a busy year. A Mars orbiter more sophisticated than any launched before would dispatch a heavy probe to a site scientists had identified as exobiologically interesting based on Mariner Mars 1971 and 1973 data. A second Galactic Jupiter Probe would begin its journey to Jupiter and beyond, and NASA would launch two Venus orbiters, each bearing two rough-landing probes.

The year 1976 would see the first of four NASA missions to non-planetary Solar System bodies: an Atlas-Centaur would launch a Mariner past short-period Comet d'Arrest. In 1978, a Mariner would fly past the asteroid Icarus, and asteroid Eros would receive a Mariner in 1979. Finally, a Mariner launched on a Titan III-C/Centaur would fly past Comet Encke in 1980.

In 1977, NASA would launch a Venus orbiter with a high-resolution cloud-piercing radar and multiple atmosphere probes. The new-design Venus orbiter used in 1975 and 1977 would need a launch vehicle more powerful than the Titan III-C - possibly a reduced-capability Saturn V, Downs and Thompson wrote. The 1975 and 1977 Mars missions would also need this powerful rocket.

The 1977 Mars flight would serve as a dedicated precursor for the piloted Mars/Venus flyby mission scheduled for launch in 1978. Its landing probe would, for example, provide data on the topography of a landing site chosen for one of the piloted flyby spacecraft's large Mars Surface Sample Return (MSSR) probes.

The year 1977 would also see the first "Grand Tour" spacecraft leave Earth on a Titan III-C with a Centaur upper stage. The new-design 1000-pound spacecraft would fly past Jupiter and receive a gravity-assist "kick" to Saturn. The gravity-assist it would receive while exploring Saturn would speed it onward to mysterious Uranus, where a third gravity-assist would send it on to Neptune. The spacecraft would fly past the Solar System's most distant gas giant planet nine years after departing Earth. A second Grand Tour spacecraft would leave Earth in 1978.

Also in 1978, NASA would launch the first of two piloted Mars/Venus flyby missions. Downs and Thompson wrote that the two piloted flyby missions would serve as precursors for a piloted Mars landing mission in 1984. The 1978 mission would fly past Venus in 1979, where the crew would release weather balloons and surface impactors. Later in the year, it would fly past Mars, releasing a small swarm of MSSR probes. These would land, collect Mars samples, and return them to the astronauts on the flyby spacecraft for immediate analysis. In 1981, the astronauts would fly past Venus a second time and return to Earth. The second piloted Venus/Mars/Venus flyby mission would depart Earth in 1981 and return home in 1983.

Minimum-energy launch opportunities are what they are, so it is not too surprising that NASA carried out missions resembling those in the Downs-Thompson blueprint. The 1971 Mariner Mars orbiters, for example, corresponded to the Mariner 9 mission, though the latter included no landing probe. (Mariner 8, the first of the intended pair of 1971 Mars orbiters, crashed in the Atlantic after its Atlas-Centaur launch vehicle failed.) The 1973 Mariner-based Mars orbiters and landers were named Viking, then funding cuts pushed their launch to 1975. NASA missed the 1970 Venus-Mercury opportunity, but launched Mariner 10 in 1973 (middle image above). It flew past Venus in February 1974, then past Mercury in March 1974, September 1974, and March 1975.

NASA launched its first Galactic Jupiter Probe two years early; Pioneer 10 left Earth in March 1972 and flew past Jupiter in December 1973 (bottom image above). Its twin, Pioneer 11, left Earth in April 1973, flew past Jupiter in December 1974, and flew past Saturn in September 1979. NASA cancelled the Grand Tour in 1972, but launched the Mariner-based Voyager 1 and 2 spacecraft in September 1977 and August 1977, respectively. Voyager 1 flew past Jupiter in March 1979 and Saturn in November 1979 (top image above). Voyager 2 flew past Jupiter in July 1979, Saturn in August 1981, Uranus in January 1986, and Neptune in August 1989.

NASA launched no piloted flyby in 1978; in fact, when that launch opportunity came and went no American astronauts had reached space since July 1975 (and none would again until April 1981). Instead, it launched the first U.S. Venus orbiter, Pioneer Venus 1 (May 1978), and Pioneer Venus 2 (August 1978), which carried a cluster of four Venus atmosphere entry probes (top image below). Budget cuts and Space Shuttle problems meant that Pioneer Venus 2 was the last U.S. planetary probe to leave Earth for nearly 11 years.

A Feasible Planetary Exploration Program Through 1980 - Case 710, J. P. Downs and W. B. Thompson, Bellcomm, February 29, 1968.

RAND and Mars resources (1962-1963)

Most early Mars expedition plans made little mention of potential martian resources. Apart from using the martian atmosphere to slow the crew lander for landing, Mars spacecraft generally depended little on materials or conditions peculiar to the planet. This was because so little was known of Mars (top image above).

The potential benefits of using martian resources for propellants, building materials, and life support consumables were so compelling, however, that some planners chose to incorporate them into their mission designs anyway. Chief among these benefits was a dramatic reduction in mission mass if Earth-return rocket propellants could be found at Mars.

The Working Group on Extraterrestrial Resources (WGER) formed in early 1962. Besides NASA, the group included representatives from the U.S. Air Force, the Army, the Bureau of Mines, aerospace corporations, and academe. The group, which met throughout the 1960s, focused mainly on lunar resources. A few researchers, however, treated the WGER as a forum for discussing eventual exploitation of Mars resources.

One of these forward-thinkers was Ernst Steinhoff (middle image above), representing the RAND Corporation, a think tank created in 1946 to provide advice to the U.S. military services. RAND had performed Mars studies for the Air Force as early as 1960. Steinhoff, whose specialty was rocket guidance, came to the U.S. in 1945 with Wernher von Braun, Ernst Stuhlinger, Krafft Ehricke, and the other members of the Peenemünde rocket team. After working to launch captured V-2 missiles for the Army (bottom image above), he went to work for U.S. industry in 1956. Steinhoff joined RAND in 1961, and was instrumental in the formation of the WGER the following year. He became the WGER's first chairman.

Steinhoff summed up his Mars work in papers presented at a March 1962 meeting at NASA's Marshall Space Flight Center in Huntsville, Alabama, and at the June 1963 American Astronautical Society Symposium on the Manned Exploration of Mars in Denver. George Morgenthaler of Martin Marietta Corporation organized the Denver symposium, the first non-NASA meeting devoted to piloted Mars travel. As many as 800 engineers and scientists heard Steinhoff's paper and 25 others. It was the first time so many people from Mars-related disciplines had come together in one place, and the last Mars meeting as large until the 1980s. Sky & Telescope magazine reported that the "Denver symposium. . . helped narrow the gaps between engineer, biologist, and astronomer."

Soon after the Denver symposium, Steinhoff became Chief Scientist at the Air Force Missile Development Center at Holloman Air Force Base, New Mexico, after which he continued his involvement with the WGER and his work on Mars subjects at a reduced level. This is unfortunate, because in his two papers he anticipated several Mars mission concepts that would, in time, emerge as significant in Mars exploration planning.

Steinhoff's work focused on "autarchic" - that is, self-sufficient - bases on Mars and Phobos. Self-sufficiency would be achieved through mining and processing local materials, and by equipping the base with regenerable (recycling) life support systems. The Phobos and Mars bases would support scientific research and serve as "terminals" for spacecraft.

Steinhoff estimated that extraterrestrial water could supply over 90% of the logistical needs of space-faring humans. He wrote that the moon's gravity - nearly 20% as powerful as Earth's - would make it an inefficient "interim space base" for fueling Mars-bound ships. Citing Clyde Tombaugh, who had written that Mars's moons were probably made of the same water-rich materials as Mars itself, Steinhoff proposed that Phobos supplant the moon as a stepping stone to Mars. Nuclear systems could cook water out of Phobos rocks, then split it into hydrogen and oxygen rocket propellants.

Steinhoff's early Mars expedition would comprise 18 astronauts in a convoy of three crew and six cargo spacecraft. They would use a conjunction-class profile, traveling to Mars in 256 days, remaining in the Mars system for 485 days, and then returning to Earth in 256 days.

Two chemists and two geologists would prospect Phobos for water-rich rocks. The little moon's weak gravity would enable space-suited astronauts to easily assemble "ready-to-operate" base modules shipped from Earth. Space construction workers, Steinhoff wrote, would be able to carry and connect 50-ton modules by hand.

Winged three-man shuttles based at the Phobos terminal would provide access to the Mars base, which would be built within 25º of the equator for easy access from Phobos's equatorial orbit. Steinhoff assumed that the martian atmosphere would be thick enough to support gliding shuttles requiring minimal landing propellant. He proposed that early shuttles drop cargoes and astronauts by parachute, then blast back to orbit without landing.

Among the early air-dropped cargoes would be a radio-controlled bulldozer, which astronauts on Phobos would use to prepare a safe runway ahead of the first shuttle landing. After the Mars base was established, the shuttles would rely on propellants manufactured on Mars to return to the Phobos base.

The Mars base would use vehicles and building techniques Steinhoff's RAND colleagues proposed in their Air Force studies. Rocket turbine engines tailored to the martian atmosphere would power surface rovers, airplanes, and helicopters with low-mass inflatable parts. Inflatable modules would provide living space for the earliest Mars explorers. Later astronauts would manufacture cement from martian materials, construct masonry and cinderblock buildings, and inhabit martian caves.

After the propellant needs of the Mars system were met, Phobos would become a fueling station for interplanetary spacecraft. Steinhoff estimated that enough propellant could be manufactured in just 100 days to launch a spacecraft from Phobos to 300-mile-high Earth orbit, and that Phobos propellants could cut the time required for transfer between the two worlds in half. He added that "use of indigenous resources, combined with more advanced nuclear ferry systems, may. . . pave the way to intensive interplanetary exploration within the limitations of our national resources." Phobos could, for example, serve as a refueling stop for Jupiter-bound piloted spacecraft.

"Use of Extraterrestrial Resources for Mars Basing," Ernst A. Steinhoff, Exploration of Mars, George Morgenthaler, editor, pp. 468-500; proceedings of the American Astronautical Society Symposium on the Exploration of Mars, Denver, Colorado, June 6-7, 1963.

"A Possible Approach to Scientific Exploration of the Planet Mars," Paper #38, Ernst A. Steinhoff, From Peenemunde to Outer Space, "A Volume of Papers Commemorating the Fiftieth Birthday of Werner von Braun," NASA Marshall Space Flight Center Technical Report, 1962, pp. 803-836.

"Manned Exploration of Mars?" Raymond Watts, Sky & Telescope, August 1963, pp. 63-67, 84.