Astronaut Sally Ride's Mission to Mars (1987)

Astronaut Dr. Sally Ride on board the Space Shuttle Orbiter Challenger during STS-7 (June 1983), her first flight into space. Image credit: NASA.

Dr. Sally Ride was a member of the 1978 astronaut class, the first selected for Space Shuttle flights. During mission STS-7 (18-24 June 1983), she became the first American woman in space. Ride flew one more Shuttle mission — STS-41G (5-13 October 1984) — and served on the Rogers Commission investigating the 28 January 1986 Shuttle Challenger accident before James Fletcher, in his second stint as NASA Administrator, made her his Special Assistant for Strategic Planning on 18 August 1986.

Fletcher charged Ride with drafting a new blueprint for NASA's future. She had help from a small staff, a 12-member advisory panel led by Apollo 11 astronaut Michael Collins, and a six-member space mission design team at Science Applications International Corporation (SAIC) in Schaumburg, Illinois. The result of her 11-month study was a slim report called Leadership and America's Future in Space.

On 22 July 1987, Ride testified before the U.S. House of Representatives Subcommittee on Space Science and Applications about her report. She told the Subcommittee that the "civilian space program faces a dilemma, aspiring toward the visions of the National Commission on Space, but faced with the realities of the Rogers Commission Report." The National Commission on Space (NCOS), mandated by Congress and launched by President Ronald Reagan on 29 March 1985, had been meant to blueprint NASA's future until about 2005. The NCOS counted among its members such luminaries as Neil Armstrong, Chuck Yeager, Gerard O'Neill, Kathryn Sullivan, physicist Luis Alvarez, planetary scientist Laurel Wilkening, and former U.S. Ambassador to the UN Jeane Kirkpatrick.

Headed by Thomas Paine, NASA Administrator from 1968 to 1970, the NCOS had exceeded its mandate. Its report, titled Pioneering the Space Frontier, was a wide-ranging 50-year master plan for "free societies on new worlds" that would have been dismissed as unrealistic even had it not been unveiled in the chaotic aftermath of Challenger. By some accounts, Paine dominated the NCOS process to such an extent that some of its less patient members — for example, Chuck Yeager — ceased to attend meetings.

The Ride Report. Image credit: NASA.

Ride's study aimed to produce a more realistic blueprint of NASA's future. Whereas the NCOS report urged immediate adoption of its expansive (and expensive) "vision," Ride outlined four much more limited "Leadership Initiatives." They were, she explained, meant to serve "as a basis for discussion." They included a piloted Mars program; "Mission to Planet Earth," which aimed to study Earth from space using satellites; "Mission from Planet Earth" (exploration of the Solar System using robotic spacecraft); and construction and operation of a permanent outpost on the Moon.

Each of Ride's proposals could occur in isolation; none necessarily depended on or followed from the others. By Fletcher's command all would rely to some degree on NASA's planned low-Earth orbit (LEO) Space Station.

SAIC began design of the Ride Report's piloted Mars program in January 1987. The company presented its final report to the Office of Exploration (nicknamed "Code Z" for its NASA Headquarters mail code) in November of that year. James Fletcher created Code Z in June 1987 and placed Ride in charge as his Acting Assistant Administrator for Exploration. By then, Ride had announced that she would leave NASA in August. John Aaron, who replaced her as Code Z chief, made SAIC's report the basis for piloted Mars and Phobos mission "Case Studies" in Fiscal Year 1988.

SAIC employed a split/sprint Mars mission design. The company credited a 1985 joint University of Texas/Texas A & M student design project with originating the split/sprint concept, though similar concepts can be traced back to the 1950s. The split/sprint mission would use a pair of spacecraft: an automated one-way cargo spacecraft "slowboat" launched first followed by a piloted "sprint" spacecraft. Both would burn chemical propellants and employ aerobraking.

The cargo spacecraft would follow a propellant-saving low-energy path to Mars. It would transport to Mars orbit propellants for the piloted spacecraft's return to Earth. The piloted sprint spacecraft would leave LEO only after the cargo spacecraft had arrived safely in Mars orbit.

So that its six-person crew would be exposed to weightlessness, radiation, and isolation for as short a time as possible, the piloted spacecraft would follow a roughly six-month path to Mars, remain at the planet for only one month, and then return to Earth in about six months. This would yield a piloted Mars mission duration of no more than 14 months.

Shuttle-derived heavy-lift launch vehicle. Image credit: M. Dowman/Eagle Engineering.

In common with most other post-Challenger piloted Mars plans, the SAIC team abandoned the Space Shuttle as its primary means of launching spacecraft components and propellants to LEO. In the Shuttle's place, it proposed a heavy-lift rocket based in part on Shuttle hardware. The new rocket would debut in 1996 with a launch capability of 36 metric tons to LEO, then would evolve by 2002 to carry 91 metric tons to LEO.

Though it featured a piloted mission of short duration — which in most cases would imply large propellant expenditure — the SAIC split/sprint mission design provided substantial propellant savings by refueling the crew spacecraft in Mars orbit. This would in turn slash the number of costly heavy-lift rockets required to launch spacecraft components and propellants to the Space Station for assembly.

Launching a single round-trip combined crew/cargo sprint spacecraft would, SAIC calculated, need 25 heavy-lift rockets, while the two-spacecraft split/sprint design would need only 15. In addition, because the cargo and crew spacecraft would depart Earth more than a year apart, heavy-lift launches could be spread out over a longer period, making launch vehicle, payload, and launch pad preparations less sensitive to delays caused by weather or rocket malfunctions.

By the time the heavy-lifter attained its maximum launch capability in 2002, Phase I of SAIC's three-phase Mars program would be ended and Phase II would just have begun. Phase I, starting in 1992, would comprise a series of robotic precursor missions. Mars Observer, in 1987 already an approved NASA mission, would map Mars from orbit beginning in 1993; then, in 1995, Mars Observer 2 would establish and act as radio relay for a planet-wide network of hard-landed penetrator sensor stations. Orbital mapping and the seismic/meteorological net would help scientists and engineers to select landing sites for automated Mars Sample Return (MSR) and piloted Mars missions.

Mars Rover Sample Return concept. Image credit: NASA.

A pair of MSR spacecraft would depart Earth in 1996 to collect Mars surface samples and return them to high-Earth orbit (HEO) in 1999. A reusable Orbital Maneuvering Vehicle (OMV) based at the LEO Space Station would retrieve the samples from HEO and deliver them for quarantine and initial study to an "isolation half-module" added to the Station in 1998. The samples would enable scientists to identify hazards in Mars surface materials and would aid engineers in the design of spacecraft, rovers, habitats, space suits, and tools.

Phase I would also include biomedical research on board the Space Station, which Ride assumed would reach Permanent Manned Configuration (PMC) in 1994. Almost immediately after it achieved PMC, NASA would add a Life Science Module. A six-person crew would then conduct a Mars mission simulation on board the Station that would last for the planned piloted sprint mission duration of 14 months.

If the astronauts remained healthy after the simulation, which would be conducted in weightlessness, then in 1996 NASA would begin development of a Mars sprint spacecraft lacking any provision for artificial gravity (that is, no part of it would rotate to create acceleration which the crew would feel as gravity). A module for housing Mars spacecraft assembly crews would join the Station in 2002, kicking off Phase II of SAIC's Mars program. The cargo spacecraft for the first split/sprint mission would depart LEO during the favorable 2003 low-energy Earth-Mars transfer opportunity.

If, on the other hand, biomedical researchers determined that the simulation crew had suffered harm from their long stay in weightlessness, then NASA would add a "variable-gravity module" to the Station in 2001. Crews would conduct simulations in the spinning module to determine the minimum level of artificial gravity required to safeguard astronaut health. Development of an artificial-gravity sprint spacecraft would not commence until after the simulations ended in 2004. If the artificial-gravity sprint spacecraft needed as much development time as its no-gravity counterpart, then the first piloted Mars mission might not leave Earth until 2013. SAIC largely ignored this possibility.

SAIC's automated cargo spacecraft (right) in Earth-orbit launch configuration with large Orbital Transfer Vehicle (OTV). The conical vehicle at the center of the cargo spacecraft's dish-shaped aeroshell is the piloted Mars Lander. Spherical tanks around the Mars Lander contain Earth-return propellants for the piloted sprint spacecraft. Image credit: Science Applications International Corporation.

Launching parts and propellants from Earth's surface for the 238.5-metric-ton cargo spacecraft and a single 349.6-metric-ton reusable Orbital Transfer Vehicle (OTV) would require seven heavy-lift rocket launches. The cargo spacecraft would carry at the center of its 28-meter-diameter bowl-shaped Mars Orbit Insertion (MOI) aerobrake heat shield the mission's two-stage, 60-metric-ton Mars Lander.

Spherical tanks surrounding the Lander would hold the 82.5 tons of cryogenic liquid hydrogen/liquid oxygen propellants the piloted sprint spacecraft would need for return to Earth. The cargo spacecraft would also carry 4.2 metric tons of propellants for correcting its course during flight from Earth to Mars and 16.4 metric tons of propellants for circularizing its Mars-centered orbit after it aerobraked in the martian atmosphere. A 9.1-metric-ton refrigeration system would prevent the propellants from boiling and escaping.

On 9 June 2003, the 30.5-meter-long cargo spacecraft/OTV stack would move away from the Space Station using small thrusters. The OTV would then ignite its main engines to push the cargo spacecraft out of LEO. After sending the cargo spacecraft on its way, the OTV would separate, turn end over end, fire its engines to slow itself, aerobrake in Earth's upper atmosphere, fire its engines to circularize its orbit, and return to the Station for refurbishment, refueling, and reuse.

The cargo spacecraft's course would intersect Mars on 29 December 2003. It would aerobrake in the upper atmosphere of Mars to slow itself so that the planet's gravity could capture it into orbit. The cargo spacecraft would rise to its orbital apoapsis (high point), then fire its rocket engines to raise its orbit periapsis (low point) out of the martian atmosphere and circularize its orbit. Flight controllers would then begin careful checkout and monitoring of the cargo spacecraft and its cargo, paying special attention to the propellants the piloted sprint spacecraft would need for return to Earth.

Partial cutaway view of SAIC's piloted sprint Mars spacecraft. A = bowl-shaped Mars Orbit Insertion aerobrake heat shield; B = cylindrical habitat modules (2); C = cylindrical logistics module; D = cylindrical "bridge" tunnel; E = cylindrical tunnel linking docking unit (right), bridge tunnel, and Earth Recovery Vehicle; F = drum-shaped Earth Recovery Vehicle; G = flattened conical aerobrake heat shield; H = engines (2); I = spherical liquid hydrogen tank; J = spherical liquid oxygen tanks (2). Not shown: cylindrical command module, cylindrical airlock module, and one spherical liquid hydrogen tank. Image credit: Science Applications International Corporation/DSFPortree.

SAIC offered a piloted spacecraft design with 4.4-meter-diameter Station-derived pressurized crew modules connected in a "race track" configuration; that is, in a square with each module linked by short tunnels at or near their ends. A pair of 12.2-meter-long habitat modules, each with a mass of 15.5 metric tons, would form two sides of the square; a 12.2-meter-long, 10.8-metric-ton logistics module would form the third side; and an 8.5-metric-ton command module and a 3.2-metric-ton airlock module would together make up the fourth.

A pressurized "bridge" tunnel would cross the inside of the square, linking directly the two habitat modules. Another tunnel would pierce the center of the bridge tunnel vertically. Its forward end would link with the top of the drum-shaped, 11.9-metric-ton Earth Recovery Vehicle (ERV), while its aft end would carry a docking unit. The ERV, situated deep within the spacecraft's structure, would double as the crew's solar flare "storm shelter."

Four spherical tanks holding a total of 91.9 metric tons of cryogenic liquid hydrogen/liquid oxygen propellants and two rocket engines with a combined mass of 4.6 metric tons would be mounted atop the crew modules. The vertical tunnel's docking unit would protrude beyond the sprint spacecraft's twin engine bells.

The ERV/storm shelter would be mounted at the center of a one-metric-ton, 11.4-meter-diameter flattened conical aerobrake heat shield. ERV, ERV aerobrake, crew modules, tunnels, propellant tanks, and engines would nest within a bowl-shaped, 25-meter-diameter, 16.1-metric-ton MOI aerobrake. Except during propulsive maneuvers and aerobraking, four solar arrays capable of generating a total of 35 kilowatts of electricity at the piloted spacecraft's maximum distance from the Sun (that is, in Mars orbit) would extend beyond the edge of the MOI aerobrake. During maneuvers and aerobraking, the arrays would be folded out of harm's way atop the crew modules. Fully assembled and loaded with propellants, the piloted spacecraft's mass would total 193.7 metric tons.

An assembly crew at the Space Station would link a newly assembled small (197.4-metric-ton) OTV to the piloted spacecraft, then would attach the larger OTV used to launch the cargo spacecraft to the new OTV. This would create a 48-meter-long, 738.7-metric-ton Earth-departure stack.

SAIC's piloted sprint spacecraft (right) in Earth-orbit launch configuration with large and small reusable OTVs. Image credit: Science Applications International Corporation.

The stack would move away from the Space Station on 21 November 2004. Shortly thereafter, the first OTV would ignite its engines to start the second OTV and the piloted sprint spacecraft on their way. Its work completed, it would then separate, aerobrake in Earth's atmosphere, and return to the Station for reuse. The second OTV would repeat this performance, then the piloted sprint spacecraft would burn nearly all of its propellants to place itself on course for Mars.

The piloted spacecraft would aerobrake in the martian atmosphere and fire its engines to circularize its orbit on 3 June 2005. Almost immediately after MOI, the crew would rendezvous with the waiting cargo spacecraft. Three astronauts would board the Mars Lander, deorbit, and land at the pre-selected landing site. They would explore the site for between 10 and 20 days.

The other three astronauts, meanwhile, would transfer the Earth-return propellants stored on board the cargo spacecraft to the piloted spacecraft's empty tanks. They would also discard the piloted spacecraft's MOI aerobrake.

SAIC noted that the ideal trajectory for a sprint Mars mission launched as soon as possible after the cargo spacecraft arrived at Mars on 29 December 2003, would have the piloted spacecraft depart Earth on 8 January 2005, reach Mars on 2 August 2005, depart Mars on 1 September 2005, and return to Earth on 8 January 2006. SAIC's Earth-departure date, a little more than a month ahead of the ideal date, would increase piloted mission duration by almost two months (that is, to 14 months).

Launching the piloted sprint spacecraft early would, however, add an abort option to the mission. For example, if the sprint spacecraft were en route to Mars and the cargo spacecraft propellant refrigeration system failed, allowing the sprint spacecraft Earth-return propellants it kept liquid to turn to gas and escape, then the crew could use the propellants they would have used to circularize their orbit around Mars after aerobraking to cause their spacecraft to skim through Mars's uppermost atmosphere on 3 July 2005. This aero-maneuver, if properly executed, would nudge the piloted spacecraft's course enough that it would intersect Earth on 15 January 2006.

SAIC's Mars crew lander would reach Mars orbit 18 months ahead of its three-person crew. It would become the surface crew's base of operations during a Mars surface stay lasting up to 20 days. Image credit: P. Hudson/NASA.

SAIC envisioned that NASA would launch a series of three split/sprint missions by the end of the first decade of the 21st century. While the first crew explored the surface of Mars and worked in orbit to prepare their spacecraft for the trip home, the cargo spacecraft for the second Mars crew would depart LEO boosted by the same large aerobraking OTV the first mission's cargo and piloted spacecraft had used. The second crew would leave Earth orbit in early 2007 and return from Mars in early 2008. The final crew in the series would depart for Mars in early 2009 and return home in early 2010.

After the third Mars expedition, establishment of a Mars base — Phase III of SAIC's program — could begin. The company provided few details of Phase III.

With their surface mission completed, the first Mars explorers would lift off in the Mars Lander ascent stage. SAIC calculated that the ascent stage would make up about half the mass of the Lander. The piloted spacecraft would rendezvous and dock with the ascent stage in Mars orbit to collect the surface crew and their samples of Mars rocks, sand, and dust. On 2 August 2006, shortly after casting off the spent ascent stage, the astronauts would fire the piloted spacecraft's twin engines to begin their five-month return to Earth.

As Earth loomed large ahead of what remained of the sprint spacecraft, the astronauts would enter the ERV capsule with their samples. The ERV, which would resemble the early "hat box" design of NASA's planned Space Station lifeboat, would slide out of a radiation shield housing that would remain behind on the crew spacecraft. The abandoned sprint spacecraft would then fire its engines a final time to miss Earth and enter orbit about the Sun.

SAIC based its ERV configuration on this NASA design for a Space Station lifeboat. Image credit: NASA.

The ERV would aerobrake in Earth's atmosphere, then an automated OMV from the Space Station would retrieve it. After physical examinations and a period of quarantine on board the Station, the first Mars crew would return to Earth on board a Space Shuttle.

SAIC wrote that its piloted split/sprint Mars mission could support international space cooperation. Other countries, both allies and rivals, could contribute money, services such as propellant delivery, crew members, robotic precursor missions, spacecraft components, and even entire spacecraft. For all the countries involved, piloted Mars missions would "provide an effective catalyst for significant advances in automation, robotics, life sciences[,] and space technologies. . .[and], through direct experience, address and answer key questions about long-duration human space flight and the role of human beings in space exploration."

NASA did not much care for the Ride Report; in fact, the agency at first refused to publish it. Ultimately NASA printed about 2000 copies — an unusually small number for such a high-level report. Perhaps this was because Ride acknowledged that NASA could not hope to lead in all areas of space endeavor. In addition, Ride proposed a manned Mars program after the Space Station was built with no intervening manned Moon program, placed robotic programs on a par with their piloted counterparts, and implied that NASA might not need a new piloted space initiative after it finished building the Space Station.

Her matter-of-fact tone seems also to have annoyed some within NASA. Ride was nearing the end of her nine-year NASA career, so felt free to express herself. She was quick to point out when NASA's actions apparently belied its enthusiasm for piloted missions beyond LEO; for example, when she noted the uncomfortable fact that NASA boss Fletcher had committed only 0.03% of the agency's budget to funding the new Office of Exploration. This, Ride noted, gave the appearance that Code Z had been established merely to quell critics who complained that NASA had no long-term goals.

Following her departure from NASA, Ride worked briefly at Stanford University, her alma mater. In 1989, she became a physics professor at the University of California, San Diego. She led space public outreach projects for NASA, co-founded the Sally Ride Science education company in 2001, participated in the Columbia Accident Investigation Board in 2003, and co-authored several science books for children. In early 2011, she was diagnosed with pancreatic cancer. She died at age 61 on 23 July 2012.

Sources

"Piloted Sprint Missions to Mars," AAS 87-202, J. Niehoff and S. Hoffman, The Case for Mars III: Strategies for Exploration - General Interest and Overview, Carol Stoker, editor, 1989, pp. 309-324; paper presented at the Case for Mars III conference in Boulder, Colorado, 18-22 July 1987.

Leadership and America's Future in Space, Sally K. Ride, NASA, August 1987.

Piloted Sprint Missions to Mars, Report No. SAIC-87/1908, Study No. 1-120-449-M26, Science Applications International Corporation, November 1987.

Humans to Mars: Fifty Years of Mission Planning, 1950-2000, David S. F. Portree, Monographs in Aerospace History #21, NASA SP-2001-4521, NASA History Division, February 2001.

More Information

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