|Space: 1995? A stylized schematic of NASA's Integrated Program Plan scenario, proposed in 1969, in the form it might have taken in the 1990s. Image credit: NASA|
For a time, the European Space Research Organization (ESRO) sought to provide NASA with a reusable Space Tug that would reach low-Earth orbit in the Shuttle Orbiter's payload bay and travel to orbits that the Shuttle could not reach. In August 1973, however, NASA and ESRO agreed that the latter should develop Spacelab, a system of segmented pressurized modules and unpressurized pallets that would operate in the Orbiter's payload bay to provide an interim short-duration space station capability. ESRO joined with the European Launcher Development Organization to form the European Space Agency (ESA) in 1975.
|Concept art of Space Shuttle Orbiter with cutaway of European-built Spacelab module in its payload bay. Image credit: NASA|
When the semi-reusable Shuttle first reached space in April 1981, NASA anticipated launching Earth-orbiting satellites and planetary probes beyond the Orbiter's operational altitude using a modest flock of expendable auxiliary rocket stages. The largest and most powerful of these would be the Centaur G-prime, a chemical-propulsion stage with a troubled development history. Centaur G-prime was tapped as NASA's main upper stage for boosting planetary probes – for example, the Galileo Jupiter Orbiter and Probe – onto interplanetary trajectories.
During Shuttle development in the 1970s, NASA budgets were tight, and planning for advanced missions - for example, humans on Mars - ceased within the U.S. civilian space agency. According to some within NASA, talk of moon bases and piloted Mars missions was tantamount to professional suicide. When planning for NASA piloted Mars missions resumed, it did so first outside of NASA. Mars exploration advocates outside the agency hoped that the Shuttle would inexpensively launch Mars spacecraft components, propellants, and crews, and also serve as a source of hardware that could be modified at modest cost to assemble piloted Mars spacecraft.
Robert Parkinson, an engineer with the Propellants, Explosives, and Rocket Motor Establishment in Great Britain, was among the first individuals to write about a NASA piloted Mars mission based on Shuttle and Shuttle-related hardware. Inspired by the writings of Arthur C. Clarke and Wernher von Braun, Parkinson had joined the British Interplanetary Society in 1956. In a series of papers spanning 1980-1981, he wrote of a capable chemical-propulsion NASA Mars expedition plan which he dubbed "Mars in 1995!"
Parkinson inventoried Shuttle-derived and Shuttle-related hardware which he believed would become available by 1990 as part of NASA's planned Earth-orbital operations. Development of such systems, he opined, "probably only awaits freeing of funding currently tied up in [development of] the Shuttle."
His long list of useful hardware included, in addition to the Space Shuttle, three systems designed mainly for rocket propulsion: a powerful Heavy Lift Vehicle (HLV) capable of launching into low-Earth orbit payloads larger than the Shuttle Orbiter's payload bay could accommodate; a Heavy Boost Stage (HBS) roughly the size of the S-IVB stage NASA used in the late 1960s/early 1970s to launch Apollo spacecraft out of Earth orbit toward the moon; and a drum-shaped high-performance Orbital Transfer Vehicle (OTV) with an optional crew cabin.
Parkinson's inventory also included important systems not related to propulsion: an extendable solar array for generating up to 25 kilowatts of electricity; Spacelab modules capable of operating in free-flyer mode (that is, outside of a Space Shuttle payload bay); closed-cycle Space Station life-support systems; and androgynous docking units resembling those which linked together Soviet and American spacecraft during the July 1975 Apollo-Soyuz Test Project mission.
Because such systems would be developed for Earth-orbital operations regardless of whether NASA planned a Mars expedition, a Mars expedition which employed them could be carried out in the 1990s with essentially no development cost. The piloted Mars lander would be the only wholly new piloted spacecraft developed for the Mars expedition.
Parkinson placed the cost of his expedition at just $3.3 billion in his first "Mars in 1995!" paper, of which developing and testing the Mars lander would account for about $740 million. He raised the total cost to $4.844 billion in a subsequent paper, of which $2.359 billion would be spent on the lander. Even this higher cost figure was, he noted, only five times the cost of the twin robotic Viking missions which landed on and orbited Mars in 1976. He added that "given the right circumstances, it is actually cheaper to send men [to Mars] than to try to do the same thing with dozens of robot expeditions."
Parkinson's 1995 NASA Mars expedition would begin with eight Space Shuttle launches in September-October 1994. Reflecting early Shuttle-era optimism, Parkinson estimated that each of the eight weekly Shuttle launches would cost just $28.75 million. Assembly of the expedition's three Orbital Assembly (OA) spacecraft - in reality, a single spacecraft system launched from Earth orbit in three parts - would take place in a 400-kilometer-high circular Earth orbit. The eighth Shuttle Orbiter would deliver the five Mars astronauts and stand by to observe the beginning of their departure from Earth orbit. In the event of trouble before the beginning of Earth-orbit departure, the Shuttle could recover the Mars astronauts and return them to Earth.
|The view from Orbital Assembly 1: A rear-facing porthole displays the setting Sun and OA 2 and OA 3 during departure from Earth-orbit. OA 2 is the nearer of the two. From fore to aft, it comprises the docking module with stowed twin rectangular solar arrays; a Spacelab-derived crew module; an unpressurized pallet with extended medium-gain dish antennas; a Mars-orbit departure/Earth-orbit capture OTV; a Mars-orbit capture OTV; and a Heavy Boost Stage. OA3 from fore to aft comprises the Lander Module; a stores module; an OTV with a crew cabin; and a Heavy Boost Stage. Image credit: © David A. Hardy/http://www.astroart.org|
Two OAs, which Parkinson also designated "Orbiters," would at launch from Earth orbit each comprise an HBS, a pair of 30-ton OTVs (one for Mars orbit capture and one for Mars orbit departure/Earth-orbit capture), and a Spacelab-derived pressurized module with an aft-mounted unpressurized pallet and a forward-mounted androgynous docking unit. The Spacelab-derived modules would provide living and working space for the crew, as well as protection from the six solar flares Parkinson said the crew could expect during their 18-month Mars expedition.
Orbiter 1, with a crew of three and a mass at launch from Earth orbit of 211.3 metric tons, would have stowed on its unpressurized pallet a deployable six-meter-diameter high-gain dish antenna for high-data-rate radio communication with Earth and two 2.5-meter-diameter Venus atmosphere entry probes. Orbiter 2, with a mass of 210.9 metric tons and a crew of two, would include attached to its forward-mounted androgynous unit a 1750-kilogram cylindrical docking module with three unoccupied androgynous docking ports and two extendable solar arrays. Either Orbiter could support the entire crew in an emergency.
OA 3, the unmanned Lander Assembly (LA), would have at launch from Earth orbit a mass of only 193.5 metric tons. In addition to an HBS, it would comprise an OTV; a three-meter-diameter drum-shaped OTV crew cabin with an androgynous docking unit; a drum-shaped stores module; and the 7.6-meter-diameter, 15.98-metric-ton Lander Module, which would transport three astronauts from Mars orbit to a pre-selected landing site on the martian surface. The stores module would partially cover the Lander Module to shield it from meteoroids.
Parkinson's stores module had a central tunnel running from its aft-mounted androgynous docking unit - linked to the OTV/crew cabin - to its forward-mounted androgynous docking unit. The forward unit would link to the Lander Module's lightweight "skeleton" androgynous unit. The module would carry supplies for the expedition's Mars-bound leg; three 1225-kilogram automated Mars sample-returner landers; a 938-kilogram propulsion package that would enable one Mars sample-returner to change its orbital plane from near-equatorial to near-polar and back so that it could reach and return a sample from one of the martian polar ice caps; six 31-kilogram penetrator hard-landers; and a 473-kilogram Mars-orbiting radio-relay satellite to enable Mission Control on Earth to remain in continuous contact with the crew on the surface of Mars.
On 8 November 1994, the three OAs would ignite their HBS engines to begin Earth-orbit departure. Over the course of several revolutions about the Earth, they would fire the HBS rocket motors at their perigee (Earth-orbit low point) to raise their apogee (Earth-orbit high point). A maneuver at final apogee would tweak the plane of the expedition's Sun-centered Mars-intersecting orbit, then a final perigee burn would push the three OAs out of Earth's gravitational grip.
After escape from Earth, the OAs would cast off their spent HBSs and dock to form the Earth-to-Mars cruise configuration. The crew would first dock Orbiter 1 and Orbiter 2 nose-to-nose with the docking module between them. The LA OTV/crew cabin would undock from the stores module/Lander Module, then the former would dock at one of the docking module's lateral (side) ports. The stores module/Lander Module would dock automatically at the other lateral port, opposite the LA OTV/crew cabin. The crew would then extend the twin solar arrays mounted on the docking module. After they finished assembling their spacecraft, the five astronauts would have available 1125 cubic meters of living space.
The OAs would reach Mars on 10 June 1995. Shortly before arrival, the crew would retract the solar arrays to protect them from deceleration stress during the Mars capture maneuver. Orbiter 1 would undock from the docking module on Orbiter 2, and the LA OTV/crew cabin and stores module/Lander Module would both undock from the docking module lateral ports and redock with each other.
The two Orbiters would then ignite their Mars orbit capture OTV engines to slow down so that Mars's gravity could capture them into a 23,678-by-3748-kilometer Mars-centered orbit with a period of 13.5 hours. The single LA OTV would perform an identical maneuver. Parkinson proposed the high elliptical orbit as a propellant-saving measure; relatively loosely bound to Mars, it would enable an economical Mars escape when time came to begin the return to Earth.
|Parkinson's "Mars in 1995!" spacecraft in Mars orbit. Spacelab-derived crew modules are labeled "NASA" and "esa." Numerals on the twin Mars orbit departure/Earth-orbit capture OTVs identify the Orbiters of which they are part. The Lander Module is at upper right, docked with the stores module, which is in turn docked with the Orbiter 2 docking module. Extended solar arrays place the LA OTV/crew cabin (labeled "3") in shadow. The painting shows a deorbit rocket pack strapped to the Lander Module heat shield; Parkinson also proposed using the Lander Module Reaction Control System thrusters for the deorbit maneuver ahead of landing on Mars. Image credit: © David A. Hardy/http://www.astroart.org|
The two Orbiters would cast off their spent Mars orbit capture OTVs and redock to form their Mars orbital configuration. The Lander Assembly would split as before so that its components could resume their places at the docking module lateral ports. Because the Lander Assembly would be less massive than the two Orbiters, its OTV would retain about 7000 kilograms of nitrogen tetroxide/hydrazine propellants after its Mars orbit capture burn and would not be cast off.
After they surveyed prospective landing sites from orbit at periapsis (orbit low-point) over several days, the astronauts would ready the Lander Module for descent to Mars's surface. Three astronauts would strap into couches in its cramped ascent module capsule and undock from the stores module. At apoapsis (orbit high-point), they would fire the Lander Module's Reaction Control System thrusters to lower its periapsis to 50 kilometers, where Mars atmosphere entry would begin. A bowl-shaped heat shield modeled on the Viking lander aeroshell design would protect the Lander Module during its fiery descent through the thin martian atmosphere.
The Lander Module would slow to Mach 2.5 by the time it fell to an altitude of 10 kilometers, then a 20-meter-diameter ballute ("balloon-parachute") would deploy to slow it to subsonic speed. Five kilometers above Mars, the ballute would separate and a parachute would deploy. At the same time, the Lander Module heat shield would fall away, exposing its four landing engine clusters and three landing legs. A downward-pointing camera would enable the Lander Module pilot to observe the planned landing site for the first time since leaving Mars orbit. The landing engines would ignite 800 meters above Mars; then, moments later, the parachute would separate. The pilot would then guide his craft to a safe landing.
Parkinson's Lander Module design, which resembled conical lander designs put forward beginning in the mid-1960s, included in its lower section a two-by-three-meter crew cabin. Soon after landing, the crew would climb down through a tunnel into the cabin and don Mars surface suits. After depressurizing the crew cabin, they would open a door-like hatch, walk down a short ramp, and put the first human boot prints on another planet.
|At the Mars landing site. Image credit: © David A. Hardy/http://www.astroart.org|
Parkinson called for a 20-day Mars surface stay, during which the three astronauts would explore using 500 kilograms of science equipment and a 500-kilogram unpressurized electric-powered rover more capable than the Lunar Roving Vehicle used during the Apollo 15, 16, and 17 missions. As they explored, they would collect up to 350 kilograms of Mars rock and dirt samples for return to laboratories on Earth.
The two astronauts on board the docked OAs, meanwhile, would deploy the mission's cargo of automated Mars probes. The 2.5-meter-diameter automated sample-returners would each collect and launch up to a kilogram of rock and soil (ice, in the case of the polar sample-returner) into a 350-kilometer circular Mars orbit.
When the time came to leave Mars's surface, the three astronauts would resume their places in the Lander Module ascent capsule and ignite three engines similar to the Apollo Lunar Module ascent-stage engine. The ascent capsule would blast free of the Lander Module's lower section, leaving behind the crew cabin. During the first-stage burn, four strap-on propellant tanks would feed the three engines. After first-stage shutdown, the tanks and two outer engines would detach; then, after a brief coast, the remaining engine would reignite to place the ascent capsule into a 350-kilometer circular Mars orbit.
As the docked OAs neared apoapsis, one astronaut would board the Lander Assembly OTV/crew cabin and undock from the docking module, then would ignite the OTV's rocket engine to descend to a rendezvous with the Lander Module ascent capsule.The OTV/crew cabin would link up with the ascent capsule, then the surface crew would transfer with their Mars samples.
After the Lander Module ascent capsule was cast off, the OTV/crew cabin would rendezvous with and recover the three orbiting sample-returner sample capsules. The OTV/crew cabin pilot would then fire its engine at periapsis to raise its apoapsis so that it could return to the docked OAs. Parkinson calculated that, even after this series of maneuvers, the OTV/crew cabin would retain enough propellants for two astronauts to carry out a 10-day sortie to Phobos, Mars's innermost and largest moon.
On 25 July 1995, the expedition would depart Mars orbit. Before departure, the astronauts would cast off the OTV/crew cabin and depleted stores module, retract the twin solar arrays, and undock Orbiter 1 from Orbiter 2. Each would then ignite its remaining OTV engine at periapsis to escape Mars orbit and begin a five-month journey to Venus. After OTV shutdown, the crew would redock the two Orbiters and extend the solar arrays. With the stores module gone, the astronauts would rely on supplies packed along the walls of the Spacelab-derived crew modules; these would have served as radiation shielding during the Mars-bound voyage and in Mars orbit.
The Venus detour, Parkinson explained, would accelerate the spacecraft toward Earth. Without the gravity-assist from Venus, the round-trip Mars voyage would need three years; with it, the Mars expedition could be completed in half that time. During the Venus swingby, the crew would deploy the twin Venus probes mounted on Orbiter 1's unpressurized pallet. The probes would be modeled on the Large Probe from the 1978 Pioneer Venus Multiprobe mission.
NASA's first Mars expedition would return to Earth 10 months after departing Mars, on 16 May 1996. The astronauts would again undock the Orbiters and retract the twin solar arrays on the Orbiter 2 docking module. They would ignite the OTV engines for the final time to capture into a 77,687-by-6800-kilometer Earth orbit with a period of 24 hours, then would redock and extend the solar arrays.
A Space Shuttle Orbiter, meanwhile, would transport into low-Earth orbit an OTV/crew cabin, which would climb to a rendezvous with the waiting Mars spacecraft and dock with the docking module. The Mars crew would board with their samples, then the OTV/crew cabin pilot would undock and fire his craft's motor to return to the waiting Shuttle Orbiter. The abandoned docked OAs would remain in Earth orbit as a long-lived monument to the early days of U.S. piloted Solar System exploration. The Shuttle Orbiter would deorbit to deliver the Mars astronauts, physically weakened by 18 months in weightlessness, to a hero's welcome on Earth.
NASA human spaceflight would follow a path very different from any Parkinson and other optimistic early 1980s space planners anticipated, though until early 1986 they could be forgiven for holding onto their dreams. In July 1982, President Ronald Reagan declared the Space Shuttle operational. The first Spacelab flight, STS-9/Spacelab 1 in late 1983, saw an ESA astronaut join American astronauts in Earth orbit for the first time. In his January 1984 State of the Union address, Reagan called for a Space Station and invited European, Canadian, and Japanese participation. The Shuttle-launched station was to be completed by 1994.
Reagan's station was meant to serve as a relatively low-cost laboratory. Such an orbital facility would have no need of the heavy-lift rockets, large in-space stages, and OTVs Parkinson had assumed would become available by 1990. NASA hoped that the lab station might be designed as a foot in the door leading eventually to a more ambitious and costly "shipyard" station, but the January 1986 Challenger accident meant that such schemes came under close scrutiny and were found wanting. At the same time, systems such as the Centaur G-prime stage were judged to be too volatile to carry on board a piloted spacecraft.
The cost of Shuttle operations was also a major factor in the death of optimistic early 1980s space plans. The Nixon Administration had made decisions that ensured low Shuttle development cost and high operations cost. NASA, a part of the Executive Branch, felt obligated despite this to continue to tout Shuttle economy.
The U.S. space agency was, however, cagey about how much it actually spent on Shuttle missions. For a time, a figure of $110 million per flight was used in Shuttle payload cost calculations. Independent cost estimates placed the per-flight cost of the Shuttle as high as $1.5 billion; even assuming that the true cost was "only" $1 billion per flight, the Earth-to-orbit transportation cost of Parkinson's Mars expedition would have reached $9 billion, or about double his highest cost estimate for his entire expedition.
The third, fourth, and fifth images of this post are © David A. Hardy/http://www.astroart.org. Used by kind permission of the artist.
"Is Nuclear Propulsion Necessary? (or Mars in 1995!)," AIAA-80-1234, R. Parkinson; paper presented at the AIAA/SAE/ASME 16th Joint Propulsion Conference in Hartford, Connecticut, 30 June-2 July 1980
"Mars in 1995!" R. Parkinson, Analog Science Fiction/Science Fact, June 1981, pp. 38-49
"A Manned Mars Mission for 1995," R. Parkinson, Journal of the British Interplanetary Society, October 1981, pp. 411-424
"Mars in 1995!" R. Parkinson, Spaceflight, November 1981, pp. 307-312