Humans on Mars in 1995! (1980-1981) (1)
01 October 2015 David S. F. Portree
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: NASANASA's Space Shuttle was conceived in the late 1960s as a fully reusable transport spacecraft for reducing the cost of Earth-orbiting space station logistics resupply and crew rotation. By the time of the first piloted moon landing in July 1969, it came to be seen as an element in an expansive Integrated Program Plan that also included upgraded expendable Saturn V rockets, reusable manned Space Tugs and Nuclear Shuttles, Earth-orbital and lunar-orbital space stations, a lunar surface base, and manned Mars expeditions - all by the mid-1980s. This vision of America's future in space found little favor in either the Executive Branch or Congress, however. By 1972, only the Space Shuttle survived, and then only in a partially reusable form.
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: NASAWhen 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.orgTwo 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.orgThe 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.