Please note: This post is based on a reader comment on my last post. Please feel free to suggest possible posts; I can't guarantee that I'll write them immediately, but at least they'll shape my thinking about the direction this blog takes.
Probably the record for the smallest space station design ever proposed belongs to the One-Man Space Station that McDonnell Aircraft, makers of the Mercury spacecraft, presented on 24 August 1960 to the Space Task Group (STG) at NASA's Langley Research Center (LaRC) in Hampton, Virginia. The station, a pressurized 10-foot-long, six-foot-wide cylinder with dome ends, was meant to be launched with a Mercury and an Agena B restartable upper stage into a 150-nautical-mile-high Earth orbit inclined 30° relative to the equator. The Mercury/station/Agena B combination would have lifted off from Earth atop an Atlas D rocket similar to that tapped to launch standard Mercury orbital missions. The Agena B would have completed orbit insertion and retained enough propellants to maneuver itself, the station, and the attached Mercury in orbit.
One might be excused for calling the station a Mission Module for expanding Mercury spacecraft capabilities rather than a bona fide space station. It was meant to be used for 14 days by the single astronaut launched with it in the Mercury spacecraft, then permanently abandoned after the astronaut separated from it in the Mercury and returned to Earth.
The STG that heard McDonnell's presentation shared some traits with the proposed One-Man Space Station: it was small and meant to be temporary. The group was founded on 5 November 1958, a little more than a month after NASA opened for business. Its aim was to accomplish Project Mercury, the first U.S. piloted space program. President Dwight Eisenhower took a dim view of "space stunts" such as piloted spaceflight, but had acquiesced to calls from Congress and public to attempt to launch men into space before the Soviet Union did. He made no commitment to piloted spaceflight after Mercury. Eisenhower insisted that Project Mercury be conducted as a civilian enterprise to keep it separate from the serious military business of developing battlefield and intercontinental missiles and launching reconnaissance and early-warning satellites.
It seems probable that the One-Man Space Station was a civilian iteration of a proposed piloted spy satellite. With its integral Agena B stage for Earth-orbit injection and orbital maneuvers and its separable Mercury spacecraft for Earth return, McDonnell's station outwardly resembled the Discoverer series satellites first launched in January 1959. Discoverer was a cover designation for Corona spy satellites. The Discoverer/Corona satellites employed an integral Agena for injection and maneuvers and a capsule for film return.
A piloted spy satellite might have begun to seem attractive in mid-1960 because the automated Discoverer/Corona satellites suffered failure after failure during their first 20 months. Not until Discoverer 14 - launched on 18 August 1960, just six days before McDonnell's presentation to the STG - did Discoverer/Corona succeed in returning to Earth a capsule containing exposed film showing Earth-surface targets.
The One-Man Space Station would have enclosed 282 cubic feet of volume, of which 182 cubic feet would have constituted living and working space. The astronaut would have worked inside the station in shirt-sleeves, not in a pressure suit. A "laboratory test payload" would have taken up 40 cubic feet of the interior, and support equipment - for example, life support gear and fuel cells capable of producing up to 1500 watts of electricity - would have filled up 60 cubic feet of volume at the domed "bottom" end of the station.
McDonnell proposed two designs for its One-Man Space Station. The manner by which the astronaut would move between the attached Mercury and the cylindrical station distinguished the two designs. The "Tunnel Access" design would have required fewer modifications to the Mercury spacecraft than the "Hinged Lab" design. The former would have included an inflatable tunnel launched under a metal cover or faring; upon reaching orbit, the astronaut would have inflated the tunnel, linking his craft's standard-design 24-inch Mercury side hatch with a 24-inch hatch on the side of the station. The metal cover would have remained attached to the tunnel to stiffen and partly shield it from meteoroids. The Hinged Lab design would have seen the Mercury pivot on a hinge to link a modified side hatch with a hatch on the side of the station.
For return to Earth, the astronaut on board the Tunnel Access station would have donned his protective pressure suit, returned to his cramped seat in the Mercury spacecraft, sealed the Mercury hatch, and fired pyrotechnic bolts or cord to sever the inflatable tunnel. He would then have separated his Mercury spacecraft from the station, turned it end for end so that its broad aft end faced in its direction of motion, and ignited a single solid-propellant retrograde motor to slow his spacecraft and begin atmosphere reentry.
The astronaut on board the Hinged Lab station also would have sealed the Mercury hatch, then would have returned his Mercury spacecraft to Earth launch position at the front of the station/Agena combination. He would have fired explosive bolts to separate the Mercury from the hinged adapter linking it to the station, then would have turned his spacecraft end over end and ignited the retrograde motor.
The presence of the Agena B stage enabled McDonnell to delete the standard Mercury spacecraft's 24-pound posigrade motor set, which in normal Mercury flights would have ignited to separate the spacecraft from its Redstone or Atlas booster. Other modifications included the new hatch design, which would have added 16 pounds to both the Tunnel Access and Hinged Lab designs; deletion of the astronaut-monitoring camera from the telemetry & recording system (a savings of 28 pounds); addition of seven pounds of water to the Mercury environmental control system; provisions for return to Earth in the Mercury spacecraft of 28 pounds of experiment results; and a new adapter for linking the Mercury with the "top" of the station (an addition of 97 pounds for the Tunnel Access design, which needed a relatively simple adapter, and 129 pounds for the more complex Hinged Lab adapter).
The station portion of the One-Man Space Station would have weighed 3344 pounds in the Tunnel Access case and 3309 pounds in the Hinged Lab case. The Hinged Lab station would have included 20 pounds more structure than the Tunnel Access station (presumably to support its modified hatch) and 22 pounds of additional attitude-control propellant (necessary because of the difficulties of stabilizing the out-of-balance side-mounted Mercury configuration). The Tunnel Access station, for its part, would have included the 50-pound faring covering the inflatable tunnel and an additional 135 pounds for the tunnel itself.
In its 24 August 1960 presentation to the STG, McDonnell Aircraft estimated that the Atlas D and Agena B upper stage could inject 6076 pounds into orbit. Subtracting the weight of the modified Mercury and the station left 1234 pounds for test & experiment equipment in the Tunnel Access station and 1342 pounds in the Hinged Lab station. The company listed as One-Man Space Station research projects the study of human adaptation to 14-day weightless spaceflights; study of "long-time equipment performance" on spacecraft; "lunar probe navigation equipment" testing; radiation exposure, geophysical, and astrophysical measurements; and development of space rendezvous techniques, presumably using the restartable Agena B rocket motor.
McDonnell also suggested that One-Man Space Stations might carry out specialized missions: for example, one station might be devoted communications research, while another might serve as a dedicated astronomical observatory; yet another might make possible detailed observations of Earth's weather. It also suggested that a One-Man Space Station might revert to the design's likely original purpose: that is, Earth-surface reconnaissance.
Reference
One Man Space Station, McDonnell Aircraft, 24 August 1960.
