In July 1968, NASA's Apollo Applications Program (AAP) was undergoing another of its annual deep budget cuts. Despite this broad hint that ambitious post-Apollo space projects were unlikely to receive support, NASA continued its plans for a post-AAP Saturn V-launched Space Station that would serve many different experiment disciplines. The Space Station, which would remain operational for long enough to be considered "permanent," would measure 33 feet in diameter and carry a six-to-nine-man crew. NASA also planned a new piloted spacecraft for economically hauling crews and cargoes to and from its large station. This was widely expected to take the form of a reusable winged or lifting-body shuttle.
Against this backdrop, some engineers proposed lower-cost alternative station concepts. Bellcomm planners E. Marion and J. Schelke, for example, proposed in a 23 July 1968 memorandum that Titan-IIIM rockets be used to launch a series of four temporary "specialist" stations in place of NASA's single multidisciplinary station. The Titan-IIIM was under development for the U.S. Air Force Manned Orbiting Laboratory (MOL) program, which was intended to rely heavily on modified Gemini spacecraft. At the time, Gemini was a recently completed NASA program; Gemini XII, the last mission in the series of 10 piloted Gemini flights, had ended with a splashdown in the Atlantic Ocean on November 15, 1966.
The authors cited an April 1968 study, which had asserted that NASA's proposed large Space Station would suffer from delays in the development of its complex multidisciplinary experiment program and its new logistics spacecraft. This would push its launch to the mid-1970s, well beyond AAP's expected conclusion, creating a gap of several years in NASA piloted flights. The study had also found that the large station's diverse experiment program would generate requirements conflicts. For example, some experiments would need to operate in a low-altitude orbit to be effective, while others would need a high-altitude orbit.
Furthermore, the Saturn V-launched large Space Station probably could not serve a military surveillance role. This was because placing it into a low-altitude near-polar or polar orbit - the best orbit for observing and imaging installations and activities all over Earth's surface - would risk dropping the Saturn V's spent S-IC first stage on Cuba (for southward launches) or New York City (for northward launches).
Marion and Schelke wrote that "the most important job" for their specialist station program would be to permit NASA "to gain experience with long term manned space flight." They proposed four basic missions, each of which would include "Man-in-Space" experiments that would gather biomedical data in support of long-term space missions.
In 1968, "long term manned space flight" was a code phrase for piloted Mars voyages, a long-held NASA objective that had become a lightning rod for Congressional hostility following the Apollo 1 fire (27 January 1967). The Bellcomm planners thus hastened to add that long-term space experience "by itself could not justify a complete program" - that is, if NASA was to make any station program "worthwhile," it would need to fly other experiments.
Marion and Schelke assumed that AAP would demonstrate that astronauts could remain healthy in orbit for up to 60 days and that medical assessments would show that stay-time in orbit could be progressively doubled beginning with the first crew of their program (Mission 1 Crew 1). Returning astronauts would need to pass a 30-day medical assessment before further stay-time doubling could be authorized. The overriding program goal would be to maintain a single two-man crew in Earth orbit for 730 days (two years).
Mission 1, which they called the "Earth-Looking/Man-in-Space/Biology" mission, would commence in mid-1974 and would last for up to 29 months. Mission 1 station assembly would require two manned Titan-IIIM launches to a 125-nautical-mile-high orbit inclined 60° relative to Earth's equator - an orbit determined by the mission's Earth observation emphasis. The orbit's high inclination would enable the specialist station to fly over every spot in the latitude band between 60° north and 60° south, and its low altitude would place observation targets on Earth's surface close at hand.
One Titan-IIIM could launch 36,000 pounds to Mission 1's operational orbit. For both Mission 1 assembly launches, the payload would comprise a 6800-pound Gemini-B bearing two men and a two-deck specialist station module. In place of Gemini's twin ejection seats, the Gemini-B would include a launch escape tower with tractor motors on top for pulling it away from a malfunctioning booster. The station modules would measure 17 feet long.
Each specialist station module would have a diameter greater than the Titan-IIIM core upon which it rode (15 feet versus about 10 feet). This meant that the module would form a "hammerhead" payload atop its booster. The Bellcomm planners noted that The Martin Company, builder of the Titan family of missiles and space launch vehicles, had determined that this configuration would be feasible. From the bottom of its twin solid-rocket boosters to the top of the Gemini-B escape tower, the Titan-IIIM and its specialist station payload would stand a little more than 140 feet tall.
Mission 1's first module, a 21,200-pound Control Cabin, would carry communications & data management systems and guidance & control systems. The latter would include control-moment gyros for attitude control and rocket motors and tanks holding 2600 pounds of propellants for "orbit-keeping." The module would also contain living quarters with a 1000-pound "crew system," 2,500 pounds of food (all that would be required for the station module's lifetime), and 2500 pounds of Earth-pointing sensors, bringing the total launched mass to 33,400 pounds. This would leave a 2900-pound "payload margin" for weight growth during development.
Upon reaching Earth orbit, the Mission 1 Crew 1 astronauts would open a hatch above and behind their seats and clamber through a hatchway in the Gemini-B heat shield into the top deck of the Control Cabin. There they would activate systems, including the Brayton/Isotope (B/I) generator that would supply the module's electricity. Marion and Schelke opted for a nuclear power source because it would eliminate the atmospheric drag and station-orientation restrictions inherent in wing-like solar arrays.
The authors estimated that a three-kilowatt B/I generator for a single-module station would have a mass of 2405 pounds; the equivalent for a multiple-module station with a B/I generator in each module would have a mass of only 2125 pounds. This was because the latter could dispense with redundant parts; if one B/I unit failed, one in another module could step in to provide redundancy. The single- and multiple-module B/I systems would each include a 480-pound nuclear fuel block, an emergency reentry heat shield, recovery aids, and abort rocket system with a total mass of 420 pounds, and 150 pounds of spare parts.
Along with the B/I system, Mission 1 Crew 1 would activate the Control Cabin's life support systems. Marion and Schelke assumed that all air and water would be recycled. Stored life support consumables would be used only to make up for leakage and would not be replenished during the lifetime of the specialist station. To avoid electricity-hungry cryogenic storage systems, oxygen and nitrogen in the station atmosphere would be derived respectively from water and ammonia, both of which have high boiling temperatures. Waste heat from the B/I unit would drive part of the recycling system, reducing total life support power usage to a single kilowatt.
Mission 1's second specialist station module, the 18,300-pound Experiment Cabin, would reach orbit a month after the Control Cabin. One deck of the Experiment Cabin would carry 8700 pounds of Man-in-Space and Biology experiment gear, while the other would house the two Mission 1 Crew 2 astronauts. As was the case with Mission 1 Crew 1, they would be launched in a Gemini-B atop their specialist space station module. Crew quarters in the Experiment Cabin would lack a full-body zero-G shower, but otherwise would not differ from those in the Control Cabin. Like the Control Cabin, the Experiment Cabin would carry 2500 pounds of food. Experiment Cabin mass would total 33,800 pounds, leaving a 2200-pound payload mass margin.
The two Gemini-B/specialist station module combinations would be docked tail-to-tail to form the complete Mission 1 specialist station. This would place the twin Gemini-B spacecraft at opposite ends of the station.
Marion and Schelke proposed an unmanned expendable logistics resupply spacecraft derived from the Gemini Program's Agena rendezvous-and-docking target vehicle. The system would comprise a modified Agena stage, a propellant resupply section, a docking structure, and an Earth atmosphere reentry capsule.
Ninety days after the Control Cabin reached orbit, the first logistics resupply vehicle would lift off atop an Atlas-derived rocket. The crew would remotely guide the resupply vehicle to a docking at one of the Control Cabin's two side ports. They would pump 2900 pounds of propellants from the resupply vehicle into the Control Cabin's orbit-keeping propulsion system tanks, then would discard the Agena and the propellant resupply section. This would leave the docking structure containing the reentry capsule attached to the specialist station.
The crew would remove 1300 pounds of experiment supplies from the capsule, refill it with experiment products (for example, exposed photographic film and biological samples), then seal it and eject it from the frame-like docking structure. The capsule would fire small solid-propellant rocket motors to deorbit and reenter Earth's atmosphere for recovery. Finally, the astronauts would discard the empty docking structure. Logistics flights would take place every 90 days throughout each station's career.
The Bellcomm engineers looked at several methods for reaching their program's 730-day stay-time goal. In one example, Mission 1 Crew 1 would remain in orbit for 120 days, then would return to Earth for a 30-day medical assessment. Two Mission 1 Crew 3 astronauts would arrive to replace them in a Gemini-B launched on a standard Gemini-Titan rocket. The Gemini-B would back up to dock with the Control Cabin docking port the Mission 1 Crew 1 Gemini-B had vacated. If doctors on Earth found Mission 1 Crew 1 to be healthy after their 120 day stay, then the astronaut pair launched with the Experiment Cabin (Mission 1 Crew 2), by then in orbit for 120 days, would be cleared to stay in space for a further 120 days, bringing their total stay-time to 240 days.
Meanwhile, Mission 2, the "Astronomy/Advance Technology/Man-in-Space" mission, would commence. The first of the three modules making up the Mission 2 station, a Control Cabin, would ascend to a 200-nautical-mile, 28°-inclination-orbit 60 days after Mission 1 began. The Titan-IIIM could boost 35,500 pounds to Mission 2's operational orbit. The 21,200-pound Mission 2 Control Cabin would carry 4100 pounds of technology experiments and 1300 pounds of propellants. With the attached Gemini-B bearing Mission 2 Crew 1, its total mass would come to 33,400 pounds, leaving a 2100-pound payload margin.
The second Mission 2 module, an 18,300-pound Experiment Cabin, would lift off nearly simultaneously from a second Titan-IIIM launch pad built at Cape Kennedy specifically for Marion and Schelke's station program. In addition to the Gemini-B bearing Mission 2 Crew 2, the second Titan-IIIM would launch the Mission 2 Experiment Cabin with 4000 pounds of Man-in-Space experiments and 5500 pounds of life-support experiments on board, giving it a hefty total mass to 34,600 pounds. This would leave a slim 900-pound payload margin. The Mission 2 Control and Experiment Cabins would dock in orbit, forming a second four-man specialist station outwardly identical to the first.
One or two months later - following refurbishment of one of the two Titan-IIIM pads - NASA would launch a third Mission 2 Titan-IIIM bearing a new type of module called an Experiment Shell. The stripped-down 12,100-pound module, launched unmanned with no Gemini-B attached, would house 18,200 pounds of astronomy gear, bringing its total mass to 30,300 pounds. This would leave a 5200-pound payload margin. Prior to its arrival, the Experiment Cabin crew (Mission 2 Crew 2) would transfer their Gemini-B to one of the pair of side-mounted docking ports on the Experiment Cabin to make way for the Experiment Shell, which would dock in its place. The crew would then expose the Experiment Shell's telescopes by casting off a protective shroud.
Mission 1 Crew 2 would return to Earth after 240 days in orbit and undergo a 30-day medical assessment. If they passed, then the two-man crew launched with the Mission 2 Control Cabin (Mission 2 Crew 1), already in space by then for seven months, would be cleared to remain in orbit for a total of 480 days (18 months). Meanwhile, two more astronauts (Mission 1 Crew 4) would arrive in a Gemini-B to replace Mission 1 Crew 2.
When Mission 2 Crew 1 reached 480 days in orbit, they would return to Earth for their 30-day medical assessment. Mission 2 Crew 3, the final crew scheduled to be launched to the Mission 1 or Mission 2 stations, would replace them. Assuming that Mission 2 Crew 1 passed medical muster, then the two astronauts that arrived with Mission 2's Experiment Cabin (Mission 2 Crew 2) would be authorized to remain in orbit for 730 days. They would reach the specialist station program's stay-time goal of 24 months just 26 months after the launch of Mission 1 Crew 1.
Meanwhile, the four astronauts on board the Mission 1 station would return to Earth simultaneously in their respective Gemini-Bs. Mission 1 Crew 3 would return after 600 days, while Mission 1 Crew 4 would have chalked up 450 days. The Mission 1 station, having reached the end of its design lifetime, would then be deorbited over an uninhabited region.
Two months later, Mission 2 Crew 3 would return to Earth at the same time as Mission 2 Crew 2. The former would have spent 240 days in space. The Mission 2 station, having also reached the end of its design lifetime, would then be deorbited.
Marion and Schelke provided fewer details for Mission 3, which they dubbed the "Physical Sciences/Man-in-Space" mission. It would begin in the third quarter of 1975 with the launch of two astronauts in a Gemini-B atop a 21,200-pound Control Cabin bearing 4000 pounds of Man-in-Space experiments and 1300 pounds of propellants.
The authors made no mention of crew rotation during Mission 3; the astronauts launched in the Gemini-B with the Mission 3 Control Cabin would apparently remain on board until the third quarter of 1977, their stay-time progressively extended as crews on board the four-man stations reached new stay-time milestones and were found to be healthy after they returned to Earth.
A month after the Mission 3 Control Cabin reached space, a 14,300-pound Experiment Shell with a B/I generator and 14,000 pounds of physical science experiments would arrive. Two months after the Experiment Shell arrived, the crew would remotely pilot a logistics resupply spacecraft to a docking with the station. After transferring its propellants and unloading its cargo, they would use its reentry capsule to return to Earth the first materials samples from their physical science experiments.
Marion and Schelke noted that Mission 3's science program would not be orbit-dependent (its altitude could, they wrote, "be anything"). They chose a 200-nautical-mile-high orbit inclined 28° to Earth's equator. The station's relatively high altitude would minimize required orbit-keeping propellants, while 28° was Cape Kennedy's latitude and thus the orbital inclination most easily achieved by rockets launched from that site.
The Bellcomm engineers did not include Mission 4, the MOL-like "Military Mission," in their mission schedule. They explained that, "by edict" of the U.S. Air Force, the Military Mission would require only a single launch. A Titan III-M would launch a Control Cabin with an attached piloted Gemini-B into a 100-nautical-mile-high orbit inclined 90° relative to Earth's equator. This would take the Mission 4 station over both of Earth's poles during each orbit and enable it to overfly Earth's entire surface every 24 hours. They envisioned a two- or four-month duration for the Military Mission.
Marion and Schelke briefly discussed their views on mission safety. They wrote that "[s]omeone is bound to notice" that their station lacked redundant crew Earth-return vehicles; that is, that its crews would have available to them for emergency Earth return only the Gemini-B spacecraft in which they had reached space. In their view this was not, however, a serious problem. If a station disaster meant that the astronauts could not reach their Gemini-B through normal means (that is, through the heat shield hatch), then they could reach it by spacewalking outside the station. If their Gemini-B failed while it was attached to the station, then they could discard it and extend their station stay until a new Gemini-B could be launched unmanned to the station.
The Bellcomm engineers provided a cost breakdown and spending schedule for their specialist station program. In 1969, the program's first year, NASA would spend $29 million to begin experiment hardware development. The following year, it would spend $42 million to start specialist station module development. Construction of the new Titan-IIIM launch pad at Cape Kennedy would commence in 1971. In that same year, NASA would spend $64 million to begin Gemini spacecraft modifications. In 1972, the program's peak funding year, NASA would spend a total of $787 million, bringing the total spent since program start to $1.361 billion.
The year 1973 would see peak funding for specialist station module development ($396 million); that same year, NASA would complete the new Titan-IIIM launch pad and modifications to Cape Kennedy's existing Launch Complex 41 Titan-III pad. Titan-IIIM launches in 1974 and 1975 would cost a total of $48 million. In all, NASA would spend $2.559 billion between 1969 and 1977 to fly the four specialist stations.
Eleven months after Marion and Schelke completed their specialist space station program proposal, Melvin Laird, President Richard Nixon's Secretary of Defense, announced that the increasingly costly U.S. Air Force MOL program would be scrapped (10 June 1969). This effectively ended plans to use Gemini spacecraft for new missions. NASA launched Skylab, the last vestige of AAP, atop the last Saturn V to fly on 14 May 1973. Three three-man crews reached Skylab on board Apollo Command and Service Module spacecraft. The last, the Skylab 4 crew, remained aloft for 84 days, a U.S. space endurance record not beaten until Norman Thagard lived on board the Russian Mir space station for 115 days in 1995.
Reference:
A Titan-IIIM Launched Space Station Program - Case 710, E. Marion and J. Schelke, Bellcomm, Inc., 23 July 1968.
