|Modular Shuttle-launched Station in the 1980s. Image credit: NASA|
Both companies looked at 33-foot-diameter, barrel-shaped "monolithic" stations. These were designed to be launched in one piece into low-Earth orbit atop a two-stage Saturn V rocket. Both companies assumed that a logistics vehicle - commonly called a Space Shuttle - would resupply the Station, rotate its six-to-12-man crews, deliver experiment equipment and small experiment modules, and return experiment results and experiment modules to Earth.
|Plan drawing of NAR's Phase B "monolithic" Space Station design. Image credit: NAR/NASA/DSFPortree|
In January 1970, as negotiations toward the Fiscal Year (FY) 1971 NASA budget got under way between NASA, President Richard Nixon's White House, and the Congress, NASA Administrator Thomas Paine announced that, to accommodate proposed funding cuts, NASA's Saturn V rocket test and assembly facilities would be mothballed. He was not specific about when this would happen, stating only that it would occur after the last Saturn V ordered for the Apollo moon program - the fifteenth - was completed and tested. That was expected to occur before the end of 1971.
The Mississippi Test Facility at Bay St. Louis, home of test stands for Saturn V engines and rocket stages, would be hardest hit; from about 2000 its staff would shrink to 150-200 "caretaker" personnel. The industry publication Aviation Week & Space Technology explained in its 9 February 1970 issue that, if NASA proceeded with its Saturn V plans and then received funding for new Saturn Vs in its FY 1972 budget, it would need four years to restore its assembly and test capabilities. The first Saturn V after the last Apollo Saturn V would not launch before July 1975.
On 4 May 1970, the Space Station Task Force asked MSFC and MSC to direct MDAC and NAR to devote some attention during their Phase B studies - which were set to conclude in two months - to assessing a new method of launching the Space Station: specifically, by boosting it into Earth orbit in pieces in the payload bays of Space Shuttle Orbiters. At about the same time, MSC began to organize its Shuttle-launched modular Station study, which commenced officially on 1 June 1970.
One ground rule of the MSC study was that the modular Station should be able to accomplish the same research objectives as its monolithic counterpart. Another was that MSC should seek to "exploit the unique capabilities of multiple Shuttle launches."
By June 1970, NASA had, in exchange for U.S. Air Force political support, largely settled on a 15-foot-by-60-foot payload bay for its winged Shuttle Orbiter design. Engineers at its Houston center had, however, not yet fully reconciled themselves to these payload bay dimensions. Some sought a shorter - and sometimes wider - payload bay.
The modules they considered for their Space Station during June 1970 reflected this. They looked at five modules; then, in a second round of analysis, they emphasized four. The initial five measured 12 feet in diameter by 39.5 feet long; 12 feet in diameter by 29 feet long; 14 feet in diameter by 29 feet long; 16 feet in diameter by 22.2 feet long; and 18 feet in diameter by 17.4 feet long. The four "second-pass" modules measured 12.5 feet in diameter by 30 or 40.5 feet long; 14.5 feet in diameter by 30 feet long; 16.5 feet in diameter by 23.2 feet long; and 18.5 feet in diameter by 18.4 feet long.
|MSC's four "second-pass" circular floor plan Shuttle-launched Space Station Modules. Image credit: NASA with stick figures by DSFPortree|
|MSC's four "second-pass" horizontal floor plan Shuttle-launched Space Station Modules. In this image and the image above, the stick figures indicate the positions of the floors in the modules, not necessarily the presence of artificial gravity. Image credit: NASA with stick figures by DSFPortree|
Module design Concept Selection took place on 1 July. MSC chose a horizontal module 14 feet in diameter by 29 feet long, which could launch in a 15-foot-diameter Orbiter payload bay as short as 30 feet long.
MSC then used the selected module concept to create six modular Space Station configurations (shown below). Crews for five of the six would live and work in weightlessness. All six featured one Solar Power Boom with a pair of two-part solar arrays, one or two Central Assembly Elements (CAEs), eight Basic Structural Elements (BSEs), and two Expendables Storage Elements (ESEs). MSC calculated that these module combinations would provide roughly the same workspace as the four 33-foot-wide circular decks and the upper and lower equipment bays of the NAR monolithic Station design.
Four configurations MSC considered and then put aside are labeled 1 through 4 below. None includes an ESE, though the Shuttle-launched Station would not operate without one attached. The designs are of two classes: the BSE modules Configuration 1 and 2 BSE modules form arms and the Configuration 3 and 4 BSE modules form bundles. In Configurations 3 and 4, a single nadir-facing (Earth-facing) BSE module would be provided for Earth observation experiments.
On 15 July 1970, MSC engineers traveled to NASA Headquarters to brief the Space Station Task Group on its progress. They included in their presentation - which, being an interim product, contains its share of internal inconsistencies - the four designs they had put aside plus a preliminary artificial-gravity baseline design with a specialized telescoping CAE (fifth image above). Most of their presentation was, however, devoted to a preliminary assembly sequence for their baseline Shuttle-launched Station configuration (bottom image above - click to enlarge).
MSC expected that 14 Shuttle launches would be required to place their baseline modular Station into Earth orbit; that is, that NASA would need 14 Shuttle launches to replace a single two-stage Saturn V launch. Launch 1 of the Station Program would place into orbit a 20,412-pound CAE (labelled 1 in the drawing above) "core module" with nine ports (one on each end and seven on its four sides) and a pair of robot arms to facilitate module manipulation and attachment. Launch 2 would attach a 19,351-pound ESE (not shown) to a CAE "side" port, forming an "L"-shaped configuration. Though its length was not given, the ESE was meant to be shorter than the other module types. It would carry enough food to supply 12 men for 90 days.
Launch 3 would see a Shuttle Orbiter join the 19,154-pound Solar Power Boom (3) to one end of the CAE. After the Orbiter moved away, the Boom's solar arrays would unfurl. Launch 4 would place into space the first BSE, a 17,209-pound module containing the Station's main control and data processing facilities. It would be attached to the CAE port on the side opposite the ESE port. It is not shown in the baseline configuration illustration above; an outline of an arrow marks the port to which it would be attached. The Launch 4 BSE, a permanent module, would be the sole exception to the guiding principle that only temporary modules would attach to side ports.
Launches 5 through 8 would attach permanent BSE modules to ports perpendicular to the long axis of the ESE and Launch 4 BSE modules. Module placement would alternate between zenith (space-facing) and nadir CAE ports. Launch 5 would deliver a 20,605-pound BSE containing mainly life support and personal hygiene equipment (5). This would bring total Station mass to 96,731 pounds. Launch 6 would deliver a 20,302-pound BSE outfitted with crew staterooms and communications equipment (6). Launch 7, midway through the assembly sequence, would attach to the Station a lightweight 13,367-pound BSE containing crew recreation and dining facilities and a galley (7).
The Launch 8 module, a BSE dedicated to crew health (8), would also be a lightweight (13,324 pounds). Its arrival at the Station would mark completion of one of the modular Station's two redundant, independently pressurized volumes. MSC's modular Station would at that point be equivalent to two decks, an equipment bay, and the Solar Power Boom of the NAR monolithic Station design. Station mass would total 143,724 pounds.
Redundant, independent volumes reflected the Station's crew safety philosophy. If one volume became uninhabitable, the entire crew could retreat to the second volume to await an Orbiter that could provide repair assistance or rescue. The modular Station would not be permanently staffed until both volumes were completed.
Launches 9 through 14 would assemble the Station's second redundant, independent volume. This would be equivalent to an NAR monolithic Station equipment bay and two decks.
Launch 9 would see arrival of the 18,645-pound second CAE (9), which would be attached to the second end port of the first CAE. This would enable attachment of four more zenith- and nadir-facing BSEs to the modular Station. Launch 10's 16,395-pound BSE would include a maintenance shop and laboratory space (10), while Launch 11's 19,024-pound BSE would contain a general-purpose lab (11).
The Launch 12 BSE would provide backup control & data processing (12); like its twin delivered by Launch 4, it would weigh 17,209 pounds. The payload for Launch 13 would be a 15,756-pound BSE containing crew quarters (13).
Launch 14 would complete MSC's baseline modular Station. An Orbiter would arrive with a 20,551-pound ESE module containing the Station's first six long-term resident astronauts and food for 12 men for 90 days. Like the first ESE, the second ESE is not shown in the drawing above; it would, however, be attached to the side CAE port marked on the drawing by the outline of a star. With the addition of the 14th Shuttle payload, Station mass would total 251,304 pounds.
The image at the top of this post (click to enlarge) shows an advanced version of MSC's modular Station. The design is sometimes mistakenly attributed to MDAC. The advanced configuration, scheduled for assembly in the 1980s, would include at least five more BSEs than the baseline configuration. Four would link to the zenith and nadir ports of a third CAE attached to the second CAE. In the painting, an ESE makes an appearance: it includes a pair of robot arms. One of the four BSE modules attached to the third CAE is a dedicated nadir-facing Earth-observation module (an open round end-hatch and extended instruments are visible below the ESE arms).
Two BSEs are attached to the side CAE ports; one, nearest the Solar Power Boom, is the Launch 4 BSE, while the other, on the same side as the ESE, is probably a temporarily docked free-flyer with an independent propulsion system. This would detach from the Station periodically to provide a stable platform for materials science and astronomy experiments; such experiments could be adversely affected by vibrations caused by crew movement within the Station.
The approaching Shuttle Orbiter is an MSC design with straight wings a little more than 90 feet across, internal liquid oxygen and liquid hydrogen tanks, and a payload bay shorter than 60 feet. It bears a BSE module bound for a CAE side port. During flight to the Station, the module - probably another freeflyer - would be lifted from the payload bay and attached to a docking unit atop the Orbiter crew cabin. The Orbiter would move close to the Station, then dock with it through the intermediary of the module. When time came to return to Earth, the Orbiter would undock from the module, leaving it attached to the Station.
After its 15 July presentation at NASA Headquarters, the MSC team apparently halted its activities. The artificial-gravity baseline design, for example, seems not to have been developed further. I have found no evidence that briefings scheduled for 1 August and 7 September at MSC and 15 September at NASA Headquarters actually took place.
NASA extended the NAR and MDAC Space Station Phase B contracts by six months on 30 June 1970. On 29 July 1970, Charles Mathews, chair of the Space Shuttle Task Force, requested that MSC and MSFC instruct their respective Phase B Extension contractors to abandon all work on monolithic Saturn V-launched Station designs in favor of Shuttle-launched modular designs. When unveiled in 1971, the NAR modular design resembled the baseline design from MSC's May-July 1970 in-house study.
Shuttle-Launched Space Station Study Interim Review, NASA Manned Spacecraft Center presentation to NASA Headquarters, 15 July 1970
"Curtailing Field Centers Limits Saturn 5 Options," Aviation Week & Space Technology, 9 February 1970, pp. 26-27
"Space Station and Space Platform Concepts: A Historical Overview," J. Logsdon and G. Butler, History of Space Stations and Space Platforms - Concepts, Designs, Infrastructure, and Uses, I. Bekey and D. Herman, editors, Volume 99, Progress in Astronautics and Aeronautics, American Institute of Aeronautics and Astronautics, 1985, pp. 226-233
Space Shuttle: The History of the National Space Transportation System - The First 100 Flights, Third Edition, D. Jenkins, Specialty Press, 2008, pp. 101-108, 137
A Bridge from Skylab to Station/Shuttle: Interim Space Station Program (1971)
An Alternate Station/Shuttle Evolution: The Spirit of '76 (1970)
Apollo's End: NASA Cancels Apollo 15 & Apollo 19 to Save Station/Shuttle (1970)
McDonnell Douglas Phase B Space Station (1970)
Think Big: A 1970 Flight Schedule for NASA's 1969 Integrated Program Plan
"A True Gateway": Robert Gilruth's June 1968 Space Station Presentation