Evolution vs. Revolution: The 1970s Battle for NASA's Future

Sunlight glints off NASA Marshall Space Flight Center's proposed Power Module in this artist concept by Junior Miranda

According to historians Andrew Dunar and Stephen Waring, writing in their 1999 NASA-funded history Power to Explore: A History of Marshall Space Flight Center, in the 1970s two lines of thought emerged within NASA concerning manned spaceflight's course after the Space Shuttle became operational. On the one hand, there was the "revolutionary" line taken by Johnson Space Center (JSC) in Houston, Texas. On the other was the "evolutionary" line of NASA Marshall Space Flight Center (MSFC) in Huntsville, Alabama.

At JSC, many managers assumed that, as soon as the Shuttle became operational, NASA would get a green light to assemble a large, new-design, multipurpose Space Station in low-Earth orbit (LEO). They envisioned that a 1980s President would make a speech much like President John F. Kennedy's 25 May 1961 “moon speech.” Visionary goal thus proclaimed, the funding floodgates would open.

At MSFC, by contrast, many managers expected that NASA budgets would remain tight for the foreseeable future, so that any space technology development that took place would need to be incremental; that is, it would have to begin with existing space hardware and occur in small steps. MSFC's work on the Skylab Orbital Workshop, a temporary LEO space station launched in May 1973 on the last Saturn V rocket to fly, probably helped to shape their outlook.

The 169,950-pound Skylab "cluster," which comprised the Multiple Docking Adapter, the Apollo Telescope Mount (ATM), and the Orbital Workshop, had been conceived originally as an element of the Apollo Applications Program (AAP). As its name implies, AAP had been meant to apply hardware developed for the Apollo lunar program to new tasks. The Skylab Orbital Workshop was a converted Saturn S-IVB stage outfitted with experiment apparatus, crew quarters, and supplies for visiting three-man crews. Three crews were launched to Skylab in 1973-1974; the last orbited the Earth for 84 days.

The Skylab Orbital Workshop floats serenely over the Earth, but this image bears evidence of its nearly disastrous launch and the heroic efforts that saved it. Skylab's reflective meteoroid shield deployed during ascent and peeled away, tangling one of its wing-like solar arrays in debris and loosening the other. A stage separation rocket motor then blasted away the loose array and the tangled array refused to open. Skylab was starved for electricity while temperatures inside it soared, threatening to spoil food, film, and medicines. The first Skylab crew (Charles Conrad, Paul Weitz, and Joseph Kerwin) deployed a sun shield and forced open the jammed array. Skylab went on to host astronauts for a total of 171 days. Image credit: NASA

NASA built most of a second Skylab, but was unable to secure funding to complete it, launch it into orbit, and launch crews to it. The first Skylab was a success, so MSFC might have expected on that basis to have "earned" funding for the second. The Huntsville Center had, however, learned during the 1960s not to equate success with rewards. It had been responsible for the Saturn V moon rocket, the largest and most powerful launcher ever built. Even as MSFC succeeded in making the mighty Saturn V work, however, it began to suffer funding and staff cuts that by the time Skylab flew would make it a shadow of its former self.

When MSFC engineers looked at the Space Transportation System (STS), as NASA called the Space Shuttle and its stable of expendable upper stages and European-built Spacelab components, they saw not the promise of a big new space station, but rather a system which, once operational, could benefit from evolutionary development. In particular, they noted that Spacelab, which MSFC was assigned to integrate with the Shuttle, could not reach its potential as an orbiting laboratory while the Shuttle Orbiter's planned maximum time in space was only seven days. The Orbiter and its payloads would rely for electricity on the former's fuel cells, which meant that the quantity of fuel-cell reactants the Orbiter could carry would determine their endurance.

The Space Shuttle Orbiter with its Payload Bay doors open to space. A drum-shaped, European-built Spacelab module is shown as a cutaway.  Curved panels raised above the front half of the doors are radiators. The Spacelab module is located near the rear of the Payload Bay to ensure that the Orbiter's center of gravity is placed properly for maneuvers and landing. Image credit: NASA

In early 1977, with the first STS flight test officially planned for March 1979, MSFC proposed "the first step beyond the baseline STS" – a Power Module (PM) capable of supplying 25 kilowatts of electricity continuously. The solar-powered PM was meant to be deployed into LEO from a Shuttle Orbiter payload bay and left in space for up to five years. A succession of Orbiters bearing Spacelab modules and pallets in their payload bays would dock with the PM and use its electricity to remain in orbit for up to 30 days at a stretch.

Alternately, a Shuttle Orbiter could attach a "freeflyer" payload to the orbiting PM and leave it to operate on its own. This appealed to materials scientists, who worried that astronauts' movements on board the Shuttle Orbiter and Spacelab would rattle and ruin their microgravity experiments. Orbiters would periodically dock with the materials science freeflyer/PM combination to retrieve experiment products – for example, large flawless crystals – and replenish raw materials.

In addition to electricity, the PM "building block" would provide thermal and attitude control. The latter would permit a docked Orbiter to conserve its Reaction Control System propellants. Freeflyer payloads meant to be docked with the PM could be built without thermal and attitude control systems, reducing their cost.

Image credit: NASA

MSFC engineers planned at first to base the PM on the Skylab ATM design. They quickly found, however, that modifying the ATM to meet stringent Orbiter payload bay safety requirements would cost more than a new design. They retained the ATM's octagonal cross-section, however, because they found that it made efficient use of the Orbiter's cylindrical payload bay volume while providing flat surfaces upon which to mount subsystems.

Although it nixed the ATM-based design, MSFC still aimed to lower the PM's cost by using subsystems developed for Skylab, Spacelab, Shuttle, and other programs. These included three Skylab Control Moment Gyros for attitude control and four curved Shuttle Payload Bay door radiators for thermal control. MSFC planned to update and improve Skylab systems used in the PM based on Skylab flight experience. All major PM subsystems would be redesigned for easy replacement by spacewalking astronauts.

The 31,000-pound PM would measure 55 feet long from the framework holding its aft- and side-facing international docking ports to the forward ends of its stowed twin solar arrays. This would leave room in the Shuttle Orbiter's 15-by-60-foot Payload Bay only for a docking tunnel with an international docking port. The tunnel would be bolted to the forward wall of the bay over the hatch linking the bay to the Shuttle Crew Compartment.

This NASA artwork shows a Space Shuttle Orbiter bearing a Spacelab module in its Payload Bay docked with a separately launched Power Module which extends forward over the Orbiter Crew Compartment.

Upon arrival in LEO, the astronauts would open the Shuttle Orbiter's Payload Bay doors and release the five pins that secured the PM in the bay. They would then use the Orbiter's robot arm to lift the PM from the bay and berth its side-facing docking port on the Orbiter docking port. This would position the module so that it extended out over the Crew Compartment.

The astronauts would next extend the PM's twin solar arrays. Fully extended, each wing-like array would measure 131 feet long by 30 feet wide. They would together span a little more than 276 feet. MSFC sized the arrays to generate a total of 59 kilowatts of electricity; that is, 34 kilowatts more than the PM would supply to Spacelab-carrying Orbiters and freeflyers. A portion of this excess would power PM systems, but the majority would charge batteries in the PM so that it could supply a constant 25 kilowatts throughout its roughly 90-minute orbital day-night cycle.

Close-up of Power Module showing international docking ports and curved radiator panels. Image credit: Junior Miranda

MSFC acknowledged that the big solar arrays would degrade over time; its engineers estimated that over five years they would lose 5% of their generating capacity. Similarly, the PM's batteries would gradually lose their ability to charge and discharge. After five years, a Shuttle Orbiter might be sent up to recover the PM and return it to Earth for refurbishment. Another Orbiter would then launch it back to LEO to continue its duties.

MSFC engineers presented the PM concept to scientists at an MSFC-sponsored solar-terrestrial physics workshop in October 1977. They found broad support for the new capabilities the PM would give to the baseline STS.

Lots of living space: Skylab, Power Module, Spacelab-based add-on supply module, Shuttle Orbiter, and Payload Bay-mounted Spacelab module. Image credit: Junior Miranda

This view emphasizes the solar arrays on the Power Module and Skylab. The 276-foot span of the Power Module arrays dwarfs the Shuttle and Skylab. The Skylab "wing" array lost during launch in May 1973 is conspicuous by its absence; also notable are two Apollo Telescope Mount "windmill" solar arrays stowed to  make way for the Power Module and Orbiter. Image credit: Junior Miranda

They also proposed that the PM become part of NASA plans to reuse Skylab. MSFC contractor McDonnell Douglas had "interrogated" the abandoned Orbital Workshop's data handling system and found that, nearly four years after its last crew had returned to Earth, reactivation remained feasible. The first step toward Skylab reuse would be for a Space Shuttle to rendezvous with it late in 1979 and boost it to a longer-lived orbit.

The PM would be a late addition to the revitalized Skylab cluster; MSFC did not expect that the new STS element would reach LEO for the first time until 1983, by which time several Shuttle Orbiters would already have visited Skylab. Once added to Skylab, however, the PM would enable Skylab to support as many as six astronauts without a Shuttle Orbiter present. They would perform experiments with large-scale space construction and early space industrialization.

MSFC engineers hoped that the PM might also contribute toward NASA's quest for Skylab's successor. They envisioned that PMs attached to Shuttle Orbiters, freeflyers, and Skylab might lead to PMs attached to Spacelab-derived habitat and laboratory modules during the 1980s: in other words, a new NASA Space Station.

In 1978, the Huntsville center contracted with Lockheed Missiles and Space Company to study PM evolution. MSFC expected that PM development might lead to simultaneous operation of several small specialized "space platforms," each with at least one PM attached. The platforms would not need to be staffed continuously. MSFC argued that several small platforms would best serve scientific and engineering disciplines with conflicting needs, and might cost less than a single large station besides.

In early 1979, NASA Headquarters authorized MSFC to spend $90 million on PM hardware development. The Huntsville center created a PM Project Office in March 1979. At about the same time, however, the space agency abandoned plans to reuse Skylab because the Space Shuttle would not be ready in time to prevent its uncontrolled reentry. Skylab reentered Earth's atmosphere over Australia on 11 July 1979.

JSC, meanwhile, pitched a new-design Space Operations Center (SOC). The space station would include hangars for reusable auxiliary spacecraft and satellite repair, robot arms, habitat and laboratory modules, and truss-mounted solar arrays spanning more than 400 feet. It was conceived primarily as a "space shipyard," a role inspired partly by JSC's 1970s enthusiasm for Solar Power Satellites.

Artist concept of the module cluster of the Space Operations Center (SOC). Most modules are a little less than 60 feet long by 15 feet wide (the length and width of the Space Shuttle Payload Bay). At lower left is a "false Payload Bay" for satellite servicing and spacecraft assembly. Had the SOC been built, this would have included robot arms. A Service Module partly covered with gold thermal blankets is located at upper right and a hexagonal hangar is located below it. The artist has included a Spacelab-derived module near a Shuttle docking port at left. Image credit: NASA

STS-1, the maiden flight of Columbia, the first Space Shuttle Orbiter, took place in April 1981. James Beggs, President Ronald Reagan's choice for NASA Administrator, was confirmed two months later. Beggs soon sought presidential approval for a Space Station. This move seemed to favor JSC's revolutionary vision. At the same time, however, Beggs informed MSFC that he wanted to buy the new station "by the yard" – that is, as money became available. This approach seemed more in line with MSFC thinking.

In November 1981, NASA Headquarters halted PM, SOC, and other station-related work at MSFC and JSC. According to Dunar and Waring, it did this to take charge of station development and to end MSFC-JSC rivalry. Following Reagan's January 1984 State of the Union Address, in which he called upon NASA to build a Space Station by 1994, JSC's revolutionary vision seemed to win out. JSC was designated "lead center" for Space Station in early February 1984.

Although Reagan authorized NASA to spend only the $8 billion Beggs had told him the Space Station would cost and had specifically called for a space laboratory in his State of the Union Address, the agency's first baseline station design, the "Dual Keel," was an elaborate combination of lab, Earth/space observatory, and shipyard measuring more than 500 feet wide. Like the SOC, it included a small fleet of freeflyers and auxiliary vehicles. It also included a pair of solar-dynamic power systems - a NASA Lewis Research Center innovation - for generating large amounts of electricity.

The Dual-Keel Space Station design unveiled shortly after the January 1986 Challenger accident was dead on arrival, though NASA sought to ensure a future for the design until 1990. Image credit: NASA

The Dual Keel's complex multipurpose design immediately came in for criticism. Materials scientists, for example, complained that space construction, the comings and goings of auxiliary spacecraft, the whirling turbines of solar-dynamic power systems, the presence of a large crew, and atmospheric drag on such a large structure were bound to spoil the station's microgravity research environment. Congress, meanwhile, accused NASA of low-balling its cost estimate to gain the project's approval.

Congressional cost containment, combined with the 28 January 1986 Challenger accident, concern over the number of assembly and maintenance spacewalks the station would need, and a rapidly expanding U.S.-Russian space partnership (one which would have been unthinkable when Reagan delivered his January 1984 speech), led to a decade-long series of station redesigns. The Space Station shrank and lost many of its proposed capabilities. This untidy evolution yielded the International Space Station (ISS), a U.S.-Russian hybrid with Japanese and European labs and Canadian robotics.

Early days of the International Space Station: from upper left to lower right are visible a Progress freighter, the Service Module with docking node, the FGB, and U.S. Node 1. Image credit: NASA

Ironically, the first ISS element launched into space amounted to a Power Module. The Russian-built, Russian-launched, U.S.-funded FGB provided the second ISS element to reach space, U.S. Node 1, with electricity and attitude control from December 1998 to July 2000, when they were joined by a mini-space station – the Russian-built, Russian-launched Service Module, which had originally been intended as the "base block" of the Soviet Union's Mir-2 station. At that point, ISS became capable of supporting long-duration crews.

Sources

Guntersville Workshop on Solar-Terrestrial Studies, NASA Conference Publication 2037, "summary papers from a University of Alabama in Huntsville/NASA Workshop conducted 13-17 October 1977, at Lake Guntersville State Park Convention Center, Guntersville, Alabama," NASA George C. Marshall Space Flight Center, 1978

"The 25 kW Power Module – First step beyond the baseline STS," G, Mordan; paper presented at the American Institute of Aeronautics and Astronautics Conference on Large Space Platforms: Future Needs and Capabilities, held in Los Angeles, California, September 1978

25 kW Power Module Updated Baseline System, NASA TM-78212, NASA George C. Marshall Space Flight Center, Huntsville, Alabama, December 1978

Power to Explore: a History of Marshall Space Flight Center, 1960-1990, NASA-SP-4313, Andrew J. Dunar and Stephen P. Waring, NASA History Office, 1999

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