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III: Steps Forward

Marshall Space Flight Center had since the Manned Orbital Systems Concept Study in 1975 been evaluating proposals for space stations based off Spacelab hardware, but as a lesser focus in terms of a focus on space stations involving Spacelab hardware was on ways to improve Spacelab's operations and flight capability. This had posed more of an interesting question (versus that of the development for a space station on Spacelab hardware), and one that had emerged as a point of competition and contrast between that of Johnson Space Flight Center and that of Marshall Space Flight Center. Both flight centers had begun the same kind of studies on ways towards improving the initial Shuttle flights with Spacelab in hopes of expanding unto a space station. For Marshall, their work would establish the development of a way into improving Spacelab as that of an entirely separate module. Known as the ‘Power Module’, it was proposed to be able to offer a steady twenty-five kilowatts of power to a Spacelab flight, which would allow to both provide more power to Spacelab and associated payloads than the Shuttle could provide via its fuel cells and allow an increase in duration of flight to as long as a month by reducing the amount of power being drawn by the fuel cells. In addition to the expected performance increase to the Spacelab flights, by having it as an entirely separate ‘module’ (rather than as a ‘solar array kit’ as proposed by Johnson) it could offer the capability to function as a ‘free-flyer’ and be able to host a series of experiments that would not be required to be man-tended and needed to remain in space for months at a time.

While the Power Module was intent on increasing the power and extending the duration of Spacelab flights, the capacity for it to act as a free-flyer had paved the way for a major variety of missions or payloads that it could undertake. Yet the biggest unsaid reason for the development of a Power Module by Marshall was simple; the development of a space station for NASA. The Power Module had emphasized Marshall's approach of 'building it as you go' and would represent but the first step for the development of a space station by both free-flying payloads along with the extension of Spacelab flights. The next steps after that would be either the upgrading of the Power Module to allow additional power production (and eventual addition of fixed modules into a space station) or for additional fixed experiments and other associated hardware that could be used in the power being provided by it. Even if the latter option was chosen, the Power Module could be upgraded on orbit and still allow the former option to be taken and developed. Yet for the time being, Marshall found the focus of its own future centered around the Power Module and one that would have to be lobbied for and pushed against whatever Johnson would try to push forth.

While the effort of design and politics were underway between Johnson and Marshall over the future for NASA after the Shuttle was operational, progress on the Space Shuttle was continuing at the National Space Technology Laboratory (NSTL) [1]. The National Space Technology Laboratory had been assigned the role for testing the Space Shuttle Main Engine and to ensure it was ready for flight. The initial piece for testing had been the ‘Integrated Subsystem Test Bed (ISTB) which was intended as that of a prototype Space Shuttle Main Engine (SSME) capable of operating up to 50% thrust [2] and for the development of a proper start-up procedure for the Shuttle (this would not be completed until the end of 1978). Throughout 1976, the ISTB would be utilized towards tests of up to 50% thrust (including few of 65% thrust), and as the tests proceeded there was the eventual goal of getting 100% thrust from a development engine (separate from that of the ISTB). Finally in March 1977, a development engine would achieve a total of 100% thrust in a test. While it was necessary to work towards actually maintaining the 100% thrust for an actual flight duration, there was going to be the need to reach the total of 109% thrust, the then rated ‘emergency’ thrust level [3].

Testing of the SSME, as with all new engines, was bound to run into problems and some of the first major issues would come about during a test of 75% power during March. A fire would break out after a fall in the shaft speed in the oxygen turbopump, and investigations would show that the point of origin of the fire had started from a failure from a major liquid-oxygen seal. While the seal was redesigned and put into use, it was but the start of the headaches at the NSTL for the issues with the oxygen turbopumps. In September, another test of a SSME (running at near full power) would see a failure, with the engine having 'shaken' itself apart. The investigation of it would show that the failure of the engine had occurred on both sides of the bearings of the oxygen turbopump shaft. Once more, fixes and redesigns on the SSME were underway in order to prevent such a failure from happening on an actual flight.

As the work and issues with the SSMEs were being handled throughout 1977, parallel work involving the SSMEs was happening at the NSTL with the efforts at readying and preparing the Main Propulsion Test Article (MPTA) for use. The Main Propulsion Test Article was a structural article made up of the Shuttle aft fuselage (where the SSMEs would be mounted), a truss structure making up the basic structure of the mid-fuselage of the Orbiter, and all the associated plumbing to run the SSMEs. Having arrived at the NSTL in June 1977, work on verifying it and combining it with the MPTA's counterpart of the External Tank found itself underway, and by April 1978 it was officially ready for testing of the SSMEs. From May to July, testing of the MPTA found itself underway racking up crucial time for the testing of the engines, and showing no problems. Moving into late August, the testing of the SSME hit its stride, running through more than 5,000 seconds of trouble-free operation, with more than 90% of it spent at or above 100% power. For the program as a whole as 1978 drew to a close, everything seemed to be going fine for the first flight which was targeted for September 1979.


[1] The National Space Technology Laboratory as named in 1974 was originally known as the Mississippi Test Facility and known from 1988 on, as the John C. Stennis Space Center.

[2] The minimum thrust for the SSME would originally be set at 50%, but would later be increased to 65%.

[3] The 109% 'emergency' thrust would be renamed to that of 'full power' as part of planning by NASA to have it available for every flight in order to increase the amount of payload that could be delivered to orbit.