THE “DUAL KEEL” SPACE STATION [1986-87]
Notes:
NASA struggled to define a “Dual Keel” design that met all the various cost,engineering,safety,launch and user requirements. By the time Phase B1 ended in March 1986, the size of the truss structure elements had been increased from 3 x 3 meters to 5 x 5 meters for additional strength and stiffness. Shown here is Martin Marietta's concept.
Another early 1986 modification involved the power system. At the end of Phase B1 in March 1986, NASA had settled for a hybrid system consisting of 25KW photovoltaic arrays and 50KW solar thermodynamic generators.
The number of American crew modules was also reduced from four to two while European and Japanese laboratories were incorporated in the design for the first time. The habitable volume remained the same, though, since the length of the US modules was increased to 13.3 meters.
NASA Space Station Office submitted its recommended final baseline in May 1986 as Phase C/D started. The Station would now support man-tended operations after the sixth Shuttle assembly mission and be ready for permanent occupation after the ninth mission. Initial Operating Capability (IOC) would be achieved after 20 flights -- twice as many as the 1984 estimate. The total number of required Shuttle flights would be 31. The number of instrument mounting ports was reduced to five, down from an earlier projection of nine. One of the two bays for satellite servicing was also deleted.
Rockwell “Dual Keel” Space Station proposal. NASA's new Space Station design was criticized in a widely publicized astronaut office briefing by Shuttle astronaut Gordon Fullerton. The Dual Keel design was found to provide poor access for maintenance, visibility from habitable areas was obstructed, there was no provision for internal vehicle 'hands on' access to EVA equipment. No crew escape vehicle had been added although a small fleet plus lower-than-hoped-for flight rates means astronauts could not be rescued as easily by the Shuttle. The Canadian manipulator was regarded as insufficient for building and maintaining such a complex Station. Fullerton also criticized excessive EVA "spacewalk" requirements, including a "long and complex" assembly sequence. By this time, increased complexity and Shuttle payload capability reductions had increased the required number of assembly flights to more than 20 for an Initial Operating Capability (IOC) vs. 8-10 in 1984. "Basic structure, wire runs, and plumbing are not easily designed for replacement / repair. EVA crew time even for planned maintenance is excessive. Correction of design errors may not be possible; unplanned failures may not be fixable at all."
