A Smaller Payload Bay?

One challenge in designing a smaller orbiter using an expendable propel­lant tank or tanks was maintaining the 15 x 60 foot payload bay required to launch the largest national security payloads. As NASA began to explore what it called the “drop tank” design, Dale Myers on May 25 wrote Grant Hansen, asking him to “determine if Air Force requirements [which included National Reconnaissance Office payloads] could be accommodated” in a 12 x 40 foot payload bay. He added that “if this is not possible, I would appreciate some thoughts as to what missions must exceed these dimensions and what alternate launch capabilities could be used.”42

Hansen’s reply was negative in tone, saying that a shuttle with the smaller payload bay would “preclude our full use of the potential capability and operational flexibility offered by the shuttle” and would “degrade the pay­load cost savings” that were an important part of the national security inter­est in the shuttle. Maintaining the Air Force Titan III expendable boosters to launch the largest national security payloads would mean that “the potential economic attractiveness and the utility of the shuttle to the DOD” would be “severely diminished.” Hansen estimated with the shorter payload bay “71 of the 149 payloads forecasted for the 1981 to 1990 time period in option C and 129 of the 232 payloads forecasted in Option B of the mission model will require launch vehicles of the Titan III family.” Hansen also noted the negative consequences of a narrower payload bay, especially in terms of the use of a large “transfer stage” to carry national security payloads to geosyn­chronous orbit.43 This response reflected the continuing national security community pressure on NASA to maintain a shuttle design with a large payload bay, even as NASA was seeking an approach to minimize shuttle development costs.