Alternative Space Transportation Approaches

As he thought through the path that NASA should follow, Low in August had outlined for his senior colleagues his ideas on “the desired Space Transportation System for the 1980’s.” He rejected both developing a full­sized, two-stage reusable shuttle and pursuing an approach using a reusable “ballistic” spacecraft, a capsule without wings, launched on an expendable booster and parachuted back to Earth. This approach was based on modify­ing the two-person Gemini spacecraft used in the mid-1960s to carry six or more people, and was becoming known as “Big-G.” Low focused on a “mini-shuttle approach wherein a smaller shuttle vehicle is first developed and launched on an expendable booster. The recoverable booster and the desired full-scale shuttle are phased in at a later date.” The mini-shuttle would have a 15 x 40 foot payload bay (so that it could carry research and application modules and eventually space station modules), upgraded Saturn J-2 engines, and a disposable hydrogen/oxygen propellant tank. It could carry 40,000 pounds (rather than 65,000 pounds) to a due-East orbit. The initial version of this mini-shuttle would make use of existing technology in its on-board electronic systems. It would be propelled to staging velocity by an expendable booster, then fire its engines to accelerate to orbital velocity. In successive stages of development, an advanced shuttle rocket engine could replace the J-2 engines and a recoverable booster, not necessarily piloted, could be used.

Low also considered a “glider approach.” This vehicle, Low suggested, would be winged but smaller, with a 12 x 40 foot payload bay, carrying 30,000 pounds to orbit. It would have small engines for maneuvering in orbit and to initiate return to Earth, but no large rocket engines. It would be propelled to orbit by an expendable booster. Low did not have “enough information in hand to lead to a firm recommendation between the glider approach and the mini-shuttle approach.” He suggested that NASA “take a further look at both the glider and the mini-shuttle before we decide to limit our work to one or the other.” Low noted that Dale Myers preferred the mini-shuttle approach, suggesting that a glider would only send astronauts “whirling about the Earth” to no evident purpose, while he, Fletcher, and von Braun favored the glider.21