However, partly owing to the planned evolution of expendable launch systems by the Air Force, the U.S. government currently has available three families of expendable rockets: the soon-to-be-retired Titan IV and the about-to-be-flown Delta IV Heavy for heavy lift, and the old and new families of Delta and Atlas vehicles for medium lift. In addition, two small launchers (Taurus and Pegasus) provide on-orbit delivery of lighter spacecraft. These systems are completely expendable, will support only low launch rates, and are not crew-rated. The medium- and heavy-lift launchers also operate exclusively from two highly vulnerable Florida and California coastal locations, and one of the boosters (the Atlas V) incorporates a Russian-designed and -manufactured liquid main engine.
Our nation has relied for more than 20 years on the only crew-rated reusable launch vehicle (RLV) in the world, the Space Transportation System (the shuttles). Now, two catastrophic failures in 113 flights have reduced the shuttle fleet to three, which are grounded until corrective actions can be implemented, and have severely limited the shuttle manifest. Currently, crew access to the International Space Station (ISS) depends on the Russian space program to provide limited capability with expendable launch vehicles and crew modules. If the ISS is to be completed and to have the full crew complement, the space shuttle will have to be brought back into service or there will have to be an extended delay until a replacement vehicle is available.
This chapter contains at various points 34 findings and 26 recommendations.
Both the Air Force and NASA are beginning to pursue new capabilities to satisfy their respective mission needs. While potential new systems may differ considerably and are not yet fully defined, many of the underlying technologies are expected to be similar. As stated earlier, raw lift performance is not the issue. The issues are cost, reusability, reliability/availability, responsiveness, and turnaround time to put assets into space. NAI has targeted these issues in its access-to-space (ATS) pillar with a three-phase program of increasingly demanding requirements. Vehicle and supporting system characteristics and, by implication, NAI technology timelines are illustrated in Figure 3-1.
The ATS pillar has identified the common technical efforts and provides a mechanism for cooperation, sharing, and advocacy of these technologies. Included are reusable rocket propulsion, tanks, and airframes; thermal protection systems (TPS); integrated vehicle health management (IVHM); quick turnaround operations; hypersonic air-breathing propulsion; and many others. NASA and Air Force planning are discussed next.
Future NASA missions are planned to include human spaceflight and logistical support for the ISS, Earth and space science, astrophysics, and exploration of the solar system. In addition, NASA may seek to develop a new launch capability for very heavy lift to facilitate both crewed and uncrewed exploration of the solar system. Until recently NASA had been funding the development of an orbital space plane (OSP), which was to become operational before the end of this decade. Initial capabilities were intended to satisfy ISS crew rescue requirements. Crew transfer capability (Earth to LEO) was planned as a follow-on spiral development. The OSP was to be launched on an existing expendable vehicle modified to become crew-rated. It should be noted that since the OSP was a current vehicle development program and not a technology development program, it was not considered part of NAI. It is only mentioned here for the sake of completeness regarding future planned capability and for its potential to compete for limited NASA resources. However, the vision articulated by President George W. Bush on January 14,