3 gravities acceleration. Horizontal takeoff and lifting flight during initial boost appears to be preferable for this mode of transportation. The third area of study is aimed at determining the next large launch vehicle after SATURN V which may be required to provide the very large weight-lifting capability for such missions as large space stations, large lunar base operations, and manned planetary exploration. This effort is designated post-SATURN.

SATURN improvement

The first area of vehicle studies, SATURN improvement, is expected to be fruitful. Because this Nation has been spending and is continuing to spend large amounts of money to develop the SATURN IB and SATURN V vehicles, it is desirable to prolong the operational lifetime of the vehicles by uprating their performance capability to accommodate missions beyond the APOLLO program. We now have underway programs of study which will tell us the most feasible way of performing these vehicle improvements. Figure 96 shows the present performance of the SATURN IB vehicle and its growth potential. Even higher payloads are possible with this vehicle, but the cost effectiveness and impact on launch facilities require considerable study before maximum growth can be proposed. The payload growth shown can be obtained by such changes as the addition of fluorine to the oxygen, the use of strap-on solid propellant motors, or the use of high-pressure engines. Other methods which will require moderate to severe change of the basic vehicle structure are being considered. Figure 97 shows the outline of a conventional lox-hydrogen (J-2) engine of 200,000 pounds thrust contrasted to a typical high-pressure

engine configuration of 265,000 pounds thrust. Within the limitations of a fixed vehicle diameter, the higher chamber pressure allows a higher nozzle area ratio to be used. This higher nozzle area is one of the factors which allows the high-pressure engine to develop a higher specific impulse.

The engine is smaller because the engine plumbing, pumps, and turbine work with higher density flows and consequently do not require as much flow areas as conventional engines. A substantial benefit accrues to the vehicle when high-pressure engines are used due to the higher oxidizer-fuel ratio that they operate on. This permits a reduction in the size of the hydrogen tank and a consequent reduction in the vehicle tankage weight.

Figure 98 indicates the growth potential of the SATURN V vehicle. Payloads in this category can be obtained by changes similar to those previously described for the SATURN IB. These and other methods will require careful study and consideration so that the most promising approach to uprating can be determined.

Reusable orbital vehicles

Figure 99 shows a reusable launch vehicle concept which would transport approximately 10 passengers plus 3 tons of associated cargo to Earth orbit. It would be designed for passenger accommodation and safety and allow for launch vehicle reusability. Due to the horizontal takeoff mode, accelerations felt by passengers would be limited to 21⁄2 to 3 gravities during ascent, and to 4 gravities under abort conditions. The vehicle consists of two stages, both of which are designed for lifting reentry, horizontal landing after return to the

launch site, and for complete reusability. It is about the same size as current commercial aircraft. We are investigating systems employing propulsion and other combinations of rocket and air-breathing boost propulsion. Also being investigated is the use of a ground based accelerator, during which the major portion of the undercarriage is left on the ground.

Post-SATURN

The third vehicle study area is that of post-SATURN. Because manned planetary exploration is the most ambitious of the planned missions, it will probably determine the size and requirements of the next large launch vehicle after SATURN V. It will be a major step in both technology and capability. Therefore, post-SATURN vehicles must boost the largest payloads, with the greatest reliability and at the lowest possible cost consistent with the projected state of the art.

The many possible configurations being examined are grouped into several classes. Class I vehicles are considered to employ present SATURN V state of the art. Class II vehicles are somewhat beyond the present state of the art in that they require developments such as new propulsion systems. Class III vehicles require major advancements in technology.

Figure 100 shows typical class II vehicles. Both expendable and reusable vehicles are being investigated, Earth orbit payloads being in the range of about 1 million pounds.

There are now 29 astronauts in training to perform manned missions in GEMINI and APOLLO. The latest group of 14 was selected this past fall and reported to the Manned Spacecraft Center in January 1964. Future selections of scientist-astronauts are being considered The National Academy of Science is assisting in these selections. (See S. Doc. No. 42, 88th Cong., 1st sess. U.S. Astronauts, Staff Report of the Senate Committee on Aeronautical and Space Sciences.)

The training of the astronauts involves three areas: their active participation in the design and development of spacecraft, training equipment, and life support systems; general training, including instruction in science and engineering subjects, aircraft flight, physical conditioning, survival training, and indoctrination under simulated space environmental conditions; and special training in simulators and trainers to meet GEMINI and APOLLO operational requirements (figs. 101 and 102).

The astronauts are actively participating in the design and development of spacecraft, full-mission simulators and life support systems. Mockups of these major components underwent major review periodically by the astronauts this past year as part of the design development. In addition to contributing to hardware development, this activity contributes significantly to crew readiness (fig. 103).