The missions defined to date range from small 250 pound Explorer and space physics satellites to a 20,000 pound astronomy mission requiring annual revisits by the shuttle for servicing, maintenance and updating of instrumentation. Here, for instance, MH 70-7515, is an artist's concept of an advanced Nimbus type of weather satellite whose many cameras and other systems could be periodically serviced. An Agena and Earth Resources satellite are shown in this slide, MH 70-7010. This mission, presently under study, would use the shuttle as a delivery system to low earth orbit for both the satellite and Agena. The Agena would then propel the satellite to synchronous orbit. For missions of this type, the crew operating the shuttle will checkout the satellite in low earth orbit before committing it to its destination.

Space Shuttle sortie flights are missions conducted solely by the shuttle, and involve specific scientific investigations in areas such as astronomy, bioscience, plant and animal experiments, which can be accomplished within the seven-day on-orbit capability of the shuttle, MH 70-6290. Rescue missions could also be performed as a sortie flight. Requirements for sortie missions are expected to be significant once the full capability of the shuttle is understood by the potential users. For example, the capability of an individual experimenter to conduct his own experiment in orbit and return with the data, as well as his own personal observations, should be very attractive.

Space Station support is another important use for the shuttle. At the present time we are investigating the implications of using the shuttle to carry modules into orbit for assembly and operation of a multi-purpose space station. Under this concept, the shuttle could also be used for replacing modules as they become obsolete or require major overhaul and for substituting more sophisticated modules as they become available. Regardless of the final configuration of any future space station, however, the shuttle will be used for logistics support, transferring crews to and from the station, replacing consumables and bringing experiment data, films, etc. back to earth. Apart from NASA, the shuttle represents a national capability that can satisfy the booster requirements of the Department of Defense for the foreseeable future and will add flexibility and operational options not available with existing expendable boosters. It will allow DOD to replace all of their current launch vehicles with the shuttle.

Other government agencies, working through an interagency committee, have estimated their preliminary requirements. Uses include communication and navigation satellites, improved Tiros weather satellites, precision position determination satellites and earth resources satellites. Again, it is anticipated that several satellites can be carried to earth orbit by a single shuttle flight, thereby further reducing the operational cost to these user organizations.

Benefits

The shuttle system will benefit the users in two major areas. The first is the direct benefit of the reduction in the cost of transportation of payloads to orbit. The second and equally significant is the benefit of reduced costs of the payloads themselves made possible by the characteristics of the shuttle system. These advantages include:

High payload weight and volume capacity.

Mild launch environment.

Base of repeated transport to space.

Payload return from space.

Intact abort capability.

Shuttle payload capacity and capability are comparable to large expendable launch vehicles, yet the shuttle per mission cost is characteristic of the smaller launch vehicles in our present inventory.

Present day space satellites involve complex engineering since the high cost of payload to orbit using today's launch vehicles places a premium on miniaturization and minimum weight. In addition to mission requirements, the satellite subsystems are carefully designed to meet the specific demands imposed on the payloads by the launch vehicle. These severe constraints can be relaxed in shuttle launches because among other assets, the large payload volume of the shuttle bay, the ample weight to orbit capability, and a 3G maximum acceleration. This will allow the configuration of the satellite to be established by the mission objectives and by considerations of component access, easy fabrication, and simple testing rather than by the need to crowd the equipment into the nosecone of an expendable launch system. My next chart, MH 70-7062 shows a satellite built with a light weight tubular space frame. Subsystem components

are grouped on two terminal boards, which are fabricated as separate subassemblies. Many of these subsystem components are grouped on two terminal boards, which are fabricated as separate subassemblies. Many of these subsystem components will be standard off-the-shelf devices with dramatic cost reductions being achieved at the expense of the allowable weight increase. Standardized subsystems will in many cases have performance in excess of the specific requirements of the satellite, but the benefits of multiple production will make this possible at reduced cost. The large diameter antennas shown in the figure are simple dishes. In current space vehicles, these would need to be folded to fit within the confines of the launch vehicle shroud. The cost advantages of these approaches are readily apparent.

In today's mode of space operations any significant malfunction of either launch vehicle or payload generally results in loss of all or at least part of the mission objectives. With the shuttle, a malfunctioning payload can be returned to earth, fixed, and then recycled through checkout and launch.

In addition, the shuttle permits payloads to be returned to earth for overhaul and updating of systems. Since the shuttle will bring satellites back to earth as easily as it puts them in orbit, we will be able to reduce costs through reuse of space equipment. Even if a payload is not a candidate for reuse, many of its subsystems can be adapted for use on other satellites..

Finally, the shuttle, like a commercial transport, is designed to survive malfunctions of its own systems and return safely to earth. This concept, which is called "intact abort," provides safe return of its passengers. Contrasts with the present day situation in space flight, in which a major malfunction of the launch vehicle usually results in the loss of the satellite. Present day space programs often plan against possible mission failure by building backup flight units. Fewer backup systems would be needed with the shuttle and the assurance obtained by orbital checkout will further reduce mission failure risk.

Summary

TECHNICAL STATUS

Extensive studies have been conducted by the National Aeronautics and Space Administration, the Department of Defense, and industry to identify all technology requirements. Follow-on studies are now concentrating on the pacing items of shuttle design that must be accomplished before we move into final design. A summary evaluation of these key technical areas is shown here, MH 70-7325.

Our most critical studies are being directed to the design and development of an airframe structure in conjunction with thermal protection systems and materials which must be lightweight and reusable. Further they must protect the shuttle from the extreme high temperatures of reentry predicted as a result of previous space flights and wind tunnel testing. A number of very promising candidate materials are available and work has been focused on the applications of these materials to the shuttle. Technical requirements for integrated avionics and control systems are in hand, but the applications of this electronics technology to shuttle systems control will require innovation and proof-of-concept demonstration.

Program Plan

Existing information and continued progress in basic technical areas have provided the keystone for the current definition studies and future design of the shuttle. High pressure hydrogen-oxygen propulsion experience will make possible the compact and lightweight engines with high thrust and high efficiency required. Spacecraft technology advances during the past decade, provides us with the assurance that the necessary aircraft flight characteristics can be proIvided in the shuttle. Previous knowledge in electronics, guidance and control, structures, and heat shields has been extended and applied to shuttle definition and design requirements. A continuation of these technical applications through FY 1972 is outlined here MH 70-7326.

Vehicle definition will be advanced by wind tunnel testing to define the precise aerodynamic heating, launch aerodynamics, staging separation forces, reentry stability and control characteristics, and atmospheric propulsion effects. Dynamics testing will proceed to determine wind loads, vehicle flutter effects and the acoustic environment which will exist. Integration of vehicle and subsystem design and development requirements will be performed during FY 1972 to effectively define and focus prototype design and development requirements. Main engine efforts will include development testing of the thrust chamber and engine controls, and design of a prototype engine. Propulsion subsystem test facilities will be modified and development hardware tested. Fabrication of a prototype engine will be initiated.