Since the Shuttle is an "airplane" while it is in the atmosphere, it requires the same kind of wind tunnel test support required by any airplane project. Indeed, this "airplane" must traverse a speed range greater than that of any previous airplane from low take-off and landing speeds to hypersonic speeds near Mach-20 during orbiter reentry into the atmosphere. Consequently, the Shuttle wind tunnel test program requires testing in many of our largest and "most realistic" facilities. Since mid year 1972 when Shuttle Phase C development was initiated to the present time, we have performed approximately 15,000 hours of Shuttle testing in wind tunnels at our Ames and Langley Research Centers as shown in Figure 2. In FY 1975, we expect to conduct an additional 7,000 hours of tests in these facilities.

In the materials research area, our support of the Space Shuttle has contributed to substantial improvements in both high and low temperature reusable insulations, coatings, bearings, seals, and hydraulic fluids. During FY 1975, our primary support in this area will be to establish a data base on the characteristics of the baseline reusable surface insulation materials and to evaluate and assess in arc jet tunnels the effects of gaps, joints, and defects on the performance of the thermal protection system. Much of this work will be performed in the new Shuttle Interactive Heating Facility at the Ames Research Center. We expect to conduct about 3500 hours of testing in this facility in FY 1975.

Our major structures activity in support of the Shuttle in FY 1975 will be to provide critical data on the structural capability of the thermal protection systems. Panels of reusable surface insulation (RSI) tiles supported by a representative backup structure will be subjected to the critical temperature, pressure, and aerodynamic flow conditions associated with the Shuttle entry environment; and the ability of the thermal protection system to withstand the required 100 entry cycles will be assessed. A photograph of this type of test being conducted in the High Temperature Structures Tunnel at Langley is shown in Figure 3; the high heating in the gaps and joints between the tiles is evident.

Most of our Shuttle support effort in the area of dynamics and aeroelasticity has been completed, but some work still remains to be done. Vibration tests are underway on a % scale model (Figure 4) of a Shuttle type configuration. The NASA Structural Analysis (NASTRAN) computerized mathematical model of this vehicle has been developed and will be modified on the basis of these scale model tests. The modified computerized model will then be used to describe accurately the dynamic properties of the vehicle and to identify areas that are sensitive to small structural changes.

Advanced Space Transportation Systems Technology

Space missions requiring higher orbits and the operational cost savings of payload retrieval and refurbishment identify the next important step in the development of a cost effective space transportation system-a low cost, reusable Space Tug. Reusability, however, places large demands on the tug design; as a minimum requirement, the tug must return to the Shuttle in order to be returned to earth for refurbishment and reuse. This requirement essentially doubles the velocity requirements of the vehicle and amplifies the need for a high performance propulsion system.

Three major propulsion subsystems require technology advances: a) the main engine thrust chamber, b) systems for cryogenic fuel storage, and c) the propellant feed system. The design goals for this propulsion system and stage are at least 20 renses with minimal refurbishment, specific impulses of 470 seconds, and a mass fraction of .91 In FY 1975, technology work will continue toward the goals of demonstrating a longer life reusable thrust chamber, developing cryogenic seals, and developing longer life bearings for highly efficient, high-pressure turbopump systems illustrated in Figure 5. Fully reusable lightweight insulation and composite propellant feedlines will be demonstrated by FY 1976.

The weight of the tug is very important since the tug and the payload must be transported by the Shuttle. Decreases in tug weight directly result in increases in payload capability. We believe that advances in composite materials technology will play an extremely important role for the tug or any other future transportation system because the composites have the potential to significantly decrease vehicle weight. Indeed, composite materials promise a weight savings for a full capability space tug of approximately 25 percent. In FY 1975, emphasis will be placed on improving the mechanical properties of graphite reinforced aluminum composites by improving the bond between graphite and aluminum and investigating long term degradation phenomena. Additional advanced technology is required to develop very thin gage composite structures that will permit vehicle designs that accommodate concentrated launch loads and stresses and provide lightweight longlife structures.

Our efforts on advanced space transportation systems technology are timed so that the technology will be available to support decisions on the Space Tug in the late 1970's. Of course, the results of this work will have applications to many other uses and will be available to other users.

SPACE PAYLOAD SYSTEMS TECHNOLOGY

The real benefits from space exploitation will come from the payloads which are transported to space by the Shuttle system. Exploitation involves both those research and technology investigations that benefit from being performed in the space environment and those investigations on the earth and its resources performed from space. Our efforts in this area include technology developed in support of the Office of Applications which conducts investigations from space and an OAST new start-the Space Technology Shuttle Payloads Program—which will allow OAST research and technology to be performed in space. Space Applications

We are supporting a number of technology advancement activities which will enable the Office of Applications to carry out earth observations and pollution monitoring missions currently constrained by technology limitations. This work includes the development of technology for: a Light Detection and Ranging (LIDAR) device for detection and mapping of oceanic properties and atmospheric constituents; a Lasar Earth Beacon for improving the accuracy of our satellite tracking systems; and Advanced Auxiliary Propulsion system which will perform station keeping, maneuvering, and attitude control functions for spacecraft; and a new start-the Solid State Data Storage System which will significantly improve the reliability and decrease the costs of spacecraft data recording. The LIDAR work and the solid state data storage activities will be described in more detail.

LIDAR, which is similar to radar except that it uses a pulsed tunable laser beam for the excitation source, offers a method for the detection of various oceanographic properties such as oil pollution, phytoplankton, depth, and salinity and for the identification of the various constituents in the atmosphere. Application of this technology has been under development at the Langley Research Center since FY 1971.

As shown in Figure 6, demonstration of this technique in determining oceanographic properties has been accomplished from aircraft. Coastline depths can be determined from the time difference between the return beams of a high power laser from the surface and the bottom of shallow waters (up to 10 meters), and soluble salts, oil slicks, and phytoplankton can be identified from the wavelength, of the return beam. With an aircraft or balloon this technique can be used to provide ground validation of information gathered by earth resources satellites. Extension of LIDAR to infrared measurements of atmospheric constituents and pollutants will be emphasized in the next fiscal year. Exploitation of the method for airborne and ultimately spaceborne survey platforms for atmospheric mapping is planned.

The objective of the Solid State Data Storage Program is to provide by mid FY 1978 a modular, high density, very reliable 108 bit solid state data storage system using magnetic bubble domain technology and to demonstrate the system in tape recorder applications. Today, magnetic tape recorders are used to perform the on-board data storage function. These recorders suffer from low reliability due primarily to their moving mechanical parts (over 70 percent of past tape recorder failures were due to malfunction of these moving parts).