Analytical and experimental investigations have been made to deter¬mine the landing characteristics of a reentry spacecraft equipped with a vertical-cylinder air bag for impact load alleviation. Assuming a rigid body and isothermal air compression and expansion, computations were made to determine accelerations for a landing on concrete from a flight-path angle of 90° (vertical flight path) at a contact attitude of 0°. A scaling technique was developed which permits the application of normal scaling laws to data obtained from model tests conducted at prevailing atmospheric pressure. Two models (l/6 and l/2 scale) of the air-bag system were tested to establish the validity of the computational procedure and the scaling technique. A l/6-scale dynamic model of a spacecraft—air-bag configuration proposed for manned reentry was landed on concrete, on sand, and in calm water from various flight paths for a range of contact attitudes. Accelerations were measured along the X-axis (roll) and Z-axis (yaw) by accelerometers rigidly installed near the center of gravity of the model. Actual flight paths and attitudes were determined from high-speed motion pictures.nReasonable agreement between computed and experimental data (0° attitude, 90° flight-path angle) indicates that the scaling technique is satisfactory for prediction of full-scale characteristics from model tests with air bags in atmospheric environment. The maximum acceler¬ations obtained during landings on sand were about 11g along the X-axis and about 8g along the Z-axis. The maximum accelerations obtained during landings in water were about 10g along the X-axis and about 6g along the Z-axis. The rotational motions of the spacecraft during the time required to reach peak accelerations were small for the water and sand landings at all flight paths and attitudes of the investigation.
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