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Aviation History
1963
1963 - 1866.PDF
FLIGHT International, 17 October 1963 673 Earth satellite missions with our missions to the Moon, Mars, and Venus. I have chosen Pioneer 5, Ranger and Mariner to illustrate our past spacecraft experience with interplanetary, lunar and planetary flight, respectively. Pioneer 5 was a spin-stabilized, solar-powered spacecraft bred from Earth satellite technology. It was designed to make particle and field measurements in interplanetary space. The success of this relatively simple spacecraft in returning valuable data from up to 22.5 million miles convinced us that interplanetary monitors of this type should become a basic part of our pro gramme. We will begin a new Pioneer series in 1965 in support of the International Quiet Sun Year (IQSY). The Ranger is really a second- or third-generation spacecraft. It was designed to fly to the Moon and land an instrumented cap sule at less than 250ft/sec within a 50-mile circle. Because of the unique requirements of this mission, Ranger incorporated a number of technical innovations. Three-axis stabilization was achieved with an Earth sensor, which pointed the directional antenna and locked the spacecraft in roll, and with a Sun sensor which pointed the roll axis and solar panels at the Sun and locked the spacecraft in pitch and yaw. The spacecraft could be programmed to any attitude for a mid- course velocity correction capable of reducing the dispersion dia meter at the Moon from several thousand miles to about 50 miles. After the midcourse manoeuvre was complete, the Ranger could re acquire its Earth-Sun lock until arrival at the Moon. Upon arrival, the Ranger could be programmed to the proper attitude to align its capsule retro-rocket axis with the vertical des cent velocity vector. The retro-rocket would be triggered by a radar altimeter and would slow down the instrument capsule to a probable resultant impact velocity of less then 250ft/sec. The extremely sensitive seismometer capsule could withstand this impact by virtue of a ruggedized design and a protective layer of balsa wood. On the most successful of the three flights made with this spacecraft, it performed all automatic functions properly prior to arrival at the Moon and executed the first midcourse correction made by a space craft. One of the Rangers hit the Moon but none returned lunar data. Our plans include additional Rangers of this type. The Mariner 2 was by far our most successful deep space probe. Its attitude control and midcourse manoeuvre subsystems were functionally similar to th»se of the Ranger just described. On its 109-day and 180 million-mile flight to Venus, Mariner 2 performed beautifully despite minor problems including excessive tempera- Table I: Scientific Satellites (unsuccessful craft in italics) 1958 Explorer 2, Vanguard, Vanguard, Explorer S, Vanguard, Explorer I, Vanguard I. Explorer 3. Explorer 4. 1999 Vonguord. Explorer, Vanguard, Vanguard 2 (partial success). Explorer 6. Explorer 7, Vanguard 3. 1960 Explorer, Explorer, Explorer 8. 1961 Explorer. Explorer, Explorer, Explorer 13, Explorer 9, Explorer 10. Explorer 11. Explorer 12. 1962 OSO, Ariel. Alouette, Explorer 14, Explorer 15, Explorer 16. 1963 Explorer 17. Table 2: Application! Satellites (unsuccessful craft in italics) 1960 Echo, Tiros I, Echo I, Tiros 2. 1961 Tiros 3. 1962 Tiros 4, Tiros 5, Telstar I, Tiros 6, Relay I. 1963 Syncom I, Telstar 2, Tiros 7, Syncom 2. Table 3: Deep Space Probes (unsuccessful craft in italics) 1958 Pioneer 2, Pioneer I and Pioneer 3 (partial successes). 1959 Pioneer, Pioneer 4 (partial success). 1960 Pioneer, Pioneer, Pioneer 5. 1961 Ranger I, Ranger 2. 1962 Mariner t, Ranger 3, Ranger 4, Ranger 5, Mariner 2. tures, a solar-panel short, and a weak Earth sensor signal. Less than 41b of nitrogen were consumed for attitude control. Mariner's midcourse manoeuvre corrected the Venus miss distance from about 233,000 miles to 21,600 miles. We aimed for a miss of 10,000 miles but designed Mariner to scan Venus effectively at up to 40,000 miles distance. At the planet, all experiments worked well and returned in valuable radiometric observations of the planet's atmosphere and surface. The telemetry signal strength at Earth was less than 10-18 watts but was well within the design signal-to-noise ratio. The technology developed by Ranger and Mariner will continue to be used in the NASA lunar and planetary spacecraft. There is no good substitute for extensive ground testing in the development of spacecraft. The test history of an average Explorer- type spacecraft shows that, in the five test phases of checkout, vibration, temperature, vacuum, and thermal vacuum, this average spacecraft experienced 18.2 electrical failures and 4.6 mechanical failures. Most electrical failures occurred during thermal vacuum and most mechnical failures during vibration. The long-term effectiveness of such thorough testing standards is evident. The average time to the first malfunction of any sort in flight of all of NASA's unmanned spacecraft had climbed to about two months in 1962. The average useful life has exceeded six months and is still rising because some of last year's spacecraft are still functioning at a useful level. [Continued overleaf Among the future spacecraft mentioned by Mr Cortright were (left) the Advanced Orbiting Solar Observatory, which will weigh 9001b (including 2501b of instruments) and will make its first flight in 1967; and (right) the forthcoming second-generation Pioneer series of interplanetary spacecraft. These latter craft will weigh 1151b, of which 201b will consist of instruments STABILIZATION BOOM ANTENNA-* / /VIEWING 1 / PORT -SOLAR CELLS MAGNETOMETER ACTIVE THERMAL CONTROL
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