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Aviation History
1963
1963 - 1867.PDF
674 FLIGHT International, 17 October 1963 Missiles and Spaceflight During the same time period, our space launch vehicles had achieved a demonstrated reliability of 82 per cent, paced by the Delta, which has now had 19 out of 20 successful launches. A real challenge faces us in maintaining these upward reliability and life trends in the face of increasing complexity. This can be illustrated by listing the approximate number of piece parts for three of our advanced spacecraft: Mariner 2, Surveyor, and the Orbiting Geophysical Observatory. These spacecraft contain about 54,000, 82,000, and 100,000 parts respectively, and a sizeable per centage of these are critical for effective mission performance. Only time will tell whether we have moved too fast to this degree of sophistication. Turning to spacecraft now under development, the Orbiting Geophysical Observatory (OGO) is a 1,0001b satellite designed to carry 20-50 experiments in either circular polar orbits under 1,000 miles, when launched with a Thor Agena, or in highly eccentric inclined orbits with apogees of around 70,000 miles when launched with the Atlas Agena. The spacecraft is designed to hold its atti tude with the bottom looking directly towards the Earth, its solar panels towards the Sun, and selected experiments towards Earth, space, Sun, or in the direction of motion. A prime feature of the OGO is its data-handling system which can store up to 43.2 million bits of data at an input rate of 1,000 to 4,000 bits per second and a readout rate of 64,000-128,000 bits per second. Certainly, one of our most ambitious and significant scientific satellites is the 3,6001b Orbiting Astronomical Observatory (OAO), to be placed in a 500-mile circular inclined orbit in 1965. Basically the spacecraft is designed to sense and point the optical axis to any point in the celestial sphere, with the exception of a 90-degree cone about the Sun line, to an accuracy of one minute of arc. Using the experimenters' prime optics and a suitable error sensor, the space craft control system is designed to achieve a fine pointing accuracy of 0.1 second of arc for extended periods of time. This has turned out to be a formidable task with which we are still having some problems. A combination of gas jets and inertia wheels are the prime movers. A new observatory called the Advanced Orbiting Solar Obser vatory (AOSO) has recently been initiated. This is designed for extensive and detailed observations of the Sun not possible with the first-generation OSO. The field of view will extend to about 10" centred on the solar disc; yet a 5-arc-second pointing precision will permit some 400 observations in one pass across the Sun's dia meter. These will permit spectral analysis of individual sunspots This version of the Mariner craft is being designed to explore the vicinity of Mars. Weighing 5701b, of which 401b represents the scientific instruments, this craft will be launched by Atlas Agena next year HIGH GAIN ANTENNA \ LOW GAIN ''ANTENNA ELECTRONICS j COMPARTMENT MIDCOURSE PROPULSION- NOZZLE TELEVISION CAMERA STABILIZATION' VANE and other detail structure. A particularly challenging technical problem is to locate and record in the brief time available major solar flares which occur relatively infrequently and emanate from a small portion of the solar disc. The most advanced meteorological satellite is the Nimbus, which is designed to fly late this year or early next year. This 6751b satellite will initially fly in a circular 80° retrograde orbit so that the rate of regression of the nodes will maintain the Earth illumination relatively constant (i.e., 12 o'clock noon orbit). The Nimbus is fully stabilized to look at the Earth while its solar panels seek the Sun. Multiple videcon television cameras provide complete day. light observation of the Earth once each 24hr. Cloud pictures are stored for readout at two wide-band readout stations in Alaska and Canada, once each orbit. The follow-on series of Pioneer deep space probes is designed to monitor particles and fields at distances up to 50-90 million miles from Earth. Two probes launched ahead of and trailing the Earth, plus Earth satellites, will make possible the monitoring of a large segment of the solar sector. This small probe will deliver a data rate of 16 bits per second up to 80 million nautical miles, with much higher rates early in the flight. Mariner for Mars Our next planetary probe is designed to duplicate the Mariner 2 feat of a close planetary fly-by, but in this case the target is Mars. Although Mariner-Mars does not look much like Mariner 2, it uses much of the same technology. Some interesting variations include the following: the use of a fixed high-gain antenna, made possible by the particular Earth-Sun-planet geometric relationships for this flight; a change from Earth reference to Canopus reference for one axis; and the addition of solar pressure vanes at the tips of the solar panels to supplement and back up the gas stabilization system. The Mars mission is more difficult than the Venus mission because of increased lifetime, increased communication distance and power requirements, and a decreased solar constant. The Mariner-Mars payload will include a television telescope for surface photography. For the 1966 Mars mission, a version of this spacecraft will be fitted with a capsule to land and survive on the Martian surface. The Atlas Centaur launch vehicle will be required. The capsule landing will not be attempted unless we can be assured that it is biologically sterile. The basic spacecraft, as on the 1964 flight, will not be sterile but will use a trajectory providing less than one chance in 10,000 of impact. From a technological point of view, we have found the use of heat, gas, liquids, and radiation to achieve com plete spacecraft sterilization without degradation of reliability to be beyond the state of art at this time. Thus our lunar spacecraft such as the Ranger and Surveyor, will settle for surgically clean procedures which are now deemed sufficient for the Moon. The next series of Ranger flights are now scheduled to begin late this year with a series of four spacecraft. These spacecraft are similar to earlier Rangers, but with a high-resolution television subsystem substituted for the landing capsule and its retrorocket. This television subsystem will take pictures of the lunar surface during descent. The last full frame before impact should resolve objects of about one metre in diameter within a square 60 metres on a side. These flights will provide spot sampling of the many conflicting theoretical models of the lunar surface. Our detailed surface reconnaissance must await the Surveyor and a lunar photo graphic orbiter which we hope to soon initiate. The last US spacecraft to be covered in this paper is the Surveyor. This 5401b spacecraft weighs 2,1001b when coupled with its retro- rocket. It will fly to the Moon in a stabilized mode similar to the Ranger but with a Canopus rather than an Earth sensor. Two mid- course manoeuvres can be made with three small liquid rockets which are also used for landing. During descent, the main retro- rocket is fired by a marking radar altimeter, and attitude is main tained during this firing with the three small liquid rockets. After firing, the main retrorocket is jettisoned and the Surveyor will land under its own control using a dual doppler radar system. Once on the Moon, the surface will be observed with television cameras, seismic activity will be monitored, and local surface physical and chemical properties will be analysed. Later Surveyors may carry a small roving vehicle. When these local sites are ob served from orbit and interrelated with broad area photographic coverage, we should be in a good position not only to describe the Moon scientifically with some accuracy, but to select a landing site for man. \
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