FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1958
1958-1- - 0431.PDF
12 September 1958 rate was so low. The cross-sectional area of the swept-out channelwas quite large, so a reasonable number of "sweeper satellites" could reduce the radiation belt to tolerable limits. An analysis of the scientific results obtained with the Explorersatellites was given by A. R. Hibbs of the Jet Propulsion Labora- tory, California Institute of Technology, who reported some in-teresting facts concerning the micro-meteorite experiments con- ducted with Explorer 3, which in addition to impact microphonescarried a set of 12 wire gauges. Each gauge was approximately 1 sq cm in area and was wound with two layers of enamelledwire 17/* in diameter. Impact of micro-meteorites of approxi- mately 10/* diameter or larger causes the fracture of such a gauge.The gauges were mounted as a parallel resistance network so that the fracture of any one caused a change in the frequency of thesub-carrier oscillator of the telemetry circuit. Not more than one of the gauges was broken during the life-time of the telemetring system of Explorer 1, which had established an upper limit for the influx of particles 10/* or more indiameter of 10~3 particles sq m/sec during the period of the experiment (January 31 to April 14). Data received from Explorer 3 showed no wire gauges brokenuntil May 6. Then, between 2243 G.M.T. on May 6 and 0232 G.M.T. on May 7, two of the gauges were fractured. An inter-esting series of events followed. On May 8 and 9 erratic behaviour was observed in one of the telemetering channels on the low-power transmitter. After 0415 G.M.T. on May 9 no signal at all was picked up from this transmitter. During May 10 and 11 theMinitrack receiving stations indicated intermittent operation of the high-power transmitter, and after May 11 no further signalswere received for several days. Then, quite unexpectedly, both transmitters returned to operation. However, the low-powertransmitter carried no telemetry signal, and the operation of the interrogated beacon was intermittent. Mr. Hibbs said that the breakdown of these two transmitters(which operated quite independently, with separate circuitry and power supplies) within one or two days of each other, simply byvirtue of coincidental power failures, was unlikely. But one other piece of information must be taken into account: all other micro-meteorite data had been taken during periods of normal back- ground activity. No meteor showers were encountered. How-ever, the shower n Aquarides, which had been associated with Halley's Comet, occurred during the early part of May, reachingits most intense activity on or about May 5. It was reasonable to speculate, therefore, that some form of internal damage wascaused by the impact of meteorites. Professor L. I. Sedov of the U.S.S.R. took as his theme TheDynamic Effects of the Motion of Earth Satellites; he said that analysis carried out with Sputniks 1, 2 and 3 had shown that theperturbations of the motion of artificial satellites by the Sun and Moon were very small, and there was at present no need to takethem into consideration. In determining the sputniks' orbits, no fewer than 60,000 measurements were processed from radiomeasurements and about 400 from optical observations for Sputnik 1; 12,800 radio measurements and 2,000 optical observa-tions for Sputnik 2; and (as at July 7,1958) 52,750 radio measure- ments and 1,260 optical observations for Sputnik 3. These datawere processed on high-speed electronic machines and the elements of the orbits computed. Prof. Sedov presented several tables andgraphs showing the results of these computations. In view of the results revealed by Prof. Sedov it was par-ticularly gratifying to note from R. H. Merson's paper that the R.A.E.'s radio and optical tracking stations had achieved accur-acies which, in some cases, outmatched the Russian. Tabulated data on the orbit of Sputnik 2 included details which for onereason or another were omitted from the Soviet paper. A second Russian contribution, by Prof. V. I. Krassovsky, gavesome preliminary results obtained with Sputnik 3, which con- firmed the existence of the radiation belt. Many speakers com-plimented the Russians on their achievement of launching this 26 cwt. satellite-laboratory, which appeared to be working well inmany fields of geophysical investigation. In view of the large variety of instruments carried, however, it would be some timebefore the full range of this information could be processed. Another significant British paper, this time by T. Nonweiler ofthe Department of Aeronautical Engineering, Queen's University, Belfast, took up the question of the motion of an earth-satelliteon re-entry to the atmosphere. Equations were derived govern- ing the final descent of a satellite which had been describing a largenumber of elliptical orbits. The paper considered atmospheric retardation and the effects of frictional heating on satellites ofvarious mass and surface area. Mr. R. E. Roberson, Autonetics Division, North AmericanAviation, took as his theme General Guidance and Control Con- cepts for Satellites and Space-Vehicles. His paper was a generaldiscussion of the relation of guidance and control to astronautics, Signing-in for the Space Congress. Nearest the table, r. to /., are D. E. Koelle (W. Germany), Dr. W. von Braun (U.S.A.), K. W. Gotland (U.K.) with Mrs. Gotland, and Gordon T. Walker (U.K.). 43= Prof. S. F. Singer (U.S.A.) delivering his paper on cosmic radiation and its possible effect on manned satellites. emphasizing concepts and conceptual problems. Existing guid-ance concepts, he said, were inadequate for most future astro- nautical missions and this area deserved early and extensiveinvestigation. The arrival of more sophisticated artificial satellites was fore-shadowed by Dr. Fred L. Whipple, who considered the technical feasibility of placing an astronomical telescope in a satellite orbitaround the earth. The study was performed by members of the Smithsonian Astrophysical Observatory and the Harvard CollegeObservatory, and led to the conclusion that experiments of this kind could be realized fairly soon. The main advantage of placingan astronomical telescope in a satellite orbit, Dr. Whipple said, was that it opened the far ultra-violet spectrum much below3000A for the instrument. It was believed that ultimately, by the use of grazing incidence reflection, a telescope could function inthe short X-ray region of approximately 10A. The scheme outlined by Prof. Whipple provides for an elec-tronic scanning device and a transmitter for sending the informa- tion to the ground; also a command-receiver which controls thestabilizing, focussing and orientation equipment. Impulsive Mid-course Correction of a Lunar Shot was the titleof a paper by M. W. Hunter, W. B. Klemperer and R. J. Gunkel of the Douglas Aircraft Company, who were concerned with en-hancing the accuracy of Lunar probes by the expedient of a thrust impulse applied somewhere along the transit path. Literallyhundreds of similar investigations have been made by Douglas over the past few years in support of the Thor-Able project and similarschemes for space-research. Looking further afield, R. P. Haviland, of G.E.C.'s Missile andOrdnance Systems Department, took as his subject Consideration of the Solar Probe. It had recently become apparent, he said, thatthe Earth was immersed in the solar atmosphere. In the vicinity of the Earth this atmosphere consisted largely of ionized hydrogenof a density of about 400 particles/c.c. A solar probe offered the opportunity for investigating the solar atmosphere directly and forconducting a number of other investigations of the Sun and the various environmental factors associated with it. Assuming thata five-stage rocket was the limit of practical design, it was found that a 250,000 lb take-off weight was required to place a 50 lbpayload at the distance of Mercury. A reasonable approach would be to use liquid-propellant units for the first two stages, andsolid propellants for the last three. All manoeuvring would be accomplished in the early stages of the flight. A possible shape for the probe was a cone with the base towardsthe Sun, and with the cone angle so chosen that the sides were always shadowed. Over the range of interest, from 30 to 100 Sun-radii, it was possible to secure a body temperature between about 150 deg and 1,000 deg K. Over this range the allowable tempera-ture limit is determined more by components for instrumentation than by structural factors. A stabilization sensing system couldbe operated by the Sun's radiation. Assuming that telemetry was only required until the probe was first eclipsed by the Sun, atotal distance of about 200 million km must be bridged, for which a frequency of 1,000 Mc/s was most suitable. A narrow-bandC.W. system, such as Microlock, was proposed, with a radiating power of 2kW. Intermittent transmission of data would be em-ployed to reduce the power requirements. Haviland suggested that investigations of the kind envisaged here would form a soundbasis for the extension of the Geophysical Year.
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
