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Aviation History
1961
1961 - 0937.PDF
FLIGHT, 13 July 1961 37 SPACE RADIO MEETING IN OXFORD RADIO Techniques and Space Research," the theme of the1961 Convention of the British Institution of RadioEngineers held at Oxford during July 5-9, produced over40 papers concerned with the scientific, engineering and electronic aspects of the subject. Extracts from the papers by Mr D. J.Lyons of the Royal Aircraft Establishment and by Mr John D. Nicolaides of the US Bureau of Naval Weapons are discussed inthe preceding and following articles; other points from the Oxford meeting are reported here. In The Canadian Defence Research Board Topside SounderSatellite, R. C. Langille and J. C. W. Scott described the ingenious extending aerials devised for this satellite, which is to be launchedinto a 625-mile, 80° orbit by a NASA Thor-Agena vehicle during next year. Rather similar in concept to a carpenter's steel rule, theseaerials comprise thin steel tapes which are unrolled and extended by an electric motor. Four of these types are used to erect two dipoleaerials, one 150ft and the other 75ft from tip to tip. An example of one of these aerials, built by de Havilland Aircraft Co of Canada,was demonstrated by Mr G. K. C. Pardoe at the meeting. The mechanical, structural and electrical properties of theseaerials are to be tested under flight conditions, the Canadian authors disclosed, by means of a Javelin research rocket. Two ofthe 73|ft sounding aerials will be launched in a Javelin and ejected at high altitude. The rocket will be de-spun to about 329 r.p.m.before the experiment in order to give a realistic dynamic environ- ment during ejection of the aerials. The maximum expected bend-ing moments on the aerial tubes will be applied in the transient manner anticipated in the satellite experiment—a loading whichwould be extremely difficult to reproduce in a ground test. Con- struction of a Javelin nosecone with aerials and instrumentation iscurrently under way. The satellite package will be a near-spheroid approximately 42inin diameter and 34in high, and weighing some 2751b. A large part of the surface is covered with 6,480 silicon solar cells which willcharge the nickel cadmium batteries. Except for the electronics the satellite is being designed and built by de Havilland Aircraft Co ofCanada, to specifications supplied by the Defence Research Tele- communications Establishment. Electrical design of the aerials isby Sinclair Radio Laboratories. The Canadian satellite experiment is one of two authorized bythe US National Aeronautics and Space Administration to sound the upper side of the ionosphere by radio means. It will be a sweep-frequency sounder covering the frequency range from 1.8 to 11.5 Mc's, similar in operation to that of a ground ionospheric station.The second satellite, being developed in the USA, will sound on six frequencies in rapid succession. The data collected by bothsatellites will be telemetered to the ground and received at the same ground stations. The DRB satellite will concentrate on high-latitude problems, while the fixed-frequency sounder will be con- cerned more with studying the ionosphere to the south and, inparticular, along the 75° parallel. Mr D. J. Lyons, Acting Head of the Guided Weapons Depart-ment of the Royal Aircraft Establishment. Farnborough, presented a paper on Satellite Launching Possibilities. The general section of this paper gave the following description of methods of injectioninto orbitr Mr Lyons' remarks on launching by aircraft are par- ticularly interesting in view of the American views on this topicreported on page 39, and his discussion of continuous-thrust techniques is also significant. Practically all known satellite launching attempts [Mr Lyonsstated] have been made with all-rocket systems. In such a system the initial launching is vertical, as maximum efficiency is achieved withvery low initial acceleration (sometimes as low as \ g), but as the orbital velocity is required in a more or less horizontal direction theflight path is curved towards the horizontal as soon as is possible in order to start acquiring horizontal velocity. The rate of turn islimited by requirements to keep the speed down whilst the booster is still in the atmosphere in order to keep aerodynamic heatingand loads within reasonable proportions. As the stages burn out they are jettisoned and the succeeding stages ignited just before,during or after separation. In the most usual system all but one of the stages are burnt inrapid succession and have fairly high mean accelerations, firstly so as to derive the maximum possible energy-increase for givenmomentum increases and secondly to minimize the gravity losses. Since, however, this results in burn-out at a fairly low altitude andthe launching vehicle must enter the required orbit under power, a coast period is usually inserted between the penultimate stage andthe end stage while altitude is being gained. The final stage is ignited near orbital altitude to increase the energy to that needed toremain in the desired orbit. This might be termed the thrust-coast-thrust type of injection.It has the added attraction that on a simple mathematical approach it has the virtue of being the most efficient method of injection fromthe point of cessation of thrust of the first stages; its disadvantages are also clear. Orientation systems have to be carried to holdspatial axis references for controlling direction of the end-stage thrust, and there may be additional problems caused by the neces-sity to start the end-stage engines from conditions of free fall when liquids will not be nicely placed in their required position in the"bottom" of the tanks. An alternative method which has been evaluated in UK has beenthe elimination of the coast period and the substitution of a con- tinuous but very low thrust end stage so that cessation of this thrustand attainment of initial orbit conditions are met at the same time. The advantages of this method are numerous:(i) The low thrust lowers the engine weight very considerably, which in turn permits increase of nozzle size so that greater pro-pellent efficiency (higher specific impulse) can be obtained. (ii) The continuous-thrust motor can and must be used to orientthe stage so that a separate orientation system is unnecessary. (iii) For reasons of (i) and (ii) the dead weight is reduced and theresulting increase in performance offsets the simply mathematically calculated loss in performance. (iv) Light-up problems can be eliminated if desired.(v) Loss of cryogenic propellants due to solar heating, heat leak- age, etc, can be avoided or minimized during the continuous-thrustprogramme (this is not completely possible during the coast period). in the paper "An Economical Satellite Launching Technique for Conducting Radio Research in Space" by Mr John D. Nicolaides, the launching of satel- lites from aircraft was proposed. This diagram illustrates the launch sequence envisaged and the "kick in the apogee" firing of the fourth-stage motor to obtain the required orbit. Mr Nicolaides' views on space research, as presented at the Oxford meeting and on other recent occasions, are the subject of an article on page 39 Perigee = 1,000 Miles Altitude Orbit Without "Kick In The Apogee" Resultant orbit Tinner Fires 4th stage Near Apogee = 2,300 Miles 3rd Stage Burnout Horizon Detected2nd Stage Ignition By IR Horizon Scanner Look Angle 2nd Stage Burnout 3rd Stage Ignition in Sequence 1st stageBurnout Spin Stabilization Light-Off1 st Stage, (Timer Actuated ,-*=»•*• Look Angle Coast To Apogee
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