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Aviation History
1960
1960 - 0269.PDF
FLIGHT, 26 February 1960 269 Missiles and Spaceflight . . . SKYLARK PROGRAMME THE planning of experiments for the first Anglo-American satellite,and US interest in using Skylark sounding rockets in an international project, have recently focussed attention on the British Skylark pro-gramme. This article, illustrated with photographs of Skylark equipment exhibited at last month's COSPAR Symposium in Nice, describes thevehicle, its history and its test programme. THE value and practicability of a programme of upper-atmosphere research being undertaken by Britain was firstdiscussed at a meeting of the Gassiot Committee of the Royal Society as far back as October 1953. These discussionsfollowed a conference held at Oxford during the previous summer, when a number of leading American rocket technicians had givenlectures on the techniques and results of US experiments. Dis- cussions were then held between representatives of the committeeand the Director of RAE, which were followed by joint repre- sentations to the Treasury, as a result of which a financial grantwas obtained. The Royal Aircraft Establishment undertook to develop rocketvehicles suitable for carrying out the desired experiments. The first of these is the Skylark, designed to carry a scientific pay-load of 100-1501b to altitudes over 100 miles. It is basically a very simple vehicle, cylindrical in shape with a conical nose,25ft long and 17.4in in diameter. It is dart-stabilized by three large fixed fins and is uncontrolled in flight. Power is by a Ravensolid-propellant motor giving a thrust of 12,0001b for about 30sec, ~exact Period being determined by the shape of the charge.The nose section is made in two parts; the 65in long cone and a 30in parallel bay. The cone provides 2.7 cu ft of payload spaceand the bay a further 2.3 cu ft. Both cone and bay can be pressurized independently. Information obtained in the rocket is transmitted to the groundreceiving stations by a telemetry sender. The standard transmitter inn8 an AM/FM. system on 465Mc/s and is capable of givingnU accurate readings per second for up to 24 instruments. Elec- Left, the instrumentation section of Skylark No 13, not yet fired, with five-tube photometer (upper section) devised by Queen's University, Belfast, to determine altitudes of luminous night-glow layers. Visible in the Skylark on the right are the (lower) grenade bay assembly, in which 18 grenades are carried; and the insulated nosecone used in the Birmingham electron-density experiment. The base ring of each round would be bolted to the forward end of the Raven motor "Flight" photograph trical power is provided by special lightweight batteries; thesedrive rotary convertors where necessary. By agreement with the Australian Department of Supply andwith the co-operation of the Weapons Research Establishment authorities the Skylarks are launched from Woomera in SouthAustralia. A special 100ft cradle, supported on gimbals in a tripod base, was developed for launching them. Both radio and optical instruments are used to track the vehiclesand so obtain trajectory information. For the radio tracking, a microwave beacon is carried in the rocket, and two widelyseparated ground receivers lock-on to the signal and provide a continuous record of the relative azimuths and elevations. The radio Doppler system is also used to give velocity andposition information. A ground transmitter sends a continuous wave signal to the rocket; a transponder in the rocket doubles thereceived signal and re-broadcasts it to the ground. A ground receiver compares this received frequency with the original trans-mission suitably doubled and obtains a Doppler beat frequency which is a measure of the radial velocity of the rocket with respectto the receiver. If three receiving stations are employed the rocket's velocity in space may be computed, and its position canbe determined with accuracy after summing the Doppler beats along each radial line. For optical tracking, the rocket is photographed in flight byhigh-speed cameras and by kine-theodolites, the former giving a record of vehicle behaviour during the launching phase. Severalwidely spaced kine-theodolites are used, each of which photo- graphs both the rocket and a set of elevation and azimuth dials aswell, so that the rocket position can be calculated using triangula- tion methods. By combining the results of these three systems, graphs of therocket's trajectory, speed and acceleration can be plotted, and from these can be obtained aerodynamic information about theflight behaviour of the vehicle up to its maximum speed of five or six times the speed of sound. In fact the rocket does more than describe a trajectory. It rolls,pitches and yaws for a variety of reasons: rolling arises from slight imperfections in the structure, pitching and yawing may beset up by the varying winds encountered, and these motions may develop and become quite large as the rocket leaves the effectiveatmosphere, actually causing it to tumble. To follow these additional motions both in the atmosphere andabove its effective limit, gyroscopes and accelerometers are carried inside the rocket; these instruments measure the changes inorientation and the forces causing them, passing the measurements in the form of changes of voltage or inductance to the telemetrysender in the rocket which transmits the information to the ground. There the results are extracted, displayed and photo-graphed for careful analysis back in the laboratory. The Skylark was Britain's first venture into the realm of researchrockets, and six rounds were reserved for proving trials and to enable missile know-how to be obtained before the actual scien-tific programme commenced. The first vehicle was fired on February 14, 1957. In this no attempt was made to achievemaximum height and, in fact, the launching cradle was depressed as far as possible and the rocket flew a long, flat trajectory. Rounds2 and 3 were also proving firings. These three firings proved the general performance of the vehicle and its motor, and attentionwas then turned to trials of equipment and instrumentation and the associated ground equipment. Skylark No 4, in addition toroutine instrumentation, carried equipment for four separate experiments involving grenades, metal foil "window," a dielectricexperiment and pressure gauges. Fired on November 13, 1957, it reached a peak altitude of 77 miles. Skylark No 7 (Launch No 6), fired on April 17, 1958, to analtitude of 90 miles, was the first British contribution in this field to the International Geophysical Year. The rocket carried 18grenades and fourteen cartridges of "window," and incorporated an insulated cone for ionospheric experiments. Following the recommendation of the Washington Rocket andSatellite Conference to establish a special "rocket interval" during June 1958, two firings were made on the target date of June 18/19.On the first of these, Skylark No 18, the rocket engine failed— the only such failure in a total of 17 firings. The secondlaunching, arranged within 24 hours of the failure, achieved the desired results. Another notable success in rocket handling was the firing, onDecember 3, 1958, of Skylark No 11 for a special experiment. This required the rocket to be fired when the Sun was at a depres-sion of 6°, and launching was achieved within two minutes of the
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