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Aviation History
1960
1960 - 0270.PDF
270 FLIGHT, 26 February 1960 Skylark Programme . . . optimum time. In August and September 1959 three firings weremade which were unpublicized at the time. The rockets carried an electron density probe and spectrometer probes to investigateelements of the upper atmosphere. Following a CO SPAR recommendation on the value of near-simultaneous launchings of rockets with related experiments in different parts of the world, a triple Skylark firing was madeduring a 36hr period on November 30/December 1, 1959, close to the World Rocket Week. The first of these carried the Belfastsodium vapour experiment, and the second used the UCL grenade sound-ranging method to measure atmospheric temperature andhorizontal and vertical wind speeds, and radar tracking of metal foil to give independent values of wind speeds (an Imperial Collegeexperiment). The third Skylark carried three experiments; those of UCL and IC as in the prior two firings, and the measurementof electron densities in the ionosphere by the Department of Electron Physics at Birmingham University. Skylark rocket and instrument hardware was displayed lastmonth at an exhibition in connection with the CO SPAR symposium in Nice (and later at the Royal Society, London).For the rocket itself two attitude control systems, now being developed, were on show; one using compressed air for controlabout pitch, yaw and roll axes simultaneously, and the other using high-test peroxide for roll control. (The instrumented head ofthe rocket separates from the motor at a height of about 40 miles, after which the head coasts to its maximum altitude before fallingback, and it is for this coasting period that the control systems are being developed.) SKYLARK FIRINGS Launch No Date 1 d) 2 (2) 3 (3) 4 (4) 7) 7 (5) 8(18) 9 (9) 10 (8) 11 (11) 12 13 14 15 16 17 19S7 Feb 14 May 22 July 23 Nov 13 1958 April 2 April 17 May 20 June 18 June 19 Sept 19 Dec 3 19S» Aug 19 Sept 17 Sept 24 Nov 30- Ded Remarks First proving firing, flat trajectory launch, no observation made Test firing Test firing Proving firing, but instrumentation and grenades fitted (77 miles height) Test firing First IGY and Gassiot firing, grenades and foil ejected at intervals (90 miles) Test firing, incorporated airglow experiment (94 miles) Special IGY night firing, engine failure Special IGY night firing, dielectric experiment (104 miles) Fourth Gassiot firing, instrumentation failure (97 miles) Fifth Gassiot firing, earned sodium experiment (75 miles) Electron density probe [•Spectrometer probes ,4. : ' - Sodium vapour experiment Temperatures and winds Temperatures, winds, electron densities Note: Figures in parentheses indicate vehicle number where known. During its fall, the head approaches terminal velocity of about260ft/sec at 20,000ft, and the parachute recovery system, when carried, is usually brought into use at just under 15,000ft. Atthis height an altitude switch completes an electrical circuit which begins the sequence of deploying the 6ft diameter stabilizingparachute and the 20ft main parachute, designed to slow the descent to about 26ft/sec. The rocket-grenade method (UCL and RAE) is used to measurethe speed of sound at heights up to 60 miles, in order to determine atmospheric temperature and wind velocities. Eighteen grenadesare carried, each containing a one-kilogram explosive charge, and these are fired from the rocket at regular intervals from 20 to80 miles altitude, exploding at a distance of about 100ft from the rocket's path. Ground equipment is located along two per-pendicular 20-mile baselines: the explosions are photographed and their positions determined to a 30ft accuracy; photoelectricflash detectors record the instant of detonation (rocket-borne flash detectors are also used, together with a telemetry link) and indaylight are linked to the ballistic cameras; and an array of sensi- tive hot-wire microphones tuned to 15c/s records the time ofarrival of the sounds of the explosions. An after-glow lasting for several minutes was produced by agrenade exploded at a height of about 80 miles. Repeated photo- graphs of this glow (believed to be produced by the reaction ofatomic oxygen with explosion products such as nitric oxide) enabled a further estimate of wind velocity to be obtained, andthe region over which this method can be used is now being investigated. Another wind-measurement technique is by radartracking of resonant dipoles ("window"): the cartridges, each containing about 120,000 strips of window, are ejected at twopoints during the ascent of the rocket, and the resulting clouds of window are tracked by ground radars. For certain experiments, the Skylark nosecone is split in two Left, the measuring head or a Birmingham University wide-apertun mass spectrometer recovered after free fall without parachute horn a height of 100 miles following a Skylark mission. Right, a Langmuit probe used for measuring ionospheric ion and electron densities (Univer- sity College, London): the small spherical electrode is carried on a 5/t spike mounted on the Skylark nose "Flight" photographs halves along its length (by a small explosive charge) and jettisoned.Equipment for one such experiment, visible in the left-hand Skylark in the heading picture on the previous page, is the five-unit photometer devised by Queen's University, Belfast, to measure the altitudes of the luminous night-glow layers through whichthe rocket is fired. This incorporates an optical section of five tubes, each containing a narrow-band interference filter and alens which images the sky on a photocathode; and a detector section whose five tubes each contain an 11-stage photomultiplierand a two-valve DC amplifier. Between these two sections is a rotating shutter. In Birmingham University's electron-density experiment, how-ever, the nosecone itself plays an important part. The forward portion of the nosecone (above the dark strip in the photographon the previous page) is in fact insulated from the remainder of the rocket. The capacitor so formed becomes part of a 5Mc/s oscilla-tor circuit, and ionospheric electron densities can be obtained by observing changes in the oscillator's resonant frequency. Another ingenious Birmingham technique employs a wide-aperture (1,000 sq cm) mass spectrometer. The measuring head of this instrument, with its associated part of the electronic circuit,is ejected from the rocket on a long cable as soon as the vehicle has passed above the major atmospheric drag region—so obtainingmeasurements remote from possible gas contamination from the pressurized sections of the rocket or from the hot motor shell.The measuring head (a recovered example is illustrated above) consists of a cylindrical cage having closed ends and a fine outergrid of wires. In operation, ions which diffuse through this outer cylindrical grid are accelerated by a known DC voltage toward?an electrostatically screened collecting-rod electrode at the axis of the cage. Information on ionic masses, which are proportional tothe transit times of ions between outer grid and the collector, is telemetred to the ground station and there de-coded. SKYLARK EXPERIMENTAL PROGRAMME Study of winds, temperatures and densities Grenade method and failing sphere experiment ... ... UCL Radar-reflecting foil ... ... ... ... IC Sodium cloud (temperatures) ... .. QU Sodium cloud (winds) ... ... ... ... QU and UCL • Pressure gauges ... ... ... ... ... ... ... RAE Study of ionosphere Dielectric experiment and ion cage ... BU ; Langmuir, sporadic-E and mass-spectrometer probes ... ... UCL ] Radio Doppler and radio pulse ... UCW and RAE Radiation experiments . \ Photometry of green line and OH bands . QU Lyman-alpha ionization chamber ... ... UCL X-ray counters and emulsion detectors ... .. ... UCL Other experiments Micrometeor microphones ... . ... QU Proton precession magnetometers ... IC Establishments indicated by initials are University College, London; Imperial College, London; Queen's University, Belfast: Royal Aircraft Establishment; Birmingham University and University College of Wales, The right-hand photograph above shows a Skylark probedevised by University College, London, to obtain information on the charge densities in the ionosphere by studying the voltage-current characteristic of a small electrode. The spherical electrode is carried on a 5ft spike ahead of the rocket nose, where the atmo-sphere is relatively undisturbed, and is protected during flight through the denser part of the atmosphere by a steel case. Asimpler version of this experiment is designed to study sporadic-E ionization and employs a flush electrode in the rocket skin. Among other experiments and equipment which have beendevised for Skylark are: the monitoring of the emission of ultra- violet light and X-rays by the Sun during ionospheric experiments(by means of ionization chambers and photographic detectors at present; by proportional X-ray counters and pulse height anaiysersin the near future); a transistorized micrometeorite detector; and a two-coil probe-mounted proton precession magnetometer.
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