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Aviation History
1964
1964 - 2123.PDF
144 FLIGHT International, 23 July 1964 PROGRESS WITH UK-3 ... have been incorporated. Other modifications have come to light as the experimenters have investigated more closely their aerial requirements and their compatibility with each other. It is now fairly certain that the current design of UFC-3 (see drawings, p. 143) will remain unchanged and will prove suitable for the experiments and associated electronic equipment. It will be noticed from the drawings that, compared with the initial design, the Sheffield experiment now employs a loop aerial in place of a ferrite rod; the Cambridge loop aerial has been enlarged and the shape of the booms has been slightly changed. The spacecraft carries 8,000 solar cells, sufficient to provide power for an operating life in orbit of one year. A spin table and a balancing machine have been ordered by BAC and should be delivered by September, in time for the Dl satellite to go on test. A number of smaller items of mechanical test gear have been assembled, and prototype solar-cell trays have been tested on a special vibration rig. A 5ft x 3ft diameter vacuum chamber at Stevenage will be used for components and sub- assemblies, but full-scale thermal vacuum tests on the complete satellite will be made at RAE in a new chamber which has been ordered from the USA for delivery next year. Useful work on the internal heat balance of the satellite, and on the thermal control of external equipment and surfaces, has already been completed at Stevenage. The main part of the thermal control work has involved the prediction of equipment temperatures inside the spacecraft. Initially this entailed the "longhand" pre- paration of radiation coefficient diagrams, using a quarter-scale satellite model: more recently, computer programmes for heat inputs and radiation exchange have been provided by NASA and are making possible much faster and more detailed computations. Expected temperature ambits of external equipment on the satellite have been investigated, including solar cells, ferrite rod aerials, loop aerials, booms, skins and sensors. Some redesign has resulted, but generally the temperatures have been acceptable. Predictions have also been made of the emissivity/absorptivity ratio of the satellite body. To meet the requirements of thermal control, a double skin is being used on the top cone and base surfaces of the satellite. This eases the problems of thermal control when the spacecraft is end-on to the Sun, and enables the outer skin to be finished in small areas—an easier and cheaper process. I Examination of satellite dynamics has included a detailed invest- igation of the dynamics of the "yo-yo" de-spin mechanisms. Studies have also been carried out into the dynamics of loop and whip aerials under the influence of nutation, the de-spin character- istics of ferrite rods and other ferritic and ferrous materials in the spacecraft, and the perturbations resulting from solar pressure, magnetic moment and gravity gradient. Static and dynamic stressing and vibration analyses are continuing. Planned time schedule for the five UK-3 satellites and three ground-support vehicles now being built by British Aircraft Corporation. The satellites comprise development models (Dl and D2), a prototype (PI) and two flight models (Fl and F2); the vehicles consist of two ground checkout trailers (Set I and Set 2) and a workshop vehicle (VV/V). One of the checkout trailers is scheduled to appear at this year's SBAC show OPERATIONAL iCHECK CHAMBER TRIALS! RETAIN FIT CHECK AT DALLAS
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