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Aviation History
1988
1988 - 1858.PDF
Tethered Satellite's second mission, set for 1993, will investigate the Earth's upper atmosphere the conductive tether, and is expected to produce up to 4kW of power. A non-conductive tether, 100km long, will be used for the second mission, in which the satellite will be lowered to 120km. This alti tude has previously been visited productively only by sounding rockets, for short periods. The satellite will be aerodynamically upgraded for manoeuvre control, by means of a "tailplane". It will conduct a variety of scientific studies, including direct measure ments of magnetospheric, ionospheric, and atmospheric coupling processes; thermo- spheric winds; neutral gas composition and temperature; ion composition; temperature and density; and ion drift velocity. This data is needed to improve global models of atmo spheric chemistry and dynamics, to enable scientists to evaluate phenomena such as the hole in the ozone layer above the Antarctic. Many other TSS applications have been identified. These include the space elevator, crawling along a deployed tether and provid ing variable microgravity levels; transport ation between two tethered bodies; a system for e.g. management; a tether inspection and repair device; and a carrier of re-entry probes. A space elevator test module has been designed, and is a candidate for a later TSS mission. This 70kg rectangular box, measuring 0 • 65m x 0 • 65m X 1 • 05m, would travel along the tether at a speed of 2m/sec. An advanced system deployed from the Space Station, primarily for microgravity experiments, could provide a best micro- 7^ Shuttle Tether TSSsatellite gravity level of about 10"8g. It would weigh about five tons, with three tons of payload, and would have a cruising speed along the tether of lm/sec. A secondary cable could provide 12kW of power and a 40 megabytes- per-second datalink. The Space Station elevator could also be used for transportation to a platform, and to provide overall centre- of-mass management. A tethered system could generate DC electrical power to supply onboard loads, or, in the reverse mode, to obtain an electro magnetic propulsive thrust to change a spacecraft's orbit. Using a 10km to 20km- long electrically conductive tether, with a satellite at its end, the Shuttle could demon strate the feasibility of producing up to 1MW of power or up to 200N of thrust in an exten sion of the first TSS mission. Reversal of the power generation process could generate thrust. Current, fed into the tether from an onboard power supply, runs up the tether, creating an electromagnetic propulsive force which could be used to change the spacecraft's altitude. A proposed test mission would use a 20km disposable tether to boost a small payload from Shuttle into a higher orbit, while another would inject a payload into a lower orbit for re-entry. A Shuttle-based windtunnel demonstra tion could use a lOOkm-long tether and an aerodynamic model, which would be trawled through the upper atmosphere at about 100km. Exposed for long periods, the model would yield a wide range of data nearly impossible to obtain in conventional wind- tunnels, including regimes of low Reynolds numbers and high Mach numbers. The model would record or transmit data on such factors as heat transfer and drag coefficients, airflow, and turbulence, yielding informa tion about the aerothermodynamics of the upper atmosphere for the next generation of aerospace vehicles. A tethered system combined with the elevator concept could control the re-entry of recoverable capsules, or control the disposi tion of unwanted hardware during a destruc tive re-entry, without the need for retrofire. The capsule would be moved down the tether and released at a finely-controlled point. This application could be evaluated by the Shuttle, using a capsule weighing 80kg and a 30km tether. Such a system could be applied to the Space Station. A Space Station-elevator- released re-entry system would comprise a 70km tether and seven-ton elevator, support ing a three-ton re-entry capsule whose 36 FLIGHT INTERNATIONAL, 16 July 1988
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