Spacecraft experiments

Spacecraft experience transient accelerations due to a number of events. These include dockings of spacecraft, attitude (orientation) adjustments, discharge of wastewater, the dissipation of spacecraft heat by boiling off of cooling water, etc. These events have a wide variety of duration, acceleration level, and frequency of occurrence. For example Space Shuttle waste water dumps occur about once a day with an acceleration of lO g. Space Shuttle attitude adjustments typically occur every few minutes with a duration of about 0.25 seconds and an acceleration of s ut 4 10 g. What these transient accelerations have in common with quasi-steady accelerations is that no vibration isolation can be used. They all involve a change in the spacecraft s... 

In the future, we expect to see many more radio astronomy spacecraft experiments. Spacecraft experiments will allow the submillimeter spectral range to be observed without hindrance from the terrestrial atmosphere. Planetary spectroscopy in the submillimeter spectral range is expected to reveal new information about the upper atmospheres of the planets. The ESA ROSETTA spacecraft... 

The first experiments with the thermal electric engine were conducted in Russia in 1929 by its inventor, Valentin P. Glushko, who later became a world-famous authority in rocket propulsion. For more than forty years, the United States and Russia have devoted many resources to research and development of various kinds of EREs. First tested in space by the Russians in 1964, these engines have found some limited applications in modern space technology. For more than two decades Russian weather and communication satellites have regularly used electric rocket engines for orbital stabilization. The first spacecraft to employ ERE for main propulsion was the American asteroid exploration probe Deep Space 1, launched in 1998. The performance of... 

Structural applications include thermal protection shingles for spacecraft and exhaust nozzles for turboprop engines. The exhaust nozzle was successfully tested in flight with the Do 228 airplane. The flight tests are now continuing to get experience with the long term use of CMC s. 

In spite of the usually low cooling efficiencies (see the exercise above), recent experiments have demonstrated an anti-Stokes cooling from room temperature to 77 K within a certain internal volume of Yb + doped fluorochloride and fluoride glasses under high photon irradiances (Fernandez et ai, 2000). Future practical applications of optical cooling of solids include cooling systems for spacecraft electronics and detectors, as well as for superconductive circuits. 

So far we discussed the case for 4He escape. 3He escape must at least be as effective as 4He the 4He lifetime against Jeans escape can be shown to be 70 times greater than the 3He lifetime. In the case of 4He, an inflow flux into the atmosphere is essentially the radiogenic 4He from the solid Earth. However, a flux from the interplanetary space may become important in the case of 3He inventory. From He implantation experiment on metal foil collectors in the Skylab, a spacecraft operated in a circular orbit at the altitude of 443 km from 1973 to 1974, Lind, Geiss, and Stettler (1979) concluded that the solar wind 3He precipitating from the magnetosphere to the upper atmosphere is comparable to 3He degassing flux from the solid Earth. 

Future spacecraft missions to solar system objects are primarily being oriented towards remote-sensing experiments, in contrast to the soft-landed in situ experiments and sample-return initiatives during the 1970 s and 1980 s. Because reflectance spectroscopy has become one of the most important investigative techniques in the planetary sciences, current and planned space missions for the 1990 s and 21st century should include visible and near-infrared spectrometers in their instrument payloads. Reflectance spectral measurements from space would provide more favourable viewing geometries, eliminate problems due to telluric water and C02, and improve the resolution of areas scanned on a nearby planetary surface. 

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