Spacecraft power generation

Its high melting point also makes it useful for metal electrodes in glassmaking furnaces. Molybdenum s high resistance to electricity makes it useful in high-temperature filament wires and in the construction of parts for missiles, spacecrafts, and nuclear power generators. 

Fuel cells have been used to provide electrical power for spacecraft since the 1960s. In recent years, fuel cell technology has begun to mature, and batteries made up of fuel cells will soon be or are now available for small-.scale power generation and electric automobiles. Use your Web browser to connect to http // chemistry.brookscole.com/skoogfac/. From the Chapter Resources menu, choose Web Works. Locate the Chapter 18 section and click on the link to the Scientific American Web site article on fuel cells. Describe a proton-exchange membrane from the information and links given. 

Nakamura, T., 1992. Survivable Solar Power-generating Systems for Use with Spacecraft. Brevet, US 5089055. 

Electrical Power. The electrical power system is responsible for power generation, capture, or storage, plus delivery of conditioned electrical power to all parts of the spacecraft. Power may be generated by onboard reactors such as fuel cells, or captured from sunlight by solar panels. Power from sunlight is stored in rechargeable batteries for later use when the spacecraft is in eclipse, or for times when power demand temporarily exceeds the total available from solar panels alone. Power-conditioning circuits are necessary to pro dde electricity at the volb e, current, and stability required by individual components. 

Despite the potential failure modes discussed above, reliable gas foil bearing experience has been demonstrated in the aircraft and power generation industry. Table 9-7 shows the commercial experience for various metrics, and compares them to the projected Prometheus concept. Although the Prometheus spacecraft would be unique in that no maintenance would be possible, it is evident from the table that the planned design fits within the operational experience of current state-of-the-art gas foil bearings. 

The AEG sponsored research ia the program known as Systems for Nuclear AuxiHary Power (SNAP) as early as the 1950s. Most of the systems developed iavolved the radioisotope plutonium-238 as a heat source for a thermoelectric generator. Such electrical suppHes permitted radio transmission to earth from spacecraft such as Pioneer and l qyager. 

Radioisotopes have important commercial applications. For example, americium-241 is used in smoke detectors. Its role is to ionize any smoke particles, which then allow a current to flow and set off the alarm. Exposure to radiation is also used to sterilize food and inhibit the sprouting of potatoes. Radioisotopes that give off a lot of energy as heat are also used to provide power in remote locations, where refueling of generators is not possible. Unmanned spacecraft, such as Voyager 2, are powered by radiation from plutonium. 

There are no major commercial uses for curium because of the extremely small amount produced. In the future, the most important use of curium may be to provide the power for small, compact thermoelectric sources of electricity, by generating heat through the nuclear decay of radioisotope curium-241. These small, efficient power sources can be used in individual homes or remote regions to provide electricity to areas that cannot secure it from other sources. It could also be used as a source of electricity in spacecraft. However, today curium s main use is for basic scientific laboratory research. 

Radioactive isotopes that give off a lot of energy as heat are also used to provide power in remote locations, where refueling of generators is not possible. Unmanned spacecraft, such as Voyager 2, are powered by plutonium produced in nuclear reactors. 

For closed-cycle applications, such as for spacecraft, submarines, or transportation vehicles, the combinations of lightweight, reasonable power density, and compact size are favorable features in comparison with equivalent-capacity battery-based systems. In the International Space Station, for example, both electricity and water are provided by fuel cells. Fuel cells have not only been used in space exploration, but also in submarines (because they generate no noise or vibration). They have also been used to recover the energy from methane that is generated by wastewater, by garbage dumps, and more recently in automobiles as an alternative to the IC engine. 

---