Spacecraft and Space shuttles, and their power systems

Spacecraft and Space shuttles

there is only one basic difference between shuttle and spacecraft- spacecrafts could be manned or unmanned whereas shuttles are always manned.

The different types of spacecrafts classified on basis of application are:

•  Flyby spacecraft  They followed a continuous solar orbit or escape trajectory so as not be captured in the planetary orbit. Eg-mariner 2 sent to Venus.

•  Orbiter spacecraft  It is a spacecraft that is designed to travel to a distant planet and enter into its orbit. Eg-Galileo, which entered Jupiter orbit .

•  Atmospheric spacecraf  These spacecrafts are used to study the atmospheric condition of other planets and record the data.  Eg- huygen’s which was carried to Saturn’s moon titan by spacecraft Cassini )
•  Lander spacecraft These spacecrafts are designed to land on the surface of a planet and sent data back to the earth. Eg- mars pathfinder.

•  Penetrator spacecraft These spacecrafts are designed for penetrating the surface of a body, such as a comet. Eg- twinDeep space 2 penetrators .

•  Rover spacecraft They are semi-autonomous roving vehicle that are steerable from earth. They are sent to the planet for taking images and analyzing soil. Eg- sojourner rover

•  Observatory spacecraft it is a spacecraft that does not travel to a destination but occupies earth or solar orbit. Eg- jpl sirft Observatory.

•  Communication spacecraft These are earth orbiting communication spacecrafts, which are used to transfer data. Eg- TDRS 10.

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Power System of Spacecraft and Space shuttle

three types of power generating system is used in spacecrafts

1.Solar Cell: The craft electrical system uses solar cells to directly convert sunlight to electricity. Large numbers of cells are assembled in arrays to produce high power levels. This method of harnessing solar power is called photovoltaic. But it’s not easy for those crafts what goes so far from sun.
2.Radioisotope thermoelectric generators, or RTGs: It uses the fact that radioactive materials, encased in a sealed shell, will generate heat as they decay into non-radioactive materials.
3.Fuel Cell: fuel cells are used to generate power for probes, satellites and space capsules. And specially at the time when sun light doesn’t available.
1. Solar Cell:
A solar cell(photovoltaic or photoelectric cell) is a solid state electrical device that converts the energy of light directly into electricity by ‘photovoltaic effect’. where photovoltaic effect directly related to the photoelectric effect.
(here’s a link for understanding its principle http://www.sony.net/SonyInfo/technology/technology/theme/solar_01.html)
2. Radioisotope thermoelectric generators, or RTGs
A radioisotope thermoelectric generator (RTG, RITEG) is an electrical generator that obtains its power from radioactive decay. In such a device, the heat released by the decay of a suitable radioactive material is converted into electricity by the ‘Thermoelectric effect’  (‘Seebeck effect’, for RTG) using an array of thermocouples.
[Radioactive decay is the process by which an atomic nucleus of an unstable atom loses energy by emitting ionizing particles. 238Pu, 90Sr, 210Po, 242Cm, 244Cm, 241Am are used basically for RTGs ]
3. Fuel Cell
•A fuel cell is a device that converts the chemical energy from a fuel into electricity through a chemical reaction with oxygen or another oxidizing agent. (basically hydrogen)
•Fuel cells come in many varieties; however, they all work in the same general manner. They are made up of three segments which are sandwiched together: the anode, the electrolyte, and the cathode.

The most important design features in a fuel cell are:

1. The electrolyte substance. The electrolyte substance usually defines the type of fuel cell.

The fuel that is used. The most common fuel is hydrogen.

2. The anode catalyst, which breaks down the fuel into electrons and ions. The anode catalyst is usually made up of very fine platinum powder.

3. The cathode catalyst, which turns the ions into the waste chemicals like water or carbon dioxide. The cathode catalyst is often made up of nickel.

few common type of fuel cells are:

•Polymer Electrolyte Membrane(PEM) fuel cells
•Direct Methanol Fuel Cells
•Alkaline Fuel Cells (normally use in space crafts and shuttles)
•Phosphoric Acid Fuel Cells
•Molten Carbonate Fuel Cells
•Solid Oxide Fuel Cells
•Regenerative Fuel Cells
*basic working system of a fuel cell-

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