NASA's Deep Space 1 space probe was launched on October 24, 1998. During a highly successful primary mission, it tested twelve advanced technologies in space, including ion propulsion. The spacecraft's ion engine provided about ten times the specific im pulse (ratio of thrust to propellant used) of an ordinary liquid-fuel engine. As an extension of its original mission, Deep Space 1 encountered the asteroid Braille and the comet Borrelly. It returned the best images and other data ever obtained from a comet.
The Deep Space 1 spacecraft used its ion engine to maneuver close enough to Comet Borrelly to obtain detailed photographs of its surface.
This is the highest resolution photo of the comet that was obtained by Deep Space 1.
Electricity, generated by nuclear power perhaps, could also make a fluid hot enough to vaporize. This is the same way that the electric element on a kitchen range can turn the water in a teakettle into steam. The "steam" from such a rocket—which may be at a temperature of thousands of degrees—can be used to propel it.
Scientists at NASA's Marshall Space Flight Center in Alabama have been working on several unusual forms of rocket propulsion. One obtains its energy from nuclear fusion. Unlike fission, in which an atom is split to release energy, fusion combines two or more atoms to create a heavier atom. It releases tremendous amounts of energy in the process—energy that could propel a spaceship. The creation of fusion
energy is so efficient that it would be like driving a car 7,000 miles (11,265 km) on a single gallon (3.8 liters) of gas. This energy could create power for an ion thruster. Also, the superhot plasma created by fusion could be ejected from a nozzle to propel the spaceship directly.
Another exotic source of energy is from antimatter. Antimatter is identical to normal matter, except that the electrical charges of its atomic particles are reversed. A normal proton is positive where an antiproton is negative. When normal matter and antimatter meet, they annihilate each other in a huge burst of energy. If this energy were to be channeled out the back end of a spaceship, it could produce thrust. Although scientists believe that antimatter may exist freely in the universe somewhere, the only samples so far have been produced in laboratories.
The beauty of matter/antimatter propulsion would be that a tiny amount of matter would produce a vast amount of energy. An antimatter-propelled spaceship could attain huge speeds while having to carry very little fuel. Of course, the main problem facing engineers working with antimatter is how to store a substance that explodes instantly the moment it touches anything.
Other unique rockets use conventional fuels but with radically redesigned engines. The plug nozzle, or aerospike engine, for example, is nothing more than a conventional rocket engine turned wrong side out. The flow of gases from the burning fuel clings to the outside of the curved nozzle. The advantage to the plug nozzle is that an engine can be much shorter than a conventional one. The savings in weight means the rocket can carry more fuel.
Other engineers have concentrated on ordinary rockets that use extraordinary fuels. Different fuels may be more powerful or less expensive to make or safer to store. For example, SpaceShipOne, the
Bombs are M ejected from the base of the rocket.
The series of explosions propel the rocket forward.
One of the most unusual reaction-propelled spacecraft ever suggested was Project Orion. A series of nuclear bombs were to be ejected through a hole in a huge steel plate. When the bombs detonated, they would force the spacecraft forward. A model (left) was tested by NASA and the Atomic Energy Commission using conventional explosives. But international treaties regarding aboveground nuclear testing, as well as fears about radioactive pollution, put a stop to the project before full-scale testing could begin.
Scientists think that future spacecraft may have antimatter engines. When matter and antimatter particles are combined, they mutually annihilate one another in a tremendous burst of energy—about 10 billion times more powerful than the energy released by ordinary rocket fuels. Such spacecraft are still many years in the future, however. The main problem is that antimatter doesn't exist in nature. It has to be manufactured. So far, scientists have only been able to create a few particles of antimatter. Also, scientists would have to find a way to store a substance that can't be allowed to come into contact with ordinary matter.
first private spaceship ever developed—which made its first flight into space in 2004—employed a rocket motor that burned solid fuel with a liquid oxidizer. The fuel was made of rubber processed from old automobile tires. The oxidizer was nitrous oxide, best known as an anesthetic used by doctors. A rocket engine that uses a solid fuel and a liquid or gaseous oxidizer is called a hybrid rocket. Unlike ordinary solid-fuel motors, such as those that boost the space shuttle, an engine like SpaceShipOne's can be turned on and off. (Some new solid-fuel motors can be turned on and off at will.)
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