Rocket propulsion
There are many different ways to accelerate spacecraft.
Below is a summary of some of the more popular, proven technologies, followed by increasingly speculative methods.
Three numbers are shown. The first is the specific impulse which is the amount of thrust that can be produced using a unit of fuel. This is the most important characteristic of the propulsion method as it determines the top speed available for the propulsion method.
The second and third are the typical amounts of thrust and the typical burn times of the method. One interesting and somewhat counterinituitive physics result is that outside a gravity well, the total energy provided by a propulsion mechanism is equal to the thrust times the time the thrust is applied. Hence, outside a gravitational potential small amounts of thrust applied over a long period will give the same effect as large amounts of thrust over a short period.
This result does not apply when the object is influenced by gravity.
Launch mechanisms
The launch of a spacecraft from the surface of a planet into space places special requirements on the methods of propulsion used. Generally speaking high thrust is of vital importance for launch, and many of the propulsion methods above do not provide sufficient thrust to be used in this capacity. Exhaust toxicity or other side effects can also have detrimental effects on the environment the spacecraft is launching from, ruling out other propulsion methods. Currently, only chemical rockets are used for the launch of spacecraft from Earth's surface.
One advantage that spacecraft have in launch is the availability of infrastructure on the ground to assist them. Proposed ground-assisted launch mechanisms include:
Referenced By
Space science
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