The shape of the center channel determines the rate and pattern of the burn, thus providing a means to control thrust. Unlike liquid propellant engines, solid propellant motors cannot be shut down. Once ignited, they will burn until all the propellant is exhausted. There are two families of solids propellants: homogeneous and composite.
Both types are dense, stable at ordinary temperatures, and easily storable. Homogeneous propellants are either simple base or double base. A simple base propellant consists of a single compound, usually nitrocellulose, which has both an oxidation capacity and a reduction capacity. Double base propellants usually consist of nitrocellulose and nitroglycerine, to which a plasticiser is added.
Homogeneous propellants do not usually have specific impulses greater than about seconds under normal conditions. Their main asset is that they do not produce traceable fumes and are, therefore, commonly used in tactical weapons.
They are also often used to perform subsidiary functions such as jettisoning spent parts or separating one stage from another. The fuel itself is generally aluminum. The propellant is held together by a polymeric binder, usually polyurethane or polybutadienes, which is also consumed as fuel. Additional compounds are sometimes included, such as a catalyst to help increase the burning rate, or other agents to make the powder easier to manufacture.
The final product is rubber like substance with the consistency of a hard rubber eraser. Composite propellants are often identified by the type of polymeric binder used. However, PBAN propellant is the more difficult to mix and process and requires an elevated curing temperature. Both PBAN and HTPB formulations result in propellants that deliver excellent performance, have good mechanical properties, and offer potentially long burn times. Solid propellant motors have a variety of uses.
Small solids often power the final stage of a launch vehicle, or attach to payloads to boost them to higher orbits. The Titan, Delta, and Space Shuttle launch vehicles use strap-on solid propellant rockets to provide added thrust at liftoff. The Space Shuttle uses the largest solid rocket motors ever built and flown. Each booster contains , kg 1,, pounds of propellant and can produce up to 14,, Newtons 3,, pounds of thrust. Hybrid Propellants. Hybrid propellant engines represent an intermediate group between solid and liquid propellant engines.
One of the substances is solid, usually the fuel, while the other, usually the oxidizer, is liquid. The liquid is injected into the solid, whose fuel reservoir also serves as the combustion chamber. Sign in. Thanks for reading Scientific American.
Create your free account or Sign in to continue. See Subscription Options. Go Paperless with Digital. Read more from this special report: The Science of Pro Football. Bryan K. Glenn Research Center, provides the following explanation. Get smart. Sign Up. Support science journalism. The liquid hydrogen and oxygen are released into an engine where they begin to combine to make water.
Just like the solid fuel, the water vapor creates energy and steam. The steam is released to make the rocket go upwards. To get a rocket from the ground into space, rockets need both solid fuel and liquid fuel. You would think that rockets could just carry liquid fuel because liquid fuel is more efficient and gives more push when burned. However, having only liquid fuel would require a huge tank of fuel.
Instead, rockets are boosted off the ground by solid fuel. The boosters are dropped off the rocket to make it lighter, and then the liquid fuel is burned to allow the rocket to keep moving upward in space.
Therefore, rocket fuel can be categorized into solid or liquid fuels. Click here to view. BY Quora. Big Questions science Space.
0コメント