Posted by Sara on Monday, March 15, 2010 at 7:56pm.
I dont agree with the premise. Hydrazine is a very nice rocket fuel, which does not use oxygen. It decomposes in a violent exothermic decomposition reaction when sprayed over a catalyst.
Hydrazine can be combined with an oxidizer, often dinitrogen tetraoxide, which contains oxygen, but that is an aside. The reaction is still violently exothermic.
Now fuel cells in space are interesting, in that liquid hydrogen and liquid oxygen are carried into space to provide fuel for these cells.
Thank you
Rockets typically depend on the combustion of a fuel and an oxidizer to produce their thrust. There are many fuel/oxidizer combinations that have been used since the beginning of the space age. While there are mono-propellant propulsion systems, bi-propellant systems are used mst requiring the oxidizer to be carried into space for mission use.
The Saturn V launch vehicle used RP-1 kerosene in the S1-C 1st stage, LOX-liquid hydrogen (LH2) in the S-II 2nd stage, and the same in the S-IVB 3rd stage. The Apollo Service Module and Lunar Module Descent and Ascent Stages all used what is referred to as hypergolic propellants which ignite on contact with one another. The
specific propellants used were nitrogen tetroxide oxidizer and Unsymmetrical Dimethyl-hydrazine (UDMH) as fuel.
Common oxidizers and fuels that have been used over the years
are.................................................................Oxidizer.............................................Fuel
............................................................
Liquid oxygen..............................Liquid hydrogen
...........................................................
Liquid flourine...................................Hydrazine
.......................................................
Hydrogen peroxide............................Methyl Alchol
...............................................................
Nitric acid..........................................Aniline
.......................................................Nitrogen Tetroxide.......Unsymmetrical Dimethylhydrazine
.....................................................
(Not necessarily in the combinations shown)
The Atlas, Delta, Titan, and Saturn 1st stages use LOX and Kerosene; the Centaur and most other upper
stages, and the Space Shuttle use LOX and LH2, while the Redstone, the rocket that launched our first satellite, used LOX and 75% alcohol. LOX-LH2 is the most efficient propellant combination in use today as measured by the Rocket's specific impulse, ~455 in the Space Shuttle Orbiter Main Engines and ~466 n the latest Delta 3 2nd stage, the 1st stage still using LOX-Kerosene.
Rockets make use of either liquid or solid propellants. In either case, the two elments required to support combustion in the combustion chamber are a fuel and an oxidizer. To produce high efficiency, it is desireable for the propellants to have a high calorific value, a high density, and that they be safe to handle, and be cheap.
The most important characteristic of any fuel/oxidizer combination is the velocity of the exhaust gases as they exit the rocket motor combustion chamber, which is a function of the propellant combination's specific impulse. The exhaust velocity depends on the nature of the materials, the combustion chamber pressure, the shape of the combustion chamber and exhaust nozzle, the mixture ratio, and the pressure of the surrounding atmosphere. While firing in the atmosphere, a rocket's thrust is degraded by as much as 15% due to the backpressure caused by the atmosphere.
A solid propellant motor consists of a rubbery, or plastic-like, mixture of ingredients that have been processed, blended, and molded into a specific shape inside a motor casing. The ingredients include fuel, oxidizer, binder, curing agent, and burn rate catalyst.
Those ingredients used in typically small amounts are referred to as additives and usually fulfill functions
other than those of the primary fuel and oxidizer. Typical solid propellant fuels are aluminum powder and
beryllium powder. Typical oxidizers are ammonium perchlorate and ammonium nitrate, among others.
Liquid propellant motors are far more efficient than solid propellant motors. The measure of a rocket motor's efficiency is its specific impulse. The best liquid propellant ombination in use today, on the space shuttle, is liquid hydrogen and liquid oxygen, with a vacuum Isp of 453 seconds. The solid propellant boosters used for the Space Shuttle launch have an Isp of 263.
While many mono-propellants exist, booster stages and on orbit systems typically use bi-propellant propulsion systems. Methyl nitrate, nitromethane, nitroglycerin, ethyl nitrate, hydrrozine, hydrogen peroxide, and ethylene oxide are a few mono-propellants. Peroxide was used in the German V-2 and the U.S.Redstone.
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