Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!samsung!noose.ecn.purdue.edu!mentor.cc.purdue.edu!mace.cc.purdue.edu!dil From: dil@mace.cc.purdue.edu (Perry G Ramsey) Newsgroups: sci.space.shuttle Subject: Re: hydrazine Summary: N2H4. Decomposes into gasses. Message-ID: <6015@mace.cc.purdue.edu> Date: 9 Nov 90 18:31:43 GMT References: <7565@eos.arc.nasa.gov> <3250005@hpnmdla.HP.COM> Organization: Department of Earth and Atmospheric Sciences Lines: 44 In article <3250005@hpnmdla.HP.COM>, stanb@hpnmdla.HP.COM (Stan Bischof) writes: > Would someone explain as concisely as possible just what hydrazine > is, how it acts as a propellant, and why it seems to be so popular? Hydrazine is N2H4. H HH H \/ \/ N = N Under the right conditions (1) heating in the presence of a catalyst, or (2) in the presence of a strong oxizizer and a catalyst, it decomposes into it's components, releasing a lot of hot gas. Typically, monomethyl hydrazine (MMH), which is formed by replacing one of the H above with a CH3, is used in the first mode. This is very useful for control thrusters because it is simple, reliable, and reasonably clean. A combination of MMH and unsymetrical dimethyl hydrazine (replace two of the hydrogens on the same side with CH3's), along with nitrogen tetroxide is used in the second mode. This is very useful for higher thrust applications, like the Titan core or the Shuttle OMS. These types of systems are popular because 1) The propellants can be stored for a long time at room temperature 2) They aren't explosive per se like hydrogen is 3) You don't need an ignition system to get the engine going. Just add propellant and maybe some heat. On the flip side, 1) They are less efficient than hydrogen 2) They are awfully toxic. -- Perry G. Ramsey Department of Earth and Atmospheric Sciences perryr@vm.cc.purdue.edu Purdue University, W. Lafayette, IN USA dil@mace.cc.purdue.edu Congress thinks that if you have nine women pregnant simultaneously, you can get one baby in one month.