Date: 17 Sep 90 00:23:14 GMT
From: van-bc!rsoft!mindlink!a752@ucbvax.Berkeley.EDU  (Bruce Dunn)
Subject: Re: red fuming nitric acid power

> heskett@titan.tsd.arlut.utexas.edu writes:
> Red fuming nitric acid (a.k.a. RFNA) was used on the Wac Corporal, if
> I remember correctly, and the Aerobee series (not their solid-fuel
> boosters, of course).  Actually, the Aerobee series used IRFNA...I
> forget what the I stands for.


     The I in IRFNA (Inhibited Red Fuming Nitric Acid) stands for Inhibited.
Red fuming nitric acid is a good oxidizer (it contains a lot of nitrogen
tetroxide by weight - one chemist commented that red fuming nitric acid wasn't
so much a chemical, as a chemical system).  However, it is fiercly corrosive,
and eats the tanks of any missile it is stored in.  Early designs using red
fuming nitric acid therefore had to put the oxidizer in the rocket just before
firing.  However, the fumes (nitrogen oxides etc.) are very poisonous, making
this a not particularly pleasant task.  After some years of research, it was
discovered that if a trace of hydrofluoric acid were added to the nitric acid,
metal surfaces would form a protective metal fluoride film.  Inhibited red
fuming nitric acid therefore contains hydrofluoric acid as a corrosion
inhibitor.  IRFNA can be stored for years in metal tanks, leading to storable
bipropellant liquid fueled missles when teamed with a fuel such as one of the
hydrazine series.
     Incidently, monomethyl hydrazine and dimethyl hydrazine are not remarkably
better fuels than straight hydrazine.  The main historical reason that they
were used in missles is that they don't freeze nearly as easily as hydrazine.
This was important to the army, who occasionally has to fight wars at sub zero
temperatures, and the air force who had liquid fueled missles up in the cold
stratosphere.
--
Bruce Dunn   Vancouver, Canada    a752@mindlink.UUCP