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From: Henry Spencer <>
Subject: Re: Fluorinated oxidizers
Date: Thu, 4 Jul 1996 14:12:48 GMT

In article <4ranma$> (Frank Scrooby) writes:
>> >Well, according to John Clark's book "Ignition", ClF3 is hypergolic with
>> >human flesh!  
>> I wonder how they found this out? Empirically, as in by accident?
>Wasn't this the same stuff used in the Me-153 Komet a rocket powered plane used
>by the German Luftwaffe in the last years of WW2?

You're thinking of the Me-163, and it did not use ClF3.  Skipping some 
details, it used hydrazine and hydrogen peroxide, and the hydrazine was
what caused problems.

As for the ClF3, I would suspect either small-scale accidents or just a
simple application of chemistry. :-)
If we feared danger, mankind would never           |       Henry Spencer
go to space.                  --Ellison S. Onizuka |

From: Henry Spencer <>
Subject: Re: Unadvisable Rocket Science
Date: Wed, 31 Jul 1996 19:20:47 GMT

In article <4tl4r3$> "Geoffrey A. Landis" <> writes:
>>>> rocket powered motorcycle.  I am looking for something really really
>>>> dangerous to use as an oxidiser for this engine.  Extra points will be
>>>> awarded if this oxidiser is toxic.  
>>>...pure flourine...
>>  100% Ozone...
>Ozone and fluorine will require that your motorcycle have cryo tanks...
>For toxic I'd go for either red fuming nitric acid or nitrogen tetroxide

Oh come now Geoff -- we can do better than that.  Chlorine pentafluoride,
ClF5, is a great deal more corrosive than fluorine (because it's denser
than gaseous fluorine and warmer than liquid fluorine), is a liquid at
room temperature under a bit of pressure, and is highly toxic to boot. 
For sheer nastiness, it's hard to beat a compound that is hypergolic with
most fire-extinguishing agents, which ClF5 is.

ClF5 has *almost* flown as a rocket oxidizer several times, most recently
in some of the Clementine 2 proposals.  SDIO has developed and tested a
hydrazine/ClF5 maneuvering engine.  If you want maximum performance, it
is actually quite attractive:  it's dense, energetic, and non-cryogenic.
You gain about 50s of Isp over N2O4, and ClF5 is denser too.

>If you want something a bit dangerous, hydrogen peroxide. 

This is basically mythology.  Hydrogen peroxide is easily the *least*
dangerous of the useful oxidizers -- considerably less hazardous than
liquid oxygen.
 ...the truly fundamental discoveries seldom       |       Henry Spencer
occur where we have decided to look.  --B. Forman  |

From: Henry Spencer <>
Subject: Re: Unadvisable Rocket Science
Date: Thu, 1 Aug 1996 16:16:00 GMT

In article <4tg0ua$> (Robert Hill) writes:
>...I seem to remember such a substance as 
>red fuming mercruy fulminate.  However I am almost certian that such a 
>substance does not exist( although it sure sounds dangerous and toxic!). 

You're probably misremembering RFNA (red fuming nitric acid), nitric acid
with NO2 dissolved in it.  It's moderately nasty.  However, as per my
earlier posting, ClF5 is a real rocket oxidizer which makes RFNA look
like tapwater.  Teflon will burn in ClF5.  So will asbestos.

>I assume gasoline will work as a fuel, it's just more dagerous than the 
>various forms of kerosene commonly used.

If you want the combination to be really nasty, forget the gasoline and
switch to hydrazine (N2H4).  It is volatile, flammable, highly poisonous,
prone to spontaneous decomposition, explosive when pressurized, corrosive,
and carcinogenic.  Furthermore, it is a good fuel for use with ClF5, which
performs poorly with fuels that contain carbon.
 ...the truly fundamental discoveries seldom       |       Henry Spencer
occur where we have decided to look.  --B. Forman  |

Subject: Re: Fuel-Rich rockets (was Re: Saturn V)
From: Henry Spencer <>
Date: Sat, 28 Jun 1997 15:53:50 GMT

In article <>,
JAllenLewi <> wrote:
>...the density impulse is not discussed often enough.  When you look at
>density impulse, NTO/Aerozine 50 type combinations like on the Titan core,
>et al., are very attractive...

And you can do still better if you replace the N2O4 with ClF5 (and throw
in a bit of FClO3 if you want to go on using 50-50 N2H4/UDMH, so there's
some oxygen in there to burn the carbon) -- it's denser and more energetic,
although harder to handle.

BUT... I would actually say that the desirability of N2O4/hydrazine is
another piece of entrenched mythology.  It's an excellent combination for
tactical missiles, where storability is vital.  For launchers, one need
not be afraid of cryogenics or peroxide, so LOX/kerosene or H2O2/kerosene
is a much better choice:  far safer, comparable or better performance, and
much cheaper.
Committees do harm merely by existing.             |       Henry Spencer
                           -- Freeman Dyson        |

From: Henry Spencer <>
Subject: Re: Zero-g fuel tanks: idea
Date: Tue, 7 Oct 1997 20:25:40 GMT

In article <>,
RBynum3965 <> wrote:
>Why not just use an inflatable bladder in the tank?

Several potential problems, but the big one is that it's difficult to find
bladder materials that are compatible with the liquids involved.  Very few
elastic materials stay elastic at cryogenic temperatures, for one thing.
For another, it can be hard to find even slightly-flexible materials that
can stand up to a powerful oxidizer -- for the most powerful oxidizers,
there simply aren't any.  (Not even Teflon is stable in ClF5.)
If NT is the answer, you didn't                 |     Henry Spencer
understand the question.  -- Peter Blake        |

From: (Henry Spencer)
Subject: Re: Trains in space?
Date: Tue, 30 Jun 1998 04:35:02 GMT

In article <>,
Greg D. Moore (Strider) <> wrote:
>> Sand is hypergolic with ClF5.  The recommended procedure for dealing with
>> a ClF5 fire is to take cover at a safe distance, and wait until it burns
>> itself out.
>> ...a storable oxidizer with considerably better performance than N2O4.
>Ah, what do you store this in?

Same thing you store fluorine in:  metal tanks.  Just like fluorine, it
instantly forms a fluoride layer on the metal surface, and that protects
the rest of the metal from attack.  Provided you pick the right metal, and
prepare it properly.  Provided it is spotlessly clean.  Provided that you
don't do anything that would scrub or melt the fluoride layer off.  The
stuff is spectacularly intolerant of even the smallest mistakes.

>And it would really suck if you got a leak along the way.

Yes indeedy.
Being the last man on the Moon is a |  Henry Spencer
very dubious honor. -- Gene Cernan  |      (aka

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