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Subject: RL10 with hot oxidizers (was Re: Space Tech Digest V18 #842)
From: Henry Spencer <> 
Date: Apr 19 1996

In article <v01510111ad920c585f68@[]> (Simon Rowland) writes:
>>>: The RL10 has been fired successfully with liquid fluorine instead of LOX...
> ...The isp for a RL10 with LH2/LOX is ~440, as I understand it. What would
>it change to with 10% O3, 90% O2 as an oxidiser?

I'm afraid you won't like the answer:  it isn't going to improve it much.
People have played with up to 25% ozone, with unimpressive results for all
the troubles and explosions.

(Yes, explosions.  10% or 25% itself is okay... but ozone's boiling point
is considerably higher than oxygen's, so it concentrates as the oxygen
boils off.  When it hits 30%, a 75% phase starts to separate out, and
that is a deadly dangerous explosive.  There are ways to deal with this,
but it all gets to be a lot of trouble for not a lot of gain.)

>  Too bad a fluorine engine wouldn't really be a 'spectator' rocket like
>the Shuttle is :-)  (would you use gold-plated tanks or something?)

Actually, a lot of quite ordinary metals form fluoride surface films when
exposed to fluorine, and this renders them inert to it... provided nothing
melts or scrubs away that thin, fragile surface film.  When something does,
about all you can do is take cover.

By the way, ozone is at least as toxic as fluorine, although it's true
that there won't be much ozone left in the exhaust...
Americans proved to be more bureaucratic           |       Henry Spencer
than I ever thought.  --Valery Ryumin, RKK Energia |

Subject: Re: H2O2/RP1 Rocket Motors
From: (George Herbert)
Date: 24 Jun 1997 14:23:12 -0700

Doug Jones  <> wrote:
>J. Storrs Hall, PhD. wrote:
>> Has anyone thought about using liquid ozone as an oxidizer?
>> It has a higher boiling point than O2 (i.e. not as cold,
>> -112 c vs -183) and higher density (1.6 vs 1.15).  And I
>> would imagine a little bit more kick in the motor, with
>> 32 Kcal/mol free energy.
>> Am I reading that wrong or does that mean almost 600 degrees
>> higher reaction in a stoichiometric combination with H2?
>Oh, gawd, here we go again- I recall a thread a few years ago
>where ozone/acetylene was proposed,

Me, I think, albeit not very seriously.

>then somebody wanted to FLOX it.
>I replied with something like this:
>>Hmmm, nice, we have a toxic, unstable, corrosive, detonable fluourinated
>>oxidizer and an unstable detonable fuel.
>>Is there any way we can make it radioactive?
>Enter one vote against ozone.

Actually, you *can* make it radioactive... O14 and O15 have 70 and
120-ish second half-lives, mass less than normal O16 and therefore
improve Isp, and the best part is that if you make Ozone-14 or -15,
both isotopes will decay into nitrogen, leaving you with NO2 molecules in
an ozone tank, and all reports indicate that NO2 and O3 are hypergolic.

The credit for this particular combination goes to John Schilling,
Frank Crary, and myself during discussions at Space Access 97.
I think that this more or less tops out the potential for
bad propellant choices 8-)

O12 or O13 would be even neater but they have microsecond half-lives.
It's almost conceivable you could work with 70 or 120-sec half lives,
just enough that it would make an amusing J.Propulsion article...
If any of us had spare time, perhaps we could write it up.

-george william herbert
Retro Aerospace

From: (George Herbert)
Subject: Re: H2O2/RP1 Rocket Motors
Date: 24 Jun 1997 16:02:08 -0700

I wrote:
>O12 or O13 would be even neater but they have microsecond half-lives.

I was misreading some notes, there is no O12.  O13 does indeed have
a miniscule half life (8.6 ms or so).


Date: Tue, 14 May 1991 20:37 CDT
From: Bill Higgins-- Beam Jockey <>
Subject:  Doc Clark tells all about ozone (long)
Original_To:  SPACE

In article <> Richard Ristow
(AP430001@BROWNVM.BROWN.EDU) wrote:

>There's been some discussion about alternative propellant chemistry.  Does
>anybody know the current thinking on using ozone as the oxidant? ...

And with admirable economy, Henry Spencer ( but
you knew that) replied:

>As far as I know, nobody has found a way around the fundamental
>problem of coping with a cryogenic liquid that is a powerful and
>touchy explosive.

Despite this, I got the contrary urge to dig up *Ignition* from the
local library and quote big slabs of what Doc Clark had to say about
this.  You may consider this a shameless waste of net bandwidth, but I
insist that it is Good For You to Become Educated.  Here's Doc:

Ozone, O-sub-3, is an allotropic form of oxygen... what makes it
attractive as a propellant is that (1)its liquid density is
considerably higher than that of liquid oxygen, and (2) when a mole of
it decomposes to oxygen during combustion it gives off 34 kilocalories
of energy, which will boost your performance correspondingly.  Saenger
was interested in it in the 30's, and the interest has endured to the
present.  In the face of considerable disillusionment.

For it has its drawbacks.  The least of these is that it's as least as
toxic as fluorine. (People who speak of the invigorating odor of ozone
have never met a real concentration of it!)  Much more important is
the fact that it's unstable-- murderously so.  At the slightest
provocation and sometimes for no apparent reason, it may revert
explosively to oxygen.  And this reversion is catalyzed by water,
chlorine, metal oxides, alkalis-- and by, apparently, certain
substances which have not been identified.  Compared to ozone,
hydrogen peroxide has the sensitivity of a heavyweight wrestler.

Since pure ozone was so lethal, work was concentrated on solutions of
ozone in oxygen, which could be expected to be less dangerous.  The
organizations most involved were the Forrestal Laboratories of
Princeton University, the Armour Research Institute, and the Air
Reduction Co.  Work started in the early 50's, and has continued, on
and off, ever since.

...During 1954-57, the Forrestal fired concentrations of ozone as high
as 25 percent, using ethanol as the fuel.  And they had troubles.

The boiling point of oxygen is 90 K.  That of ozone is 161 K.  On
shutdown, the inside of the oxidizer lines would be wet with the
ozone-oxygen mixture, which would immediately start to evaporate.  The
oxygen, with the lower boiling point, would naturally come off first,
and the solution would become more concentrated in ozone.  And when
that concentration approaches 30 percent, at any temperature below 93
K, a strange thing happens.  The mixture separates into two liquid
phases, one containing 30 percent ozone, the other containing 75
percent.  And as more oxygen boils off, the 30-percent phase
decreases, and the 75-percent phase increases, until you have only one
solution again-- all 75 percent ozone.  And *this* mixture is *really*

So after a series of post-shutdown explosions which were a bit hard on
the plumbing and worse on the nerves of the engineers, some rather
rigorous purging procedures were adopted.  Immediately after shutdown,
the oxidizer lines were flushed with liquid oxygen, or with gaseous
oxygen or nitrogen, to get rid of the residual ozone before it could
cause trouble.

That was some sort of a solution to the problem but not a very
satisfactory one.  25% ozone in oxygen is not so superior to oxygen as
to make its attractions overwhelmingly more important than the
difficulty of handling it. A somewhat superior solution would be to
eliminate the phase separation somehow, and in 1954-55 G.M. Platz...
had some success in attempting to do this.  He showed that the
addition of about 2.8 percent of Freon 13, CClF3, to the mixture would
prevent phase separation at 90 K, although not at 85 K.  Which meant
that if you had, say, a 35-percent mixture at the boiling point of
oxygen, it would remain homogeneous, but if you cooled it to the
boiling point of nitrogen 77 K, the high-concentration, lethal, phase
would separate out. [A bunch of people from Battelle and Air
Reduction] came up with a better answer in 1964-65, when they showed
that 5 percent of OF2 or 9 percent of F2 added to the mixture
completely eliminated the phase separation problem.  And their
addition didn't degrade the performance, as the Freon would have.
Nobody has yet come up with an even faintly plausible explanation for
the solubilizing effect of the additives!

One other ozone mixture has been considered-- that of ozone and
fluorine, which was thoroughly investigated during 1961 by A.J. Gaynor
of Armour.  (30% of ozone would be optimum for RP-1.)  But the
improvement over Flox 70 [a 70% fluorine-30% O2 mixture --WSH]
wouldn't be too impressive, and the thought of what might happen if
the ozone in the oxidizer let go on the launching pad and spread the
fluorine all over tha landscape was somewhat unnerving, and I have
heard of no motor runs with the mixture.

For ozone still explodes.  Some investigators believe that the
explosions are initiated by traces of organic peroxides in the stuff,
which come from traces, say, of oil in the oxygen it was made of.
Other workers are convinced that it's just the nature of ozone to
explode, and still others are sure that original sin has something to
do with it.  So although ozone research has been continuing in a
desultory fashion, there are very few true believers left, who are
still convinced that ozone will somehow, someday, come into its own.
I'm not one of them.

From *Ignition! An Informal History of Liquid Rocket Propellants*, by
John D. Clark, Rutgers University Press, 1972.  Quoted without
permission.  But if Rutgers really *cared* about their copyright
they'd *keep it in print*, wouldn't they, and then I could BUY A COPY
OF THE DAMNED BOOK!  (bitter? no, not me, I'm not bitter.)  I've
gotten nowhere in finding copies for sale.  Fortunately a few nearby
libraries have it.  Public libraries are among God's finest blessings
upon this planet... But don't get me started.  Next time you're at a
party, you can work the topic around to ozone as a rocket propellant,
and dazzle everyone with your expertise, making new friends and
attracting members of the opposite sex.  Thank a public library for

     O~~*           /_) ' / /   /_/ '  ,   ,  ' ,_  _           \|/
   - ~ -~~~~~~~~~~~/_) / / /   / / / (_) (_) / / / _\~~~~~~~~~~~zap!
 /       \                          (_) (_)                    / | \
 |       |                      Bill Higgins
 \       /                      Fermi National Accelerator Laboratory
   -   -                        Bitnet:                HIGGINS@FNALB.BITNET
     ~                          Internet:             HIGGINS@FNAL.FNAL.GOV
                                SPAN/Hepnet/Physnet:         43011::HIGGINS

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