Newsgroups: sci.space.history
From: Henry Spencer <henry@zoo.toronto.edu>
Subject: Re: What's Aerozene 50?
Date: Thu, 4 Sep 1997 16:39:08 GMT

In article <5ul796$4cl@bgtnsc02.worldnet.att.net>,
Larks  <"Larks@worldnet.att.net"@worldnet.att.net> wrote:
>What is the tradename, "Aerozene 50" or "Aerozine 50".  I have seen
>it in print as the former only.  I have an engineering drawing of the
>LEM with "Aerozene 50" tanks indicated while the consensus in this
>group is that it is the latter "Aerozine 50".  Also, I have a LIFE
>magazine pictorial cutaway of the LEM stating "Aerozene".

I don't think I've ever seen it spelled Aerozene.  Several sources,
including "Apollo Expeditions to the Moon", the Apollo News Reference, and
Clark's book on liquid propellants, all spell it Aerozine.

>Also, not terribly related, just for my information:
>are all of the above four compounds I mentioned hypergolic
>with N2O4 ?  I would assume all are, but I was just wondering.

Yes, they are.

There actually were a lot of hydrazine-based fuels in use at one point:
various mixtures of hydrazine (excellent fuel, but high freezing point and
useless for cooling), monomethyl hydrazine (MMH, much better freezing
point), unsymmetrical dimethyl hydrazine (UDMH, even better freezing point
and stable enough for regenerative cooling), diethylene triamine (DETA,
makes the mixture denser), acetonitrile (reduces the viscosity of DETA
mixtures), hydrazine nitrate (helps freezing point and boosts performance,
but dangerous and troublesome in large amounts), and even water (hurts
performance but improves stability and cooling).

Most of these have quietly passed out of use, especially since the missile
people -- who were the ones who really cared about freezing point -- have
almost all switched to solid fuels.  The major survivors have been the
pure compounds plus 50-50 (aka Aerozine 50 etc.), with hydrazine and MMH
used as spacecraft propellants and UDMH and 50-50 used in larger
applications.  Hydrazine has the best performance (and is also useful as a
monopropellant), MMH is more stable and gives the highest performance when
freezing point is an issue (Galileo uses MMH), UDMH is still more stable
and is usable in big regeneratively-cooled engines, and 50-50 is almost as
stable as UDMH and performs better.
--
The operating systems of the 1950s will be out  |     Henry Spencer
next year from Microsoft.  -- Mark Weiser       | henry@zoo.toronto.edu

Newsgroups: sci.space.tech
From: henry@spsystems.net (Henry Spencer)
Subject: Re: LH2 coolant for SRB or F-1 rocket nozzels
Date: Tue, 23 May 2000 03:39:31 GMT

In article <8gckpu$1r8@chronicle.concentric.net>,
Hiram Berry <burningb@burningbridges.com> wrote:
>...but it's interesting that the other monopropellant coolant
>mentioned in this thread, hydrazine, was a major component of the other fuel
>used, "C-stoff", and that the C-stoff cooled version successfully test fired
>as well.

Hmm, I'm not sure about the beginning, but by the end, hydrazine was
getting to be a fairly minor component of C-stoff.  They'd have preferred
to use more of it, but supplies were limited.

>If you want to use a monoprop to power pumps, though, consider using
>hydrazine (or MMH) instead of peroxide in this role.  Its adiabatic
>decomposition temperature is about 350C lower, its products are reducing
>rather than oxidizing (allowing the engine which powers the pumps to be made
>from common materials, or even possibly be an off the shelf unit), and the
>enthalpy per unit mass decomposed is a little higher.

And you don't care that it's flammable, volatile, corrosive, prone to
spontaneous decomposition and/or ignition, potentially explosive,
intensely poisonous by inhalation or skin contact, and carcinogenic?
Peroxide is mother's milk by comparison.  Hydrazine may perform a bit
better, but...
--
Microsoft shouldn't be broken up.       |  Henry Spencer   henry@spsystems.net
It should be shut down.  -- Phil Agre   |      (aka henry@zoo.toronto.edu)

Newsgroups: sci.space.tech
From: henry@spsystems.net (Henry Spencer)
Subject: Re: Hydrazine & N2O4
Date: Sat, 4 Nov 2000 16:08:14 GMT

In article <8tubq2$4vc$1@nnrp1.deja.com>,  <cray74@hotmail.com> wrote:
>I noticed that N2O4 & UDMH are self-igniting (hypergolic?)
>on Mark Wade's Space Library, but are N2O4 & Hydrazine*
>hypergolic?

Yes.  N2O4 is hypergolic with any of the hydrazine family -- hydrazine
itself, MMH, UDMH, and mixtures thereof.

>*If I read the entries right, N2H4 is chemically similar
>to UDMH.

Correct -- UDMH is Unsymmetrical DiMethyl Hydrazine, hydrazine with a
couple of methyl groups added, a fairly minor modification of hydrazine
which makes it more stable.  (In particular, hydrazine cannot be used for
regenerative cooling of engines, but UDMH and UDMH-hydrazine mixtures will
work for that.  "50-50", half hydrazine and half UDMH, is a common choice
of fuel for big hypergolic engines for that reason.)

>It also benefits from being a functional monopropellent,
>which I don't think UDMH is.

UDMH could be used as a monopropellant in principle, I believe, but there
are practical problems, and hydrazine is the only one of the family which
is usually taken seriously for that role.  (It has the best performance too.)

>What are the typical combustion products of N2O4 & Hydrazine?
>I got:
>N2O4 + 2 N2H4 --> 3 N2 + 4 H2O

You'd also get some H2 and NH3, because it is usually beneficial to run
bipropellant engines a bit fuel-rich, for several reasons.

>Given the combustion temperatures, I'd expect some funky
>secondary reactions resulting in nitric acid, nitrous
>oxides, etc...

Those are all aggressive oxidizing species and won't survive well in a
fuel-rich environment.  You might get traces of them, but that's all.

>I'm curious if the exhaust* is worth capturing
>and filtering for water and nitrogen supplies on a space station.

Space stations generally run a water surplus, because human metabolism
produces water as a byproduct of burning food.  (In fact, it is common to
get breathing oxygen by electrolyzing some of the extra water, avoiding
the need to ship oxygen up.)  There's no need to supply much water.

If you want nitrogen, just decomposing hydrazine (no N2O4 involved) is a
fairly reasonable way to get it; this has been mentioned as a way to store
nitrogen conveniently for stations.  The only real issue, apart from the
heat generated, is that you must be absolutely sure there is *no* leftover
hydrazine in the output stream, because hydrazine is highly poisonous, and
carcinogenic to boot.
--
Microsoft shouldn't be broken up.       |  Henry Spencer   henry@spsystems.net
It should be shut down.  -- Phil Agre   |      (aka henry@zoo.toronto.edu)

From: Doug Jones <random@qnet.com>
Newsgroups: sci.space.tech
Subject: Re: Hydrazine & N2O4
Date: Sat, 04 Nov 2000 09:24:18 -0800

cray74@hotmail.com wrote:
>
> I noticed that N2O4 & UDMH are self-igniting (hypergolic?)
> on Mark Wade's Space Library, but are N2O4 & Hydrazine*
> hypergolic?

Yes, and in some comsats the apogee kick motor runs on these, while the
RCS uses the hydrazine as a monoprop. Thus they get good Isp for the
circularization burn along with a big monoprop tank.

> *If I read the entries right, N2H4 is chemically similar
> to UDMH. It also benefits from being a functional monopropellent,
> which I don't think UDMH is.

Yep, see above.

> What are the typical combustion products of N2O4 & Hydrazine?
> I got:
>
> N2O4 + 2 N2H4 --> 3 N2 + 4 H2O
>
> Given the combustion temperatures, I'd expect some funky
> secondary reactions resulting in nitric acid, nitrous
> oxides, etc. I'm curious if the exhaust* is worth capturing
> and filtering for water and nitrogen supplies on a space
> station.

In rocket engines, you always run rich, which gives excess hydrogen (and
CO in carbon containing systems).  This lowers the molecular weight of
the exhaust and gives better nozzle performance, improving Isp.  The
output below is from a typical equilibrium calculator, and shows how the
combustion products often have small amounts of higher energy species.
The program was balking at doing frozen flow calculations (where you
assume that the composition doesn't change after the throat due to the
short time available for reactions) so the fraction of H2 in the exhaust
is underreported.  Look at the throat column to get the real exhaust
composition.  Note that about 1% atomic hydrogen exists at the same time
as a fraction of a percent of O2, unlikely though that may seem.

There have been proposals to carry hydrazine and decompose it to supply
makeup nitrogen for breathing gas on long duration missions, while the
hydrogen is reacted in a fuel cell with oxygen to create drinking water
and useful power. The system complexity gets out of hand, though.


              THEORETICAL ROCKET PERFORMANCE ASSUMING EQUILIBRIUM

            COMPOSITION DURING EXPANSION FROM FINITE AREA COMBUSTOR

 Pinj =   250.0 PSIA
 Ac/At =  4.0000      Pinj/Pinf =  1.012755
 CASE = 1

             REACTANT                    WT FRACTION      ENERGY
TEMP
                                          (SEE NOTE)     KJ/KG-MOL
K
 FUEL        N2H4(L)                      1.0000000     50380.000
298.150
 OXIDANT     N2O4(L)                      1.0000000    -17549.000
298.150

 REACTANT DENSITY= 1048.13 KG/CU M

 O/F=    1.30000  %FUEL= 43.478261  R,EQ.RATIO= 1.104341  PHI,EQ.RATIO=
1.104341

                 INJECTOR  COMB END  THROAT     EXIT
 Pinj/P            1.0000   1.0260   1.7592   709.38
 P, BAR            17.237   16.800   9.7979   .02430
 T, K             3134.45  3129.10  2956.89  1055.90
 RHO, KG/CU M    1.3569 0 1.3250 0 8.2648-1 5.9081-3
 H, KJ/KG          575.74   559.26  -101.98 -4729.32
 U, KJ/KG         -694.53  -708.63 -1287.48 -5140.60
 G, KJ/KG        -38654.5 -38620.2 -37125.2 -17950.3
 S, KJ/(KG)(K)    12.5158  12.5210  12.5210  12.5210

 M, (1/n)          20.516   20.520   20.738   21.346
 (dLV/dLP)t      -1.01896 -1.01890 -1.01443 -1.00000
 (dLV/dLT)p        1.3821   1.3815   1.3092   1.0000
 Cp, KJ/(KG)(K)    5.4073   5.4061   4.9153   1.7608
 GAMMAs            1.1418   1.1418   1.1434   1.2840
 SON VEL,M/SEC     1204.3   1203.2   1164.2    726.7
 MACH NUMBER         .000     .151    1.000    4.482

 TRANSPORT PROPERTIES (GASES ONLY)
   CONDUCTIVITY IN UNITS OF MILLIWATTS/(CM)(K)

 VISC,MILLIPOISE   1.0612   1.0599   1.0155   .49899

  WITH EQUILIBRIUM REACTIONS

 Cp, KJ/(KG)(K)    5.4073   5.4061   4.9153   1.7608
 CONDUCTIVITY     14.0234  14.0020  11.7341   1.4777
 PRANDTL NUMBER     .4092    .4092    .4254    .5946

  WITH FROZEN REACTIONS

 Cp, KJ/(KG)(K)    2.2340   2.2336   2.2167   1.7608
 CONDUCTIVITY      4.2862   4.2785   3.9841   1.4776
 PRANDTL NUMBER     .5531    .5533    .5650    .5946

 PERFORMANCE PARAMETERS

 Ae/At                      4.0000   1.0000   50.000
 CSTAR, M/SEC               1768.8   1768.8   1768.8
 CF                          .1026    .6582   1.8415
 Ivac, M/SEC                7165.5   2182.5   3383.6
 Isp, M/SEC                  181.5   1164.2   3257.3


 MOLE FRACTIONS

 *H                .01660   .01655   .01230   .00000
 HO2               .00002   .00002   .00001   .00000
 *H2               .08609   .08595   .07754   .05473
 H2O               .44657   .44690   .46718   .52452
 *NO               .00749   .00744   .00527   .00000
 *N2               .40064   .40073   .40612   .42075
 *O                .00365   .00364   .00231   .00000
 *OH               .03148   .03134   .02372   .00000
 *O2               .00743   .00742   .00553   .00000


--
Doug Jones
Rocket Plumber, XCOR Aerospace
http://www.xcor-aerospace.com