Cheap, easy to handle fuels/oxidizers

(Henry Spencer) wrote in message ...
In article ,
The tricky part, really, is the oxidizer. Fuels are generally cheap and
straightforward. There are about four reasonable choices of oxidizer --
LOX, peroxide, N2O, and WFNA -- each with its own set of disadvantages.
LOX and peroxide both require meticulous cleanliness, LOX is cryogenic,
high-grade peroxide is costly and hard to get, N2O requires high pressure,
WFNA is highly corrosive.

If the high pressure of N2O is a pain, is there any reason why people
couldn't use NBP N2O? It's not hugely cryogenic - minus 90C vs
minus 180C for LOX, and with a higher specific heat of vaporization it
should boil off much more slowly.

Or is the general theory that if you're going to go to the hassle of
using moderately cryogenic nitrous that you may as well bite the
bullet and use LOX for the increased performance?

-jake

In article ,
Len wrote:
...There are about four reasonable choices of oxidizer --
LOX, peroxide, N2O, and WFNA -- each with its own set of disadvantages.
LOX and peroxide both require meticulous cleanliness, LOX is cryogenic,
high-grade peroxide is costly and hard to get, N2O requires high pressure,
WFNA is highly corrosive.

If you are talking about a professional project,
cryogenic and cleanliness problems should be
maageable. IMO, the obvious choice is LOX.

It depends a little bit on configuration and mission profile; storability
at room temperature *is* an advantage, and if you work at it :-), you can
make it an important advantage.

That said, as on most things, I generally agree with Len. LOX is a clear
win on performance, and for a professional project its disadvantages are
manageable nuisances unless some unusual consideration intervenes.

For an amateur project, the tradeoffs change somewhat, and careful thought
is called for. Any of those four could be the winner, depending on details.
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |

In article ,
Zoltan Szakaly wrote:
...There are about four reasonable choices of oxidizer --
LOX, peroxide, N2O, and WFNA -- each with its own set of disadvantages...

Don't you mean NTO? As in Nitrogen tetroxide? N2O4

Nope. N2O4 is an unreasonable choice of oxidizer. :-) It is quite costly
and very dangerous. After 40 years of infatuation with it, even NASA and
the USAF are starting to back away from it.

N2O, nitrous oxide, is what I meant.

Its performance is better than you would think based on its small oxygen
content, because it also has quite significant stored energy. In fact, it
would be an interesting monopropellant if a room-temperature catalyst for
it were known.

And it has the great virtue that at room temperature, it is essentially
chemically inert: only when you get it hot does it become an enthusiastic
oxidizer. This is a big win for handling safety, and is why it's used as
the oxidizer in commercial amateur hybrid rockets.

It is in wide use as an anesthetic and as a performance booster for some
types of racing cars, and is not too expensive.

A minor wart is that its density is not all that high. A major wart is
that at room temperature, it has to be kept under fairly high pressure to
be liquid. (The alternative is to chill it, which is a nuisance, although
not nearly as bad a nuisance as LOX.)
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |

In article ,
Jake McGuire wrote:
If the high pressure of N2O is a pain, is there any reason why people
couldn't use NBP N2O? It's not hugely cryogenic - minus 90C vs
minus 180C for LOX, and with a higher specific heat of vaporization it
should boil off much more slowly.

It hasn't often been done, but it is a reasonable notion. That will also
bring the density up noticeably.

Or is the general theory that if you're going to go to the hassle of
using moderately cryogenic nitrous that you may as well bite the
bullet and use LOX for the increased performance?

I suspect that's what most people end up thinking. I'd want a careful
analysis, in the context of a particular project, before deciding that it
was really true.
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |

Jake McGuire wrote

(Henry Spencer) wrote in message
...
In article ,
The tricky part, really, is the oxidizer. Fuels are generally cheap and
straightforward. There are about four reasonable choices of oxidizer --
LOX, peroxide, N2O, and WFNA -- each with its own set of disadvantages.
LOX and peroxide both require meticulous cleanliness, LOX is cryogenic,
high-grade peroxide is costly and hard to get, N2O requires high pressure,
WFNA is highly corrosive.

If the high pressure of N2O is a pain, is there any reason why people
couldn't use NBP N2O? It's not hugely cryogenic - minus 90C vs
minus 180C for LOX, and with a higher specific heat of vaporization it
should boil off much more slowly.

Or is the general theory that if you're going to go to the hassle of
using moderately cryogenic nitrous that you may as well bite the
bullet and use LOX for the increased performance?

Yep. N2O (nitrous oxide, or "laughing gas") isn't that great an oxidiser in
rocket applications, although it's by no means useless. Gives lots of gas,
but it's not energetic enough to give really high exhaust temp's. Good for
cars, but not that good for rockets. Afaik no-one has ever used it in a
space rocket.

It is used in some homebrew/ hobbyist designs though, especially hybrid ones
which use high pressure oxidiser tanks and solid fuel, often perspex. Mostly
they use high pressure tanks for pressure-fed delivery anyway, even the
cryoliquid designs. We are talking homebrew here.

If you want to get some practice in cryoliquid rocketry it might well be a
good (safer, and easier to get and use than lox) way to start. Be careful
not to spill it though, it's not like liquid N2, even a drop will scar.
Clean! Fresh air!! Read lots before you even _think_ of starting!!!



Liquid N2O4 aka NO2 (dinitrogen tetroxide or nitrogen dioxide, same
substance) was fairly widely used as a first stage oxidiser, eg on Titan/
Delta. It's main advantage is that it is storable (and hypergolic with MMH
etc). It doesn't need high pressure, but it has many toxicity, environmental
and regulatory problems, which make it expensive in the US, and it's not
"easy-to-handle" either. If you start pouring it in the open air you will
likely die.

It isn't much used for first stages in the US these days, though it is still
used in first stages by the Russians and Chinese and in some Ariane's, and
it's used by everybody everywhere in lots of upper stages, eg the Shuttle's
RCS and OMS engines to name but two from many.


Of the other oxides of nitrogen, NO (nitric oxide) is cryogenic and
corrosive and toxic and not as good as N2O4, so it's not much use. N2O3
(dinitrogen trioxide) is liquid at -25C and a possible candidate, but N2O4
is better both in performance and temperature stability, though mixtures are
sometimes used (known as MON). N2O5 might just be interesting, but it's a
solid, and not that stable. NO3 is unstable. I can't think of any more
offhand. The peroxides etc are far too dangerous. All nitrogen oxides
(except N2O, which is only mildly toxic) are very toxic.




I don't know of any other liquid oxidisers in use that Henry hasn't
mentioned, save fluorine/ flox, which is ridiculously dangerous and
unfriendly.

Conc. HNO3 is less agressive than WFNA or RFNA, but less powerful and it
doesn't ignite easily or burn well. You could try 90% HNO3/ 10% H2SO4 with
vinyl isobutyl ether fuel (if you can get it) like the German Wasserfall
rocket used, it's hypergolic. And therefore dangerous.

30% (not 30 vol) H2O2 is sometimes available fairly cheaply, but I doubt it
would burn at all. You can distill it at low pressure to concentrate it, but
it's not simple to do.


There are a lot of solid oxidisers, perchlorates (NOT chlorates) are my
personal favourite for performance, after good-ol'-fashioned nitrates, as in
black powder.

There's also a guy in England who traps gaseous oxygen in foamed plastic
fuel at 3000 psi, then uses the hardened foam as a solid monopropellant. I
don't know how good it is as yet, but it might eventually be comparable to
eg lox/kerosene except for the extra chamber weight. Interesting idea
though. I think he's patented it.

--
Peter Fairbrother

Peter Fairbrother wrote:

I don't know of any other liquid oxidisers in use that Henry hasn't
mentioned, save fluorine/ flox, which is ridiculously dangerous and
unfriendly.

There are some exotics, like perchloryl fluoride and nitrogen trifluoride,
but I don't believe they are in use. Chlorine pentafluoride has been
used in upper stages/buses, but it's extremely dangerous.

Paul

(Henry Spencer) wrote in message ...
N2O, nitrous oxide, is what I meant.

Its performance is better than you would think based on its small oxygen
content, because it also has quite significant stored energy.

The combination of Nitrous-Oxide(N2O) and Propane(C3H8) seems
interesting. It seems to have a high ISP. Both self pressurize, and
are relatively safe and easy to handle. At the URL below they say "an
ISP of 230 at sea level, 290 at high elevation". I have not verified
this, but if accurate, that is rather good. Anyone else have ISP
numbers?

http://web.wt.net/~markgoll/rse3.htm

Somewhere I found that propane has a pressure of 124 PSI at 70° F. I
think Nitrous Oxide is about 750 PSI at room temp. Seems like we use
the N20 to cool the engine (since it has extra pressure) and run the
engine with just 124 PSI feeds. Or maybe a simple pump that uses some
of the extra pressure from the N2O to increase the pressure on the
propane.

Not needing separate tanks to pressurize the Nitrous-oxide or Propane
simplifies things a little.

As a guy who thinks the rocket only need to get to about 5 km/sec and
then tethers/ion-drives can do the rest, the N2O/Propane seems like it
has a high enough ISP and would be easier/safer than most
fuels/oxidizers.

But is this ISP of 290 seconds real? Can we get that at 100 PSI?

-- Vince

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~
Vincent Cate Space Tether Enthusiast
http://spacetethers.com/
Anguilla, East Caribbean http://offshore.ai/vince
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~

You have to take life as it happens, but you should try to make it
happen the way you want to take it. - German Proverb

Henry Spencer wrote:

And it has the great virtue that at room temperature, it is
essentially chemically inert: only when you get it hot does it become
an enthusiastic oxidizer.

So if you used it to cool a Chamber that was already running with some
sort of an "Ignition Mixture", could you then pump the stuff in and run
it thru a catalyst?

A minor wart is that its density is not all that high. A major wart
is that at room temperature, it has to be kept under fairly high
pressure to be liquid.

Pressure Fed? (8-)

Aloha mai Nai`a!
--
"Please have your Internet License http://kapu.net/~mjwise/
and Usenet Registration handy..."

Vincent Cate wrote:
(Henry Spencer) wrote:
N2O, nitrous oxide, is what I meant.
Its performance is better than you would think based on its small oxygen
content, because it also has quite significant stored energy.

The combination of Nitrous-Oxide(N2O) and Propane(C3H8) seems
interesting. It seems to have a high ISP. Both self pressurize, and
are relatively safe and easy to handle. At the URL below they say "an
ISP of 230 at sea level, 290 at high elevation". I have not verified
this, but if accurate, that is rather good. Anyone else have ISP
numbers?

It's rather bad by standards of 'good' propellants; upper stage
lox/kero engines can get upwards of 330 S ISP, and hydrazine/tetroxide
can get upwards of 320 S.

I think those numbers are accurate for a higher pressure
motor; for lower pressure motors things are correspondingly worse.

http://web.wt.net/~markgoll/rse3.htm

Somewhere I found that propane has a pressure of 124 PSI at 70° F. I
think Nitrous Oxide is about 750 PSI at room temp.

Get thee to a library (or $$ and Amazon) to a copy of
Matheson's Gas Handbook. Therin are many secrets of the
thermodynamics and gas behaviour world explained clearly
for all to see.

You're not grossly off, but precision is important.
Especially with people who think 1.25 is a fine safety
margin in a pressure vessel 8-P

Seems like we use
the N20 to cool the engine (since it has extra pressure) and run the
engine with just 124 PSI feeds. Or maybe a simple pump that uses some
of the extra pressure from the N2O to increase the pressure on the
propane.

Not needing separate tanks to pressurize the Nitrous-oxide or Propane
simplifies things a little.

As a guy who thinks the rocket only need to get to about 5 km/sec and
then tethers/ion-drives can do the rest, the N2O/Propane seems like it
has a high enough ISP and would be easier/safer than most
fuels/oxidizers.

But is this ISP of 290 seconds real? Can we get that at 100 PSI?

Not at 100 PSI. (and do you mean tank pressure or chamber pressure 8-)

After mid-september I will have some more detailed discussion
in this thread, but it's a bit proprietary right now.


-george william herbert

Peter Fairbrother wrote
Yep. N2O (nitrous oxide, or "laughing gas") isn't that great an oxidiser in
rocket applications, although it's by no means useless. Gives lots of gas,
but it's not energetic enough to give really high exhaust temp's. Good for
cars, but not that good for rockets. Afaik no-one has ever used it in a
space rocket.

Just found out: the Russian Vostoks used "N2O/amine" (I'm not quite sure
what "amine" is though) for retro-rockets, with a claimed ISP of 266 s
(vacuum).


--
Peter Fairbrother