Recommended TSTO technical papers?

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WvB - 26 Aug 2003 06:12 GMT

What are the best technical papers to read that deal with TSTO launch
vehicle studies? I'd like to survey the best thinking that's been put
into the topic.

I'm also curious about simple hydrocarbon fuels like propane/methane and
their relative merits. For one thing: does propane soot if used in a
fuel-rich preburner? I've heard methane works fine in FRSC.

Last I heard, there were people like Henry Spencer advocating LOX/Propane,
for SSTO if I remember. Would LOX/Propane still be the way to go for
TSTO, or would another propellant choice be better?

Do the ground infrastructure issues outweigh the advantages of using two
fuels for a TSTO, i.e. propane/hydrogen rather than propane/propane.

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Ian Stirling - 26 Aug 2003 18:13 GMT

> What are the best technical papers to read that deal with TSTO launch
> vehicle studies? I'd like to survey the best thinking that's been put
[quoted text clipped - 7 lines]
> for SSTO if I remember. Would LOX/Propane still be the way to go for
> TSTO, or would another propellant choice be better?

For TSTO, it's a bit easier than SSTO.
The second stage can live with less dense fuels, as it has no need to fly
through significant atmosphere, and overall strucutral fraction can be a tad
higher.

All the same arguments apply for fuels as do to SSTO, but less so, though there
is the added issue of if you want to use common fuels or not.
TSTO is just plain easier, and will probably work whether you chose all
LOX/LH2, or go for something like H2O2/kerosene for stage 1 and LH2/LOX for
stage 2.

You may well end up looking at a very stubby stage 2, of similar diameter
as stage 1, so there is almost no drag penalty, which is a significant
driver for going to LOX/propane, or other 'dense' fuels for the bottom
stage.

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Peter Fairbrother - 27 Aug 2003 20:56 GMT

> TSTO is just plain easier, and will probably work whether you chose all
> LOX/LH2, or go for something like H2O2/kerosene for stage 1 and LH2/LOX for
> stage 2.

Kerosene is safer and easier to use than propane, but you'd get a slightly
better isp with propane or even ethane, methane or lng. I don't know if
that's enough to make them better overall than kerosene though.

Where ground support is available and there are no special storage
requirements, lox is probably the only sensible choice of oxidiser,
especially if you are doing lots of launches. It's by far the cheapest, it
gives good isp, it's non-toxic, and it's reasonably safe as long as you keep
things clean.

It's only disadvantage is that you are at the edge of the possible,
especially for reusable engines. It's pretty harsh as far as long engine
life and switch-on-and-off-ability goes. For reuseability, you might want to
look at something slightly gentler.

H2O2 is a no-no for reuseables. Forms unstable explosive peroxides which
accumulate in nasty places. There isn't a real aircraft or spacecraft
anywhere that doesn't have minor leaks.

N2O4 is also a no-no, for environmental and cost reasons. IRFNA is similar,
and IWFNA is still pretty bad. N2O is a bad greenhouse gas and gives lower
isp.

Me? I'd stick to lox, and work on the engineering.

> You may well end up looking at a very stubby stage 2, of similar diameter
> as stage 1, so there is almost no drag penalty, which is a significant
> driver for going to LOX/propane, or other 'dense' fuels for the bottom
> stage.

The Skylab 1 Saturn V 2 was stubby like that. It used two stages,
lox/kerosene and lox/LH2. It put 75 tons into LEO for a launch weight of
around 2,500 tons - 5% payload, not bad for the '70s, and considering it
wasn't designed for that.

I really liked the Saturn V, "the rocket that never failed".

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Peter Fairbrother

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Paul F. Dietz - 27 Aug 2003 21:58 GMT

> Kerosene is safer and easier to use than propane,

Propane has the substantial advantage of being easier to purge
from the system. This is important since a little bit of hydrocarbon
left in the LOX plumbing can be catastrophic.

Paul

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John Carmack - 28 Aug 2003 04:31 GMT

> H2O2 is a no-no for reuseables. Forms unstable explosive peroxides which
> accumulate in nasty places. There isn't a real aircraft or spacecraft
> anywhere that doesn't have minor leaks.

What do you base this on? Peroxide has more extensive use in reusable
engines than any other rocket propellant. All the rocket belts,
rocket dragsters, rocket helicopters, as well as a commercial reusable
RATO in England all were long service life peroxide engines. True,
they were all monoprop, but that does exonerate the oxidizer.

Leaked high concentration peroxide doesn't hang around very long.
Practically anything it leaks onto will cause it to start decomposing,
not forming explosive peroxides. Only if you made the incredibly bad
system design choice to use high concentration peroxide and alcohol in
a biprop system would this be a credible danger -- simultanious leaks
from both tanks could indeed combine to form a detonable mixture.
With kerosene and most other hydrocarbons, they aren't miscable. Lox
can also form explosive mixtures with quite a few fuels, like propane.
Peroxide leaks onto random surfaces may well be a fire hazard, but
the same can be said for any oxidizer (except nitrous oxide).

Higher cost and somewhat lower performance are valid reasons not to
use peroxide, but "Forms unstable explosive peroxides" really isn't.

Lots of people have negative things to say about peroxide that are
mostly extrapolations from historic folklore, but most of these people
(assuming they aren't strictly armchair engineers) have had much more
direct experience with, say, frozen lox valves...

John Carmack
www.armadilloaerospace.com

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Peter Fairbrother - 28 Aug 2003 19:30 GMT

>> H2O2 is a no-no for reuseables. Forms unstable explosive peroxides which
>> accumulate in nasty places. There isn't a real aircraft or spacecraft
>> anywhere that doesn't have minor leaks.
>
> What do you base this on?

Science, accident reports and experience.

A bit of chemistry (I'm still an amateur, but not armchair, rocket-ist but I
was a professional chemist before I became a mathematian/cryptographer).

Caveat: this is not professional opinion, it should be considered as just
general chatter. Peroxides are not my speciality. Don't rely on it for
safety.

1) Inorganic peroxides. I'm sure you use high purity aluminium for your
peroxide tanks, but Al/Mg alloys are better from a weight point of view for
the rest of the structure, and Al/Mg will form both straight magnesium
peroxides and mixed magnesium/aluminium peroxides.

I've even heard of Al peroxides. I theorise that the oxide layer on the Al
is what protects it, and it will form a peroxide under some circumstances,
like perhaps leaks.

Cu, Zn, Ni, brass and bronze will all form peroxides, and there are many
other mixed inorganic peroxides, including some Fe ones. Yes those metals
decompose the H2O2, but they _also_ form peroxides. These can be highly
reactive or explosive by themselves, and likely will be explosive if they
come into contact with organic materials.

2) Many salts will form addition compounds with H2O2, a bit like the
hydrates. I don't know offhand which ones do, but it's probably broadly
similar to the hydrates. Washing soda is an example, off the top of my head.
They can decompose violently, perhaps explosively, just by themselves, and
are likely to react explosively if in contact with organics.

3) Organic peroxides. It is well known that ethers, acetals and alcohols
will form organic peroxides with hydrogen peroxide, but so will almost any
organic with an oxygen atom in it, and even aliphatic hydrocarbons will do
so eventually in leak conditions with air and metals present to act as
catalysts. Many organic peroxides are sensitive explosives.

BTW, alcohol is pretty bad here. It can oxidise in air (or slowly with H2O2)
to acetaldehyde or acetic acid, when it will form really nasty peroxides
with H2O2. Are you the guy who uses 50% aqueous H2O2 with small amounts of
added alcohol? Beware. That's a bad combination to leave around.

Nobody knows that much about any of these, they tend to be too dangerous to
experiment on. There are probably unknown dangers involving mixed peroxides
too. Chemists don't like working with them.

There are many reports of not-quite-fully-explained accidents and explosions
relating to the previous storage and use of H2O2. Things like shelves
exploding when disassembled. Even a water-filled drainage pond (!).

> Peroxide has more extensive use in reusable
> engines than any other rocket propellant. All the rocket belts,
> rocket dragsters, rocket helicopters, as well as a commercial reusable
> RATO in England all were long service life peroxide engines. True,
> they were all monoprop, but that does exonerate the oxidizer.

"Were" is probably the operative word here. The Royal Navy won't use it in
it's torpedoes. The US navy has stopped using it. Even the Russians have
withdrawn their peroxide torpedoes after the Kursk explosion.

Whether that's because of peroxides building up from leaks or the "normal"
dnagers of H2O2 I don't know. But I'd have to have a powerful reason, and do
lots of research, before I used it in a reuseable (torpedoes are frequently
test fired and reused).

> Leaked high concentration peroxide doesn't hang around very long.
> Practically anything it leaks onto will cause it to start decomposing,
> not forming explosive peroxides.

There may well be peroxides forming while it's decomposing. Slow leaks are
bad for that. The peroxides build up until..

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Peter Fairbrother

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Earl Colby Pottinger - 31 Aug 2003 07:21 GMT

Peter Fairbrother <zenadsl6186@zen.co.uk> :

> John Carmack wrote
>
[quoted text clipped - 14 lines]
> general chatter. Peroxides are not my speciality. Don't rely on it for
> safety.

Thank you for the above.

> 1) Inorganic peroxides. I'm sure you use high purity aluminium for your
> peroxide tanks, but Al/Mg alloys are better from a weight point of view for
> the rest of the structure, and Al/Mg will form both straight magnesium
> peroxides and mixed magnesium/aluminium peroxides.

Well, just don't act like NASA then, if Al/Mg is not safe don't use it? Not
everyone thinks like NASA and believe that a rocket must run at the ragged
edge of techonolgy and be made as light as possible. Some people want rugged
rockets that are reliable and can be used over and over again. I don't know
about John Carmack, but personally all my work is done with Glass/Stainless
Steel/Aluminium only. I never planned to use Al/Mg in any of my designs nor
have I heard that anyone else is, so why assume that they will?

> I've even heard of Al peroxides. I theorise that the oxide layer on the Al
> is what protects it, and it will form a peroxide under some circumstances,
> like perhaps leaks.

Can you supply a URL or reference? Not one report that I have read about
storing peroxide in aluminium tanks warns of peroxides forming from the
metal, and the Russians stored peroxide for years in thier tanks without
problems. And the USA peroxide suppliers who are anal about safe storage
have not mentioned it either.

> Cu, Zn, Ni, brass and bronze will all form peroxides, and there are many
> other mixed inorganic peroxides, including some Fe ones. Yes those metals
> decompose the H2O2, but they _also_ form peroxides. These can be highly
> reactive or explosive by themselves, and likely will be explosive if they
> come into contact with organic materials.

This requires that you follow just one simple rule. Don't use these
materials! What is so hard about that idea? Again this is not NASA where
safety regulations are bypassed with goverment mandate. I already knew all
the above materials and more are problems so I just don't use them. I know
this must be hard to understand, but aluminium can be machined to make any
object these other material can.

> 2) Many salts will form addition compounds with H2O2, a bit like the
> hydrates. I don't know offhand which ones do, but it's probably broadly
> similar to the hydrates. Washing soda is an example, off the top of my head.
> They can decompose violently, perhaps explosively, just by themselves, and
> are likely to react explosively if in contact with organics.

And that is why I don't add anything to my peroxide. Infact most of my
personal research is in finding cheap ways to make peroxide more pure. Why
are you assuming that people don't know to keep thier peroxide tanks clean?

> 3) Organic peroxides. It is well known that ethers, acetals and alcohols
> will form organic peroxides with hydrogen peroxide, but so will almost any
> organic with an oxygen atom in it, and even aliphatic hydrocarbons will do
> so eventually in leak conditions with air and metals present to act as
> catalysts. Many organic peroxides are sensitive explosives.

Again, I know it is a hard thing to see, but don't use organics in your
design, why assume that they must? Can you show where John Carmack used any?
ERPS? RocketGuy? Any rocket cars even? My site in the rocket section?
Everyone who has done this for any time already knows this and the solution
was simple - Don't use them!

> BTW, alcohol is pretty bad here. It can oxidise in air (or slowly with H2O2)
> to acetaldehyde or acetic acid, when it will form really nasty peroxides
> with H2O2. Are you the guy who uses 50% aqueous H2O2 with small amounts of
> added alcohol? Beware. That's a bad combination to leave around.

I assume you mean John Carmack and if you read his website you would see that
it is stated procedure to only mix just before use, and to always burn off
all the mixture - Each and Every Time. There is no mix left lying around.
Sometimes the simple solutions are the best ones.

> Nobody knows that much about any of these, they tend to be too dangerous to
> experiment on. There are probably unknown dangers involving mixed peroxides
> too. Chemists don't like working with them.

Well then the only way to find out the truth is to do some experiments.
Based on chemist safety standards no non-hybrid rocket would ever be built,
all the useful combinations have the potential being a major explosive. So
if the dangers are unknown your advice is not to find out what the dangers
are but to quit?

> There are many reports of not-quite-fully-explained accidents and explosions
> relating to the previous storage and use of H2O2. Things like shelves
> exploding when disassembled. Even a water-filled drainage pond (!).

Yes, and how many of them involved peroxide that was stored away and
forgotten for years? Most rocket people plan to burn off thier peroxide
within days of recieving it. Others use very cold storage or very remote
storage to be safe. You are talking about stuff left in the back of the
store or in a standard warehouse. And as for the water filled pond you need
to supply some references on that one, the only way I see it working is if
there was explosive peroxides forming and the pond was never drained. Again
suggest peroxide just left lying around for long periods of time.

> > Peroxide has more extensive use in reusable
> > engines than any other rocket propellant. All the rocket belts,
[quoted text clipped - 5 lines]
> it's torpedoes. The US navy has stopped using it. Even the Russians have
> withdrawn their peroxide torpedoes after the Kursk explosion.

The point is while they found what they think are better combinations to fuel
things, your claims are on the dangers of peroxide. But peroxide was in use
in all these machines and still is in the case of rocket belts and rocket
cars. There are even a few rocket helcopters still being made. But if
peroxide is as dangerous as you say, where are all the explosions? You can
point to the Kursk but where are the explosions of peroxide powered machines
that were just sitting there. Maybe the fact that with use the peroxide does
not just sit there and accumulate explosive peroxides has something to do
with it.

> Whether that's because of peroxides building up from leaks or the "normal"
> dnagers of H2O2 I don't know. But I'd have to have a powerful reason, and do
> lots of research, before I used it in a reuseable (torpedoes are frequently
> test fired and reused).

Yes, but you are also talking about the Russian navy when it is suffering
it's worse cutbacks. Again, where others were regularly using peroxide to
power thier machines where are the explosions. And the German Comet does not
count, there is a big difference in how you handle peroxide while people are
trying to kill you first.

> > Leaked high concentration peroxide doesn't hang around very long.
> > Practically anything it leaks onto will cause it to start decomposing,
> > not forming explosive peroxides.

> There may well be peroxides forming while it's decomposing. Slow leaks are
> bad for that. The peroxides build up until..

And there must be leaks because? Again this is not NASA, every present day
peroxide design that I know of has plumbing simple enough to be completely
insepected by one person in a single day. Just because something can be
complicated does not mean that it must be.

A little fear to keep you on your toes is a good thing, a lot of fear that
leaves you frozen still is just a waste.

Earl Colby Pottinger

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Charles Buckley - 31 Aug 2003 14:47 GMT

>>H2O2 is a no-no for reuseables. Forms unstable explosive peroxides which
>>accumulate in nasty places. There isn't a real aircraft or spacecraft
[quoted text clipped - 27 lines]
> John Carmack
> www.armadilloaerospace.com

John,

What was the source down in Mexico for the H2O2 distillation unit?

Charles Buckley

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ed kyle - 28 Aug 2003 05:04 GMT

> I really liked the Saturn V, "the rocket that never failed".

Except that it did fail once. SA-502 failed to perform its
assigned mission when its S-IVB J-2 engine failed to restart,
leaving the rocket's Apollo 6 payload far short of its intended
orbit (360 km apogee vs. planned 528,024 km apogee, or a
velocity shortfall of nearly 26% (about 2,728 meters per
second). Today's media would howl "failure" after such a
performance.

- Ed Kyle

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Space Forum / Space Flight / August 2003

Recommended TSTO technical papers?