From: henry@zoo.toronto.edu (Henry Spencer)
Newsgroups: sci.space.tech
Subject: Re: Liquid Propane/Methane tanks
Date: Sat, 14 Oct 1995 16:40:17 GMT
Organization: U of Toronto Zoology
Lines: 50

In article <45kb7p$rv9@apakabar.cc.columbia.edu> pn30@columbia.net (Sea Witch) writes:
>>...In those rare circumstances where you care much about the
>>fuel cost, one of the cheaper combinations is Propane/LOX or Methane/
>>LOX.  These are widely available and quite inexpensive.  They are, of
>>course, cryogenic (but reasonably so).
>
>	Liquid Propane is not really cryogenic - its b.p. is only -42.1
>Celsius...

When folks talk about using propane/LOX, they often assume chilling the
propane to LOX temperatures.  It is still liquid there, and considerably
denser than at its b.p.

This also simplifies the vehicle design somewhat by letting you use an
uninsulated common bulkhead.  Unfortunately, you pay for it in some other
complications, like the need to pressurize with something other than
propane gas.  (Pressurizing a liquid with its own vapor works fine at
b.p., but at much lower temperatures the vapor has a strong tendency to
condense into the liquid.)

>...LPG (liquid propane gas) is so common
>and easy to deal with that it is used for home heating and cooking.
>It's also dirt cheap.

Actually, LPG stands for Liquefied Petroleum Gas and it's not pure propane,
although propane is the major component.

>>Also, what's standard practice for insulating liquid Propane/Methane
>>tanks?
>
>	Well, you know those big tanks that say Petrolane on them that you see
>at big gas stations in rural areas of the US? Those contain LPG. I
>believe they need  very little insulation...

Propane tanks for such purposes normally are not insulated at all, because
the propane is at ambient temperature.  It's liquid because of pressure,
not temperature.  In a rocket, you probably want to cool it instead,
because pressure tanks are heavy.  (Rocket tank pressurization, at least
in pump-fed rockets, typically uses much lower pressures than commercial
propane storage.)

It's actually reasonably routine in rocketry to build LOX tanks without
any insulation at all.  On the ground, a nice thick layer of frost forms,
and that's reasonably effective insulation.  When you launch, it falls
off, and after that things happen too quickly for boiloff to be a problem.
The only launcher propellant that really demands insulation is liquid
hydrogen.
-- 
The problem is, every time something goes wrong,   |       Henry Spencer
the paperwork is found in order... -Walker on NASA |   henry@zoo.toronto.edu

From: Henry Spencer <henry@zoo.toronto.edu>
Newsgroups: sci.space.tech
Subject: Re: SSTO delta-V and dense fuels
Date: Mon, 13 May 1996 19:12:21 GMT

In article <199605060711.QAA00547@igor.levels.unisa.edu.au> steven@spri.levels.unisa.edu.au (Steven Pietrobon) writes:
>...The vehicle can also have a common bulkhead between the propellants, 
>reducing weight and the size of the vehicle.

Well, that can be done even with LOX/LH2 or LOX/kerosene, although admittedly
for LOX/LH2 you need insulation.  (The LOX/kerosene common bulkhead in the
Atlas is not insulated.)

>The big disadvantage of course is that H2O2 vigourously decomposes in the
>presence of catalytic impurities. Not all impurities are catalytic. Nine times
>out of ten, nothing happens...

Well, I wouldn't have put the odds as that good. :-)  I seem to recall
seeing a comment that at least 50% of all materials are at least mildly
catalytic for peroxide decomposition.  However, the cleanliness needed to
avoid excessive peroxide decomposition is roughly comparable to that needed
to avoid fire/explosion hazards in LOX systems.  (People underestimate the
hazards of LOX.  For example, if you're using aluminum plumbing, you have
to be careful to get rid of *all* particulate contamination in the LOX,
because otherwise, when the LOX goes around a corner fast and particles
slam into the wall... the aluminum ignites.)

>>Just what was the advantage of LOX/LH2 supposed to be again?
>
>Well, the big advantage that O2/H2 has is that engines are available. The
>same is true for LOX/kero...

Well, true.  Mostly.  The difficulty of doing engine conversions tends to
be overestimated.  The Titan engines were originally LOX/kerosene engines,
and were converted to N2O4/hydrazine with only minor changes (they have
also been fired experimentally on LOX/LH2, as I recall).  Admittedly, you
won't fully exploit the advantages of peroxide unless the engines are
custom-designed (notably, to decompose the peroxide before fuel injection),
but it might be possible to do a quick conversion for proof of principle.
-- 
Unix was a breakthrough.                           |       Henry Spencer
Windows 95 is more like a smash-and-grab.          |   henry@zoo.toronto.edu

Newsgroups: sci.space.policy
From: Henry Spencer <henry@zoo.toronto.edu>
Subject: LOX (was Re: Staging flights (was Shuttle II))
Date: Tue, 11 Jun 1996 03:04:00 GMT

In article <4p9288$1v3@josie.abo.fi> mlindroo@news.abo.fi (Marcus Lindroos INF) writes:
>About LOX transfer to ordinary airports, are there any single users 
>at the moment which require several hundred tons of the stuff per 
>day...? If there are, how do they transport it - pipelines or 
>trucks?

Certain steelmaking processes use LOX, I believe, and I expect they'd use
it in such quantities.  I don't think there are any major LOX pipelines; 
when usage goes beyond the point where it's practical to truck it in, you
want to build your own LOX plant (bearing in mind that the raw material
is just air).

I'm a bit surprised that (as I recall) KSC does not have its own LOX plants.
Kourou does.
-- 
If we feared danger, mankind would never           |       Henry Spencer
go to space.                  --Ellison S. Onizuka |   henry@zoo.toronto.edu

From: Henry Spencer <henry@zoo.toronto.edu>
Newsgroups: sci.space.tech
Subject: fuel costs (was Re: HTHL vs.VTVL)
Date: Sat, 15 Jun 1996 17:02:24 GMT

In article <4pjrd6$b53@josie.abo.fi> mlindroo@josie.abo.fi (Marcus Lindroos INF) writes:
>...G.Harry Stine claims 1kg
>of LOX/LH2 costs $1.10. 23 years ago, Phil Bono (FRONTIERS OF SPACE) was
>saying one kilogram of LH2 cost fifteen times as much as a kilogram of
>LOX. Assuming an 85.5% mix of LOX by mass, the LOX cost becomes $0.363/kg
>provided LH2 is still 15 times more expensive.

That's much too high.  LOX, in quantity, costs pennies per pound -- I'm
told it goes as low as $0.01/lb if you're using enough to build your own
plant.  (Remember, the raw material is air!)

Let's see, the numbers I have on hand (USAF ones from 1991) are $0.03/lb
for LOX and $3.35/lb for LH2.  (Jeff Greason probably has more current ones.
Somewhere I've got the numbers for how much DC-X was paying, but I can't
seem to find them right now.)
-- 
If we feared danger, mankind would never           |       Henry Spencer
go to space.                  --Ellison S. Onizuka |   henry@zoo.toronto.edu

From: Henry Spencer <henry@zoo.toronto.edu>
Newsgroups: rec.arts.sf.science,rec.models.rockets,sci.space.tech
Subject: Re: Unadvisable Rocket Science
Date: Thu, 15 Aug 1996 12:23:38 GMT

>For sheer touchiness (never mind toxicity), may I suggest a 
>monopropellant which is a stochiometric mixture of liquid ozone and 
>liquid acetylene.  Of course, it tank storage lifetime may be limited 
>:-)

Alas, this particular combination almost certainly isn't going to work
even if you *can* somehow stabilize it...  Liquid acetylene is not
miscible with liquid oxygen, and hence probably won't mix with liquid
ozone either. 

(In fact, LOX plants need provisions to drain off liquid acetylene...
There's always a trace of hydrocarbons in the incoming air, especially in
industrial areas, and while most of them simply dissolve in the LOX --
which sounds alarming but is harmless at low concentrations -- the liquid
acetylene will not, so it tends to accumulate in the plumbing.)
-- 
 ...the truly fundamental discoveries seldom       |       Henry Spencer
occur where we have decided to look.  --B. Forman  |   henry@zoo.toronto.edu

Newsgroups: rec.pyrotechnics
From: tip@ai.chem.ohiou.edu (Tom Perigrin)
Subject: Re: Solid Gas
Date: Wed, 27 Nov 1996 17:00:28 GMT

In article <E1J7zJ.n0H@quest1.questconsult.com>,
tam@quest1.questconsult.com (Timothy Melton) wrote:
> 
> In article <57de8f$65i@whales.netwave.net> melody leist <melody> writes:

> 
> What's so hard about getting LOX?

Nothing.  In fact, labs that use liquid N2 to cool things have to work hard
to prevent LOX formation.   Long ago I accidentally condensed about 50 ml
of LOX in a vapor trap, along with some 2,3-dimethyl-2,3-diaminobutane
(probably about 5 grams).  I removed the dewar holding the LN2, and saw the
problem...  We replaced the dewer, and after a long discussion, decided to
remove the entire cold trap into the E2 bomb room.   Sure enough, about 10
minutes after the dewar and LN2 were removed the cold trap exploded,
turning the glass into fine shards no bigger than 1 mm.

 
> >it may freeze but liquids themselves dont burn, only the 
> >vapors, if light, the frozen block o' gas *may* start on
> 
> Yep.  Same for liquids, though.  They burn with a diffusion flame.  The
> liquid must first be vaporized to burn.
> 
> This is only true, however, if the material needs external oxygen to burn.
> HEs do a fine job of burning in the solid state.

Yup... this is an old canard that was taught to me back in undergraduate
days...  "only vapors burn".  Well, there are a few reactions that are
"gasless", such as Si/BaCrO4.

> I'm not sure, but I suspect that if you poured LOX into gasoline, it would
> spontaneously ignite.  LOX can be nasty stuff.

LOX causes many things to ignite/explode/do-bad-things.   See the above
example.  The diaminobutane took off while there was still a significant
amount of LOX.  What is surprising is that it didn't go long before... 
like, when we were moving it?  Luck, I guess.  Or perhaps the walls of the
vessel had warmed enough to provide the activation energy, even though they
must have still been way below 0.


Tom

From: gherbert@crl3.crl.com (George Herbert)
Newsgroups: sci.space.policy
Subject: Re: Orion Lite?
Date: 9 Feb 1998 14:16:02 -0800

Alexey Goldin  <goldin@spot.uchicago.edu> wrote:
>Paul Dietz <dietz@interaccess.com> writes:
>> Compare this to TNT, which yields about 4.2 megajoules per
>> kilogram when exploded.  Even LOX + RP-1 has a higher
>> energy content than that.
>>
>> The reason for the lower energy content of high
>> explosives is not hard to understand.  They are under
>> additional constraints -- storability, stability -- that
>> liquid bipropellants do not face.
>
>BTW, charcoal soaked in liquid oxygen will explode much more
>spectacularly then TNT. So will mixture of LH2+LOX. It is not used in
>place of TNT for above reasons.

Actually, LOX explosives (LOX + charcoal) are used in some places,
they can be very cheap and safe in some applications.  For example,
you drill boreholes, fill them with charcoal, and then pour in LOX
to top them off soaking the charcoal.  Highly energetic, as described.

However, it's both static and impact sensitive.  Both of which are
nonos for industrial explosives in most applications.


-george william herbert
Retro Aerospace
gherbert@crl.com

From: henry@spsystems.net (Henry Spencer)
Newsgroups: sci.space.policy,sci.space.tech
Subject: Re: Roton Reservations
Date: Thu, 11 Jun 1998 21:01:53 GMT

In article <6llsg5$60r$1@nnrp1.dejanews.com>,  <frankzeg@aol.com> wrote:
>...Recognize that
>several of the best seal materials wiht long life and good cryogenic
>properties are denied you in lO2 service- spcifically UHMW polyethylene is
>not LO2 compatible for impact.

Do bear in mind that the impact tests appear to be overly conservative.
Aluminum ignites a significant fraction of the time in impact tests, and
yet it is deemed LOX-compatible.  Note that Rotary Rocket is using unlined
graphite-epoxy LOX tanks, after considerable testing (with real hardware,
not arbitrary lab apparatus) utterly failed to reveal any likely fire or
explosion hazard.
--
Being the last man on the Moon is a |  Henry Spencer   henry@spsystems.net
very dubious honor. -- Gene Cernan  |      (aka henry@zoo.toronto.edu)

Newsgroups: sci.space.shuttle
From: henry@spsystems.net (Henry Spencer)
Subject: Re: use of shuttle ET in construction
Date: Mon, 7 Aug 2000 15:40:31 GMT

In article <398E3923.2875B433@ibm-pc.org>,
Jorge R. Frank <jrfrank@ibm-pc.org> wrote:
>> If you build a station module and flood it with propellants, then you don't
>> have to worry about orbit flaking etc since you're bringing up a component
>> which is designed for orbit to begin with.
>
>But you still need insulation - LOX and LH2 need to be kept very cold,
>otherwise they'll boil off quickly.

Boiloff is a significant problem only for LH2.  Indeed, the original ET
design had the middle section of the LOX tank uninsulated:  the nose was
insulated against aerodynamic heating, and the base was insulated to avoid
ice formation inside the intertank ring (I think), but there didn't seem
to be any special need to insulate the center section.  The Saturn V LOX
tanks were not insulated; the frost and ice just fell off at liftoff.  But
then they realized that falling ice from the ET LOX tank could damage
tiles on the orbiter, so the whole thing had to be insulated.
--
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: LOX Rankine Cycle
Date: Wed, 9 Aug 2000 01:16:31 GMT

In article <sp0i9chh63a183@corp.supernews.com>,
Pete Lynn <pete@peterlynnkites.co.nz> wrote:
>I wonder if such plants are designed to liquify all air instead of just the
>efficient liquification of oxygen...

In general they liquefy whole air and then distill it, with the fate of
the results depending on market interest in LOX and LN2.  Some years ago
the LOX industry made a concerted attempt to expand the market for LN2,
and was quite successful, so they can now sell essentially all they make.

>LOX is already cheap and there is little
>money in making it cheaper.  I think they use inefficient throttling instead
>of a turbine for the cooling...

On the contrary.  Commercial LOX plants work hard to get costs down as low
as possible; large customers do care.  The plants use expansion engines
rather than throttling, they have heat exchangers everywhere, and in
general they make strenuous efforts to be as efficient as possible.  This
is one major reason why the cycle used in a commercial LOX plant is quite
complex, not the simple single-loop design seen in elementary textbooks.

>...Another trick I had thought of was to use
>the near absolute temperature of space as your heat sink, a large parabolic
>dish focussed on the night sky.  This would work for space solar thermal,
>main heat sink at say 300 K, liquification heat sink at 100K.

Unfortunately, because radiated heat scales with the *fourth power* of
temperature, a radiator at 100K radiates only 1/100th the power per unit
area of a radiator at even 300K.  This makes it huge and extremely heavy.

>Anyway, I think that there is room to significantly reduce the price of LOX
>yet...

Extremely doubtful; see above.  In very large quantities, LOX costs about
one cent per pound.
--
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: Inflatable Spectra ET's
Date: Fri, 22 Sep 2000 15:29:51 GMT

In article <39C95E2D.B7BE8E5D@peterlynnkites.com>,
Robert Lynn  <robert@peterlynnkites.co.nz> wrote:
>What would be the most suitable membrane materials for LOX
>temperatures?

Well, basically there aren't any.  Teflon is still somewhat flexible at
cryo temperatures.  *Very thin* Mylar is sometimes usable.  That's about it.

By the way, LOX compatibility is a major issue for anything like this.
Many organic materials are dangerous explosives in a LOX environment.
--
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: Oxygen and Kerosene
Date: Sat, 16 Dec 2000 19:41:41 GMT

In article <slrn93lt7k.fv2.soup@holly.penrij.uucp.jtan.com>,
John R. Campbell <soup@jtan.com> wrote:
>>...LOX/petroleum mixtures are touchy and
>>will go off at the slightest excuse, but they don't (reliably) do it
>>spontaneously.
>
>	Actually, doesn't this require pure O2 in a gaseous state?
>	Didn't an O2 cloud (harmless to us folks) ignite spilled oil
>	on some NASA vehicles?

More precisely, it ignited the grease on their hot engines, or at least it
looks like that's what happened.  Even gaseous oxygen doesn't reliably
ignite in the presence of hydrocarbons.

>	It was advised that, under no circumstances, should the
>	charcoal be allowed to absorb the LOX before ignition since
>	just one of the briquets would be like a stick of dynamite.

Indeed so.  For similar reasons, the paving around LOX tanks (e.g. the
ones outside hospitals) is *not* asphalt, but concrete with a carefully
sealed surface.
--
When failure is not an option, success  |  Henry Spencer   henry@spsystems.net
can get expensive.   -- Peter Stibrany  |      (aka henry@zoo.toronto.edu)