Newsgroups: sci.space.tech
From: henry@spsystems.net (Henry Spencer)
Subject: Re: Nitric acid: Stroable oxidizer rediscovered?
Date: Fri, 9 Jun 2000 02:35:04 GMT

In article <393FE8A1.E92F8272@gte.net>, Aaron Smith  <ttocs@gte.net> wrote:
>    Why have people given up on Nitric acid for an oxidizer?

Basically, because N2O4 is better.  It has somewhat higher performance,
and if kept dry, it is much less corrosive.

Nitric acid has a few advantages, like density and lower freezing point,
but the people who really care about those things -- tactical missile
designers -- have mostly switched to solid fuels.

>with Kerosene, it has a density of 1.35g/cc and an ISP of 314.  Nitric
>acid itself is 1.51 g/cc, and that's pretty damn good.  Plus, it's a
>helluva lot cheaper than N2O4/MMH.

The costs of rocket propellants are typically "down in the noise", not
significant to launch costs.  Note also that the acid/kerosene combination
is not hypergolic.
--
Microsoft shouldn't be broken up.       |  Henry Spencer   henry@spsystems.net
It should be shut down.  -- Phil Agre   |      (aka henry@zoo.toronto.edu)

From: gherbert@gw.retro.com (George William Herbert)
Newsgroups: sci.space.tech
Subject: Re: Nitric acid: Stroable oxidizer rediscovered?
Date: 8 Jun 2000 23:50:01 -0700

Henry Spencer <henry@spsystems.net> wrote:
><ttocs@gte.net> wrote:
>>    Why have people given up on Nitric acid for an oxidizer?
>
>Basically, because N2O4 is better.

Phbhht.

I think we need to have a (late night, properly lubricated)
propellants panel discussion at the next Space Access.
Save us from the @#$&@*# (but important and necessary) business talk ;-)

>It has somewhat higher performance,
>and if kept dry, it is much less corrosive.

If inhibited, Nitric Acid is very low corrosion on aerospace alloys.
There seems to have been somewhat of an underestimation of tetroxide's
corrosivity over time, too, I hear stories about spots inside the
retired Titan II ICBMs having had pretty bad spot corrosion, though I
haven't found any reports or papers confirming the stories.

>Nitric acid has a few advantages, like density and lower freezing point,
>but the people who really care about those things -- tactical missile
>designers -- have mostly switched to solid fuels.

Nitric acid is chemically safer (IWFNA at least, with no dissolved
tetroxide and inhibited with 0.5 to 1% HF so that it's not really
corrosive with metals); less of a fume hazard, the fumes which it
does produce don't corrode your lungs out faster than you can get
to a hospital, etc.

The improved density just about makes up for lost Isp from booster
design points of view (Density Impulse), and its improved safety
handling makes using it much much easier.  You basically can't ship
large quantities of nitrogen tetroxide around without armed guard and
your own ready hazmat cleanup team; nitric acid is shipped in unguarded
trucks and tanker traincars with no more precaution than the usual
hazmat placards on the truck and the proper bill of lading info for
the driver.  The difference between world class hazardous material
and merely somewhat dangerous industrial chemical is immense,
in liability and cost and handling danger (to staff and visitors
and neighbors).

>>with Kerosene, it has a density of 1.35g/cc and an ISP of 314.  Nitric
>>acid itself is 1.51 g/cc, and that's pretty damn good.  Plus, it's a
>>helluva lot cheaper than N2O4/MMH.
>
>The costs of rocket propellants are typically "down in the noise", not
>significant to launch costs.  Note also that the acid/kerosene combination
>is not hypergolic.

Everyone keeps saying that the fuel costs are down in the noise.

Down in the noise, however, I am finding the opposite.  Admittedly the
best alternative is cheap too (LOX) but HNO3's cost is a big plus in
development programs, particularly if you don't happen to have a billionare
backer to pay your peroxide bills.  Also admittedly, not very many people
are doing things the way I am, and they might be right, but cost is not
all that insignificant.

Nitric/Kero isn't hypergolic but there are fuels which are adequate
performance and cost and safety (furfural alcohol, *cough* turpentine)
which it is hypergolic with.  With a bit of encouragement you can make
Nitric/Gasoline hypergolic, but the longer chain kerosene hydrocarbons
burn rougher (and people keep trying diesel fuel with it from time to
time despite it's being much worse that way, sooty and terrible combustion
behaviour...).


-george william herbert
gherbert@retro.com

Newsgroups: sci.space.tech
From: henry@spsystems.net (Henry Spencer)
Subject: Re: Nitric acid: Stroable oxidizer rediscovered?
Date: Sat, 10 Jun 2000 18:23:07 GMT

In article <8hq42p$qq0$1@gw.retro.com>,
George William Herbert <gherbert@gw.retro.com> wrote:
>Nitric acid is chemically safer (IWFNA at least, with no dissolved
>tetroxide and inhibited with 0.5 to 1% HF so that it's not really
>corrosive with metals); less of a fume hazard...

Of course, it tends to turn itself *into* IRFNA, which is a horse of a
very different color, both literally and figuratively...

(Straight nitric acid is not 100% stable, it turns out.  It slowly
decomposes to water, oxygen gas, and N2O4.  The water just dilutes things
a bit, the oxygen bubbles out -- which is fine unless you're trying to
keep the stuff in a sealed tank -- and the N2O4 slowly turns your WFNA
into RFNA.)

In practice, this just means you have to use the stuff promptly.

>...The difference between world class hazardous material
>and merely somewhat dangerous industrial chemical is immense,
>in liability and cost and handling danger (to staff and visitors
>and neighbors).

True.  Back when the Lunaris project -- the amateur moonrocket -- briefly
seemed to be a going concern, I argued long and hard for using WFNA and
furfuryl alcohol as the propellants.  They're storable at room temperature
and atmospheric pressure, they're commercially available in bulk, and they
aren't especially hazardous.  (And that combination has reasonable Isp and
is reliably hypergolic.)

Bear in mind, though, that the original poster was asking more about
large-scale professional rocketry than about the innovative small fry.
--
Microsoft shouldn't be broken up.       |  Henry Spencer   henry@spsystems.net
It should be shut down.  -- Phil Agre   |      (aka henry@zoo.toronto.edu)

From: "Jeff Greason" <jgreason@hughes.net>
Newsgroups: sci.space.tech
Subject: Re: Nitric acid: Stroable oxidizer rediscovered?
Date: Mon, 12 Jun 2000 11:03:51 -0700

Aaron Smith <ttocs@gte.net> wrote in message
news:393FE8A1.E92F8272@gte.net...
> Hi everyone...
>
>     Why have people given up on Nitric acid for an oxidizer?  I was
> looking at Encyclopedia Astronautica (very good source,BTW) and It says
> with Kerosene, it has a density of 1.35g/cc and an ISP of 314.  Nitric
> acid itself is 1.51 g/cc, and that's pretty damn good.  Plus, it's a
> helluva lot cheaper than N2O4/MMH.  I know some of the people here are
> going to say "it's toxic!" but what is N2O4?  Just some thoughts...

Propellant selection (like most engineering) depends on what your
constraints or goals are:

* If you want storability with maximum performance, and cost and
   toxicity are no object (i.e., any military and most NASA hardware
   prior to 1996), N2O4 is higher Isp at competitive density-impulse

* If you want cheap propellants, LOX is cheaper and higher Isp,
   and a heck of a lot less difficult to get environmental permits for.

* If you want high density-impulse, LOX is only slightly worse, and
   peroxide is at least as good, with simpler handling properties.

* In order to make nitric acid storable, you have to dissolve N2O4 in
   it and inhibit it (IRFNA), which makes it a toxic fuming nasty
   propellant to handle, and puts enough HF in your exhaust to make
   the EPA unhappy.  If you take the HF out, it becomes very difficult
   to store for any length of time in reasonable tanks.  If you take the
   N2O4 out (white fuming nitric acid, WFNA), it becomes
   substantially *less* shelf-storable than H2O2, decomposing into
   water and RFNA over time.

I see little future for IRFNA outside of purely amateur efforts; if
you can accept the N2O4 and HF once you're a real business, you
probably have the budget for straight N2O4 or H2O2 or the budget
to hire people who know how to handle LOX.  In applications where
propellant cost and density both matter (such as a large pressure
fed similar to that being done by Beal), WFNA *may* make sense
(it's at least 10x cheaper than peroxide at similar density and
 performance), but it's tough to show a win over LOX systems
unless you make very specific assumptions about materials and
operations.

In the back of my mind, I keep hoping for a way to stabilize WFNA
against decomposition other than putting N2O4 into the acid; that
would make it much more attractive as a long-term storable for
in-space propulsion -- but while there are interesting hints that a
dash of H2O2 might do the trick, propellant research is a long,
expensive, and generally low ROI endeavor.

----------------------------------------------------------------
"While dramatic ventures can be            Jeff Greason
 invigorating, they can also make us lose  President & Eng. Mgr.
 sight of the amazing achievements that    XCOR Aerospace
 occur bit by bit"                         <jgreason@hughes.net>
 -- V. Postrel, The Future and its Enemies <www.xcor-aerospace.com>

From: "Jeff Greason" <jgreason@hughes.net>
Newsgroups: sci.space.tech
Subject: Re: Nitric acid: Stroable oxidizer rediscovered?
Date: Thu, 15 Jun 2000 22:19:56 -0700

Jeppe Locht <lochtREMOVETHIS@bigfoot.com> wrote in message
news:k%c25.487$ts.16539@news.get2net.dk...
> You can say that decomposed WFNA _looks_ like RFNA but it is not the same.
>
> (Do I get my ICHT #2 now?)

Unlikely.  WFNA (white fuming nitric acid) and RFNA (red fuming nitric acid)
do not by themselves fix concentration.  WFNA needs to be above about 70%
or it wouldn't be fuming.  WFNA needs to have low N2O4 dissolved in it,
or it wouldn't be white.  When 4*HNO3 -> 2*N2O4 + 2*H2O + O2, the
O2 goes off and the acide dilutes and gets N2O4 in it -- but by the
time you have enough N2O4 to turn red, you're still at a plenty high enough
concentration to be fuming.  So WFNA does indeed turn into RFNA.

Of course, RFNA or IRFNA are often used as an engineering shorthand
for something specific, namely type III-A nitric acid, which is 14% NO2,
1.5-2.5% H2O, 0.7% HF, balance HNO3.  But RFNA is also used
as a simple abbreviation for nitric acid which is both red and fuming.

Of course the *real* use of RFNA as an abbreviation is simply because
dealing with a propellant called "Red Fuming Nitric Acid" sounds too
scary :-)

----------------------------------------------------------------
"While dramatic ventures can be      Jeff Greason
 invigorating, they can also make us lose   President & Eng. Mgr.
 sight of the amazing achievements that     XCOR Aerospace
 occur bit by bit"        <jgreason@hughes.net>
 -- V. Postrel, The Future and its Enemies  <www.xcor-aerospace.com>

From: "Jeff Greason" <jgreason@hughes.net>
Newsgroups: sci.space.tech
Subject: Re: WFNA AND Ethyl Alcohol
Date: Mon, 18 Sep 2000 15:30:51 -0700

"Maurizio Natali" <maunat@hotmail.com> wrote in message
news:F36UghLpx3VTMvTN3W90000882f@hotmail.com...
> Because liquid oxigen is in many ways more dangerous than nitric acid, i
> have decide the use of the nitric acid as oxider.

I *strongly* suggest you re-think that conclusion.  I would also suggest
that before you go too much further you seek out people with actual
handling experience with your candidate propellants and learn from
them.  Both propellant grade nitric acid and liquid oxygen (really, any
liquid oxidizer) need to be handled with proper respect.


> But in two years of searchs, i have find in italy, only nitric acid with
> concentration of just 68%.
> Seeing that, using nitric acid at 68% how oxider, obviously i don't obtain
> any results, i have decide of concentrate it.
> The method that i have decide of use involves using concentrated 94%
> sulfuric acid to dehydrate the 68% nitric acid.
> I have write, because i would know, if you know this method to concentrate
> nitric acid, or you know other methods.

I suggest a thorough perusal of J. Clark's, _Ignition!_ before going
any further.  It's available at:

http://wwwlib.umi.com/bod/fullcite?id=130299

Also, when you find that the chemical you want is not commercially
available in your area -- think again.  Usually it's *far* cheaper and safer
to work with a propellant you can buy than to try and produce your
own.  There are often good reasons why the chemical industry doesn't
produce the high concentration you might want.

In the case of nitric acid, the chemical factory probably *does* produce
high concentration for use in explosives manufacturer -- I believe Dyno
Nobel produces a lot of the nitric acid for European consumption.
Getting them to sell it to you may be difficult unless you have proper
facilities, however.

> So i would hear if you know the ignition time of the hno3 and ethyl Alcohol.
> What is the ignition time of the commercial gosoline and hno3?
> What is the ignition time of the commercial kerosene and hno3?

Ethyl alcohol, gasoline, and kerosene are NOT hypergolic with HNO3.

> What are other hypergolic fuel that have little ignition time with hno3?

You can read about many of the options tried in _Ignition!_.

----------------------------------------------------------------
"Limited funds are a blessing, not         Jeff Greason
a curse.  Nothing encourages creative      President & Eng. Mgr.
thinking in quite the same way." --L. Yau  XCOR Aerospace
   <www.xcor-aerospace.com>                <jgreason@hughes.net>

From: Doug Jones <random@qnet.com>
Newsgroups: sci.space.tech
Subject: Re: WFNA AND Ethyl Alcohol
Date: Sun, 17 Sep 2000 11:14:01 -0700

Maurizio Natali wrote:
>
> Dear people,
> i am an italian lover of rocketry; i am a student of physics and my main
> interest are the rockets engines, that works with liquids propellants.
> I have begin to work with solid rocket ( also engine with more of 1 kg of
> propellant ), since several years, but now i want begin to work with liquid
> rocket.
> Because liquid oxigen is in many ways more dangerous than nitric acid, i
> have decide the use of the nitric acid as oxider.

Okay, LOX is cryogenic, and can sometimes ignite some things
spontaneously.  Nitric acid isn't cryogenic, and can usually ignite a
lot of things spontaneously.  It's also corrosive and toxic- this is
better than LOX?

> But in two years of searchs, i have find in italy, only nitric acid with
> concentration of just 68%.

This should tell you something.  Strong acid is nasty stuff, emitting
toxic fumes.

> Seeing that, using nitric acid at 68% how oxider, obviously i don't obtain
> any results, i have decide of concentrate it.

Concentrating acid (or peroxide) from dilute feedstocks is a diversion
that can eat huge amounts of time and resources.  I don't recommend it.

> The method that i have decide of use involves using concentrated 94%
> sulfuric acid to dehydrate the 68% nitric acid.

Then how do you get the H2SO4 out?  Although mixed acid may ignite
fairly well, it is still low performance and will emit horrid amounts of
SO2 in the exhaust.  This would probably violate air pollution laws in
your area.

> I would work with white fuming nitric acid, because red fuming nitric acid
> is very dangerous to handling.

Yep. I strongly recommend N2O, nitrous oxide, for any hobbyist.  It is
nontoxic, non corrosive, and very forgiving of oily contamination
(unlike oxygen).  It pressurizes itself, no nitrogen or regulator
required, and evaporates harmlessly if spilled.

> I would use hno3 and Furfuryl Alcohol, because they are hypergolic and
> because their ignition time is wery little, about 20 ms.
> But i don't find quickly the Furfuryl Alcohol.

If you absolutely must continue down this path, check with the Quaker
Oats people- IIRC, furfuryl alcohol is a byproduct of making oatmeal.
Some things are just plain weird.

> So i would hear if you know the ignition time of the hno3 and ethyl Alcohol.

As far as I know, that combination is not hypergolic.

> What is the ignition time of the commercial gosoline and hno3?
> What is the ignition time of the commercial kerosene and hno3?

Both are dangerously variable- hypergols *MUST* ignite without delay,
else you can get unreacted mixtures accumulating in the chamber before
they light off, destroying the engine.

> What are other hypergolic fuel that have little ignition time with hno3?
> Waiting impatiently your answers, i thank you for every.
> Maurizio Natali

My advice: switch to N2O and use a pyrotechnic igniter if you don't need
restart.  Use a burn wire to detect proper pyro operation before main
propellant valve actuation, else you can get a hangfire and hard start.

The best route is to build an augmented-spark igniter. This is basically
a tiny rocket engine with a spark plug and at least one gaseous
propellant supply which prevents destructive mixtures from accumulating
even in the worst case (the N2O in N2O/alcohol will vaporize and sweep
the mist out, keeping the energy density low).  Use a pressure switch to
detect proper igniter operation before opening the main propellant
valves.

Nitric is not your friend.

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

Newsgroups: sci.space.tech
From: henry@spsystems.net (Henry Spencer)
Subject: Re: WFNA AND Ethyl Alcohol
Date: Thu, 21 Sep 2000 00:30:06 GMT

In article <8q68rv$6hr$1@gxsn.com>, Ed Nelson <ednelson@waitrose.com> wrote:
>Try Aniline (aminobenzene; C6H5NH2) as an alternative hypergolic fuel. Its
>definitely hypergolic with RFNA, but I don't know about WFNA or mixed acid...
>Xylidine and some amides might also work. Or of course theres Hydrazine if
>you want to get poisoned...?

While aniline is not *as* poisonous as hydrazine, it's still decidedly
dangerous -- poisonous in fairly small doses by ingestion, inhalation, or
skin contact.

The nice thing about furfuryl alcohol is that it is reliably hypergolic
with WFNA or RFNA, while being a fairly innocuous industrial solvent.
(You wouldn't drink the stuff, but it's not in the same league as aniline
or hydrazine when it comes to toxicity.)
--
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: WFNA AND Ethyl Alcohol
Date: Thu, 21 Sep 2000 01:50:41 GMT

In article <39C509E9.3BECD395@qnet.com>, Doug Jones  <random@qnet.com> wrote:
>> What is the ignition time of the commercial gosoline and hno3?
>> What is the ignition time of the commercial kerosene and hno3?
>
>Both are dangerously variable- hypergols *MUST* ignite without delay,
>else you can get unreacted mixtures accumulating in the chamber before
>they light off, destroying the engine.

Also of note:  the US military spent really large amounts of money looking
for some way, *any* way, to make those fuels reliably hypergolic with HNO3.
They really, really wanted to be able to fuel their missiles with aviation
fuel rather than needing special rocket fuel.  They couldn't do it.
--
Microsoft shouldn't be broken up.       |  Henry Spencer   henry@spsystems.net
It should be shut down.  -- Phil Agre   |      (aka henry@zoo.toronto.edu)

From: "Jeff Greason" <jgreason@hughes.net>
Newsgroups: sci.space.tech
Subject: Re: re: wfna and ethyl alcohol
Date: Thu, 21 Sep 2000 10:58:23 -0700

"Maurizio Natali" <maunat@hotmail.com> wrote in message
news:F115uAQBpCly49nLJ800000748b@hotmail.com...
> LOx is in many ways more dangerous than nitric acid. You must keep
> EVERYTHING free of grease or oil because LOx and kerosene or any petroleum
> product can detonate and kill or severly injure you.
> So i have decide of use WFNA.

Of course, the choice of propellant depends on a lot of variables.
But don't kid yourself.  The need to keep potential fuels and ignition
promoters out of the system is a characteristic of oxidizers, not
just liquid oxygen.   When it comes to oxidizer systems, cleanliness
is something you really want to pay attention to, regardless of
the oxidizer you're using.

I think nitric acid may well have it's place -- though the NO2 fumes
make it problematic.  I don't know of any way to suppress NO2
production without additives which are as much trouble in their
own way.  Put enough N2O4 in it to keep it from decomposing,
and NO2 production is much worse when poured or spilled.  Put
enough sulfuric or other SO2 bearing acid into it to suppress
NO2 production, and there's enough sulfur in the exhaust to be
a problem.  Corrosivity is a real problem for long-term storage,
and putting enough HF into it to contain that puts enough HF in
the exhaust that (in the U.S. at least), the EPA would be unhappy
with you.

It's the second-cheapest oxidizer out there, and density-impulse
product is similar to LOX combinations, so I understand why
it's attractive.  The drawbacks are pretty fierce, however.  I keep
thinking that if only there were a way to suppress NO2 production
with some less-nasty additive ... but I haven't found one yet.

----------------------------------------------------------------
"Limited funds are a blessing, not         Jeff Greason
a curse.  Nothing encourages creative      President & Eng. Mgr.
thinking in quite the same way." --L. Yau  XCOR Aerospace
   <www.xcor-aerospace.com>                <jgreason@hughes.net>

From: gherbert@crl3.crl.com (George Herbert)
Newsgroups: sci.space.policy
Subject: Re: Cheap Access to Space rocket prize (WAS: Pass the ComSpace Act)
Date: 2 Mar 1998 13:27:29 -0800

Pierce Nichols  <pn30@columbia.edu> wrote:
>George Herbert wrote:
>> >SERIOUSLY, why do you think nitric acid, frozen or not, is safer than
>> >everything else, given the quantities involved?
>> >I would have thought the corrosion problems would be prohibitive.
>>
>> Use inhibited nitric acid (0.6% HF added).  Won't corrode most metals.
>> You get a flouride coating and it's resistant to the HNO3.
>
>	George, I know you generally have a clue, so I'm not going to go with
>my initial response to this idea (which is along the lines of "why work
>with one nasty acid when you can have two for the same price?"). But
>please explain it more in depth...

There isn't enough HF in the mix to noticably increase the
corrosive capabilities on materials that don't form the
flouride barrier.  Nor for there to be serious toxicity
problems with the mix.  It's a tad more expensive, but it really
is safer to handle than pure HNO3 (since it doesn't require
intact liners between the acid and metals) and than nitrogen
tetroxide (which is corrosive and has a whole boatload of
biological effects).  It really is the safest acid for
propellant use, although slightly less performance than
nitrogen tetroxide.  In performance terms, hydrogen peroxide
is better (as is nitrogen tetroxide), and hydrogen peroxide
is also safer (noncorrosive on metals, and as long as the
concentrated stuff doesn't spill ON people, cleanup is
easy and the fumes are not a problem).  However, peroxide
costs 10 times what inhibited nitric acid does.  At $0.50-0.75/lb
it's a poor choice for big dumb boosters where you'll have
more than 100 times the payload weight in oxidizer at liftoff...

There might conceivably be enough operational advantages to
peroxide to outweigh the cost, but without actual experience
building and flying vehicles regularly it's hard to tell.
My analysies so far tell me to go with inhibited nitric acid,
corrosivity and fume hazard and all.



-george william herbert
Retro Aerospace
gherbert@crl.com