[AR] Re: Hydroxylammoniumnitrate (HAN)
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Mon, 3 Apr 2017 13:41:43 -0400 (EDT)
On Mon, 3 Apr 2017, Galejs, Robert - 1007 - MITLL wrote:
I was under the impression that the "green" monopropellants were based on
HAN...
Some are, some aren't. LMP-103S, the Swedish one, is based on ADN
instead.
At Space Access last year, John Schilling (who's worked on these things)
described the USAF's AF-M315E as "HAN plus HEHN plus stabilizers plus
water", if I remember correctly. (HEHN is hydroxyethyl hydrazine
nitrate.) He went on to add that the details are still not public and you
really need to get the stabilizers *right* to make that mixture halfway
safe to handle.
Maybe they found the magic sauce to keep things orderly in an engine?
Maybe. :-) Energetic monopropellants historically are treacherous, prone
to finding lethal new ways to produce loud surprises. It's easy for
people to kid themselves that they've found the magic sauce, but they're
usually wrong, and learning this is often traumatic. The ALASA guys were
supposedly within about six months of flight when KABOOM KABOOM told them
that Boeing didn't have their monoprop's problems as well under control as
they thought. (Fortunately, ALASA's N2O/acetylene mixture was frightening
enough that nobody forgot that they were dealing with a liquid high
explosive, and they proceeded accordingly, so nobody was hurt.)
Also, you need to read the fine print carefully and discount the marketing
hype. Sure, LMP-103S and AF-M315E are non-explosive -- at their nominal
compositions. What happens if you spill some without noticing it, perhaps
due to a small plumbing leak, and it manages to dry out completely
(perhaps not easy) -- is the residue dangerous? (Answer: it's probably a
sensitive high explosive!) And as Anthony has already noted, some of
those chemicals aren't anything you want on you or in you, even if they
aren't quite as aggressive as hydrazine.
And do remember that the guys who *developed* these mixtures had plenty of
explosions along the way. Experimental work with energetic monoprops is
unusually dangerous even by rocketry standards -- people keep finding new
ways to die. Any attempt at it should assume that your propellant *is* a
dangerous high explosive: think remote mixing, very small quantities,
detonation traps, carefully-written checklists for returning to a safe
state even if valves freeze or plumbing leaks or software crashes or the
power goes out. Don't forget blast shields, firefighting gear, and
independent safety reviews.
Henry
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