[ExI] Patent search was [AR] Planned FAA LOX-Methane Safety Studies?

[Keith Henson]

>From below (a post on the a-rocket list)

> Anyone know anything more about this?  Something we've discussed around
> here occasionally.  Looks like FAA (later also a NASA/Space Force
> followon) is planning a drop-test program to get more data on
> appropriate explosive-equivalence assumptions for LOX-LCH4 rocket safety
> planning.

The FAA is concerned about the effects of mixed LNG and LOX, unlikely
as it is that the common bulkhead could fail.

The day after this post, I woke up musing about the recent postings on a-rocket.

The FAA concern is bulkhead failure, intimate mixing of the liquid
methane and LOX, and a shock to make a big boom.

Burning on contact makes a heck of a fire, but no shock wave.

I thought up a passive, low-cost, and reliable way; to assure a fire
rather than mixing.  Put an open container of triethylaluminum in the
top of the liquid methane tank.  "It is one of the few substances
sufficiently pyrophoric to ignite on contact with cryogenic liquid
oxygen." (Wikipedia). Waited till the check to the patent office
cleared before posting this.

(SpaceX will have to put the LNG tank below the LOX tank, but they had
it this way earlier.)

Of course, the problem with filing a patent is that you might not have
been the first to think of the concept.  That takes an expensive
search.  If anyone here knows of something similar where there is a
method to start a fire to avoid an explosion, I would sure like to
hear of it.  It might save me a bucket of money.

Keith

(below)
From: Henry Vanderbilt <hvanderbilt at mindspring.com>
Subject: [AR] Planned FAA LOX-Methane Safety Studies?
Date: Tue, 23 May 2023 09:25:05 -0700

Anyone know anything more about this?  Something we've discussed around
here occasionally.  Looks like FAA (later also a NASA/Space Force
followon) is planning a drop-test program to get more data on
appropriate explosive-equivalence assumptions for LOX-LCH4 rocket safety
planning.
Jeff Foust/Space News piece at
https://spacenews.com/agencies-studying-safety-issues-of-lox-methane-launch-vehicles/

This sentence from the story is causing me some head-scratching. RE the
planned FAA tests, "A crane 43 meters tall will be used to drop
stainless steel containers containing mixtures of LOX and methane."

So is that going to be drop tests of, stainless containers with separate
LOX and LCH4 tanks, IE subscale representative booster sections?  That
is what I'd (perhaps naively) think would yield useful data about
potential worst-case LOX-methane booster pad-dropback accidents.

But that sentence makes it sound like they may be going to pre-mix the
LOX and methane before drop tests.  Which causes me puzzlement, because
isn't premixed LOX and LCH4 also known as "sensitive high explosive"?
Which would make for fun LOUD Ka-Booms on impact, but may not yield a
lot of new knowledge?  Or am I missing something?  Perhaps testing bulk
impact sensitivity of varying pre-mix ratios, rather than likely rocket
near-stoichiometric? I'm still not sure how that might be relevant
knowledge, but, always willing to learn...

Normally I'd just assume reportorial imprecision, perhaps exacerbated by
interviewee imprecision, word-count limits, and/or deadline pressure.
But, well, this is Jeff Foust (Hi Jeff, if you're on here!)  Anyone have
any theoretical light to shed on this?  Or, given this crowd, actual
knowledge of what FAA is looking to do here?

Henry

------------------------------

From: John DeMar <jsdemar at gmail.com>
Date: Tue, 23 May 2023 10:34:42 -0600
Subject: [AR] Re: Planned FAA LOX-Methane Safety Studies?

More here:
https://www.faa.gov/sites/faa.gov/files/508.10-Spring-2023-REDAC-NAS-Ops-AST-Update.pdf
Likely separate tanks, similar to this test 3 years ago at Dugway:
https://www.army.mil/article/235745/rocket_fuel_test_finds_dugway_ideal

  -John

------------------------------

Subject: [AR] Re: Planned FAA LOX-Methane Safety Studies?
From: Henry Vanderbilt <hvanderbilt at mindspring.com>
Date: Tue, 23 May 2023 09:59:11 -0700

Interesting.  The FAA tests will start with a calibration shot of 1000
lbs of c-4.  (!)  Then drop tests of 2000 lbs LN2, then 2000 lbs
LOX/LCH4 twice, pressurized then unpressurized, then 20,000 lb LOX/LCH4
pressurized then unpressurized, then 500 lb LOX/LCH4 pressurized then
unpressurized.  No specific statement on mix ratio or separate tanks
versus single-tank premix.  Perhaps they assume it goes without saying.
Dugway tests were with a glass common bulkhead between the propellants
in a notional vertical-cylinder rocket body, guesstimating from the
photo ~4 ft diameter and ~20+ ft total tanks length.  They started the
tests by breaking the glass, with a delayed ignitor present in case
breaking the glass hadn't already lit things off.  Not much detail on
results, beyond this:

"The last COMET test, with large amounts of LNG/LOX, produced an
especially strong blast, creating a large crater and damaging critical
test equipment. The curved lid of the tank shot up like a flying saucer,
and landed 800 feet away."

Henry