[ExI] Fwd: [AR] Planned FAA LOX-Methane Safety Studies?

[Keith Henson]

You might be amused by this post.

---------- Forwarded message ---------
From: Keith Henson <hkeithhenson at gmail.com>
Date: Tue, Jun 6, 2023 at 8:57 PM
Subject: [AR] Planned FAA LOX-Methane Safety Studies?
To: <arocket at freelists.org>

On Tue, May 23, 2023 at 6:06 PM Henry Vanderbilt
<hvanderbilt at mindspring.com> wrote:

> 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.

Wanted to run it by Henry Spencer before trying to find a way to get
the idea to SpaceX or the FAA.

Keith

> 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
>
> On Tue, May 23, 2023 at 10:25 AM Henry Vanderbilt <
> hvanderbilt at mindspring.com> wrote:
>
> > 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
> >
> ------------------------------
> 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
>
> On 5/23/2023 9:34 AM, John DeMar wrote:
> > More here:
> > https://www.faa.gov/sites/faa.gov/files/508.10-Spring-2023-REDAC-NAS-Ops-AST-Update.pdf
> > <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
> > <https://www.army.mil/article/235745/rocket_fuel_test_finds_dugway_ideal>
> >
> >   -John
> >
>