Tips & wisdom:
- Bench-test the propulsion plumbing to be purged for angles and
crannies where liquid can accumulate without being cleared by the purge.
Either redesign to eliminate the angles and crannies, or beef up the
purge pressure/duration, or redirect the purge inlet connection(s) to
jet them clear regardless. Or all the above.
- CO2 works on kerosene. As long as your prevalves get closed so
there's no fresh LOX and fuel arriving at the scene. At that point,
nothing works (short of a firetruck-level deluge sufficient to quench
things entirely, and that can still be iffy.) So make sure your
rehearsed procedure involves instantly shutting prevalves too if the
engine is shut down for an anomaly. No guarantee the main valves will
still be working, for a sufficient definition of anomaly.
- If you see a significant runtime anomaly in the video after an
engine test, stop and do a thorough engine inspection, with teardown if
necessary. Chances are there's a reason for the anomaly. (One possible
reason is injector damage from a transient in the final stages of the
previous run's shutdown, leading to fuel migration into a LOX manifold
after the second, visually-anomalous damaged-injector run, leading to
BANG the next time the engine is started. A three-parter.
Hypothetical, of course.) Do NOT just test again in the hope that the
anomaly will go away on its own.
- If you're onsite for a test, have your emergency actions thoroughly
rehearsed in your head. If you haven't, when it hits the fan you'll
just stand there in shock trying to think, or you'll do something random
(and most likely wrong.) Both are flavors of panic. Have a plan, have
it rehearsed, even if only via repeated internal visualization.
Different people react differently. Joel recalls teleporting. I recall
everything in slow motion - pick up extinguisher, start running the
twenty feet from my vidcam position to the aft end of the vehicle while
grabbing pin, lift elbow so removal is a straight pull (you will not be
doing anything gently at that point, so don't count on an off-line pull
not jamming it), stop a few feet short of the vehicle and extinguish a
burning chunk of composite on the ground (I'd rehearsed "don't leave
fire behind you" which is a good general rule, albeit unnecessary that
time given the lack of further fuel release - but you will do what
you've rehearsed; you won't have time to think) then step up and begin
extinguishing the various burning bits in the aft end of the propulsion
system.
At about that point Mike Laughlin showed up on the other side, also with
a CO2 extingiusher (he'd had to grab it from someone standing there in
shock) and we got that thing quenched. It subjectively seemed to take
minutes. What did we pull off the audio, Randall, two-three seconds
from BANG to first extinguisher discharging, maybe ten more seconds to
extinguishers stopped? (No vid, alas, due to a failed experiment in
stopping the cam down to get internal plume details.)
Heh. After remembering that, I won't need any more coffee for a while now.
Henry
On 4/26/2016 1:47 AM, Randall Clague wrote:
As far as is gas purge good enough to get all the fuel out of the LOX
system, sure, that's never been a probTHUMP. Huh. OK, I guess that is
sometimes a problem. Tempted to #facepalm, but it was a legitimate
learning experience. On the basis of which, I tell people, if you don't
have to switch from IPA to kerosene, don't. If you get IPA in the LOX
manifold, it will evaporate overnight. Kerosene, with its much lower
vapor pressure, will not. Then you get to see how your crew deals with
an emergency.
(Joel Brinton won my eternal admiration for his aplomb in the after
action: "I teleported to the pickup truck - I wished to be there, and
then I was - grabbed the burn kit, and got ready to haul the pilot out
the right side." "Over the stick?" "If necessary." "That would have
hurt." "Not as much as being on fire.")
There's also fire fighting: water and IPA are infinitely inter-miscible.
You can dilute an IPA spill to non-flammability by throwing water on it
in almost any fashion. With kerosene, if you dump a lot of water on it
as a random deluge, you can float the burning kerosene away, to the
great displeasure of your lower-elevation neighbors.
-R
On Tue, Apr 26, 2016 at 12:00 AM Uwe Klein <uwe@xxxxxxxxxxxxxxxxxxx
<mailto:uwe@xxxxxxxxxxxxxxxxxxx>> wrote:
Am 26.04.2016 um 05:45 schrieb Henry Spencer:
> On Mon, 25 Apr 2016, David Weinshenker wrote:
>>> (That said, a lot of rockets have used aluminum tanks for ethanol,
>>> without difficulties that I know of.)
>>
>> Is ethanol even particularly corrosive to aluminum in the first
place?
>
> "Particularly", perhaps not, but slightly, yes. Enough to be a
concern
> on prolonged exposure, anyway -- I believe it's an issue in
substitution
> of bioethanol for gasoline as a vehicle fuel. I'd expect that much
> depends on details like the exact alloy and the water content of (and
> other impurities in) the ethanol.
Most issues i've heard of are related to incompatible elastomerics.
( seals and hoses )
As water is fully mixable with alcohol the biofuels can carry more
water? ( What previously gummed up the tank bottom.)
uwe
