JF Mezei wrote on Mon, 22 Apr 2019
20:34:34 -0400:

On 2019-04-22 07:05, Jeff Findley wrote:

Accident Claims SpaceX Dragon Abort Test Capsule
Apr 21, 2019 Irene Klotz - Aerospace Daily & Defense Report
https://aviationweek.com/space/accid...on-abort-test-
capsule

(sorry, it won't allow me to read that article).


You have to take the line break out so that it ends with '-capsule'.


Saw pictures of people on a beach with the big orange cloud at a
distance. How dangerous is burned hydrazine ? or would that cloud
contain unburned toxig hypergolics ?


Hydrazine burns to nitrogen and water. The color sounds to me like
nitrogen dioxide, which is a partial decomposition product of
dinotrogen tetroxide. Hydrazine and dinitrogen tetroxide are both
colorless.


I assume thrusters on shuttle were a simple pump that pushed the 2
compienst into a small chamnber where they mix, combust and then push
themselves out through the thruster port.

Would Draco be the same or have actual turbopumps and high
velocity/energy moving parts ?


First, it's SuperDraco, not Draco. SuperDraco is something like 200
times the size of Draco. Most hypergolic engines use simple pumps,
although turbopumps are possible in very large engines. SuperDraco
uses ordinary pumps.


Are the hypergolic tanks highly pressurized or just enough to push the
liquids to the combustion chamber ?


They're usually pressurized to above the chamber pressure of the
engine.


Trying to understand what sort of failure mode would cause the apparent
total destruction of the craft.


We don't know that there WAS "total destruction of the craft".


If the engines are simple pumps that push the hypergolics into chamnber
and they burn and exhaust, why would salt water cause such a failure?


Where did you get the idea that salt water had anything to do with it?
The engines successfully fired multiple times before the 'anomaly'.


If the engines are more complex with turbopumps and what not, wouldn't
they require fairly expensive inspections before being fired ?


They aren't and no, why would they?


If they find out that the cause of the accident was salt water, could
this allow "on time" continuation of programme using a new Dragon 2 as
test article for the pad eject test ? (aka: delay re-usability but don't
delay programme).


If they find out the cause of the anomaly WHATEVER IT WAS they will
then be able to continue the program. It looks to me like a pump
failure on the hydrazine tank, but that's just a guess and we don't
know why it failed if that was the case.


Or does this accident represent a hard stop to the programme
irrespective of cause until Space-X has designed changes to the
capsule/engines and proven it is safe to NASA ?


Regardless of the cause they are at full stop until they determine
what the cause was. They will then have to prove it's safe,
regardless of whether they have to make changes or not. There's a lot
of fire time on SuperDraco engines for me to believe there is some
fundamental design flaw.


Is it correct to assume that SpaceX would have tested engines after
having dropped them in sea water well before building the first Dragon 2
capsule ?


No, it is not, because there is no reason to do so.


--
"Some people get lost in thought because it's such unfamiliar
territory."
--G. Behn