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  #11  
Old June 26th 19, 09:51 AM posted to sci.space.policy
Fred J. McCall[_3_]
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JF Mezei wrote on Tue, 25 Jun 2019
22:57:25 -0400:


When was the last time Boeing had a new manned vehicle with ejection
capability?


Never. And they still won't, since Starliner doesn't have "ejection
capability", either.


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"Some people get lost in thought because it's such unfamiliar
territory."
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  #12  
Old June 26th 19, 09:34 PM posted to sci.space.policy
Greg \(Strider\) Moore
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"Fred J. McCall" wrote in message
...

"Greg \(Strider\) Moore" wrote on Tue,
25 Jun 2019 15:51:12 -0400:

"JF Mezei" wrote in message ...

Dragon had a failure in a critical system which prevents the test of
this critical system (abort in flight).

Starliner hasn't had any failures because it is behind and hasn't even
had unmanned test.

Assuming SpaceX has found the cause and knows how to fix it, Dragon
could be back in business and still be quite ahead. SpaceX appears have
a new policy of not letting Musk say much, so I don't know that one can
derive a conclusion from lack of news.


When Boeing starts its tests, it could work flawlessly or not. We have
to wait. Will they also have a max-Q abort test? That would seem to
require at least 2 test flights right?


I have not seen a max-Q abort test for Starliner planned. I may have
missed
it, but I don't think so.
I think NASA is still treating Boeing as "they've done this before, we can
trust them a bit more."
And perhaps after the recent SpaceX explosion, they might be right.


I tend to put it more down to relative cost of the two boosters. I
suspect it was SpaceX's choice to do a 'live test' for a Max-Q abort.


Yeah, I guess I didn't add the comment I thought I had, but I suspect SpaceX
feels it's cheaper to do a live test because for them it's a fairly small
incremental cost (fuel and if there's overtime added to the workflow). For
Boeing, it's a much steeper cost and they probably are comfortable enough
saying it's cheaper to do ground testing than "waste" a booster.

Wikipedia shows that test as scheduled for late July using a previously
flown booster, but I wonder if the abort test will destroy the booster.

--
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IT Disaster Response -
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  #13  
Old June 27th 19, 11:50 AM posted to sci.space.policy
Jeff Findley[_6_]
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In article ,
says...

Dragon had a failure in a critical system which prevents the test of
this critical system (abort in flight).

Starliner hasn't had any failures because it is behind and hasn't even
had unmanned test.


Starliner has had its share of issues. Notably, during a ground test of
its abort system, Starliner experienced leaks of hypergolic propellant.
This necessitated some redesigns in the valves/plumbing, if memory
serves.

Assuming SpaceX has found the cause and knows how to fix it, Dragon
could be back in business and still be quite ahead. SpaceX appears have
a new policy of not letting Musk say much, so I don't know that one can
derive a conclusion from lack of news.


When Boeing starts its tests, it could work flawlessly or not. We have
to wait. Will they also have a max-Q abort test?


No. Only SpaceX elected to do a max-Q abort test. Boeing will "prove"
their abort system will work at max-Q via extensive computer analysis.
I personally don't agree with this approach, but that's what Boeing bid
and NASA accepted.

That would seem to require at least 2 test flights right?


Nope.

Jeff
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  #15  
Old June 27th 19, 02:05 PM posted to sci.space.policy
Greg \(Strider\) Moore
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"Jeff Findley" wrote in message
...

In article ,
says...
Yeah, I guess I didn't add the comment I thought I had, but I suspect

SpaceX
feels it's cheaper to do a live test because for them it's a fairly small
incremental cost (fuel and if there's overtime added to the workflow).
For
Boeing, it's a much steeper cost and they probably are comfortable enough
saying it's cheaper to do ground testing than "waste" a booster.

Wikipedia shows that test as scheduled for late July using a previously
flown booster, but I wonder if the abort test will destroy the booster.


The abort test will reportedly use an actual fueled upper stage but no
flight worthy Merlin vacuum engine. And from what I've read, SpaceX
does not believe that the booster will survive the test. Some reports
have said they don't even plan on trying to recover the booster.

So they're planning on expending an entire Falcon 9, minus one Merlin
vacuum engine, for this test. That's got to be hardware worth tens of
millions of dollars.


True, I had overlooked the cost of the upper stage! That is not a small
chunk of change, though without the engine, they're definitely saving some
money there.

As for the booster, yeah, assuming they can't recover it, it's a loss, but
still cheaper than ULA because they're both cheaper to start with and they
can afford to lose a re-used stage since in a sense it's already been paid
for.


Jeff


--
Greg D. Moore http://greenmountainsoftware.wordpress.com/
CEO QuiCR: Quick, Crowdsourced Responses. http://www.quicr.net
IT Disaster Response -
https://www.amazon.com/Disaster-Resp...dp/1484221834/

  #16  
Old June 27th 19, 03:54 PM posted to sci.space.policy
Niklas Holsti
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On 19-06-27 13:55 , Jeff Findley wrote:

The [SpaceX Dragon-2] abort test will reportedly use an actual fueled
upper stage but no flight worthy Merlin vacuum engine.


Do you have a link/reference for that? The descriptions I've found say
no upper stage, and only three Merlins on the first stage.

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  #17  
Old June 27th 19, 07:50 PM posted to sci.space.policy
Fred J. McCall[_3_]
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JF Mezei wrote on Thu, 27 Jun 2019
11:47:09 -0400:

On 2019-06-27 06:55, Jeff Findley wrote:

flight worthy Merlin vacuum engine. And from what I've read, SpaceX
does not believe that the booster will survive the test. Some reports
have said they don't even plan on trying to recover the booster.


Recovery would be interesting from a forensic point of view. at Max Q
altitude, are videos of the craft precise enough that recovering the
wreckage would not yield much info?


What info do you need?


Would it be correct to state that there are 2 scenarios where in-flight
capsule eject would be triggered:

-catastropic failure of lower stages. (eg: explosion)
-failure of guidance and stack headed for downtown Manhattan and capsule
gets to eject just before self destruct for stack is activated ?

In the second case, is there a choreography challenge to ensure the
ejected capsule doesn't end up colliding with the rocket that is still
under power until detonation?


No. The capsule accelerates away from the stack. That's sort of the
point.

So they're planning on expending an entire Falcon 9, minus one Merlin
vacuum engine, for this test. That's got to be hardware worth tens of
millions of dollars.


SpaceX undoubtedly has a "max re-use of X times" for Falcon 9s at this
point. (X may increase later on). If they have a rocket which has has
its X reached, it has no commercial value left and could be used for
such a test. And with such a test, help validate Faklcon9 for X+1 re-uses.


They have no such rockets. Nothing is anywhere near flight limits. I
suspect SpaceX chose this route because it's really the only way to
actually test it. Simulations are nice and all, but the data you get
from them is no better than the accuracy of the simulation.


--
"Some people get lost in thought because it's such unfamiliar
territory."
--G. Behn
  #18  
Old June 28th 19, 03:38 AM posted to sci.space.policy
Greg \(Strider\) Moore
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"JF Mezei" wrote in message ...


Say the stack explodes violenty.

On the pad, assuming capsule ejects at same time, one would hope that
its speed would at least match that of debris flying towards it so that
debris won't damage capsule. Right?


That's the ideal, yes.

After launch, would Max-W be the safest time from a debris point of view
because this is where debris would be slowed the most? Or would the
capsule eject at an equally slower speed and the risk is the same?


You are launching into Max-Q, so that's an issue.
But overall, the aerodynamics are tougher. At the pad level, there's no
real airflow so the capsule will mostly go where the rockets direct it (as
seen in SpaceX's pad abort test).
But at Max-Q, I suspect if you misjudge something, the airstream risks
causing a tumble or other issue.


Just curious if Max-Q is the most difficult/dangerous ejection solely
from the point of view of debris from explosion underneat hitting capsule?


Probably not, in part you've got a lot less fuel driving the explosion.
But the aerodynamics are trickier.



--
Greg D. Moore http://greenmountainsoftware.wordpress.com/
CEO QuiCR: Quick, Crowdsourced Responses. http://www.quicr.net
IT Disaster Response -
https://www.amazon.com/Disaster-Resp...dp/1484221834/

  #19  
Old June 28th 19, 12:13 PM posted to sci.space.policy
Jeff Findley[_6_]
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In article ,
lid says...

On 19-06-27 13:55 , Jeff Findley wrote:

The [SpaceX Dragon-2] abort test will reportedly use an actual fueled
upper stage but no flight worthy Merlin vacuum engine.


Do you have a link/reference for that? The descriptions I've found say
no upper stage, and only three Merlins on the first stage.


This isn't a very recent article, but it's based on a document submitted
to the FAA for the test, so I'm betting it's as accurate as we're going
to get before the actual test.

How SpaceX Will Conduct an Inflight Abort Test for Crew Dragon
November 28, 2018 Doug Messier
http://www.parabolicarc.com/2018/11/...duct-inflight-
abort-test-crew-dragon/

From above (which I believe are excerpts from the document submitted to
the FAA:

The booster would include nine M1D engines and be configured to
perform an ascent abort shutdown. Each engine is propelled by
liquid oxygen (LOX) and rocket fuel (RP-1; highly refined form
of kerosene) and produces 190,000 pounds of thrust at sea level
(for a total of 1.71 million pounds of thrust from all nine
engines). The booster would carry the standard set of flight
instrumentation.

The second stage would be a standard Falcon 9 second stage,
with the exception of the M1D vacuum engine. The components
essential to propellant loading operations would be carried,
but the thrust chamber, turbopump, thrust vector control
actuators, and other components required for performing second
stage burns, would be omitted, as the mission concludes part-
way through the first stage ascent burn. Propellant loading
would follow standard loading operations for the second stage.

So, this sounds like a very high fidelity test. Very little would be
different from this Falcon 9 and a Falcon 9 used to launch Dragon 2 to
ISS.

Jeff
--
All opinions posted by me on Usenet News are mine, and mine alone.
These posts do not reflect the opinions of my family, friends,
employer, or any organization that I am a member of.
  #20  
Old June 28th 19, 12:18 PM posted to sci.space.policy
Jeff Findley[_6_]
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In article ,
says...

Say the stack explodes violenty.


The kerosene and LOX will burn, but there won't technically be an
explosion because the kerosene and LOX will not much have time to mix
before burning.

On the pad, assuming capsule ejects at same time, one would hope that
its speed would at least match that of debris flying towards it so that
debris won't damage capsule. Right?


The escape system on any capsule is designed to keep the capsule ahead
of any debris. You design for the "worst case scenario". Which for
capsules, would be Orion's abort motor which has to be able to pull it
away from a five segment SRB that's had a case rupture. This is a far
worse scenario than any liquid fueled launch vehicle incident.

After launch, would Max-W be the safest time from a debris point of view
because this is where debris would be slowed the most? Or would the
capsule eject at an equally slower speed and the risk is the same?


WTF is "Max-W"?

Just curious if Max-Q is the most difficult/dangerous ejection solely
from the point of view of debris from explosion underneat hitting capsule?


Max-Q is difficult because the abort system has to "fight" the maximum
aerodynamic pressure which causes drag on the capsule. Max-Q difficulty
has nothing to do with the debris from the breakup of the booster
underneath.

Jeff
--
All opinions posted by me on Usenet News are mine, and mine alone.
These posts do not reflect the opinions of my family, friends,
employer, or any organization that I am a member of.
 




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