Commercial Crew

In article ,
says...

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?

It remains to be seen if they'll try to fish the pieces out of the
water, but an intact recovery of the booster isn't in the cards
according to documents submitted by SpaceX to the FAA last year.

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?

That case is easier because the first stage engines would surely be
commanded to shut down as part of the abort sequence. This is an
advantage of liquid fueled engines over solids.

Orion would have a harder time with its abort system because "shutting
down" solids means firing the destruct charges to "unzipper" them along
their length, releasing all of the pressure that's inside the burning
SRB. That's why the abort motor for Orion is fracking huge.

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.

Falcon 9 Block 5 first stages are designed for something like 100
flights. There are no Falcon 9 Block 5 first stages with 99 flights on
them.

Jeff

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In article ,
says...

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.

This. I honestly don't know why NASA agreed to let Boeing only simulate
a max-Q escape with its Starliner capsule. IMHO, this is a case where
you really want a real world test. Orion will do a max-Q abort, so if
NASA doesn't trust Orion to a simulation, why trust Starliner to the
same?

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.

On 19-06-28 14:13 , Jeff Findley wrote:
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/

Many thanks, Jeff, that does seem authoritative.

So, this sounds like a very high fidelity test.

Yep, largely so. But it seems they intend to shut down the first-stage
engines at the time of the abort, so the booster will not try to catch
up with the capsule after the capsule separates. Still, I guess the
capsule's acceleration would win anyway.

--
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
. @ .

Jeff Findley wrote on Fri, 28 Jun 2019
07:23:56 -0400:


Falcon 9 Block 5 first stages are designed for something like 100
flights. There are no Falcon 9 Block 5 first stages with 99 flights on
them.


The one thought that occurs to me (and I don't think the description
you posted of the test assets makes it clear) is that perhaps they are
NOT using a Block 5 booster set, but rather an earlier set that isn't
intended for a lot of reflights.


--
"The reasonable man adapts himself to the world; the unreasonable
man persists in trying to adapt the world to himself. Therefore,
all progress depends on the unreasonable man."
--George Bernard Shaw

Niklas Holsti wrote on Fri, 28 Jun
2019 18:54:30 +0300:

On 19-06-28 14:13 , Jeff Findley wrote:
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/

Many thanks, Jeff, that does seem authoritative.

So, this sounds like a very high fidelity test.

Yep, largely so. But it seems they intend to shut down the first-stage
engines at the time of the abort, so the booster will not try to catch
up with the capsule after the capsule separates. Still, I guess the
capsule's acceleration would win anyway.


If the abort test is at Max Q I don't think this makes any difference
anyway, since you're not really 'accelerating' at Max Q. And wouldn't
part of the 'normal' abort sequence shut down the booster anyhow?


--
"Insisting on perfect safety is for people who don't have the balls to
live in the real world."
-- Mary Shafer, NASA Dryden

On 19-06-28 19:25 , Fred J. McCall wrote:
Niklas Holsti wrote on Fri, 28 Jun
2019 18:54:30 +0300:

On 19-06-28 14:13 , Jeff Findley wrote:
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/

Many thanks, Jeff, that does seem authoritative.

So, this sounds like a very high fidelity test.

Yep, largely so. But it seems they intend to shut down the first-stage
engines at the time of the abort, so the booster will not try to catch
up with the capsule after the capsule separates. Still, I guess the
capsule's acceleration would win anyway.


If the abort test is at Max Q I don't think this makes any difference
anyway, since you're not really 'accelerating' at Max Q.

I don't recall seeing any pause, at Max Q, in the growth rate of the
Falcon 9 "velocity" reading in the numerous Falcon 9 launch videos I've
watched, so I find it hard to believe that the vehicle stops
accelerating at that point. Also, wouldn't such a constant-speed flight
segment increase the gravity losses?

And wouldn't
part of the 'normal' abort sequence shut down the booster anyhow?

It should, but an abort occurs when there is an anomaly, so it might not
work.

--
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
. @ .

Niklas Holsti wrote on Fri, 28 Jun
2019 22:44:30 +0300:

On 19-06-28 19:25 , Fred J. McCall wrote:
Niklas Holsti wrote on Fri, 28 Jun
2019 18:54:30 +0300:

On 19-06-28 14:13 , Jeff Findley wrote:
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/

Many thanks, Jeff, that does seem authoritative.

So, this sounds like a very high fidelity test.

Yep, largely so. But it seems they intend to shut down the first-stage
engines at the time of the abort, so the booster will not try to catch
up with the capsule after the capsule separates. Still, I guess the
capsule's acceleration would win anyway.


If the abort test is at Max Q I don't think this makes any difference
anyway, since you're not really 'accelerating' at Max Q.

I don't recall seeing any pause, at Max Q, in the growth rate of the
Falcon 9 "velocity" reading in the numerous Falcon 9 launch videos I've
watched, so I find it hard to believe that the vehicle stops
accelerating at that point.


https://space.stackexchange.com/ques...y-after-launch


Also, wouldn't such a constant-speed flight
segment increase the gravity losses?


Not nearly as much as having the vehicle disintegrate due to
aerodynamic stress would.

And wouldn't
part of the 'normal' abort sequence shut down the booster anyhow?

It should, but an abort occurs when there is an anomaly, so it might not
work.


These are liquid fuel rockets. It's not like they're difficult to
throttle down. You might as well postulate that payload separation
will fail at that point.


--
"Insisting on perfect safety is for people who don't have the balls to
live in the real world."
-- Mary Shafer, NASA Dryden

In message
Jeff Findley wrote:

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.

The Dragon on CRS-7 survived the disintegration of the second stage of
the Falcon 9 just fine without any kind of abort system firing. It
didn't survive hitting the ocean a few minutes later, but software has
been tweaked to enable the parachutes should anything similar happen
again.

Anthony

On 19-06-29 07:25 , Fred J. McCall wrote:
Niklas Holsti wrote on Fri, 28 Jun
2019 22:44:30 +0300:

On 19-06-28 19:25 , Fred J. McCall wrote:

If the abort test is at Max Q I don't think this makes any
difference anyway, since you're not really 'accelerating' at Max
Q.

I don't recall seeing any pause, at Max Q, in the growth rate of
the Falcon 9 "velocity" reading in the numerous Falcon 9 launch
videos I've watched, so I find it hard to believe that the vehicle
stops accelerating at that point.


https://space.stackexchange.com/ques...y-after-launch

The acceleration graph shown there for CRS/Dragon missions never falls
below about 0.53 g, so it is indeed still accelerating at Max Q. From
the behaviour before and after Max Q it seems that without the
throttle-down for Max Q the acceleration at that altitude would still be
less than 1 g, so the throttle-down cuts acceleration in half, but not
more than that.

--
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
. @ .

In article ,
says...

Jeff Findley wrote on Fri, 28 Jun 2019
07:23:56 -0400:


Falcon 9 Block 5 first stages are designed for something like 100
flights. There are no Falcon 9 Block 5 first stages with 99 flights on
them.


The one thought that occurs to me (and I don't think the description
you posted of the test assets makes it clear) is that perhaps they are
NOT using a Block 5 booster set, but rather an earlier set that isn't
intended for a lot of reflights.

That would certainly be possible, but it wouldn't be as high fidelity as
a Block 5. According to NexxusWolf on Reddit, it will be a Block 5
booster. Yes, I know, not the most reliable spot for info, but it is
what it is.

https://www.reddit.com/r/spacex/comm...at_i_got_from_
my_tour/

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.