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SpaceX just did a full duration test firing of a recovered 1st stage



 
 
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  #11  
Old July 31st 16, 03:17 PM posted to sci.space.policy
Vaughn Simon
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Default SpaceX just did a full duration test firing of a recovered 1ststage

On 7/30/2016 11:24 PM, JF Mezei wrote:
The other aspect would be the number of times the LOX tank can be loaded
and emptied before structural issues surface.


I have also pondered that, but those tanks are clearly designed to be
loaded/cycled many times. Each Falcon 9 lox tank goes through at least
two cycles per launch, and sometimes (with scrubs etc.) several times
before it actually launches. Other launch systems historically do the
same.

Offhand, I don't recall any launch provider ever mentioning concern over
multiple lox tank cycles pre-launch. Has anyone else?
  #12  
Old July 31st 16, 03:26 PM posted to sci.space.policy
Jeff Findley[_6_]
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Default SpaceX just did a full duration test firing of a recovered 1st stage

In article om,
says...

On 2016-07-29 06:25, Jeff Findley wrote:

Saw the Tweet last night, with video, of a full duration test firing of
a recovered Falcon 9 first stage at their McGregor, Texas facility. I'm
sure there will be stories on the space news websites today.



In the history of space flight, have only Shuttle SSMEs been recovered
from flight and test fired again ?


Depends how many qualifiers you put on it. If you limit it to engines
originally used on an orbital launch I believe the answer is yes. Of
course test vehicles and test articles have done this or simulated this
in the past. For non-orbital examples there were all of the rocket
powered X planes X-1, ... X-15. For VTVL there was the DC-X/XA. There
was also a test of a simulated recovery of an engine which included a
test firing of the engine, but I can't seem to find it again via Google.
Perhaps it was a Boeing test using an SSME parachuted into the water?

My guess is that SpaceX needs to ascertain if having an actual flight
and landing creates identical conditions to test firings on ground, or
whether the cold of space and impact of landing create any unforeseen
problems.


Which is why they're testing one that was actually flown on an orbital
mission rather than one "new" from the factory.

The other aspect would be the number of times the LOX tank can be loaded
and emptied before structural issues surface.


Yup. Sub-cooled LOX will subject the tanks and plumbing to thermal
cycling. For example, even though the space shuttle ET was expendable,
it was still spec'd for so many fill and drains (for test firings,
aborted launches, and etc.) due to thermal cycling.

I assume that by now, SpaceX has developped criteria/tests that need to
met before a stage can be re-used.


Surely the engineering analysis for this was done long ago.

I wonder how many recovered stages they will test/examine before
releasing one for re-flight.


They plan on re-flying one this fall. It's my understanding that this
"life leader" is verifying their engineering analysis via testing. It's
never a bad idea to verify analyses via testing.

Jeff
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These posts do not reflect the opinions of my family, friends,
employer, or any organization that I am a member of.
  #13  
Old July 31st 16, 03:52 PM posted to sci.space.policy
Jeff Findley[_6_]
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Posts: 2,307
Default SpaceX just did a full duration test firing of a recovered 1st stage

In article ,
says...

In article om,
says...

On 2016-07-29 06:25, Jeff Findley wrote:

Saw the Tweet last night, with video, of a full duration test firing of
a recovered Falcon 9 first stage at their McGregor, Texas facility. I'm
sure there will be stories on the space news websites today.



In the history of space flight, have only Shuttle SSMEs been recovered
from flight and test fired again ?


Depends how many qualifiers you put on it. If you limit it to engines
originally used on an orbital launch I believe the answer is yes. Of
course test vehicles and test articles have done this or simulated this
in the past. For non-orbital examples there were all of the rocket
powered X planes X-1, ... X-15. For VTVL there was the DC-X/XA. There
was also a test of a simulated recovery of an engine which included a
test firing of the engine, but I can't seem to find it again via Google.
Perhaps it was a Boeing test using an SSME parachuted into the water?


Sorry for replying to myself, but here is a short blog post by Scott
Lowther on a sea water dunk test done with the H-1 as part of an
investigation into reusing the engines from the Saturn I/IB.

H-1 reusability: Bad photos of lost awesome
http://up-ship.com/blog/?p=5948


A detailed paper on parachute recovery with a picture of exactly what I
was thinking of. It's a test a reentry vehicle with a single SSME in
the center being tested as part of the an EELV proposal (figure 11, on
page 8).

http://www.airborne-sys.com/files/pd...-2005-1624.pdf

AIAA paper: "Recovery system for the evolved expendable launch vehicle"
http://arc.aiaa.org/doi/abs/10.2514/6.1997-1513

Makes one wonder if a LOX/hydrogen EELV first stage which reused the
main engine (SSME) would have been cheaper than the Delta IV first stage
with expendable engine (RS-68 if memory serves).


It's worth noting that pretty much every liquid fueled rocket engine is
reusable in practice, since nearly all of them are test fired before
being used on a launch vehicle. Yes, the devil is in the details, but
there is absolutely nothing fundamental about the engine itself that
makes it "expendable".

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.
  #14  
Old July 31st 16, 05:11 PM posted to sci.space.policy
Bob Haller
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Default SpaceX just did a full duration test firing of a recovered 1st stage

On Sunday, July 31, 2016 at 10:17:14 AM UTC-4, Vaughn Simon wrote:
On 7/30/2016 11:24 PM, JF Mezei wrote:
The other aspect would be the number of times the LOX tank can be loaded
and emptied before structural issues surface.


I have also pondered that, but those tanks are clearly designed to be
loaded/cycled many times. Each Falcon 9 lox tank goes through at least
two cycles per launch, and sometimes (with scrubs etc.) several times
before it actually launches. Other launch systems historically do the
same.

Offhand, I don't recall any launch provider ever mentioning concern over
multiple lox tank cycles pre-launch. Has anyone else?


there were limits on the shuttle external fuel tank, it was mentioned after a bunch of scrubs
  #15  
Old July 31st 16, 07:50 PM posted to sci.space.policy
Bob Haller
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Posts: 3,197
Default SpaceX just did a full duration test firing of a recovered 1st stage

On Sunday, July 31, 2016 at 1:48:33 PM UTC-4, JF Mezei wrote:
On 2016-07-31 10:17, Vaughn Simon wrote:

I have also pondered that, but those tanks are clearly designed to be
loaded/cycled many times. Each Falcon 9 lox tank goes through at least
two cycles per launch, and sometimes (with scrubs etc.) several times
before it actually launches.



I wonder if LOX cycle times will end up being limits on how many times a
stage can be re-used. (aka: a scrub would reduce re-usability of that
stage because of an extra load/unload cycle.).

Some stage1s may end up being re-used more often than others depending
on how lucky they are at the pad with launch aborts/scrubs.


the tanks could be designed, upgrade to withstand more cycles. at some point it will be cheaper to accept whats available.

thats a good thing, the reflown booster s can be used as displays at some point.

hopefully indoors out of the weather. how badly the left over saturn 5 boosters were treated still bugs me today.

although they were eventually stabilized and fixed up a bit.
  #16  
Old August 1st 16, 06:19 PM posted to sci.space.policy
Rick Jones[_6_]
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Posts: 106
Default SpaceX just did a full duration test firing of a recovered 1st stage

Jeff Findley wrote:
From what I've read, this stage will be the "life leader", which
would imply that they're going to fill, fire, and inspect it many
times to gather hard data to help determine just how many times a
Falcon 9 first stage can successfully be reused.


I suppose even one "actual" launch of the stage is not too far from
crossing the Rubicon, but why wait for a successfully returned stage
to do this testing? I suppose "Waste anything but time" doesn't
really apply to SpaceX, but it would seem that they could have been
rather further along on answering the question of "How many times can
we reuse a stage?" via repeated test firings on the ground by just
starting that process with a stage many months ago.

rick jones
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The glass is neither half-empty nor half-full. The glass has a leak.
The real question is "Can it be patched?"
these opinions are mine, all mine; HPE might not want them anyway...
feel free to post, OR email to rick.jones2 in hpe.com but NOT BOTH...
  #17  
Old August 1st 16, 11:34 PM posted to sci.space.policy
Jeff Findley[_6_]
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Posts: 2,307
Default SpaceX just did a full duration test firing of a recovered 1st stage

In article , says...

Jeff Findley wrote:
From what I've read, this stage will be the "life leader", which
would imply that they're going to fill, fire, and inspect it many
times to gather hard data to help determine just how many times a
Falcon 9 first stage can successfully be reused.


I suppose even one "actual" launch of the stage is not too far from
crossing the Rubicon, but why wait for a successfully returned stage
to do this testing? I suppose "Waste anything but time" doesn't
really apply to SpaceX, but it would seem that they could have been
rather further along on answering the question of "How many times can
we reuse a stage?" via repeated test firings on the ground by just
starting that process with a stage many months ago.


Except ground testing will never exactly replicate the conditions the
stage experiences during hypersonic reentry. Doing this testing with a
flown stage gives more confidence that a flown stage can be successfully
reflown.

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.
  #18  
Old August 2nd 16, 12:06 AM posted to sci.space.policy
Rick Jones[_6_]
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Posts: 106
Default SpaceX just did a full duration test firing of a recovered 1st stage

Jeff Findley wrote:
In article , says...
I suppose even one "actual" launch of the stage is not too far
from crossing the Rubicon, but why wait for a successfully
returned stage to do this testing? I suppose "Waste anything but
time" doesn't really apply to SpaceX, but it would seem that they
could have been rather further along on answering the question of
"How many times can we reuse a stage?" via repeated test firings
on the ground by just starting that process with a stage many
months ago.


Except ground testing will never exactly replicate the conditions
the stage experiences during hypersonic reentry. Doing this testing
with a flown stage gives more confidence that a flown stage can be
successfully reflown.


But will they really learn that much more from N (greater than one or
two as you implied from "life leader") iterations of "fill, fire and
inspect" on the ground from a stage which has been launched only once
than from one that wasn't launched? That is what I'm trying to get
at. Odds of landing success notwithstanding, I'd think they'd want to
put a dummy mass on the thing to simulate the second stage and
actually launch N times. True, an actual launch and recovery is going
to be more expensive than a static fire, but as you say, ground
testing will never exactly replicate the conditions the stage
experiences during hypersonic re-entry. And it isn't clear to me how
much more realistic ground testing becomes after say the first
post-recovery static for a stage that has been launched once than
those 2-3rd through Nth static fires would be on a stage that hasn't
been launched. One or two static fires of an already launched stage
seems reasonable, but after the second post-recovery static fire I
wonder whether the testing is assymptoticaly (sp) any different than a
never flown stage.

rick
--
a wide gulf separates "what if" from "if only"
these opinions are mine, all mine; HPE might not want them anyway...
feel free to post, OR email to rick.jones2 in hpe.com but NOT BOTH...
  #19  
Old August 2nd 16, 01:35 AM posted to sci.space.policy
Jeff Findley[_6_]
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Posts: 2,307
Default SpaceX just did a full duration test firing of a recovered 1st stage

In article , says...

Jeff Findley wrote:
Except ground testing will never exactly replicate the conditions
the stage experiences during hypersonic reentry. Doing this testing
with a flown stage gives more confidence that a flown stage can be
successfully reflown.


But will they really learn that much more from N (greater than one or
two as you implied from "life leader") iterations of "fill, fire and
inspect" on the ground from a stage which has been launched only once
than from one that wasn't launched? That is what I'm trying to get
at. Odds of landing success notwithstanding, I'd think they'd want to
put a dummy mass on the thing to simulate the second stage and
actually launch N times. True, an actual launch and recovery is going
to be more expensive than a static fire, but as you say, ground
testing will never exactly replicate the conditions the stage
experiences during hypersonic re-entry. And it isn't clear to me how
much more realistic ground testing becomes after say the first
post-recovery static for a stage that has been launched once than
those 2-3rd through Nth static fires would be on a stage that hasn't
been launched. One or two static fires of an already launched stage
seems reasonable, but after the second post-recovery static fire I
wonder whether the testing is assymptoticaly (sp) any different than a
never flown stage.


Good point. I'm sure doing the firings on a test stand are a
compromise. Similar to horizontal SRB test firings in place of actual
flight tests.

One advantage of ground tests may be the ability to collect more data.
But with today's miniaturized data collection equipment, I'd imagine you
could still instrument the heck out of a flight vehicle.

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 August 2nd 16, 02:28 AM posted to sci.space.policy
Vaughn Simon
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Posts: 55
Default SpaceX just did a full duration test firing of a recovered 1ststage

On 8/1/2016 7:06 PM, Rick Jones wrote:
But will they really learn that much more from N (greater than one or
two as you implied from "life leader") iterations of "fill, fire and
inspect" on the ground from a stage which has been launched only once
than from one that wasn't launched?


I get your point but... Given that they have several recovered boosters
now, why would they use a new one? And if they DID use a new one,
everyone would ask "why not a recovered one? What are they trying to hide?"

Also, I am sure that SpaceX has tested enough Merlin engines on their
test stands to have a very educated idea about their MTBF without even
bothering to test a recovered booster. IMO, Part of the point of this
present testing of a recovered booster surely is to convince customers
and underwriters that pre-used boosters can be a safe bet.

In other words, it's not just science and engineering that's happening
here, it's also a public relations and sales campaign. Which is why I
wonder why it took them so long to start it.
 




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