Author Topic: SpaceX Falcon 9/Dragon CRS-3 (SpX-3) MISSION GENERAL DISCUSSION  (Read 719028 times)

Offline anik

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DISCUSSION THREAD FOR CRS-3 (SpX-3).

ALL POSTS MUST BE ON TOPIC OR THEY WILL BE REMOVED WITHOUT NOTICE FOR HOUSEKEEPING PURPOSES.

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http://www.nasa.gov/missions/highlights/schedule.html

Date: November 11
Mission: SpaceX 3 Commercial Resupply Services flight
Launch Vehicle: Falcon 9
Launch Site: Cape Canaveral Air Force Station, Fla.
Launch Pad: Space Launch Complex 40
Description: SpaceX 3 will be the third commercial resupply mission to the International Space Station by Space Exploration Technologies (SpaceX).

==

Resources:

Other threads for SpX-3:
SpaceX Falcon 9/Dragon CRS-3 SpX-3 PROCESSING/Pre-LAUNCH UPDATES
SCRUB: SpaceX Falcon 9 v1.1 - CRS-3 Dragon - ATTEMPT 1 UPDATES
SpaceX Falcon 9 v1.1 - CRS-3 Dragon - ATTEMPT 2 UPDATES
SpaceX CRS-3 Dragon - RNDZ, Berthing, ISS Ops - UPDATES
SpaceX Dragon CRS-3 (SpX-3) EOM (Unberth, Entry, Splashdown) UPDATES
SpaceX Falcon 9/Dragon CRS-3 SpX-3 PAYLOADS
The CRS-3/SpX-3 - Dragon, Suit Up! - Party Thread
Poll: What will the eventual fate of the CRS-3 first stage be?

SpaceX GENERAL Forum Section:
http://forum.nasaspaceflight.com/index.php?board=45.0 - please use this for general questions NOT specific to SpX-2.

SpaceX MISSIONS Forum Section:
http://forum.nasaspaceflight.com/index.php?board=55.0 - this section is for everything specific to SpaceX missions.

SpaceX News Articles from 2006 (Including numerous exclusive Elon interviews):
http://forum.nasaspaceflight.com/index.php?topic=21862.0

SpaceX News Articles (Recent):
http://www.nasaspaceflight.com/tag/spacex/

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Main Articles for the previous mission, CRS-2:

SpaceX Dragon to make third ISS visit amid logistics schedule challenges - by Pete Harding:
http://www.nasaspaceflight.com/2013/02/dragon-third-visit-logistics-schedule-challenges/

CRS-2: Dragonís tantrum subdued following Falcon 9 launch - by William Graham (update by me):
http://www.nasaspaceflight.com/2013/03/spacex-milestone-falcon9-launch-dragon-crs2/

Resilient CRS-2 Dragon in pursuit of ISS for Sunday berthing:
http://www.nasaspaceflight.com/2013/03/resilient-crs-2-dragon-pursuit-iss-sunday-berthing/

SSRMS removes payload from Dragon trunk to mark new milestone:
http://www.nasaspaceflight.com/2013/03/ssrms-removes-payload-dragon-trunk-new-milestone/

CRS-2 Dragon homecoming delayed due to high seas in the splashdown zone:
http://www.nasaspaceflight.com/2013/03/dragon-homecoming-delayed-high-seas-splashdown-zone/

EOM Article:
http://www.nasaspaceflight.com/2013/03/spacexs-crs-2-dragon-iss-departure-splashdown/

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L2 SpaceX Section:
http://forum.nasaspaceflight.com/index.php?action=tags&tags=SpaceX

L2 SpaceX Dragon Special Section (Exclusively acquired pre-launch and Mission Coverage, Presentations, Graphics, Videos, Updates and tons of unreleased hi res photos from the mission...and also a lot less noise than the busy open forum SpaceX sections):
http://forum.nasaspaceflight.com/index.php?board=60.0

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« Last Edit: 08/08/2017 10:16 PM by gongora »

Online mto

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AviationWeek (link)

"SpaceX envisions an initial test of the upgraded Falcon 9 first stageís ďfly backĒ capabilities later this year as part of the third International Space Station Dragon mission launched under the companyís NASA Commercial Resupply Services (CRS) agreement, CEO and chief designer Elon Musk told a March 28 teleconference.

The Hawthorne, Calif.-based launch services provider will attempt a propulsively controlled landing in the Atlantic Ocean following the launch of a mission from Cape Canaveral Air Force Station, Fla., tentatively set for late September. ..."

Offline mlindner

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AviationWeek (link)

"SpaceX envisions an initial test of the upgraded Falcon 9 first stage’s “fly back” capabilities later this year as part of the third International Space Station Dragon mission launched under the company’s NASA Commercial Resupply Services (CRS) agreement, CEO and chief designer Elon Musk told a March 28 teleconference.

The Hawthorne, Calif.-based launch services provider will attempt a propulsively controlled landing in the Atlantic Ocean following the launch of a mission from Cape Canaveral Air Force Station, Fla., tentatively set for late September. ..."

AviationWeek got its dates wrong. It was mid next year for fly back. Also they said that SpaceX is waiting till the next CRS flight to test the water landing, they got that wrong too. They also claimed they "elected to skip a test" that would have found the problem with the valve... That sounds like AviationWeek is trying to spin things differently than what was said. There was no test skipping done.
« Last Edit: 04/01/2013 11:14 PM by mlindner »
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Online mto

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... AviationWeek got its dates wrong. It was mid next year for fly back. Also they said that SpaceX is waiting till the next CRS flight to test the water landing, they got that wrong too.
From parabolicarc.com (link)

"Q. When is next CRS launch?

Shotwell: CRS 3 launch late this fall. A number of upgrades to the Dragon configuration that will enable better critical cargo to be sent and returned.

Musk: Will include upgraded Falcon 9. Could increase the useful payload of Dragon by several tons. As much as you could pack into Dragon.

Will attempt to recover the first stage.

ďAs I said before, I think it will take us several flights before we are successful in that.Ē"

Offline krytek

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Any ramifications of Falcon v1.1 on the instantaneous launch window?

Offline ArbitraryConstant

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Any ramifications of Falcon v1.1 on the instantaneous launch window?
One would assume that they will be volume limited and therefore have considerably more margin to work with.

Offline docmordrid

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ISTM the F9 v1.1 would better handle a loaded up extended trunk.
DM

Offline MP99

They also claimed they "elected to skip a test" that would have found the problem with the valve... That sounds like AviationWeek is trying to spin things differently than what was said. There was no test skipping done.

Musk has said that more thorough testing would have found the problem (link):-
Quote
Musk: It was a tiny design revision change from the supplier. The supplier made some mistakes and we didnít catch those mistakes. Ran system through low pressurization tests, but didnít run them through the high presssurization functionality tests. Didnít get stuck in the low pressurization functionality tests. Make sure we donít repeat that in the future. Need a magnifying glass to see the difference.
(My highlight)

[Edit: Musk seems to be implying (but hard to be certain) that they didn't put the valve through a full suite of tests (inc high pressure) because the supplier didn't tell them of the design change.

If that reading is correct, it perhaps implies that the low-pressure tests are part of standard Dragon testing. Perhaps they avoid high-pressure tests to avoid putting too much lifetime on the components, IE trying to avoid an end-of-life issue like the M1C fail on SpX-1.]

cheers, Martin
« Last Edit: 04/02/2013 06:56 AM by MP99 »

Offline ugordan

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IE trying to avoid an end-of-life issue like the M1C fail on SpX-1.]

Except that turned out to not be an end-of-life issue.

Online JBF

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They also claimed they "elected to skip a test" that would have found the problem with the valve... That sounds like AviationWeek is trying to spin things differently than what was said. There was no test skipping done.

Musk has said that more thorough testing would have found the problem (link):-
Quote
Musk: It was a tiny design revision change from the supplier. The supplier made some mistakes and we didnít catch those mistakes. Ran system through low pressurization tests, but didnít run them through the high presssurization functionality tests. Didnít get stuck in the low pressurization functionality tests. Make sure we donít repeat that in the future. Need a magnifying glass to see the difference.
(My highlight)

[Edit: Musk seems to be implying (but hard to be certain) that they didn't put the valve through a full suite of tests (inc high pressure) because the supplier didn't tell them of the design change.

If that reading is correct, it perhaps implies that the low-pressure tests are part of standard Dragon testing. Perhaps they avoid high-pressure tests to avoid putting too much lifetime on the components, IE trying to avoid an end-of-life issue like the M1C fail on SpX-1.]

cheers, Martin

Generally you have one set of stringent tests to qualify a new product and then an easier set of tests to verify functionality for a production run.
"In principle, rocket engines are simple, but thatís the last place rocket engines are ever simple." Jeff Bezos

Offline MP99

They also claimed they "elected to skip a test" that would have found the problem with the valve... That sounds like AviationWeek is trying to spin things differently than what was said. There was no test skipping done.

Musk has said that more thorough testing would have found the problem (link):-
Quote
Musk: It was a tiny design revision change from the supplier. The supplier made some mistakes and we didnít catch those mistakes. Ran system through low pressurization tests, but didnít run them through the high presssurization functionality tests. Didnít get stuck in the low pressurization functionality tests. Make sure we donít repeat that in the future. Need a magnifying glass to see the difference.
(My highlight)

[Edit: Musk seems to be implying (but hard to be certain) that they didn't put the valve through a full suite of tests (inc high pressure) because the supplier didn't tell them of the design change.

If that reading is correct, it perhaps implies that the low-pressure tests are part of standard Dragon testing. Perhaps they avoid high-pressure tests to avoid putting too much lifetime on the components, IE trying to avoid an end-of-life issue like the M1C fail on SpX-1.]

cheers, Martin

There is a quote here regarding the supplier change.

Quote
SpaceX was not made aware of the design change by its supplier, and while companyís engineers conducted a pre-mission low-pressure functionality test of the hardware, they elected to skip a high-pressure test that might have revealed the problem, he said.

Note that this isn't really an SpX-3 issue (except insofar as they'll test to ensure this doesn't happen again), and the referenced thread should be directly related to SpX-2 Updates rather than discussion - so also not ideal to continue this.

cheers, Martin

Offline Kabloona

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[Edit: Musk seems to be implying (but hard to be certain) that they didn't put the valve through a full suite of tests (inc high pressure) because the supplier didn't tell them of the design change.

cheers, Martin

I don't think that's what he implied. What he implied is that the RCS pressurization susbsystem is routinely tested after assembly at low pressure, not high pressure. Remember, this is a test that would have been done on the fully assembled system, after the vendor had (presumably) run acceptance tests on the individual components (like the check valves) at their full rated pressures.

Any spacecraft pressurization subsystem like this one, consisting of pressurant tanks, lines, valves, etc, is normally leak tested after assembly, and one way you can do a leak check is to pressure the system with Helium and then use a very sensitive Helium detector to sniff for leaks. A low-pressure test is usually sufficient for leak detection. And since you have to pressurize the system to check for leaks, you may as well do whatever functional checks you can do at the same time.

Since check valves are such simple, highly reliable components, you just assume that a check valve that has already passed acceptance tests will work. It simply wouldn't occur to a mechanical engineer who designed the system that, hey, this check valve that opened at low pressure might *not* open at its design, rated, acceptance-tested pressure. And that assumption, which has held true in possibly every aerospace pressurization system ever built, held true until this one bizarre event.

So, yes, every Dragon RCS system would normally be subjected to a low-pressure leak/functionality test. Obviously, that will now be a high-pressure test.

This is merely my interpretation of events based in what Elon said and my modest experience with RCS propulsion systems assembly and test protocol.
« Last Edit: 04/02/2013 10:35 PM by Kabloona »

Online Robotbeat

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Check valves are not always so reliable. I've heard anecdotes of rocket folks who kind of hate them since they can be glitchy compared to other valves (though other valves are often not suitable). I looked for a source for this anecdote but could not locate it.
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Offline Kabloona

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Check valves are not always so reliable. I've heard anecdotes of rocket folks who kind of hate them since they can be glitchy compared to other valves (though other valves are often not suitable). I looked for a source for this anecdote but could not locate it.

The original question was why the system test was done at low pressure instead of at high pressure, and my point was that if a check valve opens at low pressure, there's no reason to think it won't open at high pressure, especially when (a) it was *designed* for that high pressure, and (b) it has already (presumably) been acceptance tested at the vendor. So if you're SpaceX doing a pressure test on the assembled system, it's perfectly logical for you to do the test at low pressure.

As for check valve failures, the usual failure modes are stuck open or stuck closed, and again, the check valves in question opened during the low pressure system test, but apparently the vendor's design change meant that the next pressure cycle caused the valve to stick closed. So what's strange in this case is not a *random* failure but a subtle design change that didn't prevent the valve from working normally in qual or acceptance tests, but prevented the valve from opening after a system-level test at low pressure in which the valve *did* open normally.

Offline beancounter

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Check valves are not always so reliable. I've heard anecdotes of rocket folks who kind of hate them since they can be glitchy compared to other valves (though other valves are often not suitable). I looked for a source for this anecdote but could not locate it.

The original question was why the system test was done at low pressure instead of at high pressure, and my point was that if a check valve opens at low pressure, there's no reason to think it won't open at high pressure, especially when (a) it was *designed* for that high pressure, and (b) it has already (presumably) been acceptance tested at the vendor. So if you're SpaceX doing a pressure test on the assembled system, it's perfectly logical for you to do the test at low pressure.

As for check valve failures, the usual failure modes are stuck open or stuck closed, and again, the check valves in question opened during the low pressure system test, but apparently the vendor's design change meant that the next pressure cycle caused the valve to stick closed. So what's strange in this case is not a *random* failure but a subtle design change that didn't prevent the valve from working normally in qual or acceptance tests, but prevented the valve from opening after a system-level test at low pressure in which the valve *did* open normally.
Yes that's my understanding as well.

IIRC, one of the MERs Delta II vehicles had a check valve issue prior to launch and the launch team cycled the valves several times to get them working properly, then they launched.  Doesn't seem to be an uncommon occurance.
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Offline Jim

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IIRC, one of the MERs Delta II vehicles had a check valve issue prior to launch and the launch team cycled the valves several times to get them working properly, then they launched.  Doesn't seem to be an uncommon occurance.


It was the LOX fill and drain valve.  No where close to the same thing

Offline beancounter

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IIRC, one of the MERs Delta II vehicles had a check valve issue prior to launch and the launch team cycled the valves several times to get them working properly, then they launched.  Doesn't seem to be an uncommon occurance.


It was the LOX fill and drain valve.  No where close to the same thing
Ok thanks for the correction. 
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Offline Joffan

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Meanwhile back on SpX-3 ... I notice that the initial (post SpX-2) date for SpX-3 launch moved quickly up by a couple of weeks to currently be at November 11. Could that be moved up further, and do we have any ideas about what the selection factors are for that date? NASA requirements vs SpaceX readiness etc.

Mostly I admit I'd like to see the Dragon get up to ISS again before Expedition 37 closes - which would only require it to shift up another week.
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Online Comga

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anik's updated schedule has SpX-3 launching on November 11.  (Added on March 26, date changed on March 30)
If anik posts it, I believe it.  His posted date for SpX-2 was accurate and stood for five months before launch.
We should use "Nov-11" to update the thread title.

edit: correct silly typos
« Last Edit: 04/04/2013 05:25 AM by Comga »
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Offline Jason1701

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anik's updated schedule has SpX-3 launching on November 11.  (Added on March 26, date changed on March 30)
If anik posts it, I believe it.  His posted date for SpX-2 was accurate and stood for five months before launch.
We should use "Nov-11" to update the thread title.

edit: correct silly typos

How does anik find out about that?

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