Author Topic: The SpaceX Scrubs thread  (Read 121470 times)

Online cartman

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Re: The SpaceX Scrubs thread
« Reply #20 on: 01/07/2015 12:48 AM »
I have added some delays as well, I think the ones we can track better are those that happened after the first static fire attempt.

Offline savuporo

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Re: The SpaceX Scrubs thread
« Reply #21 on: 01/07/2015 02:51 AM »
F-1 had its share of scrubs and delays, not sure which would be counted here, random google

http://www.nasaspaceflight.com/2009/07/live-falcon-1-razaksat-for-malaysias-atsb/
http://www.spacelaunchreport.com/falcon.html
Quote
The first Falcon 1 launch attempt at Omelek on November 25, 2005 was scrubbed after a ground-supply LOX vent valve allowed the small LOX supply to boil off. 
http://www.nasaspaceflight.com/2009/07/live-falcon-1-razaksat-for-malaysias-atsb/
http://www.spaceflightnow.com/news/n0806/23falcon1/
http://spacenews.com/technical-problems-delay-falcon-1-launch/

Et cetera
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Offline Brovane

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Re: The SpaceX Scrubs thread
« Reply #22 on: 01/07/2015 03:00 AM »

I think it would be fairer to compare them to something earlier in the Delta family, or the Titan II

I wouldn't disagree except for one key thing.  SpaceX is trying to pitch the Falcon9 and eventually Falcon Heavy against the Atlas-V and Delta-IV for US govt launch contracts.  For lack of a better phrase, "If you want to run with the big dogs, you got to learn to pee in the tall grass."   
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Offline foltster

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Re: The SpaceX Scrubs thread
« Reply #23 on: 01/07/2015 03:42 AM »
You should add something to the key that [ ] indicates the source reference.

Online meekGee

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Re: The SpaceX Scrubs thread
« Reply #24 on: 01/07/2015 04:25 AM »
I'll add another comment.  While we are seeing plenty of problem getting past the static hot fires and only getting caught in real count-downs, we're not seeing problems getting past the count-down and causing LOVs.

That's significant, since the record for a new rocket, both for F9 1.0 and F9 1.1 is for all intents and purposes pristine. (yes we can argue about F9 1.0 flight 4)

A possible explanation to this discrepancy is that they abort on a hair trigger. Perhaps (speculating) the level of instrumentation is higher, and the number of abort conditions is higher, and the thresholds for the abort conditions are tight, and they do all this because in these transformative years, they're rather take a hit on their launch rate than on their track record.

Because honestly - I'm a fanboy, I think SpaceX is highly competent, and so I am looking for a rational explanation not to why there are aborts (I expect that), but to why there are post-hot-fire aborts (which is odd).
« Last Edit: 01/07/2015 04:25 AM by meekGee »
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Offline nimbostratus

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Re: The SpaceX Scrubs thread
« Reply #25 on: 01/07/2015 04:50 AM »
I'll add another comment.  While we are seeing plenty of problem getting past the static hot fires and only getting caught in real count-downs, we're not seeing problems getting past the count-down and causing LOVs.

That's significant, since the record for a new rocket, both for F9 1.0 and F9 1.1 is for all intents and purposes pristine. (yes we can argue about F9 1.0 flight 4)

A possible explanation to this discrepancy is that they abort on a hair trigger. Perhaps (speculating) the level of instrumentation is higher, and the number of abort conditions is higher, and the thresholds for the abort conditions are tight, and they do all this because in these transformative years, they're rather take a hit on their launch rate than on their track record.

Because honestly - I'm a fanboy, I think SpaceX is highly competent, and so I am looking for a rational explanation not to why there are aborts (I expect that), but to why there are post-hot-fire aborts (which is odd).

It seems that static test firing does not involve the second stage.
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Online meekGee

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Re: The SpaceX Scrubs thread
« Reply #26 on: 01/07/2015 04:52 AM »
I'll add another comment.  While we are seeing plenty of problem getting past the static hot fires and only getting caught in real count-downs, we're not seeing problems getting past the count-down and causing LOVs.

That's significant, since the record for a new rocket, both for F9 1.0 and F9 1.1 is for all intents and purposes pristine. (yes we can argue about F9 1.0 flight 4)

A possible explanation to this discrepancy is that they abort on a hair trigger. Perhaps (speculating) the level of instrumentation is higher, and the number of abort conditions is higher, and the thresholds for the abort conditions are tight, and they do all this because in these transformative years, they're rather take a hit on their launch rate than on their track record.

Because honestly - I'm a fanboy, I think SpaceX is highly competent, and so I am looking for a rational explanation not to why there are aborts (I expect that), but to why there are post-hot-fire aborts (which is odd).

It seems that static test firing does not involve the second stage.

Well they don't fire it of course, but they don't fire it during a real count-down either...   They do go through some testing, and do you have specific information that they don't do these tests on the hot fires?  If so, why not?
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Offline nimbostratus

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Re: The SpaceX Scrubs thread
« Reply #27 on: 01/07/2015 05:08 AM »
I get no specific infornation, but there is a simple reason, engines optimized for vacuum have problems with firing at sea level.
And how the thrust vectoring problem was detected for this attempt is a mystery.
« Last Edit: 01/07/2015 05:53 AM by nimbostratus »
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Online meekGee

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Re: The SpaceX Scrubs thread
« Reply #28 on: 01/07/2015 05:54 AM »
I get no specified infornation regarding this, but there is a simple reason, engines optimized for vacuum have problems with firing at sra level.
And how the thrust vectoring problem was detected for this attempt is a mystery.

Heh, that, plus the fact that if you fire the second stage engine while it is attached to the first, it's get some interesting results. :)

You can test almost anything though.  Any electric circuit can be given a voltage or current limited probing signal, and the response compared to a nominal response.  Actuators can exercised (caveat: engine pressurized hydralics can only be partially tested), and position sensors read.  I am not sure if there are any items that occur on a real count-down that cannot be be tested in a hot fire.

The thing is, there's no such thing as perfectly reproducible results, and it's up to the tester to decide whether the deviations are large enough to warrant and abort or investigation. It could very well be that many of the aborts are just a result of being uber-careful. 

Not all though, and there was one item at least that definitely broke during count-down (the helium gasket) - but that's not a trend yet.
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Offline Lars-J

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Re: The SpaceX Scrubs thread
« Reply #29 on: 01/07/2015 06:34 AM »
This thread is not without merit.... But when I start seeing scrubs of hot fires, then I think it has gone too far.

The same goes for delays months in advance which shifts the launch date.

How about limiting it to scrubs/delays of actual launch attempts, only within a few days of the first launch attempt? In other words, any delay or scrub AFTER the hot fire.
« Last Edit: 01/07/2015 06:35 AM by Lars-J »

Offline Darkseraph

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Re: The SpaceX Scrubs thread
« Reply #30 on: 01/07/2015 06:44 AM »
Scrubs don't bother me, nor are enough rockets launched that we'll see a particular meaningful pattern in the amount of scrubs/faults or an apparent commonality of them. Better safe than headed on a subterranean lithobreaking orbit, lest SpaceX be forced to re-purpose itself as the premier pyrotechnics company in the USA, good for everything from your kids birthday to 4th of July extravaganzas!

I'm glad they are being cautious and not like endangering payloads of people. What faults show up will be interesting in an abstract way though, so I'll keep an eye on this thread.
"For a successful technology, reality must take precedence over public relations, for Nature cannot be fooled." R.P.Feynman

Offline ChrisWilson68

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Re: The SpaceX Scrubs thread
« Reply #31 on: 01/07/2015 07:58 AM »

I think it would be fairer to compare them to something earlier in the Delta family, or the Titan II

I wouldn't disagree except for one key thing.  SpaceX is trying to pitch the Falcon9 and eventually Falcon Heavy against the Atlas-V and Delta-IV for US govt launch contracts.  For lack of a better phrase, "If you want to run with the big dogs, you got to learn to pee in the tall grass."   

Only to the extent the government cares about the delays.  If the government isn't concerned about a three-day slip, we shouldn't be either.

Offline Bargemanos

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Re: The SpaceX Scrubs thread
« Reply #32 on: 01/07/2015 09:30 AM »
This thread is not without merit.... But when I start seeing scrubs of hot fires, then I think it has gone too far.

The same goes for delays months in advance which shifts the launch date.

How about limiting it to scrubs/delays of actual launch attempts, only within a few days of the first launch attempt? In other words, any delay or scrub AFTER the hot fire.

A hot fire can delay the actual lanch. So, to get a complete picture of a launch including static fires, delays etc one should include everything from start to end.

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Re: The SpaceX Scrubs thread
« Reply #33 on: 01/07/2015 09:45 AM »
Why is there a discrepancy for the CRS-5 launch this week in the abort time? I know SpaceX officially reported the abort time for 1:21, but very clearly the "hold hold hold" was called at 1:29, according to the display on the tv. Could there be an eight-second difference between the SpaceX launch clock and the display on the tv? If it had launched, would it have launched when there was still 8 seconds on the clock? Go to the 1:20 point in this youtube video to see

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Re: The SpaceX Scrubs thread
« Reply #34 on: 01/07/2015 10:01 AM »
Speculating here, but it took about 8 seconds from hold hold hold to the call to stop the clock and confirmation. The time when the clock actually stopped and the launch countdown systems really were aborted is the time reported I guess hence T-1:21 and not T-1:29.

Also, if you listen to the initial terminal countdown announcement, then no hold shall be called after T-10s as I guess the timing is too tight to do a manual abort at that point and the automatic systems should take over. People more knowledgable in the process can probably explain more/better.

Offline JamesH

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Re: The SpaceX Scrubs thread
« Reply #35 on: 01/07/2015 10:09 AM »

I think it would be fairer to compare them to something earlier in the Delta family, or the Titan II

I wouldn't disagree except for one key thing.  SpaceX is trying to pitch the Falcon9 and eventually Falcon Heavy against the Atlas-V and Delta-IV for US govt launch contracts.  For lack of a better phrase, "If you want to run with the big dogs, you got to learn to pee in the tall grass."   

Of course, the F9/FH are intended to compete with these older rockets, and will need to match their reliability, but you are comparing the wrong things i.e. a relatively new rocket with an older heavily tested rocket. To make the 'comparison statistics' valid, you need to compare them at similar points in their development schedule.

I would expect that Spx will get to the same level of reliability/launch cadence more quickly than Atlas and Delta did, simply because of advances in technology. But they still need to be careful.

Offline pagheca

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Re: The SpaceX Scrubs thread
« Reply #36 on: 01/07/2015 10:15 AM »
My understanding is that SpaceX takes extremely seriously any discrepancy because of the bad, maybe deadly impact a LOV would have on such a small firm future. They came to the conclusion that the impact of, let's say 10 or 20 maybe unnecessary scrubs even of an unmanned rocket would be minor than a single catastrophic failure. This is much more than, for example, Boeing, as SpaceX is a relatively small venture, and as such has lots of fan in the public but a lot of haters in the various lobbies as any little company (or individual) claiming something the big companies (or the "experts") denied can be done.

Said that, I don't think that a bunch of launches of a vehicle are enough to expect scrubs nearing zero. At the end of the day, we are talking about less of a few hours of operation in flights of the overall first stage system, with consistent upgrades over each launches.

"As a newbie" my position is rather this: SpaceX has still to demonstrate its initial goals, that is an affordable and reliable reutilization of a rocket. I expect this to take a lot of time, some substantial upgrades, with substantial impacts on any Mars plan or "factor 20" reduction in space flight cost.

In other words I'm a "skeptic" about most of SpaceX plans, but a scientific skeptic AND admirer at the same time because, even if they do 1/10 of what they plan and/or in 3 times more time than promised, it will be a great achievement. And what they did till today is ALREADY a great achievement: they gave a new flavour to spaceflight, the feeling that there can be something new, light and less corporate-like than in the past.
« Last Edit: 01/09/2015 09:22 AM by pagheca »

Offline Brovane

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Re: The SpaceX Scrubs thread
« Reply #37 on: 01/07/2015 12:03 PM »

I think it would be fairer to compare them to something earlier in the Delta family, or the Titan II

I wouldn't disagree except for one key thing.  SpaceX is trying to pitch the Falcon9 and eventually Falcon Heavy against the Atlas-V and Delta-IV for US govt launch contracts.  For lack of a better phrase, "If you want to run with the big dogs, you got to learn to pee in the tall grass."   

Of course, the F9/FH are intended to compete with these older rockets, and will need to match their reliability, but you are comparing the wrong things i.e. a relatively new rocket with an older heavily tested rocket. To make the 'comparison statistics' valid, you need to compare them at similar points in their development schedule.

I would expect that Spx will get to the same level of reliability/launch cadence more quickly than Atlas and Delta did, simply because of advances in technology. But they still need to be careful.

Quote
Personally for me I would like to know how SpaceX compares to historical scrub rates with the early launches of Atlas-V/Delta-IV.

I was asking to compare to early launches of the Atlas-V and Delta-IV when they were both new vehicles.  The Delta-IV besides the upper stage doesn't share much in common with the earlier Delta series vehicles.  The Atlas-III makes a break from earlier Atlas vehicles.  The big advantage is that the Atlas-III and V still use the Centaur which does have a extensive flight history. 
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Offline Jim

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Re: The SpaceX Scrubs thread
« Reply #38 on: 01/07/2015 01:02 PM »
I get no specific infornation, but there is a simple reason, engines optimized for vacuum have problems with firing at sea level.
And how the thrust vectoring problem was detected for this attempt is a mystery.

They slew the engine during the countdown
« Last Edit: 01/07/2015 01:02 PM by Jim »

Offline Jim

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Re: The SpaceX Scrubs thread
« Reply #39 on: 01/07/2015 01:09 PM »
Why is there a discrepancy for the CRS-5 launch this week in the abort time? I know SpaceX officially reported the abort time for 1:21, but very clearly the "hold hold hold" was called at 1:29, according to the display on the tv.

There is no discrepancy.  The abort time is when the clock is stopped and not when the hold call is made.  Countdowns have vehicle specific points to stop the clock when holds are called.  They are usually between certain events (after one completes and before others start)

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