Author Topic: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION  (Read 624672 times)

Offline cordor

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #760 on: 10/08/2012 10:26 pm »
Very interesting, and not quite what anyone speculated about as a reason. ...not caused by a failure of the upper stage, not even necessarily because of extra gravity losses but because of ISS safety constraints.

Don't you think that is caused by a lack of propellant?

Well, at first, they said engine one exploded. Engine one didn't exploded but shut down. And then they said second stage didn't restart, now low on fuel.

It's getting clear, romney is attacking elon again.

Offline cordor

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #761 on: 10/08/2012 10:30 pm »
ORBCOMM press release in updates thread.  Interesting bit:
Quote
However, due to an anomaly on one of the Falcon 9ís first stage engines, the rocket did not comply with a pre-planned International Space Station (ISS) safety gate to allow it to execute the second burn. For this reason, the OG2 prototype satellite was deployed into an orbit that was lower than intended.

Could anyone explain a little more about what's meant by the ISS "safety gate"?


Offline joek

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #762 on: 10/08/2012 10:34 pm »
Very interesting, and not quite what anyone speculated about as a reason. ...not caused by a failure of the upper stage, not even necessarily because of extra gravity losses but because of ISS safety constraints.
Don't you think that is caused by a lack of propellant?

Very possibly.  In any case, the situation must have been fairly clear as they didn't spend much time before deciding.  According the ORBCOMM press release, separation was "approximately 9:00PM EST", ~L+25min, or ~15min after Dragon separation.

Offline modemeagle

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #763 on: 10/08/2012 10:41 pm »
For modemeagle: in your simulations if F9v1 loses thrust from two engines at T+1:20 does the payload reach any orbit at all?
Yes, according to my simulation.

Offline cordor

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #764 on: 10/08/2012 10:49 pm »
Folks haven't mentioned this AFAICT, but it's worth noting that the Orbcomm "silence" may in fact be Orbcomm's fault/decision, not SpaceX's.  SpaceX has been very forthcoming about their part of the flight, but they may well have contractual obligations (or just a need to have releases vetted by Orbcomm executives) which prevent them from speaking as freely about the Orbcomm-related aspects of the flight.  Folks here have noted that Orbcomm was in a information blackhole even before the flight, with SpaceX's preflight materials not mentioning the Orbcomm satellite.

Putting on my wild guessing hat, I'd suspect that the Orbcomm delivery was not in fact "nominal" but fell squarely under the terms of service SpaceX was contracted to provide.  Secondary payloads get best-effort delivery, and off-nominal orbit insertion is one of the most likely results.  Orbcomm may or may not have chosen to cover for that possibility with thrust resources on its own satellite (at the expense of a shorter lifetime in-orbit), but that was its own choice.

Orbcomm will need to spin this even more than SpaceX, though.  It knew this was a likely outcome of flying as a secondary payload but the wordsmiths are going to be very busy crafting a press release which all of SpaceX, Orbcomm, Orbcomm's executive which approved flying as a secondary payload, Orbcomm's insurance, and Orbcomm's investors are satisfied with.

I don't believe OrbComm originally signed up as a secondary payload. They got screwed once already because SpaceX cancelled the F1, where they would have been the primary payload.


I think OG-2 are very cheap satellites, and Orbcomm have 18 of them. i suspect they rather lose 1/3 of the satellites than launch with falcon 1e or  Pegasus.

Offline modemeagle

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #765 on: 10/08/2012 10:50 pm »
Depending on the payload, and if the engine failed early (ie navigation predicts it can't hit the target orbit even using all margin), I wonder if navigation might keep all eight engines firing - not do a MECO-1 at all and just hope everything survives the G overload (which could be up to 1.14 x nominal, ie 8/7ths).

Reminder: all speculation from first principles.

The 1.14 G overload would only cause stress (or rather compression) above plan at the cabin end. This might be an issue with tourists but hopefully not for cargos.

At the engine end, the force on the frame is what the engines produce. It will be designed for 9 engines. 8 engines firing compared to 7 is still 8/9th of launch compression, even if the acceleration is higher.

Simulating the flight, I get the following times:
Engine out (9 drop to 8 engines): 80 seconds
5G limit engine out (8 drop to 7 engines): 191.6 seconds
S1 MECO: 195.3 seconds

Skipping the 5G limit shutdown gives a Meco of 194.7 seconds and 47.4m/s acceleration.

Run with an estimated payload of 6.6 tonnes.

If it reaches 5G at 191.6s, then 47.4 m/s @ 194.7s can't be right because I make that only 4.8G.

cheers, Martin
The difference is due to drag gravity losses of acceleration.
« Last Edit: 10/08/2012 10:53 pm by modemeagle »

Offline upjin

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #766 on: 10/08/2012 11:00 pm »
Can anybody make an educated guess on the orbit that the ORBCOMM's prototype OG-2 could possibly get to?

And at this point it can't be said that SpaceX failed in regards to the OG-2 prototype, because it's not clear what it can't do at the lower orbit.  It might be that it can complete all of it's tests at the lower orbit, or at least most of them and the important ones.


Online Robotbeat

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #767 on: 10/08/2012 11:00 pm »
Very interesting, and not quite what anyone speculated about as a reason. ...not caused by a failure of the upper stage, not even necessarily because of extra gravity losses but because of ISS safety constraints.

Don't you think that is caused by a lack of propellant?

Well, at first, they said engine one exploded. Engine one didn't exploded but shut down. And then they said second stage didn't restart, now low on fuel.

It's getting clear, romney is attacking elon again.
dahell? Why do you keep saying that?
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline Jim

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #768 on: 10/08/2012 11:01 pm »


Very possibly.  In any case, the situation must have been fairly clear as they didn't spend much time before deciding.  According the ORBCOMM press release, separation was "approximately 9:00PM EST", ~L+25min, or ~15min after Dragon separation.

There isn't any "deciding".   Launch vehicles are autonomous.  There is no ground commanding.  The propellant check failed so then the vehicle go on to next task in the flight program

Offline Remes

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #769 on: 10/08/2012 11:01 pm »
The part falling away here seems to be much heavier then the ice (and the ice doesn't leave a trail of fume). It's before the engine shutdown. Seen in "SpaceX CRS-1 Dragon Launch Replays.mp4" at 05:03:04, roughly 45s into flight (UCS-7 Tracker).

Offline bubbagret

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #770 on: 10/08/2012 11:03 pm »
Folks haven't mentioned this AFAICT, but it's worth noting that the Orbcomm "silence" may in fact be Orbcomm's fault/decision, not SpaceX's.  SpaceX has been very forthcoming about their part of the flight, but they may well have contractual obligations (or just a need to have releases vetted by Orbcomm executives) which prevent them from speaking as freely about the Orbcomm-related aspects of the flight.  Folks here have noted that Orbcomm was in a information blackhole even before the flight, with SpaceX's preflight materials not mentioning the Orbcomm satellite.

Putting on my wild guessing hat, I'd suspect that the Orbcomm delivery was not in fact "nominal" but fell squarely under the terms of service SpaceX was contracted to provide.  Secondary payloads get best-effort delivery, and off-nominal orbit insertion is one of the most likely results.  Orbcomm may or may not have chosen to cover for that possibility with thrust resources on its own satellite (at the expense of a shorter lifetime in-orbit), but that was its own choice.

Orbcomm will need to spin this even more than SpaceX, though.  It knew this was a likely outcome of flying as a secondary payload but the wordsmiths are going to be very busy crafting a press release which all of SpaceX, Orbcomm, Orbcomm's executive which approved flying as a secondary payload, Orbcomm's insurance, and Orbcomm's investors are satisfied with.

I don't believe OrbComm originally signed up as a secondary payload. They got screwed once already because SpaceX cancelled the F1, where they would have been the primary payload.


I think OG-2 are very cheap satellites, and Orbcomm have 18 of them. i suspect they rather lose 1/3 of the satellites than launch with falcon 1e or  Pegasus.
$6.5 Million each per: http://www.sncorp.com/press_more_info.php?id=371

Online Robotbeat

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #771 on: 10/08/2012 11:03 pm »
As far as the "ISS safety gate"...

The 2nd stage + Orbcomm ended up in the ~200 x 330 km orbit.  The intent was for the 2nd stage to relight to boost to 350 x 750 km.

If propellant in the 2nd stage was insufficient to complete the burn to 350 x 750 km with margins appropriate for any unknowns, if could instead end up in a ~400-430 x 330 km orbit, which might bring it close to ISS.

The "safety gate" was probably related to having enough propellant for be sure that everything ended up in orbits not a hazard to ISS.  Since it wasn't met - no relight.
...
Ah, plausible. And probably the best answer so far.

Could also be unrelated to level of propellant... I.e. because the ascent took longer, the orbital elements were different than expected, and thus the second stage relight wasn't cleared.
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Offline Comga

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #772 on: 10/08/2012 11:07 pm »
Very possibly.  In any case, the situation must have been fairly clear as they didn't spend much time before deciding.  According the ORBCOMM press release, separation was "approximately 9:00PM EST", ~L+25min, or ~15min after Dragon separation.

There isn't any "deciding".   Launch vehicles are autonomous.  There is no ground commanding.  The propellant check failed so then the vehicle go on to next task in the flight program

Jim: Is this a statement of fact based on flight telemetry or based on the operations of rockets in general and Falcon 9 in particular?
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Offline Joffan

Asked on the updates thread...
Only one question, why deploy if it was not in the " pre-planned International Space Station (ISS) safety gate".. why detach it from the stage.. ?

I'm guessing that your question is "Why not leave the Orbcomm satellite attached to Falcon Upper Stage and try the apogee raise a bit later at the next opportunity that is also safe for the ISS?"

And if that's the question, I'd like to know too. Are there limits on how long Falcon US can loiter up there and be effective? Or a limit on time between engine out and engine restart? And I see the speculation in this thread that the Falcon US didn't have enough fuel to guarantee an orbit clear of ISS altitudes - I'd have to say that that off-nominal possibility must have been worked out in advance, in that case, to make the decision in the timeframe.

My thought from the satellite end of the business would be whether the satellite needed to deploy solar arrays to get powered in some shortish window and couldn't wait for a further orbit.
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Online Robotbeat

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #774 on: 10/08/2012 11:10 pm »
Folks haven't mentioned this AFAICT, but it's worth noting that the Orbcomm "silence" may in fact be Orbcomm's fault/decision, not SpaceX's.  SpaceX has been very forthcoming about their part of the flight, but they may well have contractual obligations (or just a need to have releases vetted by Orbcomm executives) which prevent them from speaking as freely about the Orbcomm-related aspects of the flight.  Folks here have noted that Orbcomm was in a information blackhole even before the flight, with SpaceX's preflight materials not mentioning the Orbcomm satellite.

Putting on my wild guessing hat, I'd suspect that the Orbcomm delivery was not in fact "nominal" but fell squarely under the terms of service SpaceX was contracted to provide.  Secondary payloads get best-effort delivery, and off-nominal orbit insertion is one of the most likely results.  Orbcomm may or may not have chosen to cover for that possibility with thrust resources on its own satellite (at the expense of a shorter lifetime in-orbit), but that was its own choice.

Orbcomm will need to spin this even more than SpaceX, though.  It knew this was a likely outcome of flying as a secondary payload but the wordsmiths are going to be very busy crafting a press release which all of SpaceX, Orbcomm, Orbcomm's executive which approved flying as a secondary payload, Orbcomm's insurance, and Orbcomm's investors are satisfied with.

I don't believe OrbComm originally signed up as a secondary payload. They got screwed once already because SpaceX cancelled the F1, where they would have been the primary payload.


I think OG-2 are very cheap satellites, and Orbcomm have 18 of them. i suspect they rather lose 1/3 of the satellites than launch with falcon 1e or  Pegasus.
$6.5 Million each per: http://www.sncorp.com/press_more_info.php?id=371

A little more than half the cost of a Falcon 1e launch, back when they were still selling them. And replacement ones are probably less expensive.
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Offline Jim

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #775 on: 10/08/2012 11:11 pm »
Very possibly.  In any case, the situation must have been fairly clear as they didn't spend much time before deciding.  According the ORBCOMM press release, separation was "approximately 9:00PM EST", ~L+25min, or ~15min after Dragon separation.

There isn't any "deciding".   Launch vehicles are autonomous.  There is no ground commanding.  The propellant check failed so then the vehicle go on to next task in the flight program

Jim: Is this a statement of fact based on flight telemetry or based on the operations of rockets in general and Falcon 9 in particular?

in general

Offline cleonard

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #776 on: 10/08/2012 11:15 pm »
Can anybody make an educated guess on the orbit that the ORBCOMM's prototype OG-2 could possibly get to?

And at this point it can't be said that SpaceX failed in regards to the OG-2 prototype, because it's not clear what it can't do at the lower orbit.  It might be that it can complete all of it's tests at the lower orbit, or at least most of them and the important ones.

I looked around and it appears that the OG-2 has a deltav capability of 140 m/s.  From what I can tell the with a planned orbit of 350 x 700 km it was going to take about 110m/s to circularize at 700km.  With only 140 m/s to use there is no way they can make it to the desired orbit. 

Offline Jim

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #777 on: 10/08/2012 11:15 pm »

I'm guessing that your question is "Why not leave the Orbcomm satellite attached to Falcon Upper Stage and try the apogee raise a bit later at the next opportunity that is also safe for the ISS?"

 Are there limits on how long Falcon US can loiter up there and be effective?

There is battery life constraints.    Most LEO launch vehicles have only a couple to a few hour lifetime.  Most launch vehicles have limited capability to adapt on the fly.  They just follow a timeline and have no guidance updates. 

Offline jcm

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #778 on: 10/08/2012 11:20 pm »
Can anybody make an educated guess on the orbit that the ORBCOMM's prototype OG-2 could possibly get to?

And at this point it can't be said that SpaceX failed in regards to the OG-2 prototype, because it's not clear what it can't do at the lower orbit.  It might be that it can complete all of it's tests at the lower orbit, or at least most of them and the important ones.

I looked around and it appears that the OG-2 has a deltav capability of 140 m/s.  From what I can tell the with a planned orbit of 350 x 700 km it was going to take about 110m/s to circularize at 700km.  With only 140 m/s to use there is no way they can make it to the desired orbit. 

Do you have a source for that?
I believe they are required to keep 18  m/s for end of life disposal, so yes, they are out of luck if you are correct.
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Offline Avron

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #779 on: 10/08/2012 11:24 pm »

in general

Jim... in general, how can one determine the amount of fuel left in a stage that is in free flight..?

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