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#460
by
guckyfan
on 07 Oct, 2013 04:20
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#461
by
Robotbeat
on 07 Oct, 2013 04:26
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I agree it may be desirable to be able to command a reusable upper stage, but why do you think it would need such a long loiter time?
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#462
by
guckyfan
on 07 Oct, 2013 04:45
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#463
by
Garrett
on 07 Oct, 2013 08:40
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A reusable upper stage will need a loiter time in the range of one day and probably the ability to receive commands.
Says who?
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#464
by
Silmfeanor
on 07 Oct, 2013 08:43
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Please take this discussion somewhere else. It has nothing to do with this mission.
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#465
by
cambrianera
on 07 Oct, 2013 13:22
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The previous M-vac was successfully restarted in orbit. Of course this is a substantially new engine. But most other contemporary launch vehicles have restartable upper stages (Ariane 5 ECA is an exception).
As you say, we have to wait to see what they decide to release about the problem and its solution.
Aaah, but on the first Falcon 9 flight the attempted second burn with the original M-Vac engine also failed. It led to a spiral and much Australian UFO sightings.
Indeed, this seems like a very similar situation, although the root cause might be different. But an upper stage restart was achieved on the second F9 flight.
First F9 flight the 2nd stage developed a quite important roll due to the TPA exaust actuator that froze.
Most probably the restart failed (they got only a burp, that's what was said) due to problems in settling propellants (if someone remember something more....).
This time no roll (in 2nd stage
) but that unusual venting after SECO.
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#466
by
beancounter
on 08 Oct, 2013 03:29
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The previous M-vac was successfully restarted in orbit. Of course this is a substantially new engine. But most other contemporary launch vehicles have restartable upper stages (Ariane 5 ECA is an exception).
As you say, we have to wait to see what they decide to release about the problem and its solution.
Aaah, but on the first Falcon 9 flight the attempted second burn with the original M-Vac engine also failed. It led to a spiral and much Australian UFO sightings.
Indeed, this seems like a very similar situation, although the root cause might be different. But an upper stage restart was achieved on the second F9 flight.
First F9 flight the 2nd stage developed a quite important roll due to the TPA exaust actuator that froze.
Most probably the restart failed (they got only a burp, that's what was said) due to problems in settling propellants (if someone remember something more....).
This time no roll (in 2nd stage ) but that unusual venting after SECO.
Was it 'unusual'? Who made that statement?
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#467
by
cambrianera
on 08 Oct, 2013 08:19
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First F9 flight the 2nd stage developed a quite important roll due to the TPA exaust actuator that froze.
Most probably the restart failed (they got only a burp, that's what was said) due to problems in settling propellants (if someone remember something more....).
This time no roll (in 2nd stage ) but that unusual venting after SECO.
Was it 'unusual'? Who made that statement?
The statement is mine (did you see the clip?)
Venting was:
Not seen before with this intensity/modality in five flights.
Quite energetic, not usual purging/venting.
It's clearly visible in frames of the movie.
From
http://www.flickr.com/photos/jurvetson/10008137326/
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#468
by
gwiz
on 08 Oct, 2013 14:49
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Quite energetic, not usual purging/venting.
This could explain the considerable scatter of the tracked fragments - shed pieces of insulation caught up in the energetic venting and blown away from the stage at high velocity.
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#469
by
blazotron
on 08 Oct, 2013 15:50
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First F9 flight the 2nd stage developed a quite important roll due to the TPA exaust actuator that froze.
Most probably the restart failed (they got only a burp, that's what was said) due to problems in settling propellants (if someone remember something more....).
This time no roll (in 2nd stage ) but that unusual venting after SECO.
Was it 'unusual'? Who made that statement?
The statement is mine (did you see the clip?)
Venting was:
Not seen before with this intensity/modality in five flights.
Quite energetic, not usual purging/venting.
It's clearly visible in frames of the movie.
From http://www.flickr.com/photos/jurvetson/10008137326/
Different compared to 1.0, sure, but I don't think the data supports "unusual" where I take that to mean "off-nominal". This is a new engine, new stage, and maybe even a new relative position of camera compared to features on the stage or engine (clearly the field of view differs in some ways).
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#470
by
aero
on 08 Oct, 2013 16:10
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Who wants to speculate as to whether the liquid venting was LOX or RP-1?
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#471
by
cambrianera
on 08 Oct, 2013 16:21
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Venting was:
Not seen before with this intensity/modality in five flights.
Quite energetic, not usual purging/venting.
It's clearly visible in frames of the movie.
From http://www.flickr.com/photos/jurvetson/10008137326/
Different compared to 1.0, sure, but I don't think the data supports "unusual" where I take that to mean "off-nominal". This is a new engine, new stage, and maybe even a new relative position of camera compared to features on the stage or engine (clearly the field of view differs in some ways).
You are correct saying that it doesn't mean "off-nominal". I don't know what's nominal on Merlin DVac, hence no possibility to say what's off-nominal.
I wrote the word unusual because that venting was not seen before (hence not usual) and not standard purging/venting (hence not usual).
That's it, a little bit of speculation on something outside some expected boundaries.
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#472
by
cambrianera
on 08 Oct, 2013 16:27
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#473
by
LegendCJS
on 08 Oct, 2013 16:29
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Venting was:
Not seen before with this intensity/modality in five flights.
Quite energetic, not usual purging/venting.
It's clearly visible in frames of the movie.
From http://www.flickr.com/photos/jurvetson/10008137326/
Different compared to 1.0, sure, but I don't think the data supports "unusual" where I take that to mean "off-nominal". This is a new engine, new stage, and maybe even a new relative position of camera compared to features on the stage or engine (clearly the field of view differs in some ways).
You are correct saying that it doesn't mean "off-nominal". I don't know what's nominal on Merlin DVac, hence no possibility to say what's off-nominal.
I wrote the word unusual because that venting was not seen before (hence not usual) and not standard purging/venting (hence not usual).
That's it, a little bit of speculation on something outside some expected boundaries.
It was my understanding that it is now international practice to not leave derelict upper stages full of propellant hanging around in orbit due to agreements over managing orbital debris risk. Some of the largest single sources of current orbital debris are detonated upper stages from old GTO launches. I'd think that by now all modern upper stages have provisions to vent all propellants overboard to reduce the debris pollution risk. So while SpaceX might have prefered to burn the propellants instead, once the failure to restart was evident, intentional clearing of the tanks is the obvious next step, and very nominal for that situation.
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#474
by
guckyfan
on 08 Oct, 2013 16:40
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A general question about venting. Would they vent both the LOX and the RP-1? Venting LOX may be easier and without LOX RP-1 will be harmless. That assumption may be wrong, please correct me.
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#475
by
cambrianera
on 08 Oct, 2013 16:48
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Venting was:
Not seen before with this intensity/modality in five flights.
Quite energetic, not usual purging/venting.
It's clearly visible in frames of the movie.
From http://www.flickr.com/photos/jurvetson/10008137326/
Different compared to 1.0, sure, but I don't think the data supports "unusual" where I take that to mean "off-nominal". This is a new engine, new stage, and maybe even a new relative position of camera compared to features on the stage or engine (clearly the field of view differs in some ways).
You are correct saying that it doesn't mean "off-nominal". I don't know what's nominal on Merlin DVac, hence no possibility to say what's off-nominal.
I wrote the word unusual because that venting was not seen before (hence not usual) and not standard purging/venting (hence not usual).
That's it, a little bit of speculation on something outside some expected boundaries.
It was my understanding that it is now international practice to not leave derelict upper stages full of propellant hanging around in orbit due to agreements over managing orbital debris risk. Some of the largest single sources of current orbital debris are detonated upper stages from old GTO launches. I'd think that by now all modern upper stages have provisions to vent all propellants overboard to reduce the debris pollution risk. So while SpaceX might have prefered to burn the propellants instead, once the failure to restart was evident, intentional clearing of the tanks is the obvious next step, and very nominal for that situation.
The venting cited in my post starts exactly at SECO1, then no failure to restart was evident (bold mine).
SpaceX vented intentionally the stage later (over South Africa and Madagascar, as cited in the news).
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#476
by
kevin-rf
on 08 Oct, 2013 17:30
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It was my understanding that it is now international practice to not leave derelict upper stages full of propellant hanging around in orbit due to agreements over managing orbital debris risk. Some of the largest single sources of current orbital debris are detonated upper stages from old GTO launches. I'd think that by now all modern upper stages have provisions to vent all propellants overboard to reduce the debris pollution risk. So while SpaceX might have prefered to burn the propellants instead, once the failure to restart was evident, intentional clearing of the tanks is the obvious next step, and very nominal for that situation.
Not all, Chinese LH upper stages still break up and Russia Briz-M's that fail do not vent and then have a tendency to rather violently break up after about a year.
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#477
by
bunker9603
on 08 Oct, 2013 18:45
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It was my understanding that it is now international practice to not leave derelict upper stages full of propellant hanging around in orbit due to agreements over managing orbital debris risk. Some of the largest single sources of current orbital debris are detonated upper stages from old GTO launches. I'd think that by now all modern upper stages have provisions to vent all propellants overboard to reduce the debris pollution risk. So while SpaceX might have prefered to burn the propellants instead, once the failure to restart was evident, intentional clearing of the tanks is the obvious next step, and very nominal for that situation.
Not all, Chinese LH upper stages still break up and Russia Briz-M's that fail do not vent and then have a tendency to rather violently break up after about a year.
Then based on that it seems like SpaceX did the responsible thing.
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#478
by
LouScheffer
on 08 Oct, 2013 18:52
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It was my understanding that it is now international practice to not leave derelict upper stages full of propellant hanging around in orbit due to agreements over managing orbital debris risk.
Not all, Chinese LH upper stages still break up and Russia Briz-M's that fail do not vent and then have a tendency to rather violently break up after about a year.
The Chinese vehicles fixed this a while ago, according to
http://adsabs.harvard.edu/full/1997ESASP.393..689Z, " Elimination of the Potential Hazard of the Long March 4 Launch Vehicle's On-Orbit Breakup". In practice, I don't recall any recent breakups of Chinese upper stages.
However, 3 Briz upper stages have exploded since 2007, according to
http://orbitaldebris.jsc.nasa.gov/newsletter/pdfs/ODQNv17i1.pdf
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#479
by
douglas100
on 08 Oct, 2013 19:29
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A general question about venting. Would they vent both the LOX and the RP-1? Venting LOX may be easier and without LOX RP-1 will be harmless. That assumption may be wrong, please correct me.
Don't know about RP-1, but the LOX
must be vented (or at least be allowed to evaporate through a pressure relief valve) to avoid the tank rupturing.
) but that unusual venting after SECO.