Author Topic: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION  (Read 624315 times)

Offline MP99

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

Offline joek

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #741 on: 10/08/2012 09:50 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.
« Last Edit: 10/08/2012 09:50 pm by joek »

Offline Go4TLI

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #742 on: 10/08/2012 09:51 pm »
Should we start a new thread full of apologies for those who guaranteed there was an explosion? Or just sweep that under the rug?
Can I +1 this and suggest that we not sweep it under the rug?
I'm not a big fan of letting people forget how absurd they come across when they assert speculation masked as fact.
That also goes for those who started and stoked the GNC door rumour.

*grumbles in his armchair*

Edit: am mildly tempted to snark about "luck" comments. Hmmm, maybe I just did.

No comment on the GNC door but if people want to talk SpaceX, they have to speak about all of it.

An "engine pressure release" that blows a fairing off your rocket is not a normal thing.  I think people should indeed acknowledge they were lucky that it was not more serious because an "engine pressure release" that causes an engine to shut down, the first stage to burn longer, etc could certainly have had a much stronger impact on the climb up hill.

There is nothing wrong with discussing, if after all that is what people want to do, and suggesting that a root cause be found and determined and making sure whatever that was does not have an impact on other engines, in production or design. 

That is good engineering.  That is smart business.

Offline Peter NASA

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #743 on: 10/08/2012 09:52 pm »
That's because it wasn't an explosion. I would expect Chris will be writing an article out of L2 content soon. Already excellent information in there.

Offline mrmandias

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #744 on: 10/08/2012 09:52 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.

I saw that.  Unless Orbcomm is lying or there is some kind of complicated connection, it looks like loss of fuel on the second stage wasn't the reason for the Orbcomm failure.

Offline ugordan

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #745 on: 10/08/2012 09:55 pm »
Unless Orbcomm is lying or there is some kind of complicated connection, it looks like loss of fuel on the second stage wasn't the reason for the Orbcomm failure.

They're not lying and there is a connection.

Offline DEL

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #746 on: 10/08/2012 09:55 pm »
Very new here, please forgive me if I am saying something odd, but reading all these posts, am I to understand there are folks actually cheerleading for a mission to fail? Looking for any potential way they possibly can to deem a successful mission ( so far ) a failure?

Personally I wish them all success, even the Chinese missions ( we could use a little competition )

I will as heartily hope Orbital's attempts a success as I have Space X, and the MSL and every ULA mission.

On a positive side some of the posts here are extremely informative, I will likely be a rare poster, but avid reader.

Online Lee Jay

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #747 on: 10/08/2012 09:59 pm »
Very new here, please forgive me if I am saying something odd, but reading all these posts, am I to understand there are folks actually cheerleading for a mission to fail? Looking for any potential way they possibly can to deem a successful mission ( so far ) a failure?

Of course not.

Offline neilh

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #748 on: 10/08/2012 09:59 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"?
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Online Robotbeat

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #749 on: 10/08/2012 09:59 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.

I saw that.  Unless Orbcomm is lying or there is some kind of complicated connection, it looks like loss of fuel on the second stage wasn't the reason for the Orbcomm failure.
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.

Just goes to show you that this is a very difficult and highly constrained business.
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Offline Chris-A

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #750 on: 10/08/2012 10:02 pm »
ISS Collision avoidance?

Offline mmeijeri

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #751 on: 10/08/2012 10:02 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?
Pro-tip: you don't have to be a jerk if someone doesn't agree with your theories

Offline rcoppola

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #752 on: 10/08/2012 10:03 pm »
An ISS Safety Gateway? I get this conceptually but what is this specifically.
What triggers the gate to close? And is it a relevant trigger with the way the Falcon 9 was designed to handle certain engine out events?

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Offline Lurker Steve

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #753 on: 10/08/2012 10:03 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.

Offline Go4TLI

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #754 on: 10/08/2012 10:04 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"?

Terminology that means position of the stage and release of the sats will not have a chance of intersecting ISS within a specific box/radius around the station.

Offline Kabloona

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #755 on: 10/08/2012 10:09 pm »
Very new here, please forgive me if I am saying something odd, but reading all these posts, am I to understand there are folks actually cheerleading for a mission to fail? Looking for any potential way they possibly can to deem a successful mission ( so far ) a failure?

Personally I wish them all success, even the Chinese missions ( we could use a little competition )

I will as heartily hope Orbital's attempts a success as I have Space X, and the MSL and every ULA mission.

On a positive side some of the posts here are extremely informative, I will likely be a rare poster, but avid reader.


No one here is cheerleading for failure. We all wish SpaceX success (and I say that as a former Orbital engineer). Just different observers offering different speculations about what may have happened.

Offline douglas100

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #756 on: 10/08/2012 10:19 pm »
An ISS Safety Gateway? I get this conceptually but what is this specifically.
What triggers the gate to close? And is it a relevant trigger with the way the Falcon 9 was designed to handle certain engine out events?

That's an excellent question. Maybe it was a requirement (by NASA?) for this flight that if any anomaly occurred during ascent that the second burn was automatically canceled. I'll be interested to hear what the professionals have to say on this point.
Douglas Clark

Offline marsman2020

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #757 on: 10/08/2012 10:19 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.

Orbcomm keeps getting shafted.
« Last Edit: 10/08/2012 10:20 pm by marsman2020 »

Offline cordor

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #758 on: 10/08/2012 10:22 pm »
Am I late with this? - http://www.spacex.com/press.php?page=20121008

"Panels designed to relieve pressure within the engine bay were ejected to protect the stage and other engines. "

Oh, that's interesting.  Are they saying that the deliberate ejection of panels is somehow part of their engine protection scheme?  I'm having a hard time visualizing how that would work.

Keep in mind, this almost certainly refers to the overall engine bay, not blowouts on the failed engine itself.

The engine bay is the space above the nozzles, which mostly-encloses the combustion chambers with the aerodynamic fairings and the debris shields between the engines, etc. See a photo with covers in place here:
http://www.wired.com/autopia/2012/05/spacex-launch-aborted-as-engine-ignition-begins/

If you have a combustion chamber or turbopump failure, that means combustion gasses or possibly even fuel and oxidizer in an enclosed space. Hot gas + nowhere to go equals increasing pressure and heat.

(the engine bay isn't even close to sealed as far as I know, but the pressure may rise faster than whatever is leaking into the bay can leak out)

That could potentially damage the other engines, or their fuel lines, actuators, and instrumentation, or even the rocket structure.

So you can design some of those panels to deliberately be the weak point in all the structure that encloses the engine bay. When the pressure reaches a certain point, the panels burst or tear off instead of the pressure reaching the point where something more important fails.

Anybody started the betting yet? My money is on turbopump RUD.

FOr spacex, it's always valve problem.

Offline thydusk666

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #759 on: 10/08/2012 10:24 pm »
Very new here, please forgive me if I am saying something odd, but reading all these posts, am I to understand there are folks actually cheerleading for a mission to fail? Looking for any potential way they possibly can to deem a successful mission ( so far ) a failure?

Personally I wish them all success, even the Chinese missions ( we could use a little competition )

I will as heartily hope Orbital's attempts a success as I have Space X, and the MSL and every ULA mission.

On a positive side some of the posts here are extremely informative, I will likely be a rare poster, but avid reader.

+1 for all the above.
I am surprised by some posts in this thread which leave a bitter taste...

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