Author Topic: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION  (Read 625323 times)

Offline rcoppola

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #620 on: 10/08/2012 05:54 pm »
As people like Jim know only too well, this business is not easy. A bit of humility as to that fact, is never a bad thing.
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Offline alexterrell

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #621 on: 10/08/2012 05:57 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.

Offline Star One

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #622 on: 10/08/2012 05:58 pm »
Not there finest hour by any stretch of the imagination. Yes it survived the RUD (love that we have an acronym for something like this), but how much was that down to luck and how much down to engineering?

Overall maybe this will calm down some of this Space X good ULA & everyone else bad I have noted about.

Offline alexterrell

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #623 on: 10/08/2012 06:00 pm »
Perhaps not the finest hour, but if the mission is sucsessful (I take it we don't know yet), then they'll have learnt a lot more from this than with a routine mission.

Offline rdale

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #624 on: 10/08/2012 06:01 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?

Offline Kabloona

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #625 on: 10/08/2012 06:01 pm »
From the Ars article :

Quote
Approximately one minute and 19 seconds into last nightís launch, the Falcon 9 rocket detected an anomaly on one first stage engine. Initial data suggests that one of the rocketís nine Merlin engines, Engine 1, lost pressure suddenly and an engine shutdown command was issued immediately. We know the engine did not explode, because we continued to receive data from it. Our review indicates that the fairing that protects the engine from aerodynamic loads ruptured due to the engine pressure release, and that none of Falcon 9ís other eight engines were impacted by this event.

As designed, the flight computer then recomputed a new ascent profile in real time to ensure Dragonís entry into orbit for subsequent rendezvous and berthing with the ISS. This was achieved, and there was no effect on Dragon or the cargo resupply mission.

Falcon 9 did exactly what it was designed to do. Like the Saturn V, which experienced engine loss on two flights, Falcon 9 is designed to handle an engine out situation and still complete its mission.

http://arstechnica.com/science/2012/10/that-smooth-spacex-launch-turns-out-one-of-the-engines-exploded/

"the fairing ruptured...due to the engine pressure release..." so they already know it wasn't aero loads that broke the fairing loose, it was "engine pressure release," which I'm not sure how to interpret...a turbopump self-destructing, perhaps...

But however you interpret "engine pressure release," it looks like they believe the engine was, in fact, the point of failure.
« Last Edit: 10/08/2012 06:06 pm by Kabloona »

Offline IRobot

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #626 on: 10/08/2012 06:02 pm »
I wasn't saying the mission was a total failure, just that it could turn out to be a total failure. I'm really relieved the GNC door rumour was wrong, and I hope the Orbcomm one is too. The mission could still turn out to be a total success, though one with a very worrying anomaly. However, even now for all we know it could still end in total failure. Let's not count our Dragons before they hatch.

Dragon aside, this mission may well be a future reference for their marketing and even a reference for new rocket designs by other companies. Engine redundancy can save the day!

Offline Lars_J

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #627 on: 10/08/2012 06:03 pm »
I did notice another item kinda strange.  Was wondering if this was the tank that long ago had "welding issues" ?

Can you be more specific about this? The tank itself seems to have performed well - if it had a leak, I suspect it would not gone as well.

Offline Ben the Space Brit

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #628 on: 10/08/2012 06:04 pm »
The F9 shuts down two engines part way through the boost to keep Gs down, right? Does anybody know how an unplanned shutdown would affect the planned shutdowns?

Well, based purely on the MET clock, both MECO events were later than expected by about 30 seconds if my memory serves me well.


Re.: 'pressure release'.  I'm betting a fuel or oxidiser line downstream of the turbopump disconnected and the stream of high-flow-rate fluid coming out of the pump blew the fairing off.

If I'm right (remember: amateur here), I would have the guys at SLC-40 go over every nut and joint on the SpX-2 LV's fuel system and give them a few extra turns for luck.
« Last Edit: 10/08/2012 06:05 pm by Ben the Space Brit »
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Offline gwiz

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #629 on: 10/08/2012 06:05 pm »
Any official word on the Orbcomm satellites?
And if the Orbcomm is in the wrong orbit, does it have enough manoeuvre capability in its own right to get to the correct orbit?

Offline ugordan

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #630 on: 10/08/2012 06:06 pm »
From SpaceX:

Quote
... Initial data suggests that one of the rocketís nine Merlin engines, Engine 1, lost pressure suddenly and an engine shutdown command was issued immediately. ... Our review indicates that the fairing that protects the engine from aerodynamic loads ruptured due to the engine pressure release, and that none of Falcon 9ís other eight engines were impacted by this event.

Can someone clarify these two bolds? Does lost pressure imply a leak somewhere and what is the mechanism by which "engine pressure release" would affect something upstream? Is a sudden propellant line leak implied here?

Offline titanmiller

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #631 on: 10/08/2012 06:06 pm »



"the fairing ruptured...due to the engine pressure release..." so they already know it wasn't aero loads that broke the fairing loose, it was "engine pressure release," which I'm not sure how to interpret...a turbopump self-destructing, or ???

"engine pressure release" sounds synonymous to "explosion" to me. Maybe it wasn't a catastrophic explosion, but it definitely went out with a bang.

Think about it, if you were SpaceX, would you want to say that one of your engines "exploded"?
« Last Edit: 10/08/2012 06:09 pm by titanmiller »

Offline ugordan

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #632 on: 10/08/2012 06:08 pm »
And if the Orbcomm is in the wrong orbit, does it have enough manoeuvre capability in its own right to get to the correct orbit?

AFAIK, the 700x300 km orbit already was a compromise where the satellite would circularize itself and spend a good deal of propellant doing that. Reaching 700 km circular is probably out of the question if the satellite is stranded in a 200x300 km orbit.

Offline edkyle99

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #633 on: 10/08/2012 06:10 pm »
"the fairing ruptured...due to the engine pressure release..." so they already know it wasn't aero loads that broke the fairing loose, it was "engine pressure release," which I'm not sure how to interpret...a turbopump self-destructing, or ???

"engine pressure release" sounds synonymous to "explosion" to me. Maybe it wasn't a catastrophic explosion, but it definitely went out with a bang.

Think about it, if you were SpaceX, would you want to say that one of your engines "exploded"?

We're going to have six pages of discussion about the definition of "explosion" now...

In my opinion, mission-wise, a second stage restart failure, if that turns out to be the case, is more significant to potential SpaceX customers than the first stage engine shutdown, because a restart issue would be a flat out launch failure.

 - Ed Kyle
« Last Edit: 10/08/2012 06:13 pm by edkyle99 »

Offline Kabloona

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #634 on: 10/08/2012 06:10 pm »



"the fairing ruptured...due to the engine pressure release..." so they already know it wasn't aero loads that broke the fairing loose, it was "engine pressure release," which I'm not sure how to interpret...a turbopump self-destructing, or ???

"engine pressure release" sounds synonymous to "explosion" to me. Maybe it wasn't a catastrophic explosion, but it definitely went out with a bang.

Well, what's interesting is that they're saying the engine did NOT "explode" because they continued to receive telemetry from it...so clearly it was a violent failure, but it left some of the engine intact...which would be the case for a turbopump coming apart, for example...

Offline titanmiller

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #635 on: 10/08/2012 06:11 pm »
I don't understand the talk about the Orbicom satellite being in the wrong orbit. Wasn't it in Dragon's trunk? If Dragon reached the correct orbit, then so must have Orbicom.

I remember seen an animation that showed the satellite in the trunk and not on the second stage. Does anybody know?

Offline neilh

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #636 on: 10/08/2012 06:11 pm »
"the fairing ruptured...due to the engine pressure release..." so they already know it wasn't aero loads that broke the fairing loose, it was "engine pressure release," which I'm not sure how to interpret...a turbopump self-destructing, or ???

"engine pressure release" sounds synonymous to "explosion" to me. Maybe it wasn't a catastrophic explosion, but it definitely went out with a bang.

Think about it, if you were SpaceX, would you want to say that one of your engines "exploded"?

I'm fairly certain those terms are not in any way synonyms.
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Offline modemeagle

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #637 on: 10/08/2012 06:11 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.

Offline Ben the Space Brit

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #638 on: 10/08/2012 06:12 pm »
Any official word on the Orbcomm satellites?
And if the Orbcomm is in the wrong orbit, does it have enough manoeuvre capability in its own right to get to the correct orbit?

Increasing apogee and perigee to ~700km from ~230km? I would say "no" and "forget about it".  It was mounted on the second stage (although the Dragon's trunk was doubling as its PLF) and needed the M-Vac's power to reach its insertion orbit.
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Offline mduncan36

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Re: SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION
« Reply #639 on: 10/08/2012 06:13 pm »
"engine pressure release" sounds like they know something happened but not specifically what, yet. Give it a few days and things will become better defined.

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