Quote from: alexterrell on 10/08/2012 05:57 pmQuote from: MP99 on 10/08/2012 05:20 pmDepending 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 seconds5G limit engine out (8 drop to 7 engines): 191.6 secondsS1 MECO: 195.3 secondsSkipping 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.
Quote from: MP99 on 10/08/2012 05:20 pmDepending 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.
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.
However, due to an anomaly on one of the Falcon 9’s 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.
Quote from: rdale on 10/08/2012 06:01 pmShould 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.
Should we start a new thread full of apologies for those who guaranteed there was an explosion? Or just sweep that under the rug?
ORBCOMM press release in updates thread. Interesting bit:QuoteHowever, due to an anomaly on one of the Falcon 9’s 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.
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 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?
Quote from: joek on 10/08/2012 09:50 pmORBCOMM press release in updates thread. Interesting bit:QuoteHowever, due to an anomaly on one of the Falcon 9’s 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.
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.
Quote from: joek on 10/08/2012 09:50 pmORBCOMM press release in updates thread. Interesting bit:QuoteHowever, due to an anomaly on one of the Falcon 9’s 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"?
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.
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?
Quote from: mrmandias on 10/08/2012 07:52 pmQuote from: mduncan36 on 10/08/2012 07:37 pmAm 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.
Quote from: mduncan36 on 10/08/2012 07:37 pmAm 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.
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. "