SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION

[Comga]

F9 has a propellant utilization system which uses a fuel trim valve between the fuel pump and injector on each engine to do exactly what MP99 is suggesting.

Thank you.  That is the critical information.

Now the von Braun reference just said that it could be done.  However the link to that Popular Science from December 1964 was very interesting, as it also has  the first photo of the YA-12A, the predecessor to the SR-71 designation, and the XB-70A!

[meekGee]

Hey - does anyone here know where approximately the first stage remains ended up?   Or even where it started re-entering?

Does anyone know if there's ANY realistic chance of going to get it?

[Comga]

Hey - does anyone here know where approximately the first stage remains ended up?   Or even where it started re-entering?

Does anyone know if there's ANY realistic chance of going to get it?

By comparision, The S1C first stage that lofted Apollo 11, truly a historic treasure, has resisted a substantial effort at recovery by Jeff Bezos.  Falcon 9 #4 went farther north, is a much smaller target, and is much less worthy of a recovery effort.  It seems beyond consideration.   

[meekGee]

Hey - does anyone here know where approximately the first stage remains ended up?   Or even where it started re-entering?

Does anyone know if there's ANY realistic chance of going to get it?

By comparision, The S1C first stage that lofted Apollo 11, truly a historic treasure, has resisted a substantial effort at recovery by Jeff Bezos.  Falcon 9 #4 went farther north, is a much smaller target, and is much less worthy of a recovery effort.  It seems beyond consideration.   

Well, a lot of it has to do with the quality of tracking, and the depth of the ocean floor, right?  Was there a NOTAM (or some other appropriate keep-away notice) issued for the projected impact zone?

[rickl]

I thought I read somewhere that the F9 first stage impacts about 600 miles downrange.  Since I don't remember the source, there's no telling whether that's accurate or not.

A cursory glance at Google Earth puts it somewhere off the coast of North Carolina, in water about 8-10,000 feet deep.  I'm sure it could be done, but it would be expensive.  It would only make sense to try it if they can't figure out what happened from the telemetry.

[Mader Levap]

They may indeed be able to. I wouldn't count it out, yet. Remember how quickly they trimmed the nozzle?

They would be incredibly lucky if it was something as simple as that. I do not believe that. Will be fun to see guesses thrown at number of SpaceX launches in 2013...

Then again, if I were a betting man, I wouldn't bet anything on it happening in January, either. What is the current NET launch date for CRS-2?

Unfortunately, I know only month. I am not sure if precise date was set at all. And with what happened on CRS-1, it will probably be even more uncertain.

Isn't recovery effort futile? AFAIK each first stage went down in pieces.

[john smith 19]

Maybe the controller can adjust the mixture ratio, but that's about all that can be adjusted that I can see.  However, until someone knowlegeable says that rockets do this, I will remain highly skeptical.

RL-10s have done this for the last 50 years. The J2 or J2-S had it as well.

I don't think most US LOX/HC engines have had it but I'm not sure about the Russians.

[Antares]

If SpaceX were to perform a full-duration static test fire  on the pad before CRS SpX-2 (instead of the 3 second test fire) to help remove doubt about engine reliability, do those same engines still have enough rated life left for the actual mission?

Does a test fire of that length actually reduce their reliability for a second full-duration burn?

Production/flight items should not require more than one test to verify workmanship.  A second test is sometimes necessary to tune a component where performance is critical, but this is usually more important for second stage engines than 1st stage or where the tuning predictions may be uncertain.  Production items should see as little use as possible before flight but not zero.  Workmanship must be screened.

Even a single-engine RUD on the pad sounds like a really bad idea to me.

2. If this was a manned Dragon, would the mission have been aborted when the failure occured? I'm not sure of the Dragon abort system so I don't know if it would have been available at that time (i.e. jettisoned or rendered inactive).

Why do people ask questions about things that aren't designed yet?  This is why I don't even look at CCP and other development threads.

I'll note that due to propellants density changing due to temperature and atmospheric pressure it's normal to measure their loading by their mass.

No.  These are either measured by level sensors or dP transducers in the tanks (to get rho*g*h, then h yields volume) or by flowmeters/totalizers on the fill and drain lines which measure volume.  In either case, mass has to be inferred from volume and temperature.

if engine out capability is going to factor into man rating and crew survivability, does anyone really think NASA would allow that as a factor without seeing it in action more than once?

They did with Shuttle.  Many will raise holy he|| if NASA pulls a do-as-I-say-not-as-I-do.

[MP99]

Makes more sense to adjust the mixture ratio so that both reach their minimum levels (residuals) at the same moment.

No all engines can adjust the mixture ratio. But even if you could, there's some stochastic component to the amount of fuel left. And you want some reserves in case you have some slight under performance. What's more, an oxidizer rich shutdown might have catastrophic consequences. So, just in case, you bias towards an excess of fuel.

Agreed:-

However, I believe they'd always want to avoid an oxygen-rich shutdown, so there may be a deliberate policy to always have the lox run out slightly before the kero "just in case".

F9 has a propellant utilization system which uses a fuel trim valve between the fuel pump and injector on each engine to do exactly what MP99 is suggesting.

Thanks. BTW, in this launch video at T+0:57 "first stage propellant utilisation is active" is called out. They do same for second stage, though it's not on this video.

cheers, Martin

[meekGee]

Here's a wild unsubstantiated speculation that I didn't see on this thread before:  The fuel dome could have been damaged either in transport or during installation of the fairing corners.

This does not require a failure of either the specific acceptance test or the testing methodology.  (both of these options require both a flaw, and a test failure)

I think a handling error like this is at least as likely as something external failing in the rocket, and it's not difficult to create a fault that survives the 3 second pad test, but fails in 80.

No evidence for it whatsoever, but it should have been added to the list of option discussed earlier in the thread.

[edkyle99]

Not sure where to discuss this, but with the recent RL10 issue and this Merlin 1C/Falcon 9 failure, all of the large U.S. orbital launch vehicles are now out of action, pending investigation results, etc.  That may be it for 2012 for the U.S. side of the orbital launch ledger.

 - Ed Kyle

[sdsds]

F9 has a propellant utilization system which uses a fuel trim valve between the fuel pump and injector on each engine to do exactly what MP99 is suggesting.

So when this engine was acceptance tested, was it run with the fuel trim valve at a nominal setting, or was the setting varied up to its extremes? And to be clear, the trim valve is outside the fuel dome, right?

[ugordan]

and it's not difficult to create a fault that survives the 3 second pad test, but fails in 80.

I don't know how difficult that is, but it does make me wonder if SpaceX will rethink their strategy of performing pad hotfires before launch. This was the 2nd Merlin issue in the last two lauches that wasn't picked up by the hotfire, in fact the hotfire might have contributed to one of them (the failing check valve). ISTM they're not really getting much out of them, compared to just doing stage acceptance tests in McGregor.

[yg1968]

Not sure where to discuss this, but with the recent RL10 issue and this Merlin 1C/Falcon 9 failure, all of the large U.S. orbital launch vehicles are now out of action, pending investigation results, etc.  That may be it for 2012 for the U.S. side of the orbital launch ledger.

 - Ed Kyle

Orbital isn't grounded.

[sdsds]

ISTM they're not really getting much out of [hot fire tests on the pad], compared to just doing stage acceptance tests in McGregor.

They're getting assurance that nothing changed (i.e. was damaged) in transit. Couldn't even the nominal transport environment induce vibrations leading to trouble?

[Zed_Noir]

Not sure where to discuss this, but with the recent RL10 issue and this Merlin 1C/Falcon 9 failure, all of the large U.S. orbital launch vehicles are now out of action, pending investigation results, etc.  That may be it for 2012 for the U.S. side of the orbital launch ledger.

 - Ed Kyle

Orbital isn't grounded.

large U.S. orbital launch vehicle 

Maybe this should be posted in the US launch schedule thread.

In any case, there is only the AV 501 flight with the X-37B and the AV 401  flight with the TDRS-K left on the 2012 schedule. IMO the Antares Demo will slip to 2013.

[Robotbeat]

Antares isn't small... It's medium (by industry standards, I'd argue), in the Delta II class.

[Joffan]

Antares isn't small... It's medium (by industry standards, I'd argue), in the Delta II class.

It also isn't flying, yet. December for test flight, probably. Meanwhile, back to SpX-1....

[Robotbeat]

Antares isn't small... It's medium (by industry standards, I'd argue), in the Delta II class.

It also isn't flying, yet. December for test flight, probably. Meanwhile, back to SpX-1....

...but it isn't grounded.

[Kabloona]

ISTM they're not really getting much out of [hot fire tests on the pad], compared to just doing stage acceptance tests in McGregor.

They're getting assurance that nothing changed (i.e. was damaged) in transit. Couldn't even the nominal transport environment induce vibrations leading to trouble?

Plus, it does give them some schedule cushion if an engine or other component fails or goes out of spec on the pad test and needs to be changed, because it gets found a week or so ahead of launch, instead of on launch day.