SpaceX Falcon 9/Dragon COTS Demo (C2+) GENERAL DISCUSSION

[Jorge]

I don't believe trunk items are headed indoors at all.

Correct no cargo in trunk, they are just going to do a try run with the Dextre to make sure that it could recover payload/load trash into the trunk.

I understand that this flight doesnt have "stuff", but what about future flights?  and will future flights have stuff that needs to be brought inside or sent back in the trunk? so how do they plan on getting it in and out of the ISS?

Seems simpler to me to keep stuff headed inside ISS in the capsule and reserve the trunk for the stuff headed outside.

[manboy]

I remember watching the launches of Mercury and Gemini. Almost every launch attempt was aborted to come back again another day and try again. SpaceX is having it's growing pains but to date none of the aborts appear to be for causes as serious as those early days in the 1960's. Assuming the preliminary analysis holds and Range agrees, we'll all be back here about an hour earlier next Tuesday to do this again.

I remember listening to Neil talk about Apollo 11 and about how he was a little surprised when they actually launched.

[Steve_the_Deev]

Most likely it was due to a slight spike at start up which due to conservative LCC (like we had on the Shuttle SSME vlvs early on) may be the cause for the Hot Fire Abort.  It could be pure instrumentation.  Transducers can fail "off scale high" or "low" depending on its design/application.  R&R of a Xducer is much nicer than an  engine!  Another thing they can do is if it was due to a spike, that is understood for that engine, change the LCC if it still allows safe engine margins.

[Chris-A]

The media headlines don't seem to be too pleasing right now.

[Steve_the_Deev]

I am pretty sure the Dragon is carrying some supplies such as water, some batteries for instruments, some food items and other "safe" items. 

[psloss]

Most likely it was due to a slight spike at start up which due to conservative LCC (like we had on the Shuttle SSME vlvs early on) may be the cause for the Hot Fire Abort.  It could be pure instrumentation.  Transducers can fail "off scale high" or "low" depending on its design/application.  R&R of a Xducer is much nicer than an  engine!  Another thing they can do is if it was due to a spike, that is understood for that engine, change the LCC if it still allows safe engine margins.

Is it possible that engine was a slightly slow starter?

I seem to recall reading posts here talking about how getting start transients right was kind of "black magic."

[psloss]

The media headlines don't seem to be too pleasing right now.

That's normal, unfortunately; the automatic 72-hr turnaround probably doesn't help with the mood.  (I feel bad for all the folks that had to travel pre-launch...but there's that old line -- "You knew the job was dangerous when you took it, Fred.")

[Antares]

I seem to recall reading posts here talking about how getting start transients right was kind of "black magic."

Yeah, but if the engines are qualified, they should be tightly controlled and predictable - especially if there are 9 of them that have to be in limits to lift off.

[psloss]

I seem to recall reading posts here talking about how getting start transients right was kind of "black magic."

Yeah, but if the engines are qualified, they should be tightly controlled and predictable - especially if there are 9 of them that have to be in limits to lift off.

It will be interesting to see if anyone gets into this area of questioning in the briefing.

[Nahavandi]

[Jim]

Also, while I'm at bugging people; can anyone clarify how instantaneous the instantaneous launch window is? And is it because Falcon/Dragon carries lesser propellant for delta-v's than the shuttle?

Instantaneous is one second.  It is because Spacex wants to have as much spacecraft propellant onboard as possible. Which means launch vehicle performance needs to be as high as possible and it can't use propellant yaw steering for non optimal launch times.

[krytek]

Also, while I'm at bugging people; can anyone clarify how instantaneous the instantaneous launch window is? And is it because Falcon/Dragon carries lesser propellant for delta-v's than the shuttle?

Instantaneous is one second.  It is because Spacex wants to have as much spacecraft propellant onboard as possible. Which means launch vehicle performance needs to be as high as possible and it can't use propellant yaw steering for non optimal launch times.

I'm paraphrasing here but Gwynne basically said that it's not as "instantaneous" as a planetary launch, but it's very very tight.

It's a bit OT but do you think next year's F9 v1.1 will allow for a much larger window?

[ugordan]

It's a bit OT but do you think next year's F9 v1.1 will allow for a much larger window?

Larger (as in minutes), but that's still useless for anything but catching a hole in the clouds, waiting for a boat to clear the range that extra couple of minutes, etc. Any technical issues such as this would result in a scrub.

[Jim]

I just looked at the Launch Commit Criteria live-status snapshot on the other updates thread, and happened to notice that Tribo was N/A for this launch. Now my understanding WAS that this is a Range safety constraint, and tribo-electric interference might result in "jamming" of a destruct signal in case of a mal. Therefore, it's an issue for unmanned spacecraft, but obviously not for manned spacecraft, since a) The crew would have to first exit b) They would be able to activate such systems from on-board anyway.

Now, what's poking holes in that is a) Challenger's post break-up detonation from the ground by RSO and b) that it's N/A for this launch.

Now I'm starting to think that Tribo issues depend (amongst a few other things) on the trajectory, and speed - and a craft that's man-rated (limited g-loading, max-Q, etc.) doesn't reach the conditions necessary for significant trio-electrification issues to crop up. Would any meteorologists clarify? Thanks (and sorry for the length )

No, it isn't manned vs unmanned.  Destruct for manned is done the same way as unmanned.  trio-electrification has to do with vehicle design and shape.  Falcon and Dragon don't have a large surface area (such as an 86 foot fairing or inert upperstage) ahead of the transmitters to build up charge. And there are design mitigation steps (like conductive paint, embedded conductive paths, etc)  that can be taken to prevent it.

[Galactic Penguin SST]

Sorry, but I can't resist posting someone's reaction to the scrub: a clear cut case of launchis interruptus. 

[ugordan]

Gwynne Shotwell speculated that the high Pc on engine #5 could have been due to oxygen rich combustion leading to higher temperature and thus higher pressure.

Do combustion chambers typically have temperature sensors or just pressure transducers?

[plank]

Sorry, but I can't resist posting someone's reaction to the scrub: a clear cut case of launchis interruptus. 

Poor OT no worries the U.S. will get into space again someday.

[Mapperuo]

Sorry, but I can't resist posting someone's reaction to the scrub: a clear cut case of launchis interruptus. 

I'd like to laugh, but I was probably very similar. 

[brihath]

The media headlines don't seem to be too pleasing right now.

That coverage is probably by people who have no understanding of what is going on.  The female talking head on Fox News this morning said everyone at SpaceX was "depressed".  Really??  I got none of that from Gwen Shotwell this morning at the press conference.  Now if they launched and lost the vehicle, it would probably be different.

As a matter of fact, one reporter mentioned failure and she came back and said it is not a failure.  It is an abort.  Everything worked the way it was supposed to and saved the vehicle.

[Robotbeat]

Gwynne Shotwell speculated that the high Pc on engine #5 could have been due to oxygen rich combustion leading to higher temperature and thus higher pressure.

Do combustion chambers typically have temperature sensors or just pressure transducers?

Both.