SpaceX COTS Demo 2/3 Updates (THREAD 2)

[beancounter]

Then SpaceX is the one being conservative?

7.5% of total payload capability to LEO and an instantaneous launch window only when plane and phase angle is at a minimum... That isn't conservatism, it is a problem...

No, it's only a problem if they can't launch.

[Galactic Penguin SST]

Well, I thought that the Soyuz and Progress were launched under instantaneous windows, and yet no one spoke of the "performance shortfall" of the Soyuz rocket.... 

[QuantumG]

Well, I thought that the Soyuz and Progress were launched under instantaneous windows, and yet no one spoke of the "performance shortfall" of the Soyuz rocket.... 

I'm not sure what the roll eyes emoticon is supposed to indicate here. The inclination of the ISS is because of the performance shortfall of the Soyuz rocket.

[jedsmd]

It is odd that Spacex pushed so hard to combine launching two ORBCOMM satellites with the C2/C3 flight if they have near zero margin.

[Robotbeat]

It is odd that Spacex pushed so hard to combine launching two ORBCOMM satellites with the C2/C3 flight if they have near zero margin.

Yeah, I don't think it's been firmly established that they have near zero margin.

[yg1968]

It is odd that Spacex pushed so hard to combine launching two ORBCOMM satellites with the C2/C3 flight if they have near zero margin.

Yeah, I don't think it's been firmly established that they have near zero margin.

It's pure speculation by SpaceX detractors.

[Antares]

Or maybe they thought about it some more and realized that it makes sense to keep as much prop on board Dragon as they can in case they have to abort an on-orbit test and want to be able to fix the problem and try again.  Having a massively constrained launch window is probably still cheaper than having to launch another Dragon-Falcon stack.  Having tridaily launch attempts actually keeps the ops folks happier since one doesn't have to amp up for attempts on multiple days in a row.  As far as usability once operational, I would think that the Demo will establish an initial prop margin for the Dracos, one that's conservative and can be partially retired with more data points.  At least that's how the experienced folks do it.

Now, if the operational windows are this bad, then it's time to worry.

[beancounter]

Or maybe they thought about it some more and realized that it makes sense to keep as much prop on board Dragon as they can in case they have to abort an on-orbit test and want to be able to fix the problem and try again.  Having a massively constrained launch window is probably still cheaper than having to launch another Dragon-Falcon stack.  Having tridaily launch attempts actually keeps the ops folks happier since one doesn't have to amp up for attempts on multiple days in a row.  As far as usability once operational, I would think that the Demo will establish an initial prop margin for the Dracos, one that's conservative and can be partially retired with more data points.  At least that's how the experienced folks do it.

Now, if the operational windows are this bad, then it's time to worry.

I can't see that performance margins are the issue.  The Dragon is hardly launching with full-up mass even if it is carrying a full propellant load and they surely haven't come this far on the Merlin 1C is it wasn't up to the job so there must be some other constraint operating.

[cuddihy]

Since Progress and Soyuz are apparently in the same boat, how does shuttle and ATV compare?

Update - for ATV 1 and 2 at least it was instantaneous. Same for HTV-1. So i'm at a loss as to how this is a negative for SpaceX. Apparently every ISS supply vehicle still flying has this restriction.

[Robotbeat]

Or maybe they thought about it some more and realized that it makes sense to keep as much prop on board Dragon as they can in case they have to abort an on-orbit test and want to be able to fix the problem and try again.  Having a massively constrained launch window is probably still cheaper than having to launch another Dragon-Falcon stack.  Having tridaily launch attempts actually keeps the ops folks happier since one doesn't have to amp up for attempts on multiple days in a row.  As far as usability once operational, I would think that the Demo will establish an initial prop margin for the Dracos, one that's conservative and can be partially retired with more data points.  At least that's how the experienced folks do it.

Now, if the operational windows are this bad, then it's time to worry.

+1

[ugordan]

Unless it wasn't a prediction.

Pretty sure it wasn't merely a "prediction"... Word gets around and besides, other parts of NASA like the Launch Services Program is kept in the know about Falcon 9 because it's one of the vehicles available per the NLS II contract, even though the COTS/CRS launches have nothing to do with them.

I wonder if we'll see a direct insertion or a two burn profile on this mission...

[douglas100]

Since Progress and Soyuz are apparently in the same boat, how does shuttle and ATV compare?

Update - for ATV 1 and 2 at least it was instantaneous. Same for HTV-1. So i'm at a loss as to how this is a negative for SpaceX. Apparently every ISS supply vehicle still flying has this restriction.

I thought Soyuz had a launch window of about 30 seconds-probably wrong there. But I can't think of an instance when a Soyuz or Progress missed its launch window for ISS. Until this discussion started I just assumed that F9 would have to operate in the same way. It never occurred to me that an instantaneous launch window was an indication of under performance.

So I'll go along with Antares' assessment. (I'm an amateur so I'm not going to argue with him! 

[Ben the Space Brit]

If Merlin-1c's performance is at the low end of estimates, as Jim's mocking smily suggests, then this explains the rush to get the first Merlin-1d prototypes flying ASAP - It is unlikely that SpaceX will be able to fulfill certain contracts without it.

[Kabloona]

I expect Antares is correct. A lot riding on this for SpaceX, and the conservative thing to do is preserve maximum prop margin for contingency ops. Penalty for a 3- day recycle is trivial; penalty for failed mission is non-trivial.

[go4mars]

If Merlin-1c's performance is at the low end of estimates, as Jim's mocking smily suggests...

Brevity is the soul of misinterpretation.  Maybe it says something about how my mind works, but I thought it was a bedroom joke.

Further indication of performance issues?

;-)

 

[clarkeo]

More Expansive quotes from Gwynne Shotwell curteousy of Jeff Foust....

“I’m happy to say we have a launch date scheduled on the range and a berthing date with the ISS,”

She added that the launch window on the 30th is “almost an instantaneous window”

Two bits of good news I think, firstly it seems like the launch date is a confirmed date aka not a NET date. Also that its an "almost instantaneous" window I think that's a turn of phrase to indicate that they have to get it off without a hitch aka no chance for a recycle in each of the windows. From the other quotes in the article she seems to be trying to limit the anticipation a bit and suggest its not a big deal if they dont get it off on the first try so people don't get too disappointed. She also seems a lot more concerned about mission success rather than timeline as was pointed out by SpaceflightNow in a recent article there's a big budget fight ahead for commercial and its essential that SpaceX succeed I imagine thats a cause of a lot of the delays pressure on NASA which is then placed on SpaceX that may not have been there if congress was more accepting of commercial space. It seems failure is not an option the stakes for the whole industry are too high.

http://www.newspacejournal.com/2012/03/14/spacex-planning-for-april-30-dragon-launch/

[ugordan]

Two bits of good news I think, firstly it seems like the launch date is a confirmed date aka not a NET date.

Right... As per Florida Today "NASA says no official target date will be set until a flight readiness review now planned April 12. "

http://www.floridatoday.com/article/20120313/SPACE/120313021/SpaceX-targeting-April-30-launch-Dragon-ISS

[Namechange User]

Two bits of good news I think, firstly it seems like the launch date is a confirmed date aka not a NET date.

Right... As per Florida Today "NASA says no official target date will be set until a flight readiness review now planned April 12. "

http://www.floridatoday.com/article/20120313/SPACE/120313021/SpaceX-targeting-April-30-launch-Dragon-ISS

That's a formaility.  While true no "official" date will be set until the FRR is over, there is a date. 

There has to be in order to schedule the range, schedule the FRR, etc.  So in other words all the planning and activity to get to a launch date actually requires a launch date to be known. 

[ugordan]

Yes, but until that FRR goes satisfactorily, the April 30 date is as "concrete" as the Feb 7 date was. Really not worth getting excited about it yet.

[Namechange User]

Yes, but until that FRR goes satisfactorily, the April 30 date is as "concrete" as the Feb 7 date was. Really not worth getting excited about it yet.

If convention holds, and it may not given it is SpaceX and their tendancy to not advertise much on current status, if the FRR happens then that in itself is indication the launch date will hold.

It is rare, unless there is a last minute major issue, that the FRR would be held and then a new slip announced.