SpaceX Falcon 9 v1.1 - Dragon - CRS-5/SpX-5 -Jan. 10, 2015 - DISCUSSION

[Xspace_engineerX]

Someone on the reddit thread for the recent article mentioned fins on this launch. Can anyone confirm that?

[TripD]

Someone on the reddit thread for the recent article mentioned fins on this launch. Can anyone confirm that?

As in grid fins?   That would be wild to see them in real action.

[Dudely]

Someone on the reddit thread for the recent article mentioned fins on this launch. Can anyone confirm that?

I think they were just speculating.

Honestly, I would be somewhat surprised if grid fins were on it. But it would be rad.

[Kim Keller]

Someone on the reddit thread for the recent article mentioned fins on this launch. Can anyone confirm that?

I can't confirm it, but I have seen some clues that suggest it.

[rcoppola]

Someone on the reddit thread for the recent article mentioned fins on this launch. Can anyone confirm that?

I can't confirm it, but I have seen some clues that suggest it.

And what might those clues be?

[Prober]

Someone on the reddit thread for the recent article mentioned fins on this launch. Can anyone confirm that?

I can't confirm it, but I have seen some clues that suggest it.

thought it was a "given" from the pr dept. some months ago.

[Kim Keller]

Someone on the reddit thread for the recent article mentioned fins on this launch. Can anyone confirm that?

I can't confirm it, but I have seen some clues that suggest it.

And what might those clues be?

Notes I've read here and there.

[Kim Keller]

Someone on the reddit thread for the recent article mentioned fins on this launch. Can anyone confirm that?

I can't confirm it, but I have seen some clues that suggest it.

thought it was a "given" from the pr dept. some months ago.

Don't know; maybe they did and I missed it.

[yg1968]

Someone on the reddit thread for the recent article mentioned fins on this launch. Can anyone confirm that?

I can't confirm it, but I have seen some clues that suggest it.

thought it was a "given" from the pr dept. some months ago.

I don't recall hearing that. It was mentioned as a strong possibility on L2 a while ago but was never officially confirmed.

[Ben the Space Brit]

OK, so L2 has the NET target now looking at the second half of December.

I'm not posting the NET date and back up dates in here (public) just yet as I did ask SpaceX and they said they don't have a firm NET just yet, so the new NETs may still change....SpaceX did say when they know for sure, they'll let us know.

Also remember, December 9 was always a planning date, one that became very much subject to change via the noted impact of NASA working out priority stuff to go uphill, following the loss of Cygnus CRS-3.

I'm posting the above at least, as I know a lot of people are planning on going to the launch and need to be aware if they are booking flights, etc.

This also gives SpaceX more time to do the Pad Abort, although I think that has been postponed in all but official announcement now.

[jaufgang]

Seems strange to me that they're first using these grid fins on the same launch where they've got everyone watching to see if they can accurately target a landing barge.   

The only flight data they have on the performance of those fins are from low altitude and low velocity manoeuvring on the F9R-Dev.  They have very little data on how they will perform during a high velocity re-entry. 

I would have expected them to first try them out and collect characterization data during a high altitude/velocity test of the F9R-Dev, or perhaps on one of their earlier hail-Mary soft splashdowns in the big wide ocean.  They could have performed a series of manoeuvres on the fins during various phases of the descent without caring if it sent the trajectory just a little bit off course, and used the collected data to refine the control system.

I suppose they're just really confident in their computer modelling.

[rpapo]

Or perhaps that is a portion of those 50/50 odds.

[mme]

Seems strange to me that they're first using these grid fins on the same launch where they've got everyone watching to see if they can accurately target a landing barge.   

...  They could have performed a series of manoeuvres on the fins during various phases of the descent without caring if it sent the trajectory just a little bit off course, and used the collected data to refine the control system.

I suppose they're just really confident in their computer modelling.

I suspect they are tired of waiting for Spaceport America.  And the only reason to wait would be fear of failure, but they aren't afraid of failing because it doesn't impact the mission and it's a great opportunity to collect data and learn.

I can accept failure, everyone fails at something. But I can't accept not trying.

-- Michael Jordan

[MattMason]

The new December 16 launch is also much earlier: 2:30 PM or so. This makes a greater visual opportunity for the barge landing attempt than the twilight landing planned on the 12/9 landing.

Do we have any information on what manned or unmanned cameras may be in the vicinity of the barge? I suspect they'll establish a safe zone for crewed boats but hopefully they'll have a good uncrewed camera solution.

[Herb Schaltegger]

Seems strange to me that they're first using these grid fins on the same launch where they've got everyone watching to see if they can accurately target a landing barge.   

The only flight data they have on the performance of those fins are from low altitude and low velocity manoeuvring on the F9R-Dev.  They have very little data on how they will perform during a high velocity re-entry. 

Just playing devil's advocate here, but what makes you think they'll be used at all during re-entry? I suspect they'll stay safely stowed flat until terminal velocity, or at most used with very, very, small deflections until very late in the landing sequence.

[rcoppola]

They must have massive amounts of hypersonic, supersonic and subsonic return data at this point. Which they have no doubt cycled back into their "Return" modeling with Grid Fins added. After all, as for return, this is still a test, so they're going to go...well...test.

Ironically, for anyone concerned they are introducing something new for this well publicized event, it may very well be, that their models show they can't hit a target 300ftx170ft "without" adding grid-fins.

[rcoppola]

Seems strange to me that they're first using these grid fins on the same launch where they've got everyone watching to see if they can accurately target a landing barge.   

The only flight data they have on the performance of those fins are from low altitude and low velocity manoeuvring on the F9R-Dev.  They have very little data on how they will perform during a high velocity re-entry. 

Just playing devil's advocate here, but what makes you think they'll be used at all during re-entry? I suspect they'll stay safely stowed flat until terminal velocity, or at most used with very, very, small deflections until very late in the landing sequence.

HA. So reminiscent of when we were all contemplating at what point during reentry they would deploy the landing legs. Dare I say another poll? "When will the Grid Fins be deployed...?" Just kidding.

[jaufgang]

Just playing devil's advocate here, but what makes you think they'll be used at all during re-entry? I suspect they'll stay safely stowed flat until terminal velocity, or at most used with very, very, small deflections until very late in the landing sequence.

I admittedly don't know where in the descent profile the grid fins will be used, and I do expect it to be highly unlikely that they would be deployed while the stage is hitting the dense atmosphere at supersonic velocities so maybe "re-entry" was the wrong phrase to use.

But even deploying them at terminal velocity would be radically different from the conditions under which they've been previously tested, which was an extremely low velocity descent at a few hundred meters altitude. 

They must have massive amounts of hypersonic, supersonic and subsonic return data at this point. Which they have no doubt cycled back into their "Return" modeling with Grid Fins added. After all, as for return, this is still a test, so they're going to go...well...test.

Ironically, for anyone concerned they are introducing something new for this well publicized event, it may very well be, that their models show they can't hit a target 300ftx170ft "without" adding grid-fins.

That's what surprises me...  I would have expected that their telemetry shows that their previous landing accuracy was good enough to hit the target, otherwise they wouldn't be towing this barge out there to land on.  And if that is the case it would seem like adding a new barely tested control system would actually add  risk rather than mitigate it.

But maybe that's a false assumption.  As far as I know they've never published or stated publicly how accurate the previous "water landings" were relative to their target coordinates, but I thought Elon had implied that they had achieved enough accuracy to make the barge landing a reasonable proposition. 

Maybe its just not the case that a deliberate decision was made to attempt the first barge landing and test the grid fins on the same flight.  Perhaps it just worked out that the two systems became ready for testing around the same time.  So they're testing the gird fins out because they need them to try to get the accuracy high enough to hit the barge, and sending the barge out to catch it just in case they get it right on the first try with the fins. 

Either way, it will be fun to watch.

[Lars-J]

Presumably they have more confidence in their data than you do.

[llanitedave]

It's not the data, it's the modeling.