Author Topic: SpaceX Falcon 9 v1.1 - SpX-6/CRS-6 DRAGON - Discussion Thread  (Read 502838 times)

Offline eriblo

  • Full Member
  • ****
  • Posts: 1367
  • Sweden
  • Liked: 1670
  • Likes Given: 270
And full deployment takes at least 2-3 seconds from previous videos. It might be a little unsymmetrical and likely represent the biggest change of aerodynamics since the stage went subsonic. Personally I wouldn't rule out a contribution to the need for the questioned "late maneuvering" (which might or might not have had extra control loop lag).
I disagree with your deployment time. It's more like 1.5 - 2s.
Quite possible, especially to more or less full extension. I was going of the ORBCOMM video which had that one leg which was slightly slower. They also appear to bounce around a bit before stiffening up at 4-5 seconds after deployment start, but that might just be due to the reduced airspeed/increased g-loads....

Offline spacetraveler

  • Full Member
  • ****
  • Posts: 687
  • Atlanta, GA
  • Liked: 165
  • Likes Given: 26
Also, somehow it looks like this stage is descending at a much faster rate at the end, compared to Grasshopper. Can't they spare a bit more fuel to slow the vertical descent just before the end?

It's like the equivalent of a guy screeching into his parking spot and slamming on the brakes.

That is what it is because no they can't spare more fuel for a slow easy descent, would impact payload capacity too much.

Offline OxCartMark

  • Full Member
  • ****
  • Posts: 1836
  • Former barge watcher now into water towers
  • Michigan
  • Liked: 2072
  • Likes Given: 1555
I'll walk back (as the Washington political commentators say) some of my previous statements on leg deploy-

- I said legs deploy 8 seconds before landing.  Kim Keller said 6 seconds.  Referring back to the playbook, it looks like 6.14 seconds (Kim's number) might be most correct, at least in a nominal situation.

- I still do believe that leg deployment being acted on by side wind isn't a likely culprit because its so easy to model and be prepared for.  But in the case of the legs deploying transiently assymmetrically I can see that having funky steering input.  But still, look at the engine steering input for the upper half of that video, its intentionally pushing the bottom to the left during that time, it shouldn't be a surprise that the base is off to the left.
Actulus Ferociter!

Offline cambrianera

  • Full Member
  • ****
  • Posts: 1438
  • Liked: 318
  • Likes Given: 261
Should be same position.
Oh to be young again. . .

Offline ugordan

  • Senior Member
  • *****
  • Posts: 8520
    • My mainly Cassini image gallery
  • Liked: 3543
  • Likes Given: 759
An attempt at some color correction on the single frame:

Offline Ohsin

  • Full Member
  • ****
  • Posts: 1469
  • Liked: 1453
  • Likes Given: 2379
An attempt at some color correction on the single frame:

I like the Tilt Shifty feel of this.
"Well, three cheers to Sharma, but our real baby is INSAT."

Offline JamesH

  • Full Member
  • ****
  • Posts: 525
  • United Kingdom
  • Liked: 284
  • Likes Given: 7


I'm still open to bet on this... 5 years from now, if a SpaceX barge is in service, it will be able to broadcast live video. Want to take that bet?

How high was F9 when they called acquisition of signal at the barge?

A drone at that height above the barge could transmit to the Cape, and other parts of the coast are closer / would need less height.

Cheers, Martin

I doubt a drone could carry enough power to transmit back 300miles. Not at any acceptable bit rate.

Offline TomH

  • Senior Member
  • *****
  • Posts: 2938
  • Vancouver, WA
  • Liked: 1868
  • Likes Given: 909
Also, somehow it looks like this stage is descending at a much faster rate at the end, compared to Grasshopper. Can't they spare a bit more fuel to slow the vertical descent just before the end?

It's like the equivalent of a guy screeching into his parking spot and slamming on the brakes.

That is what it is because no they can't spare more fuel for a slow easy descent, would impact payload capacity too much.

Controlling Grasshopper is easier than controlling a returning F9 stage 1 because Grasshopper is ballasted and can hover. The returning stage is so light that the T/W is significantly >1 even with the single Merlin 1D at minimum throttle. Grasshopper's ballast puts the point of T/W = 1.0 right in the middle of the throttle range, allowing the landing to be finessed like a helicopter pilot fine tuning his/her landing. The F9 first stage cannot hover. It has to come in at significant velocity with the M1D burning off that velocity very quickly and very precisely. The landing computer has to program the burn such that V = 0 and Altitude above pad = 0 occur at the exact same moment in time. If V = 0 occurs while the stage still has any altitude, it begins ascending again and cannot be stopped without full engine shutdown. The timing has to be perfect; you can't come to a hovering stop a couple of feet off the deck and then just ease her down. That would require a more deeply throttling engine or a lower power landing engine.

Offline kevin-rf

  • Elite Veteran
  • Senior Member
  • *****
  • Posts: 8823
  • Overlooking the path Mary's little Lamb took..
  • Liked: 1318
  • Likes Given: 306


I'm still open to bet on this... 5 years from now, if a SpaceX barge is in service, it will be able to broadcast live video. Want to take that bet?

How high was F9 when they called acquisition of signal at the barge?

A drone at that height above the barge could transmit to the Cape, and other parts of the coast are closer / would need less height.

Cheers, Martin

I doubt a drone could carry enough power to transmit back 300miles. Not at any acceptable bit rate.

Depends on the size of the drone ;) The US DOD seems to do just fine transmitting full motion video and data over longer distances. They just have very deep pockets ;)
If you're happy and you know it,
It's your med's!

Offline Nilof

  • Full Member
  • ****
  • Posts: 1177
  • Liked: 597
  • Likes Given: 707


I'm still open to bet on this... 5 years from now, if a SpaceX barge is in service, it will be able to broadcast live video. Want to take that bet?

How high was F9 when they called acquisition of signal at the barge?

A drone at that height above the barge could transmit to the Cape, and other parts of the coast are closer / would need less height.

Cheers, Martin

I doubt a drone could carry enough power to transmit back 300miles. Not at any acceptable bit rate.

Didn't we get exactly that on the Orion flight test?
For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v.   Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

Offline Ohsin

  • Full Member
  • ****
  • Posts: 1469
  • Liked: 1453
  • Likes Given: 2379


 :)

Edit: Attaching as its 'private' again.
« Last Edit: 04/15/2015 08:36 pm by Ohsin »
"Well, three cheers to Sharma, but our real baby is INSAT."

Offline matthewkantar

  • Senior Member
  • *****
  • Posts: 2076
  • Liked: 2506
  • Likes Given: 2211
Excited to see the barge after that detonation. Very excited to see this video, thought we would get only the Vine.

Matthew
« Last Edit: 04/15/2015 08:28 pm by matthewkantar »

Offline kevinof

  • Full Member
  • ****
  • Posts: 1594
  • Somewhere on the boat
  • Liked: 1869
  • Likes Given: 1262
oh man oh man. that was soooo close.



 :)

Offline Chris Bergin

We have a slightly longer version in L2, where one of the COPV bottles said "No way, I want to go back uphill!" ;D

GO COPV BOTTLE! GO!
Support NSF via L2 -- Help improve NSF -- Site Rules/Feedback/Updates
**Not a L2 member? Whitelist this forum in your adblocker to support the site and ensure full functionality.**

Offline schaban

  • Full Member
  • *
  • Posts: 180
  • Liked: 53
  • Likes Given: 132
I don't remember falcon oscillating that much on previous landings. Really starts looking like some kind of control mechanism failure...

Offline CuddlyRocket

Doesn't look like much of the first stage was left on deck; the explosion blowing the engines off one side and the tank the other!

Offline Lars-J

  • Senior Member
  • *****
  • Posts: 6809
  • California
  • Liked: 8485
  • Likes Given: 5384


 :)

Wow... Amazing quality.  :o Those RCS thrusters keep firing, not giving up. So close.

The barge is collecting its fair share of battle scars.

EDIT - And the video is now private. I guess it was not supposed to be released yet. Somebody leaked a link they were not supposed to...
« Last Edit: 04/15/2015 08:33 pm by Lars-J »

Offline RotoSequence

  • Senior Member
  • *****
  • Posts: 2208
  • Liked: 2068
  • Likes Given: 1535
Don't refresh your pages if you were/are still able to watch it; the landing video's been made private.  :(

Offline notsorandom

  • Full Member
  • ****
  • Posts: 1740
  • Ohio
  • Liked: 438
  • Likes Given: 91


 :)

Wow... Amazing quality.  :o Those RCS thrusters keep firing, not giving up. So close.

The barge is collecting its fair share of battle scars.
The thrusters firing like that to keep the rocket pointed up reminds me of a number of moments in Kerbal. They must pack quite a punch because it looks like they did hold the rocket up for a few moments.

Offline Chris Bergin

Video went private. Too bad some of us download them as soon as we can :D

It will have been reuploaded by 1001 accounts already. Best someone links one of those and not eat up bandwidth here if that goes into the thousands of downloads.
« Last Edit: 04/15/2015 08:41 pm by Chris Bergin »
Support NSF via L2 -- Help improve NSF -- Site Rules/Feedback/Updates
**Not a L2 member? Whitelist this forum in your adblocker to support the site and ensure full functionality.**

Tags: CRS-6 
 

Advertisement NovaTech
Advertisement Northrop Grumman
Advertisement
Advertisement Margaritaville Beach Resort South Padre Island
Advertisement Brady Kenniston
Advertisement NextSpaceflight
Advertisement Nathan Barker Photography
1