SpaceX Falcon 9 v1.1 - Jason 3 - SLC-4E Vandenberg - Jan 17, 2016 - DISCUSSION

[Damon Hill]

I often watch events on Spaceflightnow.com for live video, but the site's been 'broken' for about ten minutes.  Nasaspaceflight.com went down for a couple of minutes but I'm getting it now.   SpaceX's feed is intermittent.  Could be an issue at my end, but I think we kind of broke the Internet for this launch/landing!

[hrissan]

I am surprised they didn't mention explosion along with the broken leg.  If it was low energy enough, or had low enough fuel to not explode when the leg broke, I would be presently surprised.  Estimating the vertical landing height in 15' seas even with the stabilization they have on JRTI has to be really hard.

If they vented the tanks as soon as the engine stopped, then I presume during 10 seconds of toppling the stage would become soft enough to not explode, but collapse on the deck after it falls?

[rsnellenberger]

Worth noting that a known problem with the 1.1's was slow valves in the engines. This was fixed with FT's. Combine that with rough seas, the odds were against them to start, this is just another great opportunity to gather boost back and landing data.

Good point....

[mfck]

Ab solutely WICKED soundtrack on the Webcast now. 

[NovaSilisko]

On the bright side, now I can stop worrying about what they're going to do with an outdated v1.1 first stage.

[Lars-J]

Wow, the raised apogee of this transfer orbit really is apparent now - stage 2 is gaining quite a bit of altitude over the Antarctic seas.

[Zach Swena]

Or, since it was a digital uplink, there was a big video buffer so we lost signal before the buffer was cleared. Good argument for either an analog uplink (secondary, perhaps) or a custom small-buffer digital uplink.

They may have a couple second delay.  They wouldn't have to use custom digital uplinks, just broadcast grade.  There is a huge cost differential between broadcast grade real time and typical internet type encoders and webcams though.  I am hoping we have enough info from whatever video they post to theory craft as to why it broke when it did.  That was pretty heavy seas for a landing though.

[JamesH]

broken leg, again, due to hard landing. There will be those calling the droneship strategy into question, of course.

True, but there already are.  The best part being it is all hot air with no chance of stopping SpaceX from trying again.

Exactly.

If the vid shows that the barge WAS pitching badly but the stage came in much closer to upright with less slew, just still hit one leg first, harder, it means this probably IS solvable, just needs control algorithm refinement.  And as was said, even 1 in 10 is better than 0 in 10 as long as it doesn't cost too much... think of it as lottery. Except the odds will get better.

now to see how I did in bingo

I dunno.. Not sure extra control would fix it - the stage needs to land at same angle, or very close to same angle, as the deck. Looking at the sea state, I was surprised how much the barge was actually moving. It would easily be a couple of meters higher at first leg touchdown, and travelling upwards, which is also going to be a tough one to solve. Unless you wait to launch until sea state is sane, which seems to obvious approach.

[meekGee]

broken leg, again, due to hard landing. There will be those calling the droneship strategy into question, of course.

True, but there already are.  The best part being it is all hot air with no chance of stopping SpaceX from trying again.

Right, but a pressurized tank of that size is surprisingly potent, even though it's "just" compressed gas.

[mvpel]

There was a lot of pitching visible on the video feed.

There was less rolling than it appeared - the key point of reference is the sky, not the ocean surface, thanks to the Thrustmasters. If you keep your eye on the point at which the jet of water intersects the bright spot in the sky behind it, that'll tell you how hard the Thrustmasters were working to keep things steady.

[vanoord]

Am I right in thinking that the thrusters maintain position and orientation but can't control pitching and rolling?

I'd imagine that pitch / roll control would be virtually impossible to correct without basing the landing platform on something like a floating drilling platform - like Sea Launch - to gain stability in these sort of seas.

Perhaps the investment would be worth it, but I can't see that decision being made until a couple of stages have been recovered onto the current design ASDS platform in good conditions.

[Robotbeat]

Worth noting that a known problem with the 1.1's was slow valves in the engines. This was fixed with FT's. Combine that with rough seas, the odds were against them to start, this is just another great opportunity to gather boost back and landing data.

Good point....

Not a good point. It was a /defect/ that caused the slow valves, so it would've been fixed on this flight.

[OxCartMark]

Just out of curiosity, is the parking orbit stable? And how much delta-v is needed to get into final orbit? And how much delta-v does Jason-3 have on-board?

  The delta v will be provided by F9, not the satellite.  After the 2nd burn of the F9 2nd stage Jason is in its orbit.

Independent of SpaceX's confirmation of the leg breaking (and almost certain kaboomness) I think the video was taken out a few seconds before then.  The ASDS stream had multiple outages for me in the minutes leading up to the event but none of those outages were longer than 1 second.  When the final outage came it was multiple seconds before the stage would have impacted the landing portion of the deck.  Since SpaceX seems to be saying it had a hard landing in more or less the normal spot it probably didn't directly contact the video or uplink equipment (before the kaboom at least).  So I'm of the theory that when we saw the orange glow on the opposite blast wall some of that equipment was simultaneously taken out by exhaust blast from more or less directly overhead.  Then maybe 5 seconds later the hard landing on the deck.

[wannamoonbase]

Worth noting that a known problem with the 1.1's was slow valves in the engines. This was fixed with FT's. Combine that with rough seas, the odds were against them to start, this is just another great opportunity to gather boost back and landing data.

They have done a great on getting targeting down.  One step at a time. 

[Robotbeat]

Just out of curiosity, is the parking orbit stable? And how much delta-v is needed to get into final orbit? And how much delta-v does Jason-3 have on-board?

  The delta v will be provided by F9, not the satellite.  ...

You don't say!
Of course, /nominally/ F9 upper stage provides the final delta-v. That was not my question.

Pet peeve: when you ask a carefully worded question, but someone (who doesn't know the actual answer) responds, making an excuse as to why they're not actually answering your question.

[NovaSilisko]

I see the landing failure as a consequence of the barge's variable altitude, rather than attitude. The rocket is trying to reach a very specific altitude above a very specific position while simultaniously bringing it's velocity to 0. The barge, meanwhile, moves up and down. I believe I saw the sea state as 12 feet earlier, so that means at its peak, the barge could very well have been 6 feet above the nominal altitude, which means... crunch.

[Joel]

If the vid shows that the barge WAS pitching badly but the stage came in much closer to upright with less slew, just still hit one leg first, harder, it means this probably IS solvable, just needs control algorithm refinement.

I wonder if the landing control algorithm is predictive, that is using a model for how the drone ship movements and/or wind disturbances will evolve the next couple of seconds.

[RotoSequence]

I've been thinking for a while that SpaceX needs something closer to an offshore drilling platform than a barge. With respect to timing the Falcon 9's hover-slam, it seems that the landing platform basically needs to be inert, rather than pitching and rolling with the seas.

[DaveS]

Anyone if the F9 1st stage landing legs has any form of shock absorption? If not, then I think they're just asking too much of the landing legs. They will break very easily as they're very stiff and rigid.

[fatdeeman]

So, assuming it tipped over but didn't explode how do they safely approach the rocket now? Are they able to tell if the stage has vented and isn't at risk of exploding? Reminds me of how you should never return to a lit firework but on a much larger scale.