SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION

[yokem55]

So, did the first stage have enough control left to deliberately divert to the ocean, or was the original trajectory to the ocean with a planned divert to the landing pad only if all was ok?

All evidence, including visual, from previous missions suggest it flies a lifting entry from after  reentry burn till landing burn. Once 3-axis control was lost, the lift was lost as well.

Frankly, I'm surprised the AFTS didn't terminate and it still executed a soft landing off shore.

An AFTS termination could have been more dangerous (in terms of debris risk) than just letting it attempt a soft splashdown. As long as the vehicle was remaining on a safe vector, letting it get lower and lower and do it's thing was improving the safety of the situation.

[dlapine]

Latest Elon tweet update-

"Pump is single string. Some landing systems are not redundant, as landing is considered ground safety critical, but not mission critical. Given this event, we will likely add a backup pump & lines."

[EnigmaSCADA]

I think I'll pass on a that PTP vacation unless I'm diagnosed with something inoperable/terminal with less than 6 weeks to live.

Almost needed a Dramamine watching on YouTube.

[jtrame]

At what point when you don't have complete control of your rocket flying back toward land does range safety kick in? While i'm sure they are happy they got their rocket back (albeit a little wet) I expect we will need to be asking some questions about whether the automated flight termination system worked as it was designed - and if it did - who didn't trigger a manual termination and why not? Dangerous as hell.

Why would they blow the rocket up when the trajectory was in the ocean?

This area offshore was cleared of traffic way before the flight, right?

[sghill]

Everyday Astronaut played a video of it a few minutes ago. Looked wild and then much calmer as landing burn started.

It looked like the leg deploy reduced the roll quite swiftly, much like an ice skater but aerodynamic drag may have slowed it more than the shifting weight.

As it slowed down, the stuck grid fins would have less authority (because there is not as much air flowing through them) and the RCS would have more authority. Makes sense that it looked more stable right as it neared a dead stop.

[OxCartMark]

Elon Musk twitter

‏Grid fin hydraulic pump stalled, so Falcon landed just out to sea. Appears to be undamaged & is transmitting data. Recovery ship dispatched.

I recall the last time they said they sent a recovery ship after a non-kaboom water landed F9.  They blew it up.  Was that by shooting it?  It'll be interesting, how do you approach such a thing unless there's a way to de-pressurize it?  Then once you have it under tugboat control what do you do with it??  It'll be close to shore, possibly drifting rear the port entry, possibly having a hazard zone that precludes cruise ships from coming in / out of port.

But how can it be intact if there was a smoke puff visible above the trees in the first video???  Oh... The smoke must have been reflected exhaust smoke and water from the surface.

[Johnnyhinbos]

At what point when you don't have complete control of your rocket flying back toward land does range safety kick in? While i'm sure they are happy they got their rocket back (albeit a little wet) I expect we will need to be asking some questions about whether the automated flight termination system worked as it was designed - and if it did - who didn't trigger a manual termination and why not? Dangerous as hell.

Isn't AFTS for the booster safed around boostback? What would unzipping the stage do with the minimal fuel left at that point?

[matthewkantar]

I clocked the stage had about 36 RPM during the burn.

On edit, 9 rpm, forgot to divide by four after counting legs going by.

[Aurora]

Just before the first stage began to spin, the video shows a ring of something releasing by the left fin.  The announcer said something about ice releasing - this was not ice.   Maybe a seal on one of the hydraulic controls of the fins?

[Tass]

No explosion in the video posted above on landing. That is impressive.

There was smoke just above the trees on the right immediately after.  Where there's smoke there's fire they say.  And if not an explosion at least there would be a bursting of the pressurized tanks.  What seems to be missing is the COPVs taking flight as we've seen before.

Betcha the folks at Vandenburg that prevented SSO-A from coming down near NROL-71 are feeling justified right now.

Nope. Intact and still transmitting per Elon.

[DigitalMan]

At what point when you don't have complete control of your rocket flying back toward land does range safety kick in? While i'm sure they are happy they got their rocket back (albeit a little wet) I expect we will need to be asking some questions about whether the automated flight termination system worked as it was designed - and if it did - who didn't trigger a manual termination and why not? Dangerous as hell.

Why would they blow the rocket up when the trajectory was in the ocean?

This area offshore was cleared of traffic way before the flight, right?

There are documents that show the zones that are  cleared for launch if you are curious exactly what areas are keep out.

[kevinof]

It was ice and it came off the booster at the lower end, not where the fins are.

Just before the first stage began to spin, the video shows a ring of something releasing by the left fin.  The announcer said something about ice releasing - this was not ice.   Maybe a seal on one of the hydraulic controls of the fins?

[punder]

Hard to tell with the long lens but the landing looked verrrry close to the shore. Hopefully an easy recovery.

Well, easy-ish.

[ugordan]

Isn't AFTS for the booster safed around boostback?

Not around boostback, but it might be around the transonic regime, actually.

[envy887]

I think I'll pass on a that PTP vacation unless I'm diagnosed with something inoperable/terminal with less than 6 weeks to live.

Almost needed a Dramamine watching on YouTube.

BFS won't have grid fins or non-redundant hydraulic loops.

[RoboGoofers]

it sure did seem like it was using a lot of RCS pretty late, when you'd expect the fins to be actuating.

it makes me wonder if the stuck fin was doing more harm than good and if they should passively fail to a flush to body position.

[Lars-J]

https://twitter.com/johnkrausphotos/status/1070385056877895682

[Lars-J]

A short clip before the video was cut from the stage. As Elon says, definitely a grid find issue. They did not move here:
https://twitter.com/nextspaceflight/status/1070383431123722240

[whitelancer64]

There's already amateur footage of the landing attempt online.  It looks like one of the grid fins went hardover and got stuck.  Amazingly, the rocket managed to neutralize the roll and perform a soft touchdown anyway, but as it was on water it fell over and ruptured after touching down.

From the video I saw, it was still rolling during the landing / splashdown

[EnigmaSCADA]

I think I'll pass on a that PTP vacation unless I'm diagnosed with something inoperable/terminal with less than 6 weeks to live.

Almost needed a Dramamine watching on YouTube.

BFS won't have grid fins or non-redundant hydraulic loops.

I wasn't being serious. Obviously.

However, to your point, I'm not sure what you said really matters that much at this point, while of course there will be more robust/redundant systems (eventually), this landing attempt undeniably illustrates how much further we need things to be for propulsive landing of people (especially for the purposes of leisure travel) to become something. We can't claim BFR will be more reliable considering it hasn't even done a hop test.