SpaceX Falcon Heavy : Arabsat 6A : LC-39A : April 11, 2019 - DISCUSSION

[Wargrim]

I hope it fell on the barge and not overboard. On barge would probably mean multiple engines recovered and maybe gridfins.

[DistantTemple]

I don't think we know... but if it was unsafe for humans to be on board the drone ship to secure the booster because of the sea state, which was also causing the booster to move, then even if it didn't topple straight over the side, it would be impossible to secure it .... and avoid it finding its eventual way over.

[Grandpa to Two]

I hope it fell on the barge and not overboard. On barge would probably mean multiple engines recovered and maybe gridfins.

https://www.theverge.com/2019/4/15/18311945/spacex-falcon-heavy-center-core-drone-ship-rough-ocean

The first paragraph from the Verge article stated it fell overboard;
“SpaceX successfully landed the center core of its Falcon Heavy rocket on a drone ship last week, but the vehicle accidentally fell into the ocean while in transit to the Florida coast. The company blamed the loss on choppy seas.”

[strawwalker]

Can they remedy this in the future, by putting a crew on board and using cable of something to strap it down? 

That's not a real remedy, that just adds a lot of risk in bad weather. The octagrabber is the superior solution.

Is Octagrabber autonomous? I was under the impression that it required a human operator on deck. Do we know one way or the other?

[Lars-J]

Can they remedy this in the future, by putting a crew on board and using cable of something to strap it down? 

That's not a real remedy, that just adds a lot of risk in bad weather. The octagrabber is the superior solution.

Is Octagrabber autonomous? I was under the impression that it required a human operator on deck. Do we know one way or the other?

The point of the octagrabber is to NOT have a human operator on deck, so I doubt it. I assume it is remote controlled from a ship nearby, but that is only my assumption.

[ulm_atms]

I will say this.  The sea state must of gotten really bad really quickly as it did not look bad at all on the video.  You could tell there was some bobbing...but I have seen much worse bobbing on other landings and those did just fine.

Looking at the buoy data (https://www.ndbc.noaa.gov/) the highest I can find is a 2.7m swell at buoy 41047 which seems quite north of what I would expect their track to be.  The rest of the buoys around there were around 2.1m and that is not so huge that I would expect it to tip over or people to not be able to board.  I know some of the landings in the pacific had bigger swells at the time and were boarded/survived.

Anyone know (or can find) a better understanding/data of the sea state in that time frame?  Just confused as I can't find any data that would show sea state bad enough for them not to of been able to get on the ASDS and secure it.  They have done it in worse....

[FinalFrontier]

7 to 10 foot swells are more than enough to knock something that tall and slender over if it's not tied down. Especially on a vessel as small as the barges are.
That may sound silly to some here but in relative terms the ASDS barges are quite small and have very little free board. They also have no ability to stabilize themselves just dynamic positioning thrusters which can be overcome in bad weather. With those seas the motion of the barge will become extremely violent and anything not chained down is going in the drink. Not worth someone getting killed trying to do manual rigging to secure it and the octograbber is likely to be insufficient for conditions that severe.

Not surprising but disappointing nonetheless. Booster in the drink from the sound of it no piece was left.

[ulm_atms]

7 to 10 foot swells are more than enough to knock something that tall and slender over if it's not tied down. Especially on a vessel as small as the barges are.
That may sound silly to some here but in relative terms the ASDS barges are quite small and have very little free board. They also have no ability to stabilize themselves just dynamic positioning thrusters which can be overcome in bad weather. With those seas the motion of the barge will become extremely violent and anything not chained down is going in the drink. Not worth someone getting killed trying to do manual rigging to secure it and the octograbber is likely to be insufficient for conditions that severe.

Not surprising but disappointing nonetheless. Booster in the drink from the sound of it no piece was left.

Oh I agree.  I'm confused on the "not being able to tie it down" part.  They should of had ~18 hours from landing to the 2+ meter swells if I read the data right.  That is where my confusion is....why did they not have enough time?

[strawwalker]

Can they remedy this in the future, by putting a crew on board and using cable of something to strap it down? 

That's not a real remedy, that just adds a lot of risk in bad weather. The octagrabber is the superior solution.

Is Octagrabber autonomous? I was under the impression that it required a human operator on deck. Do we know one way or the other?

The point of the octagrabber is to NOT have a human operator on deck, so I doubt it. I assume it is remote controlled from a ship nearby, but that is only my assumption.

Ah, thanks for clarifying. That does make a lot of sense.

[TrueBlueWitt]

Seems pretty easy to create a cable "collar" that has a cable strung around the deck perimeter from one corner and pre-tension lockable cable spools at the other 3 corners.. add flip up cable runners at each corner to keep the cable above the deck.. could even let the cable ride up the legs if necessary. Even if you did slightly damage the core, at least you keep it on the ship!

[Joffan]

I will say this.  The sea state must of gotten really bad really quickly as it did not look bad at all on the video.  You could tell there was some bobbing...but I have seen much worse bobbing on other landings and those did just fine.

Looking at the buoy data (https://www.ndbc.noaa.gov/) the highest I can find is a 2.7m swell at buoy 41047 which seems quite north of what I would expect their track to be.  The rest of the buoys around there were around 2.1m and that is not so huge that I would expect it to tip over or people to not be able to board.  I know some of the landings in the pacific had bigger swells at the time and were boarded/survived.

Anyone know (or can find) a better understanding/data of the sea state in that time frame?  Just confused as I can't find any data that would show sea state bad enough for them not to of been able to get on the ASDS and secure it.  They have done it in worse....

Might have been a resonance issue; if the wave frequency was such as to amplify the movement of the barge+rocket, it would be both difficult to board and likely to topple the rocket.

[rsdavis9]

I will say this.  The sea state must of gotten really bad really quickly as it did not look bad at all on the video.  You could tell there was some bobbing...but I have seen much worse bobbing on other landings and those did just fine.

Looking at the buoy data (https://www.ndbc.noaa.gov/) the highest I can find is a 2.7m swell at buoy 41047 which seems quite north of what I would expect their track to be.  The rest of the buoys around there were around 2.1m and that is not so huge that I would expect it to tip over or people to not be able to board.  I know some of the landings in the pacific had bigger swells at the time and were boarded/survived.

Anyone know (or can find) a better understanding/data of the sea state in that time frame?  Just confused as I can't find any data that would show sea state bad enough for them not to of been able to get on the ASDS and secure it.  They have done it in worse....

Might have been a resonance issue; if the wave frequency was such as to amplify the movement of the barge+rocket, it would be both difficult to board and likely to topple the rocket.

I always like to say for a given size ship there is a wave that will make it behave badly.

[FinalFrontier]

Still somewhat unclear if the entire vehicle went overboard or some chunk is left on the barge. Hope to hear more in the next couple days, or visual when the barge gets home. It sounds like it fully went overboard but there is some mitigating information.

[Steven Pietrobon]

SpaceX needs to solve this problem, otherwise the economics of using FH where an expendable F9 can do the job goes out the door. I'm thinking giant lassos! (Modified octograbber could do the job as well. :-)

[vanoord]

Still somewhat unclear if the entire vehicle went overboard or some chunk is left on the barge. Hope to hear more in the next couple days, or visual when the barge gets home. It sounds like it fully went overboard but there is some mitigating information.

From Elon's tweet that the engines may be recoverable, it would suggest that the engines are still on the deck - I'd speculate that if the stage fell over, it would puncture the tanks which would result in the booster sinking if it had gone over the side.

[alang]

SpaceX needs to solve this problem, otherwise the economics of using FH where an expendable F9 can do the job goes out the door. I'm thinking giant lassos! (Modified octograbber could do the job as well. :-)

Amazing how quickly the problems change.
At one time landing the booster seemed impossible.

[drzerg]

they probably could develop some cable system that automaticly locks on hooks on the stage just above the legs and temporarely secures it.

[Celestar]

Or a vessel with a crane that removes the stage from the barge and puts it into a horizontal position, fold up the legs (does that work already?) and cover the engine (to protect from salt water). That way, you could even leave the barge out for back-to-back missions and a normal vessel would be much faster to get back to the shore, wouldn't it?

Celestar

[kevinof]

I think they already have the solution and it's the octograbber - Musks tweet says that the parts to allow the grabber to secure the FH center core weren't ready in time.

So octograbber is the solution.

SpaceX needs to solve this problem, otherwise the economics of using FH where an expendable F9 can do the job goes out the door. I'm thinking giant lassos! (Modified octograbber could do the job as well. :-)

[mulp]

Maybe SpaceX can rent the air craft carrier budgeted to be mothballed;-)

Even if SpaceX doesn't get to the point of demonstrating hyperhypersonic international passenger capability until say 2024, it will take a decade to figure out how to get a sea based spaceport where a dozen or more sonic booms per day are far enough from people.

Part of the process of getting approval will be demonstrating safety of landing with people around, like jet planes do thousabnds of times per day.

The fuel load of the rocket is less than jets, so the only big risk is the remaining LOX. A bigger ship, but not necessarily bigger landing pad, will be a next step, with crew on board when landing.

Given that, losing rockets overboard while perfecting and demonstrating safe landings on small unstable landing pads is acceptable given the limited time until a long term solution is prototyped.

Not only will a bigger ship be more stable, it would have the cabability of cranes, etc., or the the equivelant of TEL/strongback.

This is in the prototyping of the prototypes stage for the Starship era.