SpaceX (general discussion)

[sferrin]

The barge is already stabilized. I just wonder if it's reaction time is sufficient.

The barge itself (the ship) is somewhat stabilized by thrusters. Making the flight deck stabilized through a hydraulic gimbal is something different.

Is there anything else that big that has been motion stabilized like that? Also, does anybody know if the rocket is just assuming it's got a level surface under it or are there sensors on it to check the angle of the surface beneath it? Just wondering if it had been able to pause a few seconds 5-10 feet off the deck, and wait for the deck to get more level, if it might have helped. It would be interesting to know all the scenarios they played out, and assumptions they're making.

 

[quellish]

Is there anything else that big that has been motion stabilized like that?

Yes, many things. For example, oil exploration and drilling ships. Anything rigid going down to the bottom needs to be stabilized relative to ship motion, and this deals with forces far, far greater than the barge would experience. I believe some ships have helicopter pads that are motion compensating as well.

 

[TomS]

Is there anything else that big that has been motion stabilized like that? Also, does anybody know if the rocket is just assuming it's got a level surface under it or are there sensors on it to check the angle of the surface beneath it? Just wondering if it had been able to pause a few seconds 5-10 feet off the deck, and wait for the deck to get more level, if it might have helped. It would be interesting to know all the scenarios they played out, and assumptions they're making.

I don't think Falcon can really hover. Even minimum thrust on one Merlin is too much to just hold altitude once it's down to zero velocity. At that point trying to wait out the platform means the stage would be pogoing as well, moving up when the engine is firing then falling when it's off.

I really think they've underestimated the difficulties of landing on a moving platform. I wonder if they wouldn't be better off building a semi-stationary platform on a jackup rig in the Gulf of Mexico for their high-velocity launches from Texas.

 

[Dragon029]

I really think they've underestimated the difficulties of landing on a moving platform. I wonder if they wouldn't be better off building a semi-stationary platform on a jackup rig in the Gulf of Mexico for their high-velocity launches from Texas.

I don't think they understimate the difficulty; Elon for example has said that this definitely won't be their last RUD ("Rapid Unplanned Disassembly" )

 

[LowObservable]

This might help:

http://www.quantumhydraulic.com/specs/QuantumMagliftML600.pdf

I believe they're used on the OSVs that the Navy uses to screen SSBNs entering and leaving harbor. Basically, they carry containers full of gravel to block any terrorist/SF rocket attacks.

 

[Sundog]

I don't think Falcon can really hover. Even minimum thrust on one Merlin is too much to just hold altitude once it's down to zero velocity. At that point trying to wait out the platform means the stage would be pogoing as well, moving up when the engine is firing then falling when it's off.

I really think they've underestimated the difficulties of landing on a moving platform. I wonder if they wouldn't be better off building a semi-stationary platform on a jackup rig in the Gulf of Mexico for their high-velocity launches from Texas.

Maybe they could adjust the descent speed to make sure it touches down when the pad is level? As opposed to a full on hover? Granted, it would depend in large on the period of the pad's motion and I also realize it isn't as though the period would be consistent.

 

[Sundog]

SpaceX First Stage Landing Story.

Apparently the landing leg didn't latch. Bummer. They're going to get all of this right eventually and kudos to them for not giving up. Also, apparently they aren't cleared to land back at Vandenburg.

 

[flanker]

Highest res; https://farm2.staticflickr.com/1669/24423604506_27d3c4548b_o.jpg

Notice the gimbal.

 

[Michel Van]

Here you tube video that show what happened

https://www.youtube.com/watch?v=jshk8ZVIgdI

 

[Sundog]

Thanks for the video. They stuck the landing! Hopefully there aren't any other weak links outside of the gear latch.

 

[Grey Havoc]

It blew up rather quickly there. Range safety device going off by accident? Or was that old bane of rocketeers, fuel tank vapours?


Here's a close up photo as it was tipping over.

http://www.telegraph.co.uk/news/science/space/12104824/Moment-SpaceX-Falcon-9-rocket-crashes-and-explodes-during-landing.html

 

[Grey Havoc]

Regarding the earlier successful landing on land: http://gizmodo.com/spacexs-returned-rocket-still-fires-mostly-1753442217

 

[FighterJock]

Anyone know what caused the landing leg to break? It seamed to go so well from the launch and release of Jason 3.

 

[flanker]

Anyone know what caused the landing leg to break? It seamed to go so well from the launch and release of Jason 3.

It was said several time in the thread already. The leg didnt latch in locked position. It didnt actually break or anything. And instead of reuploaded video here is the actual source;

https://www.instagram.com/p/BAqirNbwEc0/

Where Elon Musk says;

Falcon lands on droneship, but the lockout collet doesn't latch on one the four legs, causing it to tip over post landing. Root cause may have been ice buildup due to condensation from heavy fog at liftoff.

It was completely successful landing. Standing was the issue.

It blew up rather quickly there. Range safety device going off by accident? Or was that old bane of rocketeers, fuel tank vapours?

Yes there was some fuel remaining but keep in mind the fuel tanks are pressurized. It was not FTS.

 

[sferrin]

Thanks for the video. They stuck the landing! Hopefully there aren't any other weak links outside of the gear latch.

Damn, that looked about as dead center on the target as it could be too.

 

[flanker]

Within 1.3m of the dead center... So yeah. SES-9 barge landing next up and after that it is CRS-8 which will be land.

 

[Moose]

It blew up rather quickly there. Range safety device going off by accident? Or was that old bane of rocketeers, fuel tank vapours?

Probably just pressure. The fuel and oxidizer tanks are under pressure, when ruptured by the impact with the deck one or both came apart explosively. Luckily its mostly helium in those tanks by the time it lands, so the fireball wouldn't have been too big.

 

[merriman]

What is getting glossed over here, in the SpaceX re-run of the recovered booster engines: There was a problem with one of the motors. We have not heard the inspection report on that motor yet.

Did it ingest something knocked loose from within the lox/kerosene tank (caused by structure flexing during recovery maneuvers). Or, was FOD kicked up by the landing exhaust splash, pinging the turbine and/or clobbering the pintel injector of that motor. Why was that motors thrust curve all over the place?

I would very much like to know what that motor problem was! Is this a landing site problem or a tank problem?

David

 

[sferrin]

"Maybe some debris ingestion. Engine data looks ok. Will borescope tonight. This is one of the outer engines."

So there were fluctuations that, while yet unexplained, were still within acceptable parameters? ???

 

[Hobbes]

"Maybe some debris ingestion. Engine data looks ok. Will borescope tonight. This is one of the outer engines."

So there were fluctuations that, while yet unexplained, were still within acceptable parameters? ???

I suspect "Engine data" means data gathered by sensors on the engine. It's unlikely the engines are so heavily instrumented they can measure everything, so yes. Engine data can look okay while the engine does not perform to specifications.

 

[gral_rj]

I suspect "Engine data" means data gathered by sensors on the engine. It's unlikely the engines are so heavily instrumented they can measure everything, so yes. Engine data can look okay while the engine does not perform to specifications.

They can't measure everything, but you can learn a lot of things just by putting one or two thermocouples in the combustion chamber. Hell, you can buy a combustor dynamics sensor/software package for your heavy-duty gas turbine and get a lot of information for predictive maintenance - and you can bet those engines have more comprehensive monitoring systems than that of power plant gas turbines.

As for engine data looking ok while still not performing to specifications, yes, but the fact they will be(or already are) going to borescope the engine signals to me they have a point where measurements deviated from the expected, enough to warrant a closer look. Mind you, tolerance for deviation is at this point is much lower than what it would/will be when they operate Falcon commercially.

 

[Grey Havoc]

http://gizmodo.com/spacex-is-gearing-up-to-build-lots-and-lots-of-new-rock-1757515503

 

[fredymac]

And another launch tomorrow evening. Static fire completed yesterday.

https://spaceflightnow.com/2016/02/22/falcon-9-clears-static-fire-test-before-launch-this-week/

 

[flanker]

Will be a very difficult mission; both ascent and descent. Satellite will be the heaviest they have ever launched to GTO (5721kg) and because of the high orbit it will probably be the most challenging mission they have done, period. Landing wise it will be similar to DSCOVR, going very fast at MECO (8000-9000km/h) and will experience very high forces on the way down, like DSCOVR did;

https://twitter.com/elonmusk/status/564509965612634112

So they are skipping boostback in this case again and landing very far out at sea, something like 600km out. Weather is looking very nice out there, 2m/s winds and 1.8m waves.

F9FT being able to lift such a heavy sat to a challenging orbit + landing is very very impressive.

 

[sferrin]

They're up live for today's launch.

http://www.spacex.com/webcast

https://www.youtube.com/watch?v=6HSb_yBnJXA

 

[sferrin]

Never mind.

 

[flanker]

Looks like March 3'rd now.

 

[merriman]

Launch jobs are starting to pile up -- at this rate they won't have the time to scrub the soot and touch-up paint the launch structures as the end of the year approaches. This years manifest had about a launch a month. Not looking good if they can't solve the slush-oxygen problem.

David

 

[sferrin]

Launch jobs are starting to pile up -- at this rate they won't have the time to scrub the soot and touch-up paint the launch structures as the end of the year approaches. This years manifest had about a launch a month. Not looking good if they can't solve the slush-oxygen problem.

David

Given this is what, the 2nd launch with it, I'd say it's far to early to be throwing the baby out with the bathwater.

 

[flanker]

Yeah, only second flight with this version and no one has ever gone this cold with LOX - which is what the issue has been for the last two attempts. Angara uses colder RP-1 though.

 

[sferrin]

Yeah, only second flight with this version and no one has ever gone this cold with LOX - which is what the issue has been for the last two attempts. Angara uses colder RP-1 though.

On the webcast yesterday one of the guys said both were supercooled which I thought was odd. (As in both the LOX and RP1 on the Falcon.)

 

[flanker]

Yeah, only LOX is really super cooled. I think there were other silly mistakes in the webcast like them saying it will use multiple engines to land etc.

Falcon 9 v1.1:

LOX: ~ -180C
RP-1: ambient, ~ 21C

Falcon 9 Full Thrust:

LOX: -206C (~9.9% density increase versus v1.1)
RP-1: -6.6C (2.6% density increase v1.1)

Angara:

LOX: -180C
RP-1: -15C (density increase 3.4% vs ambient 21C)

So they could go even colder for RP-1 but not a whole lot of difference. LOX is where the big gains can be made and that is what they did.

Not official yet but there is a possibility for an attempt tomorrow.

 

[Moose]

They use 3 engines for the braking maneuver, that might have been the source of the multiple engines comment.

 

[flanker]

Yes, 3 engines for boostback and re-entry burns but their comment was for landing in particular iirc. Either way, it doesn't matter. T-13h.

 

[compton_effect]

The multiple engines comment for landing is actually correct.
Due to the concession to the client - the first stage won't do a boostback burn and instead come in in a ballistic arc - further out to sea.
The chances of a successful landing is so low that they'll be doing a multiple engine high-g burn to see if they can do it.

https://twitter.com/NASASpaceflight/status/703000514749984768

@NASASpaceflight First stage is going to pull some massive Gs slowing down. Multi-engine landing burn too! :-O

They'd lose the stage anyway - so they'll be destruct testing the landing concept.
So this is the aerospace equivalent of 'Hold my beer, I want to try something'.

 

[sferrin]

The multiple engines comment for landing is actually correct.
Due to the concession to the client - the first stage won't do a boostback burn and instead come in in a ballistic arc - further out to sea.
The chances of a successful landing is so low that they'll be doing a multiple engine high-g burn to see if they can do it.

https://twitter.com/NASASpaceflight/status/703000514749984768

@NASASpaceflight First stage is going to pull some massive Gs slowing down. Multi-engine landing burn too! :-O

They'd lose the stage anyway - so they'll be destruct testing the landing concept.
So this is the aerospace equivalent of 'Hold my beer, I want to try something'.

And the Mrs and I bought tickets to Deadpool a few days ago. SpaceX should be touching down just as the end credits roll.

 

[compton_effect]

Lol. I know the feeling.
But having seen the Merc with the Mouth - its a fair trade off.

 

[flanker]

The multiple engines comment for landing is actually correct.
Due to the concession to the client - the first stage won't do a boostback burn and instead come in in a ballistic arc - further out to sea.
The chances of a successful landing is so low that they'll be doing a multiple engine high-g burn to see if they can do it.

https://twitter.com/NASASpaceflight/status/703000514749984768

@NASASpaceflight First stage is going to pull some massive Gs slowing down. Multi-engine landing burn too! :-O

They'd lose the stage anyway - so they'll be destruct testing the landing concept.
So this is the aerospace equivalent of 'Hold my beer, I want to try something'.

I knew about the ballistic arc, no boostback, ASDS being 650km out to the sea etc but i missed the tidbit about it being a multiple engine landing burn. What the actual F. That is strange and super crazy.

 

[compton_effect]

Its SpaceX crazy. If they fail - it will be spectacular. If they succeed - it will be legendary. They would have proved first stage reusability through all the flight profiles.

One failure simulation has the engines and fuel tank crumple like a beer can . A second one -with more fuel left - has it punching a hole in the barge. Either way - the information gathered will be invaluable.

 

[sferrin]

Lol. I know the feeling.
But having seen the Merc with the Mouth - its a fair trade off.

Got my ticket time changed. Now I get to see both. If they launch today. Fingers crossed.