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

[inventodoc]

i'm very pleased.   they are repeatedly making it to the landing sites.   This collet problem can be solved and the landing looked soft enough even in the moderately unfavorable sea state. What this means to me is:

1. they will nail the next asds attempt or the one thereafter

2. asds landings will probably work most of the time in the future.

 

[Lars-J]

Interesting view of the top of the launch mount. It looks like this mount can only be used for Falcon 9 and not Falcon Heavy.

The mount is a piece that can be taken off the TE and be replaced. There would likely be a F9 and an FH version. But we will get a clearer view of how it will work when the TE receives further modifications to support FH.

[Steven Pietrobon]

Inside the fairing.

Fairing separation.

Fairing passing at the bottom left of engine.

Just Read the Instrunctions just before the landing attempt. A reflection of the engine glow can be seen on the far thrust deflector.

Second stage just before second ignition cutoff.

Jason 3 after separation.

[CuddlyRocket]

The stage would have toppled over onto the failed leg and what remains on deck appears to be at the bottom of the stage. So, there's a good chance the failed leg is either under the wreckage or is the leg sticking out, the stage having rotated slightly due to the RUD.

[OxCartMark]

Are the water cannons spraying salt or fresh water? If fresh, it seemed like they had them started up fairly early (though maybe they just have huge tanks and don't care). If salt, were they supposed to track the stage as it came in? Seems like maybe not the best idea to spray salt water at things. Or maybe they were spraying water on something else entirely...?

Seems like they would need a boatload (literally) of fresh water to maintain it that long.

I too, would like to know of the answer to this...

The Marmac 300 series barges have within them 24 ballast tanks which IIRC, are about half full (read back through the 293 pages of the ASDS thread for full details).  I seem to recall it being said that one reason for doing was that it towed better when ballasted.  Another would be that it sits at a better height for bording when in port.  And it seems to me(?) that a ballasted ASDS would bob and weave with lower amplitude and lower frequency.  But to the point above it would seem to me that filling the tanks with fresh water would be likely way to go to reduce internal corrosion.  And in any case those tanks would provide water for the fire hoses for literally days.
_________

Elon: "Root cause may have been ice buildup due to condensation from heavy fog at liftoff."
Can someone link me up with how there would be condensation turning to ice on the fuel tank when this wasn't supercooled fuel (or was it?)?  The legs don't extend up to the LOX tank.  Or is his theory that ice fell from above onto  the collet / latch?  Wait, the collet / latch is on the cylinder which is protected from falling ice until the last few seconds before landing because its sheltered between the leg and the fuel tank.  Help me understand.
________

To me it appears as if the explody / deflagatory event starts at the point where the cylinder of the failing leg meets the fuel tank.  It happened before the body slam onto the deck.  Apparently the cylinder was compressed to its full retracted geometry then when it went solid continued motion punched the end of that cylinder through the tank.   I find it odd or at least I learned something in how very rapidly after that the escaping fuel burst into flame.  No, I don't see any pre-existing flame as someone claims to have observed though there presumably would have been some around the engines.  But an ignition from the engine would seem to me to have been delayed a bit longer.
_________

That disintegration seemed too quick to me- is it possible that the last act of FSW was to unzip the stage?

That's because its a very thin walled pressure vessel charged with ~3 atm.  The same way that a balloon disintegrates when you put a pin in it, this thing disintegrates when you jam a pneumatic cylinder into it.  We saw the previous two F9 v. ASDS impact kabooms disintegrate (the F9, not the ASDS) equally fast.

The process of getting to the ASDS is getting surprisingly repeatable for such an early point in the development of the technology.

[OxCartMark]

Now that we know more than we did in the minutes after the landing and the video outage earlier today I'm still of the opinion that...

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.

[mikelepage]

Video:

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

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.

Looks like a really soft landing.

...and yet, a noticeable bounce on the legs.  They can take quite some dynamic force.

Check out the water deluge slewing toward the plume as it lands 

So close... will almost definitely get it next time

But yes, is it just me or does the entire stage drop by about 1-2 feet the instant after the engine turns off? Seems like the swell could have contributed to the ASDS being that much lower than expected at that particular moment.  Someone upthread mentioned how the swell might affect the altitude of the landing site by that much.

Admittedly it's hard to tell in the OG2 landing video, but I don't see any evidence of a similar movement there.

[CameronD]

So close... will almost definitely get it next time

But yes, is it just me or does the entire stage drop by about 1-2 feet the instant after the engine turns off? Seems like the swell could have contributed to the ASDS being that much lower than expected at that particular moment.  Someone upthread mentioned how the swell might affect the altitude of the landing site by that much.

Admittedly it's hard to tell in the OG2 landing video, but I don't see any evidence of a similar movement there.

No, not just you. The ASDS appears to be rising as the stage is coming down, but that particular slump appears to coincide with the leg failing.   They could be related or it could just be an optical illusion...  A different camera angle (preferably from a nearby drone) would help a lot.

[boog]

I would think a closed hydraulic system would be enough to keep the legs locked. How does this collet lock the legs and why isn't hydraulic pressure alone good enough?

[Lumina]

So close... will almost definitely get it next time

But yes, is it just me or does the entire stage drop by about 1-2 feet the instant after the engine turns off? Seems like the swell could have contributed to the ASDS being that much lower than expected at that particular moment.  Someone upthread mentioned how the swell might affect the altitude of the landing site by that much.

Admittedly it's hard to tell in the OG2 landing video, but I don't see any evidence of a similar movement there.

No, not just you. The ASDS appears to be rising as the stage is coming down, but that particular slump appears to coincide with the leg failing.   They could be related or it could just be an optical illusion...  A different camera angle (preferably from a nearby drone) would help a lot.

From state of sea (only a swell, no waves) there was little to no wind making it easier for the landing algorithm to approach vertically.

From the video it seems it was a smooth and soft landing. No visible difference vs. the Cape landing. So deck movement probably wasn't a factor, other than to expedite the tipping over of a stage which has no support on one side.

Also from the launch video, did you notice the droplets on the camera pointing down along the first stage? The rocket was soaking wet on takeoff due to the fog. But isn't the Kerosene tank at 7 degrees Celsius? Is it possible that the water condensed into the mechanism and turned to ice during the flight?

The silver lining is that every attempt makes the system more robust. SpaceX is learning quickly from these! Congratulations.

[HMXHMX]

I would think a closed hydraulic system would be enough to keep the legs locked. How does this collet lock the legs and why isn't hydraulic pressure alone good enough?

The legs don't use hydraulics, but rather He pneumatic system for deploy.  Very likely that is done to save mass, as the long pistons of at the current leg design would mean a lot of fluid, and that fluid also has to be stored somewhere.

[boog]

I would think a closed hydraulic system would be enough to keep the legs locked. How does this collet lock the legs and why isn't hydraulic pressure alone good enough?

The legs don't use hydraulics, but rather He pneumatic system for deploy.  Very likely that is done to save mass, as the long pistons of at the current leg design would mean a lot of fluid, and that fluid also has to be stored somewhere.

Even with a pneumatic system, what we saw last two barge landings in a row was a leg bending back on itself. There must be leaking he gas being pushed out of the system. Is something not supposed to prevent the gas from leaking out?

[Lars-J]

I would think a closed hydraulic system would be enough to keep the legs locked. How does this collet lock the legs and why isn't hydraulic pressure alone good enough?

The legs don't use hydraulics, but rather He pneumatic system for deploy.  Very likely that is done to save mass, as the long pistons of at the current leg design would mean a lot of fluid, and that fluid also has to be stored somewhere.

Even with a pneumatic system, what we saw last two barge landings in a row was a leg bending back on itself. There must be leaking he gas being pushed out of the system. Is something not supposed to prevent the gas from leaking out?

Again you seem to think of it is a hydraulic system, but it is not. Gas compresses, liquid does not. (Simplified of course) The gas is only used to extend the piston and allow the final segment to compress to absorb momentum. The other segments apparently need to be mechanically locked in place.

[hrissan]

I would think a closed hydraulic system would be enough to keep the legs locked. How does this collet lock the legs and why isn't hydraulic pressure alone good enough?

The legs don't use hydraulics, but rather He pneumatic system for deploy.  Very likely that is done to save mass, as the long pistons of at the current leg design would mean a lot of fluid, and that fluid also has to be stored somewhere.

Even with a pneumatic system, what we saw last two barge landings in a row was a leg bending back on itself. There must be leaking he gas being pushed out of the system. Is something not supposed to prevent the gas from leaking out?

IMHO Instead of trying to make quality seals, as the helium is light, the better idea might be to load more helium to allow modest leaking between leg piston segments during deployment until they are locked.

Not sure about shock absorbers, they might work same way, but the rate of leakage from them should be close, otherwise the rocket will not settle symmetrically and might topple.

[Rocket Science]

They could use pressurized RP-1 as a hydraulic fluid since its on board anyways and typical downlocks...

http://code7700.com/g450_landing_gear_uplocks_downlocks.html

[alang]

Maybe two locking points during extension. If the second one fails you are left with a ten degree list. (And other dumb ideas that add weight).

[alang]

Oops, sorry. Mass.

[JamesH]

I would think a closed hydraulic system would be enough to keep the legs locked. How does this collet lock the legs and why isn't hydraulic pressure alone good enough?

The legs don't use hydraulics, but rather He pneumatic system for deploy.  Very likely that is done to save mass, as the long pistons of at the current leg design would mean a lot of fluid, and that fluid also has to be stored somewhere.

Even with a pneumatic system, what we saw last two barge landings in a row was a leg bending back on itself. There must be leaking he gas being pushed out of the system. Is something not supposed to prevent the gas from leaking out?

IMHO Instead of trying to make quality seals, as the helium is light, the better idea might be to load more helium to allow modest leaking between leg piston segments during deployment until they are locked.

Not sure about shock absorbers, they might work same way, but the rate of leakage from them should be close, otherwise the rocket will not settle symmetrically and might topple.

Not sure why you seem intent on changing the deployment mechanism, when it was the locking system that failed...

[gadgetmind]

When I saw the first picture, I thought the Merlin's might have survived, but having now watched the video, I'm not so sure. However, the LOX would have dissipated pretty quickly and without that the RP1 isn't particularly flammable, so you never know.

[Rocket Science]

Its an evolutionary process to achieve a fault tolerant design. All and all, still a good day for data collection and the Falcon flew flawlessly on to the deck... A lot of folks should still be proud!!