SpaceX SpaceX: First stage landed Satellites in orbit

[Monsterboy]

http://www.wired.com/2016/01/spacex-still-hasnt-gotten-its-sea-legs/

3rd failed landing on the barge. The landing was fine but the legs gave in.

 

[mheslep]

Curious. Rate of descent appears in the same ballpark as the successful Cape landing. Possible differences: A sea induced pitch angle on the barge increasing the load on the down slope leg? Worse, a barge pitch up *rate* under the down side leg? More residual fuel mass than at the Cape? Clearly there was some.

 

[cjl]

Nope, leg failed to lock in place. Landing was fine.

 

[mheslep]

Nope, leg failed to lock in place. Landing was fine.

Yes I know it was the leg, but I thought the leg failed due to some kind of overstress, brought on by the landing?

 

[mheslep]

Media reports, "The company initially said it touched down harder than planned amid 10 to 15 ft swells. Later, ... Mr Musk suggested the mishap appeared to be the result of a simple mechanical failure...indicating 'touchdown speed was OK,' but the lock down mechanism on one leg didn't latch 'so it tipped over after landing'"

 

[cjl]

That agrees with what I saw - the touchdown velocity was sufficiently slow, so there wasn't an overstress, the leg just never locked in place, so it was free to fold and tip over after landing.

 

[Monsterboy]

Why should the rocket explode after tipping over ? does that mean there was a lot of fuel left ?

 

[cjl]

There was some fuel left, and there was also some helium pressurant left, so the tanks were pressurized. When the tanks ruptured (from falling over), the pressure sprayed the fuel and oxidizer around, and some of the fuel ignited on the still smoldering engines.

 

[rootone]

One leg simply failed to lock in place?
It sounds like a really basic design flaw which ought to be easily solvable, but a surprising explanation.
I know that there are occasional similar incidents with aircraft landing gear locking, which I imagine must work on a similar mechanical principle, but that's about once in 10,000 landings.

 

[mheslep]

There was some fuel left, and there was also some helium pressurant left, so the tanks were pressurized. When the tanks ruptured (from falling over), the pressure sprayed the fuel and oxidizer around, and some of the fuel ignited on the still smoldering engines.

Yes it's very apparent over a second or so, the tanks rupture and escaping fuel oxidizer immediately condense air moisture forming white clouds; when the clouds hit that hot aft engine kaboom.

 

[mfb]

One leg simply failed to lock in place?
It sounds like a really basic design flaw which ought to be easily solvable, but a surprising explanation.
I know that there are occasional similar incidents with aircraft landing gear locking, which I imagine must work on a similar mechanical principle, but that's about once in 10,000 landings.

Aircrafts don't go to space (well, with irrelevant exceptions), and much more money goes into their development. Somewhere I read that ice was related to the issue.

 

[mheslep]

Somewhere I read that ice was related to the issue.

Iron Man: How'd you solve the icing problem?
Iron Monger: Icing problem?
[his suit begins to fail]
Iron Man: Might want to look into it.
[He raps his fist on Iron Monger's frozen helmet as his suit fails and plummets to the ground]