However, that was not what prevented it being good. Touchdown speed was ok, but a leg lockout didn't latch, so it tipped over after landing.— Elon Musk (@elonmusk) January 17, 2016
What we didn’t know at the time was just how close SpaceX came to actually pulling this one off (the video of the landing wasn’t made available until last night). Unlike the previous landing attempts, which either came in too fast or carried too much lateral velocity, yesterday’s landing was right on target. The rocket landed upright on the platform, shutdown its engines as planned and all appeared to be well. However, just seconds later, the rocket began toppling over before striking the platform and exploding into bits.
Musk went on to further speculate on what exactly went wrong this time, writing, “Falcon lands on droneship, but the lockout collet doesn't latch on one [of] the four legs, causing it to tip over post landing. [The] root cause may have been ice buildup due to condensation from heavy fog at liftoff.”
It’s unfortunate that this third launch was foiled by what seemingly looks like a minor mechanical failure, but it goes to show that SpaceX has all of the basics mastered, and just needs to work on getting these minor wrinkles ironed out to ensure that future ocean landings are finally successful.