From one of his tweets:
> Hydraulics are usually closed, but that adds mass vs short acting open systems. F9 fins only work for 4 mins. We were ~10% off.
> Hydraulics are usually closed, but that adds mass vs short acting open systems. F9 fins only work for 4 mins. We were ~10% off.
EDIT: never mind - I've learned that they have a steering function, as well as drag inducing function, and they ran out of hydraulic fluid required to induce more drag, which would thus slow the rocket down. Leaving my comment here in case anyone else is curious.
If the rocket's trajectory is correct, all that is required is a final hard burn to negate all downward velocity a short distance above the barge deck.
Basically, because they lost steering it came in too steep, and ended up falling onto the deck on its side because the engines couldn't compensate for that position.