

SpaceX rocket recovery test fails - tankenmate
http://www.bbc.co.uk/news/science-environment-30752515

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ChuckMcM
While the headline is accurate, the reality is much more interesting. The
first stage did return, it made it back to the landing barge (a pretty small
target) and failed to land on the barge.

So from a debugging standpoint, interesting questions are what was the closing
speed with the barge (how hard did it "land")? This is interesting because if
nothing else one could consider an alternate landing structure of a net or
other support structure where the final energy exchange is handled by an
arrestor net of some sort.

What did telemetry say about what altitude the rocket thought it was at vs the
barge? This is the one I would be most interested in if I were at SpaceX, 'sea
level' is not nearly as precise as one might expect, there are tides, there
are ocean swells, etc. So the actual distance to the barge has to be trimmed
by radar. If the stage thought it was higher than it was, it might not have
switched to terminal guidance mode yet. If it had switched, how quickly can it
get into 'hover' from the switchover. And finally once in hover how many
seconds of fuel does it have to close the final gap?

I thought this was an excellent first shot at landing, and I may be overly
optimistic here but it seems like many more things "worked" here than didn't
work. That bodes well for the eventual success.

