I read all the news about SpaceX’s Falcon 9 latest “failure” to land on an autonomous spaceport drone ship aka barge. I view these as trials to success. Here’s why.
1. Grasshopper Successes: The two videos below show that the early landing trials aka Grasshopper from several heights between 250m and 1,000m.
The lessons here are:
a) Pinpoint landing of a 1st stage rocket is technologically feasible.
b) This 1st stage rocket has to attain zero vertical velocity at a minimum 250m above the barge.
Video of 250m test
Video of 1,000m test
2. Falcon 9 1st stage crash landing – 1st attempt: SpaceX tells us that the failure was due to a hard landing (see video below) but at 0:03 minutes into the video one can see that the 1st stage has substantially tilted before it hit the deck i.e. the 1st stage did not tilt because it hit the deck.
The lessons here:
a) A wobble – a dynamic instability – occurs before landing.
b) The guidance systems are unable to cope with new wobble.
Video of 1st attempt
3. Falcon 9 1st stage crash landing – 2nd attempt: The video of the second attempt (below) confirms that indeed a wobble has been introduced before the stabilization fins are deployed. Further, this deployment exacerbates the wobble, and the guidance systems is unable to handle this exacerbated wobble.
The lessons here:
a) 1st stage vertical velocity needs to be zero by at least 250m above deck.
b) The stabilization fins need to be redesigned to alleviate exacerbation.
c) Like the Space Ship One’s shuttlecock approach, the 1st stage upper fins need to be deployed before the lower fins are.
d) Upgrade the landing guidance system to account for more severe wobbles.
If at a minimum, SpaceX achieves zero velocity at 250m before deployment of landing gear it will be successful. The other recommendations are good to have.
I expect SpaceX to be successful by their 3rd try.