SpaceX Checks Throttle Valve After Flawed Falcon 9 Recovery Attempt.
"Video of the stage descending to the landing ship showed the vehicle
approaching quickly but decelerating. However, closer to the platform the
Falcon 9 showed an excessive horizontal velocity component that prompted the
single engine used for landing to gimbal to correct the flight path angle.
Exhaust from the Merlin engine could be seen raising clouds of water from
around the platform as the stage maneuvered close to the edge of the landing
zone. The control system then commanded vectoring of the engine nozzle to an
angle that effectively over-compensated for the previous flight path angle
correction. By this time the vehicle was too low to make further corrections
and landed at too great a tilt and speed to safely land."
Apr 16, 2015 Guy Norris Aerospace Daily & Defense Report
http://aviationweek.com/space/spacex-checks-throttle-valve-after-flawed-falcon-9-recovery-attempt
The video released by SpaceX shows the Falcon 9 coming in too fast:
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Elon Musk @elonmusk
Apr 15
High resolution, color corrected, slow motion rocket landing video
https://youtu.be/BhMSzC1crr0
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Actually, since this is slow motion it actually landed faster than this.
And Elon has acknowledged in this tweet the present configuration, which can't hover, will
cause high g landings:
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@ID_AA_Carmack Thanks! 3 of 9 engines are lit initially, dropping to 1 near
ground. Even w 1 lit, it can't hover, so always land at high g
- Elon Musk (@elonmusk) April 15, 2015
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Study of the video of both failed landings suggest both could have landed
safely with hovering capability. Then the suggestion is made to make some
relatively low cost modifications to give the Falcon 9 hovering ability:
Hovering capability for the reusable Falcon 9.
http://exoscientist.blogspot.com/2015/04/hovering-capability-for-reusable-falcon.html
Bob Clark