Video of Falcon 9 first stage landing attempt
The footage below is high resolution. Watch how the rocket comes in to the barge. It is once again astonishing that the rocket hits the target, but it is coming down very fast, and not very vertical. Like the Grasshopper tests, they need to slow it down more just before landing.
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The footage below is high resolution. Watch how the rocket comes in to the barge. It is once again astonishing that the rocket hits the target, but it is coming down very fast, and not very vertical. Like the Grasshopper tests, they need to slow it down more just before landing.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
The first stage appears to exhibit a pendulum like action as it descends. The rockets are attempting to counteract this action, thrusting on opposite sides. This corrective action may have prevented adequate velocity reduction (too much decent speed). A total wag on my part.
Still it’s a win and congratulations to team SpaceX!
For the second – SECOND – attempt, that’s phenominally good. You can see the benefit of contemporary computers: 30 years ago it probably would have taken half a dozen attempts just to hit the target. The stage does appear to descend too fast, and there are some terminal approach control issues. Still, it looks like a typical engineering exercise: design, build, operate, analyze, improve. Repeat as required.
Probably Champagne at Space X; certainly sweaty palms at every other launch contractor.
Actually, they have to come in fast. That was the whole ‘hover-slam’ thing from the Grasshopper days that was never completely explained.
The thrust of the single Merlin 1D as deeply throttled as possible, exceeds the weight of the empty stage. So they cannot hover.
Thus they must come in faster than you would like, and decelerate to zero at the last second.
I got a feeling it was something like that from watching the Grasshopper videos. We can see from the shadow that even Grasshopper came in frighteningly fast:
https://www.youtube.com/watch?v=9ZDkItO-0a4#t=70
If I were to guess, they may be having more trouble with winds than they did during the Grasshopper tests. With those tests, they could choose a time when the winds were favorable, meaning within the tolerances that worked during simulations.
As long as SpaceX knows what is going wrong, then they can converge on a solution. If they don’t know, then they need more instrumentation to help them figure it out.
I’ve been involved with tests that required several attempts to get it right, and we weren’t trying anything quite as new or untried as this (read: “the hardware in those tests should have worked right the first time”), so I am not surprised that they still need more attempts. They may do a few more tests after they seem to have gotten it right, before they declare reusable Falcons to be operational.
It would seem to me that their throttling not withstanding, the rocket wasn’t coming in directly over the barge. It skidded in sideways and the corrective motions by the main motors and the corrective burns by the jets up are what caused the pendulum like motion. I don’t pretend to have a degree in orbital mechanics but I do have a pretty good understanding of objects in motion and my offered opinion would be to have the rocket achieve a lateral stationary position over the barge while it is still at altitude and then only make fine adjustments with the nose jets as needed if there is drift.
I know using Kerbal Space Program as an example is probably horrifyingly oversimplifying the matter of controlling such a vehicle, but I can’t help but compare that landing to one of my own when I realize too late, that I’m not descending vertically over my intended landing zone, but rather drifting across the surface. The resulting, panicky attempt to roll the craft and stop horizontal motion usually results in rapid loss of altitude followed shortly by the loss of the vehicle. It seems to me the same thing happened here, the stage spent too much time trying to correct it’s horizontal position in the late stages of landing when it should have been maintaining a vertical position for landing.