This is an "unpublished video" on a non-SpaceX YouTube channel. Who uploaded this?
I guess that's what "This video is unlisted. Be considerate before sharing." gets you in today's world...
Space X CR6 First stage landing
31–40 of 205 posts
Re: Space X CR6 First stage landing
#32Earlier quoted context omitted.
There is always some extra fuel and oxidizer, as it is used to slow the vehicle, and is needed until touchdown. If the vehicle were to run out of propellant before landing, it would crash. In addition, the LOX makes any combustion spectacular.
Complete destruction is obviously expensive. Finding a way to prevent an explosion if it falls over after landing seems worthwhile. If it hovered for 5 seconds at .5 meters, for example, could it burn off enough extra fuel?
> If it hovered for 5 seconds at .5 meters, for example, could it burn off enough extra fuel?
The Falcon 9 cannot hover. The thrust of the single landing engine, even when throttled down to minimum, will provide significant lift to the empty rocket. That's part of what makes this maneuver so difficult and so awesome: it's called the hoverslam, where you achieve 0m altitude and 0m/s velocity at time = 0.
For reference, though, the Grasshopper/F9R-dev1, could hover due to it only having 3 engines, not 9, and because they could ballast it with additional fuel.
Re: Space X CR6 First stage landing
#33Non-engineers see this as a failure. Engineers and scientists see this as an awe-inspiring success from which to learn, iterate and try again. I don't fault reporters for exagerated headlined focusing on failure. They don't know any better. That is not what their lives are about and most might be challenged to understand that nothing in that video constitutes failure in the context of evolving a design. In fact, fail…
For an example of how this works in practice, just go back to the original rocket programs of the 50's and early 60's. Those guys dealt with failures much worse than this, and ended up with some of the most awesome achievements in human history.
Re: Space X CR6 First stage landing
#34Seems that the control system only tries to guide it on the X & Y axis, but if I was controlling it and saw it coming in at that steep angle, I'd fire hard on the Z axis to try to raise it up, fix the angle, and then lower it down again.
Is it correct to say that this landing control system never tries raising the craft vertically?
Re: Space X CR6 First stage landing
#35Earlier quoted context omitted.
There is always some extra fuel and oxidizer, as it is used to slow the vehicle, and is needed until touchdown. If the vehicle were to run out of propellant before landing, it would crash. In addition, the LOX makes any combustion spectacular.
Complete destruction is obviously expensive. Finding a way to prevent an explosion if it falls over after landing seems worthwhile. If it hovered for 5 seconds at .5 meters, for example, could it burn off enough extra fuel?
Their eventual goal is for every rocket to land and not have problems. Providing enough fuel for five seconds of hovering is a waste of valuable fuel (see how they're already so low that they run out in the process).
Also, falling over almost certainly also leads to a writeoff, as otherwise they'd just fly the rocket into a big pit of fire retardant foam blocks.
I'd imagine that the lateral stresses involved in a crash landing are more than enough to write off the rest of the rocket, and so the explosion would just make the barge slightly harder to clean up.
Re: Space X CR6 First stage landing
#36I can't help but feel bad for that one poor little RCS thruster doing its level best to keep the first stage upright, but ultimately running out of fuel.
Looks like the landing leg on that side collapsed during touchdown. The thruster did all it could, but alas, it couldn't keep firing forever... nor did it have enough thrust to actually hold the rocket vertical all by itself, for that matter. An A for effort though.
Re: Space X CR6 First stage landing
#37Anybody know anything about the tech they're using to guide the stage to the barge? Since the flight is so short, I suppose they could get a GPS position on the barge at liftoff and pre-program that as the initial target, but I'd think they need some kind of terminal guidance actually tracking the barge to hit it reliably. Maybe visual or radar, or a radio beacon or something?
I've always imagined that the big bulls-eye wasn't painted on the barge just for decoration. I don't have any hard info though. Come to think of it, it would be hard to get video through the rocket exhaust.
Re: Space X CR6 First stage landing
#38Anybody know anything about the tech they're using to guide the stage to the barge? Since the flight is so short, I suppose they could get a GPS position on the barge at liftoff and pre-program that as the initial target, but I'd think they need some kind of terminal guidance actually tracking the barge to hit it reliably. Maybe visual or radar, or a radio beacon or something?
On the live feed, just after +1:30 I heard "Recovery platform has acquisition signal"
Re: Space X CR6 First stage landing
#39Seems that the control system only tries to guide it on the X & Y axis, but if I was controlling it and saw it coming in at that steep angle, I'd fire hard on the Z axis to try to raise it up, fix the angle, and then lower it down again. Is it correct to say that this landing control system never tries raising the craft vertically?
It's tricky because it can't hover, one engine on minimum provides too much thrust.
So if you do raise it up, you'd have to stop the engine, then wait a little and re-light it again.. which I think is tricky to do, and the engines only have so many "re-light" cycles in them, so you don't want to use up too many , else you can't re-use the thing for another real flight.
Re: Space X CR6 First stage landing
#40Why did it explode in such a dramatic fashion? I thought the booster was almost entirely empty when it returns to the barge.
There is always some extra fuel and oxidizer, as it is used to slow the vehicle, and is needed until touchdown. If the vehicle were to run out of propellant before landing, it would crash. In addition, the LOX makes any combustion spectacular.
It probably would explode before crashing. The various machinery in the engine expects fuel to be there, providing resistance. From what I understand, if gas was to be sucked into the engine, the end result would be a rapid disassembly.