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I know fuel is an issue, but is it simply not technically possible or feasible for the rocket to slow down much more before the actual touch down? Like hover 5 meters above ground for say 2-3 seconds to get its bearings for a gentle touch down, would it use that much fuel to do so?
@Big Mike
I don't think fuel is actually much an issue with the profiles we are flying. LEO mission so 2nd stage doesn't have to have a lot of delta V, so that means easier for 1st stage and not as much delta V needed there either. The big issue is that we are taking a decent sized rocket engine (only 1 in this case but still big issue) and you fire it right into a bunch of steel that has pretty much nothing for thermal protection on it. No thermal protection is kind of on purpose, if your idea is to make a reusable vehicle you don't want to have to be putting a bunch of thermal protection on every time you launch. We could hover the vehicle easily IF we wanted to.
If you look closely at the progression of grasshopper and super grasshopper flights you see that we are starting to learn this as well as try to feel out more limits at the edges of the envelope of the vehicle. Basically if you take off from a concrete pad (grasshopper case) you light the engines and go to max power to get the hell out of dodge as fast as possible. When coming back in you do the same thing but in reverse, come in hot hit the engine just enough to be able to slow to so the "impact" is low enough the vehicle can handle it. Think of it like a jet landing on a carrier, they set themselves up into a 5-700 FPM descent and just fly it into the deck. Effectively we are doing the same thing here so that we can minimize the heating on the barge or landing pad or whatever you are landing on.
The flame ducts at all the launch pads (including ours) is amazing. The idea is to just redirect the plume 90 degrees and shoot it off to the side. If you start to erode things then you just start throwing more water at it. Brute force approach at its finest
Now when we start talking about very high delta V missions AND a return to launch site vehicle ... ya fuel is going to be a very very close one. But one step at a time haha
Ya clapping hands is actually a decent comparison. The barge stays in a programmed spot and stays in place via some sort of thruster. The vehicle is headed toward that same spot, regardless of whether there is a barge there or not. The last soft landing we did where the barge wasn't around was because of the storm and that the barge couldn't maintain position in those winds and currnets. And the swells were like 25-30 feet ... way over what we predict we could do ... Poor dudes stuck it out a for long time but when the final delay came they said screw it we are going home.
Interesting, I would have figured there was a real-time uplink of GPS data for the precise location of the landing coordinates, in the event it moves due to currents?
The link between vehicle and barge is tough to rely on though and it is also tougher to test with all hardware in the loop. It's not perfect that is for sure but like mentioned it's an easy corner to cut as the barge is just temporary thing (I think it is anyways). It works really well actually until the currents become too large or a storm comes through. The barge cannot react quickly speed wise (just a big boat). The vehicle can react but only within a small window as well.
Ya ocean is much safer. Looking at how to deal with landing back on land is pretty interesting. All vehicles launched have an auto destruct command on them (brick of C4, really high tech haha) so they can keep it from gong over populated areas etc. The problem with coming back into the launch site is your trajectory is towards the land. If you blow the vehicle your debris field could still be areas that aren't restricted or cleared. So do you run an auto destruct? Or do you just fly it into the ground? More issues that Space X is bringing to the forefront lol. It would also suck to blow up someone else's pad with our vehicle ...
I still say this had to have been a hair brained idea that just got out of hand. 5 years ago I would have said BS edit .. correction I DID say it wasn't going to work* .. no way we will be able to recover it like this. The retro burn is amazing ... supersonic speeds and fire a rocket engine with supersonic gases right into one another ... all I know is that it is working
I am grateful we have Elon to think outside the box, and to do the impossible. No one else is doing anything for the betterment of society like he is on the same scale.
I have my own opinions about that but really the rocket industry has been stagnant since the shuttle was developed. The X-37 is the only newish thing out there but we also don't know anything about it. NASA has been a complete dud since the 80s when it comes to launch vehicles.
