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The patent is so general as to be useless. It says they would do a tail first landing, but no description of exactly what technology would be used to accomplish this. It would be akin to me patenting an intelligent robot, even though I have no clue as to how to actually build it. I'm not a patent lawyer, but I believe that's what the article means by saying the patent is indefinite.
Thanks for the link. Some scratchings follow:
* The January Falcon 9 flight attempted to land its First Stage on Just Read The Instructions (see, Claytorj? I just read the name, this time) when it was 600 km downpath from Cape Canaveral.
*from the link, the following: "SpaceX has designed the first stage of its Falcon 9 rocket to fly back to the launch site and land using leftover propellant."
* I'm envisioning a rocket's trajectory, with First Stage separating, and somehow turning 180º and getting back to Ground Zero. Wow - it does seem like a lot of work (=fuel). Not so much as to negate the cost-savings, but am wondering at what cost with respect to rocket's ultimate throw-weight (as reflected in the percentage of fuel that must be devoted to that maneuver vs flipping a payload to where it's gotta go)?
Here's an off-the-cuff estimate. (Data from SpaceX Falcon 9 v1.1 Data Sheet and Falcon 9 | SpaceX ) Total mass of a Falcon 9 v1.1 plus payload at liftoff is 404+99+13 = 516 tons. At first-stage separation, it has used 385 tons of fuel in 180 seconds to get the stack to 50 km downrange, 2400 m/s and 60 km altitude. To land in the ocean, they need the energy to essentially do that exact trajectory in reverse with a 19 ton 1st stage which weighs 3.6% of launch weight. So (ignoring messy rocket-equation calculations), it should take 3.6% of 385 = 14 tons of fuel to decelerate and land at the barge.
To get back to Canaveral, it's more tricky to calculate. With 680 tons of thrust from 9 engines, the 1st stage plus remaining fuel can decelerate at between 13 and 20 gees (as it depletes fuel), getting stopped in about 15 seconds. If we just want a parabolic trajectory that goes 50 km back to Canaveral in the 111 seconds it takes to fall 60 km, we need an extra 450 meters/sec, or about another 2.5 seconds of burn. After falling 60km, (and ignoring atmospheric friction), the stage will be descending at 1088 m/s, but almost entirely out of fuel and weighing not much more than the 19 ton empty weight. One engine is sufficient to decelerate to a hover in about 25 seconds at 4.4 gees. So: 17.5 seconds at full thrust + 25 seconds at 1/9 thrust at 2.1 tons/sec fuel consumption = 36.7+5.8 tons of fuel, or about an extra 10% of first stage fuel capacity. SpaceX certainly has designed a return trajectory which is more efficient than the simple model I'm using here.
Great job, evp! There should be an arithmetic relationship between fuel on board and throw capacity, so your scratchings suggest that the difference in payload capacity for a non-returning 1st stage and one that does go back to mama is something less than ten percent. Nicht wahr?
Nope, you can clearly see the name painted on the barge in this recent video
Assembly of Storm Barrier on SpaceX Barge/ASDS/JRTI on 2015-03-14
https://www.youtube.com/watch?v=Sq3BRoPcBc8&t=52
Johan
Ex got M3 in the divorce, waiting for EU Model Y!
Johan
Ex got M3 in the divorce, waiting for EU Model Y!
I think at the end of the webcast he said "no news yet, check our social media pages". Following on Twitter now, I don't have Facebook so hopefully someone else is following on there.
palmer_md
Member
only thing that I heard was sometime after 8 minutes they indicated that stage 1 was starting a burn (I assume for landing), but then nothing about whether it landed successfully, and as noted, they said check back for answers as they were signing off.
edit: from video T+7:49 - Stage 1 Transonic, then T+8:07 Stage 1 Alignment Burn Started, then T+8:23 ???
That is all the info I got from the original launch video.
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gavine
Petrol Head turned EV Enthusiast
Why don't they spin the rocket to stabilize it? Sort of like a gyroscopic affect. The way the last landing came in a little sideways and uncontrolled made me think that it would be much more controllable if it had some kind of spinning ballast. That's why UFO's from the old movies spun, right?
Why don't they spin the rocket to stabilize it? Sort of like a gyroscopic affect. The way the last landing came in a little sideways and uncontrolled made me think that it would be much more controllable if it had some kind of spinning ballast. That's why UFO's from the old movies spun, right?
It's tall and skinny, so it probably wouldn't have much angular momentum.
Plus spin does all sorts of things to liquid fuel that may not be desirable. Didn't an earlier attempt fail due to spin preventing fuel flow?
thelastdeadmouse
Member
gavine
Petrol Head turned EV Enthusiast
They don't have to spin the entire rocket. How about a ring at the base that spins to stabilize it?
Here's an interesting video demonstrating Gyroscopic Precession -->
Here's an interesting video demonstrating Gyroscopic Precession -->
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