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Dec 22, 2015, 04:48 PM
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The rocket, you know the one



It was a good day, to be sure. Quite a thrill to see a rocket return from space to its launch pad, as it happened for the 1st time. Restarting a 1st stage engine 4 times & throttling it down enough to land is quite remarkable. The extra weight of the longer stage no doubt helped.

Humans dreamed of flyback boosters for decades, but how big of a success was it? Old timers remember the days when another vehicle was mostly recovered on every flight.

The shuttle had to throw away its mane fuel tank but recovered all 5 engines. Falcon 9 has to throw away its 2nd stage & 1 of 10 engines. We can estimate each vehicle throws away an equivalent fraction of its cost. The shuttle boosters required a large boating operation & several days to recover. Falcon 9 returns directly to the launch pad. Returning to the launch pad was once considered the hardest goal, so who would have thought it would be the 1st success.

Falcon 9 can only be reused when enough upmass is thrown away to allow it. So far, SpaceX has always tried to maximize the amount of upmass by packing as many payloads as possible, only using government flights to try landings. No matter how much the shuttle lifted, it was always recoverable. The question remanes whether SpaceX will budget more landing reserve now that they proved it was possible.

The shuttle boosters had to be completely rebuilt. The reusability was merely of the raw metal. The orbiter required months of refurbishment to repair tiles. Falcon 9 could theoretically be relaunched after refueling, but realistically could require as much refurbishing as a shuttle.

The Falcon 9 stage returned from 3723mph & 239498ft. The last shuttle boosters returned from 2997mph & 161528ft with not nearly as much downrange distance. It was a significant increase in difficulty to return Falcon 9, but a lot more of the shuttle's remaneing mass to orbit was still returned.

At least another piece is in place to launch much bigger payloads on 3 cores, recovering all 3 cores. In that case, 27 of 28 engines & 6 of 8 tanks would be recovered, a fraction of the total cost much larger than the shuttle. Considering it still costs millions to make a rocket engine, a 3 cored rocket lifting 50 people would probably cost each person 7 figures to ride, a significant reduction from the lowest 8 figure cost of any previous ride but far beyond any worker income.

Dreams of recovering the 2nd stage seem to have been dashed by the difficulty of recovering the 1st stage. Maybe not a 1 cored rocket, but a 3 cored rocket might have enough margin to do it with a traditional heat shield & parachute.

It was a sign of hope for the human race. 20 years ago there was absolutely no sense of it, but now more people are aware the human race won't survive without reusable access to space.
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