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Old 02-11-2018, 08:03 PM   #17 (permalink)
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Originally Posted by redpoint5 View Post
Was wondering about that too. The tires are subject to direct sunlight, and they are black which will absorb much of that energy. Since the vacuum of space insulates, it would get extremely hot. Perhaps they were filled with nitrogen so they wouldn't oxidize. In that case, the tires just have to resist getting gooey and deforming. Perhaps they are capable of withstanding a couple hundred degrees F and relatively low pressure.
The car was put into a slow rotation to heat up both sides of the car evenly (and maybe more importantly the camera equipment).

Originally Posted by redpoint5 View Post
I don't understand how landing the first stage is cheaper in the long run than using a parachute and recovery apparatus.

Extra fuel has to be loaded on the booster for the purpose of decelerating and landing it. When you load extra fuel on a booster, you have to load several times more fuel just to accelerate that extra fuel. In other words, most of the fuel spent by a rocket is used merely to accelerate the weight of the fuel. Finding ways to reduce the need for small amounts of fuel ends up allowing larger amounts of fuel to be saved.

How is the weight and simplicity of a parachute a disadvantage compared to the weight and complexity of powered landing and control systems?
A parachute would weigh less than the extra fuel, but doing controlled landing of a rocket that large into anything but water is very difficult. If you wanted to land on a barge with a parachute you would need a very complex and expensive apparatus to catch the rocket without damaging it. You'd also risk damaging a very expensive ship and apparatus. You'd also need a control system for controlled autonomous gliding of the rocket to a specific location. That's only ever been done with much smaller equipment, usually with helicopter capture.

Landing the rocket in the ocean with parachutes is fairly easy. NASA did it with the Shuttle boosters. The problem is that salt water is very bad for engines, especially when they're hot. Refurbishment would be very expensive, as it was for NASA even with their much simpler solid rocket boosters. You'd also need a large boat with a crane to retrieve the rocket. It ends up being a much more expensive proposition, especially since for most payloads, you don't actually need the extra payload capability.

Parachutes would also be impossible for SpaceX's upcoming BFR rocket, which is much larger. Parachute landings also don't work for landing large payloads on Mars, which is SpaceX's primary goal.

Lean burn baby!
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