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My naive understanding: The appeal of a space elevator is that all you need to get to space is the energy to climb the elevator. But if Starship is able to hit
by oconnor663 5y ago
My naive understanding: The appeal of a space elevator is that all you need to get to space is the energy to climb the elevator. But if Starship is able to hit its "fully and rapidly reusable" goals, it will have basically achieved the same thing: You can go to space on Starship for not much more than the cost of fuel to get there.
The next question is which version is more energy efficient. Again, my very naive understanding is that they seem to be kind of similar. The space elevator is less efficient than you might think, because you can't just run electrical wires up and down it. The weight would be a problem, and resistance losses over such a long cable would be high. Instead, you might send power through the air with a big laser, but that also comes with efficiency losses, in the same ballpark as rocket engines.
And of course, Starship has the obvious advantage that it seems like it actually might work with current technology. I think this comparison is an interesting way to highlight what a big deal it will be, if Starship does work.
- mercutio2 5y agoI agree that space elevators are very unlikely in the next few centuries. But arguing that Starship achieves basically the same thing seems wrong to me. Starship is subject to the rocket equation. That means all but a few percent of its launch mass is rocket fuel. Space hooks of all sorts require some transfer of energy, but the idea is it's on the order of magnitude of the actual potential energy gained. Edit: It strikes me as implausible that we'll get unobtainium with sufficient material strength to build a space elevator without accompanying superconductors run through the elevator structure, but when I ran the numbers, current lithium ion batteries are about 1/60th of the energy density of mass moved from the highest equatorial point on earth to geosync orbit. Not so very different from the rocket equation, you're right, if we decide there's no way to convey energy through the space elevator. It's all sci-fi anyway!
- perl4ever 5y agoHow about an electric rail gun in a tunnel up a mountain? Has Musk ever said that's what the Boring company is going to do some day?
- panick21_ 5y agoA mass driver makes sense on the moon or Mars potentially, unlikely to make sense on earth. Even if you assume a sufficient good mass driver, you still need a rocket upper stage. And those mass drivers would always target the same orbit. You really have to construct a very specific scenario to beat reusable rockets anytime soon. On the moon if you want to mass deliver ice blocks to a specific fuel station it makes some sense.