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You underestimate how insane the power requirements of a high-g launch are. Placing one ton into orbit requires a rocket with close to 1GW peak power output (th
by mppm 1y ago
You underestimate how insane the power requirements of a high-g launch are. Placing one ton into orbit requires a rocket with close to 1GW peak power output (this is only a very rough figure that depends on mass ratio, thrust and exhaust velocity). Delivering this much power over 20 miles, even at 1MV, would take about a ton of aluminium wire (again, very roughly). The weight grows quadratically from there -- delivering this much power 200 mi downrange to the upper stage would take 100 tons, even setting aside all the other technical challenges. And this is where we actually want this power delivered -- we don't need to increase the ISP of the first stage, as it is mostly wasted in the exhaust anyway. An ISP above the capability of chemical propulsion is beneficial in the upper stage only.
- bilsbie 1y agoThanks for the feedback! A couple notes. Running your numbers through Ai it looks like it would weigh about one ton per km of wire. And possibly much less if you’re ok with more power loss and high wire heating. Since this is a short term use that might be fine. But on top of that the extreme amount of power is only needed because we’re trying to get up to speed as fast as possible to minimize gravity loss. If we’re not carrying our fuel for the first stage it’s conceivable we only need enough power to hover the unit and gradually get it up to top speed. I know it’s still a far out idea but might be workable from first principles.