this post was submitted on 13 Oct 2023
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It's even far from fuel free, to reach Low Earth Orbit a rocket needs between 9.3 and 10km/s of delta-v.
According to the video the system is launching the rocket at mach 6, which is equivalent to 2km/s.
So the system is providing only 1/5 of the energy needed to get to orbit. It's good but I'm not sure it is worth the drawback of having to handle the huge acceleration.
On the other hand the same system on the moon would provide enough energy to reach orbit, it would just need a small amount of propellant to circularize.
Or by increasing slightly the speed of the system it could even send stuff straight to earth with no propellant.
20% of the delta-v is not the same as 20% of the energy or fuel. The early stage when the rocket is the heaviest and down in the thickest atmosphere is by far the most fuel-expensive.
That actually makes it much worse. Kinetic energy is a square law so to reach orbit at 5 times the velocity requires 5x5=25 times the energy they're currently using. And air resistance is also a square law so making it go 5 times faster also results in 25 times the air resistance and 25 times the heating due to it.
Most likely if they did get it going fast enough to make it to orbit, it'd burn up in the lower atmosphere before it even got very far.
They don't need to get 100% of the orbital energy into the object at launch. Scarabic's point is that if it can just offer an alternative for getting through the lower atmosphere, it can save a lot of fuel.
So, you want to build a trebuchet on the moon to throw rocks at Earth?
Yes, who wouldn't?
Fuck yea