Ballpark, what fraction of a rocket launch fuel energy need to orbit is to overcome atmospheric drag as opposed to overcoming gravity? Anyone know off the top of your head?
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Ballpark, it’s about 9.5 km/s of delta v needed to get to ISS orbit (400 km). Of that 9.5 km/s ~1.5 km/s is to counteract drag. Translating that to fuel in the rocket equation should be pretty ez.
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Using a specific impulse of 500s (for simplicity), without drag you’d need an initial to final mass ratio of ~5 to 1. With drag you’d need a mass ratio of ~7.3 to 1.
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Now that seems more intuitively right than the 0.25% from the stack overflow estimate
It’s all about how the mass ratio is affected. If you want to do the math yourself (and note I’m on my phone and this is from my head) use:
Delta v = 9.8 m/s^2 * Isp * log (m0/mf)
For Isp used 450s (more realistic)
m0 = initial mass
mf = final mass
Delta v as above
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Per the payload to orbit improvement from an air launched setup would be ~5%... that’s taking into account reduced drag at altitude and the Mach 0.7-0.8 speed of the launch vehicle. So the answer seems somewhere in the middle.




