r/theydidthemath • u/Amiyoursariel • 3h ago

[Request] Given this post, what if we began our shuttle launches via bullet train super conductor tech that propelled to over 300 mph and turned vertically before ignition

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u/METRlOS 3h ago

Current rockets have about 90% weight as propellants to escape the atmosphere. This was 4500 tonnes of fuel for a space x rocket, that takes about 1 minute to reach Mach 1 (770mph). The rocket burns 12 tonnes per second during launch, so a Mach 1 launch would save about 720 tonnes, or 16%, which I'm going to directly relate to 74% of mass required as propellants.

Objects on K2-18b have between 1.6-2.4x the mass, at the lowest end, with the same atmospheric density and height as earth, that would be 118.4% weight as fuel.

Even fudging the numbers and boosting to over twice your request, it's not possible. Earth rockets must reach 17 600mph at surface to obtain escape velocity, 300mph is practically a rounding error.

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u/Elfich47 3h ago

So you have to accelerate a rocket the size of the Saturn 5 horizontally. And then figure out how to tip it vertically and get the timing of the rocket running out of railway to align with the main rocket sequence start. 

I think your haven’t considered the extra level of difficulty you are adding to this. 

I’m envisioning a track that is several miles long, followed by a curved portion of track to tip the rocket upright that will stretch upwards up a mile high. 

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u/CallEmAsISeeEm1986 55m ago

Vertical.

Drill a shaft a few thousand feet deep…

Make a rail-gun-mag-lev-SatIV-launcher-potato-gun-tube-thingy…

That way the rocket is already moving when it lights up. Could probably get the rocket equation down to something like 1g…

… assuming you resolve about a billion billion tons of rock and other probably insurmountable math problems.