The ISS is around 400km above us. A rocket needs a speed of at least 8km per second to get to space. If we cut out the acceleration part it could in theory reach the ISS in around 50 seconds. Even if we factor in the acceleration part etc. it should still be very quick up there. Yet the fastest possible time to get to the ISS is 4 hours. That would be an average speed of 100Km/h which is way slower than the speed of the rocket after a few seconds. Why the long journey?
In: Planetary Science
I feel like the complicating factor everyone is missing is the orbital mechanics. Maneuvering in orbit is rather counterintuitive and complicated when it is in reference to another orbiting body.
Getting to the orbital plane of the ISS, 400km, is one thing but once your there you have to reach it too. On a highway you’d accelerate to catch up to them, but in orbit this has the effect of raising your orbit. But you won’t go up in altitude right away, your orbit is raised on the opposite side of the planet and your altitude goes up as you make your way around, however you’ll consequently also start slowing down relative to anything in orbit at the altitude your started at and you’ll actually fall behind your target instead of catch up.
So you see it’s really not as simple as just driving full beans on an intercept course unless you intend to hit it like a missile, which the ISS would really rather you didn’t. Rendezvous with the ISS for docking takes a lot of carefully timed and planned out maneuver to reach the correct side of the ISS at the correct speed and trajectory and with zero chance of accidentally setting yourself on a collision course and that just takes a lot of time.
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