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
The ISS is not static. It’s orbiting, which means anything that wants to get to it and not just ram it, needs to match its trajectory. So the rocket is actually getting into a (largely) circular orbit itself, such that it will intercept ISS, adjust and match.
Put differently if the only thing the rocket did was travel 400 km upwards it’d fall right down
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