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
Most of getting to orbit is reaching that 8km/s, that’s very fast
Most of the docking with the ISS is planning your rendezvous, so it happens at a nice and slow speed, and you use as little fuel as possible.
We can’t just say “the ISS is this way, so let’s go this way” we actually need to be in a slightly higher or lower orbit, depending on if we are ahead of or behind the ISS. We want our difference in speed to be very small, so we need our difference in orbit to also be very small, so we need to make multiple orbits with that small difference until we reach the ISS. Going near the ISS with a large speed difference can be very catastrophic
Latest Answers