I’m going to be very disappointed if the rockets top out at 65mph.
In: Planetary Science
The ISS moves at a speed of roughly 7.7 km/s or 17’000 mph. It’s not getting up there that’s hard, it’s catching up to that speed.
Because you can not go to the ISS straight up in a line. You also have to match it’s orbital velocity, which is really high. Due to how orbital mechanics work, you can also not just increase your velocity much higher to get there quickly and then brake to match the velocity. That would need much much more fuel, which you just can not take with you if you launch the rocket. So the rocket launches in way that only part of the orbit would reach the ISS and then increases the speed to match the velocity. And for security reasons this is done in very slow steps. So that when the rocket and the ISS finally meet, their relative velocity to each other is in a safe range for docking.
edit: Maybe a good example would be if you want to jump onto a moving train. You can not just jump onto it by jumping down from a bridge of something. The velocity of the train compared to yours is so high that you will not be able to land in a stable pose and get thrown around.
But if you drive with a car or another train next to it at the same velocity, you can just jump over with only a minimal risk.
With the rockets we have now it takes roughly two minutes to get enough height to reach the ISS. Then a further 8 minutes to match the speed as it is going pretty fast. So about 10-15 minutes to get to orbit. The problem is that we are not extremely accurate when trying to hit an orbit first try. Just like on a golf course a good driver shot may have the distance to go all the way to the hole but not the accuracy and you will probably land just in the rough proximity.
So on a golf course you might aim a bit closer to make sure you land on the fairway and not in the rough. You then walk up to the ball and start over again evaluating the balls position and its trajectory as well as wind and other factors before taking another shot. This will bring in closer to the hole but not quite there so you rinse and repeat until you finally put the ball into the hole.
We do the same when docking to the ISS. We first launch into an orbit slightly behind and under the ISS. Then we take measurements of the orbit we ended up in and plan the next orbit changes to get closer to the ISS. Finally getting to visual range and then slowly bring the spacecraft close to the space station without hitting it and finally dock very carefully. But unlike golf which is fairly two dimensional when you are docking a space station you need to match seven dimensions, three locational dimensions, three velocity dimensions and time. Getting these to match is very complex. And sometimes you can do nothing but sit and wait for the spacecraft to slowly drift closer to the space station.
The fact that we can launch and dock a spacecraft to the space station in as little as 4 hours is an impressive feat in itself. It used to take a full day and night. Compressing it all down to 4 hours requires a huge effort but allows the astronauts to stay in their launch suits in their seats all the way which is more comfortable then having to spend the day and night in the confined spacecraft.
The iss isn’t 250 miles away. It is orbiting at a distance of 250 miles. Orbiting really just means it’s falling past the ground so fast that it constantly misses it
I imagine the problem in getting to the ISS is to get a rocket/ship from stationary in earth’s surface to moving fast enough and close enough to the ISS to arrive at it.
So here’s a fun mental image.
Rockets can get to the ISS in a couple minutes. Go straight up, intersect the path, and you’re good!
Except now the rocket is essentially a deer that’s run in front of a car on the highway. It’s going to be a mess.
If you don’t want just a mess, either the car has to slow to about the speed of the deer or the deer has to speed up to the speed of the car. One of those things is unlikely.
With rockets, it’s stranger. If the ISS slows to the horizontal velocity of the rocket, it’ll just fall from the sky. Bad day. So the rocket has to speed up instead.
It’s orbiting thousands of miles an hour so if you simply fire a rocket straight up into its path, you’ll have a gigantic crash. You basically have to chase down its orbit. That means inclining are an angle, rather than simply going up vertically, and then accelerating to about the speed of the ISS and intercepting it’s orbit. That’s the part that takes 4 hours. You’re traveling thousands of miles to actually intercept the orbit.
You dont go straight up. You go into orbit so that you can match the speed and approach it from the side.
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Because if you sent a rocket straight at it, you’re not going to dock with the ISS, you’ve essentially just fired a missile at it.
[You can watch a video of the docking procedure.](https://www.youtube.com/live/3FaUK7VAljc?si=4Xvh3MjIKaE8ggJw&t=4738) It’s pretty delicate. You need to match its speed exactly so you can gently dock without bumping into anything and breaking something.
So you need to get into orbit, which requires more elaborate maneuvres, you can’t go straight there.
It wouldn’t take 4 hours to get there if getting there was all that mattered. But if you’re going to the ISS you probably want to stay there, which means you have to go pretty fast or you’ll fall straight down again. Gravity at the altitude of the ISS is still 99% as strong as it is on the surface, if you’re not going fast enough you’ll fall straight back down to Earth.
The space station goes fast on account of throwing itself at the Earth and missing, so the rocket has to spend some time catching up.
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