Inauguration of mainland Europe's first satellite launch complex | Hacker News Reader

Inauguration of mainland Europe's first satellite launch complex

sscspace.com

31 pointsjcfrei8 comments

I guess with the big launches now being for LEO satellites, it’s better to optimize for lowest gravity (closest to the poles) rather than closest to the equator (closest to your destination)?

> lowest gravity (closest to the poles)

Isn't that quite the opposite?

https://physics.stackexchange.com/questions/141856/why-is-ea...

Yes, you’re correct, so now I have no idea why you’d site a spaceport other than on the equator.

Well, the only EU territory close to the equator is French Guyana and there already is a space port there.

I'm curious why Sweden and not, say, the south of Spain, Sicilly, south of Greece...

Esrange was built back in the 60s, so I guess it makes sense to re-use infrastructure rather than build something brand new

The Mediterranean is quite small and developed along all its coastlines. Sweden is relatively barren with a massive ocean alongside, making it far safer launch site.

My thought was you only preferred the equator when you’re launching a geosynchronous satellite.

If you’re doing Low earth orbit and your satellite it going to regularly cross Europe, it’s best to launch as close to the poles as you can because gravity is weakest there (but air is colder/thicker…)

If you are going to orbit, you need enough kinetic energy to stay in orbit along every point of the orbit. If it's a polar orbit, it covers every latitude, from north pole to equator to south pole.

The real advantage of launching from a pole, if you are going to a polar orbit, is that you don't start out with a velocity component due to Earth's rotation, i.e. perpendicular to where want to go. If you do, you'll have to spend part of your fuel budget canceling out that unwanted velocity component.

On the other hand, if you're going into an equatorial orbit (e.g. a geosynchronous one) you want to pick up as much of that free contribution from Earth's rotation as possible, so you pick a launch site on the equator, or as close to it as you can go.

Polar and equatorial orbits are opposite edge cases. In general, your orbit will be at some angle to the equator, and the closer that angle gets to 90 degrees, the closer to a pole you'll want to go for optimal launch latitude.

BTW, surface gravity is lower at the equator (9.78 m/s^2) than at the poles (9.81 m/s^2), exactly because of Earth's rotation.

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