Physics & powered slingshot question?

[Tom Kalbfus]

Obviously not well. Atmosphere isn't very think and the ring would need to create a very intensive magnetic field for radiation protection.

The walls are 200 kilometers high, tall enough to hold in a standard atmosphere under 1 Earth gravity, it takes 47.29 minutes for a 2000 km wide habitat to make a complete rotation. The gravity at the surface is 1-g and 0.8-g at the top of the 200 km high wall. Since 100 km above the surface of the Earth is considered to be Space, a 200 km high wall should be tall enough. As for radiation protection, the 200 km wall, the floor and the atmosphere should provide protection from solar flares.

 

[Reynard]

Still no magnetic shielding so the inner area in the path of any solar flare is going to cook.

 

[Tom Kalbfus]

Still no magnetic shielding so the inner area in the path of any solar flare is going to cook.

The thing is artificial, so a magnetic field could be created easily enough, especially if its a spaceship with a power planet. if it generates enough power to self illuminate, it should have enough left over for generating a magnetic field.

 

[Reynard]

That is a LOT of power!

 

[Tom Kalbfus]

That is a LOT of power!

It is a giant starship after all, it takes a lot of power to go up to 5% of the speed of light, it probably has a fusion reactor of enormous proportions, and it creates artificial sunlight illuminating the habitable surface with visible light at about 1400 watts per square meter, the amount of power required to do that could probably also generate a decent sized magnetic field, in fact a starship like this might be a Bussard ramjet, using a magnetic field to funnel interstellar hydrogen into the intake of its fusion engine. This ship probably accelerates at 1/10,000 of an Earth gravity after 500 years of this it reaches a cruise velocity of 5% of the speed of light, at this point it continues to collect interstellar hydrogen to power its reactor, and illuminate its habitation ring, and it can continue to do this indefinitely. At 5% of the speed of light it takes 20 years to travel 1 light year, 5 light years take a century, 50 light years take one thousand years and so forth, but this starship is huge with a land area equal to India, so it could probably support one billion human inhabitants if it had to.

 

[simonh]

If a ship didn't match the inertia, it would go from zero to full G force as soon as they touched the surface.

For a 2000km diameter ring rotating once every 47 minutes, the ground (and air) would be whipping by at over 2000m/s. That's MACH 6.5.

Any ship that doesn't match rotation, and can survive travelling through the atmosphere that fast, would be torn to shreds trying to land.

I highly recommend entering the atmosphere while pointing the ship against the rotation, and re-entering that way unless you can at least fully match rotation first. Otherwise your ship will actually be travelling backwards relative to the atmosphere when you enter it (more precisely, the atmosphere will be travelling forwards relative to your ship, faster than the ship is, but the effect is the same). Most vehicles aren't designed to cope with travelling backwards in an atmosphere at high speed.

The alternative is to approach the outer rim of the station at a little ovre 2000 m/s in the direction of rotation. You'd have to time your approach so you get to the rim at the same time as some sort of 'cradle' type runway suspended from the under-side of the station, or perhaps sticking our at the rim. Fly into the cradle and land, letting the runway under you 'lift' you into synchronous rotation with the station. The advantage is you don't have to enter the ring first and then speed up to match rotation, or deal with the atmosphere. Scary manoeuver though.

Simon Hibbs

 

[atpollard]

For a 2000km diameter ring rotating once every 47 minutes, the ground (and air) would be whipping by at over 2000m/s. That's MACH 6.5.
Simon Hibbs

Good catch.
I was focusing on how easy it would be to rotate a ship 1 revolution in 47 minutes and never thought about the surface velocity of the rotating air relative to the ship.
It will be a lot like an atmospheric reentry from orbit.

I like the bottom runway idea ... reminds me of that Airship with the trapeze for catching aircraft. [EDIT: USS Macon]