# Launching spaceships from the outer edge of a rotating wheel space station

Based on Docking on the outer edge of a rotating wheel space station would it be impractical to launch ships off of the outer edge of a rotating wheel space station? Whether launching the ships along the tangent, or along the same plane as the tangent, just in a different direction?

• Have a look at Babylon 5 fighter launching. Their solution is for the craft to enter on the axis in zero G then lock to a transport system that carries them outboard to the launching racks. – pHred May 29 '19 at 4:37
• It's not free. As you move the ship up the elevator, the wheel's rotation slows down as part of it's inertia is transferred to the ship. "Dang, my dinner slid off the table again!" – user535733 May 29 '19 at 12:50

It would be quite straightforward to launch. If a ship is attached to the exterior of the station and detaches, its inertia will carry it away from the station without the need for any further thrust. This is nice if, for instance, you want to get clear of the station before cutting in your main engines so you don't damage anything.

The hard part is getting them to the outer surface in the first place. As noted in the other answer, landing there is more difficult than on other parts of the station. Also, a ship positioned there has to be held to the station against its own inertia with clamps or some other mechanism. You could move the ships "overland" from a docking station to a launching rail when it's time to go, but I question the usefulness of such an arrangement compared to just launching them into space.

• Other than the fact that it is "free" delta-V to the launchee and clean and safe to the launcher (no rocket exhaust), there's no advantage to a high-orbit station like the geosync ones that the OP has been discussing. For a 1G 150m rotating station, its only a 38m/s boost but in LEO that's probably enough to deorbit something allowing for its disposal or unpowered return to earth; a useful facility. – Starfish Prime May 29 '19 at 15:02

It might work if you take care of not perturbing the momentum of inertia of the whole station.

This either means that the departing ship has a very low mass as compared to the station, so that the momentum of inertia and the principal axis of inertia are not noticeably affected, or that you are launching/touching base with more than one ship with same mass in symmetrical locations.

The last option sounds rather unpractical, especially upon touching base, while the first one can be mitigated by proper engineering.

Not much point.

Assume that the station rotates to give 1g at the rim. We will also assume a 400m diameter station. This puts it on par with an aircraft carrier.

$$a=v^2/R$$

$$v=\sqrt{aR}$$

$$v=\sqrt{10m/sec^2*200m}$$

I would expect a station used for a fighter base would have both landings and takeoffs from the axis. Individual fighters would be in protected pockets in the walls, to minimize damage from crashing fighters.

Below the flight tube (deck isn't quite right...) you would have maintenance bays. Having a little gravity is useful for keeping stuff still. But low gravity means that replacing heavy components is easier.

The Flight tube has numerous cables strung the length of the tube. Shuttles that grip tracks much like rollercoaster tracks are used to move the fighters around.

Probably would still have a catapult for launching, and some form of wire catcher for landing.

• Hot exhaust plays hell on systems in a vacuum. Even on a carrier deck with air and a 25 knot head wind to dilute the hot gas, they deflect the blast upward.
• Some form of catapult allows rapid deployment of fighters, with them being only a few seconds apart.
• Allows unpredictable speed on exit.

Inertial accidents would be the main risk on both the flight and hanger levels. While gravity is reduced, momentum isn't. In 1/100 g you can lift a 5000 pound engine. But once it's moving, it has the same momentum as it would on earth. E.g. You lift with a 100 pound force. 50 of that cancels the weight. The other 50 accelerates it at 10cm/sec2. You strain for 10 seconds. Now it's moving up at 1m/sec. But at 1/100 g, it will take 10 seconds and travel 5 m up before coming to a stop. Now it's coming down. Are you ready to catch it? You can, if you do it right, but the risk is if you can't exert a similar force over a similar distance, and it just lands on your foot instead.