# How fast do we spin this for 'One g'

Following on from this question.

Question Context :

Mars second moon Deimos has been converted into a generation ship.

A considerable portion of its mass has been shaved off during the process & ejected backwards along its path by Railgun to help increase orbital velocity (if we need additional thrust to break orbit, perhaps nuclear explosions in a concave ablation shield could be used).

It's now a stubby rough formed cylindre with a length of at least 11 km & a width of some 5 km or more in which we've excavated 10 tunnels each 3 km long in two rows 1 km apart (so like 5 tubes with a 1 km plug in the middle of each strapped around a central tube).

Which leaves a 1 km thickness of rock to shield against radiation with an extra 1 km front & back (so 2 km there), the main propulsion envisioned is that of project orion, so the rear thickness can be considered additional shock absorption & ablation shielding.

This cylinder spins around its short axis fast enough to keep things in the tunnels on the 'ground'

The Question Itself :

How fast do we spin this for a centrifugal force of 9.80665 metres per second squared (One g) to mimic Earth's gravity on the 'floor' of our habitat tubes?

• Have you googled before posting?
– L.Dutch
Commented Dec 8, 2019 at 4:19
• @L.Dutch-ReinstateMonica : I had earlier & got nothing that made any sense or was useful but I may have simply been using the wrong search words because I've just found a couple that look like it might be what I need, I'll just delete the question while I look into them. Commented Dec 8, 2019 at 4:23
• @L.Dutch-ReinstateMonica : OK I won't delete it then, can't, it won't let me cos it has an answer on it now ;) Commented Dec 8, 2019 at 4:26
• You also have to be aware of and careful with the Coriolis effect, which can cause humans equilibrium problems. The moon needs to spin to generate the 'gravity' effect, but if it spins too quickly to create that, it may be disorienting to humans and cause space sickness. So a slower spin rate, and lower than 1g, may be necessary. Commented Dec 8, 2019 at 5:12
• Leaving the answer so that sometimes in the future someone doesn't come up with the same question for a different radius
– L.Dutch
Commented Dec 8, 2019 at 9:17

Internet is full of calculators if one searches for them.

From atomic bomb to asteroid impacts, people can calculate anything.

Spinning worlds included.

Here is just the first of the list I found by googling.

For a 2.5 km radius you get an angular velocity of 0.59 revolution per minute.

For a 1.5 km radius you get 0.77 rotation per minute.

• Ah now that's better th the one I'd just found, thanks. Commented Dec 8, 2019 at 4:25
• Assuming a 1 km thick core surrounded by our 1 km high tunnels that's a 1.5 km radius ~ so 121.3 meters per second for the tunnel floor (furthest from the centre) aka 0.77 rotations a minute ~ cheers :) Commented Dec 8, 2019 at 4:42
• Escape velocity for Deimos right now is only 5.556 m/s & we're losing a considerable amount of its mass plus the surface is another km further out so anything outside on the surface (that's not sitting on the nose or arse) better be tied down pretty tight :) Commented Dec 8, 2019 at 4:46