Semi-OT: A General Tech Question Thread for me :) - Page 9

Starhawk · #81 September 21st, 2005, 11:10 AM

Trust me El Phil I've read a few different opinions on the "problems" that come in with rotating sections, which is in part why I asked about that idea here.

I've heard any number of things like friction, amount of power required yadda yadda that people threw at one another as to why or why not rotating sections would work.

kerensky · #82 September 21st, 2005, 11:36 AM

Rule number 37: There is no such thing as overkill. There is only "Open Fire" and "Time To Reload".

El_Phil · #83 September 21st, 2005, 12:16 PM

Given the choice between floating into scalding hot coffee when the ship stops accelerating or a rotating section I know what I'd choose... Full on artificial gravity.

If you don't like rotating sections then perhaps consider the rotating ship. An idea I got from a Heinlein book, essentially the enire ship 'rolls' along. No friction or bearings to think about, full gravity for the whole ship (admitedly variable strength, but you can't have everything) it seems clever. I haven't put that much thought into practical issues, but none are jumping up at me right now.

Wolfman77 · #84 September 21st, 2005, 12:33 PM

Wouldn't a rotating ship require alot more thrust to accelerate. Manuverability would also be greatly reduced, I believe, as it would be harder to change directions. Another problem turning when spinning is that the thrusters to move you into a turn would be rotating and would create a couple of problems, depending on how much you wanted to explain.

They would need to be pulsed on ond off in a serial order to keep thrust on just one side of the ship.

If you wanted to go farther into it, then that wouldn't work either as each thruster would still fire in an arc, not just at one point. It would be massively unstable.

I can't think of any way to explain around this, and there may be other problems I haven't thought ofas well.

Starhawk · #85 September 21st, 2005, 12:38 PM

Yeah like firing weapons lol think about it if your ship is rotating a cannon that was locked onto the enemy a second ago won't be after the ship rotates.

Also grav "plating" works for me for now as just looking at an Icaran ship it's clear there's no room for a rotating section in the design (see attached).

As far as constant acceleration goes I agree with you there it would suck to float into something if the ship comes to a sudden stop lol

El_Phil · #86 September 21st, 2005, 01:55 PM

Quote:

Wolfman77 said:
Wouldn't a rotating ship require alot more thrust to accelerate. Manuverability would also be greatly reduced, I believe, as it would be harder to change directions. Another problem turning when spinning is that the thrusters to move you into a turn would be rotating and would create a couple of problems, depending on how much you wanted to explain.

They would need to be pulsed on ond off in a serial order to keep thrust on just one side of the ship.

If you wanted to go farther into it, then that wouldn't work either as each thruster would still fire in an arc, not just at one point. It would be massively unstable.

I can't think of any way to explain around this, and there may be other problems I haven't thought ofas well.

How to solve that? Computer controled constant correction. Modern aircraft (F-22, Eurofighter) are 'dynamically unstable' airframes. You kill the computers and the plane goes out of control. Similar thing with this. Or just pre compensated burns, you allow for the fact the thruster is moving when you calculate the burns. You know all the factors that will affect the stability so it's calcuable, with fast enough computers.

Weapons however are tricky, it would depend on how fast the outer edge of the ship is spinning, which would depend on how much gravity you want in the ship and how big the ship is.

OR the ship rotates round its axis of movement. The main engines are mounted on the 'hub' of the ship as are your forward firing main weapons. Simplifies some of the problems certainly, if not solving all of them.

Wolfman77 · #87 September 21st, 2005, 03:08 PM

Yup, computers could do the trick there. And with some sort of Thrust vectoring you could control it's tendancy to pitch throughout each burn. It would still have poor manuverability though.

Nice ship, btw. I guess these problems won't matter for you ship much but they are still fun to discuss. Grav plating sound ok to me, but then I'm ok with just about anything in sci-fi. At least there are not any commonly accepted theories that prohibit it from functioning (well none that I'm aware of anyway).

kerensky · #88 September 21st, 2005, 04:10 PM

As far as shooting while spinning, I don't knw if this came from a book or video game, but the ships spun to keep gravity but when they went into combat or needed to do some tricky maneuvering, they killed the spin and everyone strapped in or floated.

El_Phil · #89 September 21st, 2005, 04:53 PM

That would work as well, the problem would be the inertia. Just because you stopped powering the spin doesn't mean it will suddenly stop, there's no resistance (or practically none) in space so you have to apply power to stop the spin. Not a big problem granted, you got it spinning in the first place after all.

Gravity plating. Wonderfull and how do you propose for this to work? Last I checked you needed mass for gravity.

Lets see how you would get this. OK use Newtonian gravitational theory, its fine for practical stuff involving small fields. And its a hell of alot simpler.

So to get earth strength gravity you need about 6E24 kilograms, or the mass of the earth, at a distance of ~ 6400 km. This isn't really practical to lug around, but your plating is on the floor! Say under a few cm of carpet (or funky futuristic space floorboards) lets say its 1 cm down. So you only need 9E15 kgs of mass to create that much gravity. Tricky. Oh and it's unidirectional so your crew on the deck below are being attracted to the ceiling.

Frankly I can't see how you can ever get that into plating and then directional. But I'd like to hear this theory that would be fine.

Baron Munchausen · #90 September 21st, 2005, 05:07 PM

In order for humans not to be disoriented (dizzy) from the rotation, a rotating structure must have a cycle time (complete rotation) at at least one minute. In order to get 1 g of acceleration in a 1 minute rotation time you need: 33 feet per second * 60 seconds = a wheel 1980 feet in circumference. (approximately 650 feet across) Since any 'upper' decks within that radius will have correspondingly less g, they'll have to be 'storage and utility space' and only decks that far out or farther will be regularly inhabited. So you'll need pretty large ships for a 'routine' 1 g environment. I suspect that colonies will eventually be built that have this level of gravity but I doubt that many moving ships will.

The balance factor is another sticky problem but I suppose it's more solveable than the sheer size requirements. In order to rotate effectively the ship/structure will have to be relatively balanced, but of course it will never be perfectly balanced. Various controls can be used, including thrusters and internal movement of material, like stored water or other fluids. Even with computer controlled pumps moving fluids around you can't have a response time or a margin of error that can handle humans running around doing their daily business. Another reason that rotating ships will probably be impractical but colonies will be important enough to deal with the problems.