ship design and G orientation

[Meng]

One of the technical aspects of spaceships (those foregoing the wonders of artificial gravity at the flick of a switch) using centrifuges or constant thrust to simulate gravity have always intrigued me how they compensate for the switch in orientation which is bound to occur at some time.
One of my former favorites at tackling this issue have been the presentation of ship-design in Jovian Chronicles by Dreampod 9. Particularly the Jovian navy which feature habitat modules that are capable of rotating or folding horizontal depending on which form of gravity is being generated. It seemed a simple and logical solution, especially for vessels that get around without any ftl drive whatsoever. Having a near 1 G constant thrust for extended periods of time would certainly prove useful for providing a confortable enviroment for human crewed ships.
My query is, as I read more about space travel in 2300ad, how much time do starships spend using 'conventional' chemical reaction/fusion/whatever thrust and how long would they spend doing it? My impression is that 'not for very long', 'not at such high levels of thrust' or a combination of both answers. I get this impression mainly from ship designs I've seen so far seem to be only concerned with ONE orientation for the crew on-board the habitat modules. That is, unless I've been blindly mistaken, so I'll be happily corrected.
I have read in ship descriptions that decks are situated as I suspected - say if the ship is aligned bow to stern on a east to west plane, the decks will run parallel north to south. For reasons stated to 'take advantage of g forces during conventional drive thrust' or something similar. So, I think to myself, then what happens to all the crewmembers in the habitat modules? Are they strapped down during these times? Do the walls suddenly become the floors?
What do you folks think?

 

[Ptah]

Welcome Meng,
I'll start with I don't have 2300 but do like the ships. I think the pivoting thing is done in 2300 from some of the starship images I found here:

http://www.users.globalnet.co.uk/~dheb/2300/

You can see slots in the habitat part (presumably for the struts) in this one:

http://www.users.globalnet.co.uk/~dheb/2300/Equipment/SG/Nelson/Nelson.htm

 

[Uncle Bob]

Sorry, I just got my books out.

Stutterwarp has no accelleration. The thruster accelleration appears to be trivial, except for interface (landing) vehicles. It is not listed in any ship stats, so it cannot be significant in most cases.

The slots in the centrifuge modules are there to retract the modules when maneuvering or in combat.

The only floorplans I have seen are of the centrifuge areas, and Colin's aerospaceplane. It says in The Referee's guide that reconfiguring deckplans is trivial, so I think non-centrifugal areas of the ship are non-aligned, even chaotic.

The main hull is generally long and narrow, so it would be natural to divide it transversely, giving the impression of decks.

 

[Meng]

http://www.projectrho.com/rocket/rocket3u.html
Finally found a site that discusses the issue pretty well. Guess I'm a stickler for details like this, and it seems I don't need the site to explain. Though I was pleasantly suprised to see a draft of the very ship I had mentioned (jovian) right after the Pilgrim Space Observer Station, so I had to post the link. I'm not lauding Jovian Chronicles as a superior example (since not all their ships seem to share a very consistant design) just that they created some wonderfully thought out ships.
Though stutterwarp is used quite often to get around space, at some time reactive thrust is bound to be used. I'm not certain what speed equals what amount of Gs; I'm assuming the higher the better, and going over 1G is as far as you want to go. If this is the case, I would think alignment of ship and habitat decks to be crucial during this time or all hell would break loose. So the most practical solution would be to gimbal the habitats so their orientation keeps 'down' down while not in spin or vice versa. Every ship design I've seen so far (though beautiful as they are) do not seem to gimbal the habitat modules at all. Eh, it's Sci-fi and it's forgivable, but somehow I just can't let it go.

btw: it's good to be here, thanks.

 

[Dunryc]

Please keep in mind that the stutterwarp is a reactionless drive, so you'll only cover space and time with this device, but you are unable to get close to a planetar body or change your heading.

A) Due to the gravitional effects the stutterwarp is restricted with (from the ruleset) ... and
B) you can not change the vector (speed and direction) your ship is "drifting" to, the stutterwarp is only usable in the direction your bow is pointing to, but still you'll move where your mass is heading to. The stutterwarp will only displace your ship.

So our initial vector still holds true and you have to allign your ship (-> vector) to any planetary body or direction to move to.

You can not change the law of physics...

*cough* stutterwarp *cough*

Dun

 

[Ptah]

Originally posted by Meng:
...at some time reactive thrust is bound to be used. I'm not certain what speed equals what amount of Gs; I'm assuming the higher the better, and going over 1G is as far as you want to go. If this is the case, I would think alignment of ship and habitat decks to be crucial during this time or all hell would break loose. So the most practical solution would be to gimbal the habitats so their orientation keeps 'down' down while not in spin or vice versa. ...

On the first question, are you referring to speed of rotation of a habitat ring to give an apparent 1G? If so, then the formula is approximately:
P= 30 Sqrt(R)
where P is the rotational rate in RPM and R is the radius of the habitat ring. The 30 assumes 1G = 10 m per s^2 and rounds a bit but should be within 2% of the exact value.

If you refer to the thrust of the engines to produce 1G apparent, speed actually has nothing to do with it. It is your change in velocity, or acceleration, that will produce apparent gravity. In this case a 1G acceleration will produce an apparent 1G of gravity while you accelerate.

On the pivoting, if you batten everything down, maybe they just pivot the seats so in essence you are laying on your back during acceleration. So no loose gear on a warship, magnetic cups, pens and tools on ropes, etc. But does that mean no hot coffee! No wonder the U.S. lags behind in 2300.

 

[Dunryc]

For all who would like to know something about artificial gravity...

http://www.spacefuture.com/archive/artificial_gravity_and_the_architecture_of_orbital_habitats.shtml

enjoy!

 

[Ptah]

Hi Dunryc,
Welcome, nice link.

Meng, the formula I used above for P can be derived from equation (1) in Dunryc's excellent link, where the Omega and r vectors are considered perpendicular. So in the end the acceleration vector is in the direction r with a magnitude (the scaler portion) of (Omega^2)*r.
Converting radians/sec to RPM gives you 1 RPM = (2pi/60) = 0.105 radians per second. The apparent gravity scales with the square of the radial velocity Omega, thus if you needed only 0.5G, instead of 1G, you would need to spin only 1/4 as fast. The coriolis acceleration will be zero for someone standing still or walking around the ring (as v is parallel to Omega).

 

[Uncle Bob]

Maybe I wasn't clear. Acceleration, except for interface vehicles, appears to be trivial <0.1 G. And 90% of the time they will be on stutterwarp with no acceleration.

So deck orientation, except for the centrifuge decks, is not important.

 

[Dunryc]

Ok let's talk about deck orientation.
Acceleration has to be done with every ship which comes near a planetary body or has come to the stutterwarp threshold in a solar system.

Orbital bodies (-> i.g. planets) move around their sun(s) and their vector (speed and direction) doesn't have to be identical with the space craft's vector.
So every ship has to allign itself to it's target's vector. This has to be done by thrusters and this should take some time because you do not just allign to the direction the object is heading to, you have to match its speed too.

Therefore the time you'll be under acceleration will considerably more than the 10% you mentioned Uncle Bob. I believe the accleration phase up to 40% - 50% of the time the journey will be.
Just remember - you have to "stop" every 7.7 ly and allign yourself to a center of gravity in order to keep your stutterwarp from overload!

So every ship must spend consideable time under g (acceleration) and you have to consider this when building the spacecraft interias.

For example, corridors shouldn't be alongside the acceleration axis, because loose objects (and humans too) will not be accelerated with the ship, but will be smashed against the wall at the end of the corridor when the ship moves in the accelerations direction.

So decks shouldn't be build like decks in an airplaine (or shuttle), they should be vertical alligned to the acceleration's direction (parralel to the position where the thrusters are housed).

 

[Colin]

In general, that's how ships will be oriented, with decks perpendicular to the axis of thrust/movement. However, most ships do not use thrusters for orbital operations, using instead more exotic gravity captures/slings for velocity matching. Simply speaking, ships can't carry enough fuel for sustained thruster operations, even at fractional-G accelerations, nor are they built to withstand high accelerations.

A stutterwarp can be used for orbital operations, it just isn't very efficient. However, for most ships, it's still more efficient than a second drive/thruster package, or even carrying the fuel bunkerage required for a thruster. Stutterwarp cannot, however, be used for interface operations, thus requiring thrusters for surface-to-orbit work.

Thrusters beyond typical orbital manuevering clusters (OMCs) are NOT included as part of the engineering/power plant of any vessel, either in Star Cruiser/2300AD or in 2320AD. They have to be purchased separately. And usually aren't.

 

[Uncle Bob]

That is what I remembered. I couldn't find my Star Cruiser, though.

 

[BMonnery]

I modelled thrusters in the past. Making some assumptions I arrived at a house rule where ships had a limited number of "SC Turns", and each 60 degree turn on the SC table ate one. ISTR that 60-100 was the norm for nuke boats, which oddly, given my assumptions, had significantly less manouvring fuel than MHD ships (due to MHD ships having the ability to use their bulk fuel resevoir).

Combined with the "heat clock" effect (nuke boats actually produce more heat than they can radiate and so have a limited period at full military power. This also explains the relative lack of nuke powered civilian ships) it hamstrung nuke boats enough to have MHD powered cruising ships (frigates etc.) make a great deal of sense (especially when they have solar panels, and so can cruise /loiter fuel free in the system and can dial their drives back).