The Power plant

[Uncle Bob]

Deck grav is a scifi staple, but it is theoretically much more difficult than contragrav vehicles. Think about it: to lift an air-raft you have to cancel 4 tons of mass, but 1 G deck gravity is simulating millions of tons under the deck.

One of the nice things about B5. The Terrans had star drive with centrifuge habitats, but only the high-tech mimbari's had deck gravity. Which was why most starship interiors were filmed on Mimbari-designed ships.

 

[Malenfant]

Originally posted by Uncle Bob:
Deck grav is a scifi staple, but it is theoretically much more difficult than contragrav vehicles. Think about it: to lift an air-raft you have to cancel 4 tons of mass, but 1 G deck gravity is simulating millions of tons under the deck.

Also, unless there's magic gravity-cancelling tech incorporated onto each deck, only the bottom deck of a ship should have the 'deck grav plates' on it. If each deck has it, then there has to be ceiling plates on each level to cancel the gravity so that it isn't cumulative on the higher decks.

 

[far-trader]

Originally posted by Malenfant:
Also, unless there's magic gravity-cancelling tech incorporated onto each deck, only the bottom deck of a ship should have the 'deck grav plates' on it. If each deck has it, then there has to be ceiling plates on each level to cancel the gravity so that it isn't cumulative on the higher decks.

Yep, that's why my AG is a single field effect, set when the hull is laid and limited to operating within the hull only. It is usually set up to simulate 1G (and some folk can tell the difference between the simulation and the real thing under certain conditions). No AG pong is a bonus to my mind.

As long as the powerplant is operating the AG is on. The only way to turn it off is to turn off the powerplant. Configurable internal gravity is possible, in very limited areas and effect, by installing repeller plates to cancel part of the AG effect. Like my bunk mattresses.

There are ships IMTU that don't have AG fields laid into the hull, like the CT Type L Lab Ship which relies on spin gravity or chooses to operate in zero-g conditions for certain experiments.

I also don't see AG working at opposing angles in close vicinity, like the idea of having usable walls and ceilings in addition to the floor in the same room, especially in counter to the local gravity field.

And my IC is a field effect as well, similar to AG but tied directly to the ship's maneuver drive. It compensates only for directly applied thrust so you feel it if you get hit by something (or you hit something) and if your drives go off-line so does the IC (which is no biggie as it only compensates for thruster changes anyway).

 

[Fritz_Brown]

If you assume a small enough relative point for the gravity effect, Mal, you don't have that problem, per the inverse square rule. Of course, that means you get a layer of floaty dust that hangs in micro-G somewhere near the ceiling....

 

[far-trader]

Under those conditions wouldn't you also walk a little funny, with your feet being their normal weight (under 1G AG) and progressively lighter up your body to your head that feels like a ballon? Bending over to pick something up would do a number on your equilibrium too I'd think.

 

[Malenfant]

Originally posted by Fritz88:
If you assume a small enough relative point for the gravity effect, Mal, you don't have that problem, per the inverse square rule. Of course, that means you get a layer of floaty dust that hangs in micro-G somewhere near the ceiling....

Not sure what you mean by "small enough relative point" here. I mean, usually 1g is generated by the mass of an entire planet beneath us. I'd guess that 1g grav plates have to be generating gravity as if they were on the surface of a planet with earth radius and mass, which means that if you go vertically up by a metre from the floor in the ship then it's like you're going up a metre from the floor on earth - i.e. the difference in gravitational field is negligible on that scale.

 

[veltyen]

You could always go down the B-grade scifi path.

Heavy boots and big fans in the ceiling

 

[mike wightman]

Going back to Einstein's famous theory for a second, if you are in an elevator with no windows being pulled upwards at an acceleration of 1g every experiment you do gets the same result as if you are on the surface of a 1g planet.

Artificial gravity is an accelerating reference frame - like the elevator being pulled upwards - it is not a distortion in spacetime equivalent to a planet.

How's that for a handwave...

 

[Golan2072]

Originally posted by Uncle Bob:
One of the nice things about B5. The Terrans had star drive with centrifuge habitats, but only the high-tech mimbari's had deck gravity. Which was why most starship interiors were filmed on Minbari-designed ships.

Remember that the Babylon 5 station itself, the main filming location of B5, had rotation gravity. The Minbari deck-gravity effect was IIRC created by their manouver-drives, which were "magneto-gravitic", as opposed to the Narn or Earth fusion or ion drives. So part of the drive's field was applied as an inertia damper and deck-gravity field.

Still, rotation gravity is a viable hard-scifi staple; however, it probably won't work well on small ships, not to mension streamlined one (its the main reason most Babylon 5 capital ships are unstreamlined; the Narn Cruiser is partially streamlined, but has no deck-gravity at all, and the minbari ships are, ofcourse, streamlined).

 

[Golan2072]

A few previous threads about hard-science drives and powerplants:

- Nuclear Rockets in the real world
- A Universe without Artificial Gravity...
- Low-Tech maneuver drives
- Space Elevator

But anyway, I don't think that Traveller lends itself well to very hard-science ship technology; alot of the staples of the setting are semi-handwavium, from Jump Drives (semi-handwavium but a must for an interstellar campaign) to long-term high-G acceleration.

 

[coldwar]

The magnetic drive riase's a qeustion of does it really need to have access to the outside of the ship(like rockets etc)
And the second qeustion is that a gravitic drive will not operate by Newtons Laws as any other vessel would

 

[stofsk]

Hanwavium and unobtanium are kind of a must for space opera, though I suppose I could be wrong.

Lack of hard science doesn't bug me, it's the sci-fi brain bugs which do. Brain bugs can be anywhere, from 'hard' sci-fi to soft.

 

[Fritz_Brown]

Originally posted by far-trader:
Under those conditions wouldn't you also walk a little funny,

Well, yeah. It's the Traveller equivalent of sea-legs.

Originally posted by Malenfant:
Not sure what you mean by "small enough relative point" here. I mean, usually 1g is generated by the mass of an entire planet beneath us.

Or, Mal, you can simulate a tiny planet with massive density just 1 inch under the deck plate. It all depends on your choice of handwavium when conceptualizing artificial grav.

If you choose the right distance/density combo, you get negligible grav at the next deck, but something approaching normal most of the way to the ceiling on this deck.
(I may have done the math wrong, but I get that the AG point has to simulate 1G at .86m from the center - that gives .05G at the next deck, but it still gives only 0.066G at the ceiling.)

 

[Plankowner]

If the entire floor plate is producing the gravity effect, it won't follow the point-source rule, nor the inverse-square law.

As I recall, within 0.5R of the floor, the effect would be essentially constant, then be linear to about 0.8R, then considered a point source from there. R is the RADIUS of the floor or panel.

Given that the entire floor of the ship (entire Deck 1) would be generating the AG field, you would be able to go several decks before there is a noticeable drop in Gravity.

Take a standard size room 5mx5m. Simplify that to an R=5m. Then the "constant" G would extend up to about 2.5m, well above the ceiling. Add four of these rooms together with common deck plating and R=10m. Now you can go 5m up before noticable changes in gravity would occur. That's 2 1/2 decks and we are only talking about 4 rooms.

I may have the R distances off a bit, it's been 20+ years since I looked at the formulas.

 

[Fritz_Brown]

You are right if you are assuming the floor equals the curvature of whatever is producing the gravity. If you assume it comes from numerous point sources, though, things go different.

I'm not fighting over this, just trying to throw out some alternatives.

Now, what was this thread about, again?

 

[Uncle Bob]

Actually you use the same equations you use for a charged electrical plate, like a capacitor. The strength of the field is essentially constant as long as the floor is apparently very large. Edge effects will tend to weaken the gravity and slant the direction.

Having ceiling plates as well keeps the force-lines straight so you have unidirectional gravity at constant strength between the plates. Edge effects are much less apparent, but it will make interior cabins more desirable.

BTW, on B5 it was expliitly stated that the Mimbari had gravity control and the White Stars clearly had deck gravity perpendicular to the direction of flight. As did the Excaliber in "Crusade", also built with Mimbari technology.

 

[Straybow]

The bigger question for me has always been why fusion power requires such huge quantities of fuel?

Here in reality, fission powered carriers are able to put aircraft, weapons, spare parts, etc. in the 30%+ hull space a diesel powered ship needs for fuel.

Fusion power would supposedly be an order of magnitude greter efficiency (power/unit fuel). Yet in High Guard fission power plants are posited as a low fuel alternative to fusion plants...

Some of my thoughts are found in the Going Pirate thread (also before and after the linked post).

 

[stofsk]

I thought it was the jump fuel which takes up the most amount of space.

 

[far-trader]

All depends on what design rule set we're talking about. CT Book 2 has a lot of fuel for the powerplant, compared to pretty much every other version. And it's tied to powerplant output rather loosely. I always took it to be mostly coolant and thruster reaction mass in Book 2.

 

[Anthony]

The only version of Traveller with remotely sane power plant fuel requirements is GURPS Traveller -- where the fuel supply in a fusion reactor lasts as long as the reactor, and thus the reactor never needs refueling.

Of course, 'never needs refueling' isn't very interesting.