Bunch 'o Thoughts and the 6G Limit

[Supplement Four]

The 3G safety limit is why roller coasters are limited to 3G's positive. Most small airplane hard turns are 2G-3G.

A human can withstand much higher exposure to G force if it's for a short period of time. A hard slap in the face can produce up to 16 Gs of force locally. Bunji jumps bring force of about 3 Gs.

Wil, remember we're talking about long term exposure.

Resistance to "negative" G force (that will drive blood to the head) is about what atpolard said: 2-3 Gs. That's the threshold where a human will "red out".

With a pressure suit and training, a human can withstand about 9 Gs for a prolonged period of time, so our 6 G limit won't be an issue.

Now, if we're talking about G force perpendicular to the spine, a human can withstand a lot more Gs for an extended period of time.

Check out this wiki: http://en.wikipedia.org/wiki/G-force You'll see a NASA chart showing different tolerances, depending on the direction of force.

 

[mike wightman]

Look at the scout ship deck plan. The crew switches off the g compensation and now down is towards the engines.
Any hostiles are now going to have to climb a vertical shaft to get to the bridge, and each room now has it's exit in the ceiling.
Similar problem for the merchant ships we have deck plans for.

Also the x-boat has no maneuver drive and yet does have artificial gravity

 

[mike wightman]

IMTU the maneuver drive reduces the inertial mass of the ship so that a plasma/ion drive can actually push the ship at whole g ratings rather than fractional ratings.

According to Traders and Gunboats accelerration compensators are a separate component - T&G page 7 gravity.

Artificial gravity is provided by the magic of grav plates, also a separate component.

 

[aramis]

A human can withstand much higher exposure to G force if it's for a short period of time. A hard slap in the face can produce up to 16 Gs of force locally. Bunji jumps bring force of about 3 Gs.

Wil, remember we're talking about long term exposure.

Long term, stuck in couches on your back but survivable, is 3G's... for normal healthy people. Arthur DID NOT qualify it. sustained 3G's positive is considered safe. 2G's toward the head is potentially lethal; but Arthur didn't qualify it.

Most people won't be able to function. I've read the NASA publications on it. Repeatedly. Negative G's, whole 'nother issue... but for transient turning G's, 3Gs are minor. For sustained thrust holding you on your back, it's not a major issue for over an hour...

 

[atpollard]

Go reread the NASA data. 3G's is safe, and sustainable, for most people. It's not FUNCTIONAL, however. Most people will be couch-bound at 2G's, or even 1.5. However, most people don't realize that a typical roller coaster is 2.5G's.
The 3G safety limit is why roller coasters are limited to 3G's positive. Most small airplane hard turns are 2G-3G.

You are talking g-minutes of exposure ... what happens at 2 gees for 7 days (like a trip to a gas giant to refuel) where the exposure is on the order of 20 thousand g-minutes.
Wikipedia puts the 3 gee limit at around 30 minutes to loss of conciousness.
... and while not NASA, the chart on THIS page places the limit on 2G at less than 500 g-minutes (less than 250 minutes or about 4 hours). Not enough time to reach the 100 diameter jump limit.

But you are correct that I did not qualify my statement and 3G is not instant death, just a slow inevidable loss of conciousness over roughly an hour (or longer if you are pinned to the 'floor').

 

[Supplement Four]

Also the x-boat has no maneuver drive and yet does have artificial gravity

Does it?

If so, that's another good point against the WD article.

But...what if the X-Boats mean 1 week of travel in zero-G...

 

[Supplement Four]

According to Traders and Gunboats accelerration compensators are a separate component - T&G page 7 gravity.

Yep, I believe you can get the WD article (or a synopsis of it) on Andy Slack's page, where he states that it was a neat and good rule that was ruined by the official compensator definition when it came out.

Before that was printed, though, and all there was was 1st edition Traveller, it was a pretty good rule.

 

[Supplement Four]

So, basically, what we're saying, is that anything outside of 1G can be sustainable for a short period of time.

If you're going to speed at 2Gs of force on the crew and passengers for 2 days, then you need to have them all in pressure suits and acceleration couches.

Under the WD article (written pre-official definition of the Traveller compensators), your drives would look like this.

Drive     Acceleration     Compensation       G Force
====    =========     =============  ==================
 1G         1G                   0G                    1G (direction of drive)
 2G         1G                   1G                    1G
 3G         2G                   1G                    1G
 4G         2G                   1G                    1G
 5G         3G                   2G                    1G
 6G         3G                   2G                    1G

 

[mike wightman]

Traders and Gunboats does indeed mention the x-boat having artificial gravity.

The beaty of CT before any of the supplements etc were published was everything was house rules.

Just because it was in WD does not mean it's any better than any other fanboy's house rules (i.e. mine )

 

[boomslang]

But...what if the X-Boats mean 1 week of travel in zero-G...

Well, since Xboats have that big dish antenna that needs pointing, we can assume they have physical (as opposed to laser) gyroscopes for attitude control.

The solution then would be to use the gyros to get the Xboat spinning like a top, and then use the resulting centrifugal force as a g-plate substitute...

But that's just crazy talk...

 

[Supplement Four]

Well, since Xboats have that big dish antenna that needs pointing, we can assume they have physical (as opposed to laser) gyroscopes for attitude control.

The solution then would be to use the gyros to get the Xboat spinning like a top, and then use the resulting centrifugal force as a g-plate substitute...

But that's just crazy talk...

Crazy talk, sure...but now you're thinking outside of the box...now you're talking!

 

[mike wightman]

Except the deck plans show this not to be the case.

The only Traveller ship to use centrepetal force for g simulation is the lab ship (as my old physics teacher said - no such thing as centrifugal force )

 

[DaveChase]

Lets assume that a 1G gravity compensator(GC) can handle 100% effects at 1G movement. And lets don't forget about nondirectional movement. Think StarTrek where everyone thought it was silly that with artifical gravity that they would get thrown around when hit or high G evading. (Obviously their GC could only handle so much nondirectional movement.)


What ratio should we use for the higher G's.

That a 1G GC can only handle 50% of 2G?

The way I have played it is that gravplates only give you artifical gravity in a direction.
The standard option, no extra cost floor units are part of the price of the hull. And you can control it from ZG to X G with X being normally only 1G unless you pay for a higher abilitiy. (Gravity Skilled people could get a bit more out of the unit by Skill level x 10% x the units normal max. ie Gravity 2 could get 1.2 G out of a 1G unit.)

Now for those higher G drives you will need a higher GC floor unit (or ship unit if you think as the whole).
Once again it was considered standard IMTU that paying for the drive unit would also cover the cost for higher GC unit to make you feel like it was only 1G during normal movement.

So at the following levels
Drive Feels like Compensation
1G 1G 100%
2G 1G 200%
3G 1G 300%
4G 1G 400%
5G 1G 500%
6G 1G 600%

What I also allowed was for every 4 tech levels above the commonly found drive you could double your compensation factor.
ie
1G is available at TL 8 so that TL 12 you could make 1G feel like .5G or you could handle 2G and still feel like your only at 1G

Now for the cost factors if you wanted a higher GC for your ship.
Each 1G of compensation extra cost equal to 50% of drive cost plus took an additional 50% of drive space.
Using CT rules LLB 2 a Maneuver Drive B normally costs 8MCr and weighs 3 tons.
To double your GC ability it would cost 12MCr and weigh 4.5 tons
Or to triple your GC ability it would cost 16MCr and weigh 6 tons

Now I did this to make it have some benefits for the player along with some disadds so the players would have to think about which to purchase. A bigger drive at the same cost or more GC for less space.

Just a gearhead thing

Dave Chase

 

[aramis]

Except the deck plans show this not to be the case.

The only Traveller ship to use centrepetal force for g simulation is the lab ship (as my old physics teacher said - no such thing as centrifugal force )

That alone would get him fired 'round here...

Centrifugal force is the outward force generated as a result of applying centripetal force to an object in motion. It's very real. It's a corollary of newton's laws of motion.

It also is vital to orbital dynamics. When the centrifugal force exceeds the centripetal force (induced either by field effects like gravity or magnetism, or by contact with an unyielding substance, as in stations and slings), the object moves outbound.

 

[Straybow]

A rocket produces acceleration for itself and the structure of the ship transmits the forces to the occupants and payload. But no kind of rocketry produces anywhere near the amount of thrust for the amount of time specified in Trav. Even using mystical 100% efficient emission of 0.9999...c particles.

The only alternative is direct manipulation of gravitation-like fields into assymetric gradients of the fabric of space to produce net acceleration.

There are mathematically two ways to do this. One is the dense field solution. A "U" magnet with a bar across the ends has very little measurable magnetic field. Any manipulation within results in negligible net outside forces. This would be the inertial compensation type of "grav" field.

Deck plating "pulls" down and ceiling units "push" down, creating a relatively strong internal field for the mass of equipment involved but little outside effect. Objects within are joined by the field, so that a force (eg, explosion) that moves the structure is conveyed through the field, so that occupants feel no or little force subject to the energy limits of the field generators.

An open field gradient will cause all objects within it to be accelerated proportional to the gradient at the coordinates within the field. A large ship would then experience differential acceleration, greatest near the drive, diminishing with distance by some formula we have to make up (since at present we don't have any working artificial gravity theories).

I choose inverse-distance-cubed for a-grav as it keeps effects highly localized. You could choose a larger exponent, but then you run into difficulty creating a smooth deck-gravity and i-comp. Inverse cube would be noticeably stronger at the top and bottom than mid-span, subject to any non-linearity near the emitters.

 

[Pagan priest]

I seem to recall that there were some ship deck plans that talked about having staterooms with variable gravity, and that the common areas of the ship could also be adjusted, but were normally set at 1 g.

In any event, what I had used in my games was a floor & cealing plate based grav field generating system with limited variability inside the ship, with the maneuver drives separate from this system. The reason for the 6g limit was that the drives had a built in compensator for their acceleration, and 6g's was the best that could be nullified.

However, based on that idea, is should be possible to design a ship that boosted at higher than 6g's, simply by properly aligning the decks (as per AHL) and having the crew in couches and G-suits. So, if the deck plates can vary between, oh say... 0 and 2 g's, then is should not be too hard to set them up so they can be set for positive or negative g's as well. In other words, sometimes they give 1 g toward the floor, but can be set to provide 2 g's toward the cealing. Accelerate via maneuver drives plus an overbooster to 9g's, set the floor to -2g's, compensators cover 6g's, and the crew is comfy moving around at 1g. Put them in couches and G-suits, and boost at 12g's for a little while.

Certainly not canon, and I don't think that it would be a viable system for most purposes, but it could work for something like a pursuit ship or a rescue ship.

 

[Psion]

As to why the 6G limit... in game, it's anyone's guess (and it's hard to come up with a scientifically palatable answer. The best handwavy explanation I can come up with is limits of inertial compensators.)

But as for where it came from, I strongly suspect it came from Mote in God's Eye, where 6G was the limit. But there, it was the limit due to human survival reasons in couches designed for such a purpose.

 

[Jame]

I generally assume that missiles can accelerate at between 8 and 12 G.

 

[Psion]

I generally assume that missiles can accelerate at between 8 and 12 G.

There was a "special supplement" in an old JTAS issue that assumes the same.

 

[mike wightman]

No, it doesn't.

Maximum g for a missile in the special supplement is 6.