# The great conversion of MegaTraveller starships back to High Guard

I have tried very hard to avoid starting replies with words like "actually, nope, wrong" as I have come to the conclusion people immediately think I am being snarky even when that is not my intent. I still make mistakes but am trying to come across a little less confrontational

Do you mean MegaTraveller here? I am not a fan of the handwavium DGP wrote to "explain" thruster plates.

No, this is your error. If they have the same acceleration then they have identical "thrust to weight" - The BB drive produces a larger "force" than the fighter drive.

If the BB and the fighter have 6g acceleration then everything in the right of the equation has to equate to the same answer.

6g =F(BB)/m(BB) = F(fgt)/m(fgt)=BB(handwavium)=fgt(handwavium)

So completely different. Also in space you can spin about your centre of gravity, something an ocean ship can not do.

I'm not surre you have a picture of how the thrusters work. They have to be in pairs (x,-x), (y,-y}, (z,-z)

If I want to spin about the x axis I fire the x and -x thrusters, this produces circular motion about the and has no effect on forward momentum.

Once I have altered my pitch, roll and/or yaw I fire the main engine, this alters the forward momentum vector, by doing this randomly for a few minutes at a time then the future position becomes more difficult to predict.
Me too. Thanks for holstering the snark. It's good to have honest disagreements without the add of snark.

The reference to mass in ships goes back to original CT. I forget which version it got removed in. We are in agreement about the DGP explanation.

Just to be clear, thrust to weight implies you know the weight (or mass if we are in space) of the object and the ft/lbs of your engine providing thrust. That's a typical thrust to weight explanation for aeronautics. To be more explicit here, the thrust to weight changes continuously for an aircraft in flight for many reasons. You can also refer to an aircrafts mass on the ground and the maximum thrust at 100% operating power for a more static number. Traveller provides no mass numbers, only displacement. I probably should have started with rockets and not planes for this as it's a better analogy as aircraft get lift from wings and Traveller ships do not. Using rockets as the example, your thrust to weight ratio has to be greater than 1 to lift off from a 1G world as you derive no lift from your vehicle. It also get a bit wonkier as rocket fuel has multiple varieties with a higher specific impulse than say aviation fuel. And, of course, it's not a good analogy to Traveller as they use energy for movement. Without actual data this conversation will go nowhere. Your formula does site the active ingredient here - lots of hand wavium.

Not sure how much you study naval technology, but over the last decade or so the use of thruster pods (aka azipod) has really taken off for all kinds of ships - including military ones. I've seen a 85,000 ton cruise ship do a 180 from the dock. It's fitted with thruster pods so it does not need any tugs. These also are electrically powered. Some ships are doing away completely with shaft/rudder systems and going with azipods/thrusters. Azipods can actually shift a ship sideways - though drag must be overcome.

While yes, you can spin on your axis with your main engine, it's not actually shifting the ship sideways - it's just spinning in place. Thrusters (using the conventional definition) are meant for maneuvering and not ship movement like it's main engine. Traveller doesn't posit the invention of azipod technology since it did not exist in 1977. Subsequent versions since CT (aside from SOM - which actually is closer to azipod operations) have retained engines in back that push the ship forward under newtonian movement characteristics. The more massive a ship is the more energy required. That's why I cited the Space shuttle RCS/OMS engine types. OMS is used to push it (Traveller main engines) and RCS is used to spin it (Traveller thrusters). To be fair, a Traveller ship will be fitted with bow and stern thrusters (laterally and ventrally) and could use them to shift itself without spinning, then fire the opposite ones to cancel out the momentum. The problem with that is conventional wisdom says they are just there for maneuvering (i.e. turning) in space and the main engine is there to actually move the ship. Technically it's a correct statement, but also something that shouldn't used to justify such movement. Now, if you hung your engines on pods fore and aft then you would have a much more valid point. Engineering wise while you could go with a single pod fore/aft, I would expect them to be in pairs for greater control and flexibility.

Current manoeuvre drive has vectored thrust, though in diminishing returns.

While yes, you can spin on your axis with your main engine, it's not actually shifting the ship sideways - it's just spinning in place. Thrusters (using the conventional definition) are meant for maneuvering and not ship movement like it's main engine. Traveller doesn't posit the invention of azipod technology since it did not exist in 1977. Subsequent versions since CT (aside from SOM - which actually is closer to azipod operations) have retained engines in back that push the ship forward under newtonian movement characteristics. The more massive a ship is the more energy required.
That is just word games with non-Traveller definitions. In Traveller parlance "thruster" or "thruster plate" is the conventional gravitic M-drive.

By SSOM:

Attitude control is provided by a subsystem included in the "manoeuvre drive" system consisting of both thrusters and gyroscopes.

Whether the thrusters are movable or not is of course completely undefined by either CT or MT. Azipod is just a trademark for a specific movable motor mount. E.g. water-jet propulsion with movable nozzles have been around since the 30s and can provide side-ways thrust:

https://en.wikipedia.org/wiki/Pump-jet

Trust vectoring of rockets were used from the 30s and by most rockets e.g. the V2 and the Saturn V, so was a well known concept in the 70s.

https://en.wikipedia.org/wiki/Thrust_vectoring

There is no need to shut down the main thrusters to adjust the attitude the spacecraft, you just vector the main thrusters a bit reducing the thrust slightly, adding to aux. thrusters to rotate faster.

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It sure would be nice if the Starship Operator's Manual, or an updated version of it perhaps, were to cover thrust vectoring and actual engines on gimbals.
[Slurps tea loudly]

Since MgT has a magic gravitic maneuver drive with an extensive drive plume anything is possible.

Personally I am going to stick with my explanation come what may -

the maneuver drive reduces the inertial mass of the ship thanks to a field generated by the maneuver drive gravitics, and then ion engines provide thrust

acceleration compensators can bias this field to negate "lateral g forces" as they put it

I still have no idea how to explain null grav modules or artificial gravity floor plates - although handwaving tachyonic field condensation should do

the maneuver drive reduces the inertial mass of the ship ...
You can of course house-rule anything you want, but reducing inertia significantly creates more problems than it solves.

E.g. sophonts would bounce around like rubber balls inside the ship without inertia to resist movement. On the good side I guess it wouldn't hurt much to bounce off the walls (or ceiling)...

You can of course house-rule anything you want, but reducing inertia significantly creates more problems than it solves.

E.g. sophonts would bounce around like rubber balls inside the ship without inertia to resist movement. On the good side I guess it wouldn't hurt much to bounce off the walls (or ceiling)...
Not so, the internal fields of the ship, the grav plates and the compensators, control the environment so a passenger can't tell if the ship is moving, as per canon.

Gravity: Most ships have grav plates built into the deck flooring. These plates provide a constant artificial gravity field of 1 G.
Acceleration compensators are also usually installed, to negate the effects of high acceleration and lateral G forces while maneuvering.
A ship's passengers would be unable to tell whether they were moving through space or grounded on a planet without looking out a viewscreen.

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Next up, how gravitational tiles are configured.

Can they be implanted on top of the hull, to convenience external maintenance?

How far does the artificial gravity extend from the grav plate?

That's never been answered, as far as I know.

Especially, when you consider cargo holds and hangars.

How far does the artificial gravity extend from the grav plate?
The only canon I can recall:
Consolidated MT Errata, p25:
If you do install grav plates and/or inertial compensators, you need to install them in the entire hull volume.

It may well be a pair of "grav plates" with a field between them?

Not so, the internal fields of the ship, the grav plates and the compensators, control the environment so a passenger can't tell if the ship is moving, as per canon.
So the M-drive reduces the inertia, and the compensators puts it back in again but only for people?

Reduced inertia is not compensatable by a grav field, an acceleration. A grav field can't compensate the lack of resistance to your own motion-forces.

It just seems a lot more complicated than the canon system of thrust compensated by thrust in the other direction.

No, the m-drive reduces the mass or inertia of the ship as a whole, the grav plates and compensators maintain the environment within the ship such that the passengers think they are on a 1g planet, (or whatever you set the g field to).

It doesn't compensate for thrust in the opposite direction it negates the effects of high acceleration and lateral G forces while maneuvering.
F=ma
so a=F/m - put another way the acceleration compensation manipulates the F/m bit to make a=0

The only canon I can recall:

It may well be a pair of "grav plates" with a field between them?
CT states only floor plates.

CT states only floor plates.

HG'80, p17:
Tech level requirements for maneuver drives are imposed to cover the grav plates integral to most ship decks, and which allow high-G maneuvers while interior G-fields remain normal.
One mans floor is someone else's ceiling...

No, the m-drive reduces the mass or inertia of the ship as a whole, the grav plates and compensators maintain the environment within the ship such that the passengers think they are on a 1g planet, (or whatever you set the g field to).
And what happens when you move your arm or throw a ball? Your muscle use its normal force, but without inertial resistance the arm will be flung away and you with it...

A grav field (an acceleration) can't compensate for that.

Current explanation appears to be that the (onboard) manoeuvre drive creates an equivalent (counter) field effect that neutralizes the effects of acceleration.

Current explanation appears to be that the (onboard) manoeuvre drive creates an equivalent (counter) field effect that neutralizes the effects of acceleration.
No, canon is a grav field opposite to the perceived inertial acceleration.
Tech level requirements for maneuver drives are imposed to cover the grav plates integral to most ship decks, and which allow high-G maneuvers while interior G-fields remain normal.

But we were not discussing canon, but Sigtryggs house-rule.

Another important feature of all manoeuvre drive systems is gravitic compensators or ‘G compensators’. These enable a ship to engage in high levels of thrust without adversely affecting the crew contained inside. Ships are typically equipped with enough gravitic compensation to counter whatever Thrust score the ship has. Therefore, a ship with Thrust 4 is also equipped to compensate for 4 Gs of thrust.

The reason it would need to be field effect, is otherwise you'd need to incorporate it within the entire hull.

The problem with incorporating in the entire hull, is that you'd need to create local fields, otherwise there would be hundreds of micro tractor/repulsor beams per tonne, utilizing quite a lot of bandwidth, trying to ensure everything within the hull stays put.

And what happens when you move your arm or throw a ball? Your muscle use its normal force, but without inertial resistance the arm will be flung away and you with it...

A grav field (an acceleration) can't compensate for that.
Yes it can, this is magic handwavium after all. If it can already do the impossible adding a bit more shouldn't be an issue.
The inertial/acceleration dampers (note the mutually exclusive physics there inertial is to do with mass, acceleration is acceleration) provide pseudo inertia to mimic being on a 1 g world regardless of what the ship is doing.

Yes it is absurd, but then so is artificial gravity and acceleration compensation.

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