Maneuver Drives and Physics 101

[atpollard]

I am much better at dealing with forces on a static object than motion, so I need a check on my basic physics before I take a shot at reconciling the Book 2 and High Guard design systems.

If we assume that average mass and density are interchangeable in Classic Traveller (a 100 ton-volume ship masses about 100 metric tons, a 200 ton-volume ship masses about 200 metric tons, etc.) then:

If a 1000 dTon ship has an engine that produces enough thrust to accelerate that ship at 1G (9.8 meters per second), then installing two of these engines will generate enough thrust to accelerate the ship at 2G (19.6 mps) and six of these engines will generate enough thrust to accelerate the ship at 6G (58.8 mps.).

Are there any reasons in PHYSICS why this relationship would not hold true?

Is there any data in Traveller cannon (from other versions) that explains the strange Maneuver Drive progression in Book 5?

I have no objection to attempting to explain or rationalize the Book 5 formula and Book 2 tables, I just wanted to make sure I understood the basic real-world physics before I attempted it.

Thank you for your support.

 

[far-trader]

Originally posted by atpollard:
If a 1000 dTon ship has an engine that produces enough thrust to accelerate that ship at 1G (9.8 meters per second), then installing two of these engines will generate enough thrust to accelerate the ship at 2G (19.6 mps) and six of these engines will generate enough thrust to accelerate the ship at 6G (58.8 mps.).

Are there any reasons in PHYSICS why this relationship would not hold true?

The problem here is we're dealing with a sci-fi handwave of either extremely efficient quasi-conventional thrusters or reactionless thrusters so we can't really make any real Physics arguments.

You could actually do this in FF&S as I recall, without penalty.

I can see a good reason right off why you can't though. Not that the "engines" (whatever they may be) themselves are the problem but having two (or more) "engines" will require more control mechanics, more stuctural support, more fuel/power feed, more maintenance access, and so on, above that required simply for the engine itself. So any formula of "base engine + aux engine = total thrust" should include a "base engine size + aux engine size + aux engine control = total engine size" formula I think.

So the relationship of thrust you outline holds true but the actual drives may not be scaled linearly due to other systems associated with them.

 

[mike wightman]

LBB2 first edition says this:

Only one of each may be installed in the engineering section...

meaning only one of each drive - no stacking of maneuver A drives allowed

Revised edition misses this line out, I can't see anything in the rules to prevent drive stacking.

 

[atpollard]

My primary concern is to verify that

Force = mass x acceleration

is the correct equation to determine acceleration. Reactionless or reaction drive, doubling the thrust should double the acceleration. I know that this stuff breaks down at relativistic speeds (a flashlight in space will never accelerate to the speed of light) but I wanted to make sure that there was no other exception to the formula that might impact Traveller.

I have no real problem with B2 and HG not scaling directly with acceleration [well, to be honest, I have a little problem with it - it is darn inconvenient for creating modular starships - but I can live with it].

 

[atpollard]

Originally posted by Sigg Oddra:
LBB2 first edition says this:
</font><blockquote>quote:</font><hr />Only one of each may be installed in the engineering section...

meaning only one of each drive - no stacking of maneuver A drives allowed

Revised edition misses this line out, I can't see anything in the rules to prevent drive stacking. </font>[/QUOTE]Of course virtually every illustration and deck plan of a free trader or scout ship with one reactionless Manever Drive A depicts two jet like projections from the rear and two "drives" penetrating the rear wall in the deck plans. It was not until T20 that I saw a scout ship with one large glowing rectangular "thruster plate" at the rear. There may have been other accurate artwork, but I just did not see it.

 

[Andrew Boulton]

One possibility:

Drive tonnage = 2%
Inertial compensators = (a-1)%, where a = max acc'n

 

[aramis]

One nitpick: in MT, TNE (BLTA & FF&S), and T4 (FF&S2), average density is more like 10 tons metric per Displacement ton.

 

[Arthur Denger]

Originally posted by far-trader:

So the relationship of thrust you outline holds true but the actual drives may not be scaled linearly due to other systems associated with them.

I suspect you are right about the linear scaling. There's good reason why conventional (Tech 6-8) rockets use staged engines instead of just a single massive cluster of them. It has to do with mass. So, reactionless system or not, would adding additional maneuver drives not also demand a corresponding increase in powerplant mass?

 

[Ptah]

Originally posted by atpollard:
My primary concern is to verify that

Force = mass x acceleration

is the correct equation to determine acceleration. Reactionless or reaction drive, doubling the thrust should double the acceleration. I know that this stuff breaks down at relativistic speeds (a flashlight in space will never accelerate to the speed of light) but I wanted to make sure that there was no other exception to the formula that might impact Traveller.

F=m*a; but if you are going to work with the equation I'd suggest using the F=m* dx/dt^2 formulation.

I still remember a student that once told me d=at^2, why? because d=vt, v=at, so d=at^2.

Originally posted by atpollard:

I have no real problem with B2 and HG not scaling directly with acceleration [well, to be honest, I have a little problem with it - it is darn inconvenient for creating modular starships - but I can live with it].

It is darn inconvenient, but one way to put the breaks on reactionless drive. With reaction drives you still need to carry the fuel, so there is a built-in additional limit. Reactionless drives need some hard-wired game-rule limit since we don't have any physics to help us.

Or do we? I like to look at the first word of this genre science, and not focus on the fiction part. You can certainly handwave and say "because" but I'd rather look for a current physics we do understand and use it as an analogy (with useful game-limiting physics) and/or look at the questions and trouble spots in a current area of physics.

One area that provides great analogies for the justification of sharp steps in game design is qunatum mechanics. Why not, as the enrgy levels of an atom, moecular vibration, etc. are quantitized by the principal quantum number why not reactionless drives? This leads to easy 1G, 2G, etc. but no 1.5G drives.

It could also be used to explain why 2x1G drives don't give 2G, postulating that the energy to get 2G is not twice but 4 times say that of 1G. And not to get into EP, let's just say this comes up in the amount of drive needed to project the energy. This is similar to the non-linear spacing of quantum energy levels, of course in reverse.

Another question is does mass matter in CT reactionless drives. That is, is the reactionless drive really providing a thrust. If you want it to then F=m*a should allow for drive stacking.

If mass doesn't matter (i.e., it truly is a volume effect), then F=m*a doesn't work for reactionless drives. That doesn't mean the drives violate the "laws of physics" as F=m*a applies to the movement of objects obeying Newtonian physics, which is just an approximation, a very, very, very good one, of realtivistic physics which describes the fast, and quantum mechanics which describes the small.

With this view, the reactionless drives are not generating a thrust that moves the ship, although it's conveniet to talk in terms of thrust. Rather, it is moving a volume (space), and everything in it, relative to an observer at a certain acceleration, dx/dt^2. So stacking drives does not necessarily work to move the volume at a greater acceleration, but maybe can move a greater volume at the same acceleration.

Just my views for MTU.

 

[Ptah]

Originally posted by atpollard:

]Of course virtually every illustration and deck plan of a free trader or scout ship with one reactionless Manever Drive A depicts two jet like projections from the rear and two "drives" penetrating the rear wall in the deck plans. It was not until T20 that I saw a scout ship with one large glowing rectangular "thruster plate" at the rear. There may have been other accurate artwork, but I just did not see it.

Those are not drives but waste heat vents. Really I hope we are not limiting ourselves based on the artwork and deckplans, the deckplans themselves have been noted to be way off volume-wise.

I'm not sure what you are after with this topic. Are you looking for canon explainations, all across canon; are you looking for rule-book explainations; are you looking for general principals on which to base the reactionless drive effect and see what falls out?

 

[atpollard]

Originally posted by Andrew Boulton:
One possibility:

Drive tonnage = 2%
Inertial compensators = (a-1)%, where a = max acc'n

Good thought.
I was trying to brainstorm a "why" for the +1% per G increase in the B5 formula. Inertial compensators make sense. At least it keeps all of the "hand-wavium" in one basket. Violating conservation of momentum may not be a simple linear process.

 

[atpollard]

Originally posted by Aramis:
One nitpick: in MT, TNE (BLTA & FF&S), and T4 (FF&S2), average density is more like 10 tons metric per Displacement ton.

Good to know.
Civilian ships, military ships or both?
The actual value of average density will not affect the basic linear or non-linear relationship between thrust and acceleration. As long as the average density does not vary based on ship size, mass will be directly proportional to volume and I can use dTons in the basic equation.

 

[atpollard]

Originally posted by Ptah:
Another question is does mass matter in CT reactionless drives. That is, is the reactionless drive really providing a thrust. If you want it to then F=m*a should allow for drive stacking.

If mass doesn't matter (i.e., it truly is a volume effect), then F=m*a doesn't work for reactionless drives. That doesn't mean the drives violate the "laws of physics" as F=m*a applies to the movement of objects obeying Newtonian physics, which is just an approximation, a very, very, very good one, of realtivistic physics which describes the fast, and quantum mechanics which describes the small.

With this view, the reactionless drives are not generating a thrust that moves the ship, although it's conveniet to talk in terms of thrust. Rather, it is moving a volume (space), and everything in it, relative to an observer at a certain acceleration, dx/dt^2. So stacking drives does not necessarily work to move the volume at a greater acceleration, but maybe can move a greater volume at the same acceleration.

Your hypothesis does a better job of explaining some of the quirks in Traveller than the Classic Physics approach. Why do the drives not loose power at very high velocities? No accelerating mass to C removes the realtivistic paradoxes of infinite energy accelerating infinite mass. On a more practical note, it explains the lack of starship projectile weapons and why an unarmored ship is not destroyed by hitting a pebble at 0.2 C. If space moves then objects in space bend around the ship’s “bubble”.

This deserves more thought.

 

[atpollard]

Originally posted by Ptah:
I'm not sure what you are after with this topic. Are you looking for canon explainations, all across canon; are you looking for rule-book explainations; are you looking for general principals on which to base the reactionless drive effect and see what falls out?

My goal is to attempt to create a fitted curve equation that will produce Book 2 size drives in ships from 100 to 1000 dTons and Book 5 (High Guard) size drives in ships over 5000 dTons and to transition smoothly from 1000 to 5000 dTons. And I want to create a graph of this equation with certain critical points marked (100, 200, and 400 dTons for the Scout, Free Trader and Far Trader, plus certain logical values 1k, 2k, 5k, 10k, 20k, 50k, 100k, 200k, 500k dTons, plus maybe a few others). And I would like to create a Book 2 like table for some of the most common values. With this data, one could quickly throw together a Book 2 ship using the table, or design a less common size using the graph, or create a unique ship using the formula and a good scientific calculator. All of the ships would be compatable since the equation matches the graph which matches the chart; only the number of choices differ.

I am not sure it is even possible, but I do know the B5 non-scalable maneuver drives will create some difficulty expanding from a simple curve for 1G Maneuver Drives to allow 2G through 6G Drives. What I want to avoid is beginning this undertaking with a fundamentally flawed view of how the real science should work that will corrupt all my efforts.

To provide an analogy, it would be like calculating weapon damage based on the momentum of the bullet if damage is more correcly modeled based on the kinetic energy. A bad initial understanding will skew the results.

If this project is successful and Game values can be shown to reflect general real-world values, then it could form the starting point for modeling other types of Maneuver Drives – including thermal rockets or solar sails – in Classic Traveller game terms.

The very long term goal is to merge B2 and B5 into one system for designing all ships that will support B2 ship to ship combat or B5 fleet vs fleet combat.

“A man’s reach should exceed his grasp, or what’s a Heaven for?"

 

[atpollard]

Originally posted by Ptah:
I'm not sure what you are after with this topic. Are you looking for canon explainations, all across canon; are you looking for rule-book explainations; are you looking for general principals on which to base the reactionless drive effect and see what falls out?

The short answer is all of the above. I am looking for ANYTHING that will be usefull to modeling Maneuver Drives in Traveller and the "real-world".

 

[Ptah]

Originally posted by atpollard:

Your hypothesis does a better job of explaining some of the quirks in Traveller than the Classic Physics approach. Why do the drives not loose power at very high velocities? No accelerating mass to C removes the realtivistic paradoxes of infinite energy accelerating infinite mass. On a more practical note, it explains the lack of starship projectile weapons and why an unarmored ship is not destroyed by hitting a pebble at 0.2 C. If space moves then objects in space bend around the ship’s “bubble”.

This deserves more thought.

Thank You. I must mention that IMTU I also limit the max. velocity reactionless dirves an obtain and would require that the kinetic energy of the ship has to be supplied by energy put in by the power plant. This makes conservation of energy pretty easy.

I've seen the "bubble" idea. My own particular brand of heresy views the "bubble" as a useful concept but it doesn't prevent matter or energy from impacting the ship.

All of this are just IMTU type postulates that try to provide a basis for reactionless dirves (I love them because I hate to track fuel use) and prevent abuse/muse on the what-ifs.

I can throw out some quantum mechanics talk if you like. As advanced physics go that was my forte, it came with the spectroscopy territory.

 

[Ptah]

Originally posted by atpollard:
Originally posted by Ptah:
The short answer is all of the above. I am looking for ANYTHING that will be usefull to modeling Maneuver Drives in Traveller and the "real-world".

A worthy goal. I'm happy to give you MTU whys and wherefores on reactionless drives. I keep them seperate in operational principal from reaction drives.

It's really late for me here so it will have to wait. Just quick posts at lunch and at the end of the work day, still at work actually. Feel free to PM me as I may forget.

In short, I try to ensure/explain:
Conservation of Momentum,
Conservation of Energy,
Maximum Velocity for Reactionless Drive,
No Varaible Ship Performance (e.g. uping G's by dumping modules/changing volume),
Integer Accelerations, and
Why ships don't melt.

It's all make believe, but consistent make believe that I hope prevents game unbalancing stuff.

 

[mike wightman]

For CT.

Give each letter drive a number - A = 1, B = 2 C = 3 etc.

A maneuver drive generates "dT thrust" equal to 200 x drive "letter".

To determine final maneuver G rating divide "dT thrust" by hull size tonnage and round down.

You can find the extended drive potential table this generates in this thread.

My explanation for how the maneuver drive works in CT is:
the maneuver drive consists of several sub-components, notably the inertial mass reduction field generator (IMRFG) and a plasma rocket or ion drive.
The IMRFG produces a field that reduces the inertial mass of the ship (and also deflects harmful radiation away from the hull), while the plasma rockets/ion drive produces a thrust that would only produce hundredths of a G acceleration if not for the mass reduction.

 

[atpollard]

Originally posted by Ptah:
I can throw out some quantum mechanics talk if you like. As advanced physics go that was my forte, it came with the spectroscopy territory.

Please keep it simple, as a Civil Engineer/Architect I still prefer Newton's Laws and view Einstein's relativity with some suspicion [Relativity and Quantum Mechanics are just a flash in the pan - we will eventually find a nice algebraic formula that will put this nonsense to rest. ]

 

[TheEngineer]

Hi !

The only way to "drive" something reactionless is to place it into a gravity field.
So CTs drives create a connection to another spacetime region, which causes a spacetime curving = gravity field. Thats why the ships dtons are important for drive field size but mass is not relevant. And there is nothing like thrust, too.
The connection properties itself limits the amount of space bending/accelaration.
Guess thats a classical "freefall drive"

...

regards,

TE