Huge error in ship combat Manoeuvre Phase

[dragoner]

Take a physics class, you'll understand then:

From Newton's second law of motion, we can define a force F to be the change in momentum of an object with a change in time. Momentum is the object's mass m times the velocity V. So, between two times t1 and t2, the force is given by:


F = ((m * V)2 - (m * V)1) / (t2 - t1)

http://www.grc.nasa.gov/WWW/K-12/airplane/thrsteq.html

What is your mass again? That is your first side of the calcs, then you have to slow it down, don't forget to include the effect of the gravity wells and vector on both sides. :wink:

I'm sure players will love you for this.

Of course, if the goal is just to determine position and velocity, then mass and force are both unnecessary. If we were computing the energy requirements for the motion both are critical, but for the sake of our sanity let's not go there. Given the assumption that the power plant and maneuver drive can provide the force needed to accelerate the ship at the stated rate the computations become quite simple; all you need is current position, direction, and velocity and apply the acceleration and direction to find the new values for each turn.

I would highly recommend using a spreadsheet to keep track of it all, especially if one or more ships is firing missiles while franticly dodging all over the place as you can very quickly have dozens of individual objects to track.

If you are just speaking of kinematics, yes; however if including dynamics, mass is still important. Esp when figuring change in vector and external forces, etc.:

Forward Dynamics

For applications such as games and simulations of normal objects we can use Newtonian mechanics (as opposed to relativity or quantum mechanics)

Newton defines 3 laws (here defined in terms of particles):
1.If no forces act on a particle, the particle retains its linear momentum.
2.The rate of change of the linear momentum of a particle is equal to the sum of all forces acting on it.
3.When two particles exert forces upon each other, these forces are equal in magnitude and opposite in direction.

These laws can also be applied to rigid bodies by assuming that the forces are acting on the centre of mass of the object. Assuming that the mass is constant then the second law becomes:

force = mass * acceleration

For example, if the object is under the influence of gravity then: force due to gravity: force in Newtons= mass * 9.81

Euler extended these laws to include rotation. So there are equivalent laws for rotation such as:

torque = inertia * angular acceleration.

When working in three dimensions we can formulate these equations using vector and matrix notation, (see inertia).

http://www.euclideanspace.com/physics/dynamics/index.htm

 

[F33D]

No, that is incorrect.

:lol: Thanks, I needed that. I'll let Newton know.

Take a physics class, you'll understand then:

From Newton's second law of motion, we can define a force F to be the change in momentum of an object with <snip>

MgT ships use a GRAV drive that DOESN'T rely on OTHER grav wells. Hence, it MUST create its own grav well around the ship. It creates it by VOLUME. EVERYTHING in the VOLUME is effected REGARDLESS of the mass within. THUS, one power level to effect ALL mass withing a given volume.

So, YOU need to start over. :lol:

 

[dragoner]

MgT ships use a GRAV drive that DOESN'T rely on OTHER grav wells. Hence, it MUST create its own grav well around the ship. It creates it by VOLUME. EVERYTHING in the VOLUME is effected REGARDLESS of the mass within. THUS, one power level to effect ALL mass withing a given volume.

If that is your handwave fine, it makes no difference to me. When you do know physics, however, you will see that Matt was 100% correct to not include the multiple equations and just include a printed table for travel times.

 

[DickTurpin]

If you are just speaking of kinematics, yes; however if including dynamics, mass is still important. Esp when figuring change in vector and external forces, etc.:

At what point in the Maneuver phase of the combat round would we care about anything other than kinematics?

Forward Dynamics

For applications such as games and simulations of normal objects we can use Newtonian mechanics (as opposed to relativity or quantum mechanics)

“Games” here refers to using correct physics to allow realistic motion in video games; it has no relevance to Traveller as a pen and paper RPG.

Newton defines 3 laws (here defined in terms of particles):
1.If no forces act on a particle, the particle retains its linear momentum.

If no force acts on the object it continues on it’s current trajectory, no computations needed; mass and force (= zero) are unimportant.

2.The rate of change of the linear momentum of a particle is equal to the sum of all forces acting on it.

Exactly. All we care about is “the sum of all forces acting on it” (the acceleration and direction), not each individual component that adds to that sum.

3.When two particles exert forces upon each other, these forces are equal in magnitude and opposite in direction.

These laws can also be applied to rigid bodies by assuming that the forces are acting on the centre of mass of the object.

This would only matter if two ships collide. Even then I doubt that they could be considered “rigid bodies” as mentioned here. The ships would no doubt crumple under the impact. I would apply damage as stated in the Collisions rule on page 66 of the CRB rather than have the ships bounce around like billiards balls. At 1d6 damage per 10 kph I would expect really bad things to happen at the kind of speed space ships can attain.


None of this changes my original opinion that the rules, as currently written, are very playable for those who do not want to spend a big chunk of time grinding through the maths involved in correctly plotting the motion of each and every object in the area during space combat. I feel that such complications are not needed, some people feel differently. Dragoner and I are actually arguing the same side of the discussion, just with a different focus.

To sum up my viewpoint: I play the rules as written. If others want to add both complexity and realism, then they can (fairly) easily do so. The whole idea is for a group of people to have fun playing a game and each group should do whatever it takes to make the system work for them.

 

[F33D]

MgT ships use a GRAV drive that DOESN'T rely on OTHER grav wells. Hence, it MUST create its own grav well around the ship. It creates it by VOLUME. EVERYTHING in the VOLUME is effected REGARDLESS of the mass within. THUS, one power level to effect ALL mass withing a given volume.

When you do know physics, however, you will see that Matt was 100% correct to not include the multiple equations and just include a printed table for travel times.

Now you're just babbling as the table figures are derived from the omitted formulas. And, since a ship's cargo can be empty or full of lead without effecting acceleration, it would have to be set up the way I listed.

 

[dragoner]

To sum up my viewpoint: I play the rules as written. If others want to and both complexity and realism, then they can (fairly) easily do so. The whole idea is for a group of people to have fun playing a game and each group should do whatever it takes to make the system work for them.

Yes, agreed.

 

[dragoner]

MgT ships use a GRAV drive that DOESN'T rely on OTHER grav wells. Hence, it MUST create its own grav well around the ship. It creates it by VOLUME. EVERYTHING in the VOLUME is effected REGARDLESS of the mass within. THUS, one power level to effect ALL mass withing a given volume.

When you do know physics, however, you will see that Matt was 100% correct to not include the multiple equations and just include a printed table for travel times.

Now you're just babbling as the table figures are derived from the omitted formulas. And, since a ship's cargo can be empty or full of lead without effecting acceleration, it would have to be set up the way I listed.

So your complaint is that Matt got his peanut butter in your chocolate? Science plus fantasy equals gibberish, if you like it, that is fine; but don't then suddenly accuse others of wrong doing.

 

[DickTurpin]

At what point in the Maneuver phase of the combat round ...

The convo is about the travel times table.

Ah, I see. My mistake was assuming that the discussion was somehow related to the thread topic. I should know by now that any thread longer than a single page has drifted hopelessly off course. . .

In my opinion the Travel Times table has already been talked to death. To save you the time of digging through all those old threads, I will summarize them for you: If you don't like the tables, then use the formula instead.

 

[dragoner]

Funny story: Being so very old as I am, back in the dark ages when our professors at purdue wouldn't even let us use a calculator in class and every problem had to be done in multiple steps starting with the free hand diagram etc. (we also had to fight cthulhu on the way to lab but that's another story); my traveller group decided we should do lbb2 all realistically, finding mass by specific density etc.; the owen hall group thought we were crazy.

They were right. Good practice for exams though.

 

[MongooseMatt]

This is interesting. Based on your demographic data (which I'll grant is correct as you live the marketing side of it) young people today have really atrophied in the Int dept compared to 40 years ago.

I don't think this is true - you can find plenty of people who were at school 40 years ago who need their fingers to do sums, and you can find plenty of young people who are adept at maths and science today.

For our part, we do not presume our players are stupid. We just presume they want sci-fi action rather than maths problems. And we don't judge them for that.

 

[MongooseMatt]

From Newton's second law of motion, we can define a force F to be the change in momentum of an object with a change in time. Momentum is the object's mass m times the velocity V. So, between two times t1 and t2, the force is given by:

F = ((m * V)2 - (m * V)1) / (t2 - t1)

I'm sure players will love you for this.

I am not sure they would - it does not matter if they understand the laws of motion, or whether that simply passed them by. The number of players who actually want them as an active part of their games might well be countable on just two hands...

What I am trying to say, in the nicest possible way, is that no one else cares

 

[ShawnDriscoll]

I see no problem with players that want to use math in their RPG that doesn't have math in it. As long as the math is done in their heads or on a computer out of view from the other players, and math isn't being discussed during the game.

And since math isn't being discussed, it better be done quickly to keep the action in real-time.

 

[dragoner]

From Newton's second law of motion, we can define a force F to be the change in momentum of an object with a change in time. Momentum is the object's mass m times the velocity V. So, between two times t1 and t2, the force is given by:

F = ((m * V)2 - (m * V)1) / (t2 - t1)

I'm sure players will love you for this.

I am not sure they would - it does not matter if they understand the laws of motion, or whether that simply passed them by. The number of players who actually want them as an active part of their games might well be countable on just two hands...

What I am trying to say, in the nicest possible way, is that no one else cares

Yes, I am actually on your side, the bolded was sarcasm, sorry. 8)

 

[iainjcoleman]

I have over 20 publications in astrophysics and space science. I once spent a year of my life doing tedious calculations of the relative positions of various spacecraft in the solar system in order to trace the flow of the solar wind.

I really could not give a toss about "realistic" space combat in Traveller. This universe has magic constant-thrust drives and a don't-ask-don't-tell relationship with relativity. Slapping a bunch of detailed physics calculations on top of that lot is futile and pointless.

The Traveller space combat rules lend themselves to a cinematic style which emphasises the skills and actions of the player characters. And a jolly good thing too.

I'm not averse to bringing real science into Traveller, and I think it can often enhance the game. But, unless you're willing to rebuild space combat from the ground up and spend a whole evening on resolving a single encounter, this is not the place for it.

 

[ShawnDriscoll]

I have over 20 publications in astrophysics and space science. I once spent a year of my life doing tedious calculations of the relative positions of various spacecraft in the solar system in order to trace the flow of the solar wind.

I really could not give a toss about "realistic" space combat in Traveller. This universe has magic constant-thrust drives and a don't-ask-don't-tell relationship with relativity. Slapping a bunch of detailed physics calculations on top of that lot is futile and pointless.

The Traveller space combat rules lend themselves to a cinematic style which emphasises the skills and actions of the player characters. And a jolly good thing too.

I'm not averse to bringing real science into Traveller, and I think it can often enhance the game. But, unless you're willing to rebuild space combat from the ground up and spend a whole evening on resolving a single encounter, this is not the place for it.

If not Q.E.D., then the next best thing.

 

[dragoner]

This universe has magic constant-thrust drives and a don't-ask-don't-tell relationship with relativity. Slapping a bunch of detailed physics calculations on top of that lot is futile and pointless.

Precisely.

 

[SSWarlock]

This is interesting. Based on your demographic data (which I'll grant is correct as you live the marketing side of it) young people today have really atrophied in the Int dept compared to 40 years ago.

I don't think this is true - you can find plenty of people who were at school 40 years ago who need their fingers to do sums, and you can find plenty of young people who are adept at maths and science today.

For our part, we do not presume our players are stupid. We just presume they want sci-fi action rather than maths problems. And we don't judge them for that.

Thank you for that, Mr. Sprange. Nice to see a game publisher who gets it.

40 years ago, I was solving complex polynomials in my head out of boredom. Today, I need to do some sums on my fingers. It's called "getting old" and practically everyone is going to get there eventually whether they like it or not if they live long enough (there's always exceptions to the loss of mental acuity, thank goodness). And yet I can still play Traveller with anyone between the ages of 8 and 80 and have a rollicking good time doing it.

MongTrav is just fine.