Query and speculation on maneuver drive

[Carlobrand]

I need a double-check on a question of interpretation.

MT Referee's Manual, P.87
"Agility: Space-faring craft also list the craft’s agility, which is used in starship combat. To compute the craft’s agility (drop fractions): Agility = Excess power output in megawatts - unloaded weight of craft in tons) x 5.4. Agility can never exceed 6. Excess power output is the power left over from the power plant after all other components have been powered."

(and then there's the odd comparison between Queen Mary and a rowboat.)

In High Guard (II), on which this system is clearly based, agility cannot exceed maneuver drive rating. In MegaTrav, I can't find any limiter to agility other than it can't exceed 6. Hypothetically, you could have a 1G craft with an agility of 6. Is this an accurate interpretation, or is this errata? Imperial Encyclopedia presents us with craft with low G drives and high agility, including the launch (1G, agility 6), slow boat (3G, agility 6), slow pinnace (2G, agility 6),free trader (1G, agility 2), and safari ship (1G, agility 2), but IE designs are errata-prone.

Now, speculation:
Observation: spaceship maneuver drive does not seem to care what your mass is: acceleration using maneuver drive (thrusters or grav) or is calculated by volume, not mass. In addition, spaceship drive in-atmosphere is based on the drive rating, not the drive rating minus the local gravity: MT Referee's Manual, p86, "Compute the speed values as shown for grav vehicles. Use the spacecraft’s maneuver drive thrust in Gs directly as the maneuver thrust - skip the maneuver thrust computation."

Observation: Starship Operator's Manual presents us with a system that thrusts out the backside, with slightly less thrust available to sides and much less forward. However, in such a system, agility would be based on the ability to turn the ship quickly to line up its drive with the new desired vector, and there would be no need for extra power: a ship with a powered 6G drive would be faster than a ship with a powered 1G drive even if the 1G drive had extra power available. The amount of power needed to pivot even a massive ship on its axis quickly is small compared to the thrust outputs being applied over a 20-minute turn. Inertial forces could play a limiting role, limiting how fast you can turn a ship without subjecting the extremities to more than 6G centripetal acceleration, but even there the times involved are quite short compared to the turn length. A 6G ship SHOULD be more agile than a 1G ship, even without added power.

However, spaceship agility IS calculated by mass, with extra power needed even though power is already allocated to the drive system.

Hypothesis: Starship Operator's Manual is incorrect. The spaceship's maneuver drive is an inertialess drive system that neither cares how much the ship masses nor what external forces are influencing the mass or what direction the ship is facing, because the drive influences the ship itself on an atomic level to provide motion. In effect, the drive "transcribes" a vector directly onto each atom of the ship. Or perhaps the drive influences space itself. (My physics is weak, but it does not appear to violate conservation because it is only successful in applying at best 7% of the energy used to motion, the rest going gods-know-where) At any rate, the drive can alter magnitude and direction over the long scale, taking about 20 minutes to apply a "turn" or "braking thrust". However, the drive is resistant to the kind of rapid change in direction that could mislead a targeting system: extra power must be applied in order to achieve a rapid change in direction or magnitude. In essence, the maneuver drive in space lumbers like the Queen Mary in an ocean, resisting sudden changes in both magnitude and vector unless extra energy is applied to achieve them, and the greater the mass, the greater the resistance.

The advantage of acceleration without expending reaction mass is therefore gained at a steep price in agility.

(In this model, the inertial damper system functions to "lock" every atom in the affected area into precisely the same frame, preventing slight variations in the drive's "transcription" from being translated into, say, the sudden collision of a passenger with a bulkhead.)

 

[McPerth]

Now, speculation:
Observation: spaceship maneuver drive does not seem to care what your mass is: acceleration using maneuver drive (thrusters or grav) or is calculated by volume, not mass. In addition, spaceship drive in-atmosphere is based on the drive rating, not the drive rating minus the local gravity: MT Referee's Manual, p86, "Compute the speed values as shown for grav vehicles. Use the spacecraft’s maneuver drive thrust in Gs directly as the maneuver thrust - skip the maneuver thrust computation."

My take on it (absolutely non-canon explanation thought to allow me to swallow it): mass is not a factor on acceleration at those levels (only for 20+ dton use maneuver drives) because maneuvre drives thrust (gravitic) is also based on the own (negligible at most levels) ship's gravity field, that also increases with the mass, so increasing drives efficiency by the same magnitude that the increased mass would lower the acceleration.

Observation: Starship Operator's Manual presents us with a system that thrusts out the backside, with slightly less thrust available to sides and much less forward. However, in such a system, agility would be based on the ability to turn the ship quickly to line up its drive with the new desired vector, and there would be no need for extra power: a ship with a powered 6G drive would be faster than a ship with a powered 1G drive even if the 1G drive had extra power available. The amount of power needed to pivot even a massive ship on its axis quickly is small compared to the thrust outputs being applied over a 20-minute turn. Inertial forces could play a limiting role, limiting how fast you can turn a ship without subjecting the extremities to more than 6G centripetal acceleration, but even there the times involved are quite short compared to the turn length. A 6G ship SHOULD be more agile than a 1G ship, even without added power.

However, spaceship agility IS calculated by mass, with extra power needed even though power is already allocated to the drive system.

Hypothesis: Starship Operator's Manual is incorrect. The spaceship's maneuver drive is an inertialess drive system that neither cares how much the ship masses nor what external forces are influencing the mass or what direction the ship is facing, because the drive influences the ship itself on an atomic level to provide motion. In effect, the drive "transcribes" a vector directly onto each atom of the ship. Or perhaps the drive influences space itself. (My physics is weak, but it does not appear to violate conservation because it is only successful in applying at best 7% of the energy used to motion, the rest going gods-know-where) At any rate, the drive can alter magnitude and direction over the long scale, taking about 20 minutes to apply a "turn" or "braking thrust". However, the drive is resistant to the kind of rapid change in direction that could mislead a targeting system: extra power must be applied in order to achieve a rapid change in direction or magnitude. In essence, the maneuver drive in space lumbers like the Queen Mary in an ocean, resisting sudden changes in both magnitude and vector unless extra energy is applied to achieve them, and the greater the mass, the greater the resistance.

I have not my SOM Handy, but, IIRC, it also talked about agility being regulated by fast spining, high density disks in the center of mass of the ship, that were stopped to turn it in the desired direction. As I understood it, making those disks spin was what required those vast amounts of power.

 

[whulorigan]

I have not my SOM Handy, but, IIRC, it also talked about agility being regulated by fast spining, high density disks in the center of mass of the ship, that were stopped to turn it in the desired direction. As I understood it, making those disks spin was what required those vast amounts of power.

I do not have SOM in front of me either, but you are correct. The primary attitude control of the ship is a superdense sphere of material (at least, I think it was a sphere) at the Center-of-mass of the ship, surrounded by gravitic plates. As the superdense core spins, the gravitic-system varies the g-field along preferential directions to cause a gyroscopic effect to alter the ships attitude, so that the entire ship spins about whatever axis is desired. *


* - As an aside, note that SOM also says that every hull has a chemical/gas-powered emergency back-up reaction control thruster system installed by default, free of charge.

 

[mike wightman]

My explanation is the DGP folks didn't understand agility in HG2 and what it represents.

In HG2 if your power plant is equal to your m- drive you get an agility = m-drive. But because screens, computers and weapons use power plant out put you have to build a bigger power plant if you don't want to rob your maneuver drive of performance.

Put another way agility = (EPs available to maneuver drive from a same rating power plant) = effective maneuver drive rating.

The folks at DGP have misread this. They think that agility is energy left over after powering weapons, screens, computer and m- drive., which is not the case in HG2.

Now if you correct this you can start to use loaded and unloaded mass calculations to calculate performance in MT

 

[whulorigan]

Put another way agility = (EPs available to maneuver drive from a same rating power plant) = effective maneuver drive rating.

Are you sure about this? In HG2 (p.28):

Agility: Energy points remaining after weapons, screens, and computers have been installed may be applied toward the ship's agility rating. Divide the remaining energy points by 0.01M; the result is the number of agility points the ship has. Drop all fractional points. Agility is the ability of a ship to make violent maneuvers and take evasive action while engaging hostile targets. A ship's agility rating may never exceed its maneuver drive rating.

​

By this formula, it is possible for ships in HG2 to have Agility=0, as some do in Supplement 9: Fighting Ships:

Gazelle Class Close Escort p.17
Lightning Class Frontier Cruiser, p. 31

​

If your statement above about effective Maneuver Drive rating is true, these ships would be effectively Maneuever-0.
How do you interpret an Agility-0 ship in this case?

(Or am I misreading your statement)?

EDIT: Note - I agree that your statement makes logical sense, but the HG2 formula seems to cause problems with it. Is it perhaps a "broken" component of HG2 that should be addressed as an Errata?

 

[Carlobrand]

...I have not my SOM Handy, but, IIRC, it also talked about agility being regulated by fast spining, high density disks in the center of mass of the ship, that were stopped to turn it in the desired direction. As I understood it, making those disks spin was what required those vast amounts of power.

I do not have SOM in front of me either, but you are correct. The primary attitude control of the ship is a superdense sphere of material (at least, I think it was a sphere) at the Center-of-mass of the ship, surrounded by gravitic plates. As the superdense core spins, the gravitic-system varies the g-field along preferential directions to cause a gyroscopic effect to alter the ships attitude, so that the entire ship spins about whatever axis is desired. *


* - As an aside, note that SOM also says that every hull has a chemical/gas-powered emergency back-up reaction control thruster system installed by default, free of charge.

I recall the entry, but it does not fit the math. It simply does not take the level of power being applied in MT to turn a ship by either method. My example scout for example needs about 320 megawatts to manage agility 2, which means she's using almost as much power to spin quickly on her axis as she's using to achieve 2G acceleration. I can power a city on what it takes to turn a ship about the size of a passenger jet.

My explanation is the DGP folks didn't understand agility in HG2 and what it represents.

In HG2 if your power plant is equal to your m- drive you get an agility = m-drive. But because screens, computers and weapons use power plant out put you have to build a bigger power plant if you don't want to rob your maneuver drive of performance.

Put another way agility = (EPs available to maneuver drive from a same rating power plant) = effective maneuver drive rating.

The folks at DGP have misread this. They think that agility is energy left over after powering weapons, screens, computer and m- drive., which is not the case in HG2.

Now if you correct this you can start to use loaded and unloaded mass calculations to calculate performance in MT

I was under the impression the Referee's Manual was a GDW work, not DGP. Unless there's something I don't know about the creation of the Referee's Manual, GDW's actually the one that created the extra-power-needed rule. The extra-power rule's pretty effective at keeping large ships from becoming dancing fortresses but, given the scale involved, it is difficult to rationalize in the quantities needed - thus my hypothesis.

Are you sure bout this? In HG2 (p.28):

Agility: Energy points remaining after weapons, screens, and computers have been installed may be applied toward the ship's agility rating. Divide the remaining energy points by 0.01M; the result is the number of agility points the ship has. Drop all fractional points. Agility is the ability of a ship to make violent maneuvers and take evasive action while engaging hostile targets. A ship's agility rating may never exceed its maneuver drive rating.

​

By this formula, it is possible for ships in HG2 to have Agility=0, as some do in Supplement 9: Fighting Ships:

Gazelle Class Close Escort p.17
Lightning Class Frontier Cruiser, p. 31

​

If your statement above about effective Maneuver Drive rating is true, these ships would be effectively Maneuever-0.
How do you interpret an Agility-0 ship in this case?

(Or am I misreading your statement)?

EDIT: Note - I agree that your statement makes logical sense, but the HG2 formula seems to cause problems with it. Is it perhaps a "broken" component of HG2 that should be addressed as an Errata?

HG's issue was that you could design a ship that could divert power from the drive to power weapons - which meant no power available for sudden maneuvers. A scout, for instance, could have agility 2 or it could carry two lasers and have agility 0. Why that power had to be available to the lasers for the full 20 minutes is beyond me, but that's the way they did it. Makes about as much sense as that MT extra power rule, but it would be difficult to change without changing the fundamental character of the game.

Meanwhile, MegaTrav decided that everything needed to be powered all the time, which means you have power available for the drive but no explanation for why that power's not being used to wiggle and evade. You can change your vector on the map, but you can't use your available drive power to evade - you need extra power funneled through an agility-calculation rule. It helps avoid the dancing-fortress thing, but it's clearly a contrivance rather than an emulation. The challenge is to come up with some rationalization that doesn't leave it feeling like you're playing some abstract game where bishops are confined to diagonals because the rules say they are.

 

[whulorigan]

I recall the entry, but it does not fit the math. It simply does not take the level of power being applied in MT to turn a ship by either method. My example scout for example needs about 320 megawatts to manage agility 2, which means she's using almost as much power to spin quickly on her axis as she's using to achieve 2G acceleration. I can power a city on what it takes to turn a ship about the size of a passenger jet.

Yes, I understand and agree. I have been looking at your post for the last half-hour trying to think a way around this, but you are correct.

The extra-power rule's pretty effective at keeping large ships from becoming dancing fortresses but, given the scale involved, it is difficult to rationalize in the quantities needed - thus my hypothesis.
.
.
.

Meanwhile, MegaTrav decided that everything needed to be powered all the time, which means you have power available for the drive but no explanation for why that power's not being used to wiggle and evade. You can change your vector on the map, but you can't use your available drive power to evade - you need extra power funneled through an agility-calculation rule. It helps avoid the dancing-fortress thing, but it's clearly a contrivance rather than an emulation. The challenge is to come up with some rationalization that doesn't leave it feeling like you're playing some abstract game where bishops are confined to diagonals because the rules say they are.

Could it have something to do with Moment of Inertia/Centrifugal Force regarding the Inertial Compensation System?

The larger the physical dimensions of an object, the greater the "Centrifugal Force" that will be experienced at the end point of the moment-arm (that's the radial distance from the axis of rotation to the far end of the object). The larger it is, the more taxed a grav-based inertial compensation system will be, trying to compensate for the rotation so that people at the very back and very front of the ship will not be "crushed" against the outer wall during a rotation. (Think of the traditional "rotating-wheel" type space station - the larger the radius of rotation, the greater the effective gravity to the occupants of the wheel-habitat for a given rotational rate).

A small ship would not have that great of a moment arm, and thus not that great of a centrifugal force to compensate for. A large vessel would have a significant centrifugal force to compensate at its endpoints. (And this is in addition to powering the M-Drive and the attitude control system).

Therefore, you either put in a bigger power-plant to power more powerful compensators, or you rotate more slowly so that the compensators do not get overtaxed.

Of course, if this is the case, then agility ought to be based on displacement or configuration, not mass.

 

[McPerth]

In general, all power needs for MT are absurdously high.

To power an appartment (3-4 staterooms, so about 162-216 kl), the life support (just basic life support, that ammounts to heat and lights) power needs are about 0.162-0.216 MW (that's 162-216 kW). The power I have contracted at home is just 4.4 kW...

IIRC, in a Q&A, Mr Furgate told that they assumed chap power will bring that, using as a paralelism the cheap memory in computers that raised memory needs for everything, but does not take into account that lower TL needs are kept the same.

 

[mike wightman]

Are you sure about this? In HG2 (p.28):

Agility: Energy points remaining after weapons, screens, and computers have been installed may be applied toward the ship's agility rating. Divide the remaining energy points by 0.01M; the result is the number of agility points the ship has. Drop all fractional points. Agility is the ability of a ship to make violent maneuvers and take evasive action while engaging hostile targets. A ship's agility rating may never exceed its maneuver drive rating.​

Take a 1000t ship with a pp6 and md 6.

How many EPs is it's pp generating? EP = 0.01MPn, that's 60EPs

How much agility do you get for 60EPs?

60/0.01M = 6

Trouble is you will lose agility to power weapons, screens and computer.

By this formula, it is possible for ships in HG2 to have Agility=0, as some do in Supplement 9: Fighting Ships:

Gazelle Class Close Escort p.17
Lightning Class Frontier Cruiser, p. 31​

That's because they are pre-HG2 designs and not very well translate to HG2.
The Gazelle and the AHL are unerpowered.

If your statement above about effective Maneuver Drive rating is true, these ships would be effectively Maneuever-0.
How do you interpret an Agility-0 ship in this case?

Agility is movement in HG2 combat, energy to manoeuvre is agility, if your agility is low you lose initiative to a more agile fleet. Read the rules on emergency agility - diverting all power to the engines.

 

[mike wightman]

In general, all power needs for MT are absurdously high.

To power an appartment (3-4 staterooms, so about 162-216 kl), the life support (just basic life support, that ammounts to heat and lights) power needs are about 0.162-0.216 MW (that's 162-216 kW). The power I have contracted at home is just 4.4 kW...

IIRC, in a Q&A, Mr Furgate told that they assumed chap power will bring that, using as a paralelism the cheap memory in computers that raised memory needs for everything, but does not take into account that lower TL needs are kept the same.

Or the need to remove all the waste heat that 216kW will degrade to...

 

[McPerth]

Or the need to remove all the waste heat that 216kW will degrade to...

It seems that the heat included in the basic life support means cooking all the inhabitants :devil:.

 

[mike wightman]

I was under the impression the Referee's Manual was a GDW work, not DGP. Unless there's something I don't know about the creation of the Referee's Manual, GDW's actually the one that created the extra-power-needed rule. The extra-power rule's pretty effective at keeping large ships from becoming dancing fortresses but, given the scale involved, it is difficult to rationalize in the quantities needed - thus my hypothesis.

MT was developed and written by DGP up until Hard Times when GDW took it back in house. It was published by GDW.

The DGP design team tried to do the impossible - reconcile Striker vehicle design with starship construction. They based their power generation on Striker numbers. When they realised the fuel requirements of Striker power plants wouldn't fit starship parameters they lowered jump fuel required as a fix.

There are lots of problems with MT ship construction as a result of this.

Note standard designs become TL15 across the board, because lower tech power plants become too big and fuel hungry to build the classic designs at a lower TL.

I think the MT agility rule shows they didn't understand HG2 very well, and the jump drive fuel rules (all fuel consumed by the jump regardless of jump distance) were still based on '77 CT rather than the revised rules from HG, HG2, '81CT.

HG's issue was that you could design a ship that could divert power from the drive to power weapons - which meant no power available for sudden maneuvers. A scout, for instance, could have agility 2 or it could carry two lasers and have agility 0. Why that power had to be available to the lasers for the full 20 minutes is beyond me, but that's the way they did it. Makes about as much sense as that MT extra power rule, but it would be difficult to change without changing the fundamental character of the game.

HG1 didn't use EPs, your pp had to be equal in size to your j or md whichever is higher.
MgT has re-adopted this system but also put a minimum power plant size for various weapons too.
HG2 requires you to build power plants larger than your m-drive if you want high agility.

Meanwhile, MegaTrav decided that everything needed to be powered all the time, which means you have power available for the drive but no explanation for why that power's not being used to wiggle and evade. You can change your vector on the map, but you can't use your available drive power to evade - you need extra power funneled through an agility-calculation rule. It helps avoid the dancing-fortress thing, but it's clearly a contrivance rather than an emulation. The challenge is to come up with some rationalization that doesn't leave it feeling like you're playing some abstract game where bishops are confined to diagonals because the rules say they are.

I don't think this can be rationalised. I think they just got agility wrong in MT.

 

[mike wightman]

It seems that the heat included in the basic life support means cooking all the inhabitants :devil:.

You owe me one keyboard :rofl:

 

[Carlobrand]

It seems that the heat included in the basic life support means cooking all the inhabitants :devil:.

I'm sure there's a very good reason for that. Yes, a very good reason. A very, very, very good reason.

I just can't even begin to guess what it could possibly be.

MT was developed and written by DGP up until Hard Times when GDW took it back in house. It was published by GDW. ...

That actually explains quite a lot.

... Note standard designs become TL15 across the board, because lower tech power plants become too big and fuel hungry to build the classic designs at a lower TL. ...

That's true of High Guard II as well. The systems were just close enough that we could grandfather the classic ships in as long as we held our noses and didn't look too closely.

... I don't think this can be rationalised. I think they just got agility wrong in MT. ...

I actually agree. They had a mission: to fix some of the problems with High Guard and give us a space combat system that produced something more like what we see in the canon milieu. They - had some odd results.

The changes birthed a 20dT model/9-equipped fighter that devastates anything with less than 88 ranks of armor; the only real defense is to be small and agile or big and heavily armored, or they mosquito-bite you into impotence in short order. Meanwhile, spinal mesons still pretty much eat up whatever they hit, though the crew survival rate's a bit better, so big is still a bad thing. The result, as near as I can figure, is a universe dominated by fighters and carriers, SDBs in the 1500 dT range, and small meson-spinal battleriders and their tenders.

However, as I have said regarding other such errors, it is what it is. Unless the powers-that-be decide to embark on a really ambitious errata program, we're still left with either IMTUing it or coming up with some artful tapdance to rationalize the more nonsensical elements.

 

[mike wightman]

I just opted to fix HG2 myself and borrow all the higher tech weapons, screens, armour etc from MT - it ports to HG2 easy enough.

 

[Carlobrand]

I just opted to fix HG2 myself and borrow all the higher tech weapons, screens, armour etc from MT - it ports to HG2 easy enough.

What did you do about the computers?

 

[HG_B]

What did you do about the computers?

Purchased stock in a vacuum tube company? :rofl:

 

[rancke]

Interpreting the volumes to include workstations and access space helps a bit.


Hans

 

[Carlobrand]

I was thinking more about their power consumption.

 

[HG_B]

Interpreting the volumes to include workstations and access space helps a bit.


Hans

Not nearly enough as you STILL have allocate separate tonnage for crew work space and even adding the human interface, you are several orders of magnitude over size wise. Much simpler to do what MgT did.