Agility - thoughts

[Spinward Flow]

Agility in airplane terms derive from how readily they can use control surfaces to turn, lift etc. while using the least energy doing so.

Agility in spacecraft terms derive from how readily they can use gravitics/reaction control thrusters to spin on different axes of rotation, etc. in the most time efficient/responsive manner for doing so.

The engineering/means is different ... but the purpose/intent is analogous in a broadly similar way.

Kind of like how submarines are "lighter than water craft" in the same way that dirigibles and balloons are "lighter than air craft" in terms of the physics involved. Different medium (ocean vs atmosphere), but how the two vehicles "work" is analogous in a broadly similar way.

 

[kilemall]

Agility in spacecraft terms derive from how readily they can use gravitics/reaction control thrusters to spin on different axes of rotation, etc. in the most time efficient/responsive manner for doing so.

The engineering/means is different ... but the purpose/intent is analogous in a broadly similar way.

Kind of like how submarines are "lighter than water craft" in the same way that dirigibles and balloons are "lighter than air craft" in terms of the physics involved. Different medium (ocean vs atmosphere), but how the two vehicles "work" is analogous in a broadly similar way.

I don’t think so at all, again when breaking off, what attitude your ship is at isn’t the issue, range is. Certainly the evasion altering axis type maneuvers would be central to generating misses which is part of the negative hit DM, but doesn’t get you out of range of the enemy.

 

[AnotherDilbert]

I don't use any agility rules for making a ship harder to hit. They make no sense. Example: Lets say "agility" of 1 gave you a tenth more G for the maneuver.

It doesn't. Agility-0 is 0 G, Agility-1 is 1 G acceleration.

TCS, p12:
AGILITY
Agility is a measure of the amount of energy available to the ship's maneuver drives, even when other operations are in progress.

 

[AnotherDilbert]

Orbital velocities are typically high enough that acceleration is just a tiny fraction of the current velocity.
Earth orbital velocity around the Sun is over 100,000 kph (30 km/s) … so how much will a 6G (60 m/s) acceleration really change current velocity in your orbit around the sun? It is off-orbit acceleration to increase eccentricity that will give you range between the fleets as you travel that fast. That is “breaking off”.

Yes, but irrelevant.

How large is the uncertainty in your estimation of the enemy's position?
The 30 km/s is presumably well measured, with very low uncertainty.
The added velocity in the last few seconds (current acceleration) is unmeasurable, and adds directly to the uncertainty.

You only get a sensor blip, with the enemy ship somewhere in a sphere of uncertainty.

 

[AnotherDilbert]

Agility in spacecraft terms derive from how readily they can use gravitics/reaction control thrusters to spin on different axes of rotation, etc. in the most time efficient/responsive manner for doing so.

TSC, p12:
AGILITY
Agility is a measure of the amount of energy available to the ship's maneuver drives, even when other operations are in progress.

It's a choice: send power to the weapons, or send power to the M-drive.

 

[Condottiere]

How tight is your turning radius.

 

[TamsinP]

Yes, but irrelevant.

How large is the uncertainty in your estimation of the enemy's position?
The 30 km/s is presumably well measured, with very low uncertainty.
The added velocity in the last few seconds (current acceleration) is unmeasurable, and adds directly to the uncertainty.

You only get a sensor blip, with the enemy ship somewhere in a sphere of uncertainty.

It all depends on the frequency of active sensor scans (I assume that RADAR/LIDAR is part of the weapon's fire control system). Even if the frequency is 1/second, at the engagement ranges we are talking about in Traveller, the maximum vector change it could have made by acceleration between the sensor contact and weapons hitting it would be less than the size of most ships (for light speed weapons like lasers).

 

[mike wightman]

How tight is your turning radius.

Rotation around your centre of mass or vector turning circle?

 

[AnotherDilbert]

It all depends on the frequency of active sensor scans (I assume that RADAR/LIDAR is part of the weapon's fire control system). Even if the frequency is 1/second, at the engagement ranges we are talking about in Traveller, the maximum vector change it could have made by acceleration between the sensor contact and weapons hitting it would be less than the size of most ships (for light speed weapons like lasers).

At 1 ls ≈ 300 000 km the delay between radiation bouncing off the target until you read it is 1 s. The delay until a laser beam reaches the target is another 1 s. Assuming no humans in the fire control loop, but some computer time and laying the mount accurately of another 1 s, there is a 3 s gap between sensor information and incoming fire.

In 3 s a ship accelerating at 6 G ≈ 60 m/s² can move d = at²/2 = 270 m.

So, as you fire, you have to expect that the target will be a few hundred metres from where you think it will be. Fire a pattern (like depth charges), and hope for the best.

 

[atpollard]

You only get a sensor blip, with the enemy ship somewhere in a sphere of uncertainty.

I was only addressing the specific question of Agility for breaking off in response to the accusation of ships with "agility-0" being "immobile pillboxes". They have tremendous velocity [30,000 m/s] but no ability (agility) to change orbit while actively shooting, so they cannot "break off" from a co-orbital fleet.

 

[atpollard]

How tight is your turning radius.

My ship turns on a dime ... like Star Wars.
Not like the Hindenburg ... like Reality.

 

[AnotherDilbert]

I was only addressing the specific question of Agility for breaking off in response to the accusation of ships with "agility-0" being "immobile pillboxes". They have tremendous velocity [30,000 m/s] but no ability (agility) to change orbit while actively shooting, so they cannot "break off" from a co-orbital fleet.

Sorry, I misunderstood.

Yes, two fleet with roughly the same vector will remain close, regardless of local velocity.

You need acceleration to pull away.

 

[Spinward Flow]

How tight is your turning radius.

My ship turns on a dime ... like Star Wars.
Not like the Hindenburg ... like Reality.

A high agility small craft can rotate 180º in ~1 second, without modifying its course vector.

Here's what that looks like when using HEPlaR reaction thrusters instead of gravitics.

Any questions?

 

[kilemall]

Orbital velocities are typically high enough that acceleration is just a tiny fraction of the current velocity.
Earth orbital velocity around the Sun is over 100,000 kph (30 km/s) … so how much will a 6G (60 m/s) acceleration really change current velocity in your orbit around the sun? It is off-orbit acceleration to increase eccentricity that will give you range between the fleets as you travel that fast. That is “breaking off”.

Re orbital relative matching to world orbit, most battles should be seeing the planet move as a separate object, the fleets are either already matching course/vee to stay defending or setting course to intercept the planet. But they still have to push to close or get away.

If the battle is not around a planet it’s all about the fleets relative to each other. Either way, accel matters.

Doing actual LBB2 maneuvering, engagements are likely not going to last long anyway, more like making firing passes at each other until one declines to. The exception is fixed target battle for planets, that will either be high speed passes or slow vee grinding attrition.

 

[kilemall]

How tight is your turning radius.

This isn’t SFB or Starfire where wet naval maneuver is recreated. A 6G battleship has the same turning radius as a 6G fighter.

 

[atpollard]

A high agility small craft can rotate 180º in ~1 second, without modifying its course vector.

Here's what that looks like when using HEPlaR reaction thrusters instead of gravitics.

Any questions?

I agree, but that is not the typical definition of "turning radius". It is a change in vector, not merely facing. Those TIE Fighters had amazing [momentum negating] change of vector capability.

 

[Spinward Flow]

Those TIE Fighters had amazing change of vector capability.

Agreed ... but that was WWII dogfighting in space being shown, not Newtonian Physics combat in space being shown.

That's why Star Wars is a really BAD option for inspiration on how craft and fighters ought to maneuver in space.
Babylon 5 is MUCH better at depicting properly what Newtonian Physics maneuvering in zero gravity ought to look like.

 

[Condottiere]

Rotation around your centre of mass or vector turning circle?

1. All things being equal, actual time to turn around on your axis would depend on the length.

2. But I'm thinking vector, which should be the same despite size of ship, with the same agility.

 

[Tobias]

I don’t get the agility-2 aspect of that interpretation, at all.

The ship can accel if it has full power available to put to full capacity use of the mDrives. If the power plant only has enough left over for Agility-2 with everything powered, then Agility-2 is its accel.

If nothing else the escape rules make this explicit, higher agility means escape, even or lower means no escape, hence the emergency agility allocation override.

I may have phrased it badly, because that is exactly what I meant.
Agility = acceleration.

 

[Tobias]

Neither do I.
It means that CT canon ship classes such as the Gazelle and the Azhanti High Lightning cannot accelerate because their Agility=0 (too many EP's spent on computers, screens and weapons). It turns entire starship classes into pillboxes that don't move ... except by "emergency" agility measures.

Correct. They could only accelerate if they don't power their weapons.
Note that both the Gazelle and the AHL were designed using HG1 originally, in which "agility" did not exist as a separate metric. Same goes for Kinunir IIRC. Other ships with agility below m-drive rating are Book 2 designs.
All ships in supplement 9 which were actually designed under HG2 rules have agility ratings equal to their maneuver drive rating.

I think the simple, binary "agility or emergency agility" system was a bit of a missed opportunity, because allocating energy to different aspects (weapons, agility, screens) has the potential for interesting tactical choices in a game.