"Emergency Agility" is basically turning weapons
and screens off.
![Backhand index pointing left :point_left: 👈](https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f448.png)
It's the normal mode outside combat.
LBB5.80, p39:
Emergency Agility: A ship may be declared to be using its emergency agility during the pre-combat decision step. If so, the ship may not fire any of its energy consuming weapons (all but missiles and sandcasters), but its agility becomes equal to its maneuver drive or its power plant number, whichever is less.
The ship may still use its computers and screens. This tactic is especially useful when breaking off by acceleration.
See, here's the thing. If I have a power plant 6 and a maneuver drive 6 and no other power-using systems, then I have agility 6: all that power is going to my maneuver drive. If I slap on lasers and energy weapons and such and divert all that power to them, then I no longer have excess energy for my maneuver drive and now have agility 0.
Here's where the problem starts: if my maneuver drive is still delivering 6g acceleration, then I am creating energy from nothing. The acceleration of my craft, even in a straight line, represents an increase in kinetic energy - energy that came to me free. My power plant isn't producing it; all my power plant's energy is going to weapons.
Here is what is ACTUALLY happening.
Power Plant code must at all times exceed Maneuver code.
You are not allowed to design a Power Plant-3 for a Maneuver-4 drive, for example.
WHY?
Answer, because you need a Power Plant of an equal or higher code number to the Maneuver drive for the Maneuver drive to deliver its full acceleration in Gs ... whatever that number is (1-6).
But then what's the deal with EPs and Agility?
How can a craft with Maneuver-1+ and Agility=0 ... accelerate at all?
Power Plants produce enough energy to power Maneuver drives up to their code number BASELINE.
A Power Plant-4 will ALWAYS under all circumstances deliver sufficient power to a Maneuver-4 drive to produce 4G acceleration under all conditions, regardless of circumstances (until the power plant is damaged or runs out of fuel, of course).
But what about EPs and Agility?
Maneuver and Agility refer to different things.
That's like trying to say that acceleration, velocity and speed are all the same things ... when THEY ARE NOT.
A Power Plant-4 will ALWAYS under all circumstances deliver sufficient power to a Maneuver-4 drive to produce 4G acceleration under all conditions, regardless of circumstances (until the power plant is damaged or runs out of fuel, of course).
The ability of the maneuver drive to produce acceleration (at all) is "baked in" to the power plant minimum requirement.
Then what are EPs?
And what is Agility?
EPs are the ADDITIONAL ENERGY the power plant produces for all other energy consuming purposes AFTER meeting the minimum requirement needed for the full acceleration output of the maneuver drive. That extra energy can be allocated to weapons, screens, computers ... and/or agility.
Maneuver is the ability to "GO FAST" in a straight line.
Agility is the ability to "TURN FAST" to alter course away from straight line movement.
I would hope that everyone reading these forums has enough Geek Cred™ to recognize this quote:
Or I could use this historical example of a craft that flies REALLY FAST, but can't TURN to dogfight ...
So what does this mean in Traveller space combat terms then?
A starship like a
Gazelle-class close escort with its Power Plant-5, Maneuver-5 and Agility-0 can maneuver at 5G in a straight line, but it can't TURN worth spit with its weapon systems active. Power down the weapons and pour all the EPs the power plant can produce into the computer and maneuver AGILITY and the starship can TURN with an Agility-5, but it can't attack anything while doing so.
Maneuver = Go Fast
Agility = Turn Quick
If you can go really fast, but can't turn ... a more nimble opponent (who has higher agility) can take advantage of your inability to follow highly agile movements and escape. They turn around while you can't. They go a different direction while you can't. They escape because you can't match their course changes. You go REALLY FAST in the wrong direction and can't recover quickly enough to re-engage.
This is why Agility is the important factor for an evasive plan of action such as Breaking Off By Acceleration. The craft with "better agility" are able to "shake" their pursuers by turning away when the pursuit can't. Higher agility "defeats" lower agility, even if the lower agility can achieve better acceleration. That's because the higher agility is "more responsive" to changes in vector, while the lower agility is "sluggish to turn" and change vectors.
If the pursuit is in a straight line (like a race to a goal) then agility is NOT A FACTOR and the superior acceleration will win.
If a pursuit relies on agility to "shake" a pursuer, then agility is the DECIDING FACTOR because the higher agility craft can move in ways that force a lower agility but higher acceleration pursuer to "waste" a lot of their acceleration by not being able to follow the "chop and change" course changes of the higher agility craft ... putting the lower agility craft at a disadvantage that cannot keep up with and remain in contact with the higher agility craft. Hence, higher agility "wins" Breaking Off By Acceleration contests.
Power plants produce enough power to provide full acceleration (in a straight line) from associated maneuver drives.
Power plants ALSO produce additional energy IN EXCESS of this minimum needed for full maneuver drive acceleration IN A STRAIGHT LINE.
However, TURNING to change course headings in a combat meaningful way requires ADDITIONAL power to the maneuver drive than the default minimum ... and this additional power is where the EPs allocated to maneuver drives for the purpose of agility (not acceleration, per se) come into play.
A power plant that has NO ADDITIONAL POWER DEMANDS other than exclusively the maneuver drive will produce an agility rating that matches the acceleration Gs of that drive.
Power Plant-4, Maneuver-4 ... no other EP consuming systems (weapons, screens, computers) ... will also have Agility-4.
It's when you start adding on additional power consuming weapons, screens and computers that this reserve of "extra power" starts getting diverted away from the maneuver drive, reducing agility (unless if you increase the size and power output of the power plant). Acceleration in a straight line remains the same, but combat agility/the ability to turn (on a dime) suffers. The craft becomes less and less responsive to pilot commands for vector changes. You can still power "forwards" at full Gs of acceleration, but as agility goes down, the power available to turn and change course, to fly in different directions goes down.
If you only want to accelerate in
1 direction (forward) then agility is superfluous.
If you want to acceleration in ANY direction, not just 1 ... then agility is paramount.
Maneuver = Go Fast(er)
Agility = Turn Quick(er)
Confuse these basic concepts at your own peril.