Register Register

Author Topic: Radical Jump Jets  (Read 289 times)


  • Master Sergeant
  • *
  • Posts: 295
    • Powered by Indifference, Focused by Caffeine
Radical Jump Jets
« on: 08 October 2022, 10:15:34 »
Jump jets intake ambient gasses, heat them, and then expel them to propel battlemechs tens of meters across the battlefield. The radical jump jet system dramatically increases air intake, sometimes using intakes similar to jet engines, in the name of getting a more efficient reaction at higher masses.

It's a tweaked jump jet system which provides a fixed "thrust-per-ton," interacts positively with superchargers, and doesn't react well to inclement environments.

Radical Jump Jets (RJJs) provide 30 JumpMP-Tons per half-ton of RJJ (60 JumpMP-Tons per full RJJ ton). To determine the Jumping Movement Points of a 'mech with RJJ, multiply the tonnage of the RJJ system by 60, divide by the 'mech's tonnage and round down.

RJJs take up one critical space per ton or fraction of a ton they weigh. RJJ must be allocated to a torso location, but may be split between adjacent torso locations.

For ease of battlefield management, RJJ also have a class. Divide the 'mechs RJJ JMP by its RJJ Crits and round up. That's its RJJ class. Whenever a RJJ system receives a critical hit, it loses JMP equal to its class.

The C-Bill cost for a RJJ system is as much as a regular jump jet system times 2.

Example: An 80-ton Charger has 7 tons of Radical Jump Jets. Its Jumping MP is 5 (7 tons of RJJ * 60 / 80 = 42/8 = 5.25).

If a 'mech with RJJ also mounts a supercharger, it may activate its supercharger to use JMP up to its Running MP that turn (provided their RJJ can provide that much MP).

A 'mech with RJJ can have all of its JMP removed while still having the RJJ system functional. 'Mechs with a functional RJJ system and 0 JMP can still:
    Use JMP to move 1 hex into an adjacent hex with any lower elevation without taking fall damage.
    Use JMP to make a Death from Above attack against a unit in its own hex or in an adjacent hex with a lower elevation.

Because RJJ are tied so closely to the engine, when a 'mech uses JMP from RJJ, it gains 3 additional heat for each RJJ crit it has taken

Because of their massive air intakes, RJJ cannot be used in vacuum, trace, or thin atmosphere environments. Nor may they be modified to do so.

RJJ take in large amounts of air and do not respond well if they also take in particulates. If RJJ are used in an environment with Hail, Rain, Snow, or Blowing Sand; or in a hex that's a Bug Storm, Geyerser, or Fire hex, the player rolls a Determining Critical Hits roll with a -2 modifier. All critical hits are applied to the RJJ system.

Optional Rules
Radical Jump Jets interact with some of the optional rules from Tactical Operations.

Glancing Blows/Margin of Success - If a 'mech is hit by a glancing blow with a non-energy AP weapon in a turn it used RJJ, the player rolls a Determining Critical Hits roll with a -2 modifier (and without the modifier from Glancing Blows). All critical hits rolled this way are applied to the RJJ system. The light weapons used to harm infantry can be actively sucked into the intakes and damage the system.
Before firing at a unit that used RJJ movement this turn, an attacker may declare they are aiming for the jets. Any additional bonuses from Margins of Success are ignored and if the attack has a MOS of 3 or greater it may force the 'mech with RJJ to roll a Determining Critical Hits roll with a -2 modifier. All critical hits rolled this way are applied to the RJJ system. This roll is separate from any other checks for critical hits caused by the attack.

Fractional Accounting - If using fractional accounting, calculate the 'mech's RJJ tonnage with the following formula:
     Desired JMP * 'Mech Tonnage / 60

It struck me as odd but reasonable that there were no 1.5-ton jump jets. Also that half-ton jump jets could propel a 45 ton 'mech as efficiently as a 30 ton 'mech 2/3 its size.

Radical Jump Jets peak in efficiency at the 30, 60, and 90 ton mark and are worse than standard JJ for most purposes. I tried tweaking that magical 60 number, but a Grand Titan with a supercharger and 10 tons of RJJ already seemed...wrong?

There's also lighter 'mechs to consider. 3.0 tons would give a 20-ton 'mech 9 JMP. A supercharger for a 120 engine runs 0.5 tons. That's scary, but it requires a supercharger roll, so it's not every turn and no matter how careful you are, there's still a risk.
« Last Edit: 08 October 2022, 10:17:17 by VanVelding »
I also have a blog about gaming, comics, and news at vanvelding.blogspot.