Friday, July 19, 2013

200: Thermal Sword

ENTRY 200: Thermal Sword

“The tip of my sunblade seemed to just touch the faceplate—and then I drove it in. For a moment he stared into the sun, and in the next breath the white-hot tip had plunged through helmet and eye and bone, and the brain flash-boiled and exploded.”
– Ruster Graeme

There is a popular story told on Mars, about how a squad of exsurgent xenomorphs came down on a demolition site where the Barsoomians were cutting apart a dome that had fallen in on itself. The transhumans had only their tools to defend themselves with. The xenomorphs burned under the assault of a dozen thermal lances, and when the rods were exhausted what was left of them were broken into pieces by heavy hammers and wrenches. With all its variations, no one can say if the events of the story ever happened, but it is undoubtedly part of the reason thermal swords are so popular today—and perhaps it’s even true.

The progenitor of thermal swords and sunblades (also called “oxygen weapons”) is the thermal lance, a powerful and simple industrial cutting tool. An iron tube packed with iron rods; pressurized oxygen is fed through the assembly and the business end ignited. The result is a few minutes of molten magma being pumped out at around 3,000° C before the tube is consumed. Oxygen weapons work on an identical principle, with only a few refinements to the technology. The typical thermal sword is a shorter version of a thermal lance, with a specially-packed rod designed to burn hotter and a red-oxygen ignition at the end that can get the thermal sword burning in less than a second; the base contains the oxygen bottle and a heavily-insulated handle with flow-control knob and ignition switch. All of the parts can be manufactured by a maker, are relatively easy to assemble, and the plans are online—the red oxygen being by far the most expensive part of the whole weapon.

What a transhuman gets for their efforts is an easily disguisable melee weapon capable of melting or burning through most armor, and which can be wielded effectively using a few basic fencing maneuvers. However, the “blade” and oxygen supply lasts only for about a minute, and the igniter device is a one-shot; once lit the transhuman may have a burning sword of fiery vengeance, but unless they finish their business quickly will find themselves holding a handle with an empty oxygen bottle and the glowing stump of a weapon.

Sunblades are artisan-crafted thermal swords, made by Barsoomian fencing schools. Using higher-quality materials and better manufacturing techniques than random people with access to a maker and some duct tape, sunblades also have a better balance and are overall much better weapons in combat.


Armor Penetration (AP)
Damage Value (DV)
Average DV
Thermal Sword
2d10 + 2 + (SOM ÷ 10)
16 + (SOM ÷ 10)
2d10 + 4 + (SOM ÷ 10)
18 + (SOM ÷ 10)

Thermal swords and sunblades are wielded with the Blades skill. Any hit that is an Excellent Success (MoS 30+) sets the target on fire, where they will continue to take 2d10 damage per Action Turn provided the environment has oxygen available. Both weapons are one-shots; igniting them is a Quick Action, but they only last for one minute (20 Action Turns) and then the weapon is effectively destroyed. Gamemasters who don’t feel like handling this extra bit of bookkeeping are advised to rule that the oxygen weapon simply lasts until the end of the current combat. Oxygen weapons do work in vacuum, since they provide their own oxygen, but the gas and molten iron shooting out the business end will send the character flying unless they are carefully braced.


  1. Entry 200! Arbitrary magic number congratulations ;-) Can't believe we're nearer to the end than the beginning. This blog has been a great enrichment to my daily reading list! Keep up the good work, Bobby :-)