Thursday, April 15, 2021

Robots as Spaceships: Walkers and Power Armor

So what is the difference between a combat walker and power armor? They seem to be a simple continuum starting with simple armor that strengthens the user and ending with giant mecha. Its not that simple though, and the more I've worked on making power armor and walkers work in Robots as Spaceships, the more distinct the two things become.

  • Power armor is worn, Walkers are piloted. 
  •  Power Armor only needs to bear its own weight and not get in its bearer's way. Walkers need to bear the weight of the pilot.
  • Power Armor must have its knees, elbows, shoulders, and hips in the same location as its wearer. Walkers can have these locations in the same places, but often do not.

Of course, art breaking that last rule is not exactly uncommon, but we can call that cinematic, and judge if it is a walker or power armor on a case by case basis.

How to Build a Walker

We actually have all the tools to build a walker that we need. Its a robot built as a spaceship, with cargo space for a pilot inside. For example, we could build a 1500 lbs chassis with 1 power cell, two legs, two arms, 1 control system, and ten armor systems. That leaves 300 lbs of "cargo space" to put the pilot and his seating (the padded interior from the Arms, Legs, and Mecha article weighs 20 lbs). That's simple enough, and gives us the following stats:

MoveDRHnd/StbLWt.LoadSMCost(cheap)(very cheap)
Generic Walker
4510150+4/+31500 lbs
280 lbs

You can of course use the spaceships system to make all sorts of changes to this basic build.

How to Build Power Armor

Power Armor only has to carry itself, making the wielder  carry themselves, and do the work of standing upright and moving their own legs. This lets them be smaller and lighter than walkers, and provide much more protection. 

Most power armor has the same basic stats:  1 power cell, two legs, two arms, 1 control system, and the remainder(14) in armor systems. We should not use the armor density rules from pyramid 3/34, because power armor is hollow, wrapped around its wearer. Some suits of power armor might need additional leg systems to run faster, or additional power systems to run for longer, but most of the time, 2/3rds of the suit will be armor. 

Which lets us do something awesome...

Gurps has a detailed and methodical system for making custom armor, and as power armor is very close to 1/3rd power system and 2/3rds armor, we can use the custom armor system in pyramid 3/96 (or 3/85 for lower tech armors) to make power armor, which is very flexible and very cool. After you build the armor with the right DR, add 50% more weight to the armor, and you have a suit of powered armor. Look up the strength based on its weight here

Basing the cost of the system on the additional weight is fine for most of the armors given in those pyramid articles. The "true" cost is $70 per pound of added weight with no leg or arm cost reductions. If using cheap legs reduce the cost by $25 per pound, or by $30 if using cinematically cheap legs. If using arm cost reductions, each 20% modifier to both arms changes the cost per pound by $6.

If you don't have that system, you can use the following approximation, based on spaceships. Based on the weight of a 150 lb armor system, 7.5 lbs of power armor will get you 3DR at TL9, 5DR at TL10, or 7DR at TL11. The cost of such armor per pound is its base cost * $1. These numbers assume you are using Awesome Future Armor for battlesuits.

I recommend not allowing power armor that weighs more than a single ton, but we can certainly go higher if we need to. 

EDIT: When building power armor this way, I came across some severe scaling problems for high weights. The new method I worked out is here.

Uneven Armoring

In an earlier post, we brought up "simple armor facing", which says to double DR for highly protected areas (like the front of a tank) while halving it in weak areas (like the bottom of a tank) as a quick and dirty simplification. 

This is quite extreme for body armor, but a similar pattern is present, just muted. Armors in Ultratech generally have limb armor at about 2/3's of  torso and head armor. To acheive this effect, give  the head and torso +15% armor, and the limbs -15% armor. We will call this "Standard Humanoid Armoring". 

The principle is quite flexible though, and in general, for humanoid shapes its both fairly equivalent in cost and weight and also good idea to reduce limb armor to raise helmet and torso armor on a one to one basis.

How Much Weight in the Cockpit? 

So how much weight do we need to set aside for a human in the cockpit of a walker? Well, we need to carry a human, and unless we have the luxury of making the cockpit for a specific human or for an organization with weight limits on its pilots, we probably want to fit most humans in the cockpit. We also want a little extra weight for them to back essentials with them: If we're building a military craft, we want cargo weight for the pilot to carry a backup weapon, some food, some survival gear, and maybe a few personal mementos. If its a civilian craft, we probably need to give even more wiggle room. 

So while we could build a walker with 150 lbs set aside for our mecha jockey, we probably shouldn't. 200 lbs is quite low, and 300 lbs should be considered typical for a small walker. 

Its also worth remembering what happens if we go over that weight limit. Vehicles in gurps don't count their payload against their encumbrance, which means we have a little room to go other the listed weight. Of course, doing so will slow the walker down, and things the walker is currently carrying on its outside (like weapons) count against that weight as well.

Rules to Remember

And now we can build walkers and power armor! In the game that started this project off, I wanted robots, power armor, and walkers to be comparable and use similar rules and numbers. I'm really happy to have worked out and shown this system. Go out and wear some cool power armor!

No comments:

Post a Comment