Wednesday, February 13, 2019

Robots as Spaceships: Arms, Legs, and Mecha

concept art by Pascal Blanche
One of the great staples of science fiction is the humanoid machine. These take many forms: mass produced battle droids, sinister machine infiltrators, humorous robot butlers and futuristic telepresence androids are all essentially machines shaped like a human.  Even power suits are ultimately human-shaped machines capable of moving under their own power. Including humanoid robots in our system is critical, not to mention quadrupeds, octopoids, and other organic shapes.  Spaceships will give us most of what we need, but we will need to extrapolate just a little, and make sure the system builds what we need it to.

Weight vs. Count

Spaceships is built with systems, each taking up 1/20th of the vehicles mass. When we add a system to spaceships, we are adding a set amount of mass. This is important to remember when adding leg or arm systems to a spaceship. A single leg system could represent a dozen small centipede like legs, or it could represent one half a a massive leg. While we can build any number of limbs from any number of limb systems, the mass spent does matter, and faster or more complex movement  requires more systems.
By Simon Liu


We can find the Robot Leg System in Spaceships 4, which includes Mecha. It gives us a simple method to calculate basic move and top speed. However, it firmly ties these statistics to a number of legs, and we're counting systems rather than limbs. We will use the same equations, but use the number of systems rather than the number of legs when determining speed. The number of legs is still important when determining handling and stability. A robot may be built with any number of legs, choosing the combination of handling and stability that seems best for that design.

One Leg+41
Two Legs+43
Three Legs+34
Four Legs +35
Additionalno effectno effect
Spaceships above SM+4 become unwieldy and difficult to balance, and their handling drops by 1 for every SM above 4. We will also apply the penalties for streamlining and winged shapes on Spaceships 4 page 37. GM's who wish for cinematically large mecha-style robots will wish to ignore all these penalties, allowing massive robots that move with the natural grace of an ancient warrior.

actual 2019 working robot arm!
Arms and Manipulators

Similarly to legs, we should not confuse the number of arms for the number of arm systems.  A robot could have 2 small manipulators that can't really reach very far, and they would be a single arm system. Conversely, it could have a single massive arm longer than the rest of its body, and that would occupy multiple arm systems.

Complex arms should be built using the extra arm advantage as a guideline, and using multiplicative modifiers (powers 102). Each Character Point weighs a 10th of a system (or 1/200th of the robot) and has a relative cost of 10. A weapon mount only costs 2 points, so it only weighs 20% of a system and has a relative cost of 20. An arm with the with the long modifier costs 20 points, and thus costs 2 systems of weight and has a relative cost of 200.

Futuristic Human-like arm
Most combat robots will either employ traditional arms, mimicking the motions of their pilots, or weapon mounts (which are 1/5th the weight of a system and cost 1/5th of a full arm). A few more will use turrets. Turrets are built as Extra Arm (short -50%, no physical attack -50%, extra flexible +50%)[5], which has a relative cost of 50 and a weight of half a system.

Most complicated arms will be found on robots that perform work of some kind. Modern examples include mars rovers, welding arms, hazmat robots, and some construction equipment. In the future, even more jobs may be performed by mechanical limbs. Two limitations are worth examining in this context:
(from The Incredibles)
No Fine Manipulators. Just because you have an arm doesn't mean you have a hand, and forgoing the complexities of full manipulation can be a great way to cut costs. Its much less effective at cutting weight. An arm with no manipulator weighs the same, but costs half as much. This includes arms with gear built into them, such as a welding rod, chainsaw, or firearm.
Weak: Mathematically speaking, an arm with half the ST score should weigh a quarter as much, not three quarters. We're going to use smaller systems rather than use the weak modifier. 

Power Armor Concept Art
Walkers and Battlesuits

Throughout this series we've inspected the difference between a vehicle piloted by a human and one piloted by a robot. In practice, the biggest difference is often that one has 150 lbs or more of meat inside. When we talked about chassis, we mentioned a basic padded interior weighing about 20 lbs. Padded interiors are perfect for battlesuits, which are "Worn" rather than "ridden", with the machinery wrapping around the form of the soldier. A sufficiently large walker could easily have a chair rather than holes for arms and legs to go in, but at that point its probably not a battlesuit anymore. To turn an android into a battlesuit or walker, we reserve cargo space for the pilot and add padding or a seat.The controls are included when we purchase the control system.


While most vehicles are driven or piloted using a specialized skill, battlesuits and some walkers are designed to be intuitive, and to harness the user's innate muscle memory and thousands of hours practice walking. At least they are in a lot of fiction. This probably requires either a direct neural interface, or dozens of small sensors all over the body. A GM could justify this as handled by the control room: what is it if not a bunch of sensors integrated with the control of the vehicle? On the other hand, just as valid to insist on more expensive control systems. If neural interfaces are uncommon in the general populace, the vehicle will be built with one included. If built in a society were neural interfaces are as common as modern cell phones, the machine is likely to only provide the software needed to connect to the neural interface and drive the machine.

A set of sensors should cost no more than $500 and have negligible weight, unless the GM wishes the sensors to be expensive prototypes. The sensors must be embedded into the walker, into suit and helmet to provide structure, or stuck directly to the skin. The suit could even be worn outside of the vehicle  and used to drive it remotely, or to control a robot that doesn't have space for a pilot.

If neither sensors nor a neural interface is available, the suit is probably operated by the mechanical means of wheels, levers, pedals, and so forth, and should use the driving (mecha) skill. Its also possible that software handles the details of balance and locomotion while the driver sets a direction and speed.

An AI essentially has a neural interface as part of its basic functionality. What it lacks is years of practice walking, running, and jumping. An AI should probably treat driving any walker as a skill, in this case driving (Mecha). An AI that spends large amounts of time may, at the GM's option, use its native DX instead.

mechanical shark by William Ye
Loose Ends

Some organic forms can't be replicated with only arms and legs. We will use the flexibody drivetrain in pyramid 3/34 if we need a robot to slither like an snake or swim like a shark.

This article only lightly touched on movement speeds, which vary by size. We will come back to add more detail, but the basic numbers from spaceships 4 are "Good Enough" for most purposes, and we will consider them at the same time we consider wheels, tracks, and other motive systems for robots smaller than spaceships gives statistics for.

With these tools, we can now build a lot more robots, and to use this system for combat walkers and battle-suits as well. Happy robot building!

No comments:

Post a Comment