Although some immigrants whose backgrounds involved reading cheesy fantasy novels or playing cheesier games have the notion that there are places in Nexus where "technologyTM doesn't work", that is not actually the case. Anywhere humans can live has, necessarily, natural laws, and it is the nature of sapience to exploit those natural laws. It is, alas for engineers, the nature of Nexus to have different natural laws in different zones, but similar zones, sort of by definition, have similar natural laws which means that applications of common principles are at least somewhat transferable between zones.
Most places where humans live have some sort of combustion, and typically the same sorts of substances burn. This means that firearms can be portable. However, because the details of combustion of a given substance vary from zone to zone, this portability is not as much as might be wished.
For game purposes, whenever the relative effectiveness of a given lot of ammo is in question, the GM should make an open quality roll. A high roll means the powder burns better than expected; a low roll means it burns more poorly. Within a limited range, the result of the roll is added directly to weapon damage. Towards the limits of the range (especially upward), the weapon will function with reduced reliability; outside the range, the weapon will probably fail to function, sometimes catastrophically. On a boxcars roll that ends up at -3 or less, the gunpowder in question is inert in that zone, and the weapon will just plain not work.
Single-shot guns or manual repeaters (including revolvers) will work with weak powder, down to the point (base damage less than 0) where the bullet won't make it out of the gun. Strong powder will reduce reliability and increase wear and tear, up to about +2. Beyond that, the increased pressure will probably badly damage or destroy the gun, possibly explosively.
(Semi)automatic weapons are pickier. They will operate normally only from -1 to +1, and then only at a substantial decrease in reliability. Below -2, the charge will be too weak to cycle the action, effectively converting the weapon to a clumsy manual repeater. At +2 or above, the action is likely to be damaged or destroyed by the overloading. Weapons with external slides (most semi-automatic pistols) will fail catastrophically at +2 or +3; ones with internal slides will be ruined, but won't explode until +3 or +4. Replacing the springs or equivalent can extend the range of functionality downward almost to 0 damage or upward to about +2, but generally requires field-stripping the weapon.
Experienced Nexus hands use guns that are overbuilt/underloaded, raising the amount of excess energy needed to destroy the weapon by about +1.
The foregoing might make firearms seem a poor choice for Nexus; even Chow Yun Fat would be hesitant to whip out his 9mm if there was a 1/12 chance he'd eat the slide. But dedicated and inventive gunwielders have found a way around this: the gunpowder gauge.
A gunpowder gauge is just a cylinder with a spring-loaded piston and a slide indicator. A known quantity of powder set off in the cylinder pushes the piston a distance against the spring proportional to the energy produced by the powder, and the user can read that amount off the scale.
For conventional fixed ammunition, the gauge reading is only a go/nogo decision for that type of ammo. However, a liquid propellent weapon can be adjusted to use more or less propellant to compensate for local conditions. It can even be made with an integral gauge, so that the throttle is automatically adjusted to local conditions at the push of a button (treat as an automatic or semiauto, but with the effective propellent energy adjustable by up to 2 in either direction). The downside is that LP guns are difficult to make and a pain to maintain, and the integral gauge mechanism is somewhat fragile. The sensible user will doublecheck the integral gauge with an independent one and override the setting manually as required.
Despite all these precautions, firearms are still more dangerous and less reliable than under a fixed set of laws: some interfaces are so subtle they give no warning that a powder check is necessary, and some zones have physics that change with time, place, or divine whim. Even when the interface is obvious and the reality stable, there might not be time to make a check, or the check might reveal only that none of the ammo handy is any good. Life is tough in Nexus.
Internal combustion engines aren't fundamentally much different than guns: fire, expanding gas, simple mechanical linkages. However, since they must operate continuously, they're somewhat more finicky. A fuel roll should be made like the gunpowder roll described above; from -1 to +1 an engine will continue to run, although not terribly well. -2 or +2 will require some adjustment of choke, timing, etc, but no major changes to the engine. Beyond that, the engine will not run at all reliably or well.
Engines built in or for Nexus (or for other environments where fuel type and quality are unknown ahead of time) can adjust choke, fuel flow, timing, and a variety of other parameters to work with a wide range of fuels; depending on the manufacture they can adjust the effective fuel quality by up to 3 points either way (although 1 or 2 is much more common). This adjustment takes some time and generally trial and error; there are enough parameters that an equivalent of the gunpowder gauge would be excessively complicated.
Gas turbines are a lot simpler: any turbine can run from -2 to +2, and Nexus-rated ones can handle as much as -4 to +4, mostly by adjusting the fuel flow alone.
Reciprocating engines usually burn more energetic fuel less efficiently, so overall consumption is the same, but turbines burn smaller amounts of more energetic fuel (and vice versa) so every 2 points of fuel quality halves or doubles consumption. The disadvantage, of course, is that gas turbines are, from a maintainance standpoint, complete money sinks.
External combustion (eg, steam) engines are much more flexible in principle: an ideal engine would be able to use fuel of quality down to maybe -5 before the temperature produced is too low to be useful, and up to +5 before the temperature is too high to be safe, although the details of a specific fuel system might be limiting.
One inobvious problem is that a thermostat cannot be counted on to produce the same reading for the same temperature in two different zones, so engines that try to automatically maintain a constant boiler temperature will fail. Mechanical pressure-based governors will usually work, though.
Recognizable electricity and magnetism (and electromagentism) are not as ubiquitous as combustion, but are more common than one might think. The principles of conductance, resistance, capacitance, and so on are reasonably portable, and often involve similar materials: simple electric circuits, including resistors, capacitors, relays, and vacuum tubes, as well as electric motors, can be expected to work in some fashion outside their native reality. Precise values will vary, though, necessitating adjustment in each new zone; Nexus-rated electrics generally have variable resistors and capacitors arranged to all be adjusted in synch with the turn of a knob.
Primitive radios and radar, analog telephones and televisions, electric motors and solenoids, and the like are therefore somewhat portable, although not nearly as much so as guns or cars. More sophisticated electronics that rely on subtle and strange properties such as semiconductivity, superconductivity, and nonlinear optics are rarely portable at all. In particular, microchip-based computers are right out (although you can do a lot with miniature vacuum tubes).
The rule of thumb is that the deeper an understanding required of a phenomenon, the less portable technology based on that phenomenon will be. Also, the more dependent the technology is on the precise values involved, the more adjustment it will require to be ported.
The important corollary to this is that defense (both literally and metaphorically) is easier than offense: native equipment will, except in the case of degenerate knowledge bases, always be superior to imported equipment.
This file was last modified at 1635 on 22Jun99 by email@example.com.