Sufficiently Advanced Technology 2
Plug and Play Power Sources
Removable, replaceable power sources for devices are fairly common in science fiction, ranging from ammunition that’s distinct to a given model of blaster to general-purpose batteries that work across dozens of different devices. In Barbarian Conquerors of Kanahu, and in a module that I’ll refrain from specifying to avoid spoilers, something close to the latter approach is used, with some items being entirely self-contained but those that do have replaceable power sources all using ‘energy crystals’. I’ll be using the word ‘battery’ to refer to the concept of a one-size-fits all charging consumable generally, and ‘energy crystals’ to refer to the prior examples. Many of the things said here don’t hold up as well when your las-gun runs on type A cells, your flight jacket on type B cells, and your matter relay runs on type C cells.
Battery Mechanical Constraints
If batteries only come in one size, but the objects they are used to power have effects of varying level, this needs to be accounted for. There’s two main options, with variations:
An effect always costs a full battery. This requires basing the price of a battery around the highest-level spell equivalent among the various items that take batteries, and results in less efficiency when powering weaker effects. I think this is not desirable, generally- no one will ever use a ray gun whose arrow-equivalent blasts could instead have powered an artillery piece- but it’s worth mentioning, and with a curated set of items/effects that are of roughly equivalent power it might work smoothly, rather than track exactly which items are 3rd, 4th, or 5th level. The difference in recharging difficulty, for purposes of pricing, can smooth this over a little: perhaps using a battery to power a 3rd level effect is priced as challenging, while using that same battery to power a 5th level effect is priced as easy, for example.
An effect can cost a partial battery, or multiple batteries. For example, a battery could be worth a a 2nd level effect, in which case it’d power a cantrip item for 10 uses but 3 batteries would be consumed for each use of a 6th level item. As a matter of implementation, this also requires deciding whether partially expended batteries exist, or whether the battery is drained entirely on the first use but the item itself holds the remainder of the energy. The former options has interesting implications, where weaker items can be easily operated off partial batteries but bigger items that empty one or more batteries at a time need full batteries. If batteries are often found with, say, 1d10x10% full capacity in partially loaded laser pistols then fueling a device that needs a whole battery, and can only physically accept one battery, requires a rare find of an untouched battery or somehow transferring energy from one battery to another.
One last consideration on the question of battery capacity is the physical dimensions of the batteries and the objects they power. If objects drain batteries and use the energy later, they can essentially be any size, but if they need to have one battery, or multiple batteries, attached or contained to be used, they need to be at least as big as the batteries- there’s no making a tech ring that uses batteries the size of a AA pencil battery.
Battery Prices and Rarity
The following section assumes a ‘kitchen-sink’ campaign, where tech items and their power sources might be found in any given treasure hoard, and are sold on the open market, with batteries possibly being created or refilled by alchemical means even if more complex devices remain inscrutable. If this isn’t the case, and all of a campaign’s tech items are found in a single large spaceship that the PCs have found, this section is less relevant, as it pertains to the process of integrating tech items and batteries into normal treasure tables and economies.
Objects are easier to buy and sell the cheaper they are, in systems like ACKS, so whether the typical battery is 100gp, 1,000gp, or 2,000gp matters a fair bit for how many can be bought, if they’re on the market. Counterbalancing this is the would-be rarer components having higher capacity. As an example, if these were just transacting as any other trade good, in a class II market one could buy 5 100gp, 2 500gp, 2 1,000gp, 1 2,000gp, 1 5,000gp, or 1 10,000gp batteries in a month, depending which was the standard. That’s 500, 1,000, 2,000, 2,000, 5,000, or 10,000gp available, respectively, depending on the size that a standard battery has. It’s different if batteries are bought and sold as magic items, and more complicated, as the volume of magic items traded per rarity/price bin is across all kinds of magic items, not per type, but has a similar pattern. A cantrip-equivalent tech item may recharge at 1 use per 100gp battery, if 100gp batteries are standard, or 10 uses per 1,000gp battery, if that’s the standard, and have a noticeably different sustainable rate of use, accordingly. The value of the default battery matters!
Even if not available as a typical trade good, and forming a small portion of the magic items available in market, if uncraftable, the base cost of batteries impacts how they can be placed on treasure tables. If batteries are 1,000gp or less, they’d be found on the Common tables; if 1,001-5,000gp, or found in groups with total value in that range, they’d be found on the Uncommon tables. On the former, batteries would mostly be displacing potions and scrolls, while on the latter they’d displace items of all kinds. But where do the items themselves fall?
Battery-Powered Tech Prices and Rarity
Now, what’s an item that takes batteries worth? Let’s consider a jacket which creates a localized antigravity field around the wearer for an hour, approximately the spell flight, a 3rd level effect (flight has a duration of 1 turn per level, but it’s the same cost). A potion or scroll of flight has a base cost of 1,500gp. What is the base cost of our jacket? if it’s single-use, the same 1,500gp. What if it’s rechargeable? If we call this a medium-difficulty recharge (2nd level, where an easy recharge would be 3rd level for a 3rd level spell and a hard recharge would be 1.5th level), then a single-charge rechargeable item is 2,000gp. These prices are very firmly Uncommon items; even an easy-recharge 6th level item would only be 4,500gp. If it’s desirable to have battery-fueled tech items in the Rare tables, the obvious answer is just to increase their capacity. If a full-capacity refuellable antigravity jacket functions for 12 hours, it has a base cost of 24,000gp. Charged effects can of course be combined with permanent and other effects- a high-tech sword could burn charges to become surrounded by an energy field that makes it cut even sharper, or armor have additional features, etc. Depending on the exact power and setting, I can see having charged tech items calculate their spell-equivalent charges used in total uptime, rather than per time the button is pressed, for things like forcefields, but it’s often simpler to just model such items using short-duration spells if that’s desired. Here’s an example charged item where the charges can be put to multiple uses:
Reentry Suit
Base Cost 30,000gp: Permanent (1/hour) 1st level effect 12,000gp; 6 charges choice of 6/2 = 3rd level esoteric effect (air supply), 3rd level effect (cold invulnerability), 3rd level effect (fire invulnerability), 3rd level effect (bludgeoning invulnerability), or recharge 3rd level effect = effective 6th level esoteric effect 18,000gp. Apparent Value: 200gp.
This 5” x 3”x 2” brick of blue-tinted metal has eight depressions on its top surface: one central ovoid depression, four circular depressions in a square above it; two wide, sequential depressions below it; and the last depression on the edge of the brick, beyond the sequential depressions. Drawing a finger across the centermost wide depression causes the bottom two-thirds of the brick to unfold into metal foil, a suit of the material open at the front and capable of covering a man-sized humanoid from head to toe, though the face is left exposed. drawing a finger across the second wide depression will draw the foil skintight with the brick held tight to the user’s left arm, if worn, or collapse it back into the brick, if empty. Wearable by any character under clothes, this undersuit provides a +2 bonus to AC which stacks with worn armor and any other enhancements to AC.
When worn, the central depression appears as glass, with five nested, segmented circles underneath, slightly glowing. The outer circle has eighteen segments, while the inner have ten segments each. 3d6 consecutive segments of the the outer circle will be illuminated, representing the charges the device contains. The depression at the brick’s edge is a catch, revealing a compartment into which a power cell can be inserted. When closed, the power cell will be drained, and one more charge displayed on the central depression.
The suit has four functions activated by touching a suit-gloved finger to a corresponding depression. Each function lasts for 1 turn, the remaining time of which is displayed in lit segments in the corresponding ring of the central depression. Invulnerability to cold, fire, or bludgeoning damage costs 3 of the device’s charges per damage type protected from; this protective field extends beyond the suit, affecting the wearer’s other equipment. For 6 charges, a skin-tight force field and pressurized air supply is generated, allowing the user to safely breathe underwater, when surrounded by poisonous gases, or even in environments that lack air entirely. Legends tell of men falling from the sky in such suits in far-flung locations, weapon in hand, though details vary heavily as to their armaments, purpose, and eventual fate.
For the purposes of this item, I am assuming 500gp ‘power cells’ that are the size of AAs, and that items can simply drain them, not needing to be physically big enough for 18 batteries to hold that many charges. At 6 charges (for item math purposes; 18 as counted on the device) the suit has enough juice to use each of its powers once, with one activation of a lesser power left over. The general idea here is to jump out of an airplane, or spaceship, with an enclosed air supply, the ability to not freeze to death in vacuum or burn up on reentry, and to not take damage on hitting the ground, without presenting an obvious airborne target by slowing down with a parachute. Typical adventurers may of course find some of these powers more useful than others, but everyone likes a good AC bonus.
Next installment, we’ll consider which effects are more suited to ‘scientific’ sources than magical ones, and vice versa.