Steve Jackson Games GURPS – Generic Universal RolePlaying System

GURPS Lensman – Cover

Gadgeteering: Modifying and Inventing Devices


This section replaces the "new inventions" rules on pp. B186-187. Lensman characters frequently include elite mentalities, capable of exceeding the limits of available technology. The scientists, engineers and technicians of Civilization – and of Boskonia – often invent, design and construct new and fantastic devices that revolutionize the state of the art.

However, only inventions that the GM feels are appropriate can be created. Gadgets appropriate for a GURPS Supers game are not appropriate in a Lensman campaign, and the GM's word is final. No special advantage is required to use these rules – just high skills. Every gadget has specific areas of knowledge required to create it. The engineer will need to specialize in one or two areas. The GM will determine the complexity of the proposed device – see the Gadget Complexity sidebar for samples – and assign the prerequisite skills for each gadget.

Players who want to create a gadget must have an explanation for its operation, and must describe it to the GM in an impressive manner. The GM is free to accept or reject the design depending on its feasibility. If the item violates any laws of nature or would interfere with Mentor's plans, its research rolls will never succeed.

Impromptu Gadgeteering

Galactic Patrolmen are frequently in situations where they cannot rely on support forces being available. Accordingly, they are trained to improvise and adapt. They are quite capable of analyzing and modifying equipment during the course of a mission. Many of Civilization's greatest weapons – the primary beam and the hyper-spatial tube, as examples – were initially invented by Boskonians, and adapted by Civilization's scientists.

To modify someone else's gadget requires 1d hours, and two successful Mechanic (device type) rolls if an intact gadget is available. The GM will have to use his judgment to decide what modifications could reasonable be made in each particular case.


One common modification attempted on devices is overloading, trying to get more performance that it was designed to provide. The engineer altering the device should roll against whatever skill the GM decides is most appropriate. If the roll succeeds, the device's performance is improved by 10% per point he made his roll by. If he exactly made his roll, the device still works, but he made no improvement. However, overloaded devices have short life-spans. The GM will decide how long the altered device will last – it is quite possible that it will only work once! One method for randomizing the time of failure is to roll three dice. A roll less than the number of times the modified device has already been used causes it to quit.

If the engineer overloading the device failed his skill roll, the device whines, emits sparks, possibly shudders a little . . . and then quits completely, with vital components burned out and destroyed. If he critically failed, the device explodes.

A critical success results in starkly incredible performance. Roll one die – the device's capacity is multiplied by that number. On an unmodified roll of three, roll three dice.

Building New Gadgets

Characters can design and build their own gadgets. This lengthy process has several steps, but appropriate high skills can hasten it. When dividing by TS herein, use 0.1 for TS0.

Step 0: The Theory

No gadget can be built without a working understanding of its underlying principles. The initial idea may come in a single blinding flash, but the experimentation to confirm that idea takes much longer and can be expensive – very expensive if the idea is revolutionary.

Time Required: The idea behind a simple gadget takes 4d man-hours to confirm. Average complexity takes 6d man-hours, a complex gadget takes 6d × 15 man-hours, and an amazing gadget takes 6d × 50 man-hours. The work can be divided among several researchers, but each of them will understand the project most thoroughly – if secrecy is important, this is dangerous!

At the middle of the project, the engineers roll against their average skills the GM requires for the particular gadget. A failed roll adds 50% to the time to complete the gadget. On a critical failure the gadget is destroyed – all work is lost and the research cost (below) must be paid over again. A critical success means that the item is finished immediately!

This skill roll is modified by the complexity of the gadget - no modification for simple; -2 for average; -4 for complex; -8 for amazing.

Expenses: Creating new gadgets is costly. Tools, raw material, unusual parts, laboratory space etc., all require money. The Gadget Research Costs sidebar suggests the price which must be paid simply to confirm that the idea will work, before any production can begin.

Example: During a campaign set during the Jovian Wars (TS2) an agent of the Triplanetary Service (undercover as "Charles Keith-Stanley" of the Historical Division) wishes to make an Intruder Suit (p. UT86). The GM decides that this item, which distorts the appearance of the wearer, giving some small bonuses in combat and making him almost impossible to see, is TS5.

The GM rules that this is a complex item, so the base research cost is $25,000. Since TS5 is 3 tech stages above the campaign's TS2, there is an additional $150,000 (3 × TS Increment) research cost, bringing the total to $175,000.

After paying this expense, Keith-Stanley makes an Electronics and a Physics roll, each at -4.

Step 1: The Blueprints

The theory is correct! Now to build the device.

First, the plans must be drawn up. To find the man-hours required to design a gadget, take three times the square root of the research cost. The GM will determine the Engineering specializations needed. Multiple designers can work on a project at once, splitting the man-hours. The only cost is paying the engineers' wages and upkeep. Once the design process is complete, average the design team leader's Engineering skill with the average of all other team members' Engineering skill (round down). Roll against this number; critical success means a flawless design. Success means a good design with ½d minor gremlins. Failure results in a sloppy design with ½d minor and 1 major gremlin. Critical failure means the design does not pull together – the time is wasted and the design process must be started from scratch. Subtract 1 from the effective skill if the proposed design cost $1,000 or more, 2 if $10,000 or more, 3 if $100,000 or more and so on. Add bonuses for design tools like wind tunnels and so on; $1,000 in lab equipment adds 1, $10,000 worth adds 2 and so on to a maximum of +5. Basic equipment of the trade such as an integrating calculator for every engineer is mandatory. Each individual lacking such suffers a -1 penalty to skill and the effect of his time contribution is halved, so an eight-hour day is four man-hours.

The GM should decide the nature of each gremlin. A minor gremlin is something that is annoying but not critical. A major gremlin is something potentially crippling, like the power supply exploding when the device is subjected to shock.

Example: Marooned on an uninhabited moon, Steve and Nadia must build an ultrawave communicator to call for help. Such a device ordinarily costs $500, so it takes 67 (three times the square root) man-hours to design. If Steve and Nadia each spend 8 hours a day working on it, the design would be completed in just over four days – if they had design equipment. Alas, they have none, so each suffers -1 to skill and it will be done in the morning of the eighth day. Steve, the leader, has Engineering (Ultrawave) 22, while Nadia's skill is 14. Their average, after penalties, is 17. The roll is 11 – success! The device has ½d6 minor gremlins. Rolling determines one small gremlin. The GM rules that Steve's glassblowing skill was not quite up to standards, and the tubes in the set will be unusually fragile. Any shock will break one or more of them, disabling the set.

Step 2: The Prototype

This step requires access to appropriate parts and machine tools, and a big enough workshop, hangar or whatever to hold the assembled device while it is being built. It takes the square root of (research price / TS) man-hours to build and costs the same as the parts and tools separately. If the designers have to employ workers, their wages will increase the cost by another factor of 5. After the time and money are spent, the GM should roll secretly against the average Mechanic skill of the design team. A critical success means that they detect half (round up) of any gremlins in the design process and fix them. A failure means they require twice as much time to build it. A critical failure means an industrial accident takes place – the prototype is comminuted, people may be injured, the shop may catch fire or blow up etc.

Any parts that cannot be acquired must be built as separate gadgets.

Example: All the parts necessary to build an ultrawave set would cost $2,500 and the GM rules that Steve and Nadia are operating under TS0 conditions, so it will take 158 (the square root of 2,500 / 0.1) man-hours to build one – once they find all the parts.

The GM rules that all the parts necessary can be salvaged from the wreckage of their ship, except the main ultrawave tube itself, which is worth $500 by itself. The castaways will need to design and build that tube before going any further. After the design phase, it will take 71 hours to build it.

Step 3: Testing

This step is optional, but advisable if the device is going to go into production. Once a prototype is built a test crew should take it through its paces.

During each week of testing in which the gadget has undiscovered gremlins, roll against the operator's skill-3 (or the average skill-3 of a large crew). A critical success finds all the gremlins. A success finds one gremlin randomly. A failure means either that no minor gremlins show up, or that any unfixed major gremlin causes an accident. A critical failure means that the device broke regardless of whether it had gremlins.

If an accident happens, the GM should come up with a cause (related to a major gremlin, if there is one). If NPCs are testing the prototype, decide how badly it was damaged and whether they survived. If PCs are nearby, play out the results, allowing Mechanic rolls to spot the developing problem, Dodge rolls to avoid flying fragments and so on. Failing to successfully deal with the problem may result in an explosion or any other consequences the GM thinks fit the circumstances.

Example: Each week of use, if either Steve or Nadia make an Electronics Ops-3 roll, they will notice the fragility of their set's tubes.

Step 4: Gremlins Do Not Exist!

If a gremlin shows up in testing (on a success or a critical failure), fixing it is a two-step process. First, it requires a redesign of part of the vehicle. The time required is 5% of the time needed for the initial design for a minor gremlin, 20% for a major one. The GM should roll against the designer's Engineering skill with the same modifiers as the blueprint step. A success means they solve the problem. A critical success means they solve it in half the time. Failure means they don't solve it – but they can try again after spending more time. A critical failure means they think they've solve it, but the gremlin (or a new, different flaw) remains in effect.

Example: It would take 5% of 67 man-hours, or 3 hours, 21 minutes and a successful Glassblowing roll for Steve and Nadia to work out a way to create more durable tubes for the ultrawave set. Since they only plan to use the set once, they don't bother. The GM begins thinking about jolts . . . perhaps a seismic quake . . .

After a problem has been solved, modifications must be made to the prototype. This requires 5% of the original time required to build it and the original parts cost for each minor gremlin, or 20% for each major one. If the gadget destroyed itself, a new prototype must be built – once the problem is solved, no extra time is required to build the modification into the new prototype.

Step 5: Production

The single prototype may be the only version of the gadget ever built – as in the case of Steve and Nadia's ultrawave set – or it can be used as a model for other devices. Once the design team has found all the gremlins (or has given up looking) the device is "type-standardized" and ready to enter production. If testing failed to find and correct all the gremlins, they will remain a permanent flaws in the device's design.

Limited Production: One a device is type-standardized, copies of it take less time to build. Divide the time it took to build the prototype by 3 – that's the time it takes for each example. The cost of each copy is 20% of the base price for parts alone, or 100% of the base price including labor.

Mass Production: Setting up a mass-production line costs 20 times the base price of the device. (It also takes up at least 100 times the volume of the device.) Each line can turn out one device in one-tenth the time it took to build the prototype. The cost is 20% of the base price for parts, or 50% of the base price including labor.

Variants: If the device is based on an existing design and the major changes are in details (e.g., increasing or decreasing the power supply by up to 50%, adding "bell and whistles" that do not change the major functionality of the device, the device is a variant. Treat designing a variant like designing a new device, but at 10% of the listed time. Gremlins only appear on a failure (one gremlin) or a critical failure (two gremlins).

Combined Example

More than fifty of the most brilliant scientists of Civilization are researching the negasphere. They begin their work at TS6, led by Worsel and Kimball, who can co-lead because of their telepathic abilities.

The negasphere is an "amazing" device, a Stage beyond anything currently known. It thus has a base research price of $60,000. No one is worrying about the cost of parts and labor – the War Department's budget can handle it. Developing and unifying the multitude of wildly divergent theories to the point where actual design can begin takes a full year, but eventually produces a set of equations – and an entirely new branch of mathematics, devised especially for them!

Drawing up the plans takes 735 man-hours – fifty Patrol engineers, led by Master Tech Thorndyke, accomplish this in two stressful days of shouting. They succeed on their skill roll, the bonus from the availability of the finest equipment more than compensating for the penalties from the complicated design. Their future problems are limited to three minor gremlins.

It will take 10,000 man-hours to construct the prototype. The fifty techs do it in a month.

Testing begins, and all three gremlins are found. Fortunately, no lives were lost, and only two techs were hospitalized with radiation burns.

It takes 37 man-hours to isolate each of these gremlins, and the same amount of time to fix them.

The negasphere is now ready to enter production. Future negaspheres each take only 245 man-hours to hand-build – a crew of ten can turn one out every three days. The Home Front, though, sets up mass-production lines, hangs signs on the wall reading "Take the Day Off: Boskone Says It's Okay" and turns them out at 73.5 man-hours each – each ten-worker team produces one every shift.


Gadget Complexity

Simple gadget
e-m radio, chemical explosive
Average gadget
ultra-wave communicator, spy-beam
Complex gadget
blaster, force shield, thought screen
Amazing gadget
sunbeam, negasphere
Starkly unimaginable gadget
automatic computer, inertialess drive, neuro-electronic interface – impossible without Arisian inspiration.

Reverse Engineering

If a gadget was seen in use but is not available to the engineer (perhaps it was destroyed in use, like the first primary beams, or it is still in the possession of unfriendlies, like the first hyper-spatial tube), it can be reverse engineered. This process is carried out exactly like original research, but the complexity level of the gadget is one lower (simple gadgets are unaffected). What constitutes "seen in use" is up to the GM. A partial glimpse as one flies by is insufficient; significant data must be collected.

"I Need It Tomorrow!"

All times mentioned in this section assume that the engineer works eight hours a day. If he works 16 hours a day, time is cut by 50%, but he must make a HT roll each morning or lose fatigue as if he only got a half-night of sleep (see sidebar, p. B134). Fatigue lost in this manner can't be regained without taking a break from the project, which will add 1d days to it! If the engineer has the Doesn't Sleep advantage, only 1 fatigue roll per week is necessary.

Engineers may also save time by cutting corners. Every 5% of project's original time requirement that a job is rushed penalizes the effective skill by -1. A job that should take a month can be finished in three weeks if the engineer can make his roll with a -5 penalty.

Gadget Research Costs

Find the Base Cost of researching a new theory to the point where a gadget can be designed. Add to it the TS Increment, times the number of Tech Stages which the gadget is in advance of the campaign.

Complexity Base Cost TS Increment
Simple $5,000 $10,000
Average $10,000 $25,000
Complex $25,000 $50,000
Amazing $50,000 $100,000

Salvage and Cannibalizing

Removing a component from one device for use in another is salvage if the original device no longer works, cannibalizing if the original worked (until you took it apart). In either case, a skill roll is required as if the original device were being repaired, but at +3. Success yields a working part. Failure damages the part you were trying to get.

Reliability (Optional Rule)

It is an unavoidable fact of life that vacuum tubes burn out and break, brushes wear down, wave guides flex out of alignment and so on. Equipment must be maintained.

Every piece of equipment is given a reliability number and rate. If the equipment is regularly tended by someone with the appropriate Mechanic skill, add one-fifth of that skill to the reliability number. Roll three dice as often as the rate indicates. If the number rolled is less than the reliability, the equipment performs flawlessly. If it exceeds the number, it begins breaking down, and becomes useless over the period of time indicated by the rate. Only on a critical failure does it quit working instantly. The amount by which the reliability roll was missed is the breakdown severity.

During the period between a failed roll and the resulting breakdown, a mechanic can try once to fix the problem, by rolling against his skill, minus the breakdown severity. On a critical success, the problem is completely fixed, and normal operation resumes. On normal success, the problem is patched, and the equipment will continue to function one additional reliability period; it will break down two periods from now. A failed roll simply means the equipment will break down when previously indicated; a critical failure causes immediate breakdown.

If a piece of equipment breaks down, it is completely non-functional until the repairing engineer can roll his appropriate skill, minus the breakdown severity.

Example: A captured Bergenholm in poor condition has a reliability number of 10 and a period of daily. Senior Chief Electronics Technician Simmons has Mechanic (Bergenholm) 15. He must roll a 13 (10+15/3) or less every day or the drive will begin to have problems. One day he rolls a 16, failing by 3. The Berg has developed a severity-3 meter-jump. He must roll a 12 (skill-3) to fix it, and gets 11. He has held it together one more day. The next day, he rolls again, but gets a 14. The day following that, the Berg quits. He'll need a 12 (skill-3) to fix it and resume the normal maintenance cycle.

Lab Notebooks

Any competent scientist, engineer or technician of any specialty keeps lab notebooks detailing any work he does – failures as well as successes. Even the wildest jerry-rigged field repairs will be documented as soon as he gets a chance. (Especially if they actually work!) These documents are utterly invaluable to anyone attempting to reverse-engineer his efforts. Depending on the thoroughness of the writer, possession of his notebooks both count as having seen the device in use and further reduce the expense required to duplicate his efforts by up to 30% and time by up to 90%. (For a random, anonymous engineer, roll ½d × 10% and 6d+3 × 10% respectively.) The reader must still make the required skill rolls – the writer may have made mistakes!

For example, Agent Keith-Stanley obtains lab notebooks describing the early research of an Intruder Suit. The Suit would be complex, but the notebooks reduce it to average. Secretly, the GM determines that it would take Keith-Stanley 8 days and $85,000 to research the Suit on his own, but that the notebooks reduce expenses by 25% and time by 60%. Keith-Stanley's research then takes 3 days and costs $63,750. Thirteen hours in, Keith-Stanley must make an unmodified skill roll. Production cost is unaffected.

Because of their value, sensitive lab notebooks are usually very well hidden and protected – sometimes even encrypted. A chance to photograph an enemy scientist's notebooks is a spy's dream.

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