Building Jump Drives With Warp

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The Traveller universe is one of the oldest RPG settings still around, and remains one of the most interesting and fun to game in. And Jump Drives are one of the key features of this setting. Every Jump Drive has a "J-number" indicating how many parsecs it can travel (from J-1 to J-6). Jumps cannot begin or end within 100 times the diameter of any planet or star (the "100D Limit"). Each jump requires a tankful of hydrogen and takes approximately one week, regardless of the distance jumped.

With these built-in assumptions, I thought it might be interesting to try designing this style of Jump Drive using Warp. Much like I did with Gadget Pools, I'm going to present the final version first, then explain how I got those numbers afterwards for those who are curious enough to continue reading:

Special Modifier for Warp

Jump-Drive: A variant of Hyperjump, your Warp works like the Jump Drives in Traveller (see details in the first paragraph of this page). The basic penalty to your Navigation (Hyperspace) roll is based on your Jump Drive number and the distance you wish to travel. This assumes that you're jumping to a charted system and that you have access to an astrogation system with appropriate charts. Jumping without them (or to an uncharted system) is at an extra -3 to skill, costs 2 FP per +1 to the roll, and any failure is treated as a critical failure (use the Traveller mis-jump rules)!

J-NumberSkill PenaltyModifier
J-2-14 plus -2 per parsec jumped-10%
J-3-12 plus -2 per parsec jumped-5%
J-4-10 plus -2 per parsec jumped+0%
J-5-8 plus -2 per parsec jumped+5%
J-6-6 plus -2 per parsec jumped+10%

I've seen a few other people take a crack at it, but the results either ended up feeling arbitrary or (more often) didn't differentiate between jump distance. It's difficult to do so -- Warp doesn't allow you to claim a limitation for a range limit if you can jump over 100,000 miles (a reasonable rule, to prevent point crocks) and the penalty for jumping one parsec is the same as that of jumping six parsecs! However, it occured to me that I could use various levels of Reliable to maintain a difference between jump distances.

First, the basics. Travelling from 1-6 parsecs in a week results in a travel speed of between "one light-year per 2 days" and "one light-year per 0.35 days". On average, that seems to equate fairly to the -25% level of Hyperjump, with the fact that it always takes one week as a special effect. I then turned the following into a single -10% Nuisance Effect limitation: Must jump in whole parsecs; Cannot exceed jump rating; Cannot start or end jump within 100D limit; Requires a tankful of hydrogen.

A jump of 1-6 parsecs has a base penalty of -18 to skill. Every system has been fully mapped out and loaded into astrogation databases; the jump will thus always be to a place you can "fully visualize" but cannot see (another -2 to skill). Jumping to an uncharted system should be possible (at -5 to skill instead of -2) but incredibly dangerous, bought as a "limited enhancement" (p. B111): Blind (Any failure is a critical failure, -80%), +10%. Obviously, critical failues should use the Traveller mis-jump rules, because they're a lot of fun.

So, we're at -20 to skill for a jump. I now want to include a variable level of Reliable based on how far we're actually jumping. The idea is that the more you "under-jump", the greater the bonus (to help offset that penalty); +2 per level seemd about right. I ended up using the rules for variable levels of Costs Fatigue (Powers, p. 101), which produced a reasonable result. The J-6 version exceeded the normal limits of Reliable slightly (+12 at the extreme), but considering that you're paying for a six-parsec jump and then only using 1/6 of that, it didn't seem unreasonable.

Obviously, J-6 has six "levels" of jump. We want to get two levels of Reliable per parsec, inverted (i.e., +2 at 6 parsecs, +4 at 5 parsecs, +6 at 4 parsecs, +8 at 3 parsecs, +10 at 2 parsecs, and +12 at 1 parsec). J-6, like all versions of this modifier, has a "per level cost" of +10% (for Reliable +2). Its "average use" is ((1+6)/2), or 3.5 levels. Since we're buying Reliable in multiples of 2, I'm retaining the fraction. The final cost is +35%.

J-5 has five "levels" of jump, and thus ranges from +2 (for a 5 parsec jump) to +10 (for a 1 parsec jump). The "per level cost" remains +10%, and the "average use" is ((1+5)/2), or 3 levels. Final cost is +30%.

Similarly, J-4 works out to +25%, J-3 is +20%, J-2 is +15%, and J-1 (which really just consists of unmodified "Reliable +2") is +10%. For all of these versions of Jump Drive, the operator will be at a -18 penalty to jump the farthest distance possible, reduced by +2 for every parsec that he "under-jumps".

This has the final effect of making higher numbered jump drives cost more while also being more useful, because they incorporate a larger number of levels of Reliable. It's up to the GM whether or not to allow further levels of Reliable with these modifiers; it's certainly reasonable to argue that the J-1 version can add another +8 at least, but that might make the higher levels seem less attractive. Use your own judgment, as always.

Random Tangent: Enhanced Move and c

A random bit of data that didn't really fit anywhere else: The speed of light is approximately 9.75 x 225 yards per second. So the average character (Speed 5.00) will want to take Flight and 25 levels of Enhanced Move (Space) to travel at the speed of light. Acceleration to that speed will take a little over a year, though, so I'd recommend adding Cosmic (+50%) to eliminate the need to accelerate.

Thus, a quick way to figure out how fast you can travel, relative to the speed of light, is to subtract 25 levels from your Enhanced Move (Space), then apply the remainder to your Space Move. Divide the result by 9.75 and that's your multiple of c. For example, the Teal Flashlight has Space Move 17, and 27 levels of Enhanced Move (Space). We subtract 25 levels from the Enhanced Move, leaving 2, and apply it to the Space Move for a result of 68. We divide that by 9.75 to get 6.97. So the Teal Flashlight can fly at almost 7c, seven times the speed of light.

All of the above assumes that FTL travel is allowed in the campaign, of course. If not, but "reactionless drives" still exist, then there's little point to buying any levels of Enhanced Move; instead, space fliers should buy up their Space Move (at +2 points per yard/second), as all realistic space travel rules use Acceleration (in G) to calculate travel times and performance. Divide Space Move by 10 to get Space Acceleration; even with fractional Accleration, one can eventually approach the speed of light... though it may take centuries.

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