Wednesday, 23 May 2012

Jump Drive Performance Spreadsheet

The table below shows the theoretical fuel efficiency values for jump drives for TL's 10 to 15 as well as hypothetical values for TL's 16 to 18 for speed ratings 1 to 10. The value given is the percentage of ship mass required in fuel to travel 1 parsec.

TL J 1 2 3 4 5 6 7 8 9 10
10 1 10.0 22.7 36.6 51.3 66.8 82.8 99.4 116.3 133.7 151.4
11 2 5.4 12.1 19.6 27.5 35.8 44.4 53.2 62.3 71.6 81.1
12 3 3.7 8.4 13.6 19.1 24.9 30.8 37.0 43.3 49.7 56.3
13 4 2.9 6.5 10.5 14.7 19.2 23.8 28.5 33.4 38.4 43.5
14 5 2.3 5.3 8.6 12.1 15.7 19.5 23.3 27.3 31.4 35.6
15 6 2.0 4.5 7.3 10.2 13.3 16.5 19.8 23.2 26.6 30.2
16 7 1.7 3.9 6.3 8.9 11.6 14.4 17.2 20.2 23.2 26.3
17 8 1.5 3.5 5.6 7.9 10.3 12.7 15.3 17.9 20.6 23.3
18 9 1.4 3.1 5.1 7.1 9.2 11.5 13.8 16.1 18.5 20.9
Time (hours) 168 84 56 42 34 28 24 21 19 17
Speed (c) 170 340 511 681 851 1021 1191 1361 1532 1702

Here's a spreadsheet for calculating the fuel use ( link ) taking into account wear and tear on the ship and the results of Engineer and Astrogation rolls. Enter the ship details and then the journey details in the yellow coloured boxes. Adjust the throttle value until you have a valid journey with fuel left at the end. Update the two values for distance travelled on the ship data (manually I'm afraid) and your ship will deteriorate before you eyes. Calculating cells are protected (but not password protected).

I tried to find a way of embedding a working spreadsheet in the blog, but to no avail.

The formulae used and the constants they use are arbitrary - they give a nice range of figures and allow idiots (sorry, player characters) to go pedal to the metal and waste fuel.

Speaking of fuel, next bit of rule finagling will be to sort out how fuel works (and costs) as well as what purifying hydrogen actually means.

Tuesday, 22 May 2012

The universe and J-drives

A universe, yesterday (it was there when I looked out the window)

This post is all about J-Drives and how I'm messing with the rules. First of all a bit of babbling about the universe (my universe that is, yours may vary) as a bit of an exercise in getting my brain working.

Concentric universes expanding of a Big Bang (or Big Drip)
The (my) Universe is a topologically closed 4D hypersphere. Normal spacial dimensions x, y, z are all we are aware of, the universe is closed in the w dimension. Collapsing x, y and z to a single dimension you can visualise the universe as a circle. Everything in the universe we can observe is confined to the line of the circle.

The circle (and universe) is expanding from a point (the Big Bang) along the w dimension.

OK for fun, if we assume that a universe is possible (it is, I've checked by looking out the window), then so is another. So we can assume that if there is some point in the u, v, w dimensional space where universes can spawn once, maybe it can happen again, and again and so on.

So picture lots of circles all expanding from the same point, all separate universes separated by a void in the w axis (and u and v axis too, but I won't go there). This void is hyperspace.

Of course the circle isn't perfect, its wobbly. Where mass slows the expansion you get slopes forming that we perceive as gravity in the universe. Black holes possibly make big holes that could go all the way through the w axis void and connect universes.

Some space being warped, the w-surface is getting wobbly
Because of this gravity thing, antigrav drives in traveller are an earlier bit of the same sort of technology that leads on to M-Drives and J-Drives. M-Drives are very powerful antigrav devices (in terms of force), but act over a very short range (at the atomic level) and can push or pull on the surface of the universe, the w-surface that is, an provide an impulse to the space ship - this is why M-Drives don't use fuel themselves as propulsion, but run on the energy from the P-Drive.

Using an M-Drive induces small wobbles on the w-surface. Powering up the J-Drive causes bigger wobbles warping the space around the ship which causes an apparent speed exceeding the speed of light.

At this point the bubble of space around the ship breaks off from the x, y, z space and enters hyperspace. The J-Drive then propels the bubble and ship through the w-void until such point the ship re-enters normal space (hopefully close to where you want to go).

Black holes - don't go there!
With higher level of technology, J-Drives gain better control of the bubble and allow faster speeds for the same expenditure of energy.

Remember space being warped by mass? You don't want to go there in hyperspace, it would be like hitting a massive wave while surfing, you'll bounce off deeper into hyperspace, lose your grip on the real universe and end up god knows where. This is commonly referred to as a miss-jump but is better known to those who have tried it as an "Oh my God, we are all going to die!" moment.

A good astrogator is able to navigate a course through w-space and reduce the effective distance travelled in the real universe, making the journey time shorter. A bad one can get you lost forever.

Good engineers can tweak the J-Drive to make more efficient use of the energy holding the bubble in w-space, a bad one can stall the drive, precipitating the ship out of hyperspace too far from a planet without enough fuel to get there or restart the J-Drive.

Coming up next, some rules and a spreadsheet for J-Drives in the Felonverse.

P.S. None of this is true, or at least provable.

Image Credits : Images linked from elsewhere, if Google can show 'em them so can I. Hover your mouse over the image to find its source.

Saturday, 19 May 2012


An orbital habitat from a previous campaign
This is where I'm going to save everything to do with the traveller campaign I'm just about to start.

Sword Worlds Sector in 1115
The rules I'll be using will be Mongoose Traveller, with a few tweaks.

The setting will be the Sword Worlds, in the Spinward Marches shortly after the Fifth Frontier War (1107 to 1110), which did not go particularly well for the Sword Worlds. The characters penultimate term will be during the war itself, the final term being during the aftermath and the formation of the Border Worlds.

I'll be using the Sword Worlds character generation rules written by Shannon Appelcline published in Signs and Portents #80 by Mongoose Games.

The big tweak I'll be making to the rules is jump travel. Rather than the classic 1 week jump system, I'll be using a more warp drive type method drawing on the SF works of Ian Banks amongst other sources for how the black boxes work. I'll write up the rule mechanisms in a post of its own, but the principle is that the fuel efficiency will vary dependant on the drive rating, actual speed travelled, the wear and tear on the drive and the skill of the engineer.