The ionic repulsion drive is the standard mode of conveyance for most space vessels. The Cobra Mk III is fitted with two Kruger “lightfast” motors, each capable of 1.21 gigawatts power. This provides a top speed of just over 30 light mach.
The motors are mounted either side of the ship's centreline in approximately the centre of the engineering section at the rear of the ship. The large plasma vents allow maximum yield of charged particles from the motors.
The w and s controls on your Astrogation Console will increase or decrease the velocity.
How does the engine function? What is it that is actually coming out of the back of the 'thrusters' (blue-tinged something)? How can it work without using fuel? The traditional answers in Oolite circles involve the use of Handwavium. But note this: in Oolite much of what is, is because it is deemed to make the game more playable. Classic Elite's engines worked in this same way, it was much more playable than the more realistic Newtonian Frontier family of games, so Oolite sticks with it - especially since the game started as a rewrite of Elite (with minor tweaks) for the AppleMac!).
There seem to be two main theories about the workings of the engine. These differ on their approach to Newtonian physics. The auto-compensation approach holds that the Newtonian underlying reality is masked by the astrogation computer, which corrects the flying experience to make it seem non-Newtonian. The phlogiston approach sticks with non-Newtonian physics and is rather more dramatic!
See the discussion in 2009. The following points were made:
- We have speed control rather than thrust control (phonebook)
- Debate about a faulty auto-compensation theory, assuming retro-thrusters which the astrogation computer uses for correcting flight.
- Our ships have big flaring jets of something blue and glowing coming out their rears, that get bigger when we go faster. But when we slow down, there are no big jets shooting out the front. Plus, again, no fuel is used – so these can't be rocket motors. We're forced to turn to technobabble and explain the rear jets away as being some sort of trailing wake of disturbed spacetime, left behind by our thoroughly non-Newtonian system drives ... (Disembodied)
- normal space-drives burrow through the semi-rigid phlogiston leaving glowing subspace channels that heal at a constant rate, like hot boiled prunes through icy jelly (Aegidian)
Trawling through the BB will reveal other such discussions.
- 2007: Disembodied's original theory - see later discussion
- 2008: Selezen on engine plumes, Newtonian Physics, propulsion & artificial gravity (2008)
- 2009: Oolite Engine Function Question: both theories, musings about the inside of a ship (JameSpal), physics (KZ9999)
- 2010: See bottom of this post
- 2021: How does my Cobra's energy supply work? Nite Owl's alternative theory
This all comes under the general category of Handwavium
Disembodied's lengthy disquisition from 2009
A ship's drive accelerates quirium particles in a closed circular particle accelerator – a torus – thus manipulating the fabric of spacetime, drawing it in at one end and pushing it out at the other. The faster the quirium spins, the faster the ship goes. No quirium is consumed in the process. Properly maintained, a closed quirium torus could propel a ship indefinitely.
nifty diagram of a Witchspace "broomstick" drive: Top view: (bow) <----O----## (stern) Side view: (bow) <----=----## (stern)
When local spacetime is sufficiently flat, i.e. not distorted by a large mass or by the actions of another nearby drive, it can propel the ship at around lightspeed. If local spacetime is too distorted, this torus system can only operate at a fraction of capacity: 0.2C, 0.35C, etc. In these distorted conditions, spinning the quirium at full speed would cause it to rapidly decay, bringing the whole engine to a crashing halt in milliseconds. The "Witchdrive fuel injector" system gets round this, by constantly topping up the quirium in the torus from an external tank.
Of course, the ship doesn't actually move at all: it remains stationary, while space itself is hauled in at one end and rammed out at the other. Because of this there is no inertia, hence the non-Newtonian flight characteristics. When the ship appears to "turn", it's actually revolving the entire universe around itself. Because the torus is fitted in the horizontal plane of the ship – see nifty diagram above – it's easy to move the ship (or rather it's easy for the ship to move the universe) up and down vertically, but almost impossible to move it horizontally. However the ship can be spun around its longitudinal axis (or rather, the universe can be spun around ... you get the idea) by rotating the drive assembly. Some progress has been made towards "yawing" by building a smaller torus set at 90° to the main loop, and spinning it either clockwise or anticlockwise. The internal strain on the ship, and on the drive train itself, though, is massive, and personally I think this is just a passing fad with no real advantage.
The "exhaust" is caused by spacetime emerging from the Witchdrive: as this spacetime wake merges back into the normal flow, the particles and antiparticles constantly being produced from the quantum foam are briefly travelling faster than light, and hence give off the distinctive blue-purple glow of Cherenkov radiation. The faster spacetime is moving as it emerges from the engine, the more intense the glow. The conical shape is a three-dimensional section of the four-dimensional wake.
(This was all summed up much more neatly by Aegidian, who described the drives as "burrow[ing] through the semi-rigid phlogiston leaving glowing subspace channels that heal at a constant rate, like hot boiled prunes through icy jelly.")
A large enough mass of quirium, spun sufficiently fast, can distort spacetime to such an extent that it can tear open a wormhole. Again, the faster the quirium spins, the longer the wormhole. Accelerated to 99.9999...% of C (constantly topped up from an external tank, as the accelerated quirium decays), the wormhole can reach a full 7 light-years. If it was possible to spin the quirium faster than light, then theoretically the wormhole could be even longer – but it's not possible. (Explanations wanted!, 2009 ).
- Engine Sound allows the sound of the engine to be heard in game
- Q-Charger increases speed at a cost in both fuel and energy
- Hard Way (part of the Strangers World suite of oxp's) causes the engine to consume fuel in its operation.
- Breakable Engines introduces a new breakable equipment System Drive listed on the Ship's Manifest.
- Ship Configuration OXP allows a choice of 42 ship's engines with implications for cargo space and weight. There is also a choice of some 39 varieties of Thruster and 7 classes of booster. Warning: a very complicated OXP!