Build:Impulse Propulsion System
6.2 Impulse Propulsion Systems
(Required)
Cost: Varies
Starships use impulse propulsion systems (IPS) to move slower than the speed of light, which is required for travel within a star’s gravity well, through solar systems, in starship combat, and similar situations. Impulse drives use fusion reactors to generate standard thrust via a standard Newtonian reaction—the thrust “pushes” the ship forward through space. Starships usually drop to impulse when they encounter another ship to facilitate contact (or combat).
IPSs have four components: the impulse reaction chamber (IRC), or fusion reactor, of which there are three per impulse engine; the accelerator/generator (A/G); the driver coil assembly (DCA); and the vectored exhaust director (VED). Energy released in the IRC by the fusion reaction is channelled to the A/G, which raises the velocity of the plasma and feeds it on to the DCA. Electroplasma system (EPS) taps run from the A/G to divert some energy to power other systems on the ship. The DCA creates a field effect which aids the impulse propulsion process, then passes the energy on to the VDA, which directs it to thrust the vehicle in the desired direction.
6.2.1 Chemical Propulsion Systems
Cost: 10 x Size
The earliest space vessels, such as the DY-100 class, used chemical propulsion systems which generated thrust by burning liquid oxygen and hydrogen as fuel. Ships with these engines can achieve velocities of up to 40,000 kilometers per hour, or 11 kilometers per second (approximately .00004% of the speed of light, or .00004 impulse). Compared to more advanced vessels, they are extraordinarily slow, clumsy, and primitive. A ship with chemical propulsion carries enough fuel for a number of seconds of burn equal to Size x 100.
A vessel with a chemical propulsion system has small internal batteries to provide sufficient power to run its minimal systems, such as life support and crude sensors (it can also have solar power generation, if desired). The crew makes do with stored food, gravity generated by rotating the ship, and so forth. The Narrator must evaluate and approve all equipment installed on a ship with chemical propulsion; most systems listed here or in Spacedock are not appropriate for these ships (in particular, ships with chemical propulsion cannot mount weapons, except perhaps for a single chemical or nuclear rocket launcher).
6.2.2 Atomic Piles
Cost: 10 SU
Available: 2040
Primative impulse engines arrived before warp technology was discovered and, due to their reliance on the new shipboard fusion reactors, were often referred to as ‘atomic piles.’ The first vessels to use other than chemical propulsion were those of the Columbus interstellar sublight explorer series, and these early fusion-powered engines were notorious for their quirky and dangerous nature. Being older and less-developed than their later full impulse cousins, they are much larger (10 SU) and less powerful.
6.2.3 Main Impulse Engines
(Required)
Cost: Varies
Available: 2063
A main impulse engine (MIE) capable of propelling a starship consists of four linked impulse engines. These engines may be grouped together, or divided into two groups of two to provide balanced thrust for structures such as separated saucer sections.
An impulse engine is rated for the amount of velocity it can provide, expressed as a percentage of c (the speed of light). Thus, an impulse engine might be said to provide .5c thrust, meaning it can propel a vehicle at half the speed of light. Regardless of an engine’s maximum sublight speed, Starfleet generally limits impulse travels to .25c (paradoxically referred to as “full impulse”) to minimize the time-dilation problems which occur as a ship approaches speed of light travel. An impulse engine’s Standard speed is .25c or its listed Sustainable speed, whichever is less. Only in starship combat situations do starships commonly move at impulse velocities in excess of .25c.
Impulse engines are also equipped with impulse capacitance cells which can provide a tiny burst of power to them. By releasing the cells’ power directly into the driver coils, a ship can generate a one-second burst of impulse speed when the engines are otherwise not functioning due to lack of power.
A typical Type-series impulse engine can maintain Maximum impulse speed for a number of hours equal to Type + 1 before exhausting its fuel. (For example, a Type 6, 6A, or 6B engine could maintain maximum speed for seven hours.) If a ship runs out of impulse engine fuel, it cannot fly at impulse speeds or supply power from the impulse engines to other systems. Since impulse engines use deuterium for fuel, a warp-capable starship can drain deuterium from the matter tanks supplying the matter/antimatter reactor to power the impulse engines if necessary, but then risks running out of fuel for the warp propulsion system. Production developments allowed for a more efficient and proficient impulse engine starting in2303, resulting in a new series name. Type-series engines that saw enhancement became Class-series engines and also enjoyed the increase in fuel range.
The accompanying table lists the classes of MIEs available.
Table