SPACECRAFT FUEL USAGE

         In the early days of space flight, where spacecraft used chemical propellants and therefore their mass was highly variable, meaning that at their arrival at destination they have lost a great deal of mass, or had discarded various stages, which now litter their route. Fortunately the development of fusion drive and later antimatter drives replaced the need for ships to become flying fuel tanks to ever reach their destinations, now ships store enough fuel to enable them to use drive for months or years at a time without refueling, in a volume that never generally exceeds 10% of the ship’s volume.

            The difference is that modern drives produce a great deal of energy from fuel, fusion drives can be made to be hundreds of times more efficient than chemical drives, and advancements in driver core technology allowed fusion to generate power for the needs of trans-c flight. Fusion only liberates energy by reshuffling atoms to change their binding energy, the mass energy conversion is only a percent or two when the energy needs of the other processes are accounted for, but with antimatter the mass energy conversion is total, and in a well balanced reaction there remains no exhaust product as everything is converted into radiation, this makes it another couple of magnitudes more productive than fusion, which already is several magnitudes better than chemical reactions.

            The result of exploiting these high energy reactions is that a ship of a mass of several hundred tons need only carry a few tons of fusion fuel or a smaller amount of antimatter, and rather than keeping this as an external fuel tanks which can be jettisoned the fuel storage compartments are kept within the ship, and therefore have the protection of the hull, which although is less crucial for liquid hydrogen, is rather more important for the containment of antimatter. Also although the ship loses mass over the time of its flight the change does not effect greatly how the ship handles, in fact in the case of closed fusion drives (that is the fusion exhaust is used to power driver coils, rather than being accelerated and vented as in traditional drives, and therefore the exhaust retained) the change in mass is almost negligible on any short trip.

            The amount of fuel carried by a craft roughly is determined by its function, a small interplanetary craft will usually work with hydrogen as their power needs are not very great, and consequently it will carry maybe a few tons of liquid hydrogen, which via a closed fusion cycling engine could provide it with enough drive and craft energy for up to a year or more. Larger interstellar craft necessarily needs more energy, and most use antimatter which requires a lesser volume than liquid hydrogen fusion processes only, a large vessel may carry upwards of a thousand tons of hydrogen and anti-hydrogen, which would provide for many years of continuous flight at thousands of c or higher.

            Both in fusion and antimatter reactions the produced trans-c speed is proportional to the amount of energy supplied, therefore it consumes much more fuel to travel faster than traveling slowly. But this relationship is not direct, and this stems from the efficiency of the driver coils. If the trend was direct, then using Y tonnes of fuel at a high rate will allow you to travel over X distance in a short time, but if used at a lower rate then Y tonnes of fuel still allows you to travel X distance in a longer time, this not actually true in reality. Spacecraft have certain speeds at which they are more efficient than at others, and in all cases they get increasingly less efficient the faster you go, this means while at low speed Y tonnes will get you X far, at high speed Y tonnes gets you less than X distance. This relationship means that spacecraft have a number of different traveling modes which make the best o the peculiarities of their own coil set.

            Though Federation operates without money, as do all its constituent races, but there is still a value to antimatter. Although any ship can refuel anywhere without any cost, the consumption of antimatter is very closely monitored, it is basically a resource that is very hard to generate, and so its flagrant use is discouraged as the amount of produced antimatter dictates in its own way the number of craft that can be supported.

            Refuelling can be performed in a number of different ways, for craft who simply run off hydrogen, this material can be collected from certain regions in space and then distilled (purified of troublesome isotopes) for drive use, this in practice means that they may never need to refuel at a station or docking facility, but the harvesting process is usually slow and performed in hazardous environments such as a sun’s corona, often means that most craft stop at facilities to collect fuel. Also returning to facilities for refueling allows the ship to be checked over and repairs made, as craft carry enough fuel to travel uninterrupted for long periods of time, refueling is usually part of the standard maintenance schedule for a craft, with craft rarely coming in just to refuel.

            Most large facilities and harbours offer both hydrogen and anti-hydrogen, cutting edge flight bases can also offer more exotic fuels for prototype and experimental craft, such high proton number antimatter isotopes. The transfer is by the hard points on the ships hull which allow for umbilicals to attach, and fuel transferred into storage compartments. The reverse process also occurs where fuel is taken from a craft to the facilities own reserves, in this way large ships with good carrying capacity act to deliver fuel to these small stations, or act as stations themselves. On some primitive colony worlds antimatter is also taken off any craft prior to landing, as they may lack the containment equipment to ensure planetary safety, this practice may also be observed on more developed worlds, where the potential loss of containment may seriously harm many people if surface safety fields are overwhelmed.