Auxiliary Power Unit

An auxiliary power unit is an additional source of power generation separate from the powerplant that can be installed onto a vessel to satisfy additional power needs, or to increase power efficiency. There are two types: storage and generation.

Both types do not currently require maintenance, and any can be installed on all spacecraft, regardless of their size.

Magnetoplasmadynamic Generators (MPDGs)

Magnetoplasmadynamic generators (or MPDGs) utilise the electromagnetic fields generated by flowing propellant plasma to generate electricity. They operate in a closed cycle, meaning that spent plasma is returned to the reactor for reheating.

MPDGs are desirable for captains who prefer propellant efficiency and immediate power production above all other factors. Exchanging a military-grade turbine for a single turbine and an MPDG can reduce the dry mass of the vessel while providing a similar or greater amount of power, all while increasing power generation efficiency by a factor of 5.

Generators

Name	Power Consumption	Thermal Consumption	Power (nominal)	Mass	Price
MPD5035	50 MW	0.5 GW	350 MW	2,500 kg	300,000 E$
EIPFG MkIV Big Furnace Generator	100 MW	1 GW	700 MW	4,000 kg	500,000 E$
MPI Town-class MPDG	150 MW	1.5 GW	1,000 MW	8,000 kg	800,000 E$

Superconductive Magnetic Energy Storage (SMESes)

Superconductive magnetic energy storage systems (SMESes) store energy in the magnetic field of a superconductive electromagnet. They can store massive amounts of power, but their charge and discharge rates are limited, unlike ultracapacitors.

SMESes are desirable for captains who prefer low dry mass, and whose ships occasionally outpace their power generation capacity. Vessels with mass drivers and other high-power devices tend to also need manoeuvring capability, and a SMES can provide a comfortable buffer during times of high power load.

Power capacity, like ultracapacitors, is measured in megajoules. One megajoule over one second is equal to one megawatt, as watts are joules over time.

Storage

Name	Energy capacity	Charge power draw	Discharge power (peak)	Mass	Price
NDAPS	18,000 MJ	100 MW	3,000 MW	1,000 kg	400,000 E$
MPI Town-class storage	32,000 MJ	150 MW	3,000 MW	2,000 kg	800,000 E$
EIUP MkII Unlimited Power	50,000 MJ	200 MW	6,000 MW	3,500 kg	1,200,000 E$