User:The All-knowing Sith'ari/EHD lifter drive

The EHD (Electrohydrodynamic) lifter drive is a United Nations Space Command propulsion system used to produce lift in atmospheric vehicles without the need for combustion, moving parts, or wings.

Mechanics and operation
The basic principles of the EHD drive can be seen in the Ionocraft, a simple flying machine that utilises the Biefeld–Brown effect to produce thrust in the air. The basic components of the EHD drive are two: an ioniser and an ion accelerator. Ionocrafts form part of this category, but their energy conversion efficiency is severely limited to less than 1% by the fact that the ioniser and accelerating mechanisms are not independent. Unlike the ionocraft, within the EHD drive, the air gap in its second stage is not restricted or related to the Corona discharge voltage of its ionising stage. Also, EHD drives are not restricted to air as their main propulsion fluid, and work perfectly in other fluids, such as oil, but it is most common to see them used as atmospheric propulsion.

The first stage consists of a powerful air ioniser which, when supplied by high voltage in the kilovolt to megavolt range, ionises the intake air into ion clouds which flow into the second stage of the device. The second stage consists of one or multiple stages of ion accelerators, powered by voltages in the kilovolt or megavolt range, in which the ionised air is moved on a straight path along the length of the accelerating unit. Movement of the ion clouds can be electronically controlled to increase the effective efficiency. The ionised air is forced out the end of the drive engine, producing thrust.

History and applications
The first serious attempts to design EHD-based aircraft were made on Earth in the 1960s. They were, however, abandoned due to technological limitations, one of which was the need for a high voltage power supply for the device. The development of compact fission, and later, fusion reactors, in the early 21st Century that could be carried by vehicles meant that they could now meet the power requirements necessary for EHD drive operation. Their widespread implementation and development led to concepts such as staged rocketry and the Space Shuttle becoming obsolete.

The EHD lifter drive is most often used to generate a cushion of air beneath the vehicle it is mounted on, allowing it to "float" in the air. Despite appearances, it is not in fact "anti-gravity", due to the fact that it produces thrust. Its primary application is to carry a UNSC starship or fighter to an altitude where the escape velocity is low, thus allowing the starship to escape the planet's gravity well without the need for titanic amounts of fuel like 20th Century chemical rockets, or incredibly expensive space elevators. However, due to power requirements, the largest vessel that can practically carry an EHD lifter is the Commonwealth-class Frigate. The drive is typically built into vehicles where wings or other methods of producing lift would be impractical, such as on Frigates, which spend most of their time in space, where wings are unnecessary, but may be called to support ground operations in-atmosphere.

Another example is the A-50 Vulture attack fighter, which is the smallest aircraft design to use an EHD lifter, and was designed to be geared towards delivering the maximum amount of damage possible to its target to the extent that wings we deemed to be superfluous, and so the Vulture is only kept in the air by a miniturised lifter drive, powered by an incredibly compact fission reactor. Both of these factors result in the aircraft's great cost.