EHD Thruster stands for Electrohydrodynamic thruster. This is the general and most appropriate term used for high voltage propulsion devices in which, unlike their relative ion thruster family, do not need to carry their own gas supply, although they still require to carry their own electrical power source or generator. Also, unlike related propulsion devices, they require the atmosphere for their operation and cannot operate in space or vacuum.

What is an EHD thruster

An EHD thruster is a propulsion device based on ionic air propulsion, that works without moving parts, uses only electrical energy and is able to fly autonomously and carry additional cargo. The principle of ionic air propulsion with corona generated charged particles has been known as from the earliest days of the discovery of electricity, with references dating back to year 1709 in a book titled 'Physico-Mechanical Experiments on Various Subjects' by F.Hauksbee. The first publicly demonstrated tethered model was developed by Major De Seversky in the form of an Ionocraft. De Severski contributed a lot to its basic physics and its construction variations during the year 1960 and has in fact patented his device on patent no: US3130945 in April 28, 1964. Only electric fields are used in this propulsion method. The basic components of an EHD thruster are two: an air ioniser and an Ion accelerator. The ionocraft and the Lifter form part of this category, but their efficiency is severely limited to less than 1% energy conversion efficiency by the fact that the ioniser and accelerating mechanisms are not independent. Unlike the Lifter, within an EHD thruster, the air gap in its second stage is not restricted or related to the Corona discharge voltage of its ionising stage.

EHD thruster operation

The first stage consists of a powerful air ioniser, which when supplied by high voltage in the kilovolt range, ionises the intake air into ion clouds to be fed 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 along a straight path along the length of the accelerating unit. Movement of the ion clouds can be electronically controlled to increase the effective efficiency. Within this path, the ions travel at a constant drift velocity and multiple impacts occur with the neutral gases present in the accelerating unit, which is open to the atmosphere. In accordance with Newton's Third Law of motion, the thruster will be acted upon an equal and opposite force to the total force exerted by the ions over the neutral air within the second stage. Optionally, the temperature, pressure and gas constituents may be synthesised within the accelarating stage to increase the efficiency of momentum transfer between the charged ions and the neutral air molecules. The charged ions are then neutralised on their exit from the second stage. A well engineered EHD thruster can achieve a high degree of electrical to mechanical conversion efficiency with the correct design parameters.

See also

• Ion thruster
• Hall effect thruster
• Magnetoplasmadynamic thruster
• Spacecraft propulsion
• Hall effect thruster
• Field Emission Electric Propulsion
• Pulsed inductive thruster

External links

• Blaze Labs Research - Introduction to EHD thrusters
• Blaze Labs Research - Why EHD thrusters will not work in a vaccuum
• Blaze Labs Research - Ionocraft mathematical analysis & design solutions (.pdf format, 120kb)
• Plasma propulsion in space