# When did ion propulsion first see some serious development efforts?

In the video below at about 01:35 Dr. Marc D. Rayman, Chief Propulsion Engineer, NASA JPL mentions that the first time he had heard about ion propulsion was on the Star Trek TOS third season premiere episode Spock's Brain which was first aired on 20-Dec-1968.

In reality, when did ion propulsion first see some serious development efforts? Where and when were the first experimental and first sound theoretical investigations of propulsion based ion electrostatic accelerations of ions as a reaction mass for propulsion in space?

I'm not sure if it's the first use of ion propulsion, but it's the first I know - and it's possible to argue it's a yet different propulsion because the principles differ from most ion engines used nowadays...

Zond 2 launched on 30th November 1964, used six Pulsed Plasma Thruster motors for its attitude control.

Unlike typical modern ion engines, where electric field between two statically charged grids is accelerating ionized propellant, similarly to cathode ray tube, PPT uses Lorentz force for acceleration, acting on principles similar to a railgun, with the slug completing the circuit replaced by a puff of ionized plasma produced by ablating inert solid propellant. It's still ionized gas propelled with electromagnetic force, so it arguably fits the definition of a ion engine, and to my knowledge, it was the first application of such propulsion.

• Am I correct that this is NOT thermalized? – ikrase May 2 at 5:12
• @ikrase what do you mean by that? – SF. May 2 at 7:42
• It works by driving (relatively) "cold" matter, not by expanding superheated gas like VASIMR and arcjets. – ikrase May 2 at 7:48
• @ikrase Arguably or very relatively - the material is obtained through evaporating silicon off an inert silicon stick using electric arc, and subsequent electric current through the plasma surely heats it a lot, but it's not thermal expansion that is the driving force, the high temperature is just the prerequisite to start the acceleration action, and side effect of it acting. In particular at no point does chamber pressure reach any meaningful values. – SF. May 2 at 8:03

The first flown Ion Engine from the United States was the Deep Space One testbed mission, which was one of the Better-Faster-Cheaper missions of the late 1990s. However, the technology was around for quite a bit longer than that.

The basic design, the Hall Effect thruster, was studied by both the US and the USSR in the 1960s, and the first public mention being made by the US in the early 1960s. The first Soviet mission to use one was a Meteor spacecraft in 1971. The Soviets continued to lead the effort until the end of the cold war, at which time the technology found its way to the West.