- - 

*. LEWIS 

RESEARCH 

center 

21000 BROOKPARK ROAD CLEVELAND. OHIO 44135 

PUBLIC INFORMATION OFFICE 

PHONE - (AREA CODE 216) 433-4000 EXT. 415 

FOR RJ3LF;ASE: WEDNESDAY 

September 16, 1970 

Release 70-47 

Hugh W. Harris 

(res : 932-3966 ) 

CLEVELAND, Ohio, September 16 -- NASA's Lewis Research Center here 

will be honored in Chicago today for the "development of one of the 100 

most significant technical products of the year." 

The award is being presented for the electron bombardment ion thruster, \ 

a type of electric rocket engine, invented by Harold R. Kaufman, Assistant 

Chief of the Electromagnetic Propulsion Division at Lewjs. 

Winners are selected by a panel of some of the country's best known 

scientists and engineers including a nobel prize laureate. The IR-100 

awards are sponsored by Industrial Research Inc. of Beverly Shores, Indiana. 

Lewis has been honored four times in previous years since first entering 

the competition in 1966. The winners are selected by a panel of leading 

scientists and engineers. 

- more - 

I I 1 1- 1 
-2- 

There are two electron bombardment ion thrusters presently on a 

spacecraft orbiting the Earth to demonstrate the engine's ability to 

function reliably for long periods of time in space. The spacecraft, 

called SERT 13 for Space Electric Rocket Test, was launched February 3 of 

this year. The first engine operated continuously for 3,785 hours, a little 

more than five months. The second engine has been operated for more than 

1,000 hours now and it is hoped it will meet the objective of continuous 

operation for six months in space. 

In the future the ion thrusters may be used to position Earth-orbiting 

satellites or as a primary propulsion system to propel spacecraft to distant 

planets . 

Despite its name an electron bombardment ion thruster is a relatively 

simple device. In the engine, liquid mercury is heated until it vaporizes. 

The vapor then passes into a chamber where electrons bombard it separating 

the mercury atoms into electrons and positively charged ions. The resulting 

ions are then attracted rearward by a negatively charged electric field and 

stream out of the engine at very high speeds to produce thrust. After the 

ions leave the engine they are neutralized by a stream of electrons to 

prevent them from being attracted back to the spacecraft. 

Ion thrusters produce only tiny amounts of thrust. The SERT I1 engines 

for instance produce six one thousandths of a pound. However, the ion 

thruster is 10 times more effective in producing thrust for each pound of 

propellant than either chemical or nuclear rocket engines. This means that 

a greater portion of a spacecraft powered by an electron bombardment thruster 

can be devoted to payload. 

- more - 
-3- 

Unlike chemical rocket engines, ion thrusters cannot operate in the 

atmosphere because the air molecules would get in the way of the ions and 

cause electrical arcing in the engines. Since they operate only in the 

vacuum of space they could be used on spacecraft, satellites and upper 

stages of launch vehicles. 

The development of the electron bombardment ion engine has spanned 

many years. Initial studies started back in the 1950's at Lewis. By 1964 

the first space test was conducted on a suborbital flight which proved 

this type of thruster would work and produce useful thrust in space. The 

SERT I1 orbital flight of this year is proving the thruster is ready for 

application to a wide variety of space missions. 

##