Plasma and ionic electric jet engines are even more economical and "swift." In them a stream of charged particles is whisked to high velocities by means of an electromagnetic field, almost as in a charged particle accelerator.

Another factor increasing their thrust is the capacity of the equipment creating the field and speeding up the particles.

Russia's experience in developing and operating power reactors in space is unique. From 1970-1988, Russia launched a total of 32 spacecraft with nuclear propulsion units and thermo-electric converters of 3 kilowatts and 5 kilowatts capacity.

Most of these vehicles performed reconnaissance operations and remained in orbit in an activated state for several months at a time.

By comparison, America had only one such craft, with a SNAP 10A nuclear reactor and a 0.5 kW thermo-electric power converter, which was launched in 1965. It did not survive long, lasting a mere 43 days and is now part of the space junk orbiting Earth.

Then the efforts became pure research and did not resume until 2002.

Russia is also an expert at making the so-called stationary plasma engines, which have a thrust one order of magnitude greater than the traditional chemical ones. Their first space tests were carried out in 1972 on the Russian Meteor weather satellite, and the regular operation of serially made vehicles began in 1982 on geostationary satellites to correct their orbits.

At present, practically all countries, including the leading space powers, are making active use of various types of Russian-designed electric jet engines. The power of these engines is such that they can adjust the orbit both in longitude and inclination.

Additionally, they can make inter-orbital jumps along energetically optimal multi-revolution trajectories. For example, they can move from a low orbit to a geostationary one and they also serve as a vehicle for interplanetary travel.

In preparing the manned expedition to Mars, the developers considered many options: liquid rocket engines burning oxygen and hydrogen; nuclear rocket engines with liquid hydrogen as a working agent; and a nuclear and a solar installation to power electric jet engines.

For the core equipment they selected the solar-powered unit with thin-film elements based on amorphous silicon.

As a prospective alternative, consideration is also being given to a nuclear power unit as it is developed to reach an operating stage. The main problem in using such units is nuclear and radiation safety during every stage of operation, including emergencies, which requires further research.

Preoccupied with the nuts and bolts of the interplanetary ship and its propulsion, people tend to forget about many other problems, including physiological and psychological ones.

These and other problems must be addressed before humans set out on an interplanetary journey, but that is the subject for a separate discussion.

(Yury Zaitsev is an academic adviser at the Academy of Engineering Sciences. This article is reprinted by permission of RIA Novosti. The opinions expressed in this article are the author's and do not necessarily represent those of RIA Novosti.)

(United Press International's "Outside View" commentaries are written by outside contributors who specialize in a variety of important issues. The views expressed do not necessarily reflect those of United Press International. In the interests of creating an open forum, original submissions are invited.)

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