Wednesday, March 25, 2015

Project Orion: the good, the bad and the ugly

Project Orion was a study of a spacecraft intended to be directly propelled by a series of explosions of atomic bombs behind the craft (nuclear pulse propulsion). Early versions of this vehicle were proposed to take off from the ground with significant associated nuclear fallout; later versions were presented for use only in space.

Key components of the Orion drive
The Orion concept offered high thrust and high specific impulse, or propellant efficiency, at the same time. The unprecedented extreme power requirements for doing so would be met by nuclear explosions, of such power relative to the vehicle's mass as to be survived only by using external detonations without attempting to contain them in internal structures. As a qualitative comparison, traditional chemical rockets—such as the Saturn V that took the Apollo program to the Moon—produce high thrust with low specific impulse, whereas electric ion engines produce a small amount of thrust very efficiently.

Orion would have offered performance greater than the most advanced conventional or nuclear rocket engines then under consideration. Supporters of Project Orion felt that it had potential for cheap interplanetary travel, but it lost political approval over concerns with fallout from its propulsion.

Artist's conception of an Orion drive powered spacecraft
But the main unsolved problem for a launch from the surface of the Earth was thought to be nuclear fallout. Any explosions within the magnetosphere would carry fissionables back to earth unless the spaceship was launched from a polar region, possibly on a barge in the higher regions of the Arctic. An initial launching explosion of conventional high explosive would significantly reduce fallout, subsequent detonations would be in the air and therefore much cleaner. Antarctica is not viable and would require legal changes as the continent is presently an international wildlife preserve.

Freeman Dyson, group leader on the project, estimated back in the 1960s that with conventional nuclear weapons each launch would statistically cause on average between 0.1 and 1 fatal cancers from the fallout.

No comments:

Post a Comment