Nuclear Powered Ion Plasma Engines

I don't remember enough to quote it exactly. But it was something about using the engines in a manner unauthorized (out of protocol) while still in a planetary atmosphere. This order was bizarre probably because of the present condition of the engines nuclear reactor cores. The ship was "at rest" and the engines weren't yet critical, but the emergency situation required the crew to "hot start" the reactor cores and achieve hypercritical status in a hurry, instead of taking the normal amount of time. Dangerous because it required the engines to suddenly operate beyond their rated power without first having overcome inertia. It was certain that the engines; as well as the attach points of the engines, would be over-stressed. Very uncool if they ever want to use the engines again. The two pilots reacted to the command out of training or just habit because it was unorthodox. But were resigned to the fact that it was the last time the engines would be needed, as it was a suicide sortie.

"..But were resigned to the fact that it was the last time the engines would be needed, as it was a suicide sortie..." Shaw implying there may be nothing to go home to created an immediate and fatal command to be given..and executed.. How the engines might react to such a short warm up,,but being inspired by the Juggernaut take off....was not a concern for .Janek it was a job that must be done.. Anything to keep the Engineer's ship to get to earth...and keep all of the destructive 'goo' on the moon..

Don't quote me 100% on this but it was something quite close to "power up the ion drive". Today's ion drives are all the range in deep space exploration but they are useless for delivering powerful thrust (they deliver continuous but feeble amounts of thrust for months on end). However, that is not to say that in 80 years time, such drives won't be continuous [i]and[/i] powerful. The implication is that the ion drive was disabled when they were landing (since they were in atmosphere). So, turning it on to ram the juggernaut would be to give them an extra kick, I presume.

I did not realize current ion drives were low thrust. I also didn't think about the reactors being in standby and warming them up so the ship could ram the Juggernaut at full thrust seems like similar to sitting on a ticking bomb. Good thing Janek and his crew were a good team since a second's rebellion would've probably lost them the chance. Great info, folks!

Update: The actual instruction given is "Warm up the ion propulsion". It was indeed fortunate that the captain and his pilots were willing to give up their lives so easily, and with so little time to come to a decision. Some people regard that as being unbelievable, but Janek is a very bright guy with high moral scruples. The banter that followed after the decision was made is called 'gallows humour'.

THe thing about the nJanek charactor he just sees to be so cautious during other aspects of the movie. He was certainly motivated to take out the Juggernaut and his crew when he knew the time was right. I sort of wonder if he felt his crew would stay with him to the end.. If I was in Janek's shoes I mught have had a bit concern for Chance and Revel survival even if it was on this moon. Perhaps everybody but Vickers could see that this was the time to act and they had little option. Vickers trying to escape her destruction in the Prometheus just sort delayed her fate to where she was destroyed by theother spaceship , the Juggernaut

".. 'gallows humour'." I just viewed the Gallows humor you mentioned and it sort of fit the scene. What I did notice during this viewing is that Janek actually smiles when 'Your a shit pilot.." is spoken. He has quite a grin when he knows his crew will stay with him til the end.

Ion propulsion is a weird choice for turning one into a bullet, yeah. As mentioned, ion drives are very low thrust. The up-side, and why they're very popular for deep-space, is that they have very high exhaust velocity. In general, the useful power of a (rocket)ship's engine will be split between providing thrust (which is good for take-off from a planet) and exhaust velocity (which is good for economically achieving desired orbits in deep space). A more plausible choice to turn the Prometheus into a bullet is nuclear propulsion. But really, when you've got magical FTL tachyonic engines, who cares about minor tech quibbles.