Originally posted by bikingviking
I thought it sounded interesting. Googled for 5 min and this is what I found. I did not read them proberly (not the time for doing so). If only someone, could explain what it is about...?? Thay would make me a happy person! I am a quite curious person.
http://space.skyrocket.de/doc_sdat/artemis.htm ...[text shortened]... w/area/index.cfm?fareaid=26
The interesting thing about ion propulsion is the propellant usage doesn't change much as compared to a chemical rocket, where if you want more thrust and you are already using the best chemicals, like H2 and O2, the only way you get more thrust is to burn more H2 and O2 per unit time, so more flow and shorter operating times.
With ion rockets, you get more thrust with basically the same amount of propellant flow by using more energy to boost the exhaust velocity of the propellant.
That works even at relativistic velocities, because as you get closer to c the propellant gains mass and therefore kinetic energy. Of course today's technology isn't anywhere close to c as far as exhaust velocity goes but that is the potential.
There is a more advanced version called Vasimir that would get folks to Mars in about 1 month but requires the use of nuclear power, that craft wants 200 megawatts to do the job.
I calculated for 100% perfect power in vs acceleration v mass that 32 horsepower can accelerate 550 pounds at 1 G.
Call it 25 Kw for 550 Lbs @ 1 g, so round it off to 100 Kw for one ton at 1 g.
So 100 mw used 100% could accelerate 1000 tons at 1 g, so 200 mw could accelerate 2000 tons to 1 g.
Even with Vasimir, it is not anywhere like those kind of numbers because the Vasimir plus living quarters are being accel'd at 0.05 g which is enough to get you to Mars in a month. That would be about 2 weeks of acceleration and 2 weeks of deceleration so you reach Mars being at the same relative velocity so you can go into orbit or land 'easily'. Not sure how many tons the whole Vasimir design weighs so can't figure a good efficiency rating of power in vs acceleration out. 200 megawatts is about 280,000 hp which on a boat is more than enough to make an aircraft carrier go 60 Kph and carriers are something like 100,000 tons so trucks on land and boats in the water are much more efficient in terms of how efficiently they convert electrical or chemical energy into kinetic energy but in space you don't get the benefit of a large body of water to thrust against or flat land for a truck. You waste an extreme amount of energy just heating or accelerating a propellant to get thrust.