vda - 12/2/2007 8:18 AMSo far almost all Solar System missions were using chemical engines, and frankly, they are far too inefficient for the task. Nine years to Pluto? Come on... Exploring/settling solar system using this technology will take centuries...

meiza - 11/2/2007 2:12 PMIt is not sensible to analyze the propulsion systems with an assumption of "infinite power", when the choice of a propulsion system is rigidly linked to the power source. It's the same as comparing a ferrari and a lorry - either one is useless for the other's job, and you can't say which one is better without any context.

meiza - 12/2/2007 11:49 PMIt's not the ion engine that produces the power. In a sense, it doesn't "have" any power, it only "uses" that 150 kW. It always needs an external power source. The ion engine could rather be seen not as a Cessna engine but as a Cessna propeller.The very real questions are ~always about the power sources and their masses.

vda - 12/2/2007 8:47 AMQuotemeiza - 11/2/2007 2:12 PMIt is not sensible to analyze the propulsion systems with an assumption of "infinite power", when the choice of a propulsion system is rigidly linked to the power source. It's the same as comparing a ferrari and a lorry - either one is useless for the other's job, and you can't say which one is better without any context.Ok, I can rephrase it. I am interested in high-power ion engines, ones which are capable of orbit insertion job. DS1 class engine is clearly far too feeble for that. Ok, so let's presume we have a ~1MW reactor (i.e. a lot of electricity). What type of engine can use that much electric current? What are expected thrust figures?Of course this info will not be applicable to crafts with 10kW power source, I understand that.

When we did our 500 kW Hall thruster system (about 21-25 newtons) the dry mass was right at 10 metric tons.

meiza - 11/2/2007 4:30 PMIt depends on the mass of the 1 MW (?) reactor and the power conversion equipment plus the required mission acceleration and delta vee and the size of the required payload. You could bolt on a lots of ion engines etc...

... we use MPD. ISP is ten times lower, so exhaust mass should go up x100 in order to use the same amount of energy.Reactor power: 1MWReactor mass: ~500kgExhaust, m/s: 100000 (ISP ~10000)Exhaust, kg per sec: 0.0002 (200 mg)Thrust: 20 kg*m/s^2 (20N)Acceleration: 0.04 m/s (40mm/s)T/W ratio: 0.004Above numbers are incorrect because (a) conversion efficiency is not taken into account and (b) MPD thruster's own mass is assumed to be zero. I suppose I should divide those numbers at least by four in order to compare it to the first set of numbers (remembering that realistic numbers for both "engines" are even lower).So far it doesn't look too bad - hey, 1 centimeter/second acceleration is not so feeble. In one month it gives you ~25 km/s delta-v (and will consume 500 kg of propellant, so... less than 25km/s , but still...).Where am I wrong? How much lower are "realistic" numbers?