Specific impulse (usually abbreviated as Isp) is a physical quantity defined as the ratio of change in momentum (impulse) to the mass used, usually fuel. It typically uses units of metres per second (a SI unit) or feet per second (in imperial units). It is equivalent to thrust (a force, in newtons or pounds) per mass flow rate (in kg/s or lbm/s). - WikipediaCurrent ion thrusters (of which this is just a variant) provide only extremely low thrust (think: perfume atomizer or, at best, underarm deodorant spray!) - but can at least do so for a long time, and - get this! - with very good efficiency (= consumption of power to achieve acceleration).
The high efficiency is the selling point! They can't be used to blast off a celestial body (like the Earth or Moon), because their thrust is so weak - but once in orbit (or on an interplanetary trajectory), that gentle thrust can be applied for weeks / months.
For unmanned probes, that's ideal! In the case of crewed missions, you can't afford to wait hours in order to boost speed by a lousy couple of m/s - even if it's 10X more efficient that chemical fuels.
The lithium thruster discussed here is supposedly 25X more-powerful than previous ion thrusters. Probably still not powerful enough for a crewed Earth-Mars mission - but they are hopeful that it can be further improved.
Regards,
Ok... lotta words and effort in posting. but I will ask the same question yet again....
Is this system efficient enough the burn 23,000 hour-2.6 years-with the amount of fuel that can fit in the proposed Mars Mission Rocket??
The article clearly says they need 23,000 hours of burn time. I cannot see how this is even possible/needed. they are not in constant thrust the entire way to and from. there is acceleration on the start, and thrust to slow down on arrival and maneuvering.
or am I reading that wrong and the 23,000 hours is testing time??