This saves valuable chemicalpropellant and extends mission lifetime.
这样既可以节省珍贵的化学燃料，又可以延长航天器的寿命。
2
The chemicalpropellant is packed inside the tool which is lowered on wireline.
化学推进剂被装在工具内，工具用钢丝绳下入井内。
3
Whereas chemical rockets waste too much propellant to reach a net change in spacecraft velocity, electric thrusters can do exactly the same mission using just a small fraction of the propellant.