2 ms·
We already have a myriad of high specific impulse electric thruster technologies, some of them have operated for decades in space and are standard equipment use
by Gravityloss 6y ago
We already have a myriad of high specific impulse electric thruster technologies, some of them have operated for decades in space and are standard equipment used on commercial satellites, used since 1997! The exhaust speed ranges from 10 to 40 km/s.
All these technologies are limited by their power source, not by the thruster. That's the actual problem.
If you use higher exhaust velocity, you need less propellant but need more power. After a certain point, power source mass dominates the propellant mass. The total system gets worse with higher exhaust velocity than that.
- Retric 6y agoFor clarification, F=MV but kinetic energy = 1/2 MV^2. So to use 1/Nth the mass you need N times as much velocity. Which that takes 1/N * (N^2) = N times as much energy. Aka 1/100 th the mass = 100 times as much total energy.
- mhandley 6y agoAnd you're probably limited to fission or fusion power sources if you want enough power to achieve high enough thrust for crewed spaceflight with one of these drives. Problem then is getting rid of the waste heat - you'll almost certainly be limited by radiator area.
- Retric 6y agoSolar panels provide a lot of powder for an Earth > Mars trip. You get ~1/2 the sunlight in Mars orbit but it’s still 24/7 365. So your ultra light ~40% efficient panels are averaging something like 350w/m2 * 520 days, which is worth hundreds of pounds of hydrogen + LOX.