One big note up front! Electric propulsion engines are usually not specific impulse limited!
Your power source mass dwarfs the reaction mass ("fuel") really quickly.
Basically, for equivalent thrust, with twice the specific impulse you require half the fuel but double the power.
So often with electric propulsion you get a better, lower spacecraft mass by using lower specific impulse! This means more reaction mass but smaller solar panels / power electronics.
That's why things like hall thrusters are used, with ISP around 1000s compared to 3000 s gridded ion engines.
Maybe for a Venus or Mercury mission where you have plenty of power and need large delta vees...
That just what I was going to say, but probably put better. Another important metric for electric propulsion is how reliable they are - that is how long you can run them before they burn out. The fact that they're eroding the cathode intentionally might mean this form of propulsion could do well on that metric but only testing will tell.
What is great is they can use other reaction mass than Xenon, which is very rare. And if it's a solid right in the electrode, it's potentially very easy to store.
Probably limits total mass though so maybe use it for very low acceleration missions where you can use the high isp. Like stationkeeping indeed.
In case it wasn't clear, specific impulse is more or less equal to fuel efficiency for spacecrafts (higher is better).
My experience playing Kerbal Space Program, if accurate, suggests that such an engine is more effective for longer term missions, because the increased SI comes at a cost of lower max thrust (I.e. it takes longer to accelerate); I suspect this is not very accurate IRL as all our missions take a very long time so this problem may be irrelevant. Also looking below it seems such an engine is limited by electric power (solar panel/battery).
Hence this leads me to believe this type of engine allows us to extend the range of our missions but at the cost of longer mission durations.
KSP's ion engines are WAY overpowered to make for better gameplay.IRL thurst is lower by orders of magnitude.
If we are talking about probes in the solar system, then the mission durations are already long to begin with. Instead of firing a conventional hydrazine-based thruster for a few minutes, we'll fire an ion engine for months. But, if it takes years to get where you are going, who cares?
There are things we can't do yet, such as orbital insertions, with ion engines. In these cases, conventional engines are better.
Plus, as real life ion engines have burn times on the order of years, and as KSP can't do (adequate) time acceleration while the engine is running, there's a bit of an incentive to build high-thrust short-burn spacecraft --- I don't really want to have to babysit a burn in real time for six months.
(This also disqualifies solar sails, which is a shame, because I'd love to play with them.)
Sort of. People have figured out a way to simulate constant acceleration while the spacecrafts are "on-rails". I believe the KSPi mod has solar sails. They are not very realistic, but probably good enough for a game.
> There are things we can't do yet, such as orbital insertions, with ion engines.
We can do orbital insertions - if we approach a planet or asteroid with parabolic speed, we need only small change to get to an elliptic orbit, and that orbit can be later shaped as we need.
What we can't do is a launch or landing with bodies with sufficient gravity - like Moon or Vesta. There we don't have time to accelerate.
I read about this earlier this week in the campus newspaper [0] which contains a bit more background information including that the university declined any ownership of the invention. Good for him!
Your power source mass dwarfs the reaction mass ("fuel") really quickly.
Basically, for equivalent thrust, with twice the specific impulse you require half the fuel but double the power.
So often with electric propulsion you get a better, lower spacecraft mass by using lower specific impulse! This means more reaction mass but smaller solar panels / power electronics.
That's why things like hall thrusters are used, with ISP around 1000s compared to 3000 s gridded ion engines.
Maybe for a Venus or Mercury mission where you have plenty of power and need large delta vees...