Some ion trajectories involve constant
low acceleration. It really adds up time. You accelerate halfway there, then decelerate the rest of the way.
The dawn spacecraft mission to ceres has 48,000+ hours of gentle acceleration under ion propulsion. That’s 5.5 years of firing. But it gets over 38,620 km/h of delta-v (acceleration).
9 months is a typical direct transfer, using a traditional rocket engine whose thrust is so high you can basically treat it as infinite: accelerate up to your transfer speed in a few minutes and coast until you need to slow down in a similarly negligible amount of time. You need to set a lot of gas on fire in those few minutes, though. Electric propulsion is so low thrust that it can’t put you on that kind of direct trajectory in one go, so the trip is more of a slow spiral around the sun with continuous thrust the whole way. The tradeoff for everything taking forever is unbelievable fuel savings, which is a surprisingly common occurrence in space travel.
Some ion trajectories involve constant low acceleration. It really adds up time. You accelerate halfway there, then decelerate the rest of the way.
The dawn spacecraft mission to ceres has 48,000+ hours of gentle acceleration under ion propulsion. That’s 5.5 years of firing. But it gets over 38,620 km/h of delta-v (acceleration).
https://www.jpl.nasa.gov/news/nasas-dawn-spacecraft-fires-past-record-for-speed-change/
That’s to Ceres, Mars is only 9 months, so how do we get from 9 months to 23k hours?
9 months is a typical direct transfer, using a traditional rocket engine whose thrust is so high you can basically treat it as infinite: accelerate up to your transfer speed in a few minutes and coast until you need to slow down in a similarly negligible amount of time. You need to set a lot of gas on fire in those few minutes, though. Electric propulsion is so low thrust that it can’t put you on that kind of direct trajectory in one go, so the trip is more of a slow spiral around the sun with continuous thrust the whole way. The tradeoff for everything taking forever is unbelievable fuel savings, which is a surprisingly common occurrence in space travel.