If someone wanted to understand the advantages and disadvantages of ion thruster and chemical propulsion, they would have to have a fundamental understanding of a high school physics concept—acceleration.
On a short distance scale, because of the huge thrust produced by chemical propulsion, spacecraft could reach a very high speed in a short period of time, thus reducing the overall flight time.
However, if the distance scale was expanded to millions of kilometers or even tens of millions of kilometers, the situation would become drastically different.
Unlike ion thruster propulsion, chemical propulsion could produce a huge thrust in exchange for working medium consumption. However, ion thruster propulsion could reach speeds much higher than chemical rockets due to its continuous acceleration and large specific impulse.
It took the BFR rockets three months to travel to Mars.
