Question: What is the best propulsion to get humans to mars

Abbie Hutty answered on 8 Mar 2016:

The ExoMars mission uses chemical propulsion – two liquid propellants which are combined together – one main fuel and an oxidizer. This is known as a bi-propellant engine. https://en.wikipedia.org/wiki/Liquid-propellant_rocket
This is a well-understood, highly-developed technology, and is quite easy to use for a mission to Mars as the amount of fuel required is not too difficult to take along in tanks, so is a good match for our mission. You squirt your fuel and oxidizer together, they combust, and you get oomph out the back of your thrusters. You get a good oomph so you get up to speed quickly, and it is easy to control the thrust by controlling the amount of fuel you squirt in in the first place.

There are loads of new technologies coming through, and by the time we’re ready to send humans they might be preferable, depending on the scope of the mission, for example ion thrusters, electric propulsion systems and electrostatic engines. They are able to get you further with less fuel, but generally take longer to get you up to speed as you get less “oomph”. So considering Mars isn’t that far away (in celestial terms), and that if we’re going to mars with humans and we probably want a minimal journey time, we might just stick with chemical propulsion.