# Can you use magnets to travel through space?

My thought process is that there is very little friction in space minus gravitational pull. Which could be a good thing if you wanted to go faster or slow down. The question is, is it possible to have a stong electo-magnet and grab onto the magnetic field of a random mass and use it to coast? Or to push away from the magnetic field of an object that is closer given that its gravity doesn’t pull you in?

• You can use magnets to do work (in the physics sense of the word), so, yes, you can use magnets for space travel. However, magnetic force (just like electrical and gravitational force) decreases with distance squared, so I'm not sure this is better than any other means of propulsion. – barrycarter Jun 13 '18 at 15:57
• @barrycarter: Not even squared. If you use a permanent magnet to pull against non-magnetized ferromagnetic metal, the force drops with 7th power of the distance. – SF. Jun 13 '18 at 16:03
• Here's a link on a few of the things in the works for EM drives: nasaspaceflight.com/2015/04/… – Magic Octopus Urn Jun 13 '18 at 16:11
• Possibly related: Can magnets be used to launch spacecraft? – Dan Pichelman Jun 13 '18 at 16:35
• @Magic Octopus Urn: ...yeah, which is a good sign that it doesn't work. A rather more up to date article: arstechnica.com/science/2018/05/… – Christopher James Huff Jun 13 '18 at 21:35

So the short answer here is yes you could. However, there's not a justifiable advantage to using this. To propel yourself, you would constantly need an incredibly strong magnetic object near you. Now, electromagnetic forces are significantly stronger than gravity, but the extent of positive or negatively charged objects are relatively scarce. Additionally, the magnetic orientation of objects is also incredibly weak in general. Earth's magnetic field is 25-65 µT. To put that in perspective, a fridge magnet is about 1.5 mT and an MRI machine is about 1.5 T. This means that any force you could generate would be relatively small in comparison to the conventional Liquid Hydrogen and Liquid Oxygen reaction used. I can try to get the energy numbers if you need them, but I don't necessarily know how to go about calculating it properly. Regardless, the strength is likely 4 or 5 orders of magnitude ($10^4$ or $10^5$ times) weaker than conventional thrust methods.