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when we put two magnets together they push each other apart. So why can't we use the same concept with the magnetic field and a man made magnet?

David Derrico
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    The force between magnets drops off very rapidly with distance. How do you propose to apply the magnets? – Russell Borogove Aug 24 '17 at 20:34
  • @RussellBorogove point is good. One a pair of magnets are separated by a few times their widths (not lengths) the strength of the repulsion is a small fraction of what you feel holding them together. In order to get a valuable payload to orbital speed safely, you need to accelerate for a long time over a long distance. – uhoh Aug 24 '17 at 20:39
  • If one rocket propelled magnet pushes a second magnet, second magnet will reach orbital speed without touching the rocket. – user721108 Aug 25 '17 at 00:02
  • You are basically describing the idea of a mass driver. Built big enough it would be a good idea off an airless body. Slamming the spacecraft through the lower atmosphere at orbital velocity, though, is unsurvivable with present tech (for the launcher as well as the spacecraft. It would be obliterated by the shock waves.) – Loren Pechtel Aug 25 '17 at 01:58
  • @qqjkztd Second magnet will slow down the first exactly as if an equivalent mass was directly attached to the first. a = f/M and you don't get something for nothing. – Russell Borogove Aug 25 '17 at 02:37
  • @qqjkztd It's the same problem as trying to fly by pulling on your own bootstraps. You're just replacing tensile strength of bootstraps with magnetic repulsion, which changes nothing. – SF. Aug 25 '17 at 06:33
  • What CAN be done is pushing against magnetic field of Earth. But to produce force, and not just torque, you need one pole of the magnet attached to the craft, and the other either out of Earth magnetic field (making the craft impossibly big) or not attached and left behind (which poses a very hard scientific and engineering challenge.) – SF. Aug 25 '17 at 06:47

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