Neodymium Iron Boron Magnets for Launch Sleds

• http://e-magnetsuk.com/neodymium_magnets/neodymium_grades.aspx

• https://en.wikipedia.org/wiki/Rare-earth_magnet

• https://en.wikipedia.org/wiki/Neodymium_magnet

• 1 MGOe = 7958 J/m3

An N52 magnet has a maximum energy product of 50 mega-gauss Oersteds, which is 50*7958 J/m3 or 398 KJ/m³ . the density is 7.5, so that works out to 53 J/kg.

A high strength NIB magnet should be kept below 80C; launch loop magnet sleds should be refrigerated, perhaps to liquid nitrogen temperatures, before use, as they will be heated by hypersonic passage through the thin upper atmosphere. Some grades (N38 EH) can tolerate 200C, but are 36 mega-gauss Oersteds, 38 J/kg.

A reusable launch sled containing one tonne of NIB might be 10 square meters and 1.3 cm thick, 38 KJ.

If the one tonne sled is pushing itself and 5 tonnes of payload with an acceleration of 30 m/s², the total thrust on the sled is 150 KN, or 15 KN/m².

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NiB alternatives

University of Minnesota claims anisotropic Iron Nitride magnets can theoretically produce 134 MGOe, have made 10 MGOe so far

• http://license.umn.edu/technologies/20120016_iron-nitride-permanent-magnet-alternative-to-rare-earth-and-neodymium-magnets

• http://people.ece.umn.edu/~jpwang/