lecture06: autonomous problems: the brachystochrone
http://en.wikipedia.org/wiki/Nose_cone_design
http://www.info-central.org/?article=125
http://mcfisher.0catch.com/other/mach1/mach1.htm
http://www.if.sc.usp.br/~projetosulfos/artigos/NoseCone_EQN2.PDF