A Mach 10 (ten times the speed of sound) test of a scramjet took place in Australia, where a rocket carried the scramjet into near space, then ignited the scramjet to return to earth. Scramjets are special jet engines that work at very high speeds and at high altitudes, and research has continued on them for decades with mixed success. A successful and reliable scramjet design would allow travel between London and Sydney, Australia in as little as two hours.