Free Astronomy Magazine January-February 2015

on 31 October of this year. That day, at 9:20 a.m. California time, SpaceShipTwo took to the skies attached to its mother ship, White- KnightTwo (WK2), a huge twin-fuselage, four-engine jet plane whose task is to carry the spaceplane to high altitude, before re- leasing it to continue the journey under its own means. At 10:10 a.m., in having White- KnightTwo reached the altitude of 13,700 metres, SpaceShipTwo separated from its car- rier. The flight plan included the firing of its powerful rocket en- gine, an operation suc- cessfully executed on three previous occa- sions, while in all oth- er missions (35 in to- tal) SpaceShipTwo had instead remained attached to WhiteKnight- Two or simply glided back to Earth. The only difference compared to previous in-flight engine ignitions was the use of a new ther- moplastic polyamide-based propellant (something similar to nylon), whereas Scaled Composites and Virgin Galactic had previous- ly utilized hydroxyl- terminated polybuta- diene (HTPB), a rub- bery material similar to that employed in the manufacture of tires and regularly used by space agen- cies as a binder for rockets fuels. A few seconds after the sep- aration from White- KnightTwo and rocket engine ignition, Space- ShipTwo broke apart other pilot, Mi- chael Alsbury (pictured right), remains trapped inside the cockpit and crashes to the ground. [Reuters/AP/Ken- neth Brown, Vir- gin Galactic]