This is a sample of spent fuel burned by the rocket-powered SpaceShipOne during its ascent. The hybrid engine used both solid (rubber) and liquid (nitrous oxide) propellants. Both are relatively inexpensive and easy to handle, which makes them a good candidate for economical commercial spaceflight. SpaceShipOne won the $10 million Ansari X Prize in 2004 for repeated flights in a privately developed reusable spacecraft. It was designed to be a simple, robust, and reliable vehicle to make space travel and tourism affordable. The Museum removed this fuel byproduct upon receiving the spacecraft in 2005.