![The HL-20 undergoing testing for forced oscillation in pitch, 1989.](https://appel.nasa.gov/wp-content/uploads/2011/11/561703main_L-89-9450_946x710-670x380.jpg)
By Jim Hodges The first time Mark Sirangelo saw the model on which Sierra Nevada’s Dream Chaser is based, in 2005, it was in the corner of a huge hangar at NASA’s Langley Research Center in Hampton, Virginia. “It was covered with dust and other things I’d probably better not mention,” said Sirangelo, who […]