Cygnus CRS Orb-3 S. S. Deke Slayton

An AJ-26 first-stage engine — a refurbished Soviet-era NK-33 — failed six seconds after liftoff. The vehicle fell back onto Pad 0A at Wallops and exploded, destroying the pad and the cargo, which included Planetary Resources's Arkyd 3 asteroid-prospecting demonstrator. The failure ended the AJ-26 era of Antares; Orbital ATK switched the next-generation booster to factory-new Russian RD-181 engines and bought Atlas V flights to bridge the gap in Cygnus deliveries.