WASHINGTON — A Pegasus XL launched a mission to reboost a NASA astrophysics spacecraft on what may be the final flight of that rocket. A Northrop Grumman Pegasus XL rocket was deployed from its L-1011 carrier aircraft at 4:36 a.m. Eastern on July 3, after three days of delays caused by weather and technical issues. The rocket placed its payload, the 425-kilogram Link spacecraft from Katalyst Space...