A detached electrical connector on the second stage of Rocket Lab’s Electron rocket caused a failure on a July 4 mission that destroyed seven small commercial satellites, but the company said Friday it is on track to resume launching before the end of August. Once the electrical system disconnected in flight, it cut power from the rocket’s battery to the electric turbopumps on the Electron’s second stage Rutherford engine. That caused the engine to switch off prematurely around five-and-a-half minutes after the rocket took off from Rocket Lab’s launch base in New Zealand. The early engine shutdown prevented the rocket...