UPDATE 4-Northrop Grumman to buy missile maker Orbital for $7.8 bln By: Reuters: Company News September 18, 2017 at 16:25 PM EDT * Deal could face regulatory scrutiny - analyst (Adds Aerojet share price; M&A data) Read More >> Related Stocks: Aerojet Rocketdyne Holdings Northrop Grumman Orbital ATK, Inc. Common Stock Rockwell Collins United Technologies