TAMPA, Fla. — Propulsion problems on four satellites using the same kind of power modules are expected to result in at least $50 million in claims for insurers already facing more than $800 million in losses this year following two major spacecraft failures. According to multiple insurance sources, Yahsat’s Al Yah 3, Avanti Communications’ Hylas 4, and Northrop Grumman’s two Mission Extension Vehicles (MEV-1 and MEV-2) are operating with reduced power to their thrusters following a problem with onboard Power Processing Units (PPUs). The PPUs from Aerojet Rocketdyne provide the electrical power their thrusters need for station-keeping in geostationary orbit...