Pictured is a U.S. Air Force photo, posted by Northrop Grumman, of an initial mass model sled test of Sentinel's guidance and control hardware.

The Government Accountability Office's (GAO) latest report of major defense acquisition programs found that while several nuclear modernization efforts continue to advance through development and testing, the Sentinel ICBM program remains burdened by significant cost, schedule and design challenges. In its annual review of weapon systems released last week, GAO said the Air Force’s Sentinel continues to undergo restructuring following the program's critical Nunn-McCurdy cost breach. The government watchdog cautioned that the program still faces considerable uncertainty, citing ongoing design…