Boeing Co.'s construction of the largest rocket in NASA's history is projected to cost $8.9 billion — double the initial budget. While taxpayer-funded cost overruns are common in the U.S. military industrial complex, the massive aerospace company is also two years behind schedule — a gap that could widen further, according to an audit by NASA's inspector general.

The company's poor performance on the massive Space Launch System means NASA will likely miss the launch window of December 2019-June 2020 for its planned Exploration Mission-1, the first flight of the SLS and Orion spacecraft, the report said. The rocket and Orion — being built by Lockheed Martin Corp. — are designed as America's new deep-space exploration system, to launch first to the moon and eventually deeper into the solar system. Since the end of the space shuttle era, Americans have had to hitch a ride with Russians to get into space.

As of August, NASA has spent $5.3 billion out of a $6.2 billion budget for the Boeing contract, and the agency said it expects Boeing to reach the contract's value by early 2019 — albeit, without even having delivered the rocket's core stage. Between June 2014 and August of this year, Chicago-based Boeing spent $600 million more than planned on developing Core Stages 1 and 2, and NASA officials confirmed that Boeing spent an additional, unplanned $226 million in the current fiscal year.