Private spaceflight company Orbital Sciences has set a timeline for rocket launches that is too ambitious — and it’s doubtful the company will launch again on time, according to NASA’s inspector general. The space agency's Office of Inspector General (OIG) released a scathing report today criticizing the flight plans of Orbital — the company that, along with SpaceX, holds a contract with NASA to launch cargo to the station. The inspector general analyzed Orbital's strategy for returning to flight after the company's rocket exploded during a routine mission last year.

Orbital has been on hiatus from launching rockets since last October, after the company's Antares rocket blew up during take off at NASA's Wallops Flight Facility in Virginia. It was supposed to be Orbital's third cargo resupply mission for NASA. But a problem with the rocket's engine caused the entire vehicle to ignite seconds after launch. The explosion destroyed Orbital's Cygnus spacecraft, filled with supplies for the station; the Wallops facility also sustained a lot of damage.

Orbital has been on hiatus from launching rockets since last October

Since then, Orbital has been working to replace the engines in its Antares rocket. But replacing a rocket engine isn’t easy — you have to tweak the rocket’s design to incorporate the new engine — and so it’s taken some time. The problem is that Orbital doesn’t have time; it’s under a $1.9 billion contract with NASA to launch five more resupply missions to the station by 2016. So as a temporary solution, Orbital plans to launch its Cygnus cargo craft atop the United Launch Alliance's Atlas V rocket for the next two launches; then it'll use the Antares again. And rather than do five total missions, Orbital will consolidate to four. The first Atlas V launch is scheduled for late 2015, while the first Antares launch is scheduled for March 2016. The company says it'll just add more cargo to each mission to make up for the loss. This should come at no extra cost to NASA, Orbital claims.

But the inspector general isn't particularly happy with all of these changes. The OIG report expresses concern over Orbital's decision to launch the Cygnus on the Atlas V rocket so soon. The Cygnus has never flown on this rocket before, so there may be some unexpected issues with the first flight. Even the smallest miscalculation could cause a failure, and the inspector general argues Orbital hasn’t done enough technical reviews of the Cygnus and Atlas V combination.

The accelerated timeline also leaves out time for doing a flight test of the updated Antares rocket. Overall, the OIG report doesn't think the March flight is feasible and argues that June is more likely. Then there's the decision to drop one of the five planned launches. The report says this limits the flexibility in what supplies can and cannot be sent to the station for each trip.

The accelerated timeline also leaves out time for doing a flight test

The report goes on to admonish NASA's response to the Orbital failure, as well, arguing the space agency could have done more to reduce costs associated with the disaster. It also notes that NASA wound up paying an extra $5 million dollars to repair the Wallops Flight Facility, when that money should have come from insurance claims.

As a result of these findings, the inspector general made a list of recommendations NASA should follow to address the report's concerns. For example, the report called for Orbital to do more reviews of the new Antares rocket before it launches. The inspector general says Bill Gerstenmaier, NASA's associate administrator for human exploration, agreed to follow most of these recommendations. However, Gerstenmaier ignored a recommendation on how NASA could better ensure that insurance claims pay for facility damages, instead of the space agency footing the bill.