DETROIT -- The auto industry, fed up with slow progress toward finding out why some air bags explode with too much force, has hired a Virginia rocket science company to investigate the matter.

Ten automakers whose vehicles have been recalled because of problems with Takata Corp. air bags said Thursday they have jointly hired Orbital ATK to figure out the problem. The suburban Washington, D.C., company makes rocket propulsion systems, small arms ammunition, warhead fuses and missile controls.

The companies also named David Kelly, a former acting administrator of the National Highway Traffic Safety Administration, as project manager for the investigation.

Air bags inflators made by Takata of Japan can explode with too much force, sending shrapnel into car and truck cabins. At least six people have been killed and 64 injured due to the problems, which surfaced a decade ago. So far, about 17 million cars and trucks have been recalled in the U.S. and 22 million worldwide to replace the inflators, but Takata has been unable to pinpoint the cause. The company has known about the problems since at least 2004.

Takata uses ammonium nitrate to create a small explosion that quickly inflates its air bags. But government investigators say the chemical can burn faster than designed if exposed to prolonged airborne moisture. That can cause it to blow apart a metal canister meant to contain the explosion. Automakers, Takata and the government all want to find out just how much humidity and time it takes to cause the problem, both of which are unknown.

Orbital ATK has the ability to quickly simulate the impact of humidity on the propellant over long periods of time, which is key to finding out the cause, Kelly said in an interview. The company will test air bag inflators that were taken from cars that have been repaired under recalls.

"The Orbital team has a tremendous amount of experience in being able to test that and being able to look at burn rates on a large scale," he said.

Long-term stability of air bag propellant is important because cars are staying on the road for 10 or 15 years, much longer than in the past, Kelly said.

He wouldn't estimate how long it might take to find a cause. "We don't want to prejudge that process. It is much more important for us to get the answer right than to get the answer back," Kelly said.

Orbital ATK will share data with Takata and government safety investigators. Once a cause is found, it will be disclosed to all stakeholders and the public, Kelly said.

The automakers, led by Toyota, include BMW, Fiat Chrysler, Ford, General Motors, Honda, Mazda, Mitsubishi, Nissan and Subaru. Several said privately they hired Orbital to speed up the investigation.

In a statement, Takata said welcomes Orbital and Kelly and will work with them and NHTSA on the investigation. The company said it has been in contact with automakers and will support their investigation by sharing results of its own testing.

Takata is being fined $14,000 per day by NHTSA for allegedly failing to co-operate in the government's probe of the problem, an accusation that Takata denies. Fines began Feb. 20 and have grown to $98,000 so far.