The U.S. Air Force is considering upgrading just about everything on its fleet of 500 Minuteman 3 intercontinental ballistic missiles to keep them in play beyond 2020, including replacing propellants and improving guidance systems, said Lt. Gen. Frank Klotz, acting commander of Air Force Space Command.

Already well under way is a refurbishment program designed to sustain the viability of the fleet until 2018. This includes such things as replacing propellants and systems with an eye toward sustaining existing capabilities.

But the program also includes options to introduce new technologies to enhance the capability and maintainability of the Minuteman fleet, according to industry sources. It is this enhancement effort, which would be carried out incrementally as new technologies become available, that the Air Force now is contemplating, sources said.

Speaking at a briefing April 6 during the 22nd National Space Symposium here, Klotz said Space Command is looking for ways to keep the Minuteman fleet viable after 2020 . “There’s still a lot of resonant capability there,” he said. It would be better, he added, to try to build on the existing fleet instead of developing a brand-new one.

The Air Force also is considering new applications for ICBMs that go beyond the traditional nuclear-deterrent role. These include arming some of the missiles with conventional warheads and using them to strike distant targets more quickly than would be possible with aircraft.

Space Command still is briefing senior defense officials on the ICBM upgrade plan, which was based on a review of the Minuteman fleet finished this past autumn , Klotz said.

The current Minuteman 3 refurbishment program is geared toward sustaining existing capabilities, industry sources said. For example, Klotz noted, the propellant bonding in the missile motors can weaken with age.

The missile-motor casings now are being washed out and refilled with propellant that has the same chemical composition as the original fuel, the industry sources said. For the upgrade program, new propellant mixes could be introduced that would give the missiles more speed, range, accuracy and flexibility, they said.

The enhancements also would extend to the missiles’ guidance and other systems, industry sources said.

Technological improvements could help in more mundane areas like security, Klotz said.

He noted that the Montana missile field is 60,000 square kilometers — nearly three times the size of the state of New Jersey. “Security is now manpower-intensive,” he said. “High-tech surveillance could be used.”

Warren Ferster contributed to this report from Washington. Comments: