Two small U.S. military satellites are queued up and waiting to ride into space on Minotaur rockets in May, but managers want to make sure the boosters are immune from the glitch that doomed the launch of a NASA science mission in March.

File photo of a Minotaur 4 rocket in Kodiak, Alaska. Credit: Stephen Clark/Spaceflight Now

NASA and Orbital Sciences Corp. are investigating the cause of the March 4 failure of a Taurus XL rocket that destroyed the $424 million Glory mission, a NASA climate research satellite designed to study the atmosphere and the sun's relationship with Earth.

The clamshell-like nose cone responsible for the March 4 Taurus mishap uses similar components as the Minotaur 1 and Minotaur 4 launch vehicles being prepared for a pair of flights in May.

"They are both potentially affected because of similar components," said Lou Amorosi, the Orbital Sciences senior vice president for the Minotaur program. "We are hoping to show separation from Taurus within the next couple of weeks through testing of those components."

Amorosi declined to elaborate on the progress of the Taurus investigation.

A Minotaur 4 rocket is being prepared for liftoff as soon as May 14 from Kodiak, Alaska. Its payload will be the Naval Research Laboratory's TacSat 4 experimental communications satellite.

Workers at Wallops Island, Va., have already stacked a smaller Minotaur 1 rocket on the launch pad. Liftoff from Virginia's Eastern Shore is scheduled for no earlier than May 30 with the U.S. military's ORS 1 spacecraft, a tactical Earth observation satellite for the Pentagon's Operationally Responsive Space office.

TacSat 4 is already at its Alaska launch site, and ORS 1 is awaiting shipment to Virginia.

Orbital Sciences is the prime contractor for the Taurus and Minotaur rocket families.

Amorosi said Thursday there is "no decision yet" on which launch will be allowed to proceed first.

"The satellites are ready, but we are waiting for the Taurus/Glory failure review board to exonerate Minotaur 1 and 4 before we launch," said Peter Wegner, director of the ORS program.

The Taurus rocket's 63-inch-diameter nose shroud failed to separate in the March 4 launch anomaly. The payload fairing, which shields sensitive satellites on the launch pad and through flight in the lower atmosphere, was supposed to fall away a few minutes after blastoff when the Taurus rocket reached the edge of space.

But the two halves of the fairing did not jettison and clung to the rocket as it ascended into space. The extra mass of the nose cone meant the Taurus XL didn't have enough power to propel the Glory satellite into a stable orbit.

Officials say the rocket's upper stage and payload likely splashed down somewhere in the Pacific Ocean.

It was the second payload fairing separation failure in a row for the Taurus rocket. Another NASA science satellite was lost under nearly identical circumstances in February 2009.

Investigators probing the 2009 launch failure did not find a root cause, but officials identified a most probable cause in the hot-gas system that initiates the payload fairing separation.

Orbital Sciences turned to a different cold-gas system successfully demonstrated three times on the Minotaur 4 rocket.

Officials haven't released any preliminary findings on the March 4 anomaly.