A Minotaur 1 rocket powered by a surplus Cold War-era missile stage more than 54 years old is poised to blast off from the Eastern Shore of Virginia Tuesday morning, heading to orbit with three top secret spacecraft for the U.S.

The Minotaur 1, assembled and operated by Northrop Grumman, is set to fly its first mission since 2013.

The Minotaur rocket family is primarily geared to launch satellites for the military.

The Minotaur 1 rocket’s M55A1 first stage motor was cast with solid propellant in 1966 by Thiokol, now part of Northrop Grumman.

The SR19 second stage motor, produced by Aerojet, was filled with its solid propellant in 1983, according to a Northrop Grumman spokesperson.

The age of the first stage means it is likely the oldest rocket motor ever used on a space launch.

The mission set for launch Tuesday is designated NROL-111. While the satellites on-board the Minotaur 1 rocket are classified, NRO officials held a pre-launch press conference last week to preview the mission.

In 2016, the Space Force’s Space and Missile Systems Center, then part of the Air Force, selected a Minotaur 1 rocket for the NROL-111 mission.

The launch Tuesday will mark the 28th flight of a Minotaur rocket since 2000, including suborbital missions.

It will be the 18th orbital launch of a Minotaur rocket, and the 12th use of the Minotaur 1 configuration, which is capable of placing a payload of up to 1,278 pounds (580 kilograms) into low Earth orbit.

The NROL-111 mission is the second launch in two days for Northrop Grumman’s rocket program.

The company’s air-launched Pegasus XL rocket fired into orbit Sunday off the coast of California with a small Space Force satellite named Odyssey.

Northrop Grumman configured a Pegasus rocket already in its inventory to launch the Odyssey space surveillance satellite.

Eberly said Northrop Grumman plans to launch 28 rockets in 2021, and they all use the same common avionics package, from small target vehicles to the medium-class Antares rocket.