One hundred fifty-four feet long, packed with 700 tons of propellant and anchored to the side of a Utah hill, a solid rocket motor developed for NASA’s next generation of rockets is to unleash 3.6 million pounds of thrust in a test Tuesday morning.

Whether this motor design will ever go anywhere is uncertain.

To critics, the solid rocket motor — an elongated version of the boosters that fly on the space shuttles — is expensive, antiquated technology.

Advocates counter that solids are reliable and safe and provide a big bang for the buck.

NASA is still working on Constellation, the program to send people back to the Moon, and those plans call for the solid rocket motor to serve as the first stage of the Ares I rocket for taking astronauts to the International Space Station and part of the Ares V rocket for the Moon missions.

But the Obama administration wants to cancel Constellation, and bills moving through Congress also scale back the human spaceflight program.