LOS ANGELES (AP) — A massive space shuttle fuel tank squeezed through the streets of Los Angeles and loomed over vehicles on a busy freeway Saturday to join the retired orbiter Endeavour on display at the California Science Center.

The 33-ton, 154-foot-long external propellant tank began moving a few minutes after midnight from coastal Marina del Rey, where it arrived by barge Wednesday, to the California Science Center in downtown Los Angeles.

The orange-brown, sausage-shaped tank — the last of its kind — is traveling by truck at about 5 mph. By early morning, it had moved through suburban Inglewood. Crews trimmed a few trees and unbolted a stoplight pole and turned it so the arm wouldn't hit the towering tank.

Freeway drivers got a shock as the tank rolled by on a bridge over Interstate 405, an artery west of downtown that was busy even on Saturday morning.

Some of the children watching the move wore home-made space helmets.

"It's this next generation of explorers. These kids are going to remember today their whole lives. And they're going to think about it when they choose their career paths. They're going to study harder in school. And it's going to make us happy," astronaut Mike Fincke, who flew on the Endeavour's final flight in 2011, told the Los Angeles Times.

The tank will be displayed upright along with the shuttle and two solid-rocket boosters, as if ready for takeoff.

The journey was expected to take 13 to 18 hours to squeeze down 16½ miles of streets, avenues and boulevards to Exposition Park near downtown.

The trek drew smaller crowds than the journey of the 122-foot-long Endeavour. With a wingspan of 78 feet, the orbiter was similarly hauled 12 miles to the center from Los Angeles International Airport. Extensive preparations for Endeavour's trek included removing trees, street posts and other obstacles, but that journey still took about 17 hours longer than planned.

Although longer, the external tank is much narrower than the shuttle, with a diameter of 27.5 feet.

The tank was shipped to California by barge from a NASA facility in Louisiana. The tank traveled through the Panama Canal to the Pacific and arrived at Marina del Rey, a yacht harbor on the Los Angeles County coast where it was offloaded to await the weekend move.

The move Saturday began with a bit of fanfare. A New Orleans-style jazz band played "When the Saints Go Marching In" and some people waved handkerchiefs to wish the tank bon voyage.

Known as ET-94, it was NASA's last flight-qualified external tank but was never used before the shuttle program came to an end.

External tanks not only carried propellant for space shuttles' main engines but were the backbone of the launch system. An orbiter and two solid rocket boosters would be attached to the tank for the fiery ascent into space.

Inside ET-94 are two internal tanks for millions of pounds of liquid oxygen and liquid hydrogen as well as other equipment.

The tank's surface is covered with a layer of foam to keep the propellants at the proper temperature, reduce the formation of ice and to provide protection from heat as it sped through the atmosphere.

External tanks used on shuttle missions would be destroyed, burning up as they fell back through the atmosphere after being discarded by the orbiter.

ET-94 was built for use by the shuttle Columbia, which disintegrated over Texas as it was returning from a mission. The investigation found that foam fell off that mission's external tank during launch and punched a hole into a wing, allowing hot gases of the fiery re-entry inside the structure. Investigators used many pieces of foam from ET-94 in tests to come to the conclusion.