NASA’s quest to send astronauts out into the solar system begins this week with a two-laps-around-Earth test flight.

The new Orion spacecraft is not going to Mars just yet; Thursday’s debut will be unmanned and last just 4½ hours. But it will be the farthest a built-for-humans capsule has flown since the Apollo moon missions, shooting 3,600 miles out into space in order to gain enough momentum to re-enter the atmosphere at a scorching 20,000 mph.

The dry run, if all goes well, will end with a Pacific splashdown off Mexico’s Baja coast. Navy ships will recover the capsule, a la Apollo, for future use.

This initial Orion is rigged with 1,200 sensors to gauge its durability for the day when astronauts do climb aboard during the decade ahead. Advertised destinations include an asteroid to be corralled in lunar orbit for human exploration in the 2020s, followed by Mars in the 2030s.

“We’re approaching this as pioneers,” said William Hill of NASA’s exploration systems development office. “We’re going out to stay eventually. … It’s many, many decades away, but that’s our intent.”

Lockheed Martin Corp. built the capsule and is staging the $370 million test flight for NASA.

Orion is NASA’s first new spacecraft for humans in more than a generation, succeeding the now-retired space shuttles. Unlike the capsules under development by two U.S. companies for space station crew transport, Orion is meant for the long haul, both in time and space; it would be supplemented with habitats for potential Mars trips.

“We need a spacecraft that’s going to be sturdy enough and robust enough” to carry astronauts well beyond low-Earth orbit for weeks and months at a time, said Lockheed Martin’s Bryan Austin, a former NASA shuttle flight director who will oversee Orion’s maiden voyage.

“That’s how Orion really separates itself from the commercial field. They’re there to get you to station and back. Of course, we’re there to be hardened enough to sustain it for that long duration.”

For this orbital tryout, a Delta IV rocket will hoist Orion from Cape Canaveral Air Force Station. Liftoff is scheduled for 7:05 a.m. EST, just after sunrise. The rocket, with Orion and its launch escape tower at the tiptop, stretches 242 feet high.

Future Orion launches will use the mega rocket still under development by NASA, known as SLS or Space Launch System. The first Orion-SLS launch is targeted for 2018, unmanned, followed by the first piloted mission in 2021.

No one at NASA is pleased with such a poky pace. At best, it will be seven years before astronauts fly Orion — anywhere. By comparison, it took eight years from the time President John Kennedy announced his intentions of landing a man on the moon — before John Glenn had even rocketed into orbit — to Neil Armstrong and Buzz Aldrin’s lunar boot prints in 1969.

Given the present budget situation, “it is what it is,” said Kennedy Space Center’s director Robert Cabana, a former astronaut. And the presidential election ahead could bring further delays and uncertainties.

In any case, don’t confuse Orion with NASA’s old-time Apollo capsules.

For one, the 11-foot-tall Orion is designed to hold four astronauts, one more than Apollo. For relatively short outings of three weeks or so, Orion could accommodate six.

“People often ask us, ‘Hey, this thing looks like a capsule, it looks like Apollo,’ and people will confuse that with ‘it’s not new,’ ” said Scott Wilson, NASA’s Orion production operations manager. While physics drives the capsule’s outer bell shape, “everything else in the capsule is state-of-the-art,” he said.

“Everything, from the thrusters, from the environmental control systems, to the structure itself” is benefiting from all the advances in technology, Wilson said. With no one on board, this first Orion will have hunks of aluminum in place of seats for ballast, simulators instead of cockpit displays and, obviously, no life-support.

The heat shield on Orion’s base, designed to protect the craft from the searing temperatures of atmospheric re-entry, is 16.5 feet across and is the biggest, most advanced of its kind ever made, according to NASA. On this flight, Orion will reach close to 4,000 degrees, not quite the 5,000 degrees that would be generated from a moon mission, but close enough for a shakedown.

That’s why Orion will aim for a 3,600-mile-high peak altitude, more than 14 times higher than the International Space Station — to pick up enough speed to come back fast and hot.

NASA is pulling out all the stops for Orion’s inaugural run. The space agency has teamed up with the nonprofit, educational Sesame Street Workshop to promote not just this mission, but the effort to send astronauts to Mars. Comics, video and graphics are building up the countdown.

“The astronauts of the 2030s and beyond are today’s preschoolers,” NASA explains on its website.

There’s even a new countdown clock to herald the event.

Last week, Kennedy Space Center took down its familiar launch countdown clock dating back to the Apollo program; officials said it had become too expensive to fix and maintain. A new multimedia display went up in its place, just as long at 26 feet, but taller at 7 feet.

(AP)