(CNN) -- The U.S. space shuttle program retired in 2011, leaving American astronauts to hitchhike into orbit. But after three long years, NASA's successor is almost ready to make an entrance.
Orion, the agency's newest manned spaceship, is being prepared for its first mission in December. In future missions, it will journey into deep space -- to Mars and beyond -- farther than humans have ever gone before.
Orion comes loaded with superlatives. It boasts the largest heat shield ever built and a computer 400 times faster than the ones on the space shuttles. It will be launched into space on the most powerful rocket NASA has ever made.
No astronauts will be aboard the December flight, which will test the spacecraft's systems for future manned missions.
Final work on the spacecraft is under way at the Kennedy Space Center in Florida. Orion came one step closer to completion this month with the stacking of the crew module atop the service module.
"Now that we're getting so close to launch, the spacecraft completion work is visible every day," Orion Program Manager Mark Geyer said in a statement.
A 3,600-mile journey
When complete, the Orion capsule will resemble a fencing foil, with a tall spire shooting up from a rounded base. At the top will sit a launch abort system, with downward-facing thrusters that would save the crew from a jarring crash in the event of a rocket malfunction.
The bottom portion, the service module, will perform various functions such as in-space propulsion and cargo storage. Nestled between the two will be the crew module, capable of supporting human life from launch until recovery.
Attached to the service module will be a United Launch Alliance Delta IV Heavy rocket. For the first time since the space shuttle's debut launch in 1981, the crew compartment will ride on the tip of the rocket rather than hanging onto its side, evoking the configuration of the famous Apollo or Gemini missions.
Come December, Orion will be wheeled onto the Cape Canaveral launch pad and the countdown will begin. If all goes as planned, the engines will rumble and its rocket will thunder in an explosion of liquid oxygen, thrusting it toward the stars.
The rocket will carry the modules 3,600 miles above Earth, or about 16 times higher than the average altitude of the International Space Station. Orion "is built to take humans farther than they've ever gone before," NASA says.
Orion will orbit our planet twice on its own during a 4½-hour journey before screaming back into the Earth's atmosphere at nearly 20,000 miles per hour and splashing down in the Pacific Ocean.
Orion astronauts will enjoy access to unprecedented space travel technology.
NASA says the spacecraft's onboard computer system can process 480 million instructions per second, which is 400 times faster than the systems on the space shuttle and 4,000 times faster than those on the Apollo flights of the 1960s and early 1970s.
Orion also boasts the largest heat shield ever built, designed to withstand temperatures that would cause a nuclear reactor to melt down.
"Orion's flight test will provide us with important data that will help us test out systems and further refine the design so we can safely send humans far into the solar system to uncover new scientific discoveries on future missions," Geyer said.
After Orion splashes down, NASA will begin preparing the spacecraft for the future manned missions for which it was designed.
"In the future, Orion will launch on NASA's new heavy-lift rocket, the Space Launch System," the agency said. "More powerful than any rocket ever built, SLS will be capable of sending humans to deep space destinations such as an asteroid and eventually Mars."
The first astronauts will travel into space aboard Orion in 2017. NASA hopes its Exploration Mission-1, a 25-day flight around the moon's dark side, will demonstrate Orion's reliability for deep space missions.
Exploration Mission-1 will send four astronauts farther than any human has been since the last Apollo moon mission in 1972, laying the groundwork for future endeavors.
NASA hopes Orion will ring in a new era for crewed American space exploration, and American flags may someday fly on more space outposts than just the moon.