LOS ANGELES — In half a century of spaceflight, only a few countries have been able to send a capsule into space and have it return to Earth intact, a technological and financial feat reserved for the wealthiest of nations.

That may all change as early as today, when a Hawthorne, Calif.-based rocket venture plans to send an Apollo-like capsule into space and have it splash down in the Pacific, becoming the first commercial spacecraft to orbit the globe and survive the fiery re-entry back to Earth.

If the mission is successful, it would mark a major turning point for private spaceflight and a key milestone for SpaceX, a venture started by Silicon Valley entrepreneur Elon Musk.

“When Dragon returns, whether on this mission or a future one, it will herald the dawn of an incredibly exciting new era in space travel,” said Musk, the founder and chief executive of SpaceX, formally known as Space Exploration Technologies Corp.

The company, mostly on its own dime, has developed and built the Dragon capsule, which is considered a contender for the job of ferrying astronauts to and from the International Space Station after the space shuttle is retired in 2011. The Dragon is capable of carrying up to four astronauts into space.

In the unmanned test launch, the capsule would be lifted into space by a Falcon 9 rocket, also developed by SpaceX. The capsule is scheduled to orbit the Earth twice before re-entering the atmosphere and splashing down in the Pacific about 500 miles west of Southern California. The craft would deploy parachutes to slow its descent.

The entire undertaking is expected to take about four hours.

SpaceX said the mission would also include maneuvering the capsule during orbit through the use of its propulsion thrusters, transmitting telemetry data and recovering the 9,260-pound spacecraft from the ocean.

If all goes as planned, the Dragon will be the nation’s first new human-capable spacecraft to orbit the Earth and return since the space shuttle first started flying nearly 30 years ago. It also would mark the first time that a space capsule would splash down in the ocean since the last Apollo mission in 1975.

Aside from the U.S., only four countries and one intergovernmental agency have been able to launch a spacecraft and have it successfully re-enter the Earth’s atmosphere: Russia, China, Japan, India and the European Space Agency.

The Dragon capsule is on a launch pad at Cape Canaveral along with the company’s massive Falcon 9 rocket, which made its first flight in June.

The launch had been slated for earlier in the week, but Monday the company revealed that cracks in an engine nozzle would delay the mission.