As shuttle Endeavour coasted through Central Florida’s balmy skies last night, what may become the astronauts’ next ride to space was poised on a launch pad a few miles away.

Over the weekend, Space Exploration Technologies, or SpaceX, hoisted its first Falcon 9 rocket at a new launch complex just south of the Kennedy Space Center, where Endeavour touched down. The shuttle returned from a 14-day construction mission at the International Space Station.

Just four flights remain before NASA retires Endeavour and sister ships Atlantis and Discovery, due to safety concerns and operating costs that eat about $3 billion a year. Instead, the Obama administration wants to spend $6 billion over the next five years helping private launch companies like SpaceX develop the means to fly people in orbit.

SpaceX plans to pump fuel through its Falcon 9 booster this week to test the rocket and its Florida launch team. The company, founded by internet entrepreneur Elon Musk, last year successfully delivered its first commercial satellite into orbit aboard the smaller Falcon 1 booster, which launched from Omelek Island in the Kwajalein Atoll. It was the fifth launch for SpaceX, following a successful test launch with a dummy payload and a trio of launches that either failed or didn’t reach orbit.

“There’s a lot riding on the maiden flight of Falcon 9,” NASA administrator Charlie Bolden said last week.

In addition to the Falcon rockets, SpaceX is developing a capsule known as Dragon, which will carry cargo — and possibly crewmembers — to the space station. NASA already has contracts with SpaceX, and another launch firm called Orbital Sciences Corp., to demonstrate their rockets and then fly cargo to the space station.

The Falcon 9 poised on the launch pad is not part of the NASA work, but a flight demo SpaceX is undertaking on its own dime as a test. Launch is targeted for no earlier than March 22.

(New rocket on the pad at Cape Canaveral, Fla. Credit: SpaceX)