But Elon Musk, the chief executive of SpaceX, wrote on Twitter that the attempt to land the first stage on a platform in the ocean, in the hope that it could be used again, failed. “Close, but no cigar this time,” Mr. Musk wrote.

After the first stage separated, its engines fired again to turn it around and bring it into a controlled descent. SpaceX had tried similar maneuvers on three earlier flights and twice had slowed the 14-story-tall rocket stage to hover over the ocean before it toppled over and broke apart.

This time, SpaceX placed a platform in the ocean. The company also added “grid fins” to the side of the rocket to steer it precisely to the 300-foot-by-170-foot platform, about 200 miles east of Jacksonville, Fla.

Mr. Musk had guessed that the chance of success on the first try would be 50-50 at best.

SpaceX staff members observed the landing attempt from a safe distance away on a second ship. In the early morning darkness, SpaceX did not get a good video recording of the landing attempt, Mr. Musk said.

“Will piece it together from telemetry and ... actual pieces,” Mr. Musk wrote.

If recovering the first stages of rockets like the Falcon 9 proves viable, the cost of future launches could be greatly reduced.