WASHINGTON — Space Exploration Technologies Corp. (SpaceX), Hawthorne, Calif., test fired a rocket stage outfitted with nine Merlin 1-D engines June 1 at its rocket test facility in McGregor, Texas.

News of the test was announced early June 3 by Elon Musk, SpaceX’s founder and chief.

“1st firing of Falcon 9-R advanced prototype rocket. Over [1 million pounds of] thrust, enough to lift skyscraper,” Musk wrote in the short online message, which was accompanied by a picture of the test.

The test lasted about 10 seconds, SpaceX spokeswoman Christina Ra said in a June 3 email. The test rig included nine Merlin 1-D engines, the latest in SpaceX’s in-house line of kerosene-fueled rocket motors, Ra said. The photo Musk tweeted showed them attached to what appeared to be a long fuel tank.

Falcon 9-R, according to Ra, is the name of a planned Falcon 9 variant with a fully reusable first stage. Initial reusable stages will be based off the expendable Falcon 9 1.1, an upgraded version of the nine-engine rocket the company uses to deliver cargo to the international space station for its biggest customer, NASA.

“They’re iterations of each other,” Ra said.

Falcon 9 1.1 is now slated to debut Aug. 18, when the upgraded rocket is scheduled to launch the Canadian Space Agency’s Cassiope space-weather satellite, agency spokesman Samir Goulamaly told SpaceNews June 5.

Falcon 9 1.1’s core stage will generate roughly 1.3 million pounds of thrust at sea level and about 1.5 million pounds of thrust in a vacuum, Musk said June 3 on Twitter. That makes the rocket about 50 percent more powerful than the current Falcon 9 core, which is powered by the Merlin 1-C engine. Additional tweaking might boost Merlin 1-D’s power as high as 60 percent above Merlin 1-C, Musk said. 

SpaceX has been testing reusable launch vehicle technology under its Grasshopper technology demonstrator program. In a March 28 media conference call after the company’s Dragon space capsule returned from its second space station cargo delivery, Musk said SpaceX would expand its reusable rocket tests this year by attempting to steer a Falcon 9 1.1 first stage to a soft water-landing after a launch. 

Ra would not say when that test might be carried out. 

SpaceX announced back in March that Merlin 1-D had completed 28 preflight hot-fire tests and was ready to be integrated with a rocket. Now, the company has only to launch Cassiope successfully in order to prove that Falcon 9 1.1 — and a 5.2-meter-diameter fairing the company is developing — is ready for the backlog of commercial telecommunications launches SpaceX has accrued. The first of these is for SES-8, owned by SES of Luxembourg. That launch will take place at the Cape Canaveral Air Force Station in Florida.

SpaceX has been putting the 5.2-meter fairing through its paces at NASA’s Plum Brook Station near Sandusky, Ohio. Those tests are not yet complete, Ra said June 3.

Dan Leone is the NASA reporter for SpaceNews, where he also covers other civilian-run U.S. government space programs and a growing number of entrepreneurial space companies. He joined SpaceNews in 2011.Dan earned a bachelor's degree in public communications...