WASHINGTON — The next crewed launch to the international space station (ISS) will be delayed to mid-May, about six weeks after NASA now expects Space Exploration Technologies Corp.’s (SpaceX) Dragon cargo capsule to make its first flight to the orbital outpost.

Russia had been slated to launch a new three-man crew to the ISS at the end of March, but the Soyuz capsule assigned to the mission failed a prelaunch test last month.

Michael Suffredini, NASA’s ISS program manager, told reporters during a Feb. 2 teleconference that the Soyuz capsule NASA’s Russian partners were preparing for the March mission was overpressurized during prelaunch testing, rendering it unfit to fly.

“During pressure testing of the descent module and the pressurized section of the propulsion module, the vehicle was overpressurized and, as a result, it caused a leak in the area where the hydrogen peroxide system is housed for the thrusters that are used during descent and landing,” Suffredini said on the call.

Russian space officials set aside the damaged craft, Soyuz TMA-04M, and will instead use the next capsule off the assembly line, Soyuz TMA-05M, for the next crew launch to ISS.

The pressurization test that damaged the Soyuz capsule took place Jan. 22, five days before the craft was to be shipped to Baikonur Cosmodrome in Kazakhstan. NASA was notified “within hours” of Russian officials discovering the damage, NASA spokesman Josh Byerly said.

The damaged Soyuz was to have launched March. The replacement craft is slated to lift off May 15.

There are six crewmen aboard the ISS. The three who have been aboard longest — NASA astronaut Dan Burbank and Russian cosmonauts Anton Shkaplerov and Anatoly Ivanishin — are scheduled to return to Earth April 30, more than a month before the Soyuz TMA-22 lifeboat they will ride home reaches the end of its certified 200 days of on-orbit life.

Before Burbank and his Russian crewmates leave ISS, Russia will send an unmanned Progress cargo module to the station. That launch is now scheduled for April 20, five days sooner than previously planned. The change provides some schedule margin between the cargo launch and the April 30 crew return, Suffredini said.

It also limits SpaceX’s April launch opportunities since NASA does not want Dragon and Progress heading for the station at the same time.

After forfeiting a Feb. 7 launch opportunity, SpaceX is slated to fly from Cape Canaveral, Fla., no earlier than March 20. But Suffredini said April looks more likely.

“There are no big problems being worked but there’s a lot of little things they are trying to wrap up,” Suffredini said. “It’s a challenging date, so I wouldn’t hold my breath that that’s going to be the date we’ll actually launch. We’ll fly within a couple weeks of that date, probably.”

Suffredini said a more precise launch date for Dragon’s upcoming mission — a demonstration flight being conducted under NASA’s Commercial Orbital Transportation Services program — would be announced “in a couple of weeks.”

He also said SpaceX is preparing for a Feb. 14 wet dress rehearsal at the Cape. The routine prelaunch test entails rolling Dragon’s Falcon 9 rocket out to the launch pad and performing the entire countdown sequence up until the point the engines would fire.

SpaceX spokeswoman Kirstin Grantham did not respond by press time to questions about the company’s launch preparations and schedule.

Suffredini said that ISS will have enough provisions to support crewed operations even if SpaceX and rival Orbital Sciences Corp. are not able to make their first cargo runs this year.

“We can get into 2013 without any of the commercial vehicles flying,” Suffredini said. “We’re not biting our nails for the [commercial ] flights.”

Dan Leone is a SpaceNews staff writer, covering NASA, NOAA and a growing number of entrepreneurial space companies. He earned a bachelor’s degree in public communications from the American University in Washington.