Updated Sept. 3

PASADENA, Calif. — The return to flight of SpaceX’s Falcon 9 rocket, still a “couple of months” away, will also be the first launch of an upgraded version of the vehicle with increased performance, the company’s president said Aug. 31.

Speaking at the American Institute of Aeronautics and Astronautics’ Space 2015 conference here, Gwynne Shotwell said the company was working through a series of intensive reviews of the Falcon 9 after its June failure while preparing the latest upgrade to the vehicle to increase its performance.

“Our next flight will be both the return to flight and the first flight of the upgraded vehicle,” she said. “So whenever people ask me what keeps me up at night, it’s getting ready for that flight.”

SpaceX had been working for some time on an upgrade to the current Falcon 9 v1.1, sometimes called v1.2, with increased thrust. That first launch of the upgraded Falcon 9 was scheduled for September before the June 28 launch failure.

The upgraded Falcon 9 will be slightly taller than the Falcon 9 v1.1 and have a 33-percent increase in performance, said Lee Rosen, vice president of mission and launch operations for SpaceX, in another panel session here Sept. 1. “It has the same engines that we’ve flown before, but with some upgrades and things like that to increase reliability and performance,” he said.

Shotwell said after her panel session that there is a payload assigned to that return-to-flight mission, but could not name it without the permission of the customer. Prior to the launch failure, SES was scheduled to launch its SES-9 satellite on the first upgraded Falcon launch.

SpaceX blamed the June launch failure on a broken strut holding down a helium bottle in a propellant tank in the rocket’s upper stage. Helium leaking from the bottle then caused the tank to overpressurize and burst. Shotwell said SpaceX still believes that is the root cause of the failure.

“We followed the book on how to do a mishap investigation,” Rosen said. That included developing a complex “fault tree” of potential causes, and then carefully going through every branch to make sure nothing was overlooked that could explain the failure. “The fault tree is pretty much closed out.”

Shotwell said that while this problem is relatively straightforward to correct, SpaceX is also examining the vehicle for other potential issues. “What we wanted to do was to take advantage of the lessons that we learned from that particular failure and make sure we’re not seeing something like that anywhere throughout the vehicle,” she said. That includes a series of top-down reviews, and having the work done by every company engineer checked by another engineer.

That additional investigation has delayed the vehicle’s next launch. While SpaceX Chief Executive Elon Musk said in July the vehicle could return to flight in September, Shotwell suggested it may be November before that launch takes place. “It’s taking more time than we originally envisioned to get back to flight,” she acknowledged. “We’re a couple of months away from the next flight.”

Another company official offered a similar assessment. “There are still tests going on, so it’s hard to schedule the return-to-flight activity,” said Hans Koenigsmann, vice president of mission assurance, during an Aug. 31 talk. “My gut feeling is that’s going to be two to three months.”

Shotwell remained optimistic about not just returning the Falcon 9 to flight this year, but also successfully landing the vehicle’s first stage, either on an oceangoing platform or a pad on land, as part of SpaceX’s efforts to develop a reusable version of the vehicle. The company has attempted landings of the first stage on its “autonomous spaceport drone ship” after launches in January and April, but neither was successful.

“I want to see a Falcon 9 first stage land on a drone ship or land on my landing site this year,” she said. “I want to stick a landing this year.”