SpaceX is expected to complete its investigation into why the second stage engine on the Falcon 9 launched last month didn’t relight as planned, while the company also moves on from its Grasshopper reusable test vehicle, a company executive said this week.
Speaking at the International Symposium for Personal and Commercial Spaceflight (ISPCS) in Las Cruces, New Mexico, on Wednesday, SpaceX president and chief operating officer Gwynne Shotwell discussed the company’s most recent launch, the inaugural flight of the Falcon 9 v1.1 on September 29 from Vandenberg Air Force Base. While billed as an upgraded version of the original Falcon 9, she acknowledged that it was, in essence, a new launch vehicle. “We called it the version 1.1 to not scare anybody, but it’s really like the version 1001,” she said. “It was quite a different vehicle.”
While the launch was a success, placing the Canadian CASSIOPE space weather and technology demonstration satellite and several small secondary payloads into orbit, the vehicle’s second stage engine failed to relight after satellite deployment as a test. That failed relight attracted scrutiny from some observers, particularly after Air Force satellite tracking indicated the existence of a number of additional objects beyond the satellites and upper stage, which some interpreted as debris from the upper stage that may have been linked to the failed reflight.
Shotwell, talking to reporters after her ISPCS speech, said the investigation into the failed relight is nearly complete. “We should finish up on Friday,” she said, a timeline that would given insurers enough time to review the report before the company’s next scheduled launch, of the SES-8 commercial communications satellite, now planned for November 12. Unlike the CASSIOPE mission, the SES-8 launch, as well as another commercial communications satellite planned for launch in December, will require the second stage engine to relight to place the satellites into the proper geostationary transfer orbit.
Shotwell did not go into much detail about the cause of the failed relight, citing, among other issues, export control concerns. “We thought we knew right away,” she said. “It was something that we had seen previously on [version] 1.0 and we thought we had gotten completely away from it because, in fact, we obviously relit the second stage a couple of times on 1.0. But in this new configuration there were just a few things that maybe we should have done but didn’t.”
An update about the launch posted by SpaceX on its website earlier this week does offer some additional details. “The engine initiated ignition, with pressure rising in the thrust chamber to about 400 psi, but the flight computer sensed conditions did not meet criteria and it aborted the ignition,” the company stated. “SpaceX believes it understands the issue which didn’t involve anything fundamental, rather a need to iron out some of the differences between operating the engine on the ground versus in a vacuum.”
Shotwell, though, emphasized that the failed relight didn’t mean the launch was by any means a failure. “Let’s be clear: that mission was a success,” she said. “This flight was a complete success. We had no mission requirement to do a relight of the second stage, so it was a success.” Performing three successful flights, as determined by meeting all mission criteria, is a milestone required by SpaceX to be certified by the Air Force for future launches of military payloads.
Shotwell, in her speech and in talks with reporters, also discussed the next stage of the company’s efforts to develop reusable launch vehicle technology. The October 7 flight by the company’s Grasshopper test vehicle, where the vehicle went to an altitude of 744 meters before landing vertically, was the last planned flight of that vehicle by the company. SpaceX is now moving on to a full Falcon 9-R (“Falcon Niner”) first stage equipped with flight-weight, retractable landing legs, for test flights at Spaceport America in New Mexico starting in late December.
“The testing that we’ll be doing here in New Mexico will be of a flight stage,” she said, with the only difference being that the stage will lift off with its landing legs extended; there were no plans to test retracting and extending the legs, at least on the initial test flights. “We’re trying to make it as flight-like as possible.”
While SpaceX isn’t planning to fly Grasshopper again, Shotwell said there were no plans to do anything else with it. “We’ll do like all SpaceX things: we’ll hold on to it,” she said. She added she almost regretted still having Grasshopper intact after its series of tests. “In some ways we’ve kind of failed on the Grasshopper program because we haven’t pushed it to its limit,” she said. “We haven’t broken it.”
Grasshopper and the Falcon 9-R test vehicle are two of the company’s steps towards reusability. SpaceX also conducted a test of trying to recover the first stage on the Falcon 9 v1.1 launch last month, firing three of the first stage’s nine engines after stage separation as it reentered the atmosphere, and tried firing the the center engine again before landing. That second relight didn’t work well, though, because the stage was spinning fast enough (due to aerodynamic forces) to push the remaining propellant against the walls of their tanks, shutting off the flow of propellants to the engine.
In her ISPCS speech, though, Shotwell showed a photo taken of the first stage when it was just three meters above the ocean, immediately before splashdown. (That photo was also included in the SpaceX update on the launch). The stage was still “fully intact” at that time, she said, although “it didn’t remain intact after it hit the ocean” an instant later.
“We were so jubilant after the last flight” because of how close they came in recovering the first stage intact, she said. “Between the flights that we’ve been doing with Grasshopper and this demonstration, we’re really close to full and rapid reuse of stages.”