BOISE, Idaho — Space Exploration Technologies (SpaceX) is making minor software modifications on its Falcon 9 medium-lift rocket in preparation for its second flight, now targeted for October, based on issues encountered during the vehicle’s successful debut in June.
Improvements to Falcon 9 hardware have been under way since the company completed an internal analysis of the vehicle’s maiden launch from Cape Canaveral Air Force Station, Fla. A videotape of the launch posted on the company’s website shows the rocket rotated several degrees as it left the launch pad.
In a Sept. 2 e-mail, SpaceX spokeswoman Kirstin Brost said engineers are “tweaking the engine gimbal angle in software” to correct the problem. Another fix in the works involves relocating a liquid oxygen drain outlet that contributed to a second-stage roll captured by an on-board camera that taped the launch from liftoff to orbit insertion.
“The second-stage roll is being fixed by changing the location of the [liquid oxygen] pump drain outlet to avoid chilling the hydraulic lines of the roll control actuator,” Brost said.
In addition, the company has been investigating the cause of a failed second-stage restart attempt that occurred during the maiden flight. In June, SpaceX spokeswoman Emily Shanklin said the restart was not a primary mission objective for the debut, “but we actually did reignite briefly and we are evaluating that data.”
The maiden Falcon 9 mission was funded by a U.S. government agency that SpaceX has declined to name and carried a qualification unit of the company’s Dragon space station cargo capsule into orbit. The next three Falcon 9 missions will carry Dragon in an increasingly complex series of demonstrations under SpaceX’s $278 million Commercial Orbital Transportation Services (COTS) agreement with NASA. Upon successful completion of the demo missions, SpaceX will begin making regular cargo-delivery runs to the international space station under a separate contract valued at $1.6 billion.
In June, SpaceX founder and Chief Executive Elon Musk said the company had proposed combining its second and third COTS demos into a single mission. Under the current plan, the second COTS flight will be a five-day mission during which Dragon would approach within 10 kilometers of the space station and demonstrate the ability of the station’s crew to receive telemetry from the capsule and send commands. On the third and final COTS demo, Dragon is supposed to berth to the station for the first time.
In August, Alan Lindenmoyer, head of NASA’s Commercial Crew and Cargo Program Office at the Johnson Space Center in Houston, said the agency is considering the proposal, but that a decision awaits the outcome of the first COTS mission.
“We have to go through the technical details … because it’s important to complete the demonstration of contingency maneuvers with the vehicle before we actually complete berthing with the station,” Lindenmoyer told Space News Aug. 19. “We need to understand is it possible for SpaceX to conduct a mission that completes all those prerequisites — such as breakout maneuvers and multiple rendezvous and station-keeping — and still achieve a berthing.”
Musk said in June that if the proposed combined demo is unsuccessful, a third COTS mission could serve as a backup. But if his plan works, the combined demo would clear the way for SpaceX to begin delivering cargo to the space station under the Commercial Resupply Services contract it signed with NASA in December 2008.
Although Falcon 9’s debut was supposed to have happened in 2007, with the first space station resupply mission slated for the end of this year, hardware development has taken longer than planned.
Brost said the company recently asked the U.S. Air Force’s 45th Space Wing to reserve Oct. 23 at the launch range for its first COTS mission. In May, the company said subsequent demonstration flights had been pushed from fall to spring, and Brost said the need for additional development work on space station proximity operations and berthing, as well as final certification by the space station safety review board, makes those launch dates difficult to predict.
“We are hopeful that we can berth with station before next summer, but development programs need to allow for the unknown,” she said.
NASA spokesman Joshua Byerly said delays with new rockets and spacecraft are to be expected.
“The upcoming test flight is much more complicated since it involves not only the Falcon 9 rocket, but also the Dragon spacecraft,” he said in an Aug. 11 e-mail. “So you are talking about two brand-new spacecraft.”
Byerly said it is unclear how SpaceX’s COTS demo schedule might affect its space station resupply missions.
“It is too soon to tell whether the commercial resupply flights will be impacted, but we will continue to monitor the progress of our partners,” he said.
