A one-second launch window for early Monday’s mission to the International Space Station (ISS) forced Space Exploration Technologies Corp. (SpaceX) to straddle a fine line if it wanted to both get the mission off on time and recover its Falcon 9 first stage.
Commercial space advocate and industry consultant Rand Simberg said Monday launch windows for ISS missions are already tight because the launches must be precisely timed to reach the station. But he said the company’s desire to return the Falcon 9 first stage, as it did early Monday, drives the one-second window as if SpaceX needs to use all of the performance margin on the first stage or else it won’t get the stage back.
“‘We have to launch right now and if we don’t, we don’t get our stage back,’” Simberg said. “Any deviation from that results in more propellant use and there’s a certain point where it wouldn’t get there even if they threw the stage away.”
SpaceX, early Monday morning, both successfully launched its Commercial Resupply Services-9 (CRS-9) mission for NASA and landed its Falcon 9 first stage on land at Kennedy Space Center, Fla. It was the first time in recent launches SpaceX had a land landing as previous landings took place on the company’s drone ship water barge.
Simberg said performance margin is the amount of propellant available beyond what is necessary to perform the nominal mission. He said while you want to have enough margin to get mission reliability, companies can’t cut it too tight or they risk not getting the job done. He added companies don’t want to err on the side of caution with too much propellant as a rocket uses more propellant to carry all that extra fuel.
SpaceX Vice President of Mission Assurance Hans Koenigsmann said in a post-launch press conference that the company had to overcome a bit of adversity to hit the launch window. Koenigsmann said SpaceX struggled a little bit with the timeline early on, but that the launch and pad teams got everything together on the timeline so they could launch on time.
Simberg believes that SpaceX has another reason to ensure it hits that narrow launch window. If it misses the window, Simberg said the company has to wait almost another full day to attempt another launch. This, he said, could cause contractual issues with NASA as the civil space agency prioritizes getting its cargo and goods to ISS over SpaceX getting its first stage back.
Simberg said it is also possible SpaceX would have to compensate NASA if it missed a contractual deadline. SpaceX didn’t respond to requests for comment by press time Monday, but NASA spokeswoman Kathryn Hambleton said via email for each CRS launch, a window is set that includes primary and backup launch opportunities. If there is a delay, she said, and a launch occurs outside that window, then the responsible party (NASA or the contractor) may owe the other compensation based on the cause and any resulting impacts from the delay.
Hambleton said if weather causes a delay, then no fault is assessed. She added that SpaceX does not receive final payment until it has achieved all contractual requirements, which can include return of the capsule, samples and receipt of the post-flight report.
Simberg said ISS missions have narrow launch windows because if a mission isn’t launched at almost exactly the right time it won’t be in the right orbital plane because the earth is rotating. The plane where ISS is located, he said, is sitting in inertial space and not moving much, but the earth is turning underneath it. Simberg said launching at the exact right moment is essential so when the launch vehicle reaches orbit, it is in the same plane as ISS.
NASA Deputy ISS Program Manager for Utilization Joel Montalbano said Monday in the post-launch press conference that the Dragon capsule was doing “fine” and that he was expecting a grapple with ISS at around 7 a.m. EDT Wednesday. Koenigsmann said the recovered first stage was in excellent shape and would be ready to fly again, but he did not specify a date.
SpaceX has another big milestone to achieve later this year when it makes its first Falcon Heavy launch. Koenigsmann said he believed the company would also attempt to land the three stages that compromise the Falcon Heavy. He said the two side boosters would be able to land on land while he was uncertain whether the center core would land on land or use the floating water barge.
Koenigsmann said he believed SpaceX was building another pad near its Landing Zone 1 at KSC to accommodate two rockets landing on land. He said the new pad would not be very far from Landing Zone 1, but would be far enough so the two stages landing don’t influence each other.
SpaceX has a pair of launches set for the next six weeks. Koenigsmann said one launch is the JCSAT-16 satellite for Sky Perfect JSAT Corp. while the other is an Amos satellite for Spacecom. Koenigsmann said he believed the JCSAT-16 mission was for the first half of August while the Amos satellite mission was set for the second half of August. Koenigsmann added that the company would likely attempt another land landing on a CRS mission slated for later this year.
Simberg said the hits keep coming for SpaceX. With six launches already in 2016, the company has tied its annual record for launches. After Falcon Heavy debuts, ostensibly later this year, Simberg believes the next big SpaceX milestone is reusing a first stage.
SpaceX’s CRS-9 mission was uneventful, Simberg said, as everything went according to plan.
“They’re almost making it routine, which is where [they] want to get,” he said.