Less than a month after launching its Starship rocket and catching its booster, SpaceX is targeting a sixth test flight of its gleaming stainless steel rocket which towers almost 400 feet tall (121 meters).
The company announced on Wednesday a target launch date of Nov. 18, along with lessons learned from Flight 5 and mission objectives for Flight 6.
Unlike every other mission launch, this time around, SpaceX didnâ€t need to hedge its bets on the timing of the launch based on regulatory approval. When the Federal Aviation Administration cleared the Flight 5 mission, they also approved the companyâ€s plan for Flight 6.
“The FAA determined the changes requested by SpaceX for Flight 6 are within the scope of what has been previously analyzed,†the FAA wrote in an Oct. 12 statement. “Any modifications requested by SpaceX to the approved Flight 6 scope of operations may require further FAA evaluation.â€
To a large extent, Flight 6 will be a repetition of Flight 5, featuring another suborbital flight with a splashdown of the Ship upper stage in the Indian Ocean. However, the mission will include a few key differences.
This time around, SpaceX is reviving a mission milestone from Flight 3 with its intent to demonstrate a relight of one of the Raptor vacuum engines during the rocketâ€s coast phase. That objective was abandoned on that mission when the rocket began to roll much more aggressively than intended.
“Starship did not attempt its planned on-orbit relight of a single Raptor engine due to vehicle roll rates during coast,†SpaceX said in a post-launch statement on March 14.
With two successful coast phases during the most recent flights, SpaceX said this test is now within reach and will serve to demonstrate “the capabilities required to conduct a ship deorbit burn prior to orbital missions.â€
Flight 6 is a suborbital mission and there once again will not be a payload onboard the rocket The mission will instead serve as a teaching tool for SpaceX on further iterations of the vehicle. Some of those lessons will come from a better understanding of the Shipâ€s thermal protection system.
“Several thermal protection experiments and operational changes will test the limits of Starshipâ€s capabilities and generate flight data to inform plans for ship catch and reuse,†SpaceX wrote on Wednesday. “The flight test will assess new secondary thermal protection materials and will have entire sections of heat shield tiles removed on either side of the ship in locations being studied for catch-enabling hardware on future vehicles.â€
Unlike previous tests, Flight 6 will depart from Starbase in southern Texas during the afternoon instead of the morning to allow for a daylight splashdown in the Indian Ocean. Prior to that, SpaceX said that Ship will “intentionally fly at a higher angle of attack in the final phase of descent, purposefully stressing the limits of flap control to gain data on future landing profiles.â€
SpaceX said this will be the last of the Block 1 version of the Ship upper stage that will fly, stating that future versions, beginning with Flight 7, would feature “significant upgrades including redesigned forward flaps, larger propellant tanks, and the latest generation tiles and secondary thermal protection layers as we continue to iterate towards a fully reusable heat shield.â€
Building on booster lessons
One of the big goals for Flight 6 is replicating the success of catching the Super Heavy booster on its return to the launch site. The company would likely also want to reach that milestone with more confidence than the previous go around as well.
In audio unintentionally shared by SpaceX Founder Elon Musk during a livestream of the video game “Diablo IV,†SpaceX employees provide a technical debrief of Flight 5, beginning with, as one employee described it, “scary shit that happened and what weâ€re doing about it.â€
“On the landing burn, we had a misconfigured spin gas support that didnâ€t have quite the right ramp up time for bringing up spin pressure and we were one second away from that tripping and telling the rocket to abort and try to crash into the ground next to the tower,†a SpaceX employee said in the audio posted to X, formerly Twitter, on Oct. 25.
“Wow! Yikes,†Musk replied.
They discussed whether they shouldâ€ve delayed the launch by at least another day to do additional reviews, but one employee said even with that “I donâ€t know if we wouldâ€ve found this one,†referencing the issue that cropped up.
“We were scared about the fact that we had 100 aborts that were not super trivial,†another employee said. “We didnâ€t do as good of a review as we did for pre-Flight 1 when we were in a similar risk posture. We spent a load of time as a leadership team going through every last detail, really arguing it multiple times.â€
One employee described having more control over the timeline of getting to Flight 6 as notable, since they werenâ€t waiting on FAA approval in the lead up to launch.
“Weâ€re trying to do a reasonable balance of seed and risk mitigation on the booster, specifically,†an employee said.
Another employee also pointed to the damage seen to one of the chines near the base of the Super Heavy booster. One of the employees heard on the audio said some of the margins concerning the spot welding on the chine were a concern pre-launch.
“We wouldnâ€t have predicted the exact right place, but this cover that ripped off was right on top of a bunch of the single-point failure valves that must work during the landing burn,†the SpaceX employee said. “Thankfully, none of those in harnessing got damaged, but we ripped this giant cover off over some really critical equipment right as (the) landing burn was starting. We have a plan to address that.â€
The mistakenly shared audio cuts off shortly after this point, so thereâ€s not a lot of insight presently as to what SpaceXâ€s plan is to address the chine issue, but the company did broadly address the improvements to the Super Heavy booster in its prelaunch statement on its website.
“Hardware upgrades for this flight add additional redundancy to booster propulsion systems, increase structural strength at key areas, and shorten the timeline to offload propellants from the booster following a successful catch,†SpaceX wrote. “Mission designers also updated software controls and commit criteria for the boosterâ€s launch and return.â€
Like with Flight 5, SpaceX said it will abort a booster catch attempt in the event that “distinct vehicle and pad criteria†are not met prior to making the attempt. In that scenario, they would perform a powered descent over the Gulf of Mexico. The Flight 6 flight director will be in charge of making the final call.
“If this command is not sent prior to the completion of the boostback burn, or if automated health checks show unacceptable conditions with Super Heavy or the tower, the booster will default to a trajectory that takes it to a landing burn and soft splashdown in the Gulf of Mexico,†SpaceX wrote. “We accept no compromises when it comes to ensuring the safety of the public and our team, and the return will only take place if conditions are right.â€
Ramping up cadence
Depending on how different this next version of the Ship upper stage is to the current Block 1 variant or how much the flight profile and objectives may change will likely drive how quickly SpaceX gets back to the launch pad following Flight 6.
During a presentation to the Mars Exploration Program Analysis Group (MEPAG) on Thursday, Lori Glaze, the acting deputy associate administrator for NASAâ€s Exploration Systems Development Mission Directorate, said that SpaceX booster catch during Flight 5 was an important step towards its role as the lander for the Artemis 3 and Artemis 4 missions.
“Very successful and very important as a major step towards getting us to the Human Landing System for Starship because the ability to bring those boosters back to the pad and then to refurbish them and turn them around quickly will allow SpaceX to actually fly the number of flights that will be required for us to land and return from the Moon,†Glaze said.
Prior to Flight 5, Spaceflight Now spoke with Dr. Kent Chojancki, the HLS deputy program manager who said NASA is hoping to see SpaceX ramp up to a weekly launch cadence from each of its two launch towers down at Starbase in Boca Chica.
He said that an increased launch cadence will be needed as they begin the campaign to fuel a tanker version of Starship, which will remain on orbit as it receives multiple loads of methane and liquid oxygen as a demonstration before the uncrewed Moon landing flight.
“Our first, next big milestone is the long-duration (orbital flight) and propellant transfer. That is the first test that we have not mandated, but itâ€s the first test that is a SpaceX-proposed milestone back to NASA, and the design review that comes from that,†Chojnacki said. “So, the first time that we get to really interrogate that kind of data and understand the boil off, understand the long-duration capability of the Ship and understand now much is being transferred on that is going to be during that test.â€
That on-orbit fueling campaign is anticipated to begin sometime around March 2025, he said.
