Super Heavy Booster 12 returns to the pad it launched from just seven minutes earlier. Image: Adam Bernstein / Spaceflight Now.
NASA’s plan to return humans to the surface of the Moon needs several puzzle pieces to come together in time, one of which is the lunar lander itself. For the first two planned crewed landings, that capability is coming from SpaceX and its Starship rocket.
A variant of the rocket’s upper stage, referred to as Starship or just Ship, will be used on the Artemis 3 mission. The lander will dock with the Lockheed Martin-built Orion spacecraft and bring two astronauts down to the surface of the Moon and back up again.
While the Starship program had its genesis in 2012, NASA didn’t formally entered the picture until it awarded SpaceX a $2.89 billion contract in 2021, making it a cornerstone of the Artemis 3 mission. Another nod of approval came in the form of a $1.15 billion contract modification in 2022, which added a second crewed landing for Artemis 4.
NASA’s Human Landing System (HLS) program oversees contracts for both Starship development as well as Blue Origin’s lunar lander, Blue Moon, which will be used on the Artemis 5 mission.
Speaking with Spaceflight Now ahead of Starship Flight 5 in October, Dr. Kent Chojancki, the HLS deputy program manager, said each of the rocket’s iterative test launches have been illuminating for NASA to watch.
“We are very interested. We are interested in the performance of both the booster and the Starship,” Chojancki said. “We learn a lot each time it happens. SpaceX has been very forthcoming with data, data reviews, understanding how it moves forward.”
Rapid reusability
The big headline-grabbing highlight of Flight 5 was the successful catch of the Super Heavy booster using the launch tower that SpaceX calls “Mechazilla.” Chojancki said from the HLS office’s perspective, reaching that milestone successfully begins to unlock a key ingredient for the success of SpaceX’s proposal for its Moon landing: rapid reusability.
“What’s interesting to us about that is, for the architecture that SpaceX has proposed and is implementing, they’re going to have to do several launches in order to aggregate propellant in low Earth orbit prior to going to the Moon,” Chojancki explained. “Being able to rapidly reuse the boosters allows demonstrates that cadence.”
Chojancki was referring to SpaceX’s plan to first launch a tanker version of Starship into orbit and then over multiple successive flights, send other Starships to dock with it and offload its fuel to build up a reservoir.
Eventually, for a Moon landing mission, an HLS version of Starship will dock with the tanker, receive its stored fuel and then depart Earth orbit for the moon. During Artemis 3, Starship will dock with the Orion spacecraft directly but for Artemis 4, it will dock with NASA’s Gateway space station.
Before either of those events happen though, there will be an uncrewed Starship landing demonstration on the Moon.
“One of the requirements that NASA has prior to putting astronauts on the Starship is that they (SpaceX) have to demonstrate an uncrewed demo with a landing and then being able to leave the surface of the Moon,” Chojancki said. “We’re not asking for a full return, but they’re going to get off of the surface, demonstrate that they can start the engine.”
Propellant transfer
Looking beyond Starship Flight 5, Chojnacki said the HLS program office is looking forward to next year’s propellant transfer demonstration.
“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 it’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.”
A rendering of how a Ship-to-Ship propellant transfer will likely operate in low Earth orbit. Graphic: SpaceX
Chojnacki said SpaceX is looking at March 2025 to begin that fueling campaign and “hoping (the) first half of ’25 to be able to see that work.” He said two launch towers at the Starbase facility near Boca Chica Beach will be needed to do that work.
In order to make this work long-term, Launch Complex 39A at NASA’s Kennedy Space Center in Florida will need to come into the picture. Chojnacki added that the pace of launch will have to greatly increase, potentially to a bi-weekly cadence.
“Operations where you’re launching maybe once a week out of each pad, so that each pad has a two-week turnaround, but you’re launching about on a weekly basis to go up, fill the depot, come back and reuse those boosters and tankers to get that operation,” Chojnacki said. “That’s the kind of cadence that would be great. We don’t really know what the boil off is. Some of the early flight experiments we’re looking for is that data to understand what that curve would look like.”
SpaceX’s Starship rocket launches for a third time in program history on Thursday, March 14, 2024. Image: Adam Bernstein/Spaceflight Now
Earlier this year, during Starship Flight 3, SpaceX performed an internal propellant transfer demonstration as part of a $53.2 million NASA Tipping Point contract it received in 2020. When it was announced, the stated goal was a “Large-scale flight demonstration to transfer 10 metric tons of cryogenic propellant, specifically liquid oxygen, between tanks on a Starship vehicle.”
Chojnacki said going to the next step, a Ship-to-Ship propellant transfer will be notably more challenging.
“With [the Flight 3 demo] being internally, we did not have to get a docking. We did not have to get a fluid coupling. So, I think we have increased the complexity by going on to to it from Starship to Starship,” Chojnacki said. “We were able to measure the transfer mass at about five percent. That really met the goal that we were trying to accomplish.”
“It transferred more than they had suggested it could and we were able to measure and back out that data. So, we’re pretty pleased with the test and the sensors that were used for that measurement and we can extrapolate that knowledge to the Ship-to-Ship.”
NASA helps improve Starship
While the Starship rocket is something that SpaceX had in work years before tying in with the HLS program, it has benefited notably from the expertise of NASA engineers. Chojnacki said SpaceX has been receptive to the feedback that have come from data and hardware reviews.
“We had asked for some of their components to test and, maybe at the beginning, they’re like ‘I don’t know why you want my cryo valve,’ but at the end, we brought the cryo valve in house, we tested it, we had some ideas for improvement and we gave them that feedback,” Chojnacki said. “They were like, ‘Huh.’ Made some of the collaborative teams work together, made some updates, brought the valve back in house and really improved some of the performance.”
“So, it was not us directing them. It was, ‘We have some ideas on this,’ and they were able to implement it for the good of HLS.”
Onboard cameras on the Starship upper stage flown during Flight 3 (Starship IFT-3) show the vehicle surrounded by plasma as it reenters the atmosphere on March 14, 2024. Image: SpaceX
Chojnacki said another area of shared work involved the development of micrometoroid and orbital debris (MMOD) and cryogenic propellant thermal protections.
“Where we have been doing some in-house testing on the behalf of SpaceX is on their MMOD thermal tiles for in space. So not the heat shield for reentry, not the hot side, but being able to have the MMOD tile and the reflective for keeping the cryos cold,” Chojnacki said. “We brought a couple of those tiles in and did some testing. SpaceX was very happy with the capability, both at Glenn Research Center and Marshall’s test capability. And so, we’ve expanded that relationship and being able to do some testing for them.”
The Astronaut Office, based at the Johnson Space Center in Houston, Texas, has also been instrumental in developing the HLS Starship variant. Chojnacki said astronauts hold monthly meetings, nicknamed “office hours,” with SpaceX at its headquarters in Hawthorne, California.
During those sessions, Chojnacki said they discuss design elements that don’t necessarily fit into hard and fast safety requirements.
Astronauts were fully suited while conducting mission-like maneuvers in the full-scale build of the Starship human landing system’s airlock which will be located inside Starship under the crew cabin. Image: SpaceX
“They just sit and they say these are some of the things we’ve been concerned about. These are some of the things we’d like to see. And it’s soft influence. It’s being able to say, you know, if you’re trading between this being on the left-hand side and this being on the right-hand side, we’d very much like the right-hand side for the various reasons of this,” Chojnacki explained. “And so, they’re able to communicate that. So, having that crew interaction time with them has been really important.”
Astronauts have also been involved with integrated testing campaigns, like working alongside Axiom Space with mockups of the spacesuits that will be used on the Moon in tandem with a Starship demo interior or elevator system.
“We’ve been able to work both with Axiom, the crew and SpaceX in regards to further that. We have also looked at the crew cabin, the mockup, the visuals some of the sleeping quarters, the laboratory and everything else that is being built as mockups at Boca Chica,” Chojnacki said. “The next time we’ll really have a chance to look at it as a whole is we’re getting a design update from SpaceX to review in the month of November and then, we’ll be able to look at it at the critical design review next year.”
What comes next?
In addition to November’s design update from SpaceX and next year’s propellant transfer demonstration, there are a number of milestones left ahead of SpaceX and its role in the HLS program.
NASA and SpaceX will continue working on the docking capability of Starship on Earth rather than in space. The two entities already performed a series of more than 200 docking scenarios over a ten-day period earlier this year at the Johnson Space Center.
NASA and SpaceX recently performed qualification testing for the docking system that will help future #Artemis crews move between spacecraft to carry out lunar landings. The tests, conducted over 10 days, included more than 200 docking scenarios.
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— NASA Marshall (@NASA_Marshall) February 29, 2024
SpaceX will also need to perform a relight of its Raptor vacuum engine on orbit and eventually demonstrate a land landing after leaving orbital space.
In the summer of 2025, NASA and SpaceX will conduct the critical design review, which Chojnacki said is “going to be the opportunity to look at their design, and say how do you comply with the 27 requirements that we’ve had?”
“Those 27 requirements are some safety-type requirements. You shall land on the South Pole, that’s a requirement. And so, we’ll look at how they’re progressing against those set of requirements,” Chojnacki said. “And then, SpaceX has proposed to us the way they intend to verify those requirements and we have authority to approve or disapprove their verifications at the end.”
“And all of that will culminate in a design certification review, where NASA will receive all the information from the verifications and say, ‘Of the 27 requirements, you have satisfied all of them in this manner. We accept this design is certified to do what you say it’s going to.’”
Artist’s illustration of the Starship landing system on the Moon. Credit: SpaceX
All of this is building up to the Moon landing on Artemis 3. At the beginning of 2024, NASA announced the delay of that mission from December 2025 to September 2026. And while another date slip is certainly within the realm of possibility, Chojnacki said from where he’s sitting, he doesn’t believe that Starship will be a holdup.
“That is definitively the date we’re working towards. We don’t have any known roadblocks. We have some first time things that have to be demonstrated and we have a plan to go demonstrate those,” he said. “But I mean, there are first time things, sometimes there are things that get, that bite you. And so, we are working through those, but there are no known roadblocks to achieving that.”