Graphic animation of the Exploration Upper Stage in space

After Artemis I launched in November 2022 atop the only super heavy-lift rocket capable of carrying crew and large cargo to deep space in a single lift, James Savage went outside with his two daughters, 9 and 12, and looked at the Moon. “We talked about where Orion was and how it was flying past the Moon at that point,” said Savage, chief engineer for Boeing’s Exploration Upper Stage, or EUS. “And we talked about how just a couple missions from now, the first woman will walk on the Moon. The whole experience was a little surreal.”

Savage grew up in Montgomery, Alabama, and as a child, he loved going to the Florida Panhandle, where he visited the Air Force Armament Museum on Eglin Air Force Base. He collected patches from every Space Shuttle mission and always assumed he’d head into a STEM career. As a college student in Nashville, Savage met a Boeing engineer who spoke to his class. “He said, ‘You should come work for us,’” remembered Savage. After college, he did just that.

Savage has now worked on launch vehicles and spacecrafts with Boeing for almost 20 years, in a dozen different jobs. For more than a decade, he focused specifically on the Space Launch System (SLS) super heavy-lift rocket. His team worked on the Artemis I launch, which sent Orion on a 25-day mission around the Moon and back, flying farther than any spacecraft built for humans has ever flown, returning home faster and hotter than any of its predecessors. “That launch in November was about as exciting as it gets in this business,” he said.

Savage began working on EUS as the design integration lead and has been in the chief engineer role for almost five years now. He is convinced it’s one of the world’s coolest jobs. “It’s really exciting to be in my current role and leading the technical team to get to that point of future spaceflight,” he said. “To truly explore, we have to push the boundaries out to the solar system.” He said that push into the unknown is what the nation and humanity need–to help us understand more about ourselves and our place in the solar system, and to inspire the next generation of STEM students. The ability to do that, he said, is made possible by the EUS.

“I am thrilled about EUS,” Savage said, with the excitement one can imagine he felt collecting mission patches back in the day. “When I think about space flight and exploration and where the world needs to go next, I see EUS as the focal point of enabling that capability.”

EUS: More than a large upper stage

On November 16, 2022, NASA’s SLS rocket was successfully launched as part of the Artemis I Mission. The mission, launched at the Kennedy Space Center in Florida, was an uncrewed test flight to validate the rocket component and systems in preparation for future crewed missions. Boeing, which is building the Core Stages for Artemis II, III and IV, as well as the flight avionics suite, is also building the first EUS, which will enable scientific discovery missions like those to the outer planets of the solar system. In size, scope and power, the EUS is like nothing the United States—or any other country on the planet—has ever had in its space fleet.

The Exploration Upper Stage integration area – commonly referred to as the “Gray Box” – at NASA’s Michoud Assembly Facility in New Orleans where the individual articles of the EUS vehicle will be built

Starting with Artemis IV, the EUS will be used on the rocket’s advanced Block IB configuration. The EUS will replace the Interim Cryogenic Propulsion Stage (ICPS), which is currently used on the Block 1 configuration of the SLS rocket, allowing NASA to send astronauts and large payloads to the Moon on a single mission. Compared to the single-engine ICPS, the EUS has larger propellant tanks and four RL10 engines. EUS provides 97,000 pounds of thrust during translunar injection versus nearly 25,000 pounds of thrust from ICPS. This added boost allows for 40 percent more payload to be sent to the Moon and beyond, enabling NASA to send more than 83,000 pounds of cargo on a single crewed mission. That means not only can the EUS send a crew to the Moon and around the Moon, but it will also be able to haul cargo such as small lunar habitats or scientific experiments in the same launch.

“Artemis I was great, and it was a resounding success,” Snell said. “Looking to the future, we know the next Artemis missions carry even more significance as they fly crew to deep space destinations. Crew safety is our top priority and is at the forefront of all that we do.” Steve Snell, Boeing’s Space Launch System Deputy Program Manager and Boeing’s Site Leader at NASA’s Michoud Assembly Facility

“With EUS, we’ll have the opportunity to carry science missions and experiments that were never before possible because of size and volume of payload,” said Boeing’s Space Launch System Deputy Program Manager and Boeing’s Site Leader at NASA’s Michoud Assembly Facility, Steve Snell. He said the additional lift capability that comes with EUS requires fewer flights to enable a sustained human presence in deep space—sooner and more safely. Getting science 238,000 miles away to the Moon, at least 35 million miles away to Mars, and to other deep space destinations faster than ever before is critical because that speed will reduce the complexity of the missions. “The more you can take in one launch, the more you can test on the ground and avoid complexity in space,” Snell said. “Transporting crews in the fewest flights, for shorter durations, is the safest approach to human deep-space travel.”

Savage stressed that EUS is not simply a larger upper stage. “The capacity of EUS is huge,” he said, noting that what other cargo vehicles haul at full capacity is what EUS puts in the trunk. “If you’re going to develop a long-term presence on the lunar surface and in lunar orbit, you have to take much more with you, and EUS allows that to happen. If I’m an astronaut, I want to be able to take a lab and a habitat with me to the Moon – all the things I’d need to be self-sufficient, do my job and explore.”

In many ways, EUS is the embodiment of the Artemis Generation and the resurgence of aerospace: bold, accessible, with more energy and payload mass. “Our innovation and imagination outpace the industry’s current capability to provide launch vehicles,” said Kristine Ramos, Boeing business development engineer. “The SLS rocket with the EUS in the Block 1B configuration is the capability we need to support the dreams and missions people have had for deep space over the last few decades.” She said there’s a “backlog of experiments and missions” people want to have on the Moon, and EUS will eliminate that backlog and inspire the space community to dream bigger. “We can finally start tackling those missions we have been dreaming about. Everyone—kids, scientists, physicists, astrophysicists—is so excited about this.”

Ramos, who plans for future missions, said the EUS offers a lot of flexibility and cost savings, and it significantly accelerates the pace of discovery. With so much interest for missions that need a heavy-lift vehicle in the coming decades, EUS will be in high demand. There will be missions past Mars, a mission orbiting and landing on Saturn’s moon Enceladus, and missions to interstellar medium—which will take about 15 years, compared to the 30 years it took Voyager to reach that same destination. “I can’t imagine waiting 30 years for data,” Ramos said. “Getting that information in half the time will make a big difference in the career of a scientist.” Ramos said one of her favorites is a multi-mission operation with one launch and two departure points and destinations: Uranus and Neptune, since these “ice giant” planets are in the same neighborhood, relatively speaking.

Ramos said setting up infrastructure in space will set off a chain reaction of amazing missions, “whether it’s science or Artemis crew or even tourism.” She describes it as something like “Star Wars” or “Star Trek,” finally becoming a reality. “This will be within our lifetimes,” she said.

Human-rated from the start

The power of EUS—sending cargo to space faster and farther than ever before—is thrilling. But creating a vehicle that’s made for four humans to join the voyage is even more exciting.

“Artemis I was great, and it was a resounding success,” Snell said. “Looking to the future, we know the next Artemis missions carry even more significance as they fly crew to deep space destinations. Crew safety is our top priority and is at the forefront of all that we do.” NASA’s first mission with crew aboard the SLS and Orion spacecraft, Artemis II, will venture about 6,400 miles beyond the Moon on a 10-day mission, proving Orion’s life-support systems and validating the capabilities and techniques needed for humans to live and work in deep space. In April, NASA and the Canadian Space Agency announced the Artemis II crew, which includes the first woman and first person of color on a lunar mission. The announcement was made during an event at Ellington Field near NASA’s Johnson Space Center in Houston.

Liquid hydrogen (LH2) tank integration stand with its transporter awaiting the first Exploration Upper Stage LH2 tank – where hardware such as sensors, tubes and wire harnesses will be integrated

“A bunch of kids were there for the crew announcement, and it was great to see how excited they were,” Snell said. “This program is igniting a fire for our younger generation—seeing pictures from around the Moon that we’ve never had before; seeing kids inspired to pursue STEM careers. I feel like we’re wired as human beings to explore, create and learn, and I don’t think there’s a better program on the planet than the NASA space program.”

Designing a human-rated spacecraft means making safety paramount. “One of the most important things is having redundancies in your systems,” said Snell. “You could have a system or component falter, and you’re not going to lose the mission.” Protecting astronauts and the spacecraft from micrometeoroids and orbital debris, or MMOD, is vital. These naturally occurring and human-made, seemingly innocuous items can become lethal at hypervelocity speeds and are considered the number one threat to astronauts and spacecrafts. EUS has employed design layout choices, material selection, testing, fault tolerance and redundancy to make EUS resilient to MMOD, safeguarding the crew and hardware against these impacts.

Savage said the astronauts he’s talked to appreciate that EUS has been designed for them from the ground up. “We’re designing EUS with their safety and their needs in mind from the very beginning,” he said. “When it comes to the level of safety, it’s one of a kind.”

“It’s not historical artifacts anymore; it’s something we’re doing today.”

In the last year, the EUS program has transitioned from the design to production phase. At every step, Boeing has been leveraging 60 years of spaceflight knowledge and capability and applying that to the EUS. “The engines from the Core Stage are from the Space Shuttle, and some of the big architectural ideas for EUS are from the Delta IV program,” Savage said. “Then add the appropriate safety factors that help you get to human-rated, and couple all that with modern capabilities and computer technology that hasn’t been able to come together for high-capacity human spaceflight platforms until SLS, and you get the best of all worlds.”

In 2022, Boeing completed manufacturing of the test hydrogen tank barrel at NASA’s Michoud Assembly Facility in New Orleans. In February, the EUS Gray Box Assembly Area opened at Michoud, an area of the facility that contains all of the necessary tooling to produce the more powerful upper stage, such as massive welding machines.

Boeing is applying lessons learned from Core Stage to EUS production. For example, the company implemented a system called concurrent engineering, allowing the team to design the vehicle at the same time as they design the production system. That includes the planning of the shop floor construction, technician training, production engineering time and procurement processes—all the systems that have to align. “Rather than designing and then figuring out afterwards how to build it, this system has allowed the design and planning to happen in parallel,” Savage said. “That means we can go into production with confidence.”

Boeing also built a full-scale mockup of the Equipment Shelf (which houses most of the avionics systems as well as the entire Reaction Control System for in-space propulsion operations) and all of its integrated systems to validate the physical layout of the design.

In addition, once built, the EUS structural test article will undergo qualification testing at NASA’s Marshall Space Flight Center in Huntsville, Alabama, to ensure the hardware can withstand the incredible stresses of launch before heading to Kennedy Space Center.

The biggest challenge in the EUS timeline, according to the Boeing team, was pivoting at the beginning of the pandemic—as did the rest of the world. “We kicked off the program with the NASA team in January 2020 and then COVID hit in March,” said Snell. “Having to work [remotely] on a more advanced design stage in the early days was difficult.”

But the team’s passion and excitement about being part of history trumped any inconvenience about working from home,” said Sarah Weis, Boeing’s Block 1B Deputy Program Manager, who has been with SLS for a decade. “Normally you’d think that would be a huge hit to morale, but this team worked right through and excelled,” she said. “We have an amazing team working so hard on design and build. Everyone’s so passionate and excited to be a part of history.”

Savage said it’s hard to describe how exciting it is that we as a nation are finally going back to the Moon—with the intention to stay. “EUS allows humanity to go together, in a more inclusive way, with international partners, with higher levels of diversity on the team,” he said. “When we talk about the Moon, it’s not historical artifacts anymore; it’s something we’re doing today.”