Building a rocket to the Moon and back again is expensive and complex, as two scrubbed launches of Artemis I have shown, but it ultimately comes down to each individual engineer and a legendary can-do engineering mindset.
“Engineer to engineer, it’s quite challenging,” said Ralf Zimmermann, Airbus program manager on the Orion European Service Module (ESM), part of the Artemis I missions. “Given the environmental conditions of space and the mission requirements, it’s hard to achieve. Based on our skills and heritage, we can manage it, but we are on the edge of technology.”
Zimmermann is one of thousands of engineers and scientists who have worked for years to get Artemis I, including the ESM, ready for its flight around the Moon and back. The second delay on Saturday of the mission launch from the Kennedy Space Center in Florida helps put things in perspective about building a rocket and spacecraft and the constant testing involved.
Take weight for instance. “There’s always a limit on weight,” Zimmermann explained in a recent interview with Fierce Electronics. “Everything is easy if you are on the ground and you have high pressure, sure, you can build a thick wall. But in space, everything is under high pressure without weighing too much. It’s a question of how much mass you need to invest to be safe and still light enough to fit onto the rocket. That’s the basic question you need to solve.”
Another big concern is reliability. “You have to build in reliability if you need to correct something to make it work,” Zimmermann said. “If you build a car and something does not work, you go to a repair shop and order a new part. You cannot do that, even on a manned space vehicle. This makes it challenging for engineers. If you have a failure, can you still make things work?”
There are thousands of critical moments in the Artemis I flight from the time of launch to splashdown 37 days later. For the ESM, there are rockets that must burn precisely to inject Orion into an orbit around the Moon and then burn again much later in the mission to take Orion out of lunar orbit on a pathway home to Earth.
“These are nervous moments,” he said. “Everything needs to work.”
Artemis I is eventually set to launch from Kennedy Space Center in Florida on a flight around the Moon and back with no crew to splash down in the Pacific off the coast of San Diego. Two Artemis launch attempts scrubbed Aug. 29 and Sept. 3 put a focus on the engineer's job and have exacted an emotional toll even as NASA Administrator Bill Nelson described the team's response as "highly professional."
Zimmermann came to Florida for both attempts with other Airbus co-workers and their families in hopes of viewing the planned launches, while Airbus had a working staff at Johnson Space Center in Houston directly involved in switching on and off the ESM for launch attempt and will be present supporting the mission once the launch occurs.
"Emotionally, the scrubs of course are up and down," he said. "However, we are trying to launch a new vehicle and some failures might occur at the last moment. Remember, the tanking was completed during the first attempt. I am happy that the ESM, as part of the complete Orion, worked well during activation and deactivation twice now!"
The odds of a scrub across all launch attempts are about one in three, with half of the scrubs due to weather, according to a Space Force officer.
Orion’s two parts
The Orion spacecraft sits above the Space Launch System rocket, a total structure 320 feet tall. Orion is comprised of two parts: the Crew Module, which provides habitat for up to four astronauts and their cargo, and the European Service Module, which provides propulsion, power, water, oxygen and nitrogen and systems to keep the spacecraft at the right temperature and on course. Both are connected with the Crew Module Adapter.
For the first time with the ESM, NASA entrusted a non-US company to build a mission critical element for an American human spaceflight mission. The European Space Agency (ESA) has granted Airbus the prime contract with industrial partner Lockheed Martin Space to build six ESMs to handle crew life support and propulsion for Orion, among other tasks. Behind the ESA are 10 European countries supporting the mission.
The ESM half of the Orion spacecraft was built at the Airbus site in Bremen, Germany, using the skills of 150 Airbus engineers along with ESA and industry partners. Airbus gained experience on five Automated Transfer Vehicle flights to the International Space Station a decade ago. ESA has invested $2 billion to build a total of six ESMs for Artemis I and upcoming Artemis missions.
The ESM weighs 13 tons and is unpressurized even though it provides key life support for the Crew Module just above it. At 12 feet x 12 feet, it contains 20,000 components, including electrical equipment and thrusters, propellant tanks and miles of cables.
A signature feature is a four-bladed solar array, 62 feet in diameter when fully deployed, to generate power for the spacecraft. There are also 8.6 tons of propellant to power a main engine, refurbished from 19 previous space shuttle flights, Zimmermann said. There are also eight auxiliary engines and 24 smaller thrusters for navigation. When the ESM-3 is used for the first landing on the moon, planned for 2025 with Artemis III, Orion will dock with the Lunar Gateway, an orbiting lunar platform.
33 engines
“You can imagine with 33 engines, even if the main thruster doesn’t work, there are other engines,” Zimmermann said. “We have demonstrated we can do it. All the technologies have been tested and proven.”
Packing the ESM with thousands of components was one of Zimmermann’s biggest pre-launch challenges, but staying on pace to build all six ESMs was paramount. The first module took 2.5 years to build, while it took two years to build the second and will take 1.5 years for third. The final three ESMs must be built at a rate of one per year. “The main demand was delivery,” he said.
As for packing 20,000 components inside the ESM, Zimmermann chuckled as he described the task, somewhat like cramming a large suitcase to the brim to head out for a family vacation. “Just when you think you have it completely full, your wife and kids want to add something else.”
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