An edited extract from book The Launch of Rocket Lab
In 2017, Nasa formally revealed plans for Artemis, a follow-up programme to the famed Apollo missions of the 1960s, which aimed to land humans back on the Moon in the 2020s. The centerpiece of the plan was the Gateway space station, that would operate in orbit around the Moon as a place for astronauts to live and work between trips to the lunar surface. Like the International Space Station, Gateway would serve as a habitation module, scientific lab and communications hub. The US was finally going back to the Moon, but extensive preparations for Gateway were needed to identify an appropriate lunar orbit for the first space station that would ever orbit the Moon. The “Capstone” (Cislunar Autonomous Positioning System Technology Operations and Navigation Experiment) mission’s primary objective was to test and verify the calculated orbital stability of the Near Rectilinear Halo Orbit (NRHO) around the Moon – the orbit planned for Gateway.
It was calculated to give Gateway and spacecraft docking with it the best combination of fuel efficiency and a pathway to the lunar surface. As Nasa explained: “Hanging almost like a necklace from the Moon, NRHO is a one-week orbit that is balanced between the Earth’s and Moon’s gravity. This orbit will periodically bring Gateway close enough to the lunar surface to provide simple access to the Moon’s South Pole where astronauts will test capabilities for living on other planetary bodies, including Mars.”
The orbit also gives astronauts access to other landing sites around the Moon. A CubeSat [miniature satellite] would need to be launched into lunar orbit to gather data that would help Nasa decide exactly how to position Gateway.
Peter Beck had always been fascinated with interplanetary spaceflight. But Rocket Lab had to date been involved in putting spacecraft into orbit 400-550km above the Earth. Carrying a satellite beyond Earth’s orbit all the way to the Moon, over 384,000km away, was an entirely different job, and not one Peter was confident Electron could pull off.
He had earlier put master’s student and Rocket Lab intern Richard Hunter to work on a thought experiment to figure out how to use Electron to get a payload into orbit around Venus, a planet ripe for further scientific examination. When Nasa went looking for partners for Capstone, Peter asked him to run the numbers on a lunar orbit.
“It was literally applying some really simplified equations of motion to figure out how feasible it would be to modify Electron’s Kick Stage, launch it on an Electron rocket, and get something, albeit pretty small, to the Moon,” Richard remembered.
Beyond Earth’s Orbit
The initial feasibility study Richard conducted, was enough to convince Nasa to hand the job to Rocket Lab, which by that point had put numerous satellites in orbit for the agency.
“I got a call from Nasa headquarters at 3am and jumped up, super excited, punching the sky for the first 30 seconds,” said Peter. “Then, for like the next two and a half years, it was sheer pain and misery.”
From the beginning, the mission was ambitious. It required the design and development of a new orbital engine
(HyperCurie) and spacecraft (Lunar Photon) to propel the 37kg Nasa payload into a translunar trajectory. However, as the programme matured through detailed design, system complexity grew, mass increased and performance margins became negative, and significant modifications to Electron were required to make up the shortfall.
“Ultimately, the rocket that took off the pad lifted 705 pounds (320 kg),” said Peter. “There was no camera onboard, because we couldn’t spare seven ounces (200g). There was a three-hour argument about whether we could afford the mass of the Nasa sticker on the side of it.”
“As the project developed, we realised the system was more complicated than expected, which meant more weight. We needed to make the rocket more powerful, the batteries more efficient,” said Richard.
Rocket Lab’s experts combed through Electron’s components looking for ways to shed weight and extract more power. As they proposed tweaks, Richard fed them into computer simulations, running hundreds of different configurations to see which would get Electron and its precious cargo into a lunar orbit. The second-stage tanks were stretched, batteries upgraded and countless small optimisations were aimed at reducing weight.
Rocket Lab was initially given a tight 12-month deadline to prepare for Capstone. But it became clear the various modifications required would push out the timeframe. The Covid-19 pandemic also put pressure on Rocket Lab’s supply chain, leading to delays.
Desirée Brundin joined Rocket Lab as lead spacecraft systems engineer in August 2021 and was immediately assigned to work on the Lunar Photon for Capstone. She didn’t know what she had let herself in for. “I came here expecting everything to be done. I was worried that I would miss all the fun,” she said. “But there was no spacecraft. I was like, where is it?
Mission Creep
Delays in delivery of key parts and technical difficulties meant Desirée and her colleagues ended up undertaking assembly integration and testing of the Lunar Photon and the launch campaign and mission operations in less than a 12-month period. “It’s just crazy what we accomplished in so little time,” she said.
One of the key challenges the team faced was developing the HyperCurie engine, a major technological advancement over the original Curie engine Rocket Lab used to manoeuvre the Photon spacecraft. Unlike the pressure-fed Curie engine, the HyperCurie uses electric pumps to deliver propellant to the combustion chamber. This design choice eliminated the need for complex turbomachinery typically found in gas generator cycle engines, while allowing for more efficient operation in deep space. A typical Electron launch is complete within an hour from lift-off to payload deployment. For the Capstone mission, even after the initial launch to orbit on Electron was completed, Rocket Lab still had to operate the Photon spacecraft for six days in challenging conditions.
Unlike regular Electron launches to low-Earth orbit, which are automated once in flight, Richard Hunter knew that mission control would have to make adjustments to Photon’s path throughout the seven-day mission to the Moon. “With that level of complexity, you just couldn’t model it. We knew we would have to solve problems on the fly and send commands to the spacecraft in real time.”
The Super Manoeuvre
The Lunar Photon then performed a series of orbit-raising burns over six days, gradually increasing Capstone’s velocity. The plan was to perform eight burns, strategically timed to maintain sufficient momentum in space. But mid-mission, a worrying call came from mission control. Richard was home, about to go to bed after a 20-hour stint in mission control, when the phone rang.
“The propulsion team had been busy analysing telemetry from the spacecraft and spotted a problem,” he said. “We needed to limit the number of manoeuvres we were doing. They thought it would be less risky to combine the next two burns into one and limit the number of engine restarts. This required an off-script redesign of the mission sequence,” he explained.
The problem was that with each burn manoeuvre, the Lunar Photon’s propulsion system, powered by the HyperCurie engines, was getting hotter, the result of a chemical reaction in the fuel system coking up the engine system. “The next burn we did, it went five degrees above the thermal margin. And with the next burn it went five degrees above the margin again,” said Peter. “We had eight burns to do. The engine was going to explode on the last burn to the Moon. So, you know, that wasn’t going to work.”
The team again worked through the night to come up with a new plan dubbed the “super manoeuvre.” Rather than eight burn manoeuvres, the team would initiate seven to avoid damaging the engines, with one long burn considered to be much safer.
It was risky – the team hadn’t modelled that particular scenario. The longer the burn, the bigger the potential trajectory error, which could affect tracking and trajectory accuracy. But by the time Richard got to mission control the next morning, the whole new manoeuvre had been designed and was ready to upload to the Lunar Photon.
“I sat down in my chair and watched this 3280-feet-per-second [1000m/sec] burn go off. I was mentally prepared to run an emergency search pattern to track down and recover a lost spacecraft from non-deterministic orbit. I was like, ‘How did we get here in the space of one night?’”
But the improvisation paid off. When telemetry lit up after the super-manoeuvre, it confirmed that propulsion and GNC systems had executed flawlessly, and Lunar Photon remained on course. On July 4, 2022, Lunar Photon successfully completed the trans-lunar injection manoeuvre, a critical step that took Capstone out of Earth’s orbit and on a transfer trajectory to the Moon.
Another important mission milestone was marked. “We did that trans-lunar injection burn, and you know it was flawless,” said Peter. “Moreover, we had 13% propellant left in that vehicle.”
Capstone remains one of the proudest moments for Rocket Lab. “In a lot of respects, it just seemed impossible,” said Shaun O’Donnell, who had joined Peter all those years before with the simple goal of building and launching a small suborbital rocket. “We always challenge ourselves here, but Capstone seemed like a step too far. Like we have in the past, we pulled it off.”
“That was a tough mission,” admitted now deputy chief engineer Lachlan Matchett. “We had to really think out of the box, make everything as lightweight as we could, as highperformance as we could. We did an awesome job,” he said.
For Morgan Connaughton, who Peter tasked with livestreaming the final critical moments of the mission, it was both exhilarating and terrifying to watch. “At that point, I was so used to a launch lifting off and you’d be in orbit nine minutes later. An hour later the payload is deployed. This was six days of terror, because all of a sudden we’ve done the launch, but now we are operating the spacecraft.”
“We were very late on that mission, and we did that at a firm fixed price,” said Peter. “So we lost money on that mission. That was not a good economic mission for us. But that mission enabled us to win the Mars Escapade missions from Nasa.”
The experience was a baptism of fire for Desirée, but left her craving more. “I’m excited to do it all again. I think we should go to Venus and Mars,” she said. “Just launching with your own rocket is such a special experience, and you get so much flexibility. Not a lot of companies get to do that.”
