For about three minutes, Mariam Alhammadi waited in front of a small glass window. Inside the vacuum chamber, almost all the air had been removed to recreate the conditions of space. Xenon gas had been fed into an electric thruster and a signal sent to its power system. Then came the wait.
“There's this three-minute window between when you pump in the gas and you send a signal,” Alhammadi recalled. “Watching it through the glass and seeing that blue colour come out of the thruster means that it actually worked. It’s always fascinating to see it.”
That blue glow comes from ionised xenon being accelerated out of the thruster. The force it produces is tiny. “We always say it’s like putting a sheet of paper on top of your hand,” she said.
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Yet this gentle push forms part of the solar electric propulsion system that will help carry the UAE’s MBR Explorer through an approximately five-billion-kilometre journey across the Solar System.
Unlike chemical propulsion, which produces large bursts of force while consuming much more propellant, electric propulsion can apply a far smaller thrust efficiently over long periods. Alhammadi, an electric propulsion engineer on the Emirates Mission to the Asteroid Belt, said that difference makes the system particularly suited to a journey of this scale.
NASA’s Psyche asteroid mission uses the same broad principle, accelerating xenon ions with electric and magnetic fields to generate a small but persistent force over long periods in deep space. NASA says the thrust from Psyche’s system is roughly comparable to the weight of an AA battery resting on a hand.
For the UAE mission, however, generating thrust is only the beginning of the problem. This week, the UAE unveiled a separate landing probe that will be carried aboard MBR Explorer and eventually descend to 269 Justitia. The probe has reached flight-readiness stage and is due to travel to Colorado for final integration with the main spacecraft ahead of a planned March 2028 launch.
MBR Explorer itself is expected to use gravity assists around Venus, Earth and Mars, encounter six asteroids and ultimately reach Justitia in 2036.
For the engineers building it, that creates another question entirely: how do you test something today that still has to work years from now, when there will be nobody there to fix it?
Engineering for what you cannot know
When asked about the hardest engineering problem she has faced on the mission, Alhammadi did not point to a particular engine or component.
She said it was uncertainty. “I think, on a personal level, working with uncertainties is what’s the hardest part of it,” she said. “It is imagining what could go wrong.”
That means questioning how much propellant will really be consumed, whether a thruster expected to produce a particular force will deliver exactly that, how temperatures inside the tanks may change and how uncertainties in different spacecraft systems interact.
“You take in all the information that you know about your system and all the different subsystems that play a role,” she said, before ultimately translating those uncertainties into the margins the spacecraft will carry.
Testing therefore happens repeatedly and at different levels. A UAE technical paper on the solar electric propulsion programme describes component tests, leak and pressure testing, thermal assessments, module-level testing and further checks following environmental qualification before the spacecraft is eventually fuelled for launch.
Space missions are designed around the knowledge that hardware cannot simply be brought back into a workshop. “If you fly this, this is not coming back,” Alhammadi said.
Software can sometimes be updated after launch. Hardware is different. Where possible, systems are built with redundancy. Mission planners also study fallback scenarios in advance.
Alhammadi said that, in a serious propulsion problem, one possibility could even involve dropping some planned asteroid encounters and adapting the mission around what remains operational. “You cannot repair it, but you also have plans for it in order to get a success criteria that works for you and for what is already operational on a spacecraft,” she said.
Dr Elias Tsoutsanis, Chief Researcher at TII’s Propulsion and Space Research Center, said the scale of EMA makes that preparation particularly demanding.
According to him, the mission involves around 40 manoeuvres compared with five for the Emirates Mars Mission, while travelling almost ten times farther. “We’re talking about a five-billion-kilometre journey in deep space,” he said. “So it’s super exciting and super challenging at the same time.”
The spacecraft must also survive dramatically different thermal environments while keeping electronics and other systems reliable throughout the journey.
“We cannot build the system and then think about the autonomy after we have built it,” Tsoutsanis said. “Reliability, autonomous operations and also extensive testing are integral parts of the programme from the beginning.”
A capability that did not exist here before
The engineering challenge is also changing what can be done inside the UAE. “Electric propulsion did not exist in the UAE as a capability before EMA,” Alhammadi said.
She had studied mechanical engineering before moving into space systems and electric propulsion, a field she said required her to learn unfamiliar areas including electrical engineering and electromagnetism. “I had no clue what electric propulsion was,” she said. “I knew I wanted to bring this back.”
TII has since developed specialist infrastructure in Abu Dhabi for electric propulsion work. Alhammadi said the centre now has two large vacuum chambers and a smaller chamber for electronics and power-processing systems, allowing engineers to test propulsion hardware in environments that reproduce some of the conditions it will experience in space.
A UAE Space Agency research paper describing the facility says it was designed around three vacuum chambers, specialised diagnostics, thrust measurement, clean rooms and engineering workshops, creating infrastructure for research, development and testing of electric propulsion systems in the country.
The wider change, Tsoutsanis argues, is not only about facilities. Four years ago, he said, responsibility for developing a system such as the UAE-built landing probe would probably have gone elsewhere.
“This would most probably be outsourced, be given to another partner, another collaborator in another country,” he said. Instead, UAE-based teams progressed from contributing personnel to the wider mission to being given responsibility for designing, assembling and testing a complete deep-space probe.
“We were given a real system design and engineering task to perform in the UAE,” Tsoutsanis said. “Then now we just completed our extensive testing. The testing for environmental conditions is really challenging, so this is where it actually feels real.”
The mission is part of a broader push to turn space programmes into industrial capability. The UAE’s National Space Strategy 2031 aims to double space-economy revenues, increase the sector’s economic added value by 60 per cent and expand national companies, infrastructure and exports.
TII has also been developing propulsion beyond EMA. In February, it launched the UAE's first domestically designed and tested hybrid propulsion sounding rocket, which reached an altitude of around three kilometres.
From participating to building
For Alhammadi, the progression is easiest to understand by comparing the UAE’s interplanetary missions. “When we started with the Emirates Mars Mission around 10 years ago, the idea was that the UAE just wanted to be part of this,” she said. “The next mission, which is EMA right now, is the UAE wants to be building it now. And inshallah, the next one is going to be us leading it.”
Tsoutsanis sees the same transition. Engineers who participated in earlier missions are taking on larger responsibilities today, he said, while the national team has grown in both numbers and technical depth.
For him, reaching Justitia in 2036 would be an extraordinary operational achievement. But part of the mission’s purpose, he argues, has already been achieved. “The mission is already a success in the sense that we have developed the talent in the country and the national capability,” he said. “Not only to explore space, but also to develop the people.”
Alhammadi puts it more personally. “We are basically the first generations that are making this happen.”
The spacecraft still has years of testing, launch and deep-space travel ahead of it. But long before MBR Explorer reaches an asteroid, some of the mission’s most lasting hardware may be the knowledge, people and facilities it leaves behind on Earth.