A critical design review occurred in April for the communications antenna ESA is supplying for NASA’s Habitation and Logistics Outpost (HALO) on the Gateway. Time to catch up with ESA’s Esprit project lead Luca Stagnaro on this milestone.
Gateway blueprint showing all modules. Credits: ESA
Luca is responsible for both elements that make up Esprit, the Esprit HALO lunar communications system (known as Esprit-HCLS), and the European refuelling module. As the antenna will be launched first, as part of HALO, the antenna needs to be ready and built beforehand. Like all space hardware it needs to pass a “critical design review” where all parties agree on the design and its implementation. From this review onwards the design is set and production can begin.
Mouse ears
The Esprit communications system consists of two antennas that can rotate and swivel independently. The double antenna design is needed because the Moon is set to become a busy place and in the near future Esprit might need to track rovers on the lunar surface while communicating with an approaching Orion spacecraft coming in for docking with the Gateway – at the same time! The communications system is also set to support ESA’s Argonaut as it lands on the Moon, relaying live video possibly together with the ESA’s Moonlight navigation and communications system.
A view of Gateway’s first two elements – the power and propulsion element (PPE) and the habitation and logistics outpost (HALO). The two elements will be launched together. The Esprit communications system is visible on the front left. Credits: NASA
The meeting in April involved NASA, ESA and industry engineers carefully reviewing the plans to ensure that the final design is fully compliant to the needs of Gateway. All aspects of the communication system are considered, from their size and mass to energy consumption, reliability, communication system and delivery time. This type of review is a milestone for everybody involved because it verifies the system can perform as planned and can withstand the environmental conditions expected.
A positive outcome of the review authorises the start of building the flight model as the tests and calculations will have shown the system is as intended. The review passed and the hardware pieces are all good to go to the next steps, but one item that still being discussed is on the software side – which internet protocol to use on the Moon?
Esprit HALO communications antenna design.
Luca explains, “the vast majority of ESA spacecraft talk directly to ground control and they are not part of a network, like the computers and printers at home are. We are expecting hundreds of missions around the Moon in the coming years and we need to define a system that makes communication between each other possible, a sort of lunar internet. We know exactly how internet works, and I even have the ‘bible of the internet’ on my desk, but how do we apply this idea for an ‘internet for the Moon’, that doesn’t exist… yet?
“During this review we discussed with NASA how to extend the Gateway internal network externally so astronauts and rovers on the Moon can interact with computers on the Gateway, similarly to how your laptop at home communicates with servers around the world. HLCS will do what your home wi-fi router does when it connects home computers with the rest of the internet.”
Any changes to be made here are in the software part of HLCS. Luca explains, “as we progress and decide on protocols with the international partners, any changes to the software would be a limited software update, while on the hardware side, we have a robust system that can offer encrypted data transfer rates of up to 25 Mb/s, enough for 4K streaming from the Moon!”
Moon surface scenario showing Argonaut and Gateway in orbit. Credits: ESA
Xenon fuel, windows and size matters
The European Refuelling Module (ERM) also falls under Luca’s purview and is set to launch on the Artemis IV mission, towed into position by the Orion spacecraft that is powered by the European Service Module. The design of the refuelling module is at an earlier stage and has its preliminary design review still in front of it. The Esprit module’s main tasks are to bring supplies to the Gateway, store them and allow for fuel transfer to keep the Gateway and spacecraft fuel tanks topped up. As the critical design review is still to come, ERM’s scope can still be adjusted to fit the needs of Gateway.
Zoom on the Esprit refuelling module as part of Gateway. Credits: Thales
The Esprit refuelling module will also provide windows to Gateway, which is very important for the astronauts and for the operations of the lunar outpost. “As expected there are many details that we are still defining and agreeing with the rest of the Gateway partners leading towards the preliminary design review,” says Luca.
Esprit will bring additional fuel to Gateway, which uses xenon for its massively powerful electric ion thrusters. Ion thrusters have distinct advantages for spaceflight, as traditional chemical thrusters, like those we see on rockets, would require up to 20 times more fuel to be sent to the Gateway. “The xenon refuelling aspect is at the forefront of what is technologically achievable, as no pump for xenon exists yet,” says Luca, “but with the technology developed for Esprit, ESA will put itself well ahead on this aspect of space propulsion and refuelling, which will be the key to allow humans to travel between planets.”