The Hubble Space Telescope was carried to space inside the space shuttle Discovery and then released into low-Earth orbit. The James Webb Space Telescope was squeezed inside the nose cone of an Ariane 5 rocket and then launched. It deployed its mirror and shade on its way to its home at the Sun-Earth L2 Lagrange point.
However, the ISS was assembled in space with components launched at different times. Could it be a model for building future space telescopes and other space facilities?
The Universe has a lot of dark corners that need to be peered into. That’s why we’re driven to build more powerful telescopes, which means larger mirrors. However, it becomes increasingly difficult to launch them into space inside rocket nose cones. Since we don’t have space shuttles anymore, this leads us to a natural conclusion: assemble our space telescopes in space using powerful robots.
New research in the journal Acta Astronautica examines the viability of using walking robots to build space telescopes.
The research is “The new era of walking manipulators in space: Feasibility and operational assessment of assembling a 25 m Large Aperture Space Telescope in orbit.” The lead author is Manu Nair from the Lincoln Centre for Autonomous Systems in the UK.
“This research is timely given the constant clamour for high-resolution astronomy and Earth observation within the space community and serves as a baseline for future missions with telescopes of much larger aperture, missions requiring assembly of space stations, and solar-power generation satellites, to list a few,” the authors write.
While the Canadarm and the European Robotic Arm on the ISS have proven capable and effective, they have limitations. They’re remotely operated by astronauts and have only limited walking abilities.
Recognizing the need for more capable space telescopes, space stations, and other infrastructure, Nair and his co-authors are developing a concept for an improved walking robot. “To address the limitations of conventional walking manipulators, this paper presents a novel seven-degrees-of-freedom dexterous End-Over-End Walking Robot (E-Walker) for future In-Space Assembly and Manufacturing (ISAM) missions,” they write.
An illustration of the E-walker. The robot has seven degrees of freedom, meaning it has seven independent motions. Image Credit: Mini Rai, University of Lincoln.
Robotics, Automation, and Autonomous Systems (RAAS) will play a big role in the future of space telescopes and other infrastructure. These systems require dexterity, a high degree of autonomy, redundancy, and modularity. A lot of work remains to create RAAS that can operate in the harsh environment of space. The E-Walker is a concept that aims to fulfill some of these requirements.
The authors point out how robots are being used in unique industrial settings here on Earth. The Joint European Torus is being decommissioned, and a Boston Dynamics Spot quadruped robot is being used to test its effectiveness. It moved around the JET autonomously during a 35-day trial, mapping the facility and taking sensor readings, all while avoiding obstacles and personnel.
The Boston Dynamics Spot robot spent 35 days working autonomously on the Joint European Torus. Here, Spot is inspecting wires and pipes at the facility at Culham, near Oxford (Image Credit: UKAEA)
Using Spot during an industrial shutdown shows the potential of autonomous robots. However, robots still have a long way to go before they can build a space telescope. The authors’ case study could be an important initial step.
Their case study is the hypothetical LAST, a Large Aperture Space Telescope with a wide-field, 25-meter primary mirror that operates in visible light. LAST is the backdrop for the researchers’ feasibility study.
LAST’s primary mirror would be modular, and its piece would have connector ports and interfaces for construction and for data, power, and thermal transfer. This type of modularity would make it easier for autonomous systems to assemble the telescope.
LAST would build its mirror using Primary Mirror Units (PMUs). Nineteen PMUs make up a Primary Mirror Segment (PMS), and 18 PMSs would constitute LAST’s 25-meter primary mirror. A total of 342 PMUs would be needed to complete the telescope.
This figure shows how LAST would be constructed. 342 Primary Mirror Units make up the 18 Primary Mirror Segments, adding up to a 25-meter primary mirror. (b) shows how the center of each PMU is found, and (c) shows a PMU and its connectors. Image Credit: Nair et al. 2024.
The E-Walker concept would also have two spacecraft: a Base Spacecraft (BSC) and a Storage Spacecraft (SSC). The BSC would act as a kind of mothership, sending required commands to the E-Walker, monitoring its operational state, and ensuring that things go smoothly. The SSC would hold all of the PMUs in a stacked arrangement, and the E-Walker would retrieve one at a time.
The researchers developed eleven different Concept of Operations (ConOps) for the LAST mission. Some of the ConOps included multiple E-walkers working cooperatively. The goals are to optimize task-sharing, prioritize ground-lifting mass, and simplify control and motion planning. “The above-mentioned eleven mission scenarios are studied further to choose the most feasible ConOps for the assembly of the 25m LAST,” they explain.
This figure summarizes the 11 mission ConOps developed for LAST. (a) shows assembly with a single E-walker, (b) shows partially shared responsibilities among the E-walkers, (c) shows equally shared responsibilities between E-walkers, and (d) shows assembly carried out in two separate units, which is the safer assembly option. Image Credit: Nair et al. 2024.
Advanced tools like robotics and AI will be mainstays in the future of space exploration. It’s almost impossible to imagine a future where they aren’t critical, especially as our goals become more complex. “The capability to assemble complex systems in orbit using one or more robots will be an absolute requirement for supporting a resilient future orbital ecosystem,” the authors write. “In the forthcoming decades, newer infrastructures in the Earth’s orbits, which are much more advanced than the International Space Station, are needed for in-orbit servicing, manufacturing, recycling, orbital warehouse, Space-based Solar Power (SBSP), and astronomical and Earth-observational stations.”
The authors point out that their work is based on some assumptions and theoretical models. The E-walker concept still needs a lot of work, but a prototype is being developed.
It’s likely that the E-walker or some similar system will eventually be used to build telescopes, space stations, and other infrastructure.