How Virtus Solis plans to build a solar power plant in space

In 2027, if all goes to plan, a couple of car-making robots dressed in “space suits” and attached to a free-flying satellite bus will assemble a 28-meter-wide solar power plant in Earth’s orbit. The plant will consist of 217 hexagonal photovoltaic modules, each 1.65 meters wide, that click together like a honeycomb. The assembly will produce 100 kilowatts of clean solar energy and beam it to Earth.

That’s just the demonstrator. Three years later, Michigan-based start-up Virtus Solis hopes to build its first commercial-scale power station—1,000 times as large as the demo and capable of generating 200 megawatts.

Depiction of how Virtus Solis plans to build its solar array in space. (Image: Virtus Solis.)

Depiction of how Virtus Solis plans to build its solar array in space. (Image: Virtus Solis.)

What will this project cost? NASA, in a report on space-based solar power published in January this year, concluded that made-in-space electricity will be rather expensive—12 times the cost of Earth-based photovoltaics. A 2022 study by Frazer-Nash Consultancy on behalf of the European Space Agency concluded that a first-generation commercial-scale space-based solar power plant would come with a price tag of at least €9.8 billion ($10.7 billion).

Virtus Solis CEO and ex-SpaceX rocket engineer John Bucknell thinks his company can pull it off for less than $1.5 billion.

Bucknell, who founded Virtus Solis in 2018, thinks he can achieve the ambitious price tag and the even more ambitious timeline by applying a combination of principles from automotive mass manufacturing, a field in which he worked for three decades, and SpaceX-inspired experimentation.

Car-making robots in space suits

The robots that will assemble Virtus Solis’ solar power plant are commercially available Kuka KR6 robots used in car making all over the world. Virtus Solis’ partner company Orbital Composites modified these robots for use in space. Weighing 52 kilograms each, the robotic arms will be dressed in custom-made space suits resembling a corrugated tube to protect them from cosmic radiation and extreme temperatures. The platform that will carry the robots is the existing 470-kg ESPAStar satellite bus made by Northrop Grumman that is commonly used to host technology demonstrators and experimental payloads.

The end-effector—the gripping mechanism that will take the satellite modules out of the rack after deployment from the rocket and click them together in space—is the only part of the robot that Virtus Solis is designing in-house.

“Moving the arm is easy,” Bucknell told “But designing the end-effector that grabs the satellites is tricky. How do you pick up a big flat piece in space? Vacuum doesn’t help. You can’t just put a sucker on it. You need to be able to grab it and pick it up and do it in such a way that is convenient, fast and robust.”

The team is using a combination of simulations and hardware experiments to find the best solution. Bucknell said that the complexity of the task at hand makes it difficult to find a single piece of software that would perfectly meet the designers’ needs. To find the right design, the engineers are using a plethora of tools including Siemens NX, Simulink, Kuka’s simulation tools and custom software.

“The existing, commercially available tools are designed for different applications, so we have our own software engineers who can build some sort of a bridge between the tools we have and those we would need,” said Bucknell.

Design, build, test, design, build, test

Ultimately, Virtus Solis will build physical models of the end-effectors and test them with their robots on mock-up satellite modules to make sure the technology works as intended before the costly trip to space.

“We have candidate solutions, but we don’t have the final one yet,” said Bucknell. “The only way to understand whether or not we have designed something that works is for us to try it.”

Virtus Solis’ demonstration transmitter in 2023. (Image: Virtus Solis.)

Virtus Solis’ demonstration transmitter in 2023. (Image: Virtus Solis.)

Bucknell said that to achieve the fast progress needed to meet the ambitious timeline, Virtus Solis is employing the same experimental approach used by SpaceX that involves rounds of simulations, building physical hardware, testing, fine-tuning in simulations, rebuilding and testing again, over and over.

“The reason you go to hardware as quickly as you can is to close the gap between your assumptions and reality,” said Bucknell. “It’s not the most capital efficient way but it’s certainly the fastest timescale. If you have the money, you’d better build, test and study the problem. You become an experimentalist if you want to move fast.”

Space is like air hockey

Virtus Solis engineers will ultimately want to assemble the entire demo power plant in a ground-based lab to test the interaction between the robots and the satellites. They will use an air table, a larger version of the frictionless tabletop used in the game of air hockey, to allow the robots to move the mock-up satellite modules without friction to mimic floating in weightlessness.

“The biggest one that we have today is a granite block about four feet by eight feet,” said Bucknell. “We are building small mock-ups of our satellites and small robot arms that could fit there and test it lots of times until we’re confident that it works.”

Bucknell says that despite the power of modern digital design and simulation tools, complex processes involving gripping and moving objects by robots can’t be recreated digitally with fidelity. The engineers will have to test everything, including the robots’ autonomous navigation system based on radar and lidar sensors that enable the robots to safely approach the satellite modules and put them together piece by piece.

“Once you have the end effector and the robot arm, it’s usually faster to test interfaces with hardware models because you don’t know how tightly to grip and how to do the orientation,” said Bucknell. “So, you do some initial work with simulation and then, once you have a better idea, you try to test with hardware as fast as you can because you don’t know what’s really happening until you do it for real.”

Eventually, the experiments will move to an air table large enough to accommodate an experiment as large as the demo solar power plant.

The sun always shines in space

Virtus Solis and Orbital Composites announced their partnership in February this year. The demo mission, Bucknell said, will cost $25 million. Only about 4 kilowatts of the 100 kilowatts produced will reach the ground, transmitted via microwaves. But the energy transfer efficiency will improve once the larger orbiting solar farm is in place, Bucknell told, as it depends on the size of the power transmitter.

Bucknell’s optimism about the project is partly driven by SpaceX’s progress in the development of Starship. The mega-rocket is the main enabler of space-based solar power, Bucknell says, as it will drive down cost of launch enough to make space-based solar power competitive with, for example, ground-based nuclear power generation.

Illustration of a space-based solar power station. (Image: Virtus Solis.)

Illustration of a space-based solar power station. (Image: Virtus Solis.)

Proponents think space-based solar power is the perfect answer to the world’s energy needs. Prices of photovoltaic panels have dropped by 90% over the past 15 years, according to the International Renewable Energy Agency, making solar power the cheapest source of energy available to humankind. But the sun doesn’t shine at night, and the panels produce less on cloudy days. Wind power stations contend with similar problems. Grid operators therefore need baseload power plants that can be switched on when needed. Coal and gas fired plants and nuclear power stations currently serve this purpose. But burning coal and gas produces carbon emissions, which the world needs to eliminate. Nuclear power has its own problems with dangerous waste.

Because the sun always shines in space, a space-based power plant with a correctly selected orbit could provide a constant source of electricity. Government agencies around the world from regions including China, Japan and Europe are exploring the idea of beaming solar power from space. Virtus Solis thinks they can make it work faster, better and cheaper.