The future of in-space manufacturing
Hoisting heavy machinery into space is cumbersome and expensive. Soon, however, it won’t be a problem. Cathal O'Connell reports.
The great advantage of being a crew member in Star Trek was that you had “replicators” to create any object you needed, on demand. In today’s real world, everything needed for a space mission – from tools to food and medicine – has to be made on Earth then launched into orbit, and the huge cost of doing that restricts our exploration of the solar system. All that’s about to change, however.
Already companies are sending up 3D printers to produce replacement tools in space. Next we could see orbiting factories making products for sale on Earth or automated robots constructing satellites the size of a football field. Then there’s the potential to build habitats on other planets, using their natural resources, or to tap into asteroids to replenish Earth’s diminishing metal stocks.
These are the technologies that will graduate humanity from making temporary sorties into space to setting up a permanent presence there.
3d printing tools
Space agencies typically load manned missions with a crazy number of spare parts to cover every imaginable contingency – at a launch cost of around $14,000 per kilogram. On the International Space Station (ISS) these spares are worth an estimated $1.4 billion dollars. Most will never be used.
But what if there were a way to make almost any object in space, when it’s needed, or even to melt down a part after it has done its job and reuse the material for something else? We’re heading in that direction.
In 2014, US company Made In Space sent the first 3D printer to the ISS, where it was used to show that parts printed in microgravity are as strong as those printed on Earth.
Two years later, the company sent up its next generation printer, dubbed the Advanced Manufacturing Facility, and it has been providing a fabrication service to NASA and other experimenters ever since. To date it has focused on plastics, but the VULCAN system it has in the works will be able to print metals too.
Another US company, Tethers Unlimited, sent its 3D printer to the ISS on 15 November. The advantage of the Refabricator is that it can turn waste plastic, including abundant launch packaging filler, into 3D printing material, saving on the cost of sending up special printing filament.
Perhaps the most extreme idea along these lines is the recycling of human waste. Researchers at the University of Calgary in Canada are engineering bacteria to turn human waste into “astroplastic”, a 3D printing material called polyhydroxybutyrate.
The obvious challenge to overcome when making stuff in space is the lack of gravity. No gravity means no convection, and that messes with heat transfer. But what started out as a problem for Made In Space engineers might be the key to getting the first orbiting factory off the ground.High-quality optical fibre is vital for intercontinental communications and high-speed internet. Currently the internet and telecom industries are built on silica-based fibres, but another type of fibre based on fluoride glass and known as ZBLAN (from the elements Zirconium, Barium, Lanthanum, Aluminium and Sodium) is potentially far more efficient.
The problem is, on Earth at least, that convection induces tiny microcrystals to form in the ZBLAN, making it cloudy and less efficient.
In 1998 the US optical fibre maker Thorlabs tried to form ZBLAN material on the “vomit comet” – an aeroplane flight that mimics microgravity for a minute or so of freefall. And it succeeded. The ZBLAN fibres made in microgravity had far fewer microcrystals, and superior transmission.
Now, Made In Space has teamed up with Thorlabs to see if they can make high-quality optical fibre in space. Their fibre maker was launched to the ISS in December 2017 and is going through its first experimental run, with the potential to spool out four kilometres of fibre from just four kilograms of raw material. If it works, it will be the first time anyone has created a commercial product in space.
In the emptiness of space, ironically enough, astronauts live and work inside cans not much bigger than a shipping container. That’s because every module of the ISS, and everything else we send into orbit, is limited by the dimensions of the launch rocket.
But if we could build in space, we potentially could make gigantic structures that wouldn’t hold their own weight on Earth: more spacious space stations, telescopes the size of a football ground, or enormous satellites for harvesting solar energy. While the specialised parts, such as the lenses and solar cells, would still need to be made on Earth, the scaffold that holds everything together could certainly be fabricated and assembled in orbit.
One of the first examples of an orbital construction engineer is Made In Space’s Archinaut. This is basically a robotic assembly machine with an in-built 3D printer. The printer extrudes struts and connectors, which the arms click into place. It’s like space Lego. Currently Archinaut can work with NASA-approved high-strength plastics based on polycarbonate, which would be more than strong enough to hold together giant space structures in the low stress orbital environment. Archinaut has already proved itself in vacuum tests, in microgravity aboard the vomit comet, and is due to launch to the ISS in 2019.
Ultimately, even the raw materials for construction could come from space. Starting with Planetary Resources – which was established in the US in 2009 by investors including Google co-founder Larry Page and Virgin CEO Richard Branson – companies are springing up all over the world with their sights set on the untold riches beyond Earth. Their first step? Mining asteroids. And with investment firm Goldman Sachs predicting the world’s first trillionaire will make their coin in this new industry, it could become the gold rush of the 21st Century.
The obvious thing would be to find some convenient asteroid rich in precious metals such as gold or platinum. Unfortunately, although there are about 18,000 asteroids in orbits close to earth, only about 4% of these are likely have valuable metals. So, one of the biggest challenges facing the industry is the prospecting, which is why several companies, among them UK-based Asteroid Mining Corporation, are working on putting up satellites that will scan through space rocks in search of potential goldmines.
Other companies, including US-based Planetary Resources and Deep Space Industries, see the future not in precious metals, but in water. Besides hydrating thirsty astronauts, water can be easily turned into rocket fuel (oxygen and hydrogen) simply by running an electric current through it. By mining water from ice-rocks, these companies plan to set up fuelling stations for missions to the Moon, to Mars or deeper into space.
Of course, retrieving the material is easier said than done. So far only about one milligram of material has ever been returned from an asteroid – the few grains of dust collected by the Japanese Hayabusa spacecraft in 2010. In 2016, NASA launched the OSIRIS REx spacecraft on a seven-year mission to the asteroid Bennu. If all goes to plan, it will return about 150 grams of material.
But NASA’s bigger plan – to capture and return a 50-metre asteroid to orbit around the moon – was shelved by the Trump administration. Physicists at California Institute of Technology have estimated such an “asteroid return” mission would cost about $3.6 billion. That’s a lot of cash, but still not too far off the set-up costs for a mine on Earth, especially considering a nicely chosen rock could contain tens of billions of dollars’ worth of resources. The biggest problem might be the economic law of supply and demand; returning with thousands of tonnes of gold or platinum could crash the market, with once precious metals becoming cheap as chips.
Off-world habitat building
Could we send giant 3D printers to the Moon or Mars to build?
The first 3D printed houses have already been constructed here on Earth. At their simplest, these huge printers look like cement mixers with a robotic arm that manipulates a nozzle to extrude the construction material in layers. Some researchers are already developing ways to swap out the sand typically used in cement with Mars or Moon dust. In 2014, Italian researchers showed they could build large structures using material similar to lunar regolith (the layer of material covering solid rock).
NASA, meanwhile, is funding a competition for autonomous robots that can collect, refine and 3D print habitats on other worlds. The final round, a head-to-head “print off” with a $2.8 million prize purse, will be held in April 2019.
Even covering a prefabricated structure with a layer of packed regolith could help protect future colonists from radiation, small meteor strikes or dust storms. The European Space Agency envisages sending a rover to roll around the lunar surface, scooping up regolith and mixing it with a binder. The rover would then pack the material on top of an inflated habitat, a bit like how you might bury someone in sand on the beach, reinforcing the structure before any people arrive.
As they say in the space construction industry, the difference between going camping and settling are the tools you bring with you.