Space exploration is moving into a new dimension. Once again attention is being drawn to new possibilities which technology is rapidly allowing to become a reality.
NASA is collaborating with commercial and international partners on the Artemis mission which will establish a long-term base on the Moon by 2024. This will allow new research that will help inform scientists looking to send astronauts to Mars.
The use of additive manufacturing (AM) is at the heart of the Artemis mission with 3D printing being used to produce rocket parts, for example.
NASA has set up the Rapid Analysis and Manufacturing Propulsion Technology project (RAMPT) which will produce these parts with metal powder and lasers using a pioneering method known as blown powder directed energy deposition.
This cuts lead times on parts production by at least 50 per cent there is a tenfold reduction in lead times with parts that would have taken up to nine months to make before now being done in a matter of days. It also potentially lowers the cost of very large components such as nozzles and combustion chambers, the production of which would not have been possible using conventional 3D printing.
The process involves metal powder being injected into a laser-heated pool of molten metal or melt pool. The blown powder nozzle and laser optics are integrated into a print-head. This is then attached to a robot and moves in a pattern determined by a computer building one layer at a time.
Paul Gradl, RAMPT co-principal investigator at NASA's Marshall Space Flight Center, said: “Blown powder directed energy deposition additive manufacturing allows us to create very large-scale components with complex internal features that were not previously possible. We’re able to significantly reduce the time and the cost associated with the fabrication of channel-cooled nozzles and other critical rocket components."
“We can do a lot of things with additive manufacturing that we couldn’t do even two years ago. It’s an exciting time because we’re advancing at such a rapid rate. It really has been a game changer.”
Extreme temperatures
Hot fire testing is now taking place on full scale models of rocket engines to see whether 3D printed parts can stand the rigors of space, particularly the extreme temperatures and pressure needed for rocket propulsion.
Last November, 23 rigorous hot fire tests were carried out on a copper alloy combustion chamber and nozzles made of a high-strength hydrogen resistant alloy. The main combustion chamber experienced pressures up to 750 pound-force per square inch and hot gas temperatures approaching 6,200 degrees Fahrenheit.
Ultimately NASA is looking at transitioning from traditional manufacturing to AM although there is still some way to go before fully AM rocket engines are powering spacecraft.
More data must be produced through testing to ensure the properties of the new metals can perform safely and reliably. NASA is also keen to ensure the new processes are accessible through the supply chain and is working with smaller companies on their development efforts with the research being shared to build up the database.
Robotic assembly
NASA isn’t alone in development. Part of the recent advances in the space are coming from smaller companies and academia and we’re not just talking Elon Musk’s SpaceX and Sir Richard Branson’s Virgin Galactic which are pushing commercial space travel.
Through an agreement with Auburn University in Alabama, RAMPT collaborates with specialty manufacturing firms already advancing the "state of the art" bolstering their work and making the technologies developed by this team available widely to the private sector.
An example is a company called Made in Space. Founded in 2010, it was the first to additively manufacture in space and over the last six years has carried out 3D printing on the International Space Station.
This has now been scaled up significantly with work on a spacecraft called OSAM-2 which it is jointly developing with NASA. Once launched as early as next year, it is designed to combine AM robotic assembly to build large, complex structures in space as well as repairing existing satellites.
The advantage of manufacturing in space is that it cuts out the need and cost of launching components from Earth and complex structures of indefinite lengths can be produced using thermoplastics. A demonstrator has been designed to 3D print two beams stretching 33 feet from its sides.
Then, OSAM-2 will deploy simulated solar sails which it is hoped will generate five times more power than traditional solar panels. If it works, this tiny one-robot space factory will show it’s possible to cut costs and seriously reduce the risks of carrying prebuilt cargo to space.
A wide range of applications for this technology are being predicted including orbiting telescopes in space to building on-the-spot structures like power grids, radar booms, and fuel depots – ideal for missions such as Artemis.
Eric Fox, chemistry and construction team Lead at NASA, said: “The ability to print parts away from the Earth is incredibly important. The energy costs of a mission from the Moon to Mars are approximately the same as from the Earth to the Moon.
“It is such an enabling technology for space exploration and in the last five years development has taken place at a sprint.”
Moon dust
With the focus now firmly set on setting up a base on the Moon from which future exploration can be carried out, further attention is being given to how people can live on the planet.
In-situ resource utilization (ISRU) - the use of local resources to reduce up-mass, cost and risk of the mission – is key to this. The most readily available local resource on the moon is its layer of crushed rock or regolith on the surface.
It has a high metallic oxides content from which oxygen can be produced to sustain human life while it can also be used as a construction material for roads, launch pads and habitats. Proof of concept of a custom solar 3D printer capable of sintering building elements using only lunar regolith has been advanced by the ESA while a pilot plant for producing oxygen is expected by the late 2020s.
It has also awarded £250,000 of funding to British firm Metalysis to carry out this process with an initial proof of concept resulting in a metallic powder where 96 per cent of the total oxygen has been successfully extracted giving a mixed metal alloy product that can be used for in-situ manufacturing.
Ian Mellor, managing director of Metalysis, said: “We are taking an established Earth-based technology and applying it to a lunar setting. Doing this in situ means we don’t have to take so much raw material from Earth, being able to harness the resources of the Moon which will be beneficial for future space travel.”
The possibilities of space exploration are growing on an almost daily basis with a plethora of small firms such as Metalysis continuing to push the envelope.
In the UK, the Satellite Applications Catapult (SAC), a partially government-funded organisation supporting the growth of the space sector, provides facilities and equipment for shared use by these businesses. For example, it recently commissioned a MetalFAB1 3D AM machine built by Dutch-based Additive Industries for the Westcott Venture Park in Buckinghamshire to be used for the likes of printing rocket engine parts.
Mike Curtis-Rouse, head of manufacturing for Space at SAC, said: “The surge in the number of companies aspiring to build and support new launch vehicles and in-space propulsion continues to grow. This new capability will ensure that UK SMEs can access the latest in AM technology to accelerate their businesses.
“This machine can build parts in a way that engineers and technologists in the last 50 years could only dream of.
“We look forward to creating a hot-bed of testing and development to build capacity for any new or existing UK space manufacturing enterprises.”
