3D Printing in Space: An Introduction

In the last decade, the use of 3D printing in many fields has rapidly increased, and Earth-based sectors such as the automotive and aeronautic industries have taken advantage of the many benefits the technology has to offer.

However, one sector that has pushed 3D printing to its limits has been the space industry. From base building on Mars to printing artificial hearts in zero gravity, 3D printing technology is at the forefront of human exploration of the final frontier.

Cutting Weight

Launching objects to space is a slow and expensive endeavour. Despite modern companies such as SpaceX using state-of-the-art reusable rocket technology to bring costs down, it still costs thousands of pounds per kilogram to get payloads into space. Annually, 3,000kg of equipment is sent to the International Space Station (ISS) per year, with over 13 tonnes of backup equipment stored onboard for redundancy. Considering that NASA estimates that only 5% of these spare parts will actually be used, this is clearly inefficient.

Not only is this expense significant, but it is also impractical for more distant missions; a 6 – 9-month journey to Mars would require a lot more equipment and redundancy, and would not be able to carry the same amount of spare components or receive annual supplies from the Earth.

However, if you had the ability to make and recycle the tools you needed during the flight, you could greatly reduce the amount of spare equipment you would need to bring with you, leaving more room for necessary supplies such as food. This is where 3D printing comes in.

In Situ Component Manufacture

In 2014, the first-ever tool to be manufactured from an uplinked file in space (a socket wrench) was printed in ABS using the Fused Filament Fabrication (FFF) process. After testing the part back on Earth, it was found to have negligible differences to an equivalent printed on land, demonstrating the effectiveness of the method.

Since then “Made In Space”, the company behind this historical first, have made further advancements and launched another 3D printer to the ISS; the Additive Manufacturing Facility (AMF), which has been in use since 2016. The AMF provides the capability to print in multiple different materials, including ABS and High-Density Polyethylene (HDPE), and has allowed many organisations to test their 3D printed designs in space.

Since then, another project called “ReFabricator” arrived at the ISS. This project aims to recycle plastic printing material while avoiding the damaging shear caused by grinding pellets. This has moved us one step closer to being able to use waste plastic as a material for critical applications both on Earth and in Space.

3D Printing Space Metal

In addition to these polymer-focused 3D printing techniques, metal 3D printing has been looked at intently. Many critical components in space are made of metals such as aluminium and titanium. On Earth, one of the most common methods used is Selective Laser Melting or SLM. Here, a laser is utilized to melt selected areas of metal powder to build up components additively.

However, these types of machine are not suitable for use in space in their current form. SLM requires a lot of power to run and uses powders which are flammable, hazardous to breathe in and difficult to control in microgravity.

To overcome these issues, NASA is currently investigating several cutting-edge methods:

• Use of ultrasonic waves to connect adjacent layers of metal foil.
• Wire and arc-based methods to join layers of metal wire in a manner similar to welding
• Bound metal deposition methods that make use of filament or metal particle pastes bound within polymer.

Researchers at the German Federal Institute have also looked into using a specific type of “binder jetting technology”, where gravity is replaced by powerful jets of air to keep the metal powder in place.

Space Structures

As well as printing inside a space vehicle, 3D printing also has many exciting applications outside in the vacuum of space. Made In Space, Northrup Grumman and Oceaneering Space Systems are collaborating on NASA’s ‘Archinaut’ project, which is looking to use additive manufacturing technology to build large structures in space.

Following successful ground-based testing, the first orbital test to be launched to space will be Archinaut One. This will use 3D printing methods to build a solar array in orbit. If this is successful, the result could be lighter (and therefore cheaper) satellite payloads that can build components for themselves once in orbit.

Homes on Other Planets

In addition to manufacturing in orbit, organizations such as NASA and the ESA are also looking into building structures on the surface of Mars and the Moon using 3D printers. Instead of carrying heavy building materials out of the Earth’s gravity well, scientists have studied using a key material that already exists on these bodies; regolith.

Regolith is the soft layer of dust, soil and rubble that covers rocky planets and moons. It is the result of millions of years of asteroid impacts and high energy radiation breaking up the surface rock. Scientists propose that buildings could be made with this material.

This won’t be easy. One of the issues with using regolith for 3D printing is that it is a difficult substance to work with. On Earth, perpetual motion has weathered sand over thousands of years until its grains have become smoothed out and rounded. Comparatively Regolith has had very little weathering occur due to a lack of atmospheric motion. This means the grains of regolith are very sharp and result in a highly abrasive substance. This can quickly wear out nozzles, clog up moving parts and cause a lot of damage to any printers that try to print with it.

However, despite the difficulties of working with lunar regolith, and the general hazards of printing in microgravity, extreme cold and under ionizing radiation, scientists at NASA’s Granular Mechanics and Regolith Operations Lab (GMRO) strongly believe it is a viable method. To develop the printers, engineers use a substance called Black Point 1, a waste by-product of asphalt production that shares many similar properties with regolith.

Summary

3D printing is allowing significant advancement in capability outside the Earth’s atmosphere. The space industry is developing cutting edge solutions to some of the toughest challenges facing additive manufacturing.

To learn more about some of the cutting-edge solutions available now on back here on Earth, click here.