Article by Richard Arundal (2016)
On-orbit operations (such as manufacturing) could revolutionise the way space is used and enable new space mission concepts. Designing a mission concept that utilises high power lasers in space for use as manufacturing tools will test the feasibility of basic manufacturing operations such as cutting and joining. Applying these concepts to manufacturing space structures is complex and will no doubt take significant time to investigate and develop.
With laser welding and laser cutting processes, the potential for extensive on-orbit infrastructure to be manufactured from materials acquired from Earth or by salvaging End of Life (EOL) satellites has broad implications. Firstly, it has the potential of reducing the amount of Space Debris accumulated by multiple launches and exacerbating the effect of Kesslers Syndrome (Kessler 1985) and secondly, there is a potential for significant cost reductions if new satellite systems can be built in orbit. An example of this: large components of a spacecraft could be built in space (using Laser Material Processing Techniques) and then attached to satellites in orbit (which were built on Earth) to reduce constraints on payload volume limits. Such components include:
- Primary structure to support payloads and other sub systems
- solar panels
- antenna dishes
- Structure to establish forward bases on the Lunar surface or other celestial bodies
- Repairs conducted on other satellite missions
Previous Space Manufacture Mission Concepts
Wilson et al (1987) discuss the potential of using a pultrusion method and having preformed composite material loaded onto spools and an in orbit manufacture system in the Space shuttle – this system would then allow the in orbit manufacture of large structures ensure that “the number of joints would be greatly reduced compared with structures manufactured at a ground station and assembled in space…In this way, the structural materials can be transported to orbit at high packaging density for fabrication of very-low-density structure on-orbit. Tailored properties such as stiffness, tensile strength, and toughness are controlled by precise fiber orientations and selective combinations of matrix and fibre systems.”
Combining the potential of utilising a pultrusion method to form composite material and then having a laser cutting system would allow for enormous flexibility in the shape, size and complexity of space infrastructure. Such a pultrusion machine is illustrated by Wilson et al (1987) in Fig 1.
Fig 1 Pultrusion machine concept by Wilson et al (1987). This system above represents the terrestrial part of the material preparation. The prepared material would then be stored onto “spools” for logistical ease.
The lower image of the space shuttle illustrates how extended lengths of material can make use of the emptiness of space, allowing for potentially large structures to be built. Further implications include the potential for larger space structure manufacture.The implications of using a pultrusion machine combined with a laser cutter / welder means that spools of preformed composite material (manufactured on Earth) can then be launched into orbit, and then installed into an orbiting manufacture facility. The spools can then be reeled out and formed as required. A benefit to consider of composite material forming in this way is that shapes can be made solid without the requirement of fixtures and fastenings, etc. which simplifies infrastructure designs. A graphical representation of this is provided by Wilson et al (1987) in Fig 2.
Figure 2 Wilson et al (1987) provide a graphical representation of how a spool loaded material is fed into a manufacturing system, which can then be processed. As discussed by Wilson et al (1987), large platforms could be formed which then provide a basis for future payloads to be installed. Other planetary bodies would also benefit from this capability of extra-terrestrial manufacture and could drastically reduce the costs of future missions.
Laser Manufacture Processes
Using lasers for manufacture in orbit could be utilised to create “repair stations” – an automated orbiting workshop that could be programmed to manufacture a number of parts which could then be used to repair other space craft. The repair station could be docked with via other spacecraft (like a Shuttle variant, for instance) and then the parts used elsewhere.
The implications of this could mean that parts are created “on demand” and potentially have cost saving benefits for carrying out on-orbit repairs of space craft. In this age of technology, schematics and prints for parts can be communicated electronically, especially with CAD program interfacing. Combined with an appropriate storage capability for housing manufacturing material (such as the spools used in the pultrusion system), then the flexibility to create a wide range of parts could be attractive and make future space missions safer and more reliable. The variety of techniques used by lasers are illustrated in Fig 3.
Figure 3 Steen & Mazumder (2010) illustrate the different capabilities of lasers used in manufacturing. This broad capability allows a variety of processes that could be utilised for space manufacture
A brief overview of the initial ideas and potential for on-orbit servicing and manufacture has been highlighted. As the entire field of on-orbit manufacture is an enormous undertaking, the main aspects for future focus include:
- Subsystem Studies
- Cost Modelling
- Laser Material Processing of Materials
- Laser Physics will be studied, but assumptions will be made as in depth laser design is beyond the scope of this project.
Steen,M & Mazumder,J (2010) “Laser Material Processing 4th Edition” Springer London Dordrecht, Heidelberg, New York
Wilson, M et al (1987) “Potential for On-Orbit Manufacture of Large Space Structures Using the Pultrusion Process” Langley Research Center, Hampton, Virginia, NASA Scientific and Technical Information Division
Kessler, D.J (1985) “Orbital Debris Issues” Advances in Space Research.5 (2):3-10