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Metal foam in space application

The main advantage of the use of aluminium or magnesium foam in space applications is the possibility to manufacture complex and potentially large metallic parts directly in space, without need to launch voluminous structures from the Earth.

Due to expanded porous shape (inside porosity of min. 85%) it is expected that foamed components made of lightweight metals will possess very high stiffness to weight ratio that is comparable with current composites or better. Most of the properties can be adjusted by porosity level, what enables tailoring properties of future components without need to change installed technology and molds. The use of metal foam for space structures instead of plastics or ceramics would also be beneficial because the foams: Inside porosity of the foam reduces apparent density of final component below 1kg/liter and creates large cross sections with high cross-sectional moments of inertia in all directions what is beneficial for significant weight reduction in stiffness driven design. The components are made by foaming in suitable molds which gives them surface skin having complexity, precision and appearance similar as in case of traditional casting.

Fig. 1
Foamed components

There are crucial differences in comparison to standard casting techniques:
Foaming in space requires:
The foaming itself is a simple and relatively quick manufacturing method with a production rate for one part in couple of minutes, what makes strong benefits especially if compared to 3D printing. The mold itself gives the foamed part shape and accuracy, so alternative components can be manufactured easily by changing the mold. As almost all properties of the foamed part strongly depend on porosity, they can be tailored even without need to change the mold. The porosity can be adjusted by proper amount of foaming agent admixed into foamable feedstock. Since the feedstock is delivered from the Earth this “property-tailoring-approach will not require any cost intensive treatment in space.

Parable of Al foam
Parable of aluminium foam

A model of a heat shield made of aluminium foam in the shape of a parabolic dish with a diameter of 60 cm. The unique construction allows to maintain a constant temperature difference between the inner and outer side of the dish in a suitable orbit, which can be used to continuously generate mechanical energy resp. electricity even in the absence of several hours of sunlight. The weight of the dish is 1200 g, the volume is 7 dm3. The volume of foamable feedstock granulate that needs to be launched from the Earth to foam the dish necessary to foam the dish is just 0,5 dm3.