There are a number of possible applications for nanomaterials in space. For example, aluminium or boron oxide nanopowders, which are coated with thin polymer films (thickness between 20 and 300 nm) to prevent agglomeration, can be used as solid propellants in rocket engines. Due to their increased surface area, the nanopowders create more thrust in solid-propellant rockets. The agglomeration of the particles can be avoided by polymer coatings and addition of a stabilizer, which also improves the handling of the materials.
How Nanopowders Can Improve Power Systems and Help the Environment
Also, for liquid propellant rockets, an increased power density can be obtained through addition of nanopowders to hydrocarbon fuels. Suspended in organic solvents, nanopowders can also be used for bi-propellant systems (e.g. ethanol/LOX, which represents a more environmentally-friendly solution than hydrazine/N2O4). Such nanopowders are developed in the frame of a SBIR programme of NASA in co-operation with different nanotechnology companies (DWA Aluminium Composites, Argonide, Sigma Technologies etc.) and aerospace companies.
Aerogels Used in Space Applications
Aerogels, which consist of a highly porous 3d-network of nanoparticles, offer the advantages of a high internal surface as well as a small density, and thus are good options for applications, e.g. as electrode material for improved capacitors and batteries, or as thermal isolation material. Aerogels can be made of different materials, e.g. silicates or carbon. In space, aerogels have already been used as thermal isolation material in the Mars Rover of the Pathfinder mission, as well as a particle collector in the NASA Stardust mission. A disadvantage of conventional aerogels is their brittleness and small mechanical stability. Recent developments demonstrate, however, that the mechanical characteristics of aerogels can be improved significantly by using inorganic and organic material combinations (e.g. silicate/Polyurethane) substantially. Therefore, in the future, aerogels may find applications as high strength, ultra-light structure material in space.
Potential Industry Applications for Hard and Soft Magnetic Nanomaterials
Magnetic nanocomposites consist of nanoscale magnetic crystallites in an amorphous or crystalline matrix (e.g. polymers or silicates). Both soft and hard magnetic (low resp. high coercivity) nanomaterials can be obtained. Soft magnetic materials are suitable for transformers and inductors in electronic components, whereas hard magnetic materials possess application potentials in energy storage, data memories and sensor technology. With nanostructured materials, physical parameters such as coercivity can be adjusted selectively, which opens up new applications. Examples for magnetic nanocomposites are polymers or SiO2 coated cobalt nanoparticles, which can be produced economically via a wet chemical procedure. These nanocomposites possess a higher permeability, curie temperature and electrical resistance than conventional ferrite materials due to quantum coupling effects between neighbouring nanoparticles. Another example is polyimide-coated Fe nanoparticles, which can be manufactured by compression moulding of nanoscale iron powders and polyimide, and possess TMR (tunneling magneto resistance) properties.
Benefits of Using Magnetic Nanocomposites
The advantages of theses composites are an increased sensitivity to detect changes of magnetic field and a higher working temperature range, which could be utilized for the development of miniaturized and energy-saving microwave antennas, inductors, sensors or data memories for space applications. At present, different research projects in the frame of the (Small Business Innovation Research) SBIR programme of NASA and also a joint project of the BMBF exist in this context.
‘Intelligent’ Nanomaterials Which Have Sensing Properties
At present, a still rather visionary application of molecular nanotechnology is the production of ‘intelligent’ materials with intrinsic sensing properties, programmable optical, thermal and mechanical characteristics or even self-healing properties. First approaches in this direction were realized, e.g. in the form of nanocomposites, consisting of conjugated polymers in a nanostructured silicate matrix, which changes the color with respect to mechanical, chemical or thermal stress. Applied as coatings for construction materials, mechanical or corrosion damages, as well as critical changes of temperature could be detected promptly and economically.
Biomimetic Materials that Use Molecular Nanotechnology to Achieve Self-Organization, Self-Healing and Self-Replication
Long-term and visionary nanotechnological conceptions, however, go far beyond these first approaches. This applies in particular to the development of biomimetic materials with the ability of self-organization, self-healing, and self-replication by means of molecular nanotechnology. One objective here is the combination of synthetic and biological materials, architectures and systems, respectively, the imitation of biological processes for technological applications. This field of nanobiotechnology is at present still in the state of basic research, but is regarded as one of the most promising research fields for the future.
NASA’s Research into Nanomaterials at the Institute for Biologically Inspired Materials
Due to the postulated high innovation potential for space technology, NASA invests a substantial part of its nanotechnology budget into this field of basic research. For example, NASA at present establishes the Institute for Biologically Inspired Materials, with different university research institutes, e.g. Princeton University as participants. This institute is funded for a period of 10 years with annually $3 million, and its main task is to transfer basic inventions to the development of materials with extraordinary mechanical and self-healing properties, like those of some biological materials such as shells or bones.