DEFENCE AND SPACE APPLICATIONS

Nanotechnology can play a vital role in defence and space systems by minimising size, weight and power consumption that are important for long-range coverage. Also, embedded nanosensors enabled with wireless networks can enhance the intelligence of future warfare systems. There are several possible applications of nanotechnology for defence and space applications, as shown below:

• Light-weight vehicles to enhance fuel economy; longer distances can be covered for the same fuel capacity

• Smart components with built-in condition and load-monitoring sensors, such as fibre Bragg

• Adaptive structures, like adaptive skin, for better thermal control • High energetic propellants such as nano-dispersed aluminum • Lightweight protective clothes

• Anti-ballistic and shatterproof armour

• Advanced sensors, such as, high-resolution vision systems, RF, infrared, acoustic arrays, terahertz and through-the-wall radar vision

• Physical identification tags (RFID) for goods, digital ID tags for documents and information

• Biometric sensing for personal identification characteristics, such as, fingerprint, face, DNA

• Ambient intelligence for surveillance by means of distributed wireless sensor networks • Tracking and tracing with position and motion sensors

Intelligent textiles with embedded sensors in the soldiers’ attire is another important potential area for application of nanotechnology. The clothes soldiers wear can be modified to provide better protection against heat and cold and integrated nanosensors can be used for remote monitoring of heartbeat and blood pressure. In addition, clothing can have built-in protection against bullets.

Nanotechnology is needed for improved detector sensitivities (signal-to-noise ratios), to miniaturise sensor arrays for selectivity, to tailor-make high surface area materials for detection/absorption/deactivation and to create selective catalysts. Microsystems technology and nanotechnology will therefore enable small portable sensor systems capable of identifying chemical, bio, nuclear, radiation or energy threats. This will enhance the flexibility of deployment and operations, increase the safety of soldiers and civilians and enhance environmental security. Onboard intelligence will continuously increase, facilitating automated control and maintenance. Naval vessels have additional requirements with respect to detection and surveillance sensor systems.

Other technologies which can be integrated in future weapons are RF ID-tags in guns, cartridges, target positioning/recognition (via micro IR camera on guns or PDAs, microradar, RF-array, through-the wall THz radar), and smart helmets to pull the trigger from a distance (teleweapon), various ammotypes (shaped ceramic materials, softer bullets, high-penetration bullets, sensor modes/smart dust and insensitive tailored explosives to limit collateral damage).

Closely connected to the concept of the smart helmet is that of anti-ballistic protection

via a light-weight helmet consisting of a combination of polymers, fibres and nanomaterials. This new nanocomposite should have higher impact resistance than present fibre composite systems and should have a significantly reduced weight. The application of nanofibres and buckypaper in combination with present high-strength fibres and polymer materials to create new composite materials seems to be most promising. For the next generation of helmets, the use of fibres such as Kevlar, Dyneema or M5 is most realistic in combination with nanomaterials which can enlarge the strength of the composite and keep the fibres closely packed in the composite structure at impact. M5 is the newest type of fibre in this category and product applications of this fibre are expected in the next few years. Nanoclay in a silliputty-type of polymer matrix combined with fibres is a possible alternative. These high-strength fibres can, in theory, bring significant improvement. The same applies to metal nanoparticles coated with a multiple-layered ceramic nanocoating. These coatings were originally developed for turbine blade protection but the extreme hardness is also of use for anti-ballistic nanofillers in composites. In the long term (10–15 years), a more dominant use of electrospun nanofibres to create basic fibre strength in the composite can be expected. These CNT fibres and other nanofibres have a theoretical strength of 130–180 GPa. Thanks to the technological advances in high strength polymer fibres such as carbon, aramide and Dyneema, the performance of antiballistic suits has improved considerably over the last 20 years, with subsequent reduction in weight (30%). These suits with integrated or inserted

composite fibre structures are quite effective and are being successfully applied for ballistic protection of the body. However, the composite structures are not sufficiently flexible to be used for protection of extremities such as the arms, legs and neck. At present, injuries of these extremities have become the dominant factor in casualties, especially from bombings and subsequent shatter, resulting in loss of military power and high cost of medical treatment. In view of this, several concepts for flexible armour have been proposed and are now in development.

Magneto-restrictive fluid—a nanoparticle-filled flexible medium that can be electrically activated to become rigid

Shear-thickening fluid—a nanoparticle-filled binder for high-strength textiles that is flexible under low shear rate and that becomes rigid under high shear rate impact (passive system, ARL). This nanoparticle-filled system inhibits deformation and sliding of high strength fibres at high shear rate.

Silliputty-type of elastomers in combination with ceramic armour—an elastomer system which is deformable and elastic at low shear rate and stiff at high shear rate. It is similar to shear thickening fluids, but has so far been less effective in antiballistics (passive system, for example, D₃O material).

The ultimate goal will be to create nanorobots or nanobots for activities on land and NUAV (nano-unmanned aerial vehicles) for reconnaissance and sensory activities in the air (flying artificial insects). Uninhabited combat vehicles (fighter, submarine, and vehicle) with higher performance and lower casualty risk can also be expected. Ideally, all microvehicles and robots should be less visible for enemy troops (biomimetic structures), should last long enough to gather essential information, and should be low in cost and therefore redundant.

Wounds can be dressed with intelligent bandaids which monitor the moisture level and bacterial activity, and release antimicrobials on nanoparticles to kill the bacteria. Part of this health monitoring system can be a portable sample preparation and lab-on-chip analysis kit enabling the soldier to test his own body fluids when he needs more specific data and water and food. Ideally, this analysis system will be built into his smart suit and will be able to detect bioagents and apply antidotes to the soldier. Biosensors for body-function monitoring can be expected to be integrated subcutaneously in the body of future combat soldiers. Core temperature measurement with a swallowable passive RF-sensor is one of the solutions for accurate and low-cost core temperature measurement of soldiers in combat.

Smaller satellites are now becoming feasible, owing to the miniaturization enabled by nanotechnology. Besides reducing their size, weight and power consumption, the use of micromachined devices could give better component integration in areas such as propulsion, communication, data processing, power generation and navigation. With a distributed network of small satellites instead of one big one, both functionality (multi-aperture synthesis for better accuracy, formation flying) as well as redundancy is gained. The ultimate goal is to develop

a complete satellite-on-chip, the so-called picosatellites. Microsatellites (~ 10–30 cm) are in development in many countries: USA/NASA, UK, France, Germany, Sweden and Spain, both for civil and defence applications.