Applications of Nanotechnology in Aerospace
Content
APPLICATIONS OF NANOTECHNOLOGY IN AEROSPACE ABSTRACT: Aerospace, the very typical term heard by everyone in our daily lives, which explores the universe which we can’t see. The current exploration of space includes the huge investment and effort to be expended. So, nanotechnology can be invested and developed in aerospace to get much more advancement. This miniaturized technology would bring revolution in the current trend. Application of nanotechnology is its infancy and no one can predict with accuracy which will result from the full flowering of the field over the next several decades. The aerospace applications for nanotechnology include high strength, low weight composites, improved electronics and displays with low power consumption, variety of physical sensors etc., Nanotechnology has enormous potential to improve the reliability and performance of aerospace hardware while lowering manufacturing cost. Carbon Nanotubes are being widely used for aerospace programmes. It is used in the applications such as space elevators, launch vehicles, rocket propulsion techniques etc. Not only NASA-the leading space organization in the world, but every country is trying to integrate nanotechnology in aerospace applications.
EMERGENCE OF NANOTECHNOLOGY : Nanotechnology, the creation of functional materials, devices and systems through control of matter on the nanometer length scale and exploitation of novel phenomena and properties (physical, chemical, biological, mechanical, electrical...) at that length scale. The concept of nanotechnology originated with American physicist Richard P. Feynman.He believed the creation of nanoscale devices was possible within the boundaries set by the laws of physics. He specifically cited the possibility of atom-by-atom assembly—that is, building a structure (a molecule or a device) from individual atoms precisely joined by chemical forces. This possibility led to the concept of a ―universal assembler,‖ a robotic device at nanoscale dimensions that could automatically assemble atoms to create molecules of the desired chemical compounds. Such a device, for example, could assemble carbon atoms to form low-cost, large diamonds, a potentially important industrial material, now used only in limited quantities due to the high cost of mining and synthesis. Such synthetic diamonds could have many industrial and consumer applications because they are lightweight and yet extremely hard, and are electrically insulating but excellent conductors of heat. The idea of a nanoscale robotic assembler continues to be promoted by some researchers, although there is considerable debate whether such a device is indeed possible within the known laws of chemistry, physics, and thermodynamics.
EXPLORATION OF NANOTECHNOLOGY: Nanotechnology, the creation and use of materials or devices at extremely small scales. These materials or devices fall in the range of 1 to 100 nanometers (nm). One nm is equal to one-billionth of a meter (.000000001 m), which is about 50,000 times smaller than the diameter of a human hair.Scientists refer to the dimensional range of 1 to 100 nm as the nanoscale, and materials at this scale are called nanocrystals or nanomaterials. The nanoscale is unique because nothing solid can be made any smaller. It is also unique because many of the mechanisms of the biological and physical world operate on length scales from 0.1 to 100 nm. At these dimensions materials exhibit different physical properties; thus scientists expect that many novel effects at the nanoscale will be discovered and used for breakthrough technologies. Nanotechnology is in its infancy, and no one can predict with accuracy what will result from the full flowering of the field over the next several decades. Many scientists believe it can be said with confidence, however, that nanotechnology will have a major impact on aerospace; energy production and conservation; environmental cleanup and protection; electronics, computers, and sensors; and world security and defense. The scientific community began serious work in nanoscience when tools became available in the late 1970s and early 1980s—first to probe and later to manipulate and control materials and systems at the nanoscale. These tools include the transmission electron microscope (TEM), the atomic force microscope (AFM), and the scanning tunneling microscope (STM).
IMPLICATION OF NANOTECH ON AEROSPACE : The aerospace applications for nanotechnology include high strength, low weight composites, improved electronics and displays with low power consumption, variety of physical sensors, multifunctional materials with embedded sensors, large surface area materials and novel filters and membranes for air purification, nanomaterials in tires and brakes and numerous others. The status of composite preparation – polymer matrix, ceramic matrix and metal matrix will be presented. Examples of current developments in the above application areas, particularly physical sensors, actuators ,nanoelectromechanical systems etc. will be presented to show what the aerospace industry can expect from the field of nanotechnology. Of all the nanoscale materials, carbon nanotubes (CNTs) have received the most attention across the world. These are configurationally equivalent to a two-dimensional graphene sheet rolled up into a tubular structure. With only one wall in the cylinder, the structure is called a singlewalled carbon nanotube (SWCNT). The structure that looks like a concentric set of cylinders
with a constant interlayer separation of 0.34 Angstroms is called a multiwalled carbon nanotube (MWCNT). The development of nanotechnology is important for the exploration and future settlement of space. Current manufacturing technologies limit the reliability, performance, and affordability of aerospace materials, systems, and avionics. Nanotechnology has enormous potential to improve the reliability and performance of aerospace hardware while lowering manufacturing cost. For example, nanostructured materials that are perhaps 100 times lighter than conventional materials of equivalent strength are possible. Embedding nanoscale electromechanical system components into earth-orbiting satellites, planetary probes, and piloted vehicles potentially could reduce the cost of future space programs. The miniaturized sensing and robotic systems would enhance exploration capabilities at significantly reduced cost. Thousands to millions of such miniaturized devices could help map a planet in a single launch.
CNT IN AEROSPACE: Carbon Nano Tubes(CNT) are being widely studied for various applications ranging from medical to electronics and also optical devices. They are especially studied for the suitability and applications in aerospace and aeronautical field. A useful application in aerospace that we are studying is the improvement of electrical properties of composites made from carbon nanotubes and epoxy resin. Carbon nanotubes were synthesized by thermal arc plasma process after optimization of the synthesis parameters. These samples were then analysed by electron microscopes like scanning electron and transmission electron microscopes (SEM and TEM), in order to establish the morphology of the nanostructures. Atomic force microscopy (AFM) and electron diffraction studies were also carried out before using the sample for the composite material preparation. Composites of epoxy resin with curing agent as well as a mixture of graphite and carbon nanotubes were prepared with varying proportions of the mixture. The electrical resistivity of the material was studied under varying humidity, temperature and voltage conditions. The results of these studies present interesting features which are useful in choosing the ideal composition and ratio of the composite material for use in shielding of electrical circuits of space vehicles from radiations of the outer space.
ROCKET FUELS UTILISING NANOTECHNOLOGY: Several aerospace firms have programmes under way for the use of nanosized particles of aluminium or hafnium for rocket propulsion applications. The improved burn and
the speed of ignition of such particles are significant factors for this market. Aluminized liquid hydrocarbon propellant fuels would increase propulsion energy; particularly in volume limited systems through the utilization of nanosize aluminium. Rocket-fuel additives containing iron-oxide particles 3nm wide can act as a catalyst to convert solid propellants into gases that are burned when rockets or missiles are launched, making it more reactive than traditional iron-oxide catalysts, allowing faster conversion of the propellants and greater speed or range for the missiles. An example of a future use of Nanotechnology in fuel is Nanogellant gelled propellants. These gellants have a nanometre scale structure. The Nanogellent also has an enormously high surface area per gram.Gelled fuel reduces leakage and increases safety. Nanogellant for gelled cryogens has a surface area of nearly 1000m2/g, leading to cryogenic fuels gelled with 25-50% less mass than traditional gellant material. Another use is the Nanoparticulate of aluminium which can be used for jet fuels. These smaller particles allow for more efficient combustion and lower specific fuel consumption. It is hoped the adoption of both nano fuels will be seen used for the next generation of aerospace vehicles.
NANOSATELLITES: Nanosatellites are miniature, intelligent LEO satellites weighing from 5to10 kilograms. Nanosatellites can be designed using silicon micromachining and micropropulsion techniques.These nanosatellites can be effectively used for disaster management , small span communications and environmental monitoring. Low cost nanosatellite with GPS System which could effectively be used for tsunami warning system. With the aid of silicon micromachining technique, miniature semiconductor components can be fabricated for this tiny satellite. Nanotechnology forms the backbone of micromachining technique. In India, nanosatellites will effectively serve in disaster management especially this satellite can be used with Tsunami warning system. Using GPS and four such nanosatellites, the reciever position (latitude , longitude , and altitude) can be determined accurately. The production of micronanosatellites will lead to two main advantages: a reduction of costs in launching the satellite due to their lower mass, and with the same weight launched, there will be an increased number of functionalities in orbit.
SPACE ELEVATOR: Experts proposed a space elevator, a cable extending from the Earth's surface into space with a center of mass at geosynchronous altitude. If such a system could be built, it should be mechanically stable and vehicles could ascend and descend along the cable at almost any
reasonable speed using electric power. The first incredibly difficult problem with building a space elevator is strength of materials. Maximum stress is at geosynchronous altitude so the cable must be thickest there and taper exponentially as it approaches Earth. Any potential material may be characterized by the taper factor -- the ratio between the cable's radius at geosynchronous altitude and at the Earth's surface. For steel the taper factor is tens of thousands - clearly impossible. Diamond is, however, brittle. Carbon nanotubes have a strength in tension similar to diamond, but bundles of these nanometer-scale radius tubes shouldn't propagate cracks nearly as well as the diamond tetrahedral lattice. Thus, if the considerable problems of developing a molecular nanotechnology capable of making nearly perfect carbon nanotube systems approximately 70,000 kilometers long can be overcome, the first serious problem of a transportation system capable of truly large scale transfers of mass to orbit can be solved. The next immense problem with space elevators is safety -- how to avoid dropping thousands of kilometers of cable on Earth if the cable breaks.
How NASA is Planning to Use Nanotechnology in its Space Projects: NASA is the world's leading organization for aeronautical research. It's world-class capability is built on a tradition of expertise in aeronautical engineering and its core research areas, including aerodynamics, aeroacoustics, materials and structures, propulsion, dynamics and control, sensor and actuator technologies, advanced computational and mathematical techniques, and experimental measurement techniques. Beginning with theoretical insight, augmented by research and testing in the laboratory and in flight, NASA scientists and engineers develop and use rich databases of information, unique analytical tools, and their singular expertise to close the gap between empirical and abstract knowledge. This leads to design better tools and technologies for improving vehicle and air system safety and performance. Many of the nanotechnology objectives of NASA aim at a long-term time horizon, and are more or less visionary at present. One main goal is a significant increase in spacecraft capabilities with simultaneous mass reduction and miniaturization, which can not be achieved with conventional technologies. A new era of robotic exploration of the solar system is to be proposed by application of nanotechnology, among other technologies, through the development of small economical spacecrafts with high autonomy and improved capabilities. Furthermore, nanotechnological diagnostics and therapy procedures will improve life support systems, and an autonomous medical supply for astronauts which will pave the way for longterm and more complex manned space missions.
Status of India: India,a late starter in nanotechnology, sputtered along in fits and starts before readying for take-off. While there is support for the sector at the highest scientific levels, funding remains low. And with negligible interest from industry and only a small pool of skilled scientists, India is a long way from using nanoscience to solve its problems. It seems that India has not learnt any lessons from the past. It missed the microelectronics revolution of the 1970s and 1980s through a lack of timely investment, and was no wiser in the 1990s when nanoscience emerged, now we have to create the technical manpower to work in this emerging field. We have to train students, teachers and research scholars. Unless we do this, there will not be enough work happening in this area in the near future. There has been some very good work from some of the laboratories, particularly from Bangalore, in synthesising and characterising a large variety of new materials.This centre will include pilot-scale facilities for producing and manipulating carbon nanotubes, ceramic and polymer composites.
FAQ: Most space enthusiasts are disappointed with the current state of space exploration. To what extent will nanotechnology facilitate the exploration of space?
=> Nanotech would be a great help in reaching space and living in space. Aerospace hardware would be many times lighter, which saves fuel. Avionics would be literally billions of times lighter. That's just with first-stage molecular nanotech that can only build diamondoid. Advanced mechanochemistry would allow 100% recycling--life support--in a very small box. No more worries about how to grow wheat in zero-G. Nanotechnology makes a lot cheaper to reach orbit because most of the energy input is not from chemical fuel. Nanotech will also reduce the need for space access. When we can build anything we want with carbon, we won't have to go after metal-rich asteroids. When our technology is 10 to 100 times more efficient, we'll be easier on the environment down here. Assuming diamondoid materials we can predicted the performance of several existing single-stage-to-orbit (SSTO) vehicle designs. The predicted payload to dry mass ratio for these vehicles using titanium as a structural material varied from < 0 to 36%, i.e., the
vehicle weighs substantially more than the payload. With hypothetical diamondoid materials the ratios varied from 243% to 653%, i.e., the payload weighs far more than the vehicle.
CONCLUSION: Many of the applications discussed here are speculative to say the least. However, they do not appear to violate the laws of physics. Something similar to these applications at these performance levels should be feasible if we can gain complete control of the three-dimensional structure of materials, processes and devices at the atomic scale. How to gain such control is a major, unresolved issue. However, it is clear that computation will play a major role regardless of which approach -- positional control with replication, self-assembly, or some other means -- is ultimately successful. As nanotechnology progresses we may expect applications to become feasible at a slowly increasing rate. However, if and when a general purpose programmable assembler/replicator can be built and operated, we may expect an explosion of applications. Nanotechnology advocates and detractors are often preoccupied with the question "When?" There are three interrelated answers to this question: => Nobody knows. There are far too many variables and unknowns. Beware of those who have excessive confidence in any date. => The time-to-nanotechnology will be measured in decades, not years. While a few applications will become feasible in the next few years. => The time-to-nanotechnology is very sensitive to the level of effort expended. Resources allocated to developing nanotechnology are likely to be richly rewarded, particularly in the long term. In recent years every country is showing a lot of interest regarding the space exploration programs.And, hence let's expect a faster growth of nanotechnology in aerospaceapplications.
EMERGENCE OF NANOTECHNOLOGY : Nanotechnology, the creation of functional materials, devices and systems through control of matter on the nanometer length scale and exploitation of novel phenomena and properties (physical, chemical, biological, mechanical, electrical...) at that length scale. The concept of nanotechnology originated with American physicist Richard P. Feynman.He believed the creation of nanoscale devices was possible within the boundaries set by the laws of physics. He specifically cited the possibility of atom-by-atom assembly—that is, building a structure (a molecule or a device) from individual atoms precisely joined by chemical forces. This possibility led to the concept of a ―universal assembler,‖ a robotic device at nanoscale dimensions that could automatically assemble atoms to create molecules of the desired chemical compounds. Such a device, for example, could assemble carbon atoms to form low-cost, large diamonds, a potentially important industrial material, now used only in limited quantities due to the high cost of mining and synthesis. Such synthetic diamonds could have many industrial and consumer applications because they are lightweight and yet extremely hard, and are electrically insulating but excellent conductors of heat. The idea of a nanoscale robotic assembler continues to be promoted by some researchers, although there is considerable debate whether such a device is indeed possible within the known laws of chemistry, physics, and thermodynamics.
EXPLORATION OF NANOTECHNOLOGY: Nanotechnology, the creation and use of materials or devices at extremely small scales. These materials or devices fall in the range of 1 to 100 nanometers (nm). One nm is equal to one-billionth of a meter (.000000001 m), which is about 50,000 times smaller than the diameter of a human hair.Scientists refer to the dimensional range of 1 to 100 nm as the nanoscale, and materials at this scale are called nanocrystals or nanomaterials. The nanoscale is unique because nothing solid can be made any smaller. It is also unique because many of the mechanisms of the biological and physical world operate on length scales from 0.1 to 100 nm. At these dimensions materials exhibit different physical properties; thus scientists expect that many novel effects at the nanoscale will be discovered and used for breakthrough technologies. Nanotechnology is in its infancy, and no one can predict with accuracy what will result from the full flowering of the field over the next several decades. Many scientists believe it can be said with confidence, however, that nanotechnology will have a major impact on aerospace; energy production and conservation; environmental cleanup and protection; electronics, computers, and sensors; and world security and defense. The scientific community began serious work in nanoscience when tools became available in the late 1970s and early 1980s—first to probe and later to manipulate and control materials and systems at the nanoscale. These tools include the transmission electron microscope (TEM), the atomic force microscope (AFM), and the scanning tunneling microscope (STM).
IMPLICATION OF NANOTECH ON AEROSPACE : The aerospace applications for nanotechnology include high strength, low weight composites, improved electronics and displays with low power consumption, variety of physical sensors, multifunctional materials with embedded sensors, large surface area materials and novel filters and membranes for air purification, nanomaterials in tires and brakes and numerous others. The status of composite preparation – polymer matrix, ceramic matrix and metal matrix will be presented. Examples of current developments in the above application areas, particularly physical sensors, actuators ,nanoelectromechanical systems etc. will be presented to show what the aerospace industry can expect from the field of nanotechnology. Of all the nanoscale materials, carbon nanotubes (CNTs) have received the most attention across the world. These are configurationally equivalent to a two-dimensional graphene sheet rolled up into a tubular structure. With only one wall in the cylinder, the structure is called a singlewalled carbon nanotube (SWCNT). The structure that looks like a concentric set of cylinders
with a constant interlayer separation of 0.34 Angstroms is called a multiwalled carbon nanotube (MWCNT). The development of nanotechnology is important for the exploration and future settlement of space. Current manufacturing technologies limit the reliability, performance, and affordability of aerospace materials, systems, and avionics. Nanotechnology has enormous potential to improve the reliability and performance of aerospace hardware while lowering manufacturing cost. For example, nanostructured materials that are perhaps 100 times lighter than conventional materials of equivalent strength are possible. Embedding nanoscale electromechanical system components into earth-orbiting satellites, planetary probes, and piloted vehicles potentially could reduce the cost of future space programs. The miniaturized sensing and robotic systems would enhance exploration capabilities at significantly reduced cost. Thousands to millions of such miniaturized devices could help map a planet in a single launch.
CNT IN AEROSPACE: Carbon Nano Tubes(CNT) are being widely studied for various applications ranging from medical to electronics and also optical devices. They are especially studied for the suitability and applications in aerospace and aeronautical field. A useful application in aerospace that we are studying is the improvement of electrical properties of composites made from carbon nanotubes and epoxy resin. Carbon nanotubes were synthesized by thermal arc plasma process after optimization of the synthesis parameters. These samples were then analysed by electron microscopes like scanning electron and transmission electron microscopes (SEM and TEM), in order to establish the morphology of the nanostructures. Atomic force microscopy (AFM) and electron diffraction studies were also carried out before using the sample for the composite material preparation. Composites of epoxy resin with curing agent as well as a mixture of graphite and carbon nanotubes were prepared with varying proportions of the mixture. The electrical resistivity of the material was studied under varying humidity, temperature and voltage conditions. The results of these studies present interesting features which are useful in choosing the ideal composition and ratio of the composite material for use in shielding of electrical circuits of space vehicles from radiations of the outer space.
ROCKET FUELS UTILISING NANOTECHNOLOGY: Several aerospace firms have programmes under way for the use of nanosized particles of aluminium or hafnium for rocket propulsion applications. The improved burn and
the speed of ignition of such particles are significant factors for this market. Aluminized liquid hydrocarbon propellant fuels would increase propulsion energy; particularly in volume limited systems through the utilization of nanosize aluminium. Rocket-fuel additives containing iron-oxide particles 3nm wide can act as a catalyst to convert solid propellants into gases that are burned when rockets or missiles are launched, making it more reactive than traditional iron-oxide catalysts, allowing faster conversion of the propellants and greater speed or range for the missiles. An example of a future use of Nanotechnology in fuel is Nanogellant gelled propellants. These gellants have a nanometre scale structure. The Nanogellent also has an enormously high surface area per gram.Gelled fuel reduces leakage and increases safety. Nanogellant for gelled cryogens has a surface area of nearly 1000m2/g, leading to cryogenic fuels gelled with 25-50% less mass than traditional gellant material. Another use is the Nanoparticulate of aluminium which can be used for jet fuels. These smaller particles allow for more efficient combustion and lower specific fuel consumption. It is hoped the adoption of both nano fuels will be seen used for the next generation of aerospace vehicles.
NANOSATELLITES: Nanosatellites are miniature, intelligent LEO satellites weighing from 5to10 kilograms. Nanosatellites can be designed using silicon micromachining and micropropulsion techniques.These nanosatellites can be effectively used for disaster management , small span communications and environmental monitoring. Low cost nanosatellite with GPS System which could effectively be used for tsunami warning system. With the aid of silicon micromachining technique, miniature semiconductor components can be fabricated for this tiny satellite. Nanotechnology forms the backbone of micromachining technique. In India, nanosatellites will effectively serve in disaster management especially this satellite can be used with Tsunami warning system. Using GPS and four such nanosatellites, the reciever position (latitude , longitude , and altitude) can be determined accurately. The production of micronanosatellites will lead to two main advantages: a reduction of costs in launching the satellite due to their lower mass, and with the same weight launched, there will be an increased number of functionalities in orbit.
SPACE ELEVATOR: Experts proposed a space elevator, a cable extending from the Earth's surface into space with a center of mass at geosynchronous altitude. If such a system could be built, it should be mechanically stable and vehicles could ascend and descend along the cable at almost any
reasonable speed using electric power. The first incredibly difficult problem with building a space elevator is strength of materials. Maximum stress is at geosynchronous altitude so the cable must be thickest there and taper exponentially as it approaches Earth. Any potential material may be characterized by the taper factor -- the ratio between the cable's radius at geosynchronous altitude and at the Earth's surface. For steel the taper factor is tens of thousands - clearly impossible. Diamond is, however, brittle. Carbon nanotubes have a strength in tension similar to diamond, but bundles of these nanometer-scale radius tubes shouldn't propagate cracks nearly as well as the diamond tetrahedral lattice. Thus, if the considerable problems of developing a molecular nanotechnology capable of making nearly perfect carbon nanotube systems approximately 70,000 kilometers long can be overcome, the first serious problem of a transportation system capable of truly large scale transfers of mass to orbit can be solved. The next immense problem with space elevators is safety -- how to avoid dropping thousands of kilometers of cable on Earth if the cable breaks.
How NASA is Planning to Use Nanotechnology in its Space Projects: NASA is the world's leading organization for aeronautical research. It's world-class capability is built on a tradition of expertise in aeronautical engineering and its core research areas, including aerodynamics, aeroacoustics, materials and structures, propulsion, dynamics and control, sensor and actuator technologies, advanced computational and mathematical techniques, and experimental measurement techniques. Beginning with theoretical insight, augmented by research and testing in the laboratory and in flight, NASA scientists and engineers develop and use rich databases of information, unique analytical tools, and their singular expertise to close the gap between empirical and abstract knowledge. This leads to design better tools and technologies for improving vehicle and air system safety and performance. Many of the nanotechnology objectives of NASA aim at a long-term time horizon, and are more or less visionary at present. One main goal is a significant increase in spacecraft capabilities with simultaneous mass reduction and miniaturization, which can not be achieved with conventional technologies. A new era of robotic exploration of the solar system is to be proposed by application of nanotechnology, among other technologies, through the development of small economical spacecrafts with high autonomy and improved capabilities. Furthermore, nanotechnological diagnostics and therapy procedures will improve life support systems, and an autonomous medical supply for astronauts which will pave the way for longterm and more complex manned space missions.
Status of India: India,a late starter in nanotechnology, sputtered along in fits and starts before readying for take-off. While there is support for the sector at the highest scientific levels, funding remains low. And with negligible interest from industry and only a small pool of skilled scientists, India is a long way from using nanoscience to solve its problems. It seems that India has not learnt any lessons from the past. It missed the microelectronics revolution of the 1970s and 1980s through a lack of timely investment, and was no wiser in the 1990s when nanoscience emerged, now we have to create the technical manpower to work in this emerging field. We have to train students, teachers and research scholars. Unless we do this, there will not be enough work happening in this area in the near future. There has been some very good work from some of the laboratories, particularly from Bangalore, in synthesising and characterising a large variety of new materials.This centre will include pilot-scale facilities for producing and manipulating carbon nanotubes, ceramic and polymer composites.
FAQ: Most space enthusiasts are disappointed with the current state of space exploration. To what extent will nanotechnology facilitate the exploration of space?
=> Nanotech would be a great help in reaching space and living in space. Aerospace hardware would be many times lighter, which saves fuel. Avionics would be literally billions of times lighter. That's just with first-stage molecular nanotech that can only build diamondoid. Advanced mechanochemistry would allow 100% recycling--life support--in a very small box. No more worries about how to grow wheat in zero-G. Nanotechnology makes a lot cheaper to reach orbit because most of the energy input is not from chemical fuel. Nanotech will also reduce the need for space access. When we can build anything we want with carbon, we won't have to go after metal-rich asteroids. When our technology is 10 to 100 times more efficient, we'll be easier on the environment down here. Assuming diamondoid materials we can predicted the performance of several existing single-stage-to-orbit (SSTO) vehicle designs. The predicted payload to dry mass ratio for these vehicles using titanium as a structural material varied from < 0 to 36%, i.e., the
vehicle weighs substantially more than the payload. With hypothetical diamondoid materials the ratios varied from 243% to 653%, i.e., the payload weighs far more than the vehicle.
CONCLUSION: Many of the applications discussed here are speculative to say the least. However, they do not appear to violate the laws of physics. Something similar to these applications at these performance levels should be feasible if we can gain complete control of the three-dimensional structure of materials, processes and devices at the atomic scale. How to gain such control is a major, unresolved issue. However, it is clear that computation will play a major role regardless of which approach -- positional control with replication, self-assembly, or some other means -- is ultimately successful. As nanotechnology progresses we may expect applications to become feasible at a slowly increasing rate. However, if and when a general purpose programmable assembler/replicator can be built and operated, we may expect an explosion of applications. Nanotechnology advocates and detractors are often preoccupied with the question "When?" There are three interrelated answers to this question: => Nobody knows. There are far too many variables and unknowns. Beware of those who have excessive confidence in any date. => The time-to-nanotechnology will be measured in decades, not years. While a few applications will become feasible in the next few years. => The time-to-nanotechnology is very sensitive to the level of effort expended. Resources allocated to developing nanotechnology are likely to be richly rewarded, particularly in the long term. In recent years every country is showing a lot of interest regarding the space exploration programs.And, hence let's expect a faster growth of nanotechnology in aerospaceapplications.
