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Posted: Nov 21, 2008
Shields up! How nanotechnology can protect satellites from energy weapons
(Nanowerk Spotlight) When the U.S. military talks about space superiority it defines this as the "degree of control necessary to employ, maneuver, and engage space forces while denying the same capability to an adversary". Although 'space forces' has a Star Wars ring to it, the term basically refers to satellites and these satellites – at least as far as unclassified information goes – do not carry weapons (yet); although the public website of the U.S. Air Force Space Command in listing its capabilities mentions the ability to "conduct defensive and offensive counterspace operations, and space environment assessments". The main functions of the military's space capabilities today are information related – weather, communications, surveillance, reconnaissance, navigation and missile warning capabilities – and has become critical to many military operations. As other military powers build up their space programs, defensive and offensive space capabilities become more of an issue for war planers – something they call "counterspace" activities.
Counterspace operations don't have to be space-based and they could be as simple as what the coalition forces did during the first Gulf war when they cut off Iraq's access to commercially available satellite images. With increased technological capabilities however, ground-based directed energy weapons could become a threat to any satellite, whether it is military or commercial. Modern society has become so dependent on satellite services, for instance interactive TV, mobile broadband internet access, mobile phone services, research activities, or GPS navigation, that any disruption or destruction of satellite communications would seriously cripple many functions vital to society.
A recent research paper ("Improving Satellite Protection with Nanotechnology") published at the Center for Strategy and Technology, at the Air Force's Air War College, discusses how nanotechnology can be used to improve the design of satellites to mitigate the threats posed by ground-based directed energy weapons and high-powered microwaves. The paper states that several nations, including the U.S., Russia and China, already have either built or are developing the technology to construct ground-based directed energy weapons.
The Milstar satellite in orbit with the two equipment wings and two longer solar-array wings deployed; various antennas are visible on the equipment wings. (Lockheed Martin Missiles and Space)
"Ground-based lasers could damage thermal control, structural and power system components and may affect electro-optical sensors on low earth orbiting satellites. Lasers generate and focus intense beams of light that can engage a target from a long distance. Low-power lasers are usually intended to spoof or jam satellite electro-optical sensors, resulting in temporary blindness of the satellite. High-power lasers cause damage or destruction by overheating parts of the satellite. Most susceptible are the satellite’s structure, thermal control system, and solar panels.
"Long-range, ground-based high-power microwave systems are feasible and, in some cases, have application as potential anti-satellite weapons. The intense radio frequency radiation from high-powered microwaves could disable or destroy sensitive electronic components. High-power microwaves are likely to damage satellites using soft kill mechanisms, exploiting the satellite’s inherent design vulnerabilities, rather than hard kill such as melting or blowing up the satellite. Soft kill damage can occur in one of two ways: in-band damage or out-of-band damage. Microwaves at the same frequency as the satellite’s antennas enter the antennas and damage the internal circuitry by overloading them beyond their design limits with electromagnetic energy. Out-of-band damage occurs when microwaves enter through backdoors, or apertures not specifically designed as conduits for electromagnetic energy transmission. The resulting circuitry damage is from electromagnetically induced current resulting in thermal damage."
According to the author of the paper, Lt. Col. Joseph Huntington of the USAF, nanotechnology may provide several solutions to mitigate the threat from directed energy weapons:
Coatings to harden the spacecraft's surface areas to better withstand a weapon's thermal or electromagnetic effects. Nanostructured surface coating would either reflect, absorb, or transmit the incident energy or would perform some combination of the three. One-hundred percent reflection would be the ultimate protection because all the energy would be rejected; less than complete reflection would result in some absorption which would show as heat build-up, material degradation, or burn through.
While completely reflecting thermal and electrical energy would be preferred, dispersing it across the surface would also provide protection. According to Huntington, the Air Force Research Laboratory (AFRL) is managing a research program that uses carbon nanotube membranes, or buckypaper, for electromagnetic shielding and to enhance lateral thermal conductivity. Buckypaper membranes are being investigated by the AFRL for aircraft lightning strike protection, but could have application to help satellites from electromagnetic events.
Vertically aligned carbon nanotube arrays are being researched as heat sinks for the computer industry (see: Nanotechnology to the rescue of overheating computer chips) but it could be feasible to also apply them beneath a reflective coating on the satellite's surface for improved thermal dissipation.
Huntington writes that a much more futuristic use of these carbon nanotube 'forests' would be possible, in theory at least. And that's where we are getting close to the "shield" that is so popular and ubiquitous in science fiction space battles: "When energized with a small voltage at low pressure, carbon nanotube forests will emit electrons, which is the basis for their use as field emitters for plasma screen televisions. The emitted electrons ionize the atmosphere, generating a plasma shield around the structure. If the incident electromagnetic energy is short duration, the plasma should dampen most of the energy."
Huntington also mentions that, In conjunction with the AFRL, the University of Dayton has developed a method to tailor the electrical conductivity of polymer materials used to build commercial and military aerospace components. This project transforms almost any polymer into a multifunctional material capable of carrying or dissipating significant electrical charge. Specifically designed carbon nanotubes with the current carrying capability of copper but at a much lower density, on the order of 50 to 150 nm in diameter, were carefully dispersed into a polymer matrix resulting in an electrically conductive polymer composite.
Nanomaterial-based radiation shielding that protects against natural radiation in space is another research area (see our Spotlight "Nanotechnology in space ") that could also lead to protection from deliberate electromagnetic interference. Here, the paper describes that Northrop Grumman has demonstrated the feasibility of using nickel nanostrands as an electromagnetic shield for satellites. Nickel nanostrands are made from strands of sub-micron diameter nickel particles that are linked in chains from microns to millimeters in length. They are very similar to multi-wall carbon nanotubes, but have the electromagnetic, chemical, and metallurgical properties of nickel. Apparently, electromagnetic shielding that uses nickel nanostrands performs almost as well as current carbon fiber and aluminum shielding.
Although Huntington cautions that nanotechnology isn't yet mature enough to be considered a solution for protecting satellites from ground-based directed energy weapons, the USAF shouldn’t ignore it: "On the contrary, the USAF should continue investing in nanotechnology research and development to understand and harness its capabilities for protecting critical satellite systems because nanotechnology will have a significant impact on future satellite design."
He predicts that by 2025, nanotechnology will have a significant impact on United States satellites, touching on the structure and functions of all satellites in the form of radiation-hardened microprocessors, enhanced surface coatings, and reduced satellite size and weight. "In the near-tem, radiation-hardened electronics and surface coatings are likely to provide the greatest benefits toward protecting satellite systems from directed energy weapons. Structural enhancements derived from macro-scale nano-structures are likely at least 10-15 years away."
Another interesting comment he makes is that "nanotechnology research will likely be more relevant for the United States government (read: the military) than for the commercial sector". Hmm...