My last blog talked about space tethers. One of the pioneer companies researching space tethers is Tethers Unlimited. They have been around for over twenty years and for many of those years they subsisted on occasional grants. In the past few years, their focus has shifted away from space tethers and onto other space technologies that are more in demand. One of the products they are now selling is the Hydros Water Electrolysis Thruster or Hydros Propulsion System.
      Satellite launches are very expensive. Millions of dollars are involved in sending a big satellite into orbit. There is often some room left in the payload of a major launch and this space is sold to other companies for the launch of small satellites such as CubeSats. CubeSats were developed in 1999 by California Polytechnic State University and Stanford University to promote the design, manufacture and testing of small satellites intended for low Earth orbit. The size of CubeSats is measured in ten by ten by eleven and one third centimeters volumes which are referred to as “units”. They cannot be over one and one third kilograms per unit.
      Hitching a ride on a big satellite launch makes it much cheaper to get CubeSats into orbit. However, the CubeSats are just dumped into space when the big satellite reaches its orbit. This leaves the CubeSats in the wrong orbit. In order to reach the correct orbit, the CubeSats have to have some sort of propulsion system to provide thrust.
       There are many options for propulsion for these CubeSats. Pressurized tanks of cold gas such as nitrogen can be used but they have very low performance. Chemical thrusters require propellant which is not allowed when launched with a big satellite. Various electrical thrusters are being researched including Hall-effect thrusters, ion thrusters, pulsed plasma thrusters, electrospray thrusters, and resistojets. However, these require a lot of power which means big solar cells and/or batteries. Some require pressurize propellant which is not allowed in piggy back launches. Solar sails could be used but they take up a lot of space and require complex system for deployment.
       Tethers Unlimited has developed a propulsion system for CubeSats that solves many of the problems with other CubeSat propulsion systems. The satellites are launched with water onboard. Once they are dropped off in space, they can deploy solar cells to charge the batteries. The batteries can then power an electrolysis system that separates the hydrogen from the oxygen in the water. The CubeSat now has fuel that can be used in a bipropellant thruster to generate thrust and alter its orbit. Once a new orbit has been achieved, the fuel can be used for station keeping. The Hydros thrusters are efficient and powerful. The Hydros currently comes in two versions. One unit and one half unit.
       The Hydros is a pulsed propulsion system than cannot provide a constant thrust. However, the company has been working with putting multiple propulsion modules on the same CubeSat so one module can be generating the gases while the other module is firing.
Hydros thruster:

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       Over ten years ago, I attended a conference where there was a presentation on tethers for moving things around in space. I was fascinated. We tend to think in terms of powerful rockets for our current space propulsion and maybe someday warp drives that can overcome the speed of light. But here were people talking about using long cables to move things around in space. There are a number of different things that can be done with tethers.
       One application for tethers is referred to as electrodynamic tethers. This idea makes use of the magnetic fields of the Earth. Basic electric theory says that a conductor with a current flow moving through a magnetic field will experience a physical force. By dangling a long tether from a satellite and running a current through it, it is possible to use the force created by  the Earth’s magnetic field to impart a force to the tether which is transferred to the satellite. Run the current one way and the satellite is slowed down. This will move it to a lower orbit. This is useful for what is called deorbiting or causing a satellite to fall out of orbit and burn up in the Earth’s atmosphere. Run the current the other way and the satellite can be pushed up into a higher orbit.
       Tethers must be strong and light. They may be coated to protect them against atomic oxygen in the upper atmosphere and against ultraviolet light, both of which can degrade them. There is also the problem of micrometeorites damaging the tethers. Various polymers, fibers, composites and conducting wires are now used for tethers. In the future, carbon nanotubes look promising with their extreme strength and very low weight.
       Momentum exchange tethers can latch onto a satellite or package  and, rotating up or down, move it from a higher orbit to a lower orbit or from a lower orbit to a higher orbit. They can also pick up and deliver packages from the ground to orbit or from orbit to the ground. This application is referred to as a sky hook. And they allow an orbiting satellite or spacecraft to flung out of the Earth’s gravity well altogether.
      With tether formation flying, tethers can be used to adjust the position of each satellite flying in a formation of satellites so a particular configuration can be maintained.
       Electrodynamic tethers can also be used to impart momentum to a spacecraft by interacting with the solar wind streaming out from the sun.
       Perhaps the most ambitious use of space tether ideas was first proposed by a Russian in 1985. He pointed out that if a cable could be dropped from geosynchronous orbit down to the Earth and rotate with the Earth, materials and equipment could be sent to and from geosynch orbit with an elevator. This idea came to be called a space elevator and there is a Japanese company that has announced plans to try to build one by 2050.
       Tethers were all the rage years ago but as time went by, research stalled and projects and grants were cancelled or never awarded. Currently tethers are not a big part of the budding space industry but with the passage of time, development of material science and experience in space flight, tether may yet achieve a new popularity and many applications.
Graphic of the US Naval Research Laboratory’s TiPS tether satellite:

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              There is a lot of interest in asteroid mining these days in the space industry. Huge amounts of important and useful metals could be recovered from one type of asteroid. Another type of asteroid could supply hydrocarbons which can be used in the manufacture of a number of import industrial products such as plastics and medicines. In addition to a source of raw materials, other uses for asteroids have been suggested. One popular idea would be to hollow out and colonize an asteroid. Another idea that has been tossed around for a long time is the idea of using asteroids for transportation. All of these possible uses share a common interest in ways of changing the trajectory of an asteroid. In other words, how would it be possible to turn an asteroid into a vehicle.
       A California company named Made in Space has just received a grant from NASA to research how to turn asteroids into autonomous spacecraft. The project is called Reconstituting Asteroids into Mechanical Automata. A co-founder of Made In Space told Space.com that, “Today, we have the ability to bring resources from Earth into space. But when we get to a tipping point where we need the resources in space, then the question becomes, ‘Where do they come from and how do we get them, and how do we deliver them to the location that we need?’ This is a way to do it.”
        The RAMA plan would start with sending robotic “Seed” spacecraft out to rendezvous with near-Earth asteroids. These spacecraft would land on the asteroids and use 3D printing and other technologies to construct propulsion, navigation, energy-storage and other systems from materials on the asteroid. The systems envisions for the asteroids would be quite simple. The navigation computer might be mechanical. The propulsion system would be some sort of a catapult that would literally throw material off the asteroid in order to propel it in the other direction. Once properly outfitted, the asteroids could be programmed to fly to any place they were needed such as a asteroid mining facility.
      Made in Space has expertise in 3D printing in space. They produced two 3D printers that are being used in the International Space Station. 3D printers exist that use 3D printer parts which is ideal for bootstrapping operations on an asteroid. Mechanical computers exist that are made up of 3D printed parts.
       In addition to using the RAMA system to deliver asteroids for mining, there are other possible uses. If the orbits of near-Earth asteroids could be altered sufficiently, it might be possible to construct a system of asteroid “barges” that could obit between Earth and Mars on some sort of regular schedule. Even if these asteroids to months to years to move between the two planets, they would provide for the transport of huge amounts of supplies and large numbers of human beings. In addition, tunnels dug into the asteroid could provide safety for human beings from dangerous space radiation.
        And finally, hollowed out and given a spin, an asteroid could both protect against radiation and provide enough artificial gravity to remove two of the biggest impediments to living in space. Light pipes and mirrors could bring sunlight into the interior of the asteroid which would supply the light needed to grow crops for the human crew.
 

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       I have been blogging about propulsions systems lately. All things being equal, we would like to move through space as quickly as practical because the longer a journey takes, the more exposure of a human crew to health damaging radiation, the more negative health effects of zero gravity and the more food and water required for the journey.
        Lately there has been a lot of talk about visiting Mars. One benchmark for propulsion systems is how long it would take to travel to Mars. With current propulsion systems, NASA says that it will take about six months to get to Mars. There are other propulsions systems being developed that could get a manned expedition there more quickly.
       Science fiction has been full of light propulsion systems for decades. Often the sun itself provides the push for the sail but giant Earth-based and space-based lasers have also been used in stories. Light based propulsion has been tested with small sails and tiny payloads and has been shown to work as expected.        Laser sail propulsion is simpler than solar sail propulsion because the frequency band of the light is very narrow and it is easy to develop a sail that reflects almost all of the light and absorbs very little.
       There has been a lot of research and development in recent decades to make lasers ever more powerful. If lasers can be made powerful enough, they can be used as weapons, triggers for nuclear fusion and space propulsion. Because there are big problems with scaling up single lasers to high power, one popular current approach is to make an array of lasers which can be fired in phase and aimed at the same target. In order to propel a spacecraft, an Earth-based array of lasers could be built that could project megawatts of energy at the sail attached to the craft that would be already be in Earth orbit.
       A NASA scientist named Philip Lubin has been working on a system that would utilize a giant array of Earth-based lasers to propel spacecraft attached to a light sail to Mars. He claims that such a system could carry a small space probe to Mars in a matter of days. A manned space mission could get to Mars in thirty days. Lubin and his team have received a proof-of-concept grant from NASA to pursue his ideas under a project named DEEP-IN.
         While laser propulsion sounds good, there are some technical hurdles that must be overcome in order for it to become a practical way of propelling spacecraft. In order for the lasers to deliver their light to the sail, they have to collimated very precisely which will be difficult. The next problem is the fact that the spacecraft would be difficult to steer. There would need to be some system that could change the orientation of the sail. Then there is the question of how to decelerate such a craft once it had reached its destination. One system for deceleration is to have concentric rings of sail. Approaching the destination, a central disk could detach from the circular sail and the large outside ring could be used to focus light on the back on the central circle which would cause it to slow down. And, in addition to the technical problems that will have to be solved, there is the fact that the laser array would be very expensive to build and maintain.
       While the idea of laser propulsion may be attractive in the abstract, it will be decades at the very least before it is a practical way to send significant payloads through space. Even tiny space probes propelled by light are far in the future. If the technical challenges can be met, lasers may someday propel probes out of the solar system at significant fractions of the speed of light. Laser arrays build in space could use solar energy to generate extremely power beams.
NASA NanoSail-D:

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       Today to get people and payload to Earth orbit and beyond, a huge rocket burning tons of dangerous fuels at great expense in necessary. If the human race is ever going to seriously explore and exploit space we are going to have to find a much cheaper, more efficient and easier way to send people and things into orbit and beyond. The Chinese are working on a “spaceplane” that could accomplish these goals.
       The China Aerospace Science and Technology Corporation is developing a hybrid plane and spacecraft that will be able to take off from a runway like a conventional plane and then ascend all the way to Earth orbit. It will be able to reverse the journey and descend from orbit to land on a runway. The spaceplane will be able to be checked and refueled quickly to be used again. This reusability will substantially reduce the cost of reaching Earth orbit. The combined cycle engine will propel the spaceplane more slowly than a conventional rocket launch. The journey to space will be much less stressful and will not subject the passengers to the brutal G forces of a conventional rocket launch.
        When the spaceplane takes off from the runway, it will be powered by a conventional turbofan or turboprop engine. Then a ramjet will take over to carry the spaceplane up through the atmosphere. When the spaceplane achieves supersonic velocity, it will change over to a scramjet engine that will send it from twelve miles to about sixty miles altitude which is considered to be the edge of space. When the spaceplane reaches the edge of space, it will use a rocket engine to raise it into Earth orbit.
       The Chinese spaceplane which is being referred to as a “hypersonic shuttle” will be developed over the next three to five years. They are leading the field in research on the type of combined cycle engines that will be required for the hypersonic shuttle. However it will still be a serious challenge to integrate all these different propulsive capabilities into a single engine. A second big challenge will be to develop an airframe that is light enough to be economical and strong enough to withstand the stress of hypersonic flight and reentry from orbit. The Chinese hope to be able to put the hypersonic shuttle into regular service by 2030.
       The British are working on a similar spaceplane concept called the Skylon. It will rely on a new technology that will super cool the air intakes for the supersonic portion of the flight instead of using a scramjet as in the Chinese design. The British hope to have their Skylon spaceplane ready for regular service around 2030, the same date that the Chinese are working toward.
        The U.S. is falling behind in the spaceplane race. If the U.S. does not develop its own hypersonic spaceplane, it will be at a disadvantage in the global space marketplace behind the Chinese and the British. Billions of dollars will be spent on space exploitation in the coming decades and the U.S. will lose out on a great deal of business if they do not have an operating spaceplane.
Artist’s concept of British Skylon Spaceplane:

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       Conventional rocket engines have reached a high level of efficiency. However, the space industry is always working on improving the propulsion systems used in space flight. The pulse detonation rocket engine was conceived by Soviet scientists and has been researched for over seventy years. If it can be perfected, it will significantly exceed the capability of current rocket engines.
        In a PDRE, the fuel and oxidizer are injected into the combustion chamber and then compressed with a detonation wave before being ignited. The “pulsed” in the name refers to the fact that the fuel and oxidizer are injected into the combustion chamber in pulses and are not fed in continuously. These type of engines will exceed conventional engines in thermodynamic efficiency. Moving parts such as compressor spools are not required to compress the fuel/oxidizer mixture which reduces the weight and complexity of the engines. Impediments to a working PDRE include the problem of fast and efficient mixing of fuel and oxidizer, the prevention of spontaneous autoignition of the fuel/oxidizer mix and optimal integration with the inlet system and the exhaust nozzle.
       Most current rocket engines burn their fuel/oxidizer at a subsonic velocity which results in problematic pressure differentials as the fuel/oxidizer mix burns. The PDRE burns its fuel/oxidizer mix at a supersonic velocity so the burn is smoother at a constant volume. However, in order to insure that all the impulse of the burning fuel/oxidizer in a rocket engine is shot out of the nozzle, it is necessary to block the passage back into the engine from the combustion chamber. The speed of the burn in the PDE makes it very difficult to close the inlet quickly enough to prevent blowback. The intended cycle time of a PDE is thousands of times per second which will help smooth out the vibrations generated by pulsing the fuel/oxide burn. This process will also generate greater noise than conventional engines.
        Another problem for PDREs is how to efficiently ignite the fuel/oxidizer mix. In order to get the supersonic burn required, a subsonic burn is started and then accelerated down a special tube with obstructions that are designed to split the advancing burn into multiple streams. This is difficult to model and engineer.
         Now the Russian Advanced Research Foundation working in conjunction with Energomash has announced the creation and testing of a full sized PDE. The engine burns kerosene for fuel and oxygen for oxidizer. The Russians intend to develop their PDE for use in missiles and space vehicles. If they can deliver a working PDE, the Russians will have the most advanced rocket engine among space-faring nations. This will give them a significant advantage in the exploring and exploitation of space. If the Russians succeed in the development of the PDRE, other countries competing in the exploitation of space will have to develop their own PDREs or be left behind.
       Companies and agencies in the U.S. have been working on pulse detonation rocket engine designs for over twenty years but have yet to produce a working model that could be commercialized. With the Russian announcement, the pressure will be on the U.S. space industry to ramp up their efforts to develop a PDRE.
Logo of Energomash, a Russia space research company:

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       Until recently, the exploration and exploitation of space was a dominated by national governments which could bear the tremendous expense of launching payloads to orbit and beyond. But now there are many private companies that have entered the space race. These companies are developing their own launch capability and looking for ways to profit from access to space. One big factor in the commercial exploitation of space is the drafting of new laws which will permit private ownership of resources obtained from asteroids, moons and other planets.     
        Some companies are launching satellites for other companies. There are companies that are working on developing the ability to mine metals on asteroids and return them to Earth. More ambitious private projects include working on plans for the private exploration of the planet Mars. The Moon is also a target of great interest. There are many minerals there that could be mined. It may  also be possible to mine the Moon for profitable resources such as Helium 3 which could  be used in nuclear fusion power plants.
         Moon Express is a Cape Canaveral company founded by dot-com billionaire Naveen Jain, Bob Richards and Barney Pell in 201 “that plans to offer commercial lunar robotic transportation and data services with a long-term goal of mining the Moon for resources, including elements that are rare on Earth, including niobium, yttrium and dysprosium.” The company also wants to mine the Moon for profitable metals such as titanium and platinum.
       Moon Express has developed and tested its spacecraft MX-1 which will be launched as a secondary payload by Rocket Labs which has contracted with Moon Express for three launches. Moon Express has also developed the MTV-1X lunar lander and flown it on test flights.
       Under the U.N. 1967 Outer Space Treaty, any private individual or organization that wants to land on the Moon has to get permission from the appropriate national government which, in the case of Moon Express, is the U.S. Government. The approval by the Federal Aviation Administration of the request by Moon Express represents the first time that a private company has been granted permission to launch a spacecraft that will travel to and land on another celestial body.
       Moon Express plans to launch the MX-1 in 2017 that will carry the MTV-1X lunar landing module that which is about five feet in diameter. After landing, the MTV-1X module will move around the lunar surface to explore the area near the landing site.
       If Moon Express can successfully carry out its mission to land a vehicle on the surface of the Moon, it will be in competition for Google’s twenty million dollar Lunar X-Prize. In order to win the competition, the Moon Express lander will have to travel at least five hundred meters. It will also have to send back high resolution still images and videos.
       Winning the Lunar X-Prize would bring in millions of dollars that could be used for further research and development of the Moon Express lunar project. The publicity would also be worth millions of dollars and would draw in other investors.

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       Currently, exploration of space is governed by the U.N. Outer Space Treaty of 1966 which covers scientific exploration and commercial exploitation of orbits and bodies in space. Over one hundred nations have signed it. It prohibits putting nuclear weapons in space, prevents individuals, companies or government from claiming astronomical bodies and territory on moons and planets and makes nations responsible for any damages caused by their space programs, their private space industry and/or their citizens involve in space activities.
       When and if a significant number of human beings take up residence in space, the question of laws governing individuals and communities will arise and law enforcement and courts will be necessary. There was a good TV series called Star Cops in 1987 on British TV that dealt with police on the moon.
       Astronauts are carefully vetted for psychological stability and the ability to follow rules closely. In part, their survival depends on it. As space tourism and industry evolve, more and more people will be traveling into space and the quality and universality of vetting will decline. There will need to be a legal framework of some sort to deal with misbehavior.
       There is a Draft for A Convention on Manned Space Flight from 1991 that proposes a chain of command which makes the commander of a spacecraft responsible for the actions of the crew and mandates that the crew must answer to the commander and the director of spaceflight operations.
        Aviation law is often consulted for ideas that may be applicable to space law. The Tokyo Convention of 1963 authorizes the pilot of an aircraft to take appropriate actions against any passengers who are being disruptive. While not a comprehensive framework for space law, the TC is a good start.
       The International Space Station is governed by an intergovernmental agreement. Each nation that is participating in the crewing of the ISS has criminal jurisdiction over any of their nationals who are on the ISS. The ISS commander has ultimate authority over the whole crew regardless of nationality. There are provisions for chain of command, ground to space procedures and disciplinary measures. There is, as yet, no such thing as a space “jail” but some sort of incarceration facility will eventually be required.
       It may be necessary to apprehend and immobilize people who commit crimes on spacecraft, space stations or stations on moon or planets. Given that there is hard vacuum outside spacecraft and space stations as well as stations on moons, some sort of non-lethal immobilizing weapon such as a dart gun would be preferred to a projectile weapon that could pierce a bulkhead or wall.
      It will also be necessary to increase security provisions for life support systems and airlocks in case someone tries to sabotage life support or open an airlock. Biometrics will be preferable to code entry keypads because codes can be stolen. There will have to be increases security with respect to items being shipped into orbit to prevent smuggling of contraband including weapons and drugs.
      Unfortunately, in any population of human beings there will always be some who will not follow the rules and could pose a threat to themselves and/or others. The expansion of the human race into space will not be exempt from this problem.

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        Space is not a friendly place. As the human race has sent explorers beyond the atmosphere into space, we have been discovering just how unfriendly it is. To start with, it is a vacuum which would destroy an unprotected human in minutes. It is also very cold and, unless exposed to sunlight, an unprotected human would freeze to death in moments. The sunlight would burn an unprotected human in minutes. In addition, there are a number of physical problems that being in space can cause even if the human being is protected from the vacuum and cold.
       It turns out that spending extended time in space causes human bones to lose calcium and become brittle. On Earth, the force exerted by gravity results in the stimulating electrical fields in the human body that lead to the deposition of calcium. In zero gravity conditions, this mechanism fails. There has been some discussion of using special body suits that would restore the normal electric fields.
      On Earth, in normal conditions, the muscles of the body are constantly working against gravity to maintain body postures. In zero gravity conditions, there is not such constant effort on the part of muscle so they also tend to weaken and atrophy in the weightlessness of space. Rigorous exercise regimes will help with this problem.
             A few years ago it was found that astronauts who spent significant time in space were having vision problems upon returning from space. Upon examination it was found that their eyeballs were slightly flattened. Once again, the lack of gravity turns out to be the probable cause. Our biological systems are designed to work against gravity to distribute fluids around the body. When gravity is gone, the fluids redistribute causing distortions in certain body parts.
       It is impossible to maintain an absolutely sterile environment for astronauts. The human body contains and either coexists or fights off many bacteria. Unfortunately, it turns out that some nasty bugs become hardier and more infectious after time in zero gravity. Reinforcement of the human immune system might be necessary to deal with this.
      All of the problems mentions above could be alleviated if we could restore gravity. If we had spacecraft and space stations with sections that could rotate, it might be possible to create a simulated gravity field that would deal with these physical issues.
      There is dangerous radiation in space from the sun and cosmic rays that can cause tissue damage to astronauts resulting in potential health problems. Proper shielding can reduce but not totally eliminate the radiation problem. There are also periods of powerful solar eruptions that spew especially dangerous amounts of radiation into space. There are some organism on Earth that have special mechanisms to reduce radiation damage. Future astronauts may need some sort of genetic manipulation against radiation damage.
      The most recent problem with space flight to emerge is danger to the cardiovascular system. Astronauts who went to the moon were found to be at greater risk for cardiovascular disease upon their return. It turns out that radiation in space is apparently damaging the vascular endothelial cells which can lead to occlusive artery disease.
       As I said, space is not a friendly place. All of these problems have existing or theoretical solutions but they make extended stays in space more difficult and dangerous than was understood before we ventured into space.
Vascular endothelial cells:

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        The Future Space Leaders Foundation is “a tax exempt 501 c 3 non-profit organization dedicated to the career development of young space and satellite industry professionals.” Education of space professionals is one of the main focus of the Foundation. The Foundation collaborates with and supports a number of other space focused non-profit and commercial space organizations. The Foundation holds annual educational events and dispenses  grants to young professionals to enable them to attend conferences of other space related organizations. 
        The mission of the Foundation is:
“To advance learning and professional enrichment of young space professionals and future leaders pursuing careers in the fields of space and satellites.
To stimulate the professional growth and enhancement of future space professionals and to foster cooperation and interaction among current leaders in the space field with graduate students and young professionals seeking to pursue careers in the fields of space and satellites.
To assist graduate students and young professionals in attending space and satellite industry conferences and events through grants covering legitimate travel and registration related expenses.”
         At the Future Space 2016 conference held by the Foundation in July of 2016, Lt. Gen. Jay Raymond, a senior space official of the U.S. Air Force spoke about the importance of advanced space capabilities to the all facets of the mission of the Air Force.
         For the next six years, the U.S. Department of Defense has budgeted six billion six hundred million dollars for space protection which includes both commercial satellites and ground systems as well as military satellites and ground systems that protect the U.S. from a variety of threats from hostile groups and nations. Raymond referred to this budgeting as a “renaissance.” The U.S. has steadily developed and deployed new space technologies and systems that are important to the economy of the U.S. as well as defense of the country. While the new systems give us new capabilities, they also represent new vulnerabilities. This requires even more new technologies and systems to protect our civilian and military space resources.
       One of the new ideas being investigated for increasing the resilience of our space resources is called “disaggregation.” The basic concept is to distribute capabilities across smaller, simpler and cheaper satellites. This will make expansion of our civil and military space resources easier, more affordable and more resilient in the face of natural and man-made problems. The Air Force is considering disaggregation of both the missile warning defense system called the Space Based Infrared System satellite network and the critical military communication Advanced Extremely High Frequency satellite network.
       Raymond emphasized that as the U.S. has steadily built up the range and sophistication of our civil and military space capabilities, major nations which may be enemies in the future has also been building up their space capabilities. There have been recent demonstrations of the ability of such nations to disable or destroy satellites either from ground based lasers or space based attacks. This danger can be partially mitigated by the expansion of our fleet of civil and military satellites with cheaper and simpler satellites creating many more targets for any adversary.

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