One big worry about space exploration is that hostile nations will deploy devastating weapons in space. The major international space treaty currently prohibits placing any weapons in orbit or on bodies is space such as asteroids, moons, etc. Recently the U.S. made a small change in the wording of legislation for the military that has big implications for the future deployment of weapons in space.
      The U.S. depends on its arsenal of nuclear weapons as a deterrent to attacks from other nations with advanced nuclear weapons and delivery systems. Missile defense systems have usually been considered a potential destabilizing influence because if a nuclear armed nation believed that it could block a counter attack from a nuclear armed enemy, it might to tempted to consider a first strike nuclear action.
       The U.S. policy for years has been for a limited homeland missile defense system that would be able to stop an attack from a nation with limited nuclear capability such as North Korea or Iran. The term “limited” is used in legislation governing the U.S. military to explicitly calm concerns by major nuclear powers such as Russia and China that it would ever launch a first strike in the belief that it could thwart their counter attack.
      Now, bipartisan majorities in both houses of Congress have quietly passed legislation regarding the national missile defense system that removes that word, “limited.” There has been virtually no national press coverage of this change and there was no public discussion. There is also a provision in the law that orders the Pentagon to start researching, developing and testing space-based systems for missile defense.
       It is estimated that the cost of even a “bare-bones” space-based missile defense system would be at least two hundred billion to install with hundreds of billions of dollars in operating costs after deployment.
      Now members of both national parties are beginning to react to this major change in U.S. policy. On the one hand, proponents of a space-based missile defense system say that it is absolutely necessary in today’s dangerous world. Opponents of such systems say that the idea that a space-based missile defense system could protect the U.S. from a major nuclear attack is sheer fantasy.
       Proponents of a new space-based missile defense system draw inspiration from the Star Wars initiative of the Reagan administration during the 1980s. It was supposed to use space-based lasers and other weapons to render nuclear weapons “impotent and obsolete.” Thirty billion dollars were spent and no weapons were ever developed and deployed.
      The primary Congressman behind the legislation, Trent Franks, said that taking the word “limited” out of the legislation and beginning work on new space-based weapons put “put the U.S. on a path to better safeguard its security.” He went on to say, “I hope that the day will come when we could have solid-state lasers in space that can defeat any missile attack. That day is a long ways off. But fortunately, it’s a little closer, and a little more certain, with the passage of these amendments.”
       A retired president of the missile defense system division of Lockheed Corporation said that such systems “defy the laws of physics and is not based on science of any kind. Even if we darken the sky with hundreds or thousands of satellites and interceptors, there’s no way to ensure against a dedicated attack. So it’s an opportunity to waste a prodigious amount of money.” He also referred to the new legislation as “insanity, pure and simple.”
       A former assistant secretary of Defense who was in charge of the Pentagon office that carried out testing and evaluation of weapons systems said that the idea of a space-based nuclear shield was a “sham”.
        Opponents are afraid that in addition to being a useless waste of money, our creation and deployment of such a system would give Russia and China an excuse to deploy nuclear weapons in orbit. This legislation is a very serious mistake and should be repealed. The last thing the world needs is a new arms race to put nuclear weapons in space.
Trent Franks:

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      The Air University is part of the United States Air Force’s Air Education and Training Command, headquartered at Maxwell Air Force Base, Alabama. For the past two years, a group of officers and students at AU has been participating in a program called Space Horizons. The group has been “exploring the implications for national security of the ongoing transportation and industrial revolution taking place in the commercial space industry.” The group believes that a small effort taken now can lead to exponential positive effects in the future.
       The SH group has decided to promote a bold new approach to the challenges of building a robust space industry in the U.S. where the U.S. space program can “help and promote rather than hinder or constrain” the evolution and expansion of private space efforts. In accordance with those goals, the SH group has put forward a draft of a National Space Policy for the U.S.
        The draft NSP opens with the declaration that “It is the policy of the United States that Space represents a domain of vast opportunity and commerce for all humankind.” The draft continues with the assertion that space ” holds the key to our species’ long-term survival and prosperity. Therefore, space is critical to our nation’s long-term survival and prosperity.” The draft says that one specific goal should be the creation of permanent space colonies. It also says that the U.S. should lead the world in responding to threats from space such as asteroids and solar flares.
      U.S. policy should be that space should be free to all nations for lawful commerce and national activities. The U.S. should make it clear that it will defend national interests against foreign interference in space and will protect the rights free access to space of other nationals as well.
       The U.S. should protect the ability of all nations and companies to navigate safely in space which will include monitoring and deflecting space debris which threatens navigation and infrastructure in space and on Earth. The U.S. should also work to prevent the use of space as a platform for weapons of mass destruction.
       The U.S. should engage in research to develop new propulsion technologies such as ion drives, fusion drives, solar sails and other advanced systems. Another goal of U.S. space policy should be to reach for the stars though probes launched to travel to other star systems.
      The U.S. should pioneer and share new technologies for the exploitation of space resources by mining valuable minerals from asteroids, moons and planets. The limitless sunlight in space should be harnessed to beam energy back to Earth to solve the energy crisis and mitigate climate change.
      Education should be a priority with new grants to provide resources to expand the workforce of professionals that can contribute to the exploitation of space. There should be support for establishing university departments and inter-university programs to support the space industry.
       The U.S. should compete with other nations to attract top talent and provide resources and assistance for the growth of U.S. space industries. This will include helpful regulation, loan programs, tax breaks and other government actions to support domestic space companies.
       As part of the National Space Policy, the U.S. should seek to achieve a number of “firsts” in space that will include:
1)  The U.S. should be the first nation to mine an asteroid.
2) The U.S. should be the first nation to mine propellant and minerals from the Moon.
3) The U.S. should be the first nation to create commercial transportation to and from the lunar surface.
4) The U.S. should be the first nation to create a propellant depot and on-orbit refueling service.
5) The U.S. should be the first nation to operate a private space station.
6) The U.S. should be the first nation to develop an Earth-to-orbit fleet of fully-reusable launch vehicles.
7) The U.S. should be the first nation to develop a prototype solar power satellite.
8) The U.S. should be the first nation to establish a hazardous asteroid early warning system and demonstrate an asteroid deflection capability.
       The U.S. must explore the creation of new institutions at home and abroad that can best support the expansion of the human race into space.
For the full draft from the Space Horizons group at Air University, see National Space Policy

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              The human race has an insatiable hunger for electricity. There are a number of different sources that supply our civilization with electricity from fossil fuels and nuclear reactors to renewable sustainable sources such as biofuels, hydro, solar, wind and geothermal. It would be best if we could obtain our electricity with minimum impact on the environment and human health. This pretty much rules out fossil fuels and nuclear fission power plants. Fusion power holds great promise but despite billions of dollars and decades, we have yet to demonstrate that it is even possible. Renewables hold great promise but there are problems with each source that have to be worked out in order to seriously expand their usage in the near future.
         There is future promise for a technically possible major energy source that will require enormous investment and overcoming a lot of challenges. This proposed power source consists of solar power collectors placed in orbit above the Earth which will beam energy in the form of microwaves or light to ground-based stations. This idea has been talked about since the early Seventies but we are finally entering an era of commercial space projects which might make it possible. This type of system is called space-based solar power or SBSP.
         With no atmosphere to block sunlight, the energy production would be higher than from solar collectors on Earth. The intensity of the unobstructed sunlight in orbit is about fifty percent higher than the best intensity ever found on Earth in ideal conditions. There would be no need to have a system to steer the collectors as the sun traversed the sky, or an omni-directional collection system. The sun would shine on the collectors twenty four hours a day throughout the year.
      There are significant challenges that would have to be overcome. Launching construction materials into orbit would be very expensive. It might be possible to lower the cost using material from the Moon or from an asteroid. The new  construction system from Tethers Unlimited for creating huge orbital structures from spools of carbon fiber would be a big help in this undertaking. Panels in the collector would suffer degradation at about eight times the rate of collectors on Earth in the harsh conditions of space. Space debris could damage the collectors. Using microwaves to transmit energy to the Earth rectennas could interfere with existing satellites. Converting the energy to microwaves and back to electricity would result in significant losses.
       Japan is working on SBSP. Japan passed the Basic Space Law in 2008 which singles out SBSP as a national priority. Japan is extremely poor in conventional power sources such as fossil fuels and uranium. The Japan Aerospace Exploration Agency has a “roadmap” for the development of SBSP.
       The China Academy for Space Technology presented their “roadmap” for SBSP at the International Space Development Conference. The Chinese roadmap called for a one gigawatt commercial power system by 2050. They showed a video and provided a detailed description of their proposed system.
        The U.S. Secretary of Defense, Secretary of State, and USAID Director sponsor the D3 competition every year. A proposal for a SBSP system won several awards in 2015. There is currently a petition on Change.org calling for the U.S. to develop SBSP.
        If technical challenges can be overcome and funding can be secured, SBSP would be an excellent source of sustainable power with minimum environmental impact.

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              I recently posted a two part articles about a new type of engine that apparently defies the laws of physics. Most of the focus was on what is being called the EM engine. It is a sealed truncated cone that functions as a resonant cavity for microwaves. The unique feature of these engines is that they do not require any propellant. In the post, I briefly mentioned another drive based on similar principles called the Cannae drive. The Cannae company has made some announcements recently about their drive and future plans that I thought merited attention.
        First of all, Cannae claims that their drive is not based on the EM drive design but rather their own proprietary design. They mention that it works on the basis of Lorentz Force imbalances but that is a phrase they coined to explain how the engine worked although their theories are not accepted by the physics community. In any case, the basic idea is that you can generate a measurable thrust by bouncing microwaves around in a metal cavity with nothing being expelled from the rear of the engine to push the craft forward.
       Cannae says that its engine can generate thrust from a few micronewtons up to full newtons. As far as I know, to date, these engines have only generated thrust at the very low end of that range. Cannae says that the low power, mass and volume requirements in addition to the lack of a need for any propellant makes their engines ideal for small satellites. CubeSat sizes are based on an approximately four inch cube that is referred to as a Unit.  
        Cannae has tested and demonstrated a version of their engine that requires superconducting elements. They are currently working on another version that will not require superconducting components. 
        Cannae has partnered with Theseus Space have partnered to actually test the utility of their new engine in space. Theseus Space is going to launch a CubeSat with a Cannae engine aboard. The engine will be used to allow the satellite to maintain an extremely low Earth orbit below one hundred and fifty miles for a period of six months. The Cannae engine will occupy a volume of about one and a half Units and will consume about ten watts from solar panels to accomplish orbital stability or what is called “station keeping.” If the tests are successful, Theseus will offer a commercial version of the Cannae engine.
       Cannae has published their plan for a system of Cannae engines to be used in a deep space probe. They claim that their design can propel a spacecraft weighing forty four hundred pounds one tenth of a light year over a fifteen year period. Five Cannae engines will be used to provide the main thrust of eighty five newtons. Another three smaller Cannae engines will steer the craft, and two even smaller engines will control roll of the craft. They are also working on a “space freighter” design for use in Earth orbit.
       Even though this engine appears to break the laws of physics, if they can get it to work as advertised, it will be a major break though in propulsion for spacecraft that will make the exploration and exploitation of space much easier and cheaper. Theories can be developed and revised later. However, I and many other people remain to be convinced. 

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              3-D printing holds great potential for use in space. Instead of having to send up many different components, new components and structures can be directly created in space with 3-D printers. So far I have blogged about 3-D printers that are now being used on the International Space Station, 3-D printers that are being designed to build structures in space that would be too big to launch with rockets and 3-D printers that could be sent to asteroids to create navigation and propulsion systems to move the asteroids to near Earth orbits. There are also proposals for the use of 3-D printers to create structures on the Moon.
       Siemens is a German engineering company that is the biggest engineering firm in Europe. It has offices all over the world. Siemens employs over three hundred and sixty thousand people and had profits of over eighty billion dollars in 2015. The principle divisions of Siemens are Industry, Energy, Healthcare, and Infrastructure & Cities.
        The Siemens company Product Design, Modeling and Simulation Research group in the Automation and Control Technology Field at Siemens Corporate Technology in Princeton, New Jersey is working on construction robots. They have designed what they call Siemens Spiders or SiSpis. These human scale SiSpis have legs for mobility and arms for manipulation. They carry 3-D printers that can extrude quick drying resins to build structures. The spider form created in nature by evolution is a very useful and practical design for a construction robot.
       SiSpis are able to communicate with each other and cooperate with what is called swarm technology that has been developed to allow robots to coordinate activity. Each robot has cameras and a laser scanned to allow them to perceive their local environment. They are able to decide what area of a structure their 3-D printing arm is able to reach. The structure is divided into 3-D boxes and each box is assigned to a particular robot. In this way, many robots are able to cooperate to build quite complex 3-D structures. The swarm has the capability to analyze a task and split it up between its members. It can also autonomously deal with problems and obstacles that it encounters.
       The current SiSpis robot design includes rechargeable batteries that carry about two hours worth of electricity. When a robot is nearing the end of that two hours, it halts work on its assigned area and travels back to a charging station. As it leaves its work area, it transmits information to a robot that has been fully charged so that that other robot can come to the work area and continue working where the robot with depleted batteries left off.  
      A swarm of SiSpis could be sent to the Moon to create the structures needed for a lunar colony. Their vessel could also carry solar panels that would be able to charge batteries during the two weeks of daylight every month. Their vessel could serve as their base of operations with master control computers and charging stations. When human astronauts arrived, they would already have habitable structures waiting for them.
Siemens Spider:

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Part Two of Two Parts
        For a brief period, Shawyer was collaborating with the Boeing company. There were supposed to be contracts for commercial development of the EM engine. Between 2008 and 2010, Shawyer and Boeing built and tested a EM engine which Shawyer claims worked as expected. However, when contacted in 2012, Boeing had dropped the project and simply said that they were no longer working with Shawyer. Shawyer continues to work on the EM design and has filed a series of patents.
        Another inventor named Guido Fetta created a similar engine which he named the Cannae drive. Its design had some differences from the EM drive but it is supposed to operate according to the same principles. Fetta created the Cannae company to exploit his invention.
        Scientists at a Chinese university built several engines based on cavity resonators and found a slight thrust which later turned out to be a measurement error. A group at NASA’s Eagleworks laboratories which was created to test unusual rocket engine designs built and tested versions of both the EM drive and the Cannae drive. They reported a very small amount of thrust which is close to their margin of error.
       The bottom line is that three different groups have built and tested these cavity resonator engines and none of them has been able to repeatedly measure significant thrust from their test engines. All their tests had problems with noise and experimental design.
       There are a variety of theories about what is happening with the cavity resonator engines. The simplest explanation is that there is no thrust and any measurements that say so are a result of noise and experimental error. Shawyer thinks that the thrust he says that he has measured is a result of unequal radiation pressure between the ends of the cavity. Experts say that his explanation of radiation pressure is not correct. The Eagleworks lab suggested that there may be something they called a “quantum vacuum virtual plasma” acting to create thrust. This idea has been strongly criticized by mathematical physicists who say that vacuum fluctuations do not form plasmas and, even if they did, it would not produce thrust. A scholar at Plymouth University claims that thrust from such engines is the result of quantization of inertia related to a hypothesized phenomena called Unruh radiation. Critics of this idea say that Unruh radiation has never been detected and that quantized inertia would violate special relativity. And, finally, it could be that these engines really are reactionless drives. Such an explanation is very unlikely because a reactionless drive would be a sort of perpetual motion machine. A reactionless drive would violate the conservation of momentum and Newton’s Third Law of Motion. Such a drive would have to be based on a new undiscovered physical law.
       In any case, Guido Fetta, inventor of the Cannae drive has announced that he will launch one of his drives into space aboard a CubeSat sometime in 2017. The drive will be tested in space for six months. NASA Eagleworks has tested their drive in a hard vacuum and registered a slight amount of thrust. They will soon publish their results in a peer-reviewed journal. Regardless of whether or not a reasonable theory of operation exists for these cavity resonator engines, if someone can actually test one in space and demonstrate that it works, it will mean radical changes for space propulsion.
EM Drive: 

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Part One of Two Parts
          I have written a number of posts about propulsion systems for spacecraft. There are many different existing and proposed systems utilizing different sources of energy and propellant. However, all of these systems share several properties. First, they all obey the known laws of physics. Second, they all have to throw something referred to as propellant out the back of the engine to move it forward. However, there is a new engine being tested that appears to violate these two properties. So far, the new engine has been tested in laboratories and does seem to generate thrust. I have been reluctant to discuss this new engine because it appears to violate the laws of physics. There is no agreed upon theory of how it operates. A version of the engine will soon  be tested in space.
         The force generated by rocket engines can be measured in what are called newtons named for Isaac Newton. “One newton is the force needed to accelerate one kilogram of mass at the rate of one meter per second squared in direction of the applied force.” The chemical rockets engines that powered the Saturn V rockets for the Apollo missions generated tens of millions of newtons. The most efficient plasma engines called Hall thrusters which use electric charge to expel ions for thrust can generate about sixty millinewtons or sixty-thousandths of a newton.
         Microwaves are electromagnetic waves with a frequency range from  three hundred megahertz to three hundred gigahertz and wavelengths between one millimeter and one meter. Because these wavelengths are the scale of objects in the human world, it is possible to control microwaves with physical constructs at the human scale. Metal tubes called waveguides can be used to channel microwaves and chambers called cavity resonators can be used to contain them.
       In 2001, Roger Shawyer created Satellite Propulsion Research. His new company was established with a grant from a U.K. government program to develop his electromagnetic or “EM” drive. The new engine is a truncated metal cone roughly the size of a loaf of bread sealed at both ends which functions as a cavity resonator. Picture a traffic cone with the top half cut off. It is powered by a microwave generator called a magnetron. In early experiments, Shawyer  claimed that the engine produced twenty millinewtons of thrust.
       Electromagnetic radiation can produce a slight force against a surface. Shawyer theorizes that the microwaves bouncing around in the cavity produce slightly more force against the larger end of the cavity than they do against the smaller end of the cavity which results in a net force that could provide thrust for a satellite or spacecraft.
       There was a burst of media attention when Shawyer announced his work but it was quickly met with great skepticism by scientists who pointed out that the engine violated the known laws of physics. Other laboratories could not duplicate Shawyer’s results and found that any apparent thrust was much smaller than he had claimed and could be the result of thermal effects.
Please read Part Two       
EM Drive:
 

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         On September 1st of this year, a SpaceX Falcon 9 rocket exploded at Launch Complex 40 at Cape Canaveral. The rocket was intended to carry a one hundred and ninety five million dollar Facebook satellite into orbit to extend the reach of the Internet to unserved areas in Africa. SpaceX lost another rocket earlier this year. SpaceX has a contract with NASA to ferry astronauts to the International Space Station next year.         The United Launch Alliance has a building in Launch Complex 40 that is about a mile from the launch pad where the explosion occured. “The ULA is a joint venture of Lockheed Martin Space Systems and Boeing Defense, Space & Security. The ULA was formed in December 2006 by combining the teams at these companies which provide spacecraft launch services to the government of the United States.” The ULA is a competitor of SpaceX for some government space services contracts.
         In early October, rumors started circulating that the Falcon 9 rocket may have exploded due to sabotage. There was a report of a “bang” sound just before the explosion. A review of video of the explosion revealed a strange shadow and a white spot on the roof the ULA building. SpaceX requested access to the ULA roof but access was denied. Instead, the Air Force sent investigators who said that they found nothing suspicious on the roof. SpaceX has not publicly stated that they thought sabotage caused the explosion. With respect to checking the ULA roof, SpaceX said that it was just trying to cover all bases to find out what caused the explosion.
         Earlier this week, SpaceX engineers revealed what they believe caused the explosion.  There are three carbon fiber helium tanks inside the main fuel tank called composite overwrapped pressure vessels. Apparently, one of the helium tanks burst as it was being loaded and the helium that was released caused the oxygen that was flowing into the main tank to freeze solid. A series of explosions were triggered by the frozen oxygen.
        The engineers said that they had never seen anything like this before. There was a conjunction of factors including the temperature of the liquid oxygen, the rate of flow of liquid oxygen into the main fuel tank, the behavior of the carbon-fiber in the helium tank, the rate of flow of the helium and the temperature of the helium. The engineers have been able to duplicate conditions that cause the helium tank to rupture. It will be difficult to fix the problem because of the different factors involved.
        On November 4th Elon Musk, the CEO of SpaceX, appeared on the CNBC cable network and said that SpaceX had discovered the cause of the explosion of the Falcon 9. He verified what the engineers had said, that the cause of the explosion involved liquid helium, liquid oxygen and carbon-fiber materials used in the construction of the rocket. Musk said that since the problem had been identified, he was confident that SpaceX could resume rocket launches in December. SpaceX had better solve the helium loading problem quickly to remain competitive. It has already lost a ISS supply launch to another space services company called Orbital ATK. 

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              My last three posts have been about a company called Tethers Unlimited and their technologies for space exploration and exploitation. Today’s post will be a final look at exciting developments at Tethers Unlimited in the area of building structures in space.
       Currently, the size of structures that can be sent into space is limited by the space inside the payload stage of our heaviest lifters. It is possible to fold up a payload and unfold it in orbit but size is still severely constrained. Tethers Unlimited is working on going beyond the limitations of payload space for space structures.
       From Wikipedia: “In engineering, a truss is a structure that ‘consists of two-force members only, where the members are organized so that the assemblage as a whole behaves as a single object’. A ‘two-force member’ is a structural component where force is applied to only two points.” Tethers Unlimited is developing systems for constructing and deploying trusses in space. The struts for the truss are made from a spool of carbon fiber, a very strong and light material. Tethers Unlimited has developed a system that can assemble and extrude a straight section of truss made from fiber.
        Once a section of truss has been created, then it will be necessary to attach it to other sections of truss as well as satellites, space craft and space stations. This further stage of construction can be done by human beings in space suites but it would be better to have some sort of robotic system that could move around on the structure and attach new sections where needed. Tethers Unlimited are working on something they call SpiderFab. They did not set out to create a robot that looks like a spider but found that four limbs for mobility and four limbs for manipulation were a good configuration and just happened to match the eight limbs of spiders. The SpiderFab also carries a “spinneret” in the form of a spool of carbon fiber.
         With the Tethers Unlimited truss construction system, big structures can be built in space such as solar arrays to supply clean energy to Earth stations. Another application will be to create “real estate” in orbit. Now, when a satellite is sent up to geosynchronous orbit, it has to carry its own platform. If a big truss structure was created in geosynchronous orbit over a particularly useful location such as over a major urban center , then cheaper and less complex satellites could be launched and their payloads attached to the truss structure.
        Further in the future, when asteroids are being mined, it is possible that basalt from an asteroid could be turned into a fiber that could be used to construct space trusses. This would mean that carbon fiber would not have to be sent up to orbit for uses as a construction material.
         Tethers Unlimited is an innovative company that is at the forefront of creation of tools, systems and materials for exploring and exploiting space.
SpiderFab

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              My last blog talked about propulsion systems for CubeSats that used water as a propellant. These thrusters are a commercial product of a company called Tethers Unlimited. They have other products that are being marketed or being developed for space applications. One of these other products involves software defined radios for communication with and between satellites.
        There are a number of bands in the electromagnetic spectrum that are assigned for use on satellites. These bands are regulated by the Federal Communications Commission or the Department of Defense for companies operating in the U.S. One of the problems for companies launching satellites is the time lag between applying for a frequency and receiving authorization. Traditionally, when a frequency is assigned, a crystal tuned to that specific frequency is installed in the radio receiver and transmitter. Sometimes the authorization comes so late that there are only days left until the satellite is scheduled to launch. This means that the satellite has to be taken apart and the crystal installed quickly.
        Tethers Unlimited has developed a solution to this problem. Instead of a physical crystal that sets the frequency, their line of SWIFT radios use software to define the operating frequency. This means that the frequency can be set electronically prior to launch of a satellite without the need to disassemble the satellite. This results in savings in time and effort. The SWIFT radios are intended for use in CubeSats and other small satellites. They have AES-256 bit encryption built in.
       The SWIFT radio series comes in several versions dedicated to different frequency bands. The family of SWIFT-SDRs includes:
SWIFT-UTX is used for UHF Satcom and Wideband TT& C frequencies. It is compatible with 10 watt UHF transmitter and a Dual-Channel UHF receiver.
SWIFT-SLX is used for S-band SGLS/USB/ISM transceivers. It is compatible with 10 watt UHF transmitter and a Dual-Channel S-band transceiver.
SWIFT-XTS is used for 300 Mbps X-Band Downlink + S-band SGLS/USB/ISM transceivers. It is compatible with 10 watt X-band transmitter and a Dual-Channel S-band transceiver. It is also compatible with an X-band receiver and a 10 watt X-band transmitter.
SWIFT-KTX is used for the K-band of frequencies. It is compatible with a 1 watt K-band transmitter and a K-band receiver.
All of the SWIFT software defined radios share a common software module referred to as SWIFT-LINK which “provides abstracted and frequency-agnostic multi-network, multi-channel, full-duplex communications support.”
        Tethers Unlimited also has systems that incorporate the software defined radios.
SWIFT-RelNav provides relative navigation, synchronization and inter-satellite communication for fleets of satellites without the need for an external reference signal.
SWIFT-AFSCN is a programmable SGLS/USB CubeSat radio that is used to communicate with AFSCN ground stations. It allows simultaneous reception on both the SGLS and USB bands and transmission on the S-band.
SWIFT-TacSatComm  is a UHF CubeSat communication subsystem. It allows the satellites to communicate with military handheld radios.
SWIFT-WRX is currently under development. It is intended to permit CubeSats to receive a wide range of frequencies. The first model will handle frequencies from 50 MHz to 7 GHz. A future model will expand that to 50 MHz to 19 GHz.
        While  a few satellites might carry out their tasks without communications, for the vast majority of satellites, communications are critical to their purpose. Tethers Unlimited provides a wide ranges of software defined radios for use in space exploration and exploitation.

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