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Part Two of Two Parts
       In contrast to the frantic activity preparing the Atlantis and the astronauts on the ground, there would have been little to do on the Columbia. Following EVA to check on the wing damage and make preparations to move to the Atlantis, the only other preparations would be to maneuver the Columbia into an upside down orbital orientation with the tail pointed in the direction of flight. This would require minimum expenditure of propellant. For the crew of the Columbia, the stress of inactivity while waiting for rescue by the Atlantis would have been difficult to endure. They would not even be able to watch what was happening because all cameras and television equipment would be shut down to conserve power.
        The International Space Station was in orbit around the Earth. The question could be raised of why the Columbia didn’t rendezvous and dock with the ISS where the crew could find refuge. Unfortunately, the Columbia only had a tiny fraction of the fuel that would have been required to carry out the necessary change of orbit to rendezvous with the ISS. 
        A major concern about a possible rescue mission by the Atlantis had to do with what had happened to the Columbia. Foam had broken off the same place on previous space shuttles at least six times before the Columbia was launched. Once it was establish that such detached foam could fatally damage the integrity of a shuttle, the question had to be asked, “What if we launched the Atlantis on a rescue mission and a piece of foam broke off and seriously damaged the Atlantis too? Is that a risk worth taking to rescue the crew of the Columbia? There was no time to redo the foam insulation on the external tank for the Atlantis.
        There were three days in mid-February that could have provided launch windows for a rescue mission. One big concern about scheduling launches is weather. The weather has to be calm not just for the launch itself but also for possible emergency landing sites in case the mission had to be aborted. Records show that the three days in question had clear weather forecasts. However, all three launch windows were at night which would make it much more difficult to assess possible foam damage to wing tiles of the Atlantis after launch.
       If the Atlantis was successfully launched it would have approached straight up below the Columbia. The Atlantis would approach within twenty feet of the Columbia at right angles to the Columbia to prevent their tails from colliding. The two pilots would trade off holding the Atlantis steady with respect to the Columbia for the estimated nine hours of the transfer.
       The bays of both shuttles would be opened and the two EVA crew members would begin to move the crew of the Columbia to the Atlantis. Two space suits would have to be recycled which is what would make the transfer operation last so long. Putting on space suits and taking them off is a difficult and time consuming operation. The last two crew to leave the Columbia would make final preparations for ground control to deorbit the Columbia. The combined crews of the two shuttles would strap in and, hopefully, successfully land back on Earth.
       Such a rescue mission would have been extremely difficult but might have succeeded if we had known about the problem with the shattered tile soon enough. After the CAIB report was issued and the shuttles flew again, a new protocol was put into place. With the first launch in 2005 after the grounding of the fleet, no shuttle ever flew again without a rescue shuttle standing by, ready to launch in case there was a problem. Fortunately they were never needed.
Launch of the Columbia:

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Part One of Two Parts
        On January 16, 2003, the space shuttle Columbia was launched into Earth orbit from the Kennedy Space Center in Florida. During the launch, a piece of insulating foam tore loose from the external fuel tank and smashed into the leading edge of the Columbia’s left wing. The foam strike was revealed after the Columbia was in orbit and the film of the launch was examined. Foam strikes had happened before and Mission Control decided not to have images of the wing taken to examine for damage.
        It turned out that at least one of the critical reinforced carbon heat shield tiles had been shattered by the foam.  This resulted in a large hole being torn in the ceramic material of the wing. Sixteen days later the Challenger completed its mission and, on February 1st, 2003, the Columbia descended from orbit. During re-entry, superheated gas poured though the hole in the left wing and the Columbia began to disintegrate. Contact with the Columbia was lost at Mission Control and they realized that the shuttle had been destroyed. Seven astronauts lost their lives when the Columbia was torn apart.
        The Columbia Accident Investigation Board was created by Congress and charged with the responsibility of finding out what had caused the disaster. In August of 2003, the CAIB completed its investigation and issued its report. It was concluded that while the direct cause of the disaster was the damage to the wing by the foam, the management structure and practices of NASA were ultimately to blame. An obsession with reaching critical milestones and a failure to communication between different departments contributed to the loss of the Columbia. Shuttle managers lost their jobs or were reassigned. The other three functional shuttles of the U.S. fleet were grounded.
       One of the universal tendencies of human beings is to look back on the past events and ask “Could something have been done differently to lead to a better outcome?” The Columbia disaster was no exception. In the CAIB report, the question was raised about what might have been done differently that could have prevented the disaster. A section of the report with the title “STS-107 In-Flight Options Assessment” deals with what might have been done.
       A second shuttle was being prepared for a mission as the Columbia was launched. Two weeks of additional work on the Atlantis space shuttle were required before it would be ready to fly. If the damage to the wing of the Columbia had been assessed as a threat to the survival of reentry shortly after the launch, the Atlantis might have been prepared for launch in time to rescue the crew of the Columbia.
       One limiting factor in the time available to rescue the Columbia crew involved the atmosphere of the craft. The carbon dioxide exhaled by the crew had to be scrubbed from the air. Lithium hydroxide capsules are used to absorb carbon dioxide in the craft. The Columbia had sixty nine LIOH capsule onboard. It was estimated that with periods of inactivity and some discomfort, the capsule use might be stretched to thirty days. There was sufficient oxygen to exceed the thirty day carbon dioxide limit if power use in the Columbia was reduces. Food, fuel and propellant could all be conserved and last past the thirty day carbon dioxide deadline.
        On the ground, a grueling twenty four hour seven days a week schedule would have had to be implemented to carry out accelerated preparation to launch the Atlantis. Everything would have to be done much more quickly than usual and there would be no time to redo anything. Shuttles can carry from five to seven crew but the return flight would have to carry the seven members of the Columbia crew. At least four crew members would be required for the rescue mission. Two to fly the shuttle and two to carry out the Extra Vehicular Activity necessary to move the crew of the Columbia to the Atlantis. Two weeks of intensive training would be necessary for the two veteran astronauts selected for the EVA.
Please read Part Two.
Crew of the Columbia:

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        In a recent blog post, I talked about some of the lunar missions that the Chinese have planned. There have been recent reports that the Russians also have some plans for lunar missions.
        The Russian space agency, RosCosmos, has been planning for a lunar base for years and is now providing some details of those plans. Initially, the plans call for at least two people to staff the base with the total permanent staff rising to twelve people. The current plan is to build a base near one of the poles of the Moon and to bury a power plant beneath the base. There will also be a buried shelter underground near the base. This shelter will provide protection from dangerous radiation from solar storms. The Russian base will be used for scientific research. There could also be mining operations to extract useful minerals from the lunar regolith.  
        The Russians have said that the underground shelter could also be used for protection against nuclear attacks. This suggests that there may also be military uses of the base. Radar arrays at the base could be used to keep track of satellites in Earth orbit and launches of missiles from bases on Earth. Missiles on the Moon could be launched against targets on Earth. If other countries have bases on the Moon, which is likely, nuclear missiles at the Russian base could be used against targets on the Moon. This is at odds with the international treaties that call for signatories to agree not to put weapons on the Moon.
      The Russian timetable calls for launching a lunar probe in 2024 to survey possible locations for the base. Humans would arrive at the Moon to establish the base in 2030 although there may be manned flights in 2029. TASS reports that engineers are already working on the Luna 25 lander that will be used for exploration related to the base. The Angara-A5V heavy-lift launch vehicle is being developed to ferry equipment to the Moon for the planned Moon base. It is expected to take at least six Angara-A5V missions to supply the parts for the base. Each mission will carry a separate module for the base and the modules will be integrated onsite. Planners expect that it will take ten years to fully construct the base.
      A Russian company called Energia announced plans for an eleven and one half ton reusable spacecraft that will be used to carry cargo and cosmonauts to the Moon in only five days. The craft is called the Ryvok. The plan is to send the Ryvok to the International Space Station with Soyuz ships and Angara Rockets. The Ryvok will be assembled at the ISS and fuel for the lunar missions will be delivered separately to the ISS.
      Russia had plans to send cosmonauts to the Moon in the 1960s but they were never carried out. Russia has sent unmanned probes to the Moon but no humans. Now Russia says that it wants to focus on manned exploration and a permanent manned base on the Moon. The European Space Agency has expressed interest in joining the Russia lunar exploration program. NASA has been considering manned missions to the Moon and the Russian ambitions might accelerate a U.S. return to the Moon.
Mockups of Angara A5V rockets:

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        With the discovery of thousands of planets orbiting other stars, the question of life elsewhere in the universe is a topic of popular debate. A great deal of attention has been given to the exact astronomical and geological conditions necessary for Earth type life to arise on another planet. The planet must be in what is called the “habitable” zone around its parent star. This is the zone where water is liquid. Too far out and water freezes. Too close in and water turns to steam. The planet has to be solid like the Earth and have an atmosphere. It can’t be too much bigger or smaller than the Earth. It will need magnetic fields to shield it from radiation and the star it orbits needs to be old enough for life to evolve and stable enough not to send out massive solar flares that could destroy life. Some say that it would need a large moon as well. In any case, it is estimated that there are millions if not billions of planets in our galaxy alone the could host complex life.
       The discovery of life on another planet around another star will be difficult but there are some possible clues like the composition of atmospheres. It would be a huge scientific achievement to find evidence of extraterrestrial life. But aside from the gain in scientific knowledge, there are other questions to be explored. What will be the impact of such discoveries on politics, economics, and society in general? One very interesting question is what  impact the discovery of complex life on another planet around another star would have on religions. Religion is a very important and powerful institution which affects the lives of many people.
        NASA has awarded a grant of over a million dollars to the Center for Theological Inquiry to explore the societal implications of the discovery of complex extraterrestrial life including its impact on religion. CTI is an “independent academic institution for interdisciplinary research on global concerns with an international visiting scholar program in Princeton, NJ.”
       The CTI will assemble a team of scholars with credentials in theology, the humanities and the social sciences. These scholars will “conduct an interdisciplinary inquiry on the societal implications of astrobiology, the study of the origins, evolution, distribution, and future of life in the universe.” The inquiry started in 2015 and will run to 2017. 
       The John Templeton Foundation is also a supporter of the CTI research project. The TF is “is a philanthropic organization that funds inter-disciplinary research about human purpose and ultimate reality.” The Foundation often gives grants to researchers seeking to create a bridge between science and religion.
        Critics of the CTI research project say that it is a waste of taxpayer’s money to fund research into how the discovery of extraterrestrial could affect religion on Earth. However, such discoveries could have a profound impact on Earthly religions which shape the lives of billions of people. Whatever your attitude toward religion, it is important to explore what impact religious debates could have on politics and society on Earth in the future.

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        There are only a few nations with serious space launch capability. A few other nations are working on building their own infrastructure to launch space missions. All the other countries have to rely on purchasing launch services from countries which do have their own space programs. Recently a couple of small countries that have no serious space programs have announced serious ambitions to enter the exploration and exploitation of space.
        The United Arab Eremites is a small country in the Middle East on the east coast of the Arabian Peninsula just north of Oman.  It has a population of about ten million with one and a half million Emerati citizens and eight and a half million expatriates. Its oil reserves are the seventh largest in the world making it a rich country. It is one of the top ten countries with the highest GDP per capita incomes in the world. The most populated city in the UAE is Dubai which has become a global city and an international aviation hub. The UAE is no stranger to ambitious expensive projects. It is building the world’s tallest skyscraper in Dubai and has also announced plans for a brand new climate controlled city.
       The UAE has just announced that it intends to develop its own space program and send an unmanned probe to Mars by 2021. The UAE has already invested about six billion dollars in space technology. While it is generally accepted that the UAE has the drive and money to create an indigenous space program, some skeptics say that it will be difficult for the UAE to meet the 2021 deadline for its Mars probe. Only half of the Mars missions in the past have been successful.
        Luxembourg is a small country in western Europe. It is bordered by Belgium Germany and France. Its capital, Luxembourg City is one of the three official capitals of the European Union. It is less than a thousand square miles and has a populate near six hundred thousand. It is a highly developed country with an advanced economy and the highest GDP per capita in the world. Financial and banking services account for a large part of its economy.
        In the 1980s, Luxembourg invested in an ownership position for a startup satellite company that became an international provider of satellites named SES S.A. SES S.A. owns a fleet of over fifty commercial communication satellites. These satellites provide broadcast television and radio channels as well as satellite communication services to businesses and government agencies around the globe.
         Luxembourg has recently announced that it is setting aside over two hundred million dollars to support space projects such as asteroid mining. The government is also considering investing in research and development to send commercial spacecraft beyond Earth orbit. Luxembourg wants to establish the legal and regulatory framework that will convince investors to invest in such enterprises in Luxembourg. Two start-up space industry companies have already announced that they are setting up shop in Luxembourg.
        It will be interesting to see what these two small but rich countries will be able to accomplish in the global space industry in the coming decades.

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        I have blogged extensively about the Indian space program. They are far behind the U.S., Europe, Russia and China but they are making respectable progress. Recently they carried out a test launch of their space shuttle.
         On Monday of May 23rd, 2016, the Indian Space Research Organization successfully launched what they refer to as a Reusable Launch Vehicle Technology Demonstrator or space shuttle in common terms from the Satish Dhawan space center pad at Sriharikota on the southeast coast of India. An Indian HS9 booster rocket carried the RLV-TD aloft. The fourteen million dollar un-manned one sixth scale model rose to a peak altitude of forty miles and then made a controlled descent at Mach 5 into the Bay of Bengal after a thirteen minute flight. During the descent, it was exposed to temperatures of two thousand degrees Centigrade. The RLV-TD was brought down in the sea about two hundred and eighty miles from Sriharikota because the ISRO does not have a landing strip that is long enough to handle the RLV-TD.
         A spokesman for the ISRO said that they had been working on the project for ten years and that the last five years were spent on design and development of the actual vehicle itself. A statement from the ISRO said that “In this flight, critical technologies such as autonomous navigation, guidance and control, reusable thermal protection system and re-entry mission management have been successfully validated.”
         Before an Indian RLV can actually be launched into space, it will need to have a body of better and stronger material to withstand the rigors of launch and reentry. When the working model of the RLV-TD has been developed, it will be used to put satellites in orbit and to take astronauts into space. The ISRO wants to install a scram jet in the working model of the RVL-TD which would increase its range and allow it to maneuver in space. The ISRO does not expect to have an operational RLV-TD before 2030. The next step in the project is to analyze the data that was gathered during the mission. ISRO hopes to be able to launch the RLV-TD again soon to gather more data.
         The Indian shuttle is being developed to make space missions cheaper and easier. Although other countries such as the U.S. have given up on the use of winged space shuttle, India hopes that the shuttle it is developing will bring down the cost of space flight as much as ninety percent for India. India wants a piece of the multi-billion dollar satellite launch industry and the RLV would be a big step in the development of the India space industry.
         The Space Review, an online journal from Washington, D.C. cast doubt on the importance of the test launch. They said that the launch of the RLV-TD was “blown out of proportion.” The Indian aviation expert who wrote the article pointed out that the ISRO itself said that the mission was just a demonstration and a “baby step” on the road to a reusable space shuttle. He blamed the Indian media for hyping the test launch as a major advancement for the Indian space industry. The writer called into question the economics of space shuttle development for India considering the huge cost of space shuttle development in other nations.
Launch of the RLV-TD:

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        I have been a fan of science fiction since I was about six years old. I have been reading books and comics, watching TV shows and movies, and thinking about space travel for decades. There are a lot of technical details about how to design, build and launch spacecraft. Then there is all the complex mathematics of orbits to worry about. After those problems are solved, we have to worry about the effects of zero gravity on the human body. Apparently there are some very serious problems with how a human body deals conditions in space.
       It has been know for a long time that there are dangers from radiation in space. Energetic particles from solar storms can cause tissue damage. Some of this can be ameliorated by proper shielding but especially powerful solar storms might be too much for conventional shields. It might be possible to create some sort of immaterial shield from power magnetic fields in the future to protect astronauts.      
       There is a major problem has to do with the loss of bone density. Our bones are primarily composed of a matrix of collagen with embedded crystals of calcium phosphate. Calcium phosphate is piezoelectric. This means that when mechanical pressure is applied to the crystal, it generates an electrical field. Inside bone, the constant effect of gravitation generates electrical fields which cause a replenishment of bones maintaining density. When gravity is removed, that replenishment is diminished and bones become less dense and more brittle. The longer a human being stays in a low or zero gravity environment, the more their bone density falls.
        One possible solution to this problem is to create artificial gravity on spacecraft by have a section of the craft rotate. If the rotating section is too small, it will  generate deleterious effects on the inner ear because of the different in the coriolis effect from spinning between the head and the feet. It is estimated that a spinning section would have to be at least two hundred yards across in order to prevent negative coriolis effects.
       Another possible solution would be to find a way to restore the electrical fields that are missing because of the lack of gravity. It should be possible to design some sort of body stocking that generates localized electrical fields to influence bone deposition. We would have to learn a lot more about exactly how these fields are generated in bones as a result of gravity in order to make this work.
      Just recently, another health problem was discovered from long term zero gravity in Earth orbit. The livers of mice in orbit for only two weeks show symptoms consistent with nonalcoholic fatty liver disease. There is also some indication of fibrosis or scarring of liver tissue. This damage showed up in a much shorter period of time than such damage takes on Earth. It is not clearly understood exactly how the liver is being damaged but the effect is clear. This will have to be solved before humans are able to withstand zero gravity for years at a time. It may be possible to create drugs that treat the damage but that will take more research.
       Other problems of long periods at zero gravity include loss of muscle mass and vision problems. Ultimately, it may be necessary to engineer modification in the human genome in order to deal with gravity and radiation problems. Alternatively, some sort nanotechnological implants might be developed.

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        Last week, I blogged about the Chinese ambition to mine the Moon for helium-3 to fuel fusion reactors. This week, I am going to assess the practicality of that intention.
       Helium-3 is stable isotope of helium which contains two protons and a neutron in the nucleus. He-3 can fuse with deuterium but it requires higher temperatures than deuterium-tritium fusion. This reaction does not produce as many neutrons as D-T fusion but neutrons are still produced. He-3-He-3 fusion produces no neutrons which makes it desirable but requires even higher temperatures making it more difficult to utilize.
       There is virtually no He-3 on Earth. However, after billions of years of bombardment of the lunar surface by the solar winds, the upper layers of regolith on the lunar surface are saturated with He-3. There is estimated to be a million metric tons of He-3 on the lunar surface down to a depth of a few yards. It has a concentration of about ten parts per billion in sunlit areas and about fifty parts per billion in areas that are permanently in the shade.
        Forty seven tons of He-3 which would fit into the cargo bays of two space shuttles could power China for a year if burned in fusion reactors. A member of the Chinese Academy of Sciences has said that three shuttle missions to the Moon could bring back enough He-3 to supply the energy needs of the whole world. This might be overly optimistic considering that it would take two shuttle to bring back enough for China which represents only a third of the electricity consumed in the world. A Russian space company has also said that He-3 for fusion fuel would be a commercially viable export for lunar operations.
        Given the very low concentration of He-3 in the regolith, a huge amount of lunar regolith would have to be processed to yield useful quantities of He-3. One hundred and fifty million tons of lunar regolith would have to be mined and processed to acquire one ton of He-3. So in order to obtain the forty seven tons of He-3 mentioned above, it would be necessary to deal with about seven billion tons of lunar regolith. This would be a huge undertaking and would have to be repeated every year to supply all of China’s energy needs. This seems like a hard way to get electricity.
       The lunar regolith also contains a lot of oxygen. Iron, aluminum and magnesium are also present in significant quantities. Perhaps He-3 production could be part of a larger and more comprehensive mining operation to obtain multiple useful elements from the lunar regolith.
        Considering space resources beyond the Moon, there is plenty of He-3 in the atmosphere of the gas giants in the solar system. Jupiter is the closest of the gas giants but it is also the most massive. Its intense gravity and electromagnetic fields would make mining He-3 very difficult. The other gas giants such as Saturn would be easier to mine but they are much further away.

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        I have blogged before about the plans that China has for lunar exploration. China is carrying out a whole series of missions to the Moon scheduled out to 2020. This is  by far the most ambitious lunar exploration effort being executed  by any major national space program.
       Phase I of the Chinese lunar exploration program consisted of two orbital missions. In 2007, China launched the Chang’e 1 which flew to the Moon and scanned the entire lunar surface for a high definition 3-D map to be used for future missions. It also mapped the location and abundance of a variety of chemicals. In 2010, the Chang’e 2 was sent to the Moon to scan the lunar surface in greater detail.
        Phase II of the Chinese lunar exploration program was Chang’e 3 which consisted of a lunar rover called the Jade Rabbit that was landed successfully on the Moon to explore about a square mile of the lunar surface. It also carried out a 3 month mission of astronomical and Earth observations. The Chang’e 4 mission was a backup for Chang’e 3 but was used for testing after the success of Chang’e 3.
        Phase III of the Chinese lunar exploration program began with Chang’e 5-T1 to test a lunar return landing. It was launched in 2014. In 2017, the Chang’e 5 will be launched to send a lander to the Moon which will collect up to four pounds of samples and return them to Earth. Chang’e 6 will be launched in 2020.
       China also has a very ambitious energy development program. They are building dozens of nuclear fission reactors and planning to build dozens more in the next ten years. They are also research fusion power reactors. There is a light isotope of helium which has great potential as a fuel for fusion reactors. Helium-3 is stable isotope of helium which contains two protons and a neutron in the nucleus. There is virtually no helium-3 on Earth. However, after billions of years of bombardment of the lunar surface by the solar winds, the upper layers of dust on the lunar surface are saturated with helium-3. There is estimated to be a million metric tons of helium-3 on the lunar surface down to a depth of a few yards. Forty seven tons of helium-3 which would fit into the cargo bays of two space shuttles could power China for a year if burned in fusion reactors. China would like to establish a permanent manned base on the Moon for mining helium-3. This could provide cheap pollution free power for China which is in desperate need of better energy sources.
        In addition to using the Moon for a source of fusion fuel, China could also use the Moon as a military base from which to launch missiles against any target on Earth. When China launched the Jade Rabbit, its first lunar rover in 2013, there were reports of articles in the Chinese press that China could make the Moon into a “death star.” China has been increasingly aggressive and belligerent in the last few years and recently published a map of U.S. cities that could be targeted for nuclear strikes by Chinese submarines. The idea of militarizing the Moon goes against major international space treaties including the U.N. Outer Space Treaty and the U.N. Preservation of Space Treaty.
       Hopefully, China will concentrate on peaceful uses of space resources and reject the militarization of the Moon in the coming decade.
Chinese National Space Administration Logo:

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         Last week I blogged about a planned space mission that would launch a thousand tiny satellites the size of cell phones towards another star propelled by giant lasers. This week, I am going to talk about a proposed satellite launch project that would send even smaller satellites into space.
         Mason Peck is an engineer at Cornell University. He just received a seventy five thousand dollar grant from NASA’s Institute for Advanced Concepts to study his new magnetic propulsion system which he has been working on since 2005. His satellites are about the size of a dime and very inexpensive. They are integrated circuits that contain everything needed for space missions. Each one centimeter square Sprite contains a battery, a plasma contact capacitor, power conditioning and switching circuitry, a “science lab on a Sprite”, a radio, a high efficiency solar cell array and thrusters. In 2011, several prototype Sprites were sent to the International Space Station to test the ability of the Sprites to withstand conditions in space.
          Instead of requiring fuel to escape Earth orbit and explore the solar system, Mason’s satellites, called Sprites, would use the Lorentz force which acts on charged particles moving in a magnetic field to propel them to other planets.
         The idea of very tiny satellites has been around for twenty years. It evolved from the idea of “smart dust” which is a name for tiny micoelectromechanical sensors that could be distributed into the environment to measure light, temperature, movement, chemicals and biological substances. Eventually it was realized that these tiny sensors could be incorporated into satellites and sent into space. Research on such tiny satellites has been carried out by  Surrey Space Centre, the University of Strathclyde, the Aerospace Corp., and the Jet Propulsion Laboratory.
         Millions of these satellites could be launched into space and form vast sensor networks across millions of miles. Each satellite could provide a simple measurement. Taken together, the aggregate measurements of such satellites could reveal important information about conditions in space.
          Mason hopes to send his Sprites to Europa, a moon of Jupiter, by 2030. Thousands of Sprites would be packed into the nose of a rocket and then launched into Earth orbit. Each Sprite trails a long wire attached to a capacitor. A solar panel on the Sprite would send electrons to the capacitor and they would flow through the attached wire. The Lorentz force would exert a force on the charged Sprite causing it to gain altitude. After a year, the Lorentz force would have pushed the Sprite free of the Earth’s gravitation. With the correct timing, the Sprites would then fly away from Earth on a trajectory that would take them to Europa. Following a journey of several years, tiny thrusters on the Sprites could adjust their flight to insure that most of them reach Europa. Because they are so small, they would not burn up as they descend through the European atmosphere. The atmosphere would be sampled by the Sprites for molecules that indicate the existence of life. Any Sprite that detected organic molecules would send a simple one bit message back to Earth.
Early artist’s concept of a Sprite satellite:

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James Provost