Part 1 of 2 Parts
     Last week I posted an essay about a new system developed by Tethers Unlimited to deorbit small satellites by unreeling a strip of electroconductive tape at the end of a satellite’s life. This system is under development to help remove small dead satellites in a matter of weeks rather than the many months that are now required. There are tens of thousand pieces of debris from launches and dead satellites now being tracked in Earth orbit. There are over a million pieces too small for radar to spot also in Earth orbit. If this debris keeps piling up, it may become impossible to launch payloads into orbit or beyond. It is critical that we find a way to clean up this orbital debris if we want to continue to explore and exploit space.
     The Gateway Earth Development Group is a collection of academics associated with universities around the world. They are working on plans for a space station called Gateway Earth that would have facilities to recycle old satellites and other space junk. They hope to be able to have such a station operational by 2050.
     There are two main orbits in use around the Earth. The Low Earth Orbit or LEO extends from about one hundred and twenty-five miles above the Earth to about six hundred and twenty miles. The International Space Station obits the Earth every ninety minutes in LEO. There are thousands of satellites in LEO.
     LEO is very crowded and there is a danger of collisions which could result in a shower of debris that could trigger a cascade of showers as further collisions occurred. Technology is being developed to reduce debris and old satellites in LEO.
     Geostationary Earth Orbit or GEO is about twenty-three thousand miles above the Earth. At this altitude, satellites will remain in position over one spot on the Earth as the Earth rotates. This orbit is an excellent place for weather and communication satellites.
     When a satellite in GEO reached the end of its operational lifetime, the operators try to move it to a higher orbit two hundred to two hundred and fifty miles above the protected zone where GEO satellites operate. About eighty percent of dead GEO satellites actual make it up to the higher orbit. It is the twenty percent that remain in the protected zone that are a major problem that requires a solution. A recycling space station could be that solution.
     The higher orbit is like an abandoned junkyard. Flashes of light are sometimes seen in this orbit which are likely collisions between dead satellites where unused fuel or old batteries explode. There is a danger that dead satellites and collision debris could fall back into the protected zone and threaten operational satellites.
     Unfortunately, international space law is not helpful with respect to dealing with dead satellites in GEO and in the graveyard orbit. Dead or out of control satellites cannot be touched without permission of the owners even if those satellites threaten expensive functional satellites.

       I have blogged before about all the debris orbiting the Earth left over from space launches. It is estimated that there are more than one hundred million pieces of debris that are less than 1 centimeter in size. They are too small to track with radar but are big enough to cause serious damage to a space craft because they are traveling so fast. The United States Strategic Command tracks about eighteen thousand pieces of debris that are bigger than four inches. If fact, if the debris keeps piling up, it may become impossible to safely launch a payload into Earth orbit or beyond. A variety of systems have been proposed for removing debris from orbit.
       Tethers Unlimited is located in Bothell, WA. In collaboration with TriSept Corp., Millennium Space Systems and Rocket Lab, they are going to test a new system to remove satellites from orbit which are no longer operational. The system is called Terminator Tape. It involves incorporating a module into a satellite which can unwind a strip of electrically conductive tape when the satellite is no longer in use.
        TU explained the system in an online post that said, “This tape will significantly increase the aerodynamic cross-section of the satellite, enhancing the drag it experiences due to neutral particles. In addition, the motion of this tape across the Earth’s magnetic field will induce a voltage along the tape. This voltage will drive a current to flow up the tape, with electrons collected from the conducting ionospheric plasma at the top of the tape and ions collected at the bottom. This current will induce a ‘passive electrodynamic’ drag force on the tape.”
       It is believed that the increased drag on the satellite from the tape will significantly cut down the time that it takes to drag the satellite down to burn up in the atmosphere. TU has already sent its Terminator Tape module into Earth orbit in several small satellites. However, the Dragracer satellite mission due for launch next year should be the best test for the Tape. There will be a control experiment included in the test.
       Millennium Space Systems is a Boeing subsidiary located in California. It will construct and operate the fifty-five pound Raptor-class satellite for the Tape test. TriSept is a company located in Virginia. They will handle launch integration and mission management services for the test. And, finally, Rocket Lab will include Dragracer in a ride share on its Electron rocket that will be launched from New Zealand in early 2020.
       When the satellite reaches orbit, it will divide into two payloads. One of them will initiate the deployment of the Tape and the other will experience just atmospheric drag without the Tape. Mission managers estimate that it will take two to four weeks for the payload with the Tape deployed to deorbit while the other payload will take from eight to twelve months to descend from orbit.
      Mike Scardera is vice president of advanced concepts for Millennium Space Systems. He said, “The Dragracer mission is all about providing an affordable, effective and scalable solution to the orbital debris challenge facing the LEO small-satellite market and the global space. It is the first in a series of critical project missions we expect to launch with TriSept.”
       The president and CEO of TriSept, Rob Spicer, said that the Dragracer test will demonstrate a new creative solution to the problem of dead small satellites that are piling up in orbit. Hopefully, some of the small satellites that will be launched in the future will include the Tape deorbiting system developed by Tethers Unlimited.

        One of the more fantastic ideas for getting into space is the space elevator. The basic idea is that a super strong cable reaches from the Earth’s surface to a huge counterweight that is beyond the twenty-three thousand miles geosynchronous orbit. Vehicles like elevator cars would climb up and down the cable lowering the cost of sending things to and from orbit by several orders of magnitude.
       The idea was first proposed in 1895 by Russian scientist Konstantin Tsiolkovsky. An old comic published in the U.S. in the 1950s depicted a man in a space suit climbing a ladder into space. American engineer Jerome Pearson published the first technical description of a space elevator in 1975. The concept of a space elevator came to popular media with two novels, both published in 1979. These novels were The Fountains of Paradise by Arthur C. Clark and The Web Between the Worlds by Charles Sheffield. Since then there have many mentions of space elevators in popular novels, comics, movies and television shows.
       The main technical problems with constructing a space elevator are buckling, dynamic stability and strength. Engineers believe that a satellite in geosynchronous attached to the cable could solve the problems of buckling and dynamic stability. The unresolved problem with strength lies finding a material that has the incredible strength necessary to withstand the enormous strain that such a construct would endure. After a hundred and twenty-five years, it now appears that such a material may be available.
       The cable for the space elevator would have to have a tensile strength of seven gigapascals. One pascal is defined as about one newton per square meter. One newton is defined as the amount of force necessary to accelerate one kilogram of material at the rate of one meter per second squared. Peason suggested that perfect crystals of graphite might have the strength necessary.
       Chinese scientists at Tsinghua University have announced the development and patent of a carbon nanotube fiber with a tensile strength of eighty gigapascals. This is over ten times stronger than theoretical studies say is needed to build a space elevator. Part of their research has been published in the journal Nature Nanotechnology. The Chinese scientists said, “in great demand in many high-end fields such as sports equipment, ballistic armor, aeronautics, astronautics and even space elevators”.
      Nicola Pugno is a professor of solid and structural mechanics at the University of Trento in Italy. He thinks that the new fiber developed by the Chinese scientists is promising. He said, “Having a strong mega-cable and maintaining its strength and flaw tolerance is the biggest challenge. The Nature Nano report [from the Tsinghua team] is a key step towards the solution … thus, never say never.”
       One concern that I have about the creation of a space elevator is that it would be very vulnerable. If the base was destroyed, the counterweight would yank the cable into space. This would wreak havoc with the satellite to which the cable was attached. A missile or a bomb in one of the elevator cars could break the cable above the surface of the Earth. Any length of cable that was below the cut would fall back to Earth, wrapping itself around the equator causing devastation and tsunamis. If the break was above the satellite in geosynchronous orbit, the satellite would be yanked down to Earth. There would be enough cable to wrap almost all the way around the Earth. As useful as a space elevator might be, I am afraid that it would be much too dangerous to ever be constructed.

Part 3 of 3 Parts
      One big stumbling block for the Interstellar Probe project is the fact that best heat shield ever used by a NASA probe is only able to protect a probe that comes within four million miles of the Sun. The Interstellar Probe would have to come within two million miles of the Sun in order to make best use of the gravity boost.
       Nicky Fox is the director of NASA’s heliophysics division. She says, “There is a moment for every big mission, almost an ‘aha’ moment, when the technology is ready and you’ve got a plan and it makes sense and is going to answer the science questions.” The heat shield problem is standing in the way of satisfaction with the Interstellar Probe plan.
       There is another big question that looms with respect to the Interstellar Probe mission that goes beyond technology and politics. By 2050 deadline projected for the Interstellar Probe to reach its objective, the United Nations’ Intergovernmental Panel on Climate Change estimates that the global average temperature will be two degrees Celsius above the average temperature in pre-industrial times. Unless the world embarks on a “moon-shot” to curb carbon emissions, in 2050 many of the world’s major cities will be under several feet of water due to sea level rise or they will be experiencing temperatures that will make them uninhabitable. Unfortunately, major countries have not done enough to curb their carbon emissions.
      Mandt believes that the Interstellar Probe mission might be helpful in inspiring the U.S. and the world to also seriously consider putting major resources into a multigenerational project such as mitigating climate change. She said, “This would be an example of a large group of people working together on something multigenerational. Which is the same thing we need with climate change.”
        She has pointed out that members of the team working on the Interstellar Probe mission range from recent graduates from graduate school programs to people who are on the verge of retirement. At least eight different countries have contributed members of the team. The team includes engineers, astronomers, planetary scientists and a particle physicist.
       Last year, Mandt invited Janet Vertesi of Princeton to advise them on best organizational principles. Vertesi has carried out ethnographic studies of possible teams for astronauts who will share a spacecraft. This is the first known incident where a sociologist has been involved in the development of a NASA space mission.
      Vertesi said that her job for the Interstellar Probe project was to remind them of the human side of such missions. How will the team handle conflicts? Where should the data be stored? How does the team recruit diverse members to properly represent the nations who will launch the probe? She said. “We’re testing out this notion that you can actually plan a mission up front to achieve certain social objectives, too.”
       Vertesi says that it is good feeling to be involved in such an inherently long-term optimistic project given all the problems that bedevil the world today. Scientists will dedicate their careers to a project that will outlive them. She adds, these people just can’t wait for the future to come.”

Part 2 of 3 Parts
       In order to achieve the maximum velocity possible to travel beyond the Solar System, a really powerful rocket will be required. NASA hopes to have its powerful Space Launch System ready by 2021. It is capable of twice the thrust of the most power current launch system. The SLS would launch from Earth at about nine miles a second. It would loop around Jupiter and then plunge back into the Solar System to get a gravity boost from the Sun. Skimming through the outer atmosphere of the Sun, it would fire a second rocket which would boost its speed to around sixty miles a second. At this speed, it should reach the heliopause in about ten years.
       The team working on the McNutt plan hopes that they will be able to route the probe past Uranus, Neptune or a body in Kuiper Belt know as Quaoar. Kathy Mandt is a planetary scientist who hopes that good use can be made of the time the Interstellar Probe spends in the Solar System. It might also be useful for improving the search for exoplanets. This could be accomplished by looking back at planets in the Solar System with the same equipment that is currently being used to look for exoplanets. When the probe crosses the heliopause, it can take samples of dust and particles which will aid in understanding the heliosphere and the materials that formed our Solar System.
       Once beyond the protective bubble of the heliosphere, it will be able to investigate phenomena that are obscured by the heliosphere such as cosmic rays from exploding stars, light from the afterglow of the big bang, disks of debris that are forming planets around young stars and other interstellar objects and processes.
        So far, the McNutt Interstellar Probe only exists as a PowerPoint Presentation. His team has received funding of around seven hundred thousand dollars from NASA for concept studies. Currently they are waiting to find out whether NASA will provide an additional six and a half million dollars over the next three years. This would permit them to draft a more detailed plan for scientific studies and a mission design document.
      The critical moment for the Interstellar Probe project will arrive in 2023. The National Academies of Sciences, Engineering and Medicine will publish their next decadal survey for solar and space physics. These assessments are conducted every ten years under request from Congress and NASA. They are considered to be the official consensus for U.S. space science goals. They will guide NASA budgeting for the next ten years.
       Richard Mewaldt is a Caltech physicist who served as chair for the solar and heliospheric physics panel during the most recent decadal survey which was published in 2013.  He said, with respect to the Interstellar Probe, “It was always something we couldn’t do immediately, but set aside maybe for the future.” In the 2013 decadal document, advanced planning for an interstellar probe was ranked as the eighth among nine imperatives for NASA.
       NASA has a heliophysics division which would be responsible for overseeing any interstellar missions. It receives less funding than any other NASA science division. It might help launch the Interstellar Probe mission if they could interest the planetary sciences division at NASA in flyby missions to the outer planets and/or the Kuiper Belt object. Unfortunately, the different NASA divisions are kept well separated and it is difficult to obtain funds from multiple NASA division for a single mission.
Please read Part 3 next

Part 1 of 3 Parts
       For the most part, I have blogged about space around the Earth. Occasionally I have ventured out into the Solar System. Very rarely, I have written about missions beyond our Solar System. Today I am going to blog about a such a mission.
        Ralph McNutt works at the Johns Hopkins University of Applied Physics Laboratory. Now sixty-five, he has been interested in interstellar travel since he was a teenager. He is currently drafting a plan that would send a probe ninety-three billion miles into interstellar space. This is about one thousand times the distance between the Sun and the Earth which is referred to as one astronomical unit. The probe would explore the conditions beyond the Solar System. The probe would take about fifty years to reach its destination. It is likely that everyone involved in launching the probe will be dead by the time it achieved its objective.
      McNutt and his team hope to be chosen when U.S. space scientists release a list of their top research priorities. In order to get their mission on the agenda, they must convince their colleagues that the goal of the mission is scientifically valuable. Of course, it will have to be politically viable in its competitions with many research worthy topics on the Earth and in the Solar System.
       Our Sun is in a minor arm of the Milky Way galaxy. The Milky way is about one hundred thousand light years across. The Earth is about twenty-five thousand light years from the center of the Milky Way which, about half the way to the rim. The Earth is currently traveling about half a million miles per hour. It is hit by gusts of gas and dust and pounded by highly energetic particles whose origins are unknown. The surface of the Earth is shielded from this rain of gas, dust and particles by what is called the “heliosphere.” This is a stream of charged particles called the solar wind which streams out past all the planets to the very edge of the Solar System. Out beyond the Solar System, there is a region known as the “heliopause.” This is the buffer zone between the solar wind and the ocean of dust and gas in interstellar space. It is the boundary between our Solar System and the interstellar environment.
       Only two Earth probes have ever reached the heliopause while still functioning. The two probes were referred to as Voyagers. They were launched in 1977 and it took over thirty-five years for them to reach the boundary. Other probes have traveled out of the Solar System, but they had stopped functioning by the time they reached the heliopause. Some of the instruments on the Voyager probes have failed and their radio transmissions have become fainter and fainter.
       Voyager 1, the most distant object ever built by humanity is now one hundred and forty-five astronomical units. At the rate that it is traveling, it will take two hundred and eighty-three years to make it to the region targeted by McNutt.
Please read Part 2 next

  NASA has just announced that it is sending a lander to Titan, a moon of Saturn. The lander will carry a robot helicopter to explore Titan. The mission is called Dragonfly. It is part of NASA’s New Frontiers program which is dedicated to high-priority solar system science projects. Current New Frontiers missions include Juno which is a mission to Jupiter, New Horizons which is currently flying through the Kuiper Belt and OSIRIS-Rex which is orbiting the small asteroid named Bennu.
       Dragonfly includes a quadcopter. It has four pairs of coaxial propellers which are each mounted to the corners of the thirty feet long lander. The plan is for it to land and then make a series of five-mile hops so it can carry out experiments at different locations. It will take pictures and samples of the air and surface materials to examine their chemical composition. It will also take meteorological and seismological measurements at each location. The main goal of the mission is to determine whether there are organic molecules on Titan that could be the basis of some kind of life.
       Saturn is over eighty-six billion miles from Earth. Titan is so cold that if there is water on the surface, it will be as hard as granite on Earth. Titan has a atmosphere fifty percent thicker than Earth which is compose mostly of nitrogen. The Cassini spacecraft orbited Titan and took many images and readings. Some of the surface features captured by Cassini include dunes composed of hydrocarbon sand, cryovolcanoes and even evidence of an ocean of liquid water under the surface. Cassini also found huge lakes of liquid methane and ethane close to the north pole. Radar images of the landscape revealed hills and rivers that flow into the lakes. This suggests that methane on Titan behaves in a way that resembles water on Earth. It has a similar cycle composed of evaporation, movement as vapor in the atmosphere, rain and large pools of liquid on the ground. Although the temperature on Titan is around -290° Fahrenheit, the methane cycle and lots of organic molecules may be involved in complex prebiotic chemistry reactions.
       The Dragonfly mission is scheduled for a 2026 launch date assuming that the hardware for the mission will require about seven years to construct. Much of the instrumentation is based on known and tested designs. The power source will be a common radioisotope thermoelectric generator that uses plutonium to generate electricity. Solar power would not be useful because Titan only gets about one percent of the sunlight that falls on the Earth. The big question is whether or not the propellers will function correctly in the cold atmosphere. On the positive side, the gravity on Titan is only one seventh of the gravity on Earth and the atmosphere of Titan is much denser. This should make it easy to fly around on Titan. What winds there are on Titan are low velocity and should not present a problem. If Dragonfly is launched in 2026, it will not reach Titan until 2034.
       The Dragonfly mission as envisioned should last for at least two and a half years. Unfortunately, this will not be enough time for the quadcopter to hop from the landing site near the equator to the huge lakes at the pole.

        I have written about Tethers Unlimited before. They are a private space company located in Bothell, WA. Years ago, when they were founded, tethers were thought to hold great promise for a number of space applications. As time passed, that promise faded and so did the money available for research and development. When I saw a presentation by the head of TU last year, they were diversifying into providing satellite maneuvering thrusters using water for fuel and satellite radios that used software to set the frequency.
       NASA has just handed out forty-five million dollars to support three hundred and sixty-three aerospace projects that were proposed by small businesses and research institutions. Each project has been awarded up to a one hundred and twenty-five thousand dollar Phase 1 grants as part of NASA’s Small Business Innovation Research and Small Business Technology Transfer. TU was awarded grants for five space technology projects. TU has been granted NASA Phase 1 grants before for such things as in-space construction and 3D printing. Here are brief descriptions of the five new TU projects.
SPIDER: When I was listening to the TU CEO talking about current research projects, he described a machine that could move around on structures in orbit and use a spool of material to create new struts for the structure. I thought to myself that that sounded like a mechanical spider. Soon after that thought occurred to me, he said that they called the construction machine a “Spider”. At TU, SPIDER now stands for Sensing and Positioning in Deep Environments With Retrieval. This new device does not fit the description that I heard at the presentation last year. This new SPIDER is intended to position itself above a lunar crater and take samples while changing position. It was developed to overcome the contamination and stability problems that can occur when a lunar rover is exploring a crater. Phase 1 funding is to support development and design. If NASA funds Phase II, a prototype will be developed and tested.
ARTIE: ARTIE stands for Androgynous Robotic Tool-change Interface. It is intended to supply power and data interface to the connectors on robot arms used in space. Phase I will consist of demonstration of a proof of concept prototype. If NASA grants Phase II for ARTIE, a prototype will be sent into orbit for testing.
VORTEX: VORTEX stands for Venus or Titan Exploration. This is a gimballed pointing mechanism or artificial “wrist” that would be use for Venus and/or Titan explorations as well as satellite operations in other extreme environments. Phase I funds will be to support progress in the design of ARTIE.
HyperBus: The HyperBus Cargo Platform is a palletized system for the transport, emplacement and exchange of hardware at the International Space Station or other orbital platforms. If TU gets to Phase II on this project, funding will be used to develop the concept, construct a prototype and demonstrate the system in the TU laboratory.
RAMP TPS: RAMP TPS stands for Resin Additive Manufacturing Processed Thermal Protection System. Phase I funding will support development of an in-situ cured, additively manufactured, spacecraft heatshield material and process. This device will allow the lost-cost manufacture of heat shields in orbit for re-entry vehicles. TU and Western Washington University will collaborate on the creation of this technology.

       Twenty commercial space companies joined NASA representative at a conference last week to discuss the commercial possibilities of the International Space Station. NASA has been planning to use the ISS to support the commercialization of space for some time. Stephanie Schierholz, the lead spokesperson for NASA, said, “We’re here because the International Space Station is now open for business.”
       The NASA plan included allowing private astronauts to visit and stay on the ISS, brought to the station by U.S. launch vehicles. It also includes inviting private companies to carry out business activities on the ISS. These activities could include “in-space manufacturing, marketing activities, healthcare research and more.”
       NASA presented a five-part plan that it insisted would not conflict with the use of the ISS for government and public sector purposes. It will stimulate creative and varied revenue-generating opportunities for private companies. NASA wants to become just one of many users of the ISS and other low Earth orbit facilities. NASA says that this should benefit the U.S. taxpayers too.
Part 1: NASA has created an ISS Commercial Use Policy. This policy provides a menu of supplies and/or resources that will be available for purchase by private companies. Resources such as crew time, cargo launch and cargo return capabilities are just some of the resources that will be available.
Part 2: Private astronauts can book one or two short duration visits per year beginning in 2020. The missions will have to be privately funded, dedicated commercial space flights. These missions will have to use U.S. spacecraft which will include NASA certified space travel vehicles such as the SpaceX Crew Dragon. NASA will provide pricing for such resources as use of life support, supplies for the private astronauts, physical storage, computer usage and data storage.
Part 3: The forward section of the Harmony Node 2 of the ISS will be the first part of the ISS that will be a commercial destination. Other habitable commercial modules are planned for integration into the ISS in the future. NASA will issue a request for proposals on June 14th. And will select the first customer who will start developing the commercial facilities by the end of this year.
Part 4: NASA is working on a plan to stimulate long-term commercial demand. Space manufacturing and regenerative medicine are the first commercials uses for the ISS being considered. NASA has requested white papers by June 15th and proposals by June 28th.
Part 5: NASA has issued a new white paper that details the minimum needs for commercially viable long-term operations on the ISS.
       One of the most import parts of the NASA planning is to significantly reduce the cost of commercial transit to and from the ISS. NASA would also like to see private space companies develop and construct a private space station to eventually replace the ISS when it reaches the end of its operational life.
       There are about fifty private companies carrying out projects on the ISS right now. The new announcement is aimed at formalizing and scaling operations over the long term.

      In addition to this blog on the space industry, I also write a weekly blog on the nuclear issues at www.nucleotidings.com. Occasionally, I write posts that are relevant to both blogs such as today’s post on nuclear thermal propulsion.
      In a nuclear thermal propulsion system, a fission reactor is used to heat a propellant such as hydrogen which is then directed through a nozzle to provide thrust for a space craft. It is estimated that such a propulsion system could substantially reduce the duration of a deep space mission such as a trip to Mars. Early in the Space Age, NASA studied nuclear thermal propulsion only to abandon it in the early 1970s. Such research has only recently been resurrected.
     Vice President Mike Pence spoke March 26th at a National Space Council meeting in Huntsville, Alabama. He said, “As we continue to push farther into our solar system, we’ll need innovative new propulsion systems to get us there, including nuclear power. And the president and I know there’s no place on Earth better equipped to lead the world in pioneering these new propulsion technologies than Rocket City, U.S.A., a reference to a nickname for the NASA Marshall Space Flight Center in Huntsville, Alabama.
        Nuclear thermal propulsion also has support in Congress as well as in the private space industry. Jeff Thornburg is the chief executive and president of Interstellar Technologies, a private space company. He used to be a propulsion executive at SpaceX and Stratolaunch. At the May 22 Space Tech Expo in Pasadena California, he said, “Nuclear propulsion is key to exploiting our capabilities beyond low Earth orbit. There’s some key technology development that really needs to happen beyond the current state of the art.” He said that nuclear thermal propulsion integrated with electrical propulsion was the key to facilitating the expansion of nuclear thermal propulsion.
       Thornburg admitted that there were regulatory issues with nuclear thermal propulsion beyond purely technical challenges whether the nuclear thermal propulsion systems were developed and operated by government or private space industry. He also said that recent comments at the March meeting of the National Space Council by the Director of the Office of Science and Technology Policy about reviewing nuclear propulsion were encouraging.
       It is not clear exactly how nuclear thermal propulsion fits into the long-term exploration plans of NASA. Roadmaps for NASA exploration as well as many roadmaps developed by the private space industry rely on conventional propulsion systems such as chemical and solar electrical propulsion. While these system do not offer the same reduced travel times as nuclear thermal propulsion, they also do not present the same technical and regulatory challenges. None of the list of proposed NASA missions through 2028 specifically call for nuclear thermal propulsion.
      In 2019, the U.S. Congress provided one hundred million dollars for work on nuclear thermal propulsion. Seventy million dollars out of the hundred million dollars was earmarked for a flight demonstration of nuclear thermal propulsion in 2024.