28 February 2019
Nuclear In Space - The NETS Meeting
By James Conca


This is Mars, not Utah. Marsí surface looks so much like Earth, it seems likely that humans will set foot on it. Subsurface ice will provide water. But for humans to colonize this planet will require nuclear power. This photo by the Curiosity rover on September, 2015 shows a long ridge colored by the iron oxide mineral hematite. Just beyond is an undulating plain rich in clay minerals. Beyond that are a multitude of rounded buttes including Mount Sharp, all high in sulfate minerals.NASA/JPL-Caltech/MSSS

The NETS meeting is wrapping up today at the Pacific Northwest National Laboratory in Richland, Washington. The Nuclear And Emerging Technologies For Space is an annual gathering of people from NASA, National Laboratories, industry, and academia to discuss space nuclear power and propulsion as well as new and emerging technologies that make further space exploration possible, safe and economic.

For future space missions, especially for establishing colonies on the Moon or Mars, we need new energy systems to power larger facilities and spacecraft.

So far, NASA has done well with small nuclear systems that power our unmanned spacecraft to distant planets. On January 1st 2019, the nuclear powered New Horizonís spacecraft flew by the most distant object ever observed up close - Ultima Thule, far beyond Pluto, in the region called the Kuiper Belt, outside the Solar System proper. It will continue on into the Oort Cloud, the outermost region of the Solar System remaining from the original nebula from which the Sun and planets formed, before it exits our Solar System completely.

The New Horizons spacecraft flew by minor planets such as Charon (shown here) orbiting Pluto, and Ultima Thule (in the Kuiper Belt) on its path out of our Solar System. It would be impossible to get these images or approach any distant planet without nuclear power as the Sun is only another dim star in their skies. New Horizons is powered by Pu-238.NASA

The spacecraft could not have done so without nuclear energy. Solar energy does not work much beyond Mars and only in line-of-sight with the Sun. Chemical sources donít work for very long as their energy density is too low and their weight is prohibitive on long missions.

So as we gear up for more government and private commercial space exploration and development, we need conferences where we can discuss and exchange information in this area.

NETS fills this role. It is a topical meeting of the American Nuclear Society (ANS), hosted by the Aerospace Nuclear Science and Technology Division and the ANS Eastern Washington Section. Papers presented at the meeting can be seen here. Everything was discussed, from Nuclear Powered Cryobots that can access the oceans of Icy Planets like Europa, to Nuclear Thermal Rockets, to developing special composite and polymer materials to withstand long times in space.

Keynote speeches from former astronaut and entrepreneur Dr. Franklin Chang-Diaz, NASA Associate Administrator Steve Jurczyk, and John Kelly, the President of the American Nuclear Society set the stage for the meeting.

As Dr. Christopher Morrison notes, synergistic sharing of information is essential now that the global space market is $400 billion/year. Presently 72 different government space agencies are in existence, although only 14 of those have launch capability, and only six have full launch capabilities which includes the ability to launch and recover multiple satellites, deploy cryogenic rocket engines and operate space probes.

These six include the China National Space Administration (CNSA), the European Space Agency (ESA), the Indian Space Research Organization (ISRO), the Japan Aerospace Exploration Agency (JAXA), the National Aeronautics and Space Administration(NASA), and the Russian Federal Space Agency (RFSA or Roscosmos).

Nuclear energy in space has come in and out of fashion over the decades. For the last 50 years, we have used radioisotope electric propulsion systems and radiothermal generators (RTGs) to power long missions far from the Sun, like the Voyager missions to Jupiter and beyond, or the New Horizons mission to the outer Solar System. Pu-238 is the best isotope, emitting steady heat from natural radioactive decay by emitting alpha particles that thermocouples then convert to electricity. Its 88-year half-life means the missions can be long in duration.

However, RTGs cannot achieve the high-power density needed for large remote applications and there is not enough supply to meet the kilowatt- and megawatt-scale power needs of human spaceflight and off-world bases.

The next big step is to provide power for human settlements. These will require kilowatt and megawatt power systems for life support, propulsion of large payloads, and off-world industry. While solar energy works well in many locations for small loads, nuclear energy is necessary for large loads in locations far from the sun or places like the moon whose surface has long periods of darkness.

An ideal solution is a combination of both power sources, but the survival of a group of humans will require the certainty and reliability of nuclear power. A recent analysis at MIT, corroborates this Ė we need more powerful, miniaturized nuclear engines to go farther and faster into space.

This is not new. NASA launched a nuclear fission system called SNAP-10A in 1965, and Russia launched over 30 fission-powered spacecraft during the Cold War. In addition, in the 1960ís NASA successfully ground tested dozens of nuclear rockets in a program called NERVA.

This artistís concept shows four fission-based modular nuclear power stations powering a human outpost on Mars. The system could be supplemented with solar and battery arrays.NASA

More recently, NASA ground tested a tiny nuclear reactor that is perfect for powering a colony on Mars or the Moon, fueling a large spacecraft to a distant star, or operating a mining operation in the asteroid belt.

Called the Kilopower Fission Power Project, the reactors are designed to provide 1 to 10 kW of electrical power, and can be set up in coordinated modules, which could be used for more science instruments, to power electric propulsion systems, or to support human exploration or colonies on another planet (see figure). It would provide higher data rate communications with a smaller antenna, something that is more important than one might think.

Traditional terrestrial nuclear reactor designs are big. A space reactor, with a power level in the kW range, would be a million times lower power than most reactors on Earth. This translates to simplicity and low cost. For example, the Kilopower reactor core is only the size of a roll of paper towels and the entire system with all of its components and shielding, is about the weight of a car.

Until recently, putting anything into orbit around the Earth was incredibly expensive. Any object orbiting the Earth was worth its weight in 14 karat gold. The international space station is the most expensive object built in modern human history with a cost of 100 billion dollars to build. These costs put space travel strictly in the realm of governments.

But that is changing. Designing, building, and operating complex technology has never been easier in all of history. The manufacturing, materials, and computer codes are orders of magnitude better than they were in the 1960s. This has dropped the cost of developing space faring capabilities to a level cheap enough to be at the finger-tips of private companies such as Blue Origin, SpaceX, and even smaller companies like Rocket Lab.

The space market, now about $400 billion/year, is set to grow to between $1 trillion and $4 trillion per year by 2040). Last year, the market for electricity in the United States was only $400 billion. So the economic push is great to evolve these systems. Jeff Bezos (Blue Origin) and Elon Musk (SpaceX) started their companies with the mission of enabling millions of people to live and work in space. SpaceX launch vehicles have dropped the cost of spaceflight by a factor of 15, and that should continue to drop by another factor of 5.

For fission power systems, this is game changing. In the past, the launch cost was simply too great to achieve the critical mass requirements necessary for colonization. What held back humanity from pursuing endeavors beyond Earth orbit was cost, and now that barrier has been lifted.

So the gateway to space is open in the way that the internet was opened in the 1990ís. And nuclear energy is the power that will get us through that gate. When humans are ready to live and work in space, nuclear energy must be ready as well. That nuclear power is the safest energy source on Earth doesnít hurt.

Dr. James Conca is an expert on energy, nuclear and dirty bombs, a planetary geologist, and a professional speaker. Follow him on Twitter @jimconca.

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