ready for Fusion
The words of Thomas O. Paine perfectly describe why we must prepare now for the advent of fusion power rather than waiting until it arrives. Fusion technology underwent rapid advancement during the 1960s to 1990s due to competition between budding global superpowers. Today, much of the fields progress comes from startups like Helion, Tokamak Energy, and TAE Technologies which only have recently received serious funding. Backing more of these intelligent, fast-moving, scalable startups will bring fusion — with net gain back to the grid — within the next ten years.
“Only a miraculous insight could have enabled the scientists of the eighteenth century to foresee the birth of electrical engineering in the nineteenth. It would have required a revelation of equal inspiration for a scientist of the nineteenth century to foresee the nuclear power plants of the twentieth. No doubt, the twenty-first century will hold surprises, and more of them. But not everything will be a surprise. It seems certain that the twenty-first century will be the century of scientific and commercial activities in outer space, of manned interplanetary flight, and the establishment of permanent human footholds outside the planet earth.”
— Thomas O. Paine, the 3rd Administrator of NASAWhy do we need Helium-3?
The Deuterium-Tritium (D-T) reaction is the basis for current nuclear fusion research. This reaction is troublesome as 80% of the energy released comes from energetic neutrons. The energy from these neutrons needs to be captured and converted to energy through thermal devices, which introduce additional losses through their inherent inefficiencies. Furthermore, containing these energetic neutrons with magnetic fields will never be completely effective, causing damage as they interact with the reactor wall. Eventually, these walls will need to be repaired — an expensive process requiring that all power generation cease as well as a considerable risk of environmental contamination. Finally, the half-life of tritium is 12.3 years, meaning that waste material will need to be safeguarded for about 100 years before radiation levels are safe for the material to be recycled.
The optimal fuel source for fusion reactors is the isotope Helium-3 (3He). Neither the reactants nor the Deuterium-Helium-3 (D-3He) reaction products are radioactive. D-3He does not suffer from the same containment issue as D-T since the reaction does not produce high-energy neutrons that crash into the reactor wall. Instead, the products of the D-3He reaction, protons, are electrically charged. As a result, generators can manipulate the products with electromagnetic fields to directly convert some energy to electricity, which is much more efficient than thermal energy conversion (source).
Deterium and Helium-3 Fusion Reaction, Non-Radioactive Byproducts
pHASE 1
Proof of Engine Tech — VOICE
Over the past several million years, solar winds have deposited an estimated 1.1 million metric tonnes of 3He on the Lunar surface — enough fuel to power the entire United States at present energy usage rates for 44,000 years. Further, samples collected by Neil Armstrong during the 1969 Apollo 11 mission show that 3He is present in Lunar surface regolith at 13 parts per billion. At this concentration, we need only mine 4.3 cubic meters of Lunar regolith to obtain one kilogram of 3He, the equivalent of a 12 m tall square at a depth of only one inch. Regolith at this depth will be fine and powdery and only require scraping the surface.
Phase 1 will see the production of a 10-kilowatt engine for use in a robot capable of collecting regolith and depositing it at a collection location for future processing. These initial robots will be designed with simplicity and mass production in mind, permitting more extensive operations through larger fleets. This phase will be critical for testing system automation and demonstrating to the world that we are ready for Phase 2.
pHASE 2
Proof of Process — Automated refinement
The Fusion Technology Institute and the Wisconsin Center for Space Automation and Robotics (University of Wisconsin) estimate that 13 gigajoules of energy will be required to mine a single kilogram of Helium-3 (source). In Phase 2, VOICE engineers will develop the technology for "shaking and baking" the stockpiled regolith to extract the 3He (Robert Zubrin - The Case for Space).
Although this research shows good ratios of energy expenditure to gain, the proposed plan was not economically feasible at the time of publication. At the time, launch costs for a Saturn V rocket were around $4,200 per kilogram, meaning that the development and deployment of the proposed system would cost $75.6M! However, with the technological advances made by SpaceX in recent years, launch costs have dropped as low as $2,000 per kilogram onboard a Falcon 9 rocket. Further, reusing the rocket ten times would reduce the cost to a mere $200 per kilogram, or $3.6M total.
We envision a future of Lunar mining that does not require solar power (either direct solar flux or beamed radio waves) to operate. To this end, VOICE will utilize its exhaust heat to provide the 4,100 GJ of energy necessary for outgassing the 3He from the regolith.
For Phase 2, we create a larger, 200 kW implementation of the Phase 1 engine for use in processing. A similar engine operating at 30% efficiency would waste 650 kW of energy as heat. Recycling only half of this waste heat will eliminate the need for solar power in processing regolith. The Fusion Technology Institute found that 84 GJ of energy would be needed to power the machines, compressors, conveyor system, excavation, and locomotion requirements of their 18-tonne mining system. This machine would produce 33 kg of 3He over one year of part-time operation. Unlike the Fusion Institute, which proposed a heavy mobile processing plant, VOICE will use a stationary depot, requiring far less energy for locomotion. Concurrently with the development of this Phase 2 technology, the surface scraping operation of Phase 1 will be actively scaling up and accumulating regolith stockpiles.
pHASE 3
Profitability — Helium 3 Return
A kilogram of Helium-3 in a D-3He fusion reactor operating at a 60% efficiency would output about 100 GWh of electricity. That is more than four times the energy produced from one kilogram of Uranium-235 in fission, which also produces heavy amounts of lasting radioactive material. At the standard domestic rate for electricity, $0.06 per kilowatt-hour, a D-3He fusion reactor would net $6M per kilogram of 3He. Supposing electric companies were willing to spend one-third of their gross revenue on fuel for fusion reactors, 3He could sell for upwards of $2M per kilogram. At this rate, 3He would be worth its weight in gold 50 times over and certainly justifiable for return to earth.