Ryan had two later videos. One for Wired and one for TEDx.
Reviewing the videos based on information from Ryan Weed.
* Sodium 22 isotope (which they get in liquid form) will produce positrons which will be moderated with semiconductor structures
Liquid Sodium 22
The Moderator structure
Cold positrons instead of 1 million times hotter than the sun
* moderated cold positrons produced in a gamma ray beam
* The beam hits the dense film of deuterium which produces fusion products
* the fusion products are now charged particles which can be then guided as propulsive thrust with magnets
positron emission: ²²Na → ²²Ne + 1 e⁺ + 0.94 MeV of kinetic energy
positron annihilation: e⁺ + matter → pion (5%) or kaon (95%)
kaon decay: kaon → muon (80%) in 20 nsec
muon capture: muon + D or T → mD or mT
fusion (1): mD + T → ⁴He + ¹n + muon (non-consumed) (0.01 – 0.1 nsec)
fusion (2): mT + D → ⁴He + ¹n + muon (non-consumed) (0.01 – 0.1 nsec)
fusion (3): mD + D → ³He + ¹n + muon (non-consumed) (0.07 – 1.5 nsec)
muon decay: muon + time → electron + neutrinos (2,200 nsec)
²²Na (sodium missing one neutron) is almost perfect. Halflife of 2.6 years.
Each gram of the stuff:
1 g • ( 6.023×10²³ atom/mol ÷ 22 AMU ) = 2.74×10²² atoms per gram
= 434,400,000,000,000 decays per second.
× 1.6×10⁻¹⁹ J/eV × 1,000,000 eV/MeV × 2.843 MeV/decay
= 197 joules per gram
Muon Catalyzed Fusion
Muons are unstable subatomic particles. They are similar to electrons, but are about 207 times more massive.
The α-sticking problem is the approximately 1% probability of the muon “sticking” to the alpha particle that results from deuteron-triton nuclear fusion, thereby effectively removing the muon from the muon-catalysis process altogether. Recent measurements seem to point to more encouraging values for the α-sticking probability, finding the α-sticking probability to be about 0.5% (or perhaps even about 0.4% or 0.3%), which could mean as many as about 200 (or perhaps even about 250 or about 333) muon-catalyzed d-t fusions per muon. Indeed, the team led by Steven E. Jones achieved 150 d-t fusions per muon (average) at the Los Alamos Meson Physics Facility. Unfortunately, 200 (or 250 or even 333) muon-catalyzed d-t fusions per muon is still not enough to reach break-even. Even with break-even, the conversion efficiency from thermal energy to electrical energy is only about 40% or so, further limiting viability.
However Muon Catalyzed fusion from antimatter would multiply the energy production from the antimatter.
Each muon catalyzing d-d muon-catalyzed fusion reactions in pure deuterium is only able to catalyze about one-tenth of the number of d-t muon-catalyzed fusion reactions that each muon is able to catalyze in a mixture of equal amounts of deuterium and tritium, and each d-d fusion only yields about one-fifth of the yield of each d-t fusion, thereby making the prospects for useful energy release from d-d muon-catalyzed fusion at least 50 times worse than the already dim prospects for useful energy release from d-t muon-catalyzed fusion.
However, Positron Dynamics is looking at the fusion for propulsion and not energy production. The fusion rate for d-d muon-catalyzed fusion has been estimated to be only about 1% of the fusion rate for d-t muon-catalyzed fusion, but this still gives about one d-d nuclear fusion every 10 to 100 picoseconds or so
Description of a pellet based antimatter catalyzed fusion system but gives an idea of performance based on percent of material that is fused
* the 6U cubesat that they will use to test the propulsion in space will be generating 100s of watts
* the propulsion will have delta V of 1 to 10 km/second
* Later systems will have more delta V and enable cubesats and small satellites to stay in orbit for years instead of days
* the cubesats with propulsion will enable very low orbit internet satellites
* in the 2020s if things go well they will be able to scale to 10 km/second to 100 km/second with 10-100 kilogram payloads for small probe exploration of the solar system
* Later beyond 2030, they will have regenerative isotopes for a lot more power and achieve ten million ISP and several kilonewtons of propulsive force
* could enable 1G acceleration and deceleration propulsion which would 3.5 weeks to Pluto
Brian Wang is a Futurist Thought Leader and a popular Science blogger with 1 million readers per month. His blog Nextbigfuture.com is ranked #1 Science News Blog. It covers many disruptive technology and trends including Space, Robotics, Artificial Intelligence, Medicine, Anti-aging Biotechnology, and Nanotechnology.
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