{"id":138595,"date":"2017-11-01T19:53:14","date_gmt":"2017-11-01T19:53:14","guid":{"rendered":"https:\/\/www.nextbigfuture.com\/?p=138595"},"modified":"2017-11-01T19:53:14","modified_gmt":"2017-11-01T19:53:14","slug":"positron-dynamics-1-5-million-bridge-round-fund-is-still-open","status":"publish","type":"post","link":"https:\/\/www.nextbigfuture.com\/2017\/11\/positron-dynamics-1-5-million-bridge-round-fund-is-still-open.html","title":{"rendered":"Positron Dynamics $1.5 million bridge round fund is still open"},"content":{"rendered":"

Propelx is still raising the $1.5 million bridge round for Positron Dynamics.<\/A> It is over 80% raised. Accredited investors can still contribute to Positron Dynamics.<\/p>\n

Positron Dynamics is developing antimatter propulsion for spacecraft.<\/a> They are working towards nearterm propulsion for cubesats.<\/p>\n

\n* Sodium 22 isotope (which they get in liquid form) will produce positrons which will be moderated with semiconductor structures <\/p>\n

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Liquid Sodium 22<\/i><\/p>\n

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The Moderator structure<\/i><\/p>\n

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Cold positrons instead of 1 million times hotter than the sun<\/i><\/p>\n

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\n* moderated cold positrons produced in a gamma ray beam
\n* The beam hits the dense film of deuterium which produces fusion products
\n* the fusion products are now charged particles which can be then guided as propulsive thrust with magnets<\/p>\n

positron emission: \u00b2\u00b2Na \u2192 \u00b2\u00b2Ne + 1 e\u207a + 0.94 MeV of kinetic energy
\npositron annihilation: e\u207a + matter \u2192 pion (5%) or kaon (95%)
\nkaon decay: kaon \u2192 muon (80%) in 20 nsec
\nmuon capture: muon + D or T \u2192 mD or mT
\nfusion (1): mD + T \u2192 \u2074He + \u00b9n + muon (non-consumed) (0.01 – 0.1 nsec)
\nfusion (2): mT + D \u2192 \u2074He + \u00b9n + muon (non-consumed) (0.01 – 0.1 nsec)
\nfusion (3): mD + D \u2192 \u00b3He + \u00b9n + muon (non-consumed) (0.07 – 1.5 nsec)
\nmuon decay: muon + time \u2192 electron + neutrinos (2,200 nsec)<\/p>\n

\u00b2\u00b2Na (sodium missing one neutron) is almost perfect. Halflife of 2.6 years. <\/p>\n

Each gram of the stuff:<\/p>\n

1 g \u2022 ( 6.023\u00d710\u00b2\u00b3 atom\/mol \u00f7 22 AMU ) = 2.74\u00d710\u00b2\u00b2 atoms per gram
\n= 434,400,000,000,000 decays per second.
\n\u00d7 1.6\u00d710\u207b\u00b9\u2079 J\/eV \u00d7 1,000,000 eV\/MeV \u00d7 2.843 MeV\/decay
\n= 197 joules per gram<\/p>\n

Muon Catalyzed Fusion<\/b><\/p>\n

Muons are unstable subatomic particles. They are similar to electrons, but are about 207 times more massive.<\/p>\n

The \u03b1-sticking problem is the approximately 1% probability of the muon “sticking” to the alpha particle<\/A> 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 \u03b1-sticking probability, finding the \u03b1-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. <\/p>\n

However Muon Catalyzed fusion from antimatter would multiply the energy production from the antimatter.<\/p>\n

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.<\/p>\n

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<\/p>\n

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Description of a pellet based antimatter catalyzed fusion system but gives an idea of performance based on percent of material that is fused<\/i><\/p>\n

* the 6U cubesat that they will use to test the propulsion in space will be generating 100s of watts
\n* the propulsion will have delta V of 1 to 10 km\/second
\n* Later systems will have more delta V and enable cubesats and small satellites to stay in orbit for years instead of days<\/p>\n

* the cubesats with propulsion will enable very low orbit internet satellites<\/p>\n

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* 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
\n* Later beyond 2030, they will have regenerative isotopes for a lot more power and achieve ten million ISP and several kilonewtons of propulsive force
\n* could enable 1G acceleration and deceleration propulsion which would 3.5 weeks to Pluto<\/p>\n

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