Aneutronic fusion, that is initiated and supported by the fission of Lithium-6 with neutrons, allows us to create a compact fusion reactor that has no adverse reaction products.

Compact fission reactors, even clean ones, involve critical mass of fuels that have the capacity to sustain criticality.

https://upload.wikimedia.org/wikiped...um-sphere.jpeg

When a nuclear chain reaction is self-sustaining, the mass is said to be in a critical state. There is no increase or decrease in power, temperature, or neutron population.

Critical mass depends on the neutron multiplication factor k. The average number of neutrons released per fission event that go on to cause another fission event rather than being absorbed or leaving the material. When k = 1, the mass is critical, and the chain reaction is self-sustaining.

A subcritical mass is a mass who's activity will exponentially decrease. In this case, k 1.

A supercritical mass is one where there is an increasing rate of fission. Reactors use materials that settle into equilibrium after startup since high temperatures reduce cross section. When supercritical, k 1.

The mass where criticality occurs may be changed. Attributes such as fuel mixture, fuel shape, fuel temperature, fuel density and neutron-reflective blankets affect critical mass.

http://www.dtic.mil/dtic/tr/fulltext/u2/a196877.pdf

This is an interesting reaction. A reaction that converts a neutron flux into a flux of alpha particles and tritium using Lithium-6, and thence to neutron flux again.

We start with Li-6 and a neutron which is a source of tritium for nuclear fusion, through low-energy nuclear fission.

6 3Li + n → 4 2He ( 2.05 MeV ) + 3 1T ( 2.75 MeV )

The Tritium decays into Helium 3 ion and an electron along with an anti-neutrino with a 4500 day half life.

3 1T → 3 2He + e− + _ν (18.76 KeV)

Now, energetic alpha particles react with Beryllium to produce Carbon-12 and a neutron.

9 4Be + 4 2He → 12 6C + n

Energetic tritium particles also react with Deuterium to produce alpha particles and energetic neutrons.

2 1D + 3 1T → 4 2He ( 3.5 MeV ) + n0 ( 14.1 MeV )

The energetic neutrons reacts with Beryllium to produce two lower energy neutrons which scatter off Beryllium and are absorbed by Lithium-6.

9 4Be + n → 2(4 2He) + 2n

and Be-9 and a neutron yields 2 neutrons

9 4Be + n → 8 4Be + 2 n.

Starting the cycle again.

The amount of energy released for the net reaction is 22.4 MeV and the atomic weight of all the fuel components is 17 grams per mole. So, 1 MeV = 1..602677·10^(-13) J and 1 mole = 6.02*10^(-23) atoms. This comes out to be 9.34 GJ/gram - or about 1.5 barrels of oil equivalent per gram of Lithium-6-Beryllium Deuteride fuel.

http://link.springer.com/article/10....2871175#page-1

https://www.sciencedaily.com/release...0128113356.htm

http://www.sciencedirect.com/science...25838800008835

http://pubs.acs.org/doi/abs/10.1021/...nalCode=jpccck

Critical mass is inversely proportional to the square of the density. A Lithium6-Beryllium-Deuteride salt has a density of 720 kg/m3 and a critical mass of 140 kg in a neutron reflective shell of Beryllium and lead. This critical reaction is started with a blast of neutrons and controlled by changing the efficiency of the neutron reflective blanket. Such a reactor is capable of releasing 93,300 barrels of oil equivalent energy before being recharged. Actually given the changing cross sections involved, and the efficiencies achievable at the temperatures possible, this will produce around 10,000 barrels of oil equivalent energy before needing to be refueled. A 200 kW generator would have a 10 year life span operating continuously. Sufficient to power 125 homes.

Getting a little more fancy, its possible to compress the Lithium-6-Beryllium-Deuteride salt to 150x resting density using an inductive shell. This reduces critical mass by 22,500 times from 140 kg to 6.3 grams. This tiny pellet only one inch (2.55 cm) across releases 58.8 GJ (14 ton TNT) when detonated. This will be used to make highly efficient multi-gigawatt generators...

http://www.osti.gov/scitech/servlets/purl/1172154

And efficient fusion rockets..

http://msnwllc.com/Papers/FDR_AIAA_2011.pdf

A 1954 12 cylinder 5.4 litre Jaguar engine at 5,500 rpm produces 210 kW (282 HP) undergoes 2,750 detonations per cylinder per minute, or 33,000 detonations per minute - 550 detonations per second.

Detonating these tiny units at the same 550 detonations per second in powerful magnetic fields that eject the plasma in a preferred direction, at 4,320 km/sec, produce

F = mdot * Ve = (0.0063 * 550) * 4,320,000 = 14.97 MN (1,526 metric tons force)

The power output of this engine is

P = 0.5 * mdot * Ve^2 = 0.5 * 0.0063 * (4,320,000)^2 = 58.8 GW.

This system can produce one gee acceleration for 122.367 hours by blasting through 964.6 tons of propellant carrying 561.4 tons of payload.

Two nacelles with a propulsive array situated on either of a space faring hull - with the nacelles carrying 657.3 cubic meters of 1 inch diameter spheres with a delivery system. Nacelles that carries 85 kg/m3 - or 6604 cubic meters hull.

https://goo.gl/kbUvQz

So, four floors that are 2.4 meters tall, with a beam of 37 meters and a length of 74 meters, and 2,752 square feet of floor space, with two nacelles 4.8 meters in diameter and 38 meters long.

This fusion propulsion system is far closer to reality than the drive mentioned here, and makes a dandy little interplanetary runabout.

With Tesla changing the nature of motoring, increasing demand for Lithium for electric drive vehicles, we see demand rising to 150,000 tons per year. Extracting Lithium-6 and adding Beryllium 11,250 tons of Lithium-6, 16,875 tons of Beryllium, 3,750 tons of Deuterium, 31875 tons of fuel. 9125 tons of fuel will be needed to provide energy for terrestrial energy, which produces $2.6 trillion per year. This means that 2 runabouts can be operated more or less continuously throughout the solar system.


On Friday, April 22, 2016 at 6:26:42 AM UTC+12, Rick Jones wrote:
http://www.theregister.co.uk/2016/04...ve_theory_why/

The EmDrive's thrust can be predicted (and tested), says
McCulloch, by accounting for radiation pressure from Unruh
waves. These cause the momentum to increase as the thruster
moves. McCulloch suggests the same effect accounts for the
anomalies observed when spacecraft accelerate around a planet:
they jump.

rick jones
--
I don't interest myself in "why." I think more often in terms of
"when," sometimes "where;" always "how much." - Joubert
these opinions are mine, all mine; HPE might not want them anyway...
feel free to post, OR email to rick.jones2 in hpe.com but NOT BOTH...