Posted on November 30, by Scott Alexander I.
To keep the crew and the computers alive you have to shield them from both gamma rays and pions.
As far as the crew is concerned both reaction products come under the heading of "deadly radiation. Given an absorbing propellant or radiation shield of a specific density you can figure the thickness that will stop all the pions.
This is the pion's "range" through that material. In table the columns under the yellow bar show how many centimeters the "range" of the given stopping material is required to absorb MeV of pion energy. The two sets of orange bars is because while the range is relatively constant for all high energies, the range becomes dramatically less at the point where the pion energy drops below MeV the "last MeV".
But you only need 27 centimeters of water to absorb MeV from a 75 MeV pion. Since hydrogen, helium, and nitrogen have regrettably low densities the reaction chamber will have to operate at high pressure to get the density up to useful levels.
The Space Shuttle engines operated at a pressure of atmospheres, is a bit excessive. So of the gases nitrogen might be preferrable, even though you can get better specific impulse out of propellants with lower molecular weight.
Range of charged pions from Antiproton Annihilation Propulsion Using more calculations that were not explained figure was produced. The curve is the relative intensity of a charged pion at a given kinetic energy in MeV.
The MeV pions are the most intense there are more of themthe average energy is MeV. Mean Life is the lifespan not half-life of a pion at that energy in nanoseconds. The range of a pion at that energy can be measured on the RANGE scales below, traveling through vacuum, hydrogen H2 propellant at atm, nitrogen N2 propellant at atm, and tungsten radiation shielding.
Gamma Rays Sadly gamma rays cannot be used to propel the rocket well, actually there are a couple of strange designs that do use gammasall they do is kill anything living and destroy electronic equipment. So you have to shield the crew and electronics with radiation shielding.
This is one of the big drawbacks to antimatter rockets. Gamma-rays would be useful if you were using antimatter as some sort of weapon instead of propulsion.
A small number of "prompt" gamma-rays are produced directly from the annihilation reaction. The prompt gammas have a whopping MeV, but they only contribute about 0. A much larger amount of "delayed" gamma-rays are produced by the neutral pions decaying 90 attoseconds after the antimatter reaction.
As mentioned abovethe antimatter reaction is basically spitting out charged pions and gamma rays.In this paper, I review three major purposes for arms control negotiations — disarmament, stability, and advantage. In the first part of the paper, I compare the three purposes against the causes of war literature to show that each provides a defensible.
Published: Mon, 5 Dec Human beings have been using fossil fuels for hundreds of years, satisfying the demand of industrialization. The behavior of using fossil fuels, on the other hand, causes huge pollution, such as soil, water and atmosphere contamination.
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