{"id":243,"date":"2017-08-09T20:24:54","date_gmt":"2017-08-10T00:24:54","guid":{"rendered":"http:\/\/64.25.106.130\/?page_id=243"},"modified":"2017-09-04T14:58:40","modified_gmt":"2017-09-04T18:58:40","slug":"electrostatic-cosmic-ray-shield","status":"publish","type":"page","link":"https:\/\/www.irrelevant-tech.com\/index.php\/electrostatic-cosmic-ray-shield\/","title":{"rendered":"Electrostatic Cosmic Ray Shield"},"content":{"rendered":"

Cosmic ray particles, especially those over 40 MeV, are the major radiation danger in outer space.\u00a0 These are almost entirely positively charged protons, alpha particles, and heavier nuclei.\u00a0 Negatively charged beta particles \u2013 electrons \u2013 make up a fraction of 1% and can be blocked by mechanical shielding.\u00a0 Some of the positive particles are Solar Energetic Particles (SEP) generated by solar flares or by coronal mass ejections with energies up to a few MeV.\u00a0 The rest are galactic or extra-galactic particles with energies ranging to over 3 x 1020<\/sup> eV.\u00a0 Fortunately the frequency of these high energy particles falls off<\/a> in a steep power law such that well over 99.9% of cosmic rays have a kinetic energy of less than 20GeV.<\/p>\n

The Apollo missions were of a few days duration and were flown during a quiet sun period.\u00a0 The astronauts returned directly to earth, where they were again protected by its atmosphere and magnetic field.\u00a0 The ISS orbit is within the earth\u2019s magnetic field which eliminates particles under 10 GeV. \u00a0In both cases crew exposure is strongly limited even without protection.\u00a0 By contrast the situation is critical for long duration space flights or space habitats away from earth where the exposure duration may be decades.\u00a0 The crew will be subject to the full range of solar weather and may never return to the protected earth environment.\u00a0 On flights beyond the heliopause the situation is much worse<\/a> because of very high levels of additional particles below 2 GeV.<\/p>\n

Various magnetic shield topologies have been investigated.\u00a0 It has been proposed to give the spacecraft a net positive charge.\u00a0 This is difficult to maintain as it attracts every free electron in the universe to neutralize it.\u00a0 An alternative would be a neutral electrostatic shield as is presented here, using current technology.\u00a0 The main engineering problem for sufficient field strength would be the size required to avoid breakdown; however, light objects can be very large in microgravity.\u00a0 The neutral structure would consist of a positively charged central hull surrounded by a negatively charged grid with the entire assembly spun to generate gravity within the hull and to balance the Coulomb force between the hull and the grid.\u00a0 For long duration flights or habitats, spin gravity is the only current practical solution to microgravity induced health problems.\u00a0 When passing through an area of higher radiation the grid could be pumped up to a higher voltage and the spin increased.\u00a0 The crew would move inboard to lower gravity areas and would have more of the vessel structure between them and the outside environment.<\/p>\n

The first architecture would be an elliptical hull 3 km long and 500 meters in diameter.\u00a0 Three km is sufficient space for an axial 50 GeV linear electron accelerator driven by klystrons.\u00a0 A 2 km dielectric support strut would extend on axis from the cold end of the hull.\u00a0 A 2 km beam tube inside another axial support strut would extend from the hot end of the LINAC.\u00a0 This tube would be provided with quadrapole focusing magnets to keep the beam collimated.\u00a0 The outer end of the beam tube would be an electron capture and secondary emission suppression structure.\u00a0 The grid would extend between the outboard ends of the two support struts and when fully expanded would have a radius of 1.5 km, yielding a clearance of at least 1 km from the hull.\u00a0 A good material for the grid might be metalized ultra-high-molecular-weight polyethylene<\/a> fiber, which has an extremely high specific strength.\u00a0 The amount of metal should be minimized as the Coulomb force is proportional to the area of the metal in the grid, as is the amount of charge required to reach a given voltage.\u00a0 The 50 GeV LINAC is required to charge the grid relative to the hull.<\/p>\n

The second architecture would be an elliptical hull 2 km long and 1 km in diameter.\u00a0 In the 1 km diameter waist would be a 50 GeV electron synchrotron.\u00a0 A separate 2 km dielectric support strut would extend on axis from each end of the hull.\u00a0 Up to 3 tangential beam tubes would extend from pick-offs at the synchrotron out to a 2 km radius conductive ring.\u00a0 Balancing tangential dielectric support struts would also support the ring.\u00a0 The beam tubes would be provided with quadrapole focusing magnets to keep the beam collimated.\u00a0 The outer end of the beam tubes would have an electron capture and secondary emission suppression structure.\u00a0 The grid would extend between the outboard ends of the two support struts and the ring.\u00a0 When fully expanded it would have a radius of about 2 km, yielding a clearance of at least 1 km from the hull.\u00a0 A good material for the grid could again be metalized ultra-high-molecular-weight polyethylene<\/a> fiber, which has an extremely high specific strength.\u00a0 The amount of metal should be minimized as the Coulomb force is proportional to the area of the metal in the grid, as is the amount of charge required to reach a given voltage.\u00a0 The 50 GeV synchrotron is required to charge the grid relative to the hull.<\/p>\n

It is proposed that the nominal hull-grid differential be around 20 GeV.\u00a0 This will suppress SEP completely and other particle radiation by three orders of magnitude, yet is low enough to preclude vacuum breakdown over 1 km.\u00a0 As mentioned above, this could be increased in high radiation areas with an increased risk of breakdown.\u00a0 Remotely controlled electron emitters facing the hull would be provided on the grid supports to discharge the grid gracefully in order to allow repairs or such activities as docking with other spacecraft.\u00a0 At such times the off duty crew would retire to a protected core area.\u00a0 The electron cathode emitters could be thermionic devices consisting of ceramic tubes or plates with passages under the surface and covered with thoriated tungsten.\u00a0 These would be heated by burning fuel and oxidizer stored in the pylons.\u00a0 Preferably these would be either hypergolic fuel pairs such as dinitrogen tetroxide \/ hydrazine or catalytically ignited fuels such as hydrogen mixtures using platinum black to eliminate ignition hardware.\u00a0 The burning fuel would be passed through the cathodes’ internal passages with topology designed for even heat distribution, and exhausted outward in a balanced manner.\u00a0\u00a0 Spinning a spacecraft creates problems, but the human issues have to take precedence in decades long missions.\u00a0 Communications, for instance, could be handled by antennas mounted on counter-rotating donuts on the hull around the bases of the axial struts.\u00a0 For habitats and astrometry level accuracy, instruments could be mounted on external platforms.<\/p>\n

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Cosmic ray particles, especially those over 40 MeV, are the major radiation danger in outer space.\u00a0 These are almost entirely positively charged protons, alpha particles, and heavier nuclei.\u00a0 Negatively charged beta particles \u2013 electrons \u2013 make up a fraction of 1% and can be blocked by mechanical shielding.\u00a0 Some of the positive particles are Solar … Continue reading “Electrostatic Cosmic Ray Shield”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-243","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.irrelevant-tech.com\/index.php\/wp-json\/wp\/v2\/pages\/243","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.irrelevant-tech.com\/index.php\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/www.irrelevant-tech.com\/index.php\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/www.irrelevant-tech.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.irrelevant-tech.com\/index.php\/wp-json\/wp\/v2\/comments?post=243"}],"version-history":[{"count":9,"href":"https:\/\/www.irrelevant-tech.com\/index.php\/wp-json\/wp\/v2\/pages\/243\/revisions"}],"predecessor-version":[{"id":282,"href":"https:\/\/www.irrelevant-tech.com\/index.php\/wp-json\/wp\/v2\/pages\/243\/revisions\/282"}],"wp:attachment":[{"href":"https:\/\/www.irrelevant-tech.com\/index.php\/wp-json\/wp\/v2\/media?parent=243"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}