{"id":597,"date":"2020-03-10T19:53:28","date_gmt":"2020-03-10T23:53:28","guid":{"rendered":"http:\/\/www.irrelevant-tech.com\/?p=597"},"modified":"2020-03-10T19:53:28","modified_gmt":"2020-03-10T23:53:28","slug":"staying-alive-on-venus","status":"publish","type":"post","link":"https:\/\/www.irrelevant-tech.com\/index.php\/2020\/03\/10\/staying-alive-on-venus\/","title":{"rendered":"Staying alive on Venus"},"content":{"rendered":"

The most hostile place in the entire solar system that it is possible to land on is the surface of Venus.\u00a0 The airless sun-baked surface of the Moon only gets to 260\u00b0F during daylight.\u00a0 The surface of Mercury, closest to the Sun, peaks at 801\u00b0F.\u00a0 But the surface of Venus is at 872\u00b0F both day and night with a corrosive atmospheric at a pressure of 1350 psi or 93 times the Earth\u2019s.\u00a0 The Russians, famed for rugged equipment, have landed probes on Venus at least 11 times.\u00a0 The record for lander survival was set by Venera 13 on March 1, 1982, at 2 hours and 7 minutes.\u00a0 Venus survival is so difficult that NASA is soliciting outside ideas with their Venus Rover Design Competition<\/a>.\u00a0 They are looking for ways to control and maneuver rovers without computers or electronics.\u00a0 The main problem is that modern electronic devices cannot stand this kind of heat and die completely at 400\u00b0F or so.\u00a0 It is completely infeasible to try to refrigerate the sensitive electronics and sensors because of the power requirements and the very high thermal gradient any refrigeration system would have to fight through. Not just the semiconductors and processors, but even current insulation and substrates, will not work at anywhere near these temperatures.\u00a0 Nor will ordinary power sources.\u00a0 Any lander will be accompanied by one or more orbiters that can receive information if it can be gathered.\u00a0 Some creative ideas involve radar reflective panels that can be moved mechanically to change the lander albedo to signal data to an orbiter.\u00a0 Others involve purely mechanical means for using extended probes to steer around holes and obstacles.<\/p>\n

If you assume a pressure vessel, so the internal parts of the lander can be maintained at low or zero pressure to eliminate corrosion issues, the remaining problem is temperature.\u00a0 While 872\u00b0F exceeds the working temperature of most engineering technology, this environment is actually within the reach of the amateur.\u00a0 A typical self-cleaning kitchen oven runs at 900\u00b0F for a 4+ hour cycle.\u00a0 Not as fancy as NASA\u2019s Venus Surface Simulator but useful for testing magnets, bearings, insulators, and mechanisms.\u00a0 One proposed solution to the power source problem is a windmill.\u00a0 While the average wind speed on Venus is only 3 MPH, the air density is 93 times higher than on Earth, providing plenty of power for a windmill.\u00a0 The main problems are bearings and power transfer.\u00a0 There are hybrid ceramic and carbon sleeve bearings which are rated for these temperatures although not these pressures in this atmosphere.\u00a0 Magnetic bearings eliminate friction and corrosion issues.\u00a0 Unfortunately, the current top magnet material, Neodymium-Iron-Boron, loses its magnetism at such temperatures.\u00a0 The next best, Samarium-Cobalt, has some high temperature versions that will only lose part of their strength.\u00a0 These can be preconditioned at temperature and then used.\u00a0 The older ALNICO 9 is able to work at Venus temperatures but starts out with about 1\/3 the strength of Samarium-Cobalt.\u00a0 It\u2019s not clear which of an ALNICO or SmCo solution would be lighter and\/or smaller.\u00a0 Power could be transferred into the pressure vessel through a magnetic coupler consisting of a permanent magnet rotor surrounding an internal stator\/generator separated by a nonmagnetic stainless steel cup in the wall of the pressure vessel. The overall idea is to figure out how to accomplish the science goals with technology that can operate at 872\u00b0F.<\/p>\n

While NASA is looking into silicon carbide semiconductors, there are other possibilities.\u00a0 One possibility is old tech: vacuum tubes.\u00a0 In 1959 RCA invented the nuvistor<\/a>, an advanced 0.4\u201dx0.8\u201d subminiature metal\/ceramic vacuum tube.\u00a0 While the kinds of glass subminiature tubes used in the AN\/PRC-6 \u201cwalkie-talkie\u201d radio might work at these temperatures, the nuvistor<\/a> technology would be a better starting point.\u00a0 One interesting feature was the RCA \u201cdark cathode\u201d that operated 630 degrees cooler than standard filaments.\u00a0 The reduced heater operating temperature resulted in greatly increased tube life and reliability.\u00a0 Starting at Venus temperatures would significantly reduce filament power. \u00a0More advanced materials might allow a Venus ambient temperature cathode without heater power.\u00a0 The main problem is thermionic emission leakage from the grid, which limited the maximum temperature for the nuvistor<\/a>.\u00a0 In an advanced design, vacuum depositing a silicon dioxide film on the grid might produce an analog of an insulated gate, suppressing grid leakage.\u00a0 There are metal-ceramic transmitter tubes like the 4CX150 that could be used as a starting point for developing high-temperature transmitter finals.\u00a0 Circuit connections would need to be welded rather than soldered.\u00a0 Most components would need to be rethought since traditional insulators will not work.\u00a0 Capacitors could be air, glass, mica, or suitable ceramics.\u00a0 Resistors could be metal film on ceramic or wire-wound on ceramic cores.\u00a0 Inductors would be printed on ceramic laminated substrates or air-wound on ceramic spacers.\u00a0 This is mostly existing radio technology.<\/p>\n

One application would be small instrument packages that could be dropped in large numbers, consisting of a few simple sensors, a vacuum tube transmitter, and a solid electrolyte battery.\u00a0 These are batteries already in use by the military.\u00a0 They are extremely rugged and are completely solid and inactive at room temperature.\u00a0 They are intended to run at temperatures in the Venus range where the electrolyte melts and becomes active.\u00a0 Normally these batteries are actuated by pyrotechnic charges in artillery shells, rockets, or such but they could be part of a constellation of small Venus probes reporting temperature, seismic activity, or other data over wide areas for a limited time.\u00a0 They would easily survive a multi-year space flight prior to insertion.\u00a0 Multiple waves of probes could be used for longer data sets.<\/p>\n

A long-term lander with a wind power source could support a wider range of sensors over a longer time frame.\u00a0 With a method to generate high enough voltages and development of a high temperature photo cathode, it should be possible to use an image or line orthicon to transmit spectra.\u00a0 Sapphire, ALON, or quartz windows would allow light sensing and slow-scan imaging. \u00a0Decades of television before the 1960\u2019s demonstrated that this is well within the range of tube technology.\u00a0 Mechanical scanning from an even earlier era is another possibility.\u00a0 With magnetic bearings in a vacuum environment the scanner power consumption could be very low.\u00a0 An idea brought up by various people is that you don\u2019t need a computer or controller on the surface; you just need a receiver and transmitter in the lander with a control computer in the orbiter or orbiters.\u00a0 Kind of like a really expensive drone.<\/p>\n

Although NASA is looking into making processor chips out of silicon carbide, a non-trivial task, for over a decade computers were designed with vacuum tubes.\u00a0 All logic functions, nand, nor, register, etc, can be handled by tubes, which in modern guise could be very small and very low powered compared to the best of the tube era, the nuvistor<\/a>. While the original tube computers were monsters, they needed to run fast to solve major problems in a reasonable amount of time.\u00a0 You don\u2019t need much of a computer to miss a rock or transmit some data.\u00a0 Specifically, a one-bit architecture like the PDP-8\/S, WANG 500, or Motorola MC14500B with a little memory can compute anything with a minimum of physical hardware.\u00a0 While it would be slow, it would minimize size and power consumption while providing adequate control for the lander.\u00a0 A high temperature version of the Mercury computer program store could be a possibility here.<\/p>\n

Please leave comments using the post in my comments category.<\/p>\n","protected":false},"excerpt":{"rendered":"

The most hostile place in the entire solar system that it is possible to land on is the surface of Venus.\u00a0 The airless sun-baked surface of the Moon only gets to 260\u00b0F during daylight.\u00a0 The surface of Mercury, closest to the Sun, peaks at 801\u00b0F.\u00a0 But the surface of Venus is at 872\u00b0F both day … Continue reading “Staying alive on Venus”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[5,7],"tags":[85,84],"class_list":["post-597","post","type-post","status-publish","format-standard","hentry","category-engineering","category-final-frontier","tag-lander","tag-venus"],"_links":{"self":[{"href":"https:\/\/www.irrelevant-tech.com\/index.php\/wp-json\/wp\/v2\/posts\/597","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.irrelevant-tech.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.irrelevant-tech.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"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=597"}],"version-history":[{"count":7,"href":"https:\/\/www.irrelevant-tech.com\/index.php\/wp-json\/wp\/v2\/posts\/597\/revisions"}],"predecessor-version":[{"id":604,"href":"https:\/\/www.irrelevant-tech.com\/index.php\/wp-json\/wp\/v2\/posts\/597\/revisions\/604"}],"wp:attachment":[{"href":"https:\/\/www.irrelevant-tech.com\/index.php\/wp-json\/wp\/v2\/media?parent=597"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.irrelevant-tech.com\/index.php\/wp-json\/wp\/v2\/categories?post=597"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.irrelevant-tech.com\/index.php\/wp-json\/wp\/v2\/tags?post=597"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}