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{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/EILLEC3YIDJOFYNYA2IZVXOOYOVFSNQF/",
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    "message_id": "004f01c6ecb4$9bbdbf50$21567646@djxe18",
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    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/EILLEC3YIDJOFYNYA2IZVXOOYOVFSNQF/",
    "sender": {
        "address": "rjansson (a) cfl.rr.com",
        "mailman_id": "9b211bcd8a0642788e6dc055f3930699",
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    "sender_name": "Dick Jansson-rr",
    "subject": "[eagle]  Module Thermal Dissipation",
    "date": "2006-10-10T21:39:47Z",
    "parent": null,
    "children": [],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
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    "content": "Eagle module power dissipations as noted in my paper recently published\nfor the AMSAT Space Symposium, are shown below.. The allowable\ndissipations presume a module temperature of 20°C in a 0°C spacecraft. \n\n\n\nTable 1\n\n\nMean Emittance, v\n\nAllowable Power Dissipation, Q\n\n\n0.045\n\n0.4 W\n\n\n0.15\n\n1.3 W\n\n\n0.45\n\n3.9 W\n\n\n0.91\n\n7.9 W\n\nIt would be exceptionally presumptuous on my part to assume that all\nmodules will be of 7.9W dissipation as the spacecraft will not have that\nlevel of power generation (12 \"low power\" modules at 7.9W = 94.8W, plus\n4 \"high power\" modules at 50W = 200W, totaling 295W). To achieve that\nlevel (7.9W) of power will require the use of internal heat sinking. \n\nOn the PCB dissipation, if we are to limit the temperature rise, in a\n20°C module, to 40°C or a PCB of 60°C total, then the PCB dissipation\nwould be 5.35W, somewhat less than the 7.9W allowed in a 20°C module.\nThus to achieve the 7.9W other heat sinking methods would need to be\nused.\n\nI fully realize that modern-day electronics are quite compact and have\nsignificant power densities, but I personally shudder at some of these\nabove noted power densities in a vacuum environment. This is the basis\nof my previously noted conservatism in PCB power densities. There are\nsome particularly critical modules that MUST be low power. These are\nthose involved in the commanding of the spacecraft, the command receiver\nand the IHU. The noted reason for this mandate is that of the cooling\neffects of the spaceframe during eclipse and the need to maintain the\ncommand-loop equipment in suitable operating condition regardless of the\nradical eclipse cooling of the spaceframe. During a 2-3hour eclipse, the\nspaceframe can cool to as low as -80°C or below. These conditions have\nbeen observed in prior P3 spacecrafts.\n\nThis whole ongoing discussion merely further reinforces my concept that\nclose work between the electronic designers and the thermal designer for\nEagle is sorely needed. In this environment I feel that the days of\nwily-nily electronic design, damn the thermal torpedoes, are gone.\nModule design must be done as a cooperative, multi-technology effort.\nThis is why I again emphasize that all designers should read my recently\npresented paper.\n\n \nDick Jansson\n---------------------------\n <mailto:[email protected]> [email protected]\n---------------------------\n\n \n\n\n\n",
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