{"id":178043,"date":"2019-03-23T19:58:00","date_gmt":"2019-03-24T00:58:00","guid":{"rendered":"https:\/\/www.panix.com\/~msaroff\/40years\/2019\/03\/23\/what-is-darpas-endgame-here\/"},"modified":"2019-03-23T19:58:00","modified_gmt":"2019-03-24T00:58:00","slug":"what-is-darpas-endgame-here","status":"publish","type":"post","link":"https:\/\/www.panix.com\/~msaroff\/40years\/2019\/03\/23\/what-is-darpas-endgame-here\/","title":{"rendered":"What is DARPA&#8217;s Endgame Here?"},"content":{"rendered":"<div>DARPA is looking to <a href=\"https:\/\/aviationweek.com\/defense\/darpa-wants-assemble-demo-nuclear-rocket-orbit\">assemble and test a nuclear thermal rocket in orbit<\/a>.<\/div>\n<p>Nuclear thermal rockets typically have around twice the I<sub>sp<\/sub> (basically fuel economy) of chemical rockets, on the order of 800\u20141000, which is a lot less than than electric propulsion, which is typically ten times that of chemical rockets, but the available thrust produced is far greater, 100-1000 kilo-newtons for nuclear thermal vs. 10-500 milli-newtons for the various electric rockets.<\/p>\n<p>For longer missions, Mars and the further, it&#8217;s clear that electric propulsion is better and faster, so the only applications that I see are some sort of manned moon base, or an as yet undisclosed military mission:<\/p>\n<blockquote><p><span style=\"color: blue;\">DARPA plans to demonstrate a nuclear thermal propulsion (NTP) system that can be assembled on orbit to expand U.S. operating presence in cislunar space, according to the Pentagon advanced research agency\u2019s fiscal 2020 budget request. <\/p>\n<p>The agency is seeking $10 million in 2020 to begin a new program, Reactor On A Rocket (ROAR), to develop a high-assay low-enriched uranium (HALEU) propulsion system. \u201cThe program will initially develop the use of additive manufacturing approaches to print NTP fuel elements,\u201d DARPA\u2019s budget document says. <\/p>\n<p>\u201cIn addition, the program will investigate on-orbit assembly techniques (AM) to safely assemble the individual core element subassemblies into a full demonstration system configuration, and will perform a technology demonstration,\u201d the document says. <\/p>\n<p>In a nuclear thermal rocket, propellant such as liquid hydrogen is heated to high temperature in a nuclear reactor then expanded through a rocket nozzle to produce thrust. Propulsive efficiency, or specific impulse, can be twice that of a chemical rocket. <\/span><\/p><\/blockquote>\n<p>Given the advances in electric propulsion, I do not see where nuclear thermal will have an advantage, except possibly for supplying a moon base or some as yet undisclosed military program.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>DARPA is looking to assemble and test a nuclear thermal rocket in orbit. Nuclear thermal rockets typically have around twice the Isp (basically fuel economy) of chemical rockets, on the order of 800\u20141000, which is a lot less than than electric propulsion, which is typically ten times that of chemical rockets, but the available thrust &hellip;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[],"tags":[452,419,382],"class_list":["post-178043","post","type-post","status-publish","format-standard","hentry","tag-propulsion","tag-space","tag-technology"],"_links":{"self":[{"href":"https:\/\/www.panix.com\/~msaroff\/40years\/wp-json\/wp\/v2\/posts\/178043"}],"collection":[{"href":"https:\/\/www.panix.com\/~msaroff\/40years\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.panix.com\/~msaroff\/40years\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.panix.com\/~msaroff\/40years\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.panix.com\/~msaroff\/40years\/wp-json\/wp\/v2\/comments?post=178043"}],"version-history":[{"count":0,"href":"https:\/\/www.panix.com\/~msaroff\/40years\/wp-json\/wp\/v2\/posts\/178043\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.panix.com\/~msaroff\/40years\/wp-json\/wp\/v2\/media?parent=178043"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.panix.com\/~msaroff\/40years\/wp-json\/wp\/v2\/categories?post=178043"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.panix.com\/~msaroff\/40years\/wp-json\/wp\/v2\/tags?post=178043"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}