An issue with Canada\u2019s Special Purpose Dexterous Manipulator (SPDM) robot \u201cDextre\u201d is being evaluated, after engineers identified a potential failure mode in the SPDM Power Switching Init (PSU). As a result, the robot will remain in its current position attached to the Destiny Lab until further notice.<\/p>\n<\/p>\n
Dextre is capable of robotic execution of ISS external maintenance tasks, such as the removal and replacement of dexterous compatible Orbit Replaceable Units (ORUs), and the servicing of scientific payloads.<\/p>\n
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Supporting EVA-based maintenance is also part of its role, with the preposition of ORUs or Integrated Assemblies, the provision of lighting and camera support, and is it is also capable of actuating external mechanisms, performing inspection tasks, and extending the reach of the SSRMS (Space Station Remote Manipulator System).<\/p>\n
The robot arrived on the International Space Station (ISS) during STS-123.<\/p>\n
The preliminary information into the latest issue with Dextre \u2013 which was noticed last Friday \u2013 relates to a possible single-point failure mode with the SPDM Power Supply Unit.<\/p>\n
\u201cOn Friday afternoon we received data that MDA had identified a potential failure mode in the SPDM power switching unit (PSU) that could result in power flowing through from one power channel to another,\u201d noted one of several memos on L2 on Tuesday.<\/p>\n
\u201cPreliminary inputs we received from MDA (MacDonald, Dettwiler and Associates Ltd) and CSA (Canadian Space Agency) were that the failure should not affect the planned SPDM operations (this month), but after asking a few questions it became clear that they had not fully assessed the impacts of the failure.\u201d<\/p>\n
Company News (adsbygoogle = window.adsbygoogle || []).push({});<\/p>\n Dextre was due to be put through its paces this month \u2013 as early as this week \u2013 via the SSRMS. However, this is now postponed until further notice, due to a concern the issue may lead to Dextre being trapped on the end of the Station\u2019s robotic arm. Such an issue would impact on February\u2019s STS-119 mission.<\/p>\n \u201cDuring a teleon, it was determined that this failure could result in trapping the SPDM on the SSRMS, or trapping the SPDM on the MBS (Mobile Base System),\u201d added an opening memo. \u201cBoth of which would present significant impacts to 15A (STS-119).<\/p>\n \u201cIn addition, our current flight rules prohibit us from using the SSRMS to maneuver SPDM unless we are able to release the SPDM (so that the SSRMS is free to perform higher priority operations).<\/p>\n \u201cGiven the uncertainty associated with this failure its potential impacts and recovery actions, it seemed to me that taking the SPDM off the Lab PDGF (Power and Data Grapple Fixture) exposes us to risk of trapping the SPDM on the SSRMS.\u201d<\/p>\n As a result of this potential concern, engineers agreed that keeping Dextre on its current location would be prudent, until they can be assured the failure does not affect the ability to relocate the SPDM within their current set of rules.<\/p>\n \u201cSo for now, until we are directed otherwise, we expect that the SPDM operations planned for next week will be deferred,\u201d added the memo. \u201cWe will start looking at what that does to the checkout plan and the road-to-RPCM (Remote Power Control Module) R&R over the next few days.\u201d<\/p>\n Another memo, written on Tuesday, explained the issue relating to Dextre\u2019s PSU \u2013 in more technical detail.<\/p>\n \u201cIf this happens, you\u2019ve tied two non-parallel DDCUs together and could potentially damage the RPC on the redundant power leg due to high current flowing backwards through it. Best case is the RPC sees the high current and trips off. Or other equipment could be damaged as the two DDCUs tied together are both grounded to structure.<\/p>\n \u201cIt gets worse when SPDM is based on the SSRMS since here you could fry SSRMS components plus potentially have a hot LEE causing sparking and arcing when you try to grapple. Could end up with SPDM stuck at the end of the arm to avoid this.<\/p>\n \u201cBased on this possibility, the robotics community has recommended cancelling planned SPDM OCR session #2. I concur with that recommendation. Disappointing for everyone involved in this effort, but prudent.\u201d<\/p>\n Further notes of the forward plan were mentioned, although engineers are still working on the evaluations.<\/p>\n It may yet be found that the issue is workable, and will not result in any negative impact on operations. However, due diligence in understanding the potential fault path will continue until engineers are confident Dextre can begin its important role on the orbital outpost.<\/p>\n More will follow on this story as information arrives.<\/p>\n L2 members<\/em><\/em>: All documentation \u2013 from which the above article has quoted snippets \u2013 is available in full in the related L2 sections, now over 4000 gbs in size.<\/em><\/em><\/p>\n","protected":false},"excerpt":{"rendered":" An issue with Canada\u2019s Special Purpose Dexterous Manipulator (SPDM) robot \u201cDextre\u201d is being evaluated, after engineers identified a potential failure mode in the SPDM Power Switching Init (PSU). As a result, the robot will remain in its current position attached to the Destiny Lab until further notice. Dextre is capable of robotic execution of ISS […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"inline_featured_image":false,"footnotes":"","_links_to":"","_links_to_target":""},"categories":[2],"tags":[8854,233,9123],"class_list":["post-41235","post","type-post","status-publish","format-standard","hentry","category-news","tag-dextre","tag-iss","tag-sts-119"],"acf":[],"_links":{"self":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/41235"}],"collection":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/comments?post=41235"}],"version-history":[{"count":0,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/41235\/revisions"}],"wp:attachment":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media?parent=41235"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/categories?post=41235"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/tags?post=41235"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}See Also<\/h4>\n
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\u201cSPDM PSU has two strings, prime and redundant. The concern is that the redundant power supply relay could fail closed. It\u2019s a FET controller, so I presume we\u2019re talking a FET Controller Hybrid (FCH) type failure,\u201d added another memo on L2.<\/p>\n