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Groups > sci.electronics.design > #519143
| From | Martin Brown <'''newspam'''@nezumi.demon.co.uk> |
|---|---|
| Newsgroups | sci.electronics.design |
| Subject | Re: various OTs |
| Date | 2018-10-13 10:13 +0100 |
| Organization | Aioe.org NNTP Server |
| Message-ID | <ppscv6$14eb$1@gioia.aioe.org> (permalink) |
| References | <r2u1sddojvr815ukjlm0qhsr5bpa2fbe6s@4ax.com> <dnh79f-9sv.ln1@coop.radagast.org> <hq72sdp4ahpattfstmlvdaju80bqlc3amp@4ax.com> |
On 12/10/2018 23:30, John Larkin wrote: > On Fri, 12 Oct 2018 14:53:17 -0700, dplatt@coop.radagast.org (Dave > Platt) wrote: > >>> https://wattsupwiththat.com/2018/10/12/another-space-telescope-shuts-down-one-week-after-hubble/ >>> >>> Gyros, reaction wheels, seem to be a chronic problem in satellites. I >>> have a friend who designs cubesats, and he says that the gyros are the >>> most expensive and unreliable parts. >> >> ... which suggests that this is a Hard Problem. I don't find that >> surprising. Gyro bearings are a "moving part" (unlike a lot of what's >> in satellites). Almost by definition they have to take a big torque >> load on the bearing surfaces when they operate, since part of their >> job is to twist the satellite around into a new orientation. They >> often have to operate over an extreme temperature range (cold-of- >> eclipse to heat-of-full-sun) with the range going back and forth >> multiple times per day (for a LEO satellite at least). And, there's >> no opportunity to replace, or relubricate the bearings once the sat is >> in service, in most cases. >> >> I don't know what material they use in the bearings for those gyros, >> but suspect that they're probably frightfully expensive. > > My naiive concept is that things don't need bearings in zero G and > hard vacuum. Just a little magnetic suspension. Of course, a zero-G > maglev (spherical?) gyro would be hard to test on the ground; maybe we > have finally found a use for the ISS, manufacturing gyros. They need bearings or magnetic suspension that can handle the forces that occur when the satellite is being rotated by using the gyros. If they could avoid using mechanical bearings they would do so. Almost all sensor gyros are counter rotating laser beams these days. It is only the devices that have to provide real forces that move. The moving parts with serious kinetic energy and high torque are always by far the most unreliable components especially in spacecraft. We had maglev turbopumps for a while on our kit. It was wonderful in earthquake free zones but one day the entire of Tokyo moved an inch to the left and every damn one of the things was written off in an instant. We even had an earthquake in our factory which did in a couple and the UK is not known as a hotbed of earthquake activity. After that they went back to traditional bearings for almost all customer sites. You have clearly never sat on a swivel chair and played with a spinning lead rimmed bicycle wheel. It is quite fun to try and the forces on the bearings are distinctly non-trivial when you use it to move a mass. -- Regards, Martin Brown
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various OTs John Larkin <jjlarkin@highland_snip_technology.com> - 2018-10-12 12:50 -0700
Re: various OTs George Herold <gherold@teachspin.com> - 2018-10-12 13:04 -0700
Re: various OTs John Larkin <jjlarkin@highland_snip_technology.com> - 2018-10-12 13:48 -0700
Re: various OTs George Herold <gherold@teachspin.com> - 2018-10-12 17:46 -0700
Re: various OTs dplatt@coop.radagast.org (Dave Platt) - 2018-10-12 14:53 -0700
Re: various OTs John Larkin <jjlarkin@highland_snip_technology.com> - 2018-10-12 15:30 -0700
Re: various OTs Martin Brown <'''newspam'''@nezumi.demon.co.uk> - 2018-10-13 10:13 +0100
Re: various OTs John Larkin <jjlarkin@highlandtechnology.com> - 2018-10-13 09:33 -0700
Re: various OTs Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2018-10-13 14:15 -0400
Re: various OTs Martin Brown <'''newspam'''@nezumi.demon.co.uk> - 2018-10-15 10:09 +0100
Re: various OTs John Larkin <jjlarkin@highlandtechnology.com> - 2018-10-15 06:50 -0700
Re: various OTs Clive Arthur <cliveta@nowaytoday.co.uk> - 2018-10-13 10:37 +0100
Re: various OTs DecadentLinuxUserNumeroUno@decadence.org - 2018-10-13 10:01 +0000
Re: various OTs John Larkin <jjlarkin@highland_snip_technology.com> - 2018-10-13 11:08 -0700
Re: various OTs John Larkin <jjlarkin@highlandtechnology.com> - 2018-10-13 09:55 -0700
Re: various OTs MikeP <mjp993@googlemail.com> - 2018-10-16 03:22 +0000
Re: various OTs Robert Baer <robertbaer@localnet.com> - 2018-10-13 22:39 -0700
Re: various OTs Sjouke Burry <burrynulnulfour@ppllaanneett.nnll> - 2018-10-14 21:43 +0200
Re: various OTs Robert Baer <robertbaer@localnet.com> - 2018-10-15 19:46 -0700
Re: various OTs DecadentLinuxUserNumeroUno@decadence.org - 2018-10-12 23:55 +0000
Re: various OTs Lasse Langwadt Christensen <langwadt@fonz.dk> - 2018-10-12 16:58 -0700
Re: various OTs bill.sloman@ieee.org - 2018-10-12 17:52 -0700
Re: various OTs speff <spehro@gmail.com> - 2018-10-18 06:53 -0700
Re: various OTs John Larkin <jjlarkin@highlandtechnology.com> - 2018-10-18 06:59 -0700
Re: various OTs tabbypurr@gmail.com - 2018-10-18 14:10 -0700
Re: various OTs "Tim Williams" <tiwill@seventransistorlabs.com> - 2018-10-18 17:49 -0500
Re: various OTs Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2018-10-18 21:04 -0400
Re: various OTs Steve Wilson <no@spam.com> - 2018-10-19 01:34 +0000
Re: various OTs <698839253X6D445TD@nospam.org> - 2018-10-19 07:11 +0000
Re: various OTs "Tim Williams" <tiwill@seventransistorlabs.com> - 2018-10-12 19:10 -0500
Re: various OTs Lasse Langwadt Christensen <langwadt@fonz.dk> - 2018-10-13 06:22 -0700
Re: various OTs Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2018-10-13 14:16 -0400
Re: various OTs John Larkin <jjlarkin@highlandtechnology.com> - 2018-10-13 17:19 -0700
Re: various OTs whit3rd <whit3rd@gmail.com> - 2018-10-13 12:24 -0700
Re: various OTs Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2018-10-13 17:30 -0400
Re: various OTs Jasen Betts <jasen@xnet.co.nz> - 2018-10-14 20:13 +0000
Re: various OTs John Larkin <jjlarkin@highland_snip_technology.com> - 2018-10-14 13:59 -0700
Re: various OTs Steve Wilson <no@spam.com> - 2018-10-14 23:58 +0000
Re: various OTs Steve Wilson <no@spam.com> - 2018-10-15 01:05 +0000
Re: various OTs Jasen Betts <jasen@xnet.co.nz> - 2018-10-15 05:57 +0000
Re: various OTs DecadentLinuxUserNumeroUno@decadence.org - 2018-10-15 11:09 +0000
Re: various OTs <698839253X6D445TD@nospam.org> - 2018-10-15 07:23 +0000
Re: various OTs "Tim Williams" <tiwill@seventransistorlabs.com> - 2018-10-13 21:39 -0500
Re: various OTs bitrex <user@example.net> - 2018-10-13 00:08 -0400
Re: various OTs <698839253X6D445TD@nospam.org> - 2018-10-13 06:59 +0000
Re: various OTs John Larkin <jjlarkin@highland_snip_technology.com> - 2018-10-13 12:08 -0700
Re: various OTs <698839253X6D445TD@nospam.org> - 2018-10-13 07:27 +0000
Re: various OTs speff <spehro@gmail.com> - 2018-10-18 06:55 -0700
Re: various OTs Winfield Hill <hill@rowland.harvard.edu> - 2018-10-13 07:32 -0700
Re: various OTs John Larkin <jjlarkin@highland_snip_technology.com> - 2018-10-13 12:17 -0700
Re: various OTs Joseph Gwinn <joegwinn@comcast.net> - 2018-10-15 08:37 -0400
Re: various OTs Martin Brown <'''newspam'''@nezumi.demon.co.uk> - 2018-10-15 13:58 +0100
Re: various OTs Tom Gardner <spamjunk@blueyonder.co.uk> - 2018-10-15 14:34 +0100
Re: various OTs Clifford Heath <no.spam@please.net> - 2018-10-16 10:26 +1100
Re: various OTs Clive Arthur <cliveta@nowaytoday.co.uk> - 2018-10-16 10:46 +0100
Re: various OTs tabbypurr@gmail.com - 2018-10-16 08:46 -0700
Re: various OTs Clive Arthur <cliveta@nowaytoday.co.uk> - 2018-10-16 19:53 +0100
Re: various OTs tabbypurr@gmail.com - 2018-10-17 05:56 -0700
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