Nasa announces new rover mission to Mars in 2020 |
Nasa announces new rover mission to Mars in 2020 |
Sep 13 2019, 03:07 PM
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#271
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Senior Member Group: Members Posts: 2428 Joined: 30-January 13 From: Penang, Malaysia. Member No.: 6853 |
I'm not quite sure how you can accurately measure the C of G without the MMRTG being installed or at least a dummy unit of the correct size / mass being used...
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Sep 13 2019, 07:38 PM
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#272
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Founder Group: Chairman Posts: 14432 Joined: 8-February 04 Member No.: 1 |
As I understand it - these balance masses are entirely unrelated to EDL. The two cruise balance masses on one side of the backshell, and entry balance masses on the opposite side are designed so the vehicle is balanced during the spin stabilized cruise, then unbalanced before entry to give it the angle of attack required for guided entry, and then rebalanced before parachute deployment. I believe these total something around 150kg ejected both before entry, then before 'chute deployment.
The rover's CoG also needs to be characterized as part of the whole stack of the vehicle. It needs to match a conservatively predicted mass and CoG so as not to throw the rest of the vehicle off. The mass properties of the RTG are well known - you can 'balance' the vehicle without it, knowing how it will change the properties. You are not literally 'balancing' the vehicle on a spin table like that - you're simply characterizing the CoG. This is where the analogy of balancing a tyre kind of falls apart..... on one of those machines you actually need to balance it right then and there. |
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Sep 13 2019, 08:59 PM
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#273
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Senior Member Group: Members Posts: 2511 Joined: 13-September 05 Member No.: 497 |
and then rebalanced before parachute deployment... As part of the amusingly-named "straighten up and fly right" (SUFR) maneuver. See https://trs.jpl.nasa.gov/bitstream/handle/2...629/10-1775.pdf -------------------- Disclaimer: This post is based on public information only. Any opinions are my own.
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Sep 13 2019, 10:13 PM
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#274
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Member Group: Members Posts: 910 Joined: 4-September 06 From: Boston Member No.: 1102 |
Thanks to all who responded for adding insight into mass balance issues. A very interesting topic as most space craft issues are.
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Sep 13 2019, 10:17 PM
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#275
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Founder Group: Chairman Posts: 14432 Joined: 8-February 04 Member No.: 1 |
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Sep 14 2019, 12:52 AM
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#276
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Merciless Robot Group: Admin Posts: 8783 Joined: 8-December 05 From: Los Angeles Member No.: 602 |
...what could possibly go wrong there...?
-------------------- A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
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Sep 16 2019, 11:40 PM
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#277
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Junior Member Group: Members Posts: 99 Joined: 17-September 07 Member No.: 3901 |
Article on getting Mars 2020 center of gravity balanced Link I'm a bit surprised...44 pounds of tungsten weights...44 pounds that scientist would love to add. Maybe someone can explain why the position of components can't be re positioned slightly. The article refers to 9 separate weights, so they average about 5 pounds, not the same thing as being able to accommodate a 44-pound instrument. The large number of weights and the use of a spin table seems consistent with "dynamic balancing," which is more than simply adjusting the c.g. position. Dynamic balancing orients the principal axes of inertia to avoid wobble when rotating. The engineer quoted in the article likened it to tire balancing at a gas station, perfectly appropriate except that the procedure is now done at automotive tire shops, rarely at "gas stations" anymore. Repositioning components would be complicated, considering many hard constraints on component locations, and presumably it would be taboo to drill new mounting holes in the frame at this late stage of assembly in the clean room. Adjustable mounting brackets for components could be an engineering nightmare, adding extra weight and the possibility of things shaking loose and changing position. Thanks Floyd for posting the September 12 article, I was wondering why the rover has been absent from the regular clean room webcam view this past week. <https://mars.nasa.gov/mars2020/mission/where-is-the-rover/> |
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Oct 7 2019, 09:30 PM
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#278
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Member Group: Members Posts: 866 Joined: 15-March 05 From: Santa Cruz, CA Member No.: 196 |
interesting quick read on the landing vision system on arsTechnica
i'd almost forgotten about this addition, more info |
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Oct 8 2019, 01:01 AM
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#279
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Senior Member Group: Members Posts: 2511 Joined: 13-September 05 Member No.: 497 |
the landing vision system... Huh. I wonder who built this camera? I haven't seen anything public about it anywhere. -------------------- Disclaimer: This post is based on public information only. Any opinions are my own.
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Oct 12 2019, 12:18 AM
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#280
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Member Group: Members Posts: 866 Joined: 15-March 05 From: Santa Cruz, CA Member No.: 196 |
I havent seen that either, although some interesting (if brief) details on p.7,8 of this pdf here
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Oct 31 2019, 08:12 PM
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#281
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Newbie Group: Members Posts: 17 Joined: 12-August 12 Member No.: 6541 |
I'm curious: are there reasons to suspect that Jezero crater is more likely to preserve signs of ancient life (had it existed) compared to Gale crater?
I know that they're both ancient lake systems, with Jezero being an open lake system and Gale being a closed one. Does that or other differences influence biosignature preservation? |
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Oct 31 2019, 08:44 PM
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#282
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Administrator Group: Admin Posts: 5172 Joined: 4-August 05 From: Pasadena, CA, USA, Earth Member No.: 454 |
It's because of the delta within Jezero. More here: https://www.planetary.org/blogs/emily-lakda...2020-rover.html
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Oct 31 2019, 08:57 PM
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#283
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Newbie Group: Members Posts: 17 Joined: 12-August 12 Member No.: 6541 |
It's because of the delta within Jezero. More here: https://www.planetary.org/blogs/emily-lakda...2020-rover.html Thanks! Great article. |
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Jan 14 2020, 01:35 PM
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#284
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Senior Member Group: Members Posts: 2511 Joined: 13-September 05 Member No.: 497 |
Semifinalists of naming contest announced: https://www.futureengineers.org/nametherover
-------------------- Disclaimer: This post is based on public information only. Any opinions are my own.
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Jan 14 2020, 02:20 PM
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#285
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Member Group: Members Posts: 813 Joined: 8-February 04 From: Arabia Terra Member No.: 12 |
Nice to see that I was not alone in thinking Clarity would be an appropriate name.
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