Extricating Spirit, Digging out from Troy |
Extricating Spirit, Digging out from Troy |
Dec 9 2009, 07:16 PM
Post
#346
|
|
Junior Member Group: Members Posts: 43 Joined: 13-June 08 Member No.: 4206 |
Perhaps this is the correct place to post this or not.. (moderators??)
Why didn't the mer design team use brushless motors? Most certainly the tech has been developed for the past 50 years and would prove much more reliable imho. Was it a cost issue? Weight/size? Power output/efficiency? With 2 dead wheels on the right side I don't see how we can have a mobile rover, let alone escape from the trap. |
|
|
Dec 9 2009, 08:06 PM
Post
#347
|
|
Founder Group: Chairman Posts: 14431 Joined: 8-February 04 Member No.: 1 |
Remember - they were only specified for 90 sols of driving, approx 600-1000 metres.
They have both done many many times that. So it's only fair to say that the motors have far outperformed their requirements. Brushless are a newer technology, a more complex technology, and are heavier http://starsys.spacedev.com/starsysproduct...rticle.asp?id=1 http://trs-new.jpl.nasa.gov/dspace/handle/2014/38930 For what was required - brushed was the proven choice. |
|
|
Dec 9 2009, 08:12 PM
Post
#348
|
|
Member Group: Members Posts: 507 Joined: 10-September 08 Member No.: 4338 |
With 2 dead wheels on the right side I don't see how we can have a mobile rover, let alone escape from the trap. I believe one of the "plan Bs" (or maybe "plan Z" for this one) is to try energizing the right front wheel again in the hope that it might somehow have started working again. They have said they are reluctant to try this because of the possibility that it is shorted, in which case energizing it might cause damage to other driving circuits. However, if the RR wheel is truly gone, there might be little to lose in trying that at least. |
|
|
Dec 9 2009, 08:34 PM
Post
#349
|
|
Senior Member Group: Moderator Posts: 4279 Joined: 19-April 05 From: .br at .es Member No.: 253 |
However, if the RR wheel is truly gone, there might be little to lose in trying that at least. The problem is "what would be damaged if they try to energize the RF wheel?" Would it be limited to the RF wheel control circuitry or would it extend to other areas like the IDD? If it's the former I would concur with you but I fear it is the latter and in this case we would lose almost all science capability and not only the driving. |
|
|
Dec 9 2009, 08:38 PM
Post
#350
|
|
Founder Group: Chairman Posts: 14431 Joined: 8-February 04 Member No.: 1 |
They can't move both IDD and wheels at the same time - I think they may be tied on the same power distro. board.
|
|
|
Dec 10 2009, 04:44 PM
Post
#351
|
|
Member Group: Members Posts: 507 Joined: 10-September 08 Member No.: 4338 |
Why is it that energizing the RR wheel in the current diagnostics does not carry the same risk of propagating a short as would energizing the RF wheel? What was the basis for suspecting a short in the RF wheel and why does that not apply to the RR wheel?
|
|
|
Dec 10 2009, 05:15 PM
Post
#352
|
|
Senior Member Group: Members Posts: 2173 Joined: 28-December 04 From: Florida, USA Member No.: 132 |
....What was the basis for suspecting a short in the RF wheel... Elevated current. I don't know if any elevated current has been seen in the RR.Edit: Actually, from this report, it looks like the RR may have the opposite of a short: "The resistance tests indicate anomalously high resistance in the motor winding..." |
|
|
Dec 10 2009, 06:37 PM
Post
#353
|
|
Member Group: Members Posts: 691 Joined: 21-December 07 From: Clatskanie, Oregon Member No.: 3988 |
Since the RR wheel is submerged completely, have they thought of possible soil particles that may have found its way into the gearbox itself? Does the resistance test's show that signature?
|
|
|
Dec 10 2009, 08:24 PM
Post
#354
|
|
Member Group: Members Posts: 507 Joined: 10-September 08 Member No.: 4338 |
from this report, ... anomalously high resistance in the motor winding..."[/i] The report says: "a curious transition from anomalously low resistance to high resistance was observed very briefly..." Doesn't that suggest an initial short followed by a broken circuit? |
|
|
Dec 10 2009, 10:47 PM
Post
#355
|
|
Senior Member Group: Members Posts: 2173 Joined: 28-December 04 From: Florida, USA Member No.: 132 |
|
|
|
Dec 10 2009, 10:52 PM
Post
#356
|
|
Member Group: Members Posts: 239 Joined: 18-December 07 From: New York Member No.: 3982 |
New update on the Free Spirit site.
http://www.jpl.nasa.gov/freespirit/index.cfm Two interesting quotes: "The plan ahead, still being developed, will likely include more rotor resistance tests, an attempt to apply higher voltage to the right-rear wheel to see if any movement will occur, and a check of the right-front wheel to confirm its status and to see if it may offer insight into the right-rear wheel's condition." "Because of the current rover tilt, the environmental conditions and dust accumulation on the solar arrays, Spirit is at risk of inadequate power for surviving through the next southern Mars winter, which reaches solstice on May 13, 2009." |
|
|
Dec 10 2009, 11:18 PM
Post
#357
|
|
Newbie Group: Members Posts: 18 Joined: 25-May 09 Member No.: 4794 |
"Because of the current rover tilt, the environmental conditions and dust accumulation on the solar arrays, Spirit is at risk of inadequate power for surviving through the next southern Mars winter, which reaches solstice on May 13, 2009." One presumes they mean 2010 |
|
|
Dec 10 2009, 11:30 PM
Post
#358
|
|
Senior Member Group: Members Posts: 4246 Joined: 17-January 05 Member No.: 152 |
The check of the RF wheel definitely sounds interesting. I wonder if that means an attempt to drive it.
We'd heard about the danger of the coming winter, but not this bit: QUOTE Even if extrication is not possible, some limited rover motion may be able to improve rover tilt and increase the chance of winter survival.
|
|
|
Dec 11 2009, 04:28 AM
Post
#359
|
|
Member Group: Members Posts: 530 Joined: 21-March 06 From: Canada Member No.: 721 |
Given the current position, how would that be possible other than to intentionally dig the front in even deeper to get more northerly tilt? Perhaps the statement might better read, once we determine that extrication is impossible, some limited rover motion....
|
|
|
Dec 12 2009, 11:48 AM
Post
#360
|
||
The Poet Dude Group: Moderator Posts: 5551 Joined: 15-March 04 From: Kendal, Cumbria, UK Member No.: 60 |
One of the new hazcam images suggests NASA has called in extra help as it attempts to free Spirit...
-------------------- |
|
|
||
Lo-Fi Version | Time is now: 23rd April 2024 - 11:43 PM |
RULES AND GUIDELINES Please read the Forum Rules and Guidelines before posting. IMAGE COPYRIGHT |
OPINIONS AND MODERATION Opinions expressed on UnmannedSpaceflight.com are those of the individual posters and do not necessarily reflect the opinions of UnmannedSpaceflight.com or The Planetary Society. The all-volunteer UnmannedSpaceflight.com moderation team is wholly independent of The Planetary Society. The Planetary Society has no influence over decisions made by the UnmannedSpaceflight.com moderators. |
SUPPORT THE FORUM Unmannedspaceflight.com is funded by the Planetary Society. Please consider supporting our work and many other projects by donating to the Society or becoming a member. |