MSL reasons for delay |
MSL reasons for delay |
Mar 4 2009, 03:33 PM
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#1
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Senior Member Group: Members Posts: 2547 Joined: 13-September 05 Member No.: 497 |
I wanted to make sure that everyone interested sees Adrian Brown's articles at http://www.thespacereview.com/article/1319/1 and http://www.thespacereview.com/article/1318/1 about the technical and budgetary problems with MSL that led to the launch slip. While I can't claim to be privy to the budgetary and political issues at the mission level, the technical discussion seems like a fair summary of the situation as I understand it, at least as good a one as can be gathered from public sources.
People in other forums have complained about errors in these articles, but without giving specific examples or providing any factual basis for their objections. I don't find that very useful. If there are real flaws in this account, I'd be quite interested to know what they are. p.s. I guess we need to change the name of this subforum. -------------------- Disclaimer: This post is based on public information only. Any opinions are my own.
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Jul 13 2009, 08:22 PM
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#2
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Member Group: Members Posts: 279 Joined: 19-August 07 Member No.: 3299 |
dtolman,
I think that this might be a leak news from news media since it has no further detail information about the reason. If NASA informs this, I hope it would be well covered and explained. About this I have many questions and I am not able to know what is the real reason. It would be to too early to get well acquainted. I think that NASA must know it perfectly whether if it is or not necessary after studying their cons and pros. The main electrical energy would be based of nuclear and the solar ones would be interpreted as an supplemental and not as critical energy. On the other hand, it would to be insufficient to supply an extra needed energy due to a new requirements, or present instruments that might need an additional not planned electrical energy needs. An additional battery capacity would be the most sounding acceptable but up to here, it is not worth to further discuss without knowing their cons/pros. |
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Jul 14 2009, 01:25 PM
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#3
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Member Group: Members Posts: 129 Joined: 20-April 05 Member No.: 291 |
SpaceListener,
The main source of this seems to be an article in Nature - http://www.nature.com/news/2009/090710/ful...s.2009.664.html. I didn't see this in the summary, so it probably bears repeating. From the article (concerning cost and power overruns respectively): QUOTE The cause of the latest overrun is problems with motors, gearboxes and avionics controls. After switching from a dry to a wet lubricant, engineers have had trouble verifying the reliability of motors for the rover's robotic arm. Moreover, McCuistion says, a new snag was recently discovered: some of the premier instruments — the Sample Analysis at Mars or SAM instrument set — will suck twice as much power as was expected, and that means the rover needs to carry bigger batteries. I'm assuming here that the "batteries" are the RTGs. not the L-I kind...is there sufficient P-238 unclaimed to supply larger batteries? as of early 2008, I read reports in the media that the unclaimed supply in the system was measurable counting on one hand (in kilograms). Or maybe they can find a clever way to shutdown systems to allow the SAM to run on the existing power supply. Hopefully the latter is a viable solution. I doubt they can add kilograms of battery, without cutting weight from somewhere else... |
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Jul 14 2009, 01:53 PM
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#4
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Senior Member Group: Members Posts: 2547 Joined: 13-September 05 Member No.: 497 |
I'm assuming here that the "batteries" are the RTGs. not the L-I kind...I doubt they can add kilograms of battery, without cutting weight from somewhere else... No, they are talking about the secondary batteries (I forget if they are using Li-ion or something else.) The RTG doesn't provide enough peak power to run the systems directly, so it has to be used to trickle-charge the batteries. As for mass, I expect that they have enough mass margin to add batteries if there is no operational workaround. At least our cameras are coming in well under on both mass and power relative to predictions (not that we were very big either way.) And for JPL bashers, note that SAM is provided by GSFC, not JPL. -------------------- Disclaimer: This post is based on public information only. Any opinions are my own.
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Jul 14 2009, 02:17 PM
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#5
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Member Group: Members Posts: 129 Joined: 20-April 05 Member No.: 291 |
mcaplinger - thanks for the clarification. It can get confusing trying to parse power supply issues when everything ends up getting called "a battery" in the media.
Also - if anyone is interested - there is related information in this presentation to the NASA Advisory Committee (courtesy naswatch/spaceref): http://images.spaceref.com/news/2009/PSS.Jun.09.Mars.pdf The slide of interest from the presentation: QUOTE • Rover power system design does not meet present mission requirements, requiring additional battery capacity, and possibly solar array – Increased energy requirements to keep actuators above safe operating temperature – Almost double energy requirement to operate/conduct SAM instrument science/sample analysis scenarios • The SAM instrument has not completed its environmental qualification program, and the wide range pump has not demonstrated life qualification (hours of operation and start/stop) requirements. The bullets above make it sound more serious (at least to me), than the Nature summary. Does anyone have any idea if the problem is that they can't run the SAM with other operations running, or if they can't even draw enough power to run the SAM even by itself? |
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Jul 14 2009, 02:26 PM
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#6
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Senior Member Group: Members Posts: 2547 Joined: 13-September 05 Member No.: 497 |
Does anyone have any idea if the problem is that they can't run the SAM with other operations running, or if they can't even draw enough power to run the SAM even by itself? Almost certainly the first one. These are total energy problems, not instantaneous power problems. As such there are most likely operational workarounds, though they may not be very attractive. -------------------- Disclaimer: This post is based on public information only. Any opinions are my own.
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