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What's Up With Ulysses?, alive? dead? cancelled soon?
remcook
post Jan 29 2007, 04:38 PM
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ah I see now.
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ustrax
post Feb 7 2007, 01:47 PM
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There goes Ulysses...again... smile.gif

I really enjoy Dr. Marsden' updates:

"It's amazing to think that a satellite that was designed in the mid-1970's
and built in the early 1980's is still operating perfectly in 2007!"


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Guest_AlexBlackwell_*
post Feb 7 2007, 05:34 PM
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Ulysses scores a hat-trick
ESA
7 February 2007
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nprev
post Feb 11 2007, 08:17 PM
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I agree with ustrax; the longevity of this spacecraft (and others) is astounding. These are arguably among the most complex devices ever built, yet without hands-on maintenance, periodic overhauls, etc., they just keep going. Wonder if the space agencies might be interested in building a few cars on the side... cool.gif

All that aside, how much longer can Ulysses keep going given this new power conservation strategy? Also, is there any possibility that it will re-encounter Jupiter at some point?


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Paolo
post Feb 11 2007, 08:44 PM
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QUOTE (nprev @ Feb 11 2007, 09:17 PM) *
Also, is there any possibility that it will re-encounter Jupiter at some point?


Back when I was in university, a dozen of years ago I played with simulating Ulysses' orbit. In that occasion I "discovered" the second flyby of 2003.
Ulysses crosses Jupiter's orbit every 6.5 years, and approaches it every 13 years, but IIRC, the encounter distance is increasing and there will be no more flybys during all of the 21st century.


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Jeff7
post Feb 13 2007, 03:36 AM
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QUOTE (nprev @ Feb 11 2007, 03:17 PM) *
I agree with ustrax; the longevity of this spacecraft (and others) is astounding. These are arguably among the most complex devices ever built, yet without hands-on maintenance, periodic overhauls, etc., they just keep going. Wonder if the space agencies might be interested in building a few cars on the side... cool.gif

All that aside, how much longer can Ulysses keep going given this new power conservation strategy? Also, is there any possibility that it will re-encounter Jupiter at some point?

I figure that they've probably got some pretty tight tolerances on these components. What I'm learning in my engineering classes is that tight tolerances are expensive. According to my Product Design professor, a Professional Engineer, they probably could design cars that would come with lifetime warranties. But they might cost $500,000 each, or more. Parts would need to be made out of more corrosion-resistant materials (more expensive), more parts wouldn't pass inspection because they'd be out of tolerance (higher manufacturing costs, and more time required to manufacture, which also = higher costs), and you might need more highly skilled engineers and machinists to properly design and construct this super-accurate car.

If they manufactured the MER's to the tolerances you probably find in the consumer auto industry, the rovers might never have left their landers.

Something else to consider - car manufacturers want you to buy a new car every so often. A car that might fail eventually increases your chance of buying again. NASA and JPL don't expect a lot of that sort of return business for most of their designs.
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centsworth_II
post Feb 13 2007, 03:56 AM
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QUOTE (Jeff7 @ Feb 12 2007, 10:36 PM) *
A car that might fail eventually increases your chance of buying again.


But not from that manufacturer. I think car failure is due mostly to keeping costs down,
not planned shoddy workmanship. How much would a car built to NASA specifications cost?
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Littlebit
post Feb 20 2007, 02:54 PM
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Ulysses Update:

http://www.spaceref.com/news/viewpr.nl.html?pid=21934
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Jeff7
post Feb 21 2007, 04:06 AM
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QUOTE (centsworth_II @ Feb 12 2007, 10:56 PM) *
But not from that manufacturer. I think car failure is due mostly to keeping costs down,
not planned shoddy workmanship. How much would a car built to NASA specifications cost?

It depends how long it lasted, and it depends on the person. I doesn't have to last long. Just long enough. If it was long enough, the person may rather stay with a brand whose quirks and issues they know, rather than risk venturing into the unknown, buying something different that might be much worse.
And maybe it's not planned, but the engineers making it have to know what's going to happen. Heck, one of the equations I've learned has "reliability factor" built into it. What reliability do you want? 50%? 90%? 99.9%? Different percentages have different numbers (1 for 50%, .75 for 99.9%) that go into determining endurance strengths and allowable stresses to give the certain reliability rating.
I guess it's not planned so much as it is a side effect.

How much would a car built to NASA spec cost? See the post you quoted me out of. wink.gif


It'll be interesting to see how much longer it'll last. They seem to have a fair level of confidence in it:
"The definitive proof will come when Ulysses measures the temperature of the north polar coronal during the next 15 months."
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dvandorn
post Feb 21 2007, 03:43 PM
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This is the old argument they went through when they were designing the Apollo system. They asked themselves, how much would it cost to develop a system that would have a 100% reliability rating, that could never fail and never, ever endanger the lives of any of the crews.

They decided it would cost more than the entire American gross national product from then to their deadline (the "end of the decade") to accomplish that, and it would likely result in a first manned lunar landing sometime around 1980.

They also figured they could develop Apollo for about five billion dollars if they were willing to lose about half of the crews they launched.

They settled on having a 90% chance of completing any given mission, and a 99% chance of getting any given crew back alive. That determination *alone* set the cost of the program at about $25 billion in 1960s dollars.

So, yes, you can pursue perfection. Just understand that, first, you'll never achieve it, and second, that you'll spend an *awful* lot of time and money trying to get there.

The better is the mortal enemy of the good enough...

-the other Doug


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David
post Feb 22 2007, 02:19 AM
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QUOTE (dvandorn @ Feb 21 2007, 03:43 PM) *
They settled on having a 90% chance of completing any given mission, and a 99% chance of getting any given crew back alive.


Which are remarkably accurate estimates: they lost one mission out of 11 and 0 astronauts out of 33 (though they came pretty close).
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ustrax
post Feb 22 2008, 02:56 PM
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We'll miss you... sad.gif


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djellison
post Feb 22 2008, 03:37 PM
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Well - there's a lot of science to be had from the archives, and while it's always sad to see a spacecraft go, it's always a bonus to get some DSN time back.

Doug
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ilbasso
post Feb 22 2008, 04:23 PM
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QUOTE (dvandorn @ Feb 21 2007, 10:43 AM) *
...and a 99% chance of getting any given crew back alive.


I can't remember who said it, but someone once commented that all the safety features of modern cars - multiple airbags, seatbelts, etc. - actually cause more crashes, with people driving less safely because they assume they'll survive an impact. The person said, "Imagine how much more safely we would drive if our cars had foot-long spikes extending from the steering column and ending just in front of our chests. You wouldn't DARE make a stupid move or tailgate someone!" Think how much cheaper that would make our cars - a spike is a lot cheaper than an airbag!


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stevesliva
post Feb 22 2008, 06:07 PM
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You know, for all the flack that ESA's press folks get, I have to say that their framing of this story is pretty apt. Usually this sort of thing ends up reported in the press as "BILLION EURO SPACECRAFT MALFUNCTION" not http://news.google.com/news?hl=en&ned=...tnG=Search+News
"End of the odyssey for brave space probe Ulysses"
"Ulysses mission coming to a natural end"
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