Groundbreaking Solar Mission Faces Chilly Death

iamlucky13 writes "Over 17 years ago, the Ulysses spacecraft was launched aboard the space shuttle Discovery for a unique NASA/ESA mission. While nearly all other probes travel along our solar system's ecliptic plane, Ulysses used a Jupiter gravity assist to swing 80 degrees out of plane, carrying it over the sun's poles for an unprecedented view. During a mission that lasted four times longer than planned, it has flown through the tails of several comets, helped pinpoint distant gamma-ray bursts, and provided data on the sun and its heliosphere from the better part of two solar cycles. Unfortunately, the natural reduction of power from its radioisotope thermal generator means it is now unable to even keep its attitude control fuel from freezing, and NASA has decided to formally conclude the mission on July 1."

Comments

I need better

[oldhack]

attitude control.

Re:I need better

[Anonymous Coward]

Troll or not, that was a gripping narrative.

Re:I need better

[Anonymous Coward]

Hahahahahahahhaahahahhaa!

solar power?

[Anonymous Coward]

They should have put solar panels on it.

Re:solar power?

[Anonymous Coward]

it does not provide thrust. for that you need to throw out some mass. or use HUGE solar sails.

Re:solar power?

[fr4nk]

The RTGs don't provide thrust either... as TFS states, it's used (among other things) to keep the hydrazine tanks for attitude control from freezing. Also, solar panels wouldn't help much, because it's orbit extends as far as Jupiter's (with the periapsis being a little outside Earth's orbit).

Re:solar power?

[Wandering Wombat]

It doesn't need to provide thrust. Read the article. They need energy to keep the fuel warm.

Re:solar power?

[inamorty]

No man, it's an attitude problem.

it is now unable to even keep its attitude control fuel from freezing Instead of chilling out, it should apply itself more.

Re:solar power?

[NathanBFH]

While this was certaintly true 17 years ago, it's interesting to note that we are now able to sufficiently power science craft with solar panels even as far as Jupiter. Check out Juno: http://en.wikipedia.org/wiki/Juno_(spacecraft)

Re:solar power?

[hubie]

"Sufficiently power," of course, depends on your mission goals as well. An RTG will give you consistent power for a long time, whereas the solar cells will have issues managing eclipses and long-term degradation from radiation exposure. A Voyager-like flyby would be better suited for an all-solar approach rather than a Galileo-type orbit (and eclipse) all the time in strong radiation belts. History has also shown that it is far from trivial to deploy large solar arrays, even when you have humans present, and the size of these arrays are huge.

A very nice summary of solar cell technology and future plans can be found over at the USRA site.

Re:solar power?

[RockDoctor]

An RTG will give you consistent power for a long time, whereas the solar cells will have issues managing eclipses and long-term degradation from radiation exposure.

The orbit of Ulysses goes from a perihelion of 1.34 AU, to an aphelion of 5.4 AU (period 6.2 years) (from a NASA position paper) ; that's a factor of 4.03 difference in heliocentric range and 16.24 in sunlight intensity through it's orbit. That's without any variations in cell efficiency at different temperatures, pointing issues, or long-term degradation.
Given that the orbit has an inclination of 80deg to the plane of the Earth's orbit (and thus 63-97deg to the orbits of the other planets), eclipses are unlikely to be a major problem.

Re:solar power?

[Anonymous Coward]

I was commenting not about Ulysses but the more general comment made that today we can "sufficiently power science craft with solar panels even as far as Jupiter."

Not really as bad as the blurb sounds

[the_humeister]

The mission lasted 4 times longer than was planned. Not too shabby (unless you compare to those Mars rovers that just keep going and going...). Sure beats having the mission end prematurely due to stupid things like not having enough fuel or computer errors.

Re:Not really as bad as the blurb sounds

[the_humeister]

Come to think of it, it's even lasted longer than those Mars rovers.

Re:Not really as bad as the blurb sounds

[Anonymous Coward]

Come to google it, it's even lasted longer than those Mars rovers fixed.

Re:Not really as bad as the blurb sounds

[Anonymous Coward]

http://en.wikipedia.org/wiki/Ulysses_(spacecraft)

"Originally, two spacecraft were to be built by NASA and ESA, as the International Solar Polar Mission. One would be sent over Jupiter, then under the Sun. The other would fly under Jupiter, then over the Sun. This would provide simultaneous coverage. Due to cutbacks, the US spacecraft was canceled in 1981. One spacecraft was designed, and the project recast as Ulysses, due to the indirect and untried flight path. NASA would provide the Radioisotope Thermoelectric Generator (RTG) and launch services, ESA would build the spacecraft assigned to Astrium GmbH, Friedrichshafen, Germany (formerly Dornier Systems)."

Craft itself was built by ESA and now it becomes spacejunk because of the ONLY part that was provided by NASA. Some isotopes were cut too maybe...

Re:Not really as bad as the blurb sounds

[Anonymous Coward]

Come to google it, it's even lasted longer than those Mars rovers fixed. HAHAHA!

But seriously, I think something floating about freely in space can survive more easily than something grinding around in dirt all day long. It's great that Ulysses lasted that long, but it's still not as astonishing as those Mars rovers, I'd think.

Re:Not really as bad as the blurb sounds

[petermgreen]

unless you compare to those Mars rovers that just keep going and going
looking at nasa's site there don't seem to have been any updates on the rovers for about a fortnight (prior to that the updates seem to have been approximately weekly), I wonder if that is a bad sign.

Re:Not really as bad as the blurb sounds

[chrish]

IIRC they're hibernating during the Martian winter; I seem to recall reading an article about the controllers moving one into a good spot so it wouldn't run completely down during the darker months. This being /., I'm too lazy to go google it for you.

Re:Not really as bad as the blurb sounds

[Anonymous Coward]

Don't worry. The rover team has generally been pretty forthcoming about problems they've faced, and even with the reduced staff, they still post notices of big news.

Not to mention, if you go to the raw images portion of the site, you'll see there's still pictures being sent back on a daily basis. Almost none from Spirit because of her low power budget, but plenty from Opportunity. The latter is still inside Victoria crater and trying to make her way through some soft sand to reach a small cliff on the edge of the crater that shows interesting layers.

So long Energizer Bunny

[dreamchaser]

those Mars rovers that just keep going and going

I am waiting for Energizer to ditch that obnoxious rabbit and license the Mars Rovers for their advertising.

Re:So long Energizer Bunny

[antdude]

Or have both. Energizer would win. :P

Re:So long Energizer Bunny

[ckaminski]

If you noticed, the rabbit's pink. The whole marketing program is a mind-numbingly awesome appeal to women to use Energizer batteries to power their vibrators.

Re:So long Energizer Bunny

[Anonymous Coward]

I wonder if aliens could collect enough high energy photons from their nuclear whessels to refill the RTGs?

These old probes are going to be worth a fortune a few hundred years from now.

Re:So long Energizer Bunny

[jc42]

Hmm ... I can see the ad slogan: It keeps going and going, so you'll keep coming and coming.

Maybe I oughta copyright the slogan before they try to use it (if they haven't already).

Re:So long Energizer Bunny

[Xyrus]

Wow...and I thought I spent too much time on slashdot.

~X~

Re:So long Energizer Bunny

[Anonymous Coward]

Except that would be reality. Energizer commercials typically show the rediculous, like plugging the pink bunny into a powergrid to power an entire city. :P

Not intentionally a troll, I don't have any preference one way or the other on battery brands, but it always amused me how Duracell commercials mention actual uses while Energizer always stuck to fiction.

Re:Refreshing summertime treat...

[Anonymous Coward]

Cry me an icy river

Am I the only one that...

[Anonymous Coward]

...gets a little choked up thinking about that poor abandoned craft out there floating to oblivion with no one to talk to it.

Ok, back to masculinity-land...

Re:Am I the only one that...

[Anonymous Coward]

Ok, back to masculinity-land... In a similar way to Charlton Heston landing on an Earth run by apes, you appear to have landed in Geek territory. And you have NO WAY BACK!

Re:Am I the only one that...

[sporkme]

It reminds me of when Sorourner was spotted.

The rover had circled back looking for its dying lander... very touching.

The Real Ulysses

[gihan_ripper]

As the Greek Geeks will know, the real (legendary) Ulysses (aka Odysseus) went on a ten-year odyssey returning home after the Trojan war. All assumed that Ulysses had died and his former wife was preyed upon by suitors seeking her hand in marriage.

To cut a long story short, Ulysses killed all the suitors when he got home and was especially cruel to a turncoat goatherd, Melanthius. Ulysses cut off his nose and ears, pulled out his genitals for dog food, then sliced off his hands and feet.

Let's home the satellite doesn't come back and find us messing about with the ISS.

Re:The Real Ulysses

[DNS-and-BIND]

So, Ulysses was a neocon, eh?

Re:The Real Ulysses

[Hektor_Troy]

Let's home the satellite doesn't come back and find us messing about with the ISS.THEY did it! *points to Bush, Cheney, Rumsfeld and Rize*

Re:The Real Ulysses

[nfk]

"the real (legendary) Ulysses"

Hmm, so this probe is actually the real Ulysses.

Re:The Real Ulysses

[the_other_chewey]

As the Greek Geeks will know, the real (legendary) Ulysses (aka Odysseus) went on a ten-year odyssey returning home after the Trojan war.

Yeah, because he sucked at navigation.
Additionally, he was an idiot: All the things the gods warned him not to do because
they would turn out to be bad, he did - and they went bad. I never understood why this
moron is considered a hero, and what the gods liked about the guy.

Re:The Real Ulysses

[flyingfsck]

No, I read the Odyssey - it is on my book shelf, together with many other classics. Odysseus did give the goat herd a sucker punch that cracked a bone in his face (for good reason), and the rest of what you said is simply not true. The suitors attacked Odysseus and he fought them off successfully. I suggest that you read the book. It is in every library.

Re:The Real Ulysses

[Anonymous Coward]

So, Ulysses was a neocon, eh? See, that's just a stupid thing to say.

Re:The Real Ulysses

[gihan_ripper]

Well, I don't know what version of the Odyssey you have, but I can quote from the Samuel Butler translation of Book XXII at the Project Gutenberg

As for Melanthius, they took him through the cloister into the inner court. There they cut off his nose and his ears; they drew out his vitals and gave them to the dogs raw, and then in their fury they cut off his hands and his feet.

Here 'they' refers to Ulysses, Telemachus, and some cronies, as you'll find if you read further up the page. I can only imagine you have a censored version that took out the gory bits.

Re:The Real Ulysses

[Anonymous Coward]

Just goes to show that despite the odds and what common sense might tell you, stupid endures.

Re:The Real Ulysses

[andrikos]

Just goes to show that despite the *Gods* and what common sense might tell you, stupid endures.

Re:The Real Ulysses

[Anonymous Coward]

Yeah, because he sucked at navigation.

I don't think navigation skills help all that much when Poseidon is angry at you.

Additionally, he was an idiot: All the things the gods warned him not to do because
they would turn out to be bad, he did - and they went bad. I never understood why this
moron is considered a hero, and what the gods liked about the guy.

It's been a while since I've read the Odyssey, but I don't remember it quite like that. After the battle of Troy, Poseidon got angry, and Odysseus didn't offer a sacrifice to the gods, so he wasn't sufficiently humble. The other gods offered him help in an attempt to teach him humility (which he did learn and proceeded to offer sacrifices to the gods after every victory on his way back to Ithaca). Poseidon just wanted him dead.

I do remember his crew doing things that made the situation worse, like opening the bag of winds.

Re:The Real Ulysses

[Tablizer]

Ulysses cut off his nose and ears, pulled out his genitals for dog food, then sliced off his hands and feet.

I find it humorous how ancient writers went into great detail about how torture was done. It makes them sound obsessed with violence. I wonder if that was the style, or whether its just that such info tends to survive longer?

In 2500 years, will people be reading the same kinds of things about Guantanamo Bay and CIA water-boarding and think the same thing?

Re:The Real Ulysses

[Petrushka]

Odysseus did give the goat herd a sucker punch that cracked a bone in his face (for good reason), and the rest of what you said is simply not true

You're thinking of Iros, the beggar, in book 18 (though we're told that he too was going to get the same punishment: 18.86-87). The punishment of Melanthios, the goatherd, is in book 22 (22.474-477). If it's any comfort the OP isn't wholly correct either, as it's not Odysseus himself who does the dismembering; the context makes it sound like it was his son, Telemachos, assisted by the "good" herdsmen. It's the bit just after Telemachos hangs a bunch of maidservants for having sex with the suitors.

Re:The Real Ulysses

[Petrushka]

Yeah, because he sucked at navigation. Additionally, he was an idiot: All the things the gods warned him not to do because they would turn out to be bad, he did - and they went bad.

Not a single statement there accurately reflects the Odyssey. The actual story, as opposed to the one you've made up, relates that:

1. he took ten years because his men continually disobeyed his orders -- that's made clear in the first few lines --;
2. he shacked up with Circe for a year (voluntarily);
3. after he washed up on Calypso's island she basically held him prisoner for seven years. The story also relates how
4. any time a god told him to do something, he did exactly that; and
5. he is repeatedly described as having practically divine intelligence, and this is borne out by the various schemes he devises in the story. Even Athena compliments him on his deviousness.

The reason you do not understand his appeal to the ancient Greeks is because your memory of the story bears little resemblance to the actual story.

Re:The Real Ulysses

[Taatelipalmu]

So are we expecting the little tin can to come home and tell us about one-eyed aliens from a planet far away?

Re:The Real Ulysses

[Anonymous Coward]

V-GER?

Re:The Real Ulysses

[dyamkovoy]

I find it humorous how ancient writers went into great detail about how torture was done. Thy weren't ancient writers, they were ancient storytellers. These stories were passed by word of mouth first, and the gory details tend to be the ones that stick in your memory and are easiest to retell.

Bad Boy Probe

[timbudtwo]

They must be retiring it because of its serious attitude problem. It is a teenager after all.

Re:It can't die, it wasn't alive

[maxume]

Which fallacy is linking to fallacies on wikipedia?

Re:It can't die, it wasn't alive

[ricebowl]

Using animate metaphors for inanimate objects is the Pathetic Fallacy.

Does it offend you that much? Really? I'm not sure of the exact terms, but if the metaphor helps commmunication, without confusing people, then what's the harm?

attitude control

[Anonymous Coward]

it is now unable to even keep its attitude control fuel from freezing
You're fired!

Re:It can't die, it wasn't alive

[R2.0]

That would be Appeal to Authority.

http://en.wikipedia.org/wiki/Appeal_to_authority

Re:It can't die, it wasn't alive

[owlnation]

Is that a fallacy x fallacy, or a fallacy raised to the power of fallacy?

The latter, I think?

I'd send it into the sun for one last splash

[crovira]

If the fuel's going to freeze forever after this orbit, I'd send it into the sun with all instruments lit up and see what it can record on the way down.

Re:I'd send it into the sun for one last splash

[endlessoul]

The mods may have found this funny, but I find this interesting. Is it possible to modify the trajectory? Is it simply too far away to get to the sun? If the fuel already too frozen to be utilized?

If it's going to be an orbiting piece of frozen metal, we may as well send it to a fiery and possibly information gathering demise.

Re:I'd send it into the sun for one last splash

[Anonymous Coward]

I'd expect getting it to hit the sun anytime soon, would be a large delta-v maneuver, which it probably can't make anyway.

Re:I'd send it into the sun for one last splash

[PMBjornerud]

"Attitude control" means the thrusters to change its orientation, as opposed to changing the course. You could likely make the probe spin real fast. Not sure if that would give you any more exciting data, though.

I think you can safely assume the engineers on the project have gone through the possible options.

Re:I'd send it into the sun for one last splash

[mortonda]

since it used a gravity assist to get into this orbit, I highly doubt it can in any way adjust its orbit enough to make it useful, unless another planet happens to stumble by... and since it intersects the orbital plane only twice per orbit, that's pretty bad odds too.

Oh it will probably get to the sun eventually, if it doesn't run into something else, but it will be dead long before.

Re:I'd send it into the sun for one last splash

[cyclone96]

To change the orbit to intersect the sun, a tremendous amount of velocity would need to be removed from the current orbit. It would take more propellant to get it to the sun than it took to launch it from the earth in the first place.

It's actually quite difficult to "hit the sun", the Messenger spacecraft will need to do one earth, two Venus, and 3 Mercury flybys over 7 years to "slow down" enough so that it can finally brake into orbit around Mercury with it's insertion motor.

Re:I'd send it into the sun for one last splash

[u38cg]

Absolutely no way, is the short answer.

Long answer - in order to get it into the sun, you have to reduce its rotational velocity from numerous miles per second down to zero. You'll remember your 0.5mv^2 - that's how much calorific energy has to be in those tanks to achieve that. Also, at those kind of distances, almost any kind of rotational velocity will be enough to achieve orbit - meaning the damn thing will almost certainly miss and turn into a rather odd comet, which will no doubt baffle our ancestors.

Re:I'd send it into the sun for one last splash

[ozbird]

It doesn't carry anywhere near enough fuel for a sun dive.

Most of the energy to get into its current orbit came from its PAM-S and IUS solid rocket boosters, with Jupiter kicking it out of the ecliptic. Until New Horizons was launched recently, Ulysses was the fastest ever artificially-accelerated object - that's how much energy we're talking about. Ulysses started out with 33.5kg of hydrazine maneuvering fuel, and was down to 8.4kg in May 2002. In a nutshell, you could use up all of the remaining fuel and not get anywhere near the Sun (perhelion distance is around 1 AU.)

Re:I'd send it into the sun for one last splash

[RealGrouchy]

Yes, we could paint it black and have a really loud concert with terrible, terrible music!

"Ship! Sun! Wham bang!"

- RG>

Re:I'd send it into the sun for one last splash

[gihan_ripper]

which will no doubt baffle our ancestors.

so that would be our time-travelling ancestors?

Re:I'd send it into the sun for one last splash

[metamechanical]

It'll only baffle our ancestors if it performs the time-travel slingshot maneuver while going backwards around the sun.

Re:I'd send it into the sun for one last splash

[Anonymous Coward]

... which will no doubt baffle our ancestors. I find the idea of our ancestors being baffled by a modern day artificial satellite baffling. But maybe your ancestors have a time machine.

Re:I'd send it into the sun for one last splash

[denzacar]

It does not work without Spock's precise calculations.

You have to be very careful with time traveling solar-slingshots.
Forget a decimal point or two and it might end up as another Tunguska event...

Heeey...

Re:I'd send it into the sun for one last splash

[Fred_A]

Not sure if that would give you any more exciting data, though. Dizzying data then, maybe ?

Re:I'd send it into the sun for one last splash

[CartoonFan]

In order for our ancestors to travel through time, wouldn't we have to send a time machine back to the past?

Re:I'd send it into the sun for one last splash

[Anonymous Coward]

Well yes, but it's a forgone conclusion that time travel will-is-was(will have been, is being, was going to be, etc) invented simultaneously throughout history. Don't worry, it all fits together like a jig-saw puzzle.

Re:I'd send it into the sun for one last splash

[X3J11]

which will no doubt baffle our ancestors.

so that would be our time-travelling ancestors?

Unless it swings around the sun, achieves a speed multiple times that of light, and travels back in time itself.

At least it won't have to save any whales.

Re:I'd send it into the sun for one last splash

[Cecil]

As with most problems in orbital mechanics, the problem is not the distance, but the speed it is travelling to maintain its orbit. In order to crash into the sun, it needs to reduce its speed from a very high number that maintains its orbit, to a very low number that allows it to crash into the sun without gaining so much speed due to gravity that it simply ends up in a newer, more elliptical orbit.

I am certain that it doesn't have enough fuel onboard to change its speed by even a fraction of the required amount. Keep in mind that simply by merit of launching from Earth, it started off with a substantial amount of orbital velocity already (namely, Earth's). To slow it right down to near zero would take a mind-boggling amount of fuel...

Re:I'd send it into the sun for one last splash

[Sobrique]

On the plus side, at least we now know what happened to the dinosaurs.

NASA-style journalism

[TrueJim]

You can always tell when a story is based on a NASA press release. If the spacecraft exceeded its mission expectations, it's a "NASA spacecraft." But if it failed, it's a "Lockheed-built spacecraft" (or whichever contractor they decide to blame).

For a change it would be nice to see NASA give kudos to whatever contractor built the successful spacecraft for them.

Re:NASA-style journalism

[eggman9713]

It's just like they said in the Dilbert TV series, "credit travels up, blame travels down."

Re:NASA-style journalism

[Anonymous Coward]

Except in this case it isn't even a NASA spacecraft, sure NASA lauched it and did lots of the science equipment, but the spacecraft itself was built by the ESA.

Re:NASA-style journalism

[barzok]

You mean "shit rolls downhill."

Re:NASA-style journalism

[Anonymous Coward]

I have found it much more accurate if you replace "NASA" with "JPL." When the spacecraft is successful at Mars (or wherever), it is the big press ado at JPL with their logo everywhere. When it fails spectacularly, it is the NASA press room talking about how JPL will head the review board to understand why the NASA mission was a failure.

Re:NASA-style journalism

[j-b0y]

Or, more accurately, built by Dornier under contract to ESA.

Re:NASA-style journalism

[Anonymous Coward]

This spacecraft was designed and built by the ESA. NASA provided the launch vehicle and the RTG.

http://www.esa.int/esaSC/SEMTDTUG3HF_index_0.html
http://www.jpl.nasa.gov/news/news.cfm?release=2008-106

Re:NASA-style journalism

[Anonymous Coward]

http://en.wikipedia.org/wiki/Ulysses_(spacecraft)

"Originally, two spacecraft were to be built by NASA and ESA, as the International Solar Polar Mission. One would be sent over Jupiter, then under the Sun. The other would fly under Jupiter, then over the Sun. This would provide simultaneous coverage. Due to cutbacks, the US spacecraft was canceled in 1981. One spacecraft was designed, and the project recast as Ulysses, due to the indirect and untried flight path. NASA would provide the Radioisotope Thermoelectric Generator (RTG) and launch services, ESA would build the spacecraft assigned to Astrium GmbH, Friedrichshafen, Germany (formerly Dornier Systems)."

Craft itself was built by ESA and now it becomes spacejunk because the ONLY part provided by NASA. Nice.

Re:NASA-style journalism

[GrayNimic]

Where was it referred to as a "NASA spacecraft"? I looked over the summary and the press release, and it was always referred to as the "Ulysses spacecraft". The closest phrase was "The spacecraft was provided by ESA.", or references to the NASA/ESA "mission" or "project" not "spacecraft".

It's an ESA spacecraft (built by "Dornier Systems, Germany (now Astrium)"), with a mix of US & European instruments, launched by NASA (shuttle + Boeing + McDonnell Douglas), operated from NASA (JPL) by a joint NASA/ESA team.

Most NASA press releases I've seen tend to mention the manufacturer, good or bad, if it's a US company. When it's European, mentions of the contractor are a lot rarer, though Italy seems to be good at getting its name in there (probably because the US has had some construction contracts with them, outside of their ESA agreements). For example, looking over the Mars Polar Lander news release archive, the attributions to NASA vs contractors seem similar to MER and Phoenix press releases.

Re:NASA-style journalism

[GammaRay Rob]

You can always tell when a story is based on a NASA press release. If the spacecraft exceeded its mission expectations, it's a "NASA spacecraft." But if it failed, it's a "Lockheed-built spacecraft" (or whichever contractor they decide to blame).

For a change it would be nice to see NASA give kudos to whatever contractor built the successful spacecraft for them. Umm. some of NASA's spacecraft are delivered to the agency in-orbit, after checkout. Until then, they remain the property of the contractor. This is the case with GLAST, which was just launched, but will remain with General Dynamics until L+60 days.

Control moment gyros

[heroine]

Control moment gyros would have failed after 1 year & needed 17 servicing missions + 1 protest on capitol hill. U can't beat rocket fuel.

Re:It can't die, it wasn't alive

[maxume]

I think it divides, so that you end up multiplying your argument by the identity, but people wonder why you stuck in that extra step.

Why not closer orbit?

[Anonymous Coward]

Or crash it into the sun and take data as long as you can?

Re:Why not closer orbit?

[Anonymous Coward]

Fuel is the simple answer. It would have taken much more fuel, which means a heavier, more expensive spacecraft (one beyond the shuttle's launch capabilities...and in fact beyond that of any launch vehicle currently in service). The amount of fuel remaining would barely make a dent at bringing it closer to the sun.

As is, it was launched out to Jupiter, which was necessary to get the delta-v to swing it into the 80 degree solar orbit. They also took advantage of that to swing it back inward nearly to the radius of earth's orbit, but there still wasn't enough fuel to circularize the orbit. As a result, it is in an elliptical orbit as close as 1.3 AU (about 1/3 of the way to Mars) and 5 AU (roughly as far as Jupiter). The problem actually comes to a head now because it's on the outbound leg of its orbit...heading out towards Jupiter. As a result, heat from the sun the sun is minimal and it relies almost entirely on the electrical heaters and RTG waste heat to keep the fuel from freezing.

Re:It can't die, it wasn't alive

[oldhack]

Shut up you ricebowl.

A gripping narrative . . .

[Anonymous Coward]

with just a hint of deja vu.

RTG lifetime

[Richard_J_N]

Quite a few spacecraft seem to run out of power due to failing RTGs. Admittedly, these are the ones that already perform *much* better than their design-lifetime (so Kudos to the designers), but why not just equip them with a little more of the relevant isotope? After all, the mass required is really quite small, and when the missions succeed, it would be great to have a 50+ year lifespan. Is there a good reason why the amount of isotope is limited, or is it just that nobody ever expected the craft to function so well and for so long?

Re:RTG lifetime

[Waffle Iron]

but why not just equip them with a little more of the relevant isotope?

Because then you'd need a bigger heavier radiator to keep the RTG from melting early in the mission.

Re:RTG lifetime

[32771]

This is a silly comment.

This kind of knowledge must come in handy when designing your nuclear powered waffle iron.

Re:RTG lifetime

[Richard_J_N]

I hadn't thought of that. I assumed it was just a case of adding another 1kg or so of whatever isotope is used. But actually, if you doubled the mass of RTG, and used an isotope with a longer half-life, you wouldn't need a larger radiator.

Re:RTG lifetime

[deglr6328]

Because the problem of failing RTGs is not due to radioactive decay. RTGs use Pu-238 which has a half life of 88 years. It's just as hot as when it launched. The problem is dopant migration in the semiconductor heterojunctiontions (peltier junctions) of the part that creates the electricity. They degrade over time and put out less electricity for the same reason an LED fails gradually over time slowly emitting less and less light for the same amount of energy put in.

Re:RTG lifetime

[deblau]

Is there a good reason why the amount of isotope is limited, or is it just that nobody ever expected the craft to function so well and for so long?

From Wikipedia, the best fuel to use is Pu-238 (as in, zomg Plutonium, atomic bombs). Read the article for the technical explanation.

Re:RTG lifetime

[dwye]

> From Wikipedia, the best fuel to use is Pu-238 (as in, zomg Plutonium, atomic bombs)

No, fission uses Pu-239, not 238. Alas, I only know how to produce Pu-239 (oblig. bwah, hah, hah!) or I would write how different they are.

Re:RTG lifetime

[Free the Cowards]

And if wishes were horses we'd all be eating steak.

It's easy to say things like, just double the mass of the RTG and just use an isotope with a longer half-life. It's much harder to actually find an isotope with that longer half life (the isotopes which have an appropriate half life and can be synthesized in the appropriate quantities, and to actually change the design of the spacecraft to accommodate the extra mass.

It's an extremely complex engineering problem with a lot of tradeoffs involved. If they could get more life "for free" then they certainly would, but unfortunately it's far from free when you get into the details.

Re:RTG lifetime

[Thomas Henden]

How could Voyager 1 and Voyager 2 last so much longer then? They are still transmitting after 30+ years, while Ulysses lasted 17 years, and was created later than the Voyager spacecrafts so that the RTG-technology assumingly must have gotten more advanced.

Re:RTG lifetime

[Anonymous Coward]

Which is why NASA is now researching using a Sterling engine rather than RTG. Very cool tech.

Mission's over?

[192939495969798999]

I think the mission shouldn't officially be over unless useful data stops coming back, and I would assume a probe even just floating around aimlessly might still broadcast back some kinda data.

Re:Mission's over?

[Anonymous Coward]

Did you see that big dish on it? "Floating around aimlessly" = not pointing at the earth. You can't transmit to the earth without attitude control.

Re:Mission's over?

[Anonymous Coward]

The only problem with maintaining the mission is that the Deep Space Network has a limited capacity for data transfer, if the equipment is utilized to monitor the Ulysses, it can't receive data on other, more useful probes. My guess is that NASA, in order to allocate resources for missions still streaming huge amounts of valuable data, it's better to cut this one loose and focus on the others.

Re:Mission's over?

[GrayNimic]

That's probably why it's expected to "end on or about July 1", rather than a hard-and-fast date.

I remember

[32771]

My astronomy teacher told us about it when I was still in school. Must have been around '92.

She taught astronomy at the local observatory+planetarium. Her name was the German word for Fox so she had her own constellation = Vulpecula.

Idiotically our local Christian democrat government canceled astronomy lessons in 2007. This used to be a required course for the 10th grade in Eastern Germany since 1959. (Its probably the money)

Anyway, old satellites never die, and sometimes their orbits won't even decay.

Re:It can't die, it wasn't alive

[cp.tar]

Which fallacy is linking to fallacies on wikipedia?

Ad Wikipediam?

Re:It can't die, it wasn't alive

[risk one]

It's not a fallacy unless you're using it as an argument. This is just metaphorical language.

Don't know how to mod this

[Fross]

It's either very informed indeed, or complete rubbish. I mean, "heterojunctiontions"?

Well done, I'm completely stumped.

Re:Don't know how to mod this

[Pathwalker]

What term would you use for the ions in the junction of two different metals than "heterojunction ions"?

Seems perfectly clear to me.

Re:Don't know how to mod this

[jschen]

Definitely informative. Slowly failing RTG's due to degradation of the thermocouples that convert heat into electricity is a likely cause of the eventual end of the Voyager missions. More info at http://voyager.jpl.nasa.gov/spacecraft/spacecraftlife.html

Re:Don't know how to mod this

[deglr6328]

typo!

Re:Don't know how to mod this

[Sapphon]

And that, ladies and gentlemen, is the difference between 5-digit and 3-digit UID Slashdotters: the latter considers "heterojunction ions" to be a perfectly self-explantory term.

That the OP has 6-digit UID is probably just a trick: I'm betting it's the secondary account of a 2-digit user used to catch out 4- and 5-digit newbies.

It's sort of like what Twitter does, but, you know.. with facts.

Oh and...

[denzacar]

Warp speed...

It needs to be going towards the Sun at warp speed.

what about....

[ztcamper]

keeping active components of RTG at a distance and as they gradually decay bringing them closer together. Additionally a gradually increasing concentration of neutron reflective materials can be added as components get closer together. This would slow decay of radioactive materials and reduce temperature in the beginning potentially reducing size of radiators. This should also increase period of time for which RTG can be active by using variably reflective neutron mirrors.

Groundbreaking Solar Mission Faces Chilly Death

[Anonymous Coward]

and NASA has decided to formally conclude the mission on July 1."

And at that point Nasa will change the name from Ulysses to Useless

Go get it.

[Sun.Jedi]

Since it's built so well as to exceed expectations x4, why doesn't someone go get it, and bring it back for an refit/upgrade and a new mission?

Worst case would be that it just looks damn good on someones front lawn.

Re:Go get it.

[Zosden]

Only because it would take forever to get it and then returning it would be a big ??? Also do you even know where it is located NASA is having problems getting to the moon let alone correct me if I'm wrong (I'm on my iPhone) but isnt it past Pluto.

Congratulations, NASA!

[drolli]

This is great! The systems worked well up to the point until a fundamental limit, which could not be overcome, hits. The fact that they had overdimensioned it already that the system worked four times longer than planned shows that the right design decisions have been made.

Re:yeah but

[Tubal-Cain]

Ulysses was launched on October 6, 1990. Linux was announced August 25, 1991. (hurray for wikipedia!) Draw your own conclusions.

Sweet Lord, Star Trek Writers

[patio11]

>>
dopant migration in the semiconductor heterojunctiontions
>>

Hire this guy. Now. He makes your "tachyon pulses" look like the deranged ramblings of a man-child.

Here there's more

[Dusty]

The European Space Agency had a press conference about the end of Ulysses on Thursday. Brief note and audio feed. Longer press release.

The video the Ulysses Legacy has a great summary of the mission, and of the problems it now faces.

heros

[reiisi]

Actually, this is the archetype of a hero in western literature. Has something to do with how even religious people tend to view some of their Gods' demands.

(As a religious person, I have spent my time complaining to God, myself.)

One of the differences between religions is how much help the believer expects, and of what kind. This is definitely one of the concepts explored in Ulysses.

Rover

[professorfalcon]

The mainstream press will inevitably call this a rover.

Schoolhouse Rock

[Nirvelli]

Conjunction junction, what's your function?

Re:It can't die, it wasn't alive

[Anonymous Coward]

Insightful and ironic - funny!

Re:It can't die, it wasn't alive

[nahdude812]

It's cute, but it's not actually accurate. Appeal to authority only applies if an arguer uses their own authority as the argument. From your own link it is, "a type of argument in logic consisting on basing the truth value of an assertion on the authority, knowledge, expertise, or position of the person asserting it," (emphasis mine).

It would be an A2A if a Wikipedia article claimed it doesn't need citations because of it being a Wikipedia article, or only cited other Wikipedia articles which themselves had no citations or only cited yet other Wikipedia articles.

Short answer

[DerekLyons]

Sounds like a wonderful idea for Dr Who or Star Trek technobabble - but RTG's work via radioactive decay, not via fission. These ideas won't work in the real world.