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.

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?

[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.

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

[Anonymous Coward]

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

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

[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

[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).

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...

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

[nfk]

"the real (legendary) Ulysses"

Hmm, so this probe is actually the real Ulysses.

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

[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]

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.

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

[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

[gihan_ripper]

which will no doubt baffle our ancestors.

so that would be our time-travelling ancestors?

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."

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

[oldhack]

Shut up you ricebowl.

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

[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

[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.

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.

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

[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

[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.

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.

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.

Schoolhouse Rock

[Nirvelli]

Conjunction junction, what's your function?

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.