Which one is veeger?
V1 or V2?
NASA has switched off a heater on a part of the Voyager 1 probe, plunging the temperature of its one functioning instrument to below minus 110° Fahrenheit (minus 79°C) – well below the minimum temps of minus 31° Fahrenheit (minus 35° C) at which it was designed to operate. Space boffins took the decision in order to conserve …
Eh? There's no "bubble" as such related to the Sun's gravity; gravity's strength fades smoothly away with distance, and there's no point at which it stops or has any change in behaviour.
Do you mean the heliopause, perhaps, which is related to where the solar wind loses its influence?
This is pretty amazing stuff. Voyager 1 was launched in 1977. Good Old Conservative NASA (as it definitely was then) built stuff using well tried and tested technology, so this tech is much earlier, like the use of an 8-track digital recorder. It takes 33 hours for a round trip message to get from Earth to Voyager. So NASA sends a signal, and waits a day and half to see if the space craft has responded.
And today, how long can we keep an "advanced" computer running for (my record is 287 days for the home server- YMMV).
Like I say - built to last.
Your home computer was really built for a price, and was built with the idea that someone could always "turn it off and on again".
A telecoms satellite built today would be expected to work for 15 years, and the main computer will be allowed up to 1 restart over that time. It would probably keep going longer too, but the solar panels won't output as much after 15 years of the crap in space, and by then there will be no fuel left to keep it in the same place in the sky so that the dish on your house is still pointing at it.
I know I'm nitpicking here, but since we're talking about highly professional equipment I'd like to pick up on that...
Even a not so advanced computer should have no big problems with being left turned on. In fact; in many cases its actually more healthy because it doesn't have to deal with power surges (even though most of it gets handled by your power supply unit) and more importantly your hard disks won't have to cope with drastic physical changes.
If on the other hand you're referring to the OS and as such uptime then I think its a very bad indicator. To me very high uptimes only make me think of insecure or maybe even unmaintained computer environments. Which by itself is no problem, but it gets a bit shakey when we're talking about stuff hooked onto the Internet.
I'll take low uptimes with recent kernels and software (Linux, Windows, BSD*) over high uptimes any day of the week.
"Even a not so advanced computer should have no big problems with being left turned on. In fact; in many cases its actually more healthy because it doesn't have to deal with power surges (even though most of it gets handled by your power supply unit) and more importantly your hard disks won't have to cope with drastic physical changes."
Not quite. The reason why leaving computers running is usually much healthier for them is simply the abundance of mechanical stress that occurs when components heat up and cool down. It has nothing to do with power surges (which btw also do occur when computers are running). Switching computers on and off means a lot of heating up and cooling down, and thus a lot of mechanical stress.
For hard drives an additional problem is that the spin-up phase is the one that stresses components most, which (depending on the designed-in margins) may lead to overstressing and therefore life reduction of electrical components on the PCB. However, with modern (aka less than 10 years old) hard drives this isn't a issue any more, but it has been for older fast-rotating SCSI drives and 5.25" and full height 3.5" drives of the past.
"If on the other hand you're referring to the OS and as such uptime then I think its a very bad indicator. To me very high uptimes only make me think of insecure or maybe even unmaintained computer environments. Which by itself is no problem, but it gets a bit shakey when we're talking about stuff hooked onto the Internet."
I agree 100%. Long uptime is key for certain areas like production control systems and similar stuff, but for general purpose computers it's just a sign that the system hasn't been properly updated for a long time.
I think a better factor than uptime to look at is how much unwanted downtime (which doesn't include updates) a system has accumulated.
"I'll take low uptimes with recent kernels and software (Linux, Windows, BSD*) over high uptimes any day of the week."
I agree with your main argument. The main problem is that people do not distinguish between planned and forced reboots. I like to reboot customer machines when a new kernel is installed, this takes a few minutes and is done when is convenient.
The machine at which I am typing is 10 years old, but runs an up to date kernel. I leave it on 24x7 andhave had few hardware problems over the years, just: CPU fans and hard disks.
mostly because they were launched at a time when the planets were in a sort of alignment that meant they could use each one as stepping stone on their path out of the galaxy, each planet they visted gave the probes a gravitational slingshot boost on the way past.
I dont think that kind of alignement is due to happen again for quite some time
I would add that modern ground based detection systems have advanced so much that sending probes to fly passed planets is really not a requirement any more.
when you add to the mix satellite based detection systems, the only way you are going to get better data is to place a probe on the surface of the planets.
the only point in sending probes outside of the solar system would be to try and intercept interstellar transportation that's passing us by without dropping in to say hello.
if you was to try and send a probe (or maybe people) to the nearest star then you are looking at a journey time of of around 18,500 years (travelling at the same speed as voyager), Why take on that expense for the benefit of the future generations, when in probably a hundred or so years time that journey time could be cut by a half. That is if something nasty doest happen on the way like and os needing a upgrade, or a reboot....
"Why take on that expense for the benefit of the future generations, when in probably a hundred or so years time that journey time could be cut by a half."
Can you imagine how pissed off the great*260-or-so grandchildren of the first ever interstellar explorers would be when they finally arrive at their destination, only to discover that the place has already been all screwed up by 9000-odd years of humanity?
Fly-by craft are the way you do a first survey of a planet/object/thingy. That let's you get a good idea of the environment (magnetic fields, temperatures, atmosphere's density and composition, etc). That gives you good specs for an orbiter, which gives you good info and specs for a lander, etc.
Recall that Mars had Mariners 3 & 4 fly by, had Mariner 9 orbit (finding shocking things like mountains, caldera, evidence of flowing water, etc), which allowed NASA to find sites and design instruments for Viking, which has allowed us to make better roving instruments, ... and so on
Voyagers 1&2 followed two Pioneer craft to Jupiter and one to Saturn. (The one that went to both also allowed NASA to try a gravity-assist path that would be crucial to Voyager.) Uranus, Neptune and (largely) Titan were unknown and needed flyby missions first.
The flyby missions are important, but we've done that for all the planets and until we design a mission to search the heliopause or Oort cloud, I doubt we'll have a reason to send anything out that far again.
(Of couse, having said that, something new will be discovered within a year ...)
"Why are we not building more of these probes to fling out of the solar system?"
True, we are not doing fly-bys, but we have take a long look at Jupiter (Galileo), Juno(??) is next for that, Cassini is doing wonders at Saturn, having landed on Titan and observed equinox up close, discovered the relationship between Encelidus and the F-ring, etc.
We are also doing good stuff with Kepler and related probes. I would really like to see an exploration of Europa's ocean :) So, there is a lot of exploration happening.
My great-grandma had a refrigerator that's been working since the 50's, except that the thermal relay welded closed some 30 years ago. Yes, working non-stop, you won't hear the fridge clacking-in and clacking-out in the middle of the night.
Except for a paint job on the handle, new sealing gaskets on the door frame and occasional de-icing every odd month, the bugger kept going. My 2nd degree uncle GAVE it away to charity, still fully functional.
Well NASA did all that, with something running on batteries. Top that.
PS. My car won't even start if parked for a straight month without new batteries. sigh.
And I can't forget the remark: "If someone built a washing machine that could fly...."
About 10 years ago an art gallery in London were selling big (2 metre) photographs (taken from original), mounted on aluminium, as art. There were Hubble shots, etc., but I bought a close up of Saturn -- part of the planet and rings, and two moons, that was taken by Voyager I. It is incredibly lovely and is better art than most things I can think of. When I hear of Voyager's continuing journeys, and continuing value, I feel like I am part of its family.
Yes... a big fucker with proper nuclear power source that could last 100+ years powering a vast array of instruments and multiple redundant comms channels. Should cost less than a Mars rover since there's no fancy re-entry mechanisms needed, just find a nice spot in the galaxy to point it at and send it off
I second that e motion, James Micallef, and would suggest it is carried already and accepted and currently HyperRadioProActive in Advanced Personalised Perception/Virtual Reality Fields in Live Operational Virtual Environments.
* Answers in a comment on this thread, please, is AI Start.
A member since 2008 and you’ve never seen AMFM post!!!!!!!!!!!!!!!!!!!!!!!
FYI, I put AMFM's post through a English-Yoda translator and I still can't make sense of it.
That e motion, I second james micallef and would suggest, carried already and accepted and currently hyperradioproactive in advanced personalised perception/virtual reality fields in live operational virtual environments, is it. Herh herh herh.
"Voyager 1's ultraviolet spectrometer (UVS), a light meter which is its only working instrument"
I thought that there were a few instruments still working? Perhaps this is the last optical sensor? I though that they were still detecting charged particles and magnetic fields?
The last update I've seen on the Voyager logs is from October last year. For anyone really bored, you can read it all here: http://voyager.jpl.nasa.gov/mission/weekly-reports/
"Voyager 1's ultraviolet spectrometer (UVS), a light meter which is its only working instrument..."
Means this is the only instrument that's still doing some sort of work. All the others are beyond their usefulness (e.g. the camera is too far from anything to take a good picture, and the temp sensor is pegged at the bottom) and have been shut down as a result.
"NASA said it expects Voyagers 1 and 2 to be unable to power any single instrument by 2025."
Means even the UVS won't be able to get enough juice by that time, as the batteries won't have enough power anymore. At that point, the Voyagers will just become inert, slightly-radioactive lumps in deep space.
One day millions of years in the future, when the sun has become a red giant and swallowed up the earth, these spacecraft (plus a lot of electromagnetic waves) will be the only signs left that we existed.
Of course we might have developed interstellar travel by then, but it's still a nice thought.
You are either extremely pessimistic or suffer from a failure of imagination.
Maybe if we were living in the year 1000, change in human conditions might seem non-existent, and we could well expect the drudgery of life to continue unchanged forever. However, from our current position we can extrapolate from the ever-accelerating progress of science and technology over the last 500 years or so.
Given that, why should humankind not be able to continue this progress, and in the process, over the next billion years or so, terraform other planets, send many more probes into interstellar space, or send colonies to other solar systems? Indeed, given the time scale involved, why should we not be able to survive the death of the sun?
And how many of the engineers who worked on creating that superb device thought that it would just be winking out in 2011 with nothing even close to follow it, no men ever touching the Moon again, etc?
I always think about that scene from a movie (I forget which) which started with flying through space, past Voyager, and onto the main plot of the movie. Did anyone really expect that we'd never overtake it (or even send anything in that direction again) in the 30-something years after it left?
I think one of the big milestones of future exploration will be to image / recapture those devices as we overtake them. But at this rate, it'll take hundreds of years.
"By 2008, radioactive decay of the plutonium fuel source had caused the output to drop to 285 watts."
I know we put golden plates onto Voyager which should tell possible aliens where we're located and give global impressions on who we are.
But somehow the idea of sending some nuclear waste along doesn't sound too appealing to me. It makes me wonder what impression this will leave on possible finders.
Are we sure we don't contaminate the aliens the very moment they open up Voyager to see whats it all about ? ;-)
Will almost certainly assume that the bird is hot and treat it accordingly.
It would have become somewhat radioactive anyway through secondary high energy cosmic rays and other ionising effects.
But the chances of it being found are effectively nil. It isn't scheduled to pass by any other systems any time soon.
when we invent/discover/buy from aliens some really fast effective way of traversing the local interstellar neighbourhood, I am sure we will go out and try and find these probes, and possibly try to return them, we know which way they are headed, we just have to catch up, we might also need to translate how to play the golden record too, or take a look in the 'historical archives'
1.5kbps over 11 billion miles, eh? When I was away on business last Tuesday, my hotel's "high speed internet" couldn't even manage that to the street corner.
I did manage to render useless their heavily-locked-down tv by attempting to change the settings so their heavily promoted HD channels weren't squashed, stretched, and spat out in a revolting, edge-enhanced 480i pixel gumbo. Serves them right.
That said, if 20-years-behind-the-times tech makes things more reliable, that cable box should be operating long past humanity's final space probe, continually puking out the last frame of the last reality show of the last human broadcast, showing us in our final glory: Inert, eyes-glazed, unaware of the sudden mutation of a lightning-fast hemorrhagic flu, and eagerly awaiting a Next Time that would never come.
Where was I? God, I feel depressed. You people write such negative articles, I must say.
All generators (mechanical, chemical or thermoelectric) experience the Braking Effect. In a mechanical generator, it tends to slow as the load increases. As a consequence it also causes the turbine driving it to consume more fuel -- same with a dynamo on a bike, you burn slightly more calories if you have the light switched on.
In batteries, the chemical reaction runs faster as load increases and thus the battery expires faster.
In thermoelectric generators the same holds true. More load will result in a faster rate of work in the system and shorten the life of the nuclear pile.
But your last sentence is what puzzled me as to quote from the Wikipedia (yes I know but I couldn't find a better source) Radioisotope Thermoelectric Generator article (http://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generator
" On the other hand, heat generation cannot be varied with demand or shut off when not needed. Auxiliary power supplies (such as rechargeable batteries) may be needed to meet peak demand, and adequate cooling must be provided at all times including the prelaunch and early flight phases of a space mission."
Which implies that the heat (and therefore power) output is constant and cannot be varied irrespective of load.
Kirchhoff's law would suggest that's impossible. The thermocouple must be less efficient the greater the load. Less effecient heat transfer from the pile, because the thermocouples must be warmer under load than not? Heat is work and work is heat.
Also since they are powering down the instrumentation to extend the useful life of the thermoelectric generator, there must be some kind of entropic relationship going on otherwise it wouldn't make any difference whether they shut down the instruments or not? The pile would die just as fast if its output was constant?
I don't know so please someone correct me if they know for sure.
Apples & oranges. Kirchoff's laws were drawn up before the concept of RTGs existed.
You can't throttle back an RTG power source. The rate of decay (and thus the heat generated) remains pseudo-constant, in an exponentially downward sort of way, regardless of the amount of power drawn by equipment. Look up the meaning of "half life" with respect to nuclear materials.
In other words, yes. The "pile" will "die" just as fast, even if it was floating in space, all by itself, not generating electricity for a space probe. Or even at the bottom of the Tonga Trench ;-)
My point is that "saving power" is the wrong way to convey the concept. Instead of "saving power", NASA is rather "redirecting available power as needed".
Note: Kirchoff (1824-1887) worked before the likes of the Curies (Marie, 1867–1934; Pierre, 1859-1906) & Röntgen (1845-1923) ...
Kirchoff's laws are an actual fact of electrical and electronic engineering.
Kind of the calculus we use developed by Newton to describe gravity.
Fundamental laws don't change just because they're old.
I take you point, however, that Nasa are in fact redirecting available power rather than saving it.
Nothing bad at all. First, explore. Then, use it carefully. Were there ever a word of lies from MPRTY? No, there were not. Anyway, the job will be monitored by the licensant, and the license can be dismissed at any moment. Also, adding some "user's fingerprint check" would be a nice option.
By the way, the testing of the sputnik is complete. Make no missiles (-:
the RTG is powered by the thermal energy released in the radioactive decay of Pu-238, which has a half life of 87 years or so. So in 87 years the thermal power of the RTG reduces by half. However the RTG's electrical power generation is not dependent on the thermal power of the heat source in the business end... but on temperature difference between it and it's heat sink (the heat sink is effectively cooled by the inky cold blackness of space). The rate of heat loss to the environment by black body radiation (the primary mechanism in a vacuum) is proportional to the fourth power of the temperature (Stefan-Boltzmann law). This is applicable because the hot end will not *only* be cooled by the RTG transferring heat to it's heat sink but by radiating energy directly into space (this is unavoidable, no insulation is perfect).
What this means is that the electrical power available from a thermo electric RTG falls away more steeply than the half life of the radio isotope used would naively suggest. (i.e. after less than one half life, 35 years is 0.4 half lives, the thermal power of the Pu-238 should be ~76% of what it was at launch, but the RTG is only now putting out 60% of launch power).
Now I'm sure all you gadget fans realise that a) gadgets consume juice, and b) heaters consume lots of juice. Therefore to manage the dwindling energy budget on the probe the NASA engineers have to gradually turn stuff off.
Plus I expect the reduced temperature difference in the RTG has reduced the voltage available too... this will further impair the probes ability to power it's gadgets.
Still a great effort from these wonderful probes... they'll likely outlast the civilization that built them (they'll be shutdown by then but still).
Assuming it reaches a star system. Assuming that the system supports intelligent life. Assuming therefore that the system has gas giants on long orbits acting as interplanetary vacuum cleaners for larger asteroids which could otherwise periodically wipe out all life on warmer inner planets. Assuming it doesn't get sucked up by these larger outer planets. Assuming it reaches the warmer, rocky inner planets without missing and hitting the star at the centre of the system...
It will probably burn up on entry.
Very unlikely to ever be found, in my opinion. Doesn't mean it wasn't worth trying.
Modern fridges need less than 500 kw-hr per year of electric power. Depending on your cost of electricity, maybe $50 a year. An elderly fridge (especially one with the contacts welded closed) is going to require many more kw-hrs per year (e.g. times N) - easily costing several hundred additional dollars per year. Giving such an energy-pig fridge to the poor is exactly the same as giving them blankets infested with smallpox.
Old energy-pig fridges are actually evil. Recycle them for scrape ASAP.
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