"Born nearly two decades after the spacecrafts launched"
Respect to those engineers and scientists who built it, and those who continue to push the boundaries (from someone born nearly 2 decades before they launched!)
Nearly nine years after leaving the solar system, and decades beyond its original mission, Voyager 1 is still gathering valuable data, providing plasma readings to continuously sample the density of the interstellar medium. Scientists at Cornell University have used data from the spacecraft, launched in 1977, to uncover a weak …
"It is not expected to have the power remaining to operate a single scientific instrument beyond 2025."
I wouldn't put it past the abilities of this amazing team to devise some means of enabling an instrument to be used intermittently even beyond that date. And I'm sure there'll be investigators working through the existing data a good while after that.
It's good to be reminded of the best we humans are capable of.
I'll bet it is.
It is incredible that we've been able to do such things. It is indispensible that we continue to milk Voyager for every ounce of scientific data we can get while we still can.
And it is a tribute to Science and to the entire human race that NASA selflessly grants access to such data, instead of hoarding it.
I'm not saying that NASA has a habit of hoarding data, I'm saying that NASA is the embodiement of Knowledge, giving access without hesitation to any data it has on our Universe.
There are some forces for Good in our world, and NASA is one of them.
This is a testament to the days when in order to try to ensure that something would last it's expected life, it was over-engineered.
We now know so much about materials science that we can engineer to the limits of the materials. These new things will not last in the same way.
I'm not sure whether this is a good thing or not. On one hand, we get much more bang for the buck during the initial mission. On the other, we're less likely to get these amazing windfalls in the future.
Open-ended design where feasible - has always provided unpredicted enhancement capabilities later. Make a design too precise and there is no room to handle any unexpected problems.
Tom Peters gave an example of a successful multi-contractor missile project. The interface specs were deliberately woolly to allow for unforeseen adjustments.
It is like documentation: the more precise the detail - the more likely it is to be wrong at some future point.
One of the Star Trek films ("The Search for Spock" I think) started with a Klingon Bird of Prey destroying an old probe that looks remarkably like Voyager. Also in the original Star Trek film, V'ger was a Voyager-class probe that had been massively upgraded by an alien civilisation (you caught a glimpse of the probe hidden in the core of the vat V'ger structure).
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Just in my lifetime (and speaking from my own country, YMMV):
* Growth of analog TV channels, then sudden conversion to digital = likely lower total broadcast power and less "noise" of spillage to other frequencies.
* Death of many radio stations (which may have a digital conversion of their own someday).
* Rise of analog mobile phones, then quickly killed for digital, which is limited to only a few frequency bands.
* Rise of Wi-Fi, again limited in frequency spread.
* Overall better EM design in many products compared to industry and appliances of 50 to 100 years ago.
Does this actually mean we're wasting less EM/RF into space even as we use more in this thin shell of atmosphere? Maybe. Can NASA tell us?
Doesn't really matter, every frequency is used in multiple locations around the globe, that's not a problem on the ground as you will only get the one that's nearest to you but out in space they are all about the same distance away so extracting a single signal from the mush of multiple signals would be pretty close to impossible.
In fact the combined mush might be indistinguishable from random noise.
Uplink spill might be detectable from a distance but that will sweeping round like a lighthouse beam as the Earth rotates so that's not too much of a concern.
First, things like car engines, hard drives, & vacuum tubes are incredibly low power by the time you get past the absorbtion of the atmosphere.
Second, for a long time (several decades), there have been requirements for shielding regarding how much is being transmitted.
Third, signals from the control center are very high power, veryfocused, and very narrow band. They are also on a gimbled transmitter tower, so the operational window lasts several hours each day. It is also turned off when not pointed at the probe.
In fact the combined mush might be indistinguishable from random noise.
Most digital transmission methods these days are designed to be (nearly) indistinguishable from noise. Makes them more efficient, less susceptible to dynamic interference and less likely to interfere with other things... on the earth.
I suppose we keep away from the frequencies used by the likes of Voyager, but if some eejit 'white space' device comes along, raising the noise floor even just a little could totally drown out such weak signals. At least a single-carrier AM, FM or PM signal could be 'notched' out...
I think digital TV was a bad idea. Back in the analogue days, I could always get a picture. It might have had snow, but I could always watch the program. Now, if it rains, or if the atmosphere isn't right, I get extreme pixalisation and the picture keeps freezing. I have line of site to the transmitter too.
As to Voyager, long may it continue on it's merry way.
When I had 4 analogue channels, I could always seem to find something to watch.
Now with all the digital and streaming we can never seem to find anything interesting to watch.
Saying that, we have been watching "The Muppet Show" from - actually come to think of it - about the same time Voyager 1 launched!
"We continue to pollute the radio spectrum on our planet like all the other things we screw up!"
Just a few short years ago, scientists engaged in the hunt for extra-terrestrial life, using our own current communications trajectory, were considering that advanced civilisations might not be detectable as they switched from "primitive" radio comms to wired and fibre for most wide band, wide interest entertainment etc.
Now look at us!!
After a heavy session in a country pub we wandered over to a massive radio tower to see if we could climb it. Very heavily protected - apparently someone had bas jumped off it and they'd upgraded the security. We found this out the next night talking to someone in the pub who'd been working there and was very pleased we were too pissed to try the gate with he hadn't locked- why would you at 3 am? We were giggling round the perimeter trying to find an overhanging tree to fall out of.
According to NASA's real time tracker at https://voyager.jpl.nasa.gov/ it's about 14,133,497,500 miles from Earth you'd have to stack 12.5 trillion Osmans on top of each other and, since it's going over 38,000 mph, you'd have to add about 10,000 Osmans per second.
Outside of ElReg standard units, you'd have to walk around the Earth about 565,340 times to get to where it is now and you'd have to do it in less than a second per walk to keep up.
> nuclear technology is very efficient
It's not really "nuclear" technology as we usually understand it, it's just a radioisotope thermoelectric generator (Wikipedia).
There is no fission or fusion, or whatever else we call "nuclear power" going on, just a normal, natural process you find all around you in nature.
"So where does the heat come from, and why is it halving every n years?"
Most radioactivity does not involve fission. Typical radioactive decay is alpha emission (helium nuclei), beta emission (electrons), and gamma emission (photons). All these carry energy. Fission is splitting into two or more substantial nuclei, bigger than He. That is my interpretation, anyway.
There is indeed no fission, but just nuclear decay. This is often misunderstood. Plutonium-238 (which I think these RTGs use) decays to uranium-234 with the emission of an alpha particle (helium nucleus) which is moving pretty quickly, which is where the energy comes from. For the purposes of an RTG U-234 is effectively stable (its half-life is about 250,000 years), but it eventually decays in turn through some chain ending with lead.
This decay is a natural process insofar as plutonium-238 is natural, which it's not: its half-life (~88 years) is so short there's no primordial plutonium-238 in existence and I don't think it's a decay product of anything else natural). You want a fairly short half-life however as that corresponds with a fairly high power output of course.
Fission is a different process than decay: fission is when an nucleus absorbs a neutron and then splits into two daughter nuclei of fairly substantial mass. An example of this is uranium-235: U-235 + a neutron splits into barium-141, krypton-92 and three neutrons.
Plutonium-238 is fissionable but not fissile: what that means is that if you fire a high-enough energy neutron at it you can get it to split, but it won't sustain a fission chain reaction. Uranium-235 is fissile, which means it will sustain a fission chain reaction, as the neutrons spat out will cause further fission (often you need to 'moderate' them – slow them down – however).
But in an RTG no fission is happening: it's just nuclear decay, which happens to anything not stable.
"fission is when an nucleus absorbs a neutron and then splits into two daughter nuclei of fairly substantial mass"
Fission to be merely splitting; spontaneous fission is certainly possible, as distinct from induced fission, which is what you have described.
The "parts of roughly equal mass" is indeed the fragment that had slipped my mind - the normal usage of the word doesn't require the split to be into "about equal parts", but in the context of nuclear fission it is of course used to differentiate from the more traditional decay products.
Spontaneous fission does occur as you say, but it's absurdly rare in natural elements, and generally much rarer than other decay processes. As an example uranium-235 has a half-life of 700 million years: its spontaneous fission half life is about 3.5E17 years: about 27 million times the age of the universe. You need to get to really heavy artificial elements before the SF half-life becomes significant. As best I can tell the SF half-life of plutonium-238 is between about 7.4E15 and about 8.6E15 years: something over half a million times the age of the universe (and 90 trillion times its actual half-life).
Almost the only place where spontaneous fission matters is in nuclear weapons design, where you need to assemble the mass of fissile material without a spontaneous fission setting it off before you're ready. That's why uranium-235 is the only option for gun-type devices: they have a really long assembly time (ish 1ms) and you need a good chance that there will be no spontaneous fissions in that time: uranium-235 has a very low spontaneous fission rate for a fissile material. Implosion devices are much less fussy as their assembly time is much shorter.
Sorry for the thumb down, but I understand that your thought was if the instruments weren't doing any science but the probes' transmission strength wasn't attenuated NASA would write off any monitoring. That may yet happen, but monitoring the signal already needs a network of antennas: adding others is pretty easily done.
I personally don't think NASA will quit monitoring of the Voyagers for a while: it's not every day a probe passes the heliopause.
> I understand that your thought was if the instruments weren't doing any science but the probes' transmission strength wasn't attenuated NASA would write off any monitoring
No, sorry, I admit I wasn't very clear.
I'm more thinking along two issues: The first is obviously money, and the future availability of it for projects without tangible short/mid-term profits. Times are changing... Second issue is our sky getting progressively covered by huge flocks of chatty Internet satellites (not only Starlink, there are others about to jump on the bandwagon), which will certainly disturb the already faint signal from Voyager. And of course you can't really tell Voyager to shoot between the endless sheets of chaff constantly zooming over our heads.
Indeed. That and the Gaia data (from the ESA probe) are already dramatically changing the view of our local galactic system.The understanding of this view is fascinating and growing. The Oort Cloud, for example, is conjectured to be a sphere of debris that exists at very large distances (200,000 au or so off the top of my head) so a long way out.
As a boy growing up in the 70s we knew nowt about this area of space. But we are growing our knowledge nicely. All very interesting. Well done all.
"As a boy growing up in the 70s we knew nowt about this area of space. But we are growing our knowledge nicely. All very interesting. Well done all.
We not have known much about it, but we knew it was there. I started reading SF as a teen in the 70s and that's where I learned that there was such a think as the Oort cloud.