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A maintenance-free power source capable of lasting the 200 or so years it would take to make it to 542 AU does not seem within humanity's current technological

A maintenance-free power source capable of lasting the 200 or so years it would take to make it to 542 AU does not seem within humanity's current technological capabilities. Parker at its highest velocity could make it there in a century, but it doesn't have to slow down and stop. Or station keep. When we have a power source that can do 5kW (I just doubled Hubble, 542 AU would probably require much more for communications) for 100 years I'll agree that its design can be refined and its lifespan extended to 200 and 542 AU is within our reach.

dotnet00 1y ago
With distances that big, is it even necessary to slow down much? The depth of focus is probably a couple dozen AU? Even if it takes the probe a century to get there, if you can squeeze a decade or two of observation out of it without slowing down, there's no reason to bother and instead send a new upgraded telescope every decade or so. As far as power requirements go, assuming a doubled power demand from Hubble might be a bit excessive. A telescope that far out would have to be nuclear powered, so thermal regulation is 'free'/passive and RCS load is reduced (don't have to constantly adjust to point away from the Earth), which I expect are the biggest power draws on Hubble. If we assume a 150 year lifetime, with a 3kW draw by EOL and current RTG tech... RTGs have ~6% efficiency, so for 3kW electricity, you need 50kW in heat. RTG electricity output drops ~2% per year, so after 150 years, you have 5% of the initial electrical output, and you get ~0.57W/g of Pu-238. Meaning, you need ~600kg of it to power the telescope this way [https://www.mathscinotes.com/2012/01/nuclear-battery-math/ https://www.mathscinotes.com/2012/01/nuclear-battery-math/]. That's not a politically feasible amount, but it's not technically impossible with current/near future tech whose development could be spurred on by serious interest in this kind of mission. 'Proper' fission reactors can also do the job, you get higher efficiency and don't have to run the reactors for the entire 150 years besides accounting for decay (e.g. an RTG that needs to provide enough power to keep some clocks running, the electronics and batteries warm, and trigger whatever mechanism would start up the reactor). Probably less than 100kg of Pu-238 just by better reactor efficiency.
- ycui1986 1y ago
  i don't think modern semiconductor device will last more than 100 years, even without all the radiation. making something last more than a few decades is very hard.
  - le-mark 1y ago
    Does encasing electronics in lead help against high energy cosmic rays? With cheap kg to orbit one could assume the mass budget would be large.
    - chuckadams 1y ago
      > Does encasing electronics in lead help against high energy cosmic rays? Makes them worse unless and until you make the shielding several times thicker than anything you'd be able to launch from the ground. Watched one science program that demonstrated it beautifully where the interviewee stuck several balloons on a board and shot at it with a high-powered rifle, popping just one. Then he stuck a metal plate in front of the balloons and shot it, and the resulting shrapnel popped all the balloons behind it. That's a cosmic ray hitting shielding. That's also an unsolved problem with any Mars trip. Electronics can be built redundantly to recover from cosmic ray hits. Humans not so much.
  - alex_young 1y ago
    Considering that the longest continually operating computer is in Voyager 2 and has been running for nearly 50 years I would be surprised if this was actually a problem. https://www.guinnessworldrecords.com/world-records/635980-longest-period-of-continual-operation-for-a-computer https://www.guinnessworldrecords.com/world-records/635980-lo...
- os2warpman 1y ago
  I agree with you. It is indeed spherical frictionless cow-ly possible if we spend a trillion dollars to increase ORNL's annual Pu production capacity so that it doesn't take 200 years to make 600kg of Pu-238. When someone demonstrates a complex device (let's set aside power generation how about a valve? Or a capacitor?) that can last a century in space I'll agree that it is actually possible. That's what "current level of technology" means. The lego bricks exist, now, today, preferably in stock ready for immediate shipment on Digikey, and can be snapped into place.
perihelions 1y ago
[deleted]
- varjag 1y ago
  It then would have to brake..
  - minitoar 1y ago
    Or just keep launching more so there’s always a usable one
cubefox 1y ago
> A maintenance-free power source capable of lasting the 200 or so years it would take to make it to 542 AU It wouldn't take nearly that long. The proposal is to use solar sails. There is a nice video about the details on YouTube: https://www.youtube.com/watch?v=NQFqDKRAROI https://www.youtube.com/watch?v=NQFqDKRAROI
fpoling 1y ago
Project Orion-type space craft can archive 1000 km/s and can travel within 3 years 542 AU. And this is absolutely feasible technically, just not politically.
deleted 1y ago
[deleted]

dotnet00 1y ago

With distances that big, is it even necessary to slow down much? The depth of focus is probably a couple dozen AU? Even if it takes the probe a century to get there, if you can squeeze a decade or two of observation out of it without slowing down, there's no reason to bother and instead send a new upgraded telescope every decade or so. As far as power requirements go, assuming a doubled power demand from Hubble might be a bit excessive. A telescope that far out would have to be nuclear powered, so thermal regulation is 'free'/passive and RCS load is reduced (don't have to constantly adjust to point away from the Earth), which I expect are the biggest power draws on Hubble. If we assume a 150 year lifetime, with a 3kW draw by EOL and current RTG tech... RTGs have ~6% efficiency, so for 3kW electricity, you need 50kW in heat. RTG electricity output drops ~2% per year, so after 150 years, you have 5% of the initial electrical output, and you get ~0.57W/g of Pu-238. Meaning, you need ~600kg of it to power the telescope this way [https://www.mathscinotes.com/2012/01/nuclear-battery-math/ https://www.mathscinotes.com/2012/01/nuclear-battery-math/]. That's not a politically feasible amount, but it's not technically impossible with current/near future tech whose development could be spurred on by serious interest in this kind of mission. 'Proper' fission reactors can also do the job, you get higher efficiency and don't have to run the reactors for the entire 150 years besides accounting for decay (e.g. an RTG that needs to provide enough power to keep some clocks running, the electronics and batteries warm, and trigger whatever mechanism would start up the reactor). Probably less than 100kg of Pu-238 just by better reactor efficiency.

ycui1986 1y ago
i don't think modern semiconductor device will last more than 100 years, even without all the radiation. making something last more than a few decades is very hard.
- le-mark 1y ago
  Does encasing electronics in lead help against high energy cosmic rays? With cheap kg to orbit one could assume the mass budget would be large.
  - chuckadams 1y ago
    > Does encasing electronics in lead help against high energy cosmic rays? Makes them worse unless and until you make the shielding several times thicker than anything you'd be able to launch from the ground. Watched one science program that demonstrated it beautifully where the interviewee stuck several balloons on a board and shot at it with a high-powered rifle, popping just one. Then he stuck a metal plate in front of the balloons and shot it, and the resulting shrapnel popped all the balloons behind it. That's a cosmic ray hitting shielding. That's also an unsolved problem with any Mars trip. Electronics can be built redundantly to recover from cosmic ray hits. Humans not so much.
- alex_young 1y ago
  Considering that the longest continually operating computer is in Voyager 2 and has been running for nearly 50 years I would be surprised if this was actually a problem. https://www.guinnessworldrecords.com/world-records/635980-longest-period-of-continual-operation-for-a-computer https://www.guinnessworldrecords.com/world-records/635980-lo...
os2warpman 1y ago
I agree with you. It is indeed spherical frictionless cow-ly possible if we spend a trillion dollars to increase ORNL's annual Pu production capacity so that it doesn't take 200 years to make 600kg of Pu-238. When someone demonstrates a complex device (let's set aside power generation how about a valve? Or a capacitor?) that can last a century in space I'll agree that it is actually possible. That's what "current level of technology" means. The lego bricks exist, now, today, preferably in stock ready for immediate shipment on Digikey, and can be snapped into place.

perihelions 1y ago

[deleted]

varjag 1y ago
It then would have to brake..
- minitoar 1y ago
  Or just keep launching more so there’s always a usable one

cubefox 1y ago

> A maintenance-free power source capable of lasting the 200 or so years it would take to make it to 542 AU It wouldn't take nearly that long. The proposal is to use solar sails. There is a nice video about the details on YouTube: https://www.youtube.com/watch?v=NQFqDKRAROI https://www.youtube.com/watch?v=NQFqDKRAROI

fpoling 1y ago

Project Orion-type space craft can archive 1000 km/s and can travel within 3 years 542 AU. And this is absolutely feasible technically, just not politically.

deleted 1y ago

[deleted]