Update on the NASA Voyagers

[Benta]

I'm just fascinated about this mission:
https://arstechnica.com/space/2023/10/nasa-wants-the-voyagers-to-age-gracefully-so-its-time-for-a-software-patch/

[mendip_discovery]

I wish they would send more like this out there. With what we know we might be able to improve their abilities and maybe get them further out. Or at least get a snapshot of the same data but 50 year apart.

[Messtechniker]

Just wondering what sort of
capactors are being used here.

Built during pre-capacitor plague eara

Probably the circuits use as few capacitors as possible.

[Gyro]

Any capacitors of significant size are probably Wet Tantalum.

[Gyro]

I wish they would send more like this out there. With what we know we might be able to improve their abilities and maybe get them further out. Or at least get a snapshot of the same data but 50 year apart.

I seem to remember some controversy about the safety risks of launching Radioisotope powered SVs. I can't find much on the NASA website in the way of recent launches - although most other stuff can be done with solar panels.

[TimFox]

There is indeed controversy surrounding the plutonium-pile powered spacecraft, which use a thermopile (battery of thermocouples) stuck into the reactor to generate electrical power.
The main contention was possible problems if the spacecraft failed during launch, before leaving the Earth.
See  https://rps.nasa.gov/technology/  for NASA's description.

[Benta]

"Reactor" is a bit over the top to my mind. It evokes images of "China Syndrome" etc.
It's simply a lump of ²³⁸Pu with thermogenerators stuck to it.
Apart from the fact of Pu being somewhat poisonous, I don't see a radiation issue.

[Benta]

I wish they would send more like this out there.

So do I. But the Voyager missions were based on a special planet constellation that enabled "slingshot" acceleration by passing close by two/three of the big planets.
Back then, it was a breathtaking race to get them launched to take advantage of that. So they were built "quick-n-dirty" and still survive.
Something to think about.

[TimFox]

"Reactor" is a bit over the top to my mind. It evokes images of "China Syndrome" etc.
It's simply a lump of ²³⁸Pu with thermogenerators stuck to it.
Apart from the fact of Pu being somewhat poisonous, I don't see a radiation issue.

To get heat from plutonium, you need to assemble enough to create a chain reaction.
This is usually called a "pile" or a "reactor".
Plutonium, in fact, is poisonous, like other heavy metals, but its radiation is not a big problem if you don't ingest it.

[rdl]

RTGs use the heat from normal radioactive decay of plutonium. No chain reaction is involved.

[TimFox]

Yes, that's true of the RTG as discussed in the NASA article.
Actual fission reactors have been used in spacecraft by the Soviet Union, and once by the US for higher power in spacecraft.
See a discussion in  https://world-nuclear.org/information-library/non-power-nuclear-applications/transport/nuclear-reactors-for-space.aspx
Possible electrical generators discussed include thermopiles and Sterling heat engines.

[Alex Nikitin]

For me (as a certified tapehead) the most interesting fact is that Voyager 2 has a (still operational AFAIK) tape recorder on board.

 

Cheers

Alex

[Psi]

"Reactor" is a bit over the top to my mind. It evokes images of "China Syndrome" etc.
It's simply a lump of ²³⁸Pu with thermogenerators stuck to it.
Apart from the fact of Pu being somewhat poisonous, I don't see a radiation issue.

The issue, I think, was a mission failure where the craft re-enters the atmosphere and burns up. You don't want to spread a mist of Pu238 over a wide area.
I seem to recall the radioactive material is somewhat shielded in a way to survive reentry intact. But there is always a risk, it could get hit with other space debris and shattered into small pieces before re-entering.

But if we want to explore the outer solar system it's really the best option.

[Andy Chee]

Fission reactors were probably deemed too unreliable for deep space probes (too many moving parts for control rods) as retrieving the satellite for repair is not an option, hence the preference for RTGs (zero moving parts).

Uranus and/or Neptune are priority targets for NASA for an orbiter probe, similar to Cassini & Saturn, so watch this space.  Any launch trajectory will inevitably require gravity slingshots, probably from Venus and/or Earth.

[FrankBuss]

I wonder if there are details about the computer on the Voyager and the software, or even an emulator. I just found some general descriptions, like that they are using 3 computers, and Fortran and assembler. I guess NASA has an emulator for it? Would be fun to play with.

[schmitt trigger]

Weren’t these the probes fitted with COSMAC processors?

[FrankBuss]

No, looks like this is a misconception, according to this site: https://www.retrotechnology.com/memship/1802_spacecraft.html

It also notes that UDS was previously implemented in Voyager - on CMOS but discrete hardware, not on microprocessors.