NASA switches off Voyager instruments to extend life of the two interstellar spacecraft 'Every day could be our last.

[Admin]

NASA engineers are turning off two instruments on Voyager 1 and Voyager 2 to ensure these twin spacecraft can continue exploring interstellar space.

NASA switches off Voyager instruments to extend life of the two interstellar spacecraft 'Every day could be our last. : Read more

 

[Classical Motion]

It’s a shame we can’t develop a potential between the craft and a trailing wire for power, for dark space travel.

 

[contrarian]

It’s a shame we can’t develop a potential between the craft and a trailing wire for power, for dark space travel.

They should have made those RTGs much bigger.

Seems likely they did not expect these spacecraft to last so long.

 

[billslugg]

A trailing wire that generated power by crossing the local magnetic field would slow the craft. Some slowing might be acceptable.
Voyagers are going 17 km/s or 1.7e4 m/s
A kilogram of mass at that speed has a kinetic energy of 1/2*m*V^2 joules or 1.4e8 joules. Each craft weighs 722 kg thus each has a total of 1e11 J. They each use 200 watts of power currently. A watt second will give one joule. Their kinetic energy is sufficient to power their instruments for 16 years.

 

[Classical Motion]

I would love to sample Voyager. For corrosion and mutation. Before and after photos. I doubt we could make an ocean buoy that would last that long. Or a balloon.

We need to sample previous moon mission artifacts for analyses too. What kind of paint(protective covering) does a moon or space structure need?

How much damage does cosmic radiation do? What would it do to a generational garden?

Perhaps not as much as suspected.

As for space power, we need to live off the land. Some how. There is charge, electricity, moving thru space. If we can collect it. Or use it to rotate(charge) battery or capacitor banks.

 

[modelrocketman]

They should have made those RTGs much bigger.

Seems likely they did not expect these spacecraft to last so long.

Agreed but I think the design parameters were to explore our Solar System and that was it. They weren't expected to last!! It was decided to keep going as ground stations got better. I read in aviation journals there was a time when the younger controllers stepping in didn't know the spacecraft's programming language as it was so old! Modern craft use different programming computer languages. They had to get older, retired controllers out of retirement to train the "new guys" It currently takes 22.5 hours one-way to get commands to Voyager II and 22.5 hours to receive an acknowledgement! An excellent example of the speed of light which is the same speed radio waves travel!! Example it takes 5 to 20 minutes for radio signals from Earth to hit Mars depending on the planet's positions relative to each other. This is cool stuff!

 

[contrarian]

I read in aviation journals there was a time when the younger controllers stepping in didn't know the spacecraft's programming language as it was so old!

Yes, the Voyagers used a version of Fortran (V) that is not used anymore. They were lucky to find the people who made these programs still around and helpful.

But other Fortran variants are still used in a number of scientific computing apps.*

* https://en.wikipedia.org/wiki/Fortran

 

[Hevach]

Making the RTGs bigger wouldn't have helped a whole lot unless the whole probe were made bigger and more robust. A lot of instruments just stopped being useful after Neptune. They've already passed far beyond the range of the low power antenna and even had to change how they communicate for the big antenna to work at this distance, and even if the RTG doesn't give out the antenna just won't be up to the job soon (possibly as soon as later this year for low end predictions). Multiple thrusters have failed, heaters have failed, memory units have failed, instruments have failed, almost everything is on backups (a few things are switched back to broken primaries because the backups are broken worse)... At this point more on the Voyagers has failed than is still working.

The mission at this point is as much an exploration of long range engineering as it is a scientific mission. It's mission goal is for the signal to finally be lost in the noise, and it's in a tight race with the battery and the failure list which will happen first.

 

[billslugg]

Yes, the Voyagers used a version of Fortran (V) that is not used anymore.

I can't be of help here as I only learned Fortran IV.

 

[contrarian]

The mission at this point is as much an exploration of long range engineering as it is a scientific mission. It's mission goal is for the signal to finally be lost in the noise, and it's in a tight race with the battery and the failure list which will happen first.

Failures have certainly piled up, but from what I read some critical instruments to study interstellar space are still providing significant data, which is why they are powering down less critical systems. So yes, it may boil down to instrument failure in the end, but it looks as though one or both will run out of power before total instrument failure. Time will tell.

NASA Turns Off 2 Voyager Science Instruments to Extend Mission – Voyager

blogs.nasa.gov

 

[DanaBspaced]

Agreed but I think the design parameters were to explore our Solar System and that was it. They weren't expected to last!! It was decided to keep going as ground stations got better. I read in aviation journals there was a time when the younger controllers stepping in didn't know the spacecraft's programming language as it was so old! Modern craft use different programming computer languages. They had to get older, retired controllers out of retirement to train the "new guys" It currently takes 22.5 hours one-way to get commands to Voyager II and 22.5 hours to receive an acknowledgement! An excellent example of the speed of light which is the same speed radio waves travel!! Example it takes 5 to 20 minutes for radio signals from Earth to hit Mars depending on the planet's positions relative to each other. This is cool stuff!

Weight is always at a premium for a space craft. I imagine the RTGs were as large as they could manage.

 

[Torbjorn Larsson]

Still going.

Also, they're getting increasingly worried that someone will accidentally hit the 'retract' button, and that the end of the cable thrashing around as it winds up could devastate the Earth's surface.

The magnetic field and plasma wave instruments are still collecting useful trans-heliosphere interstellar space data.

Making the RTGs bigger wouldn't have helped a whole lot unless the whole probe were made bigger and more robust.

They embiggened the RTGs (and RHUs heaters) by having several - 3 RGTs and 9 RHUs
https://en.wikipedia.org/wiki/List_of_nuclear_power_systems_in_space

The main problem is an unexpected degradation loss in the themocouple material.

Most RTGs use Pu238, which decays with a half-life of 87.7 years. RTGs using this material will therefore diminish in power output by a factor of 1 – (1/2)1/87.7, which is 0.787%, per year.

One example is the MHW-RTG used by the Voyager probes. In the year 2000, 23 years after production, the radioactive material inside the RTG had decreased in power by 16.6%, i.e. providing 83.4% of its initial output; starting with a capacity of 470 W, after this length of time it would have a capacity of only 392 W. A related loss of power in the Voyager RTGs is the degrading properties of the bi-metallic thermocouples used to convert thermal energy into electrical energy; the RTGs were working at about 67% of their total original capacity instead of the expected 83.4%. By the beginning of 2001, the power generated by the Voyager RTGs had dropped to 315 W for Voyager 1 and to 319 W for Voyager 2.[48] By 2022, these numbers had dropped to around 220 W.[49]

Future RTGs may be improved:

NASA has developed a multi-mission radioisotope thermoelectric generator (MMRTG) in which the thermocouples would be made of skutterudite, a cobalt arsenide (CoAs3), which can function with a smaller temperature difference than the current tellurium-based designs. This would mean that an otherwise similar RTG would generate 25% more power at the beginning of a mission and at least 50% more after seventeen years.

https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generator

Yes, the Voyagers used a version of Fortran (V) that is not used anymore. They were lucky to find the people who made these programs still around and helpful.

But other Fortran variants are still used in a number of scientific computing apps.*

* https://en.wikipedia.org/wiki/Fortran

I'm surprised they used Fortran instead of assembler, but NASA likely could afford to put more computing power on the huge probes.

Yes, in my reading there are papers where Fortran is used for speed, but the main use is the more or less conserved math library code which is often converted to C [see the link].

I would love to sample Voyager. For corrosion and mutation.

Space corrosion and mutation can be studied on the ISS - which is a near Earth, not interplanetary or interstellar environment - and on the new Moon missions.

For mutations in living organisms associated with Vikings, you need surviving spores that awakens in a viable environment. Spore survival drops a factor 100 per 6 years in ISS studies [https://www.sciencedirect.com/science/article/abs/pii/0273117794904480 ], so for Vikings the survival is decreased with a factor 10^-16. The spore survival on probe surfaces is in question:

Previous studies have demonstrated that whenever spacecraft-associated surface samples yield fewer than ∼1 × 10^5 16S rRNA gene copies/m^2, they can be expected to give rise to very few, if any, cultivable cells or spores (13, 18).

[https://pmc.ncbi.nlm.nih.gov/articles/PMC3147454/]

 

[George²]

Future RTGs may be improved

Strange I thinking that 50 years after models which is used in Voyagers we already have better RTGs? Why NASA waiting so long to start new RTG development?

 

[billslugg]

He provided a reference for the work you are referencing.

 

[George²]

Yes with "would be made" in text. Which means that we not have this yet for using and this is only on paper, or probably with first examples in laboratory.

 

[erts12]

Yes, the Voyagers used a version of Fortran (V) that is not used anymore.

A slight correction ... The command, attitude control, and flight data computers onboard each Voyager spacecraft were/are programmed in their respective assembly languages.* Fortran was used on the ground system. Mission control (day-to-day spacecraft operations) originally ran on IBM 360 mainframes and I assume was written in IBM's Fortran. Offline engineering and analysis tasks (e.g., navigation and planning of planetary encounters) ran on Univac 1100-series mainframes and the tools were largely written, as you correctly note, in Univac's Fortran V. Around 1990, after Voyager 2's 1989 flyby of Neptune, the ground system was moved off of the mainframes onto minicomputers (?) and workstations. (The powerful IBM 360s and Univac 1100s were not devoted solely to Voyager and instead supported multiple simultaneous missions.)

As you point out, Fortran is still widely used, especially in scientific apps. The language has evolved over the decades. My post-Fortran-77 experience is nil, so I was a little lost at sea when I saw some modern Fortran code recently!

* Voyager Spacecraft and Fortran 5

 

[contrarian]

Thanks for the correction. These were all done with keypunch programming I assume. That must have been very tedious. Tried that myself long ago and decided not to get into computers, and never looked back. The slightest error and it would not work. Wiggle room is highly preferable.

 

[billslugg]

Yes with "would be made" in text. Which means that we not have this yet for using and this is only on paper, or probably with first examples in laboratory.

Correct, it is only on paper and with laboratory examples. This is the "development" you were asking about. The development is done. Now to mass produce and commercialize.