[astar1]

These 2 failures could have been easily avoidable both times.

I really wish there was a push in the US government to create and stockpile plutonium-238 and ensure it's readily available, subsidized, and offered for all US probes/rovers/other scientific instruments in space (whether it be for NASA's use who currently has to ration because of how little they have left, or for private use after approval).

Like, why aren't all of space scientific instruments RTG powered like voyager 1 which is still providing useful scientific data 47+ years later. Think about all of the lost scientific insights over the past few decades because either NASA (because of a low stockpile) or private companies like intuitive (from their 2 failures) end up choosing solar panels for their source of power with no other alternative.

Besides the fact that solar panels can fail if they aren't pointed a certain way, they usually offer far less power, and are subject to radiation, micro meteor, or dust damage. All of these are the main reason why these instruments tend to have a far shorter lifespan than voyager 1.

[dreamcompiler]

One reason all space scientific instruments are not powered by RTGs is that prior to each launch NASA has to run a very involved and time-consuming risk analysis program to determine just how much of the state of Florida becomes uninhabitable for the next 10,000 years if the rocket blows up on the launch pad.

I used to conduct said risk analysis.

[mistrial9]

I had a Look Magazine cover from the early 1950s .. It showed oil barrels full of radioactive waste, with a guy moving one on a handcart, with heavy gloves on! The point of the photo was "radioactive material must be handled very carefully" .. the guy had thick gloves .. for a fifty gallon drum of radioactive waste, among many of them.. Things change

[__turbobrew__]

That is really interesting. How much of Florida would be contaminated?

[nuccy]

Generally I agree, but Moon is not a bad place for solar panels if a spacecraft has no contingencies and is able to harvest energy during Moon's day and store it in batteries to be used over the night. The sufficient power can be generated by a solar panel of the size (or even smaller) of the spacecraft itself. The other story is for missions like Juno [1] or Europa Clipper [2] which use solar panels near Jupiter - instead of centering develoment and mass budget around payload most of the spacecraft is an enourmously sized solar array. Juno panels generate 14kW on Earth orbit and only 500W near Jupiter [1].

1. https://www.jpl.nasa.gov/news/nasas-juno-spacecraft-breaks-s...

2. https://www.nasa.gov/missions/europa-clipper/nasas-europa-cl...

[nuccy]

Another non-obvious problem is that RTGs, as any other thermal machines, need a gradient of temperature to work, i.e. to generate electrical power there should be hot (nuclear material) and cold (radiators) side. On interplanetary spacecraft (Voyager, New horizons) Sun is in a predictable (and stable) direction so RTG's radiators can be put in a permanent shadow of the spacecraft. On the Moon the sun is moving, and there is no atmosphere (unlike on Mars where RTGs are used), so on a small spacecraft RTG will need to be dug deep into the regolith which is absoluteky non-trivial since just landing straight sometimes is a problem.

There are always tradeoffs, it is almost never "why don't they just" case in spacecraft development.

[chickenbig]

An alternative to Pu-238 is Am-241 https://www.world-nuclear-news.org/Articles/Can-americium-re... .

The UK has around 140t of trans-uranics in its civilian stockpile, of which an estimated 5.6 tonnes of this is Am-241 per https://www.repository.cam.ac.uk/bitstreams/627b4440-37c9-4e....

[hombre_fatal]

Reading the title and then your first sentence is the most HN experience.

All they had to do was just...

[idontwantthis]

Seriously I started reading that comment expecting to find out the lander only had two legs or something.

[ethagknight]

Spin up a quick national plutonium reserve, takes like 3 minutes, such incompetence

[tekla]

Clearly HN is smarter than an entire team of Aero/Mechanical/Electrical engineers who have not thought of the obvious solution.

[philsnow]

It was my understanding that RTGs are relatively dense compared to their energy output. They made sense for Voyager because incident light from the sun falls off as the square of the distance and they were designed to be the farthest-away man-made objects ever.

But if you "just" want to put a probe on the moon, solar panels weigh less than plutonium.

[jmyeet]

Historically, PU-238 was a byproduct of (fissile) Pu-238 production for nuclear weapons. That need kinda went away with arms reduction treaties beginning in the mid-to-late Cold War. IIRC the US nuclear weapons stockpile is about 10% of what it was at its peak. AFAIK there is no current Pu-239 production in the US.

The need for Pu-238 was recognized years ago as the stockpile of consumed by various space probes and I believe Oak Ridge now products Pu-238 fuel pellets. I'm not sure if this production could be ramped up.

But Plutonium use has various risks associated with it. Aside from the obvious security risks, you're strapped it to a rocket that may explode while launch and come back to Earth. This is effectively a dirty bomb if the RTG containment is breached.

Solar panels are really the right choice for anything out to at least mars. Here we had a probe fall over. Would that be recoverable with RTG? Maybe. Maybe not.

[4gotunameagain]

As with everything in aerospace, the reason is a trade-off you are unaware of. In order to launch an RTG you need to abide to extensive compliance requirements that ensure no ball of plutonium lands in someone's head. Ergo weight. In space, weight is everything.

You are one internet search away from finding the specific power of RTGs and of solar panels on the moon.

[eqvinox]

That's great but I'm reasonably confident that if the probe ends up sideways, at least half of the science instruments won't work anyway. And no guarantee on communications either.