Artemis II and the invisible hazard on the way to the Moon
ansto.gov.au60 points by zeristor 8 hours ago
60 points by zeristor 8 hours ago
> Dose rate matters. Particle type matters. Direction matters. Shielding matters.
There's an old story where a professor quizzes his physics class about how to most-safely distribute different kinds of radiation sources. A common variation involves three baked cookies, emitting alpha particles, beta, and gamma respectively. One must be eaten, one must be held in your hand, and one must be placed in a pocket.
A hint, and what I think is the interesting part of the answer, involves the idea that a victim is a lot like shielding. Things which are difficult to block are also things that are less-likely to stop and ruin your day.
I heard about this question in the MIT Ionising Radiation course. You can find it here, around minute 47:30 (wont spoil the answer).
https://ocw.mit.edu/courses/22-01-introduction-to-nuclear-en...
Are we protecting the person with the cookies, or everyone else? I'm struggling to think of the best answer
Alpha: In the hand held away from the body would be reasonably safe. In a pocket of a lab coat might provide a little more shielding from the body with the coat material, but it is physically closer. Eaten would be very bad for the user, but protect the outside world the best
Beta: Medium penetration, would likely not be safe in any of these three situations
Gamma: High penetration, definitely not safe in any of these situations, best would be to get it as far away from you as possible, so held at arms length would mean you might only get high radiation exposure in your hand. Hospital visit is probably needed in any of these three situations
Eat the gamma cookie, it's the worst option for any, but with gamma it won't matter much whether it's in your hand, pocket or gut.
Pocket the beta emitter, a little bit of shielding will make a big difference.
Hold the alpha emitter, if you hold it with just a pair of fingers you will be able to reduce you dosage a lot compared to holding it tightly.
IIRC:
* Alpha in hand. Eaten, the "shielding" that blocks it will actually be very active living cells, leading to severe health outcomes. Your external layers of dead skin cells will be be fine, putting it in your pocket would be excessive.
* Gamma in hand, because whether it's in your hand or in your pocket, it's roughly the same risk, and most of it is actually going through you without stopping to have an effect. (Compared to other two.)
* Beta in pocket, where the additional clothing layer(s) offer some meaningful protection compared to your hand.
The "twist" behind the exercise involves how people often assume penetrative power is proportional to danger, when in some ways it's really the opposite. (Consider the danger profile of neutrinos.)
Oh, I thought you have to choose one of the options for each cookie, no repeats
I guess in that case it would be to eat gamma? Assuming you're keeping all three long-term, the gamma particles will be washing over you whether they're inside you or out.
Same with x-rays. People tend to think “soft” X-rays are safer because they are quickly absorbed by tissue without passing through.
The radiation that passes through is not the problem.
Sure, using the ambiguous wording to assume the cookies all have such a large activity they are unsafe no matter how they are stored is technically a solution. But it's equally possible the teacher is imagining the cookies as only slightly radioactive such that it is indeed possibly to safely store them according to the alternatives given if you choose the correct pairs.
Can these cookies be weaponized? Are there secret cookie enrichment factories? Would weapons-grade cookies still be good with milk?
Only weapons-grade milk.
Heavy milk (whole) is required for cookie enrichment. But depleted milk (skim) still has value.
Eat the gamma, pocket the beta, hold the alpha. Nothing in the picture here stops gamma rays so it doesn't matter what you do with those; skin will stop alpha particles, but so will mucosa (and you die of that); in your pocket, the beta source will spall X-rays off your trousers at least some of the time so the beta burns will be mitigated.
I enjoy how moon-landing deniers will use the van Allen belts as a reason for why the astronauts could not have made it to the moon because of radiation exposure. Like, you don't believe NASA that they went to the moon, but you believe NASA that the van Allen belts exist?
Strictly speaking, their existence was verified by Sputnik 2 (though the Soviets only released data on it after the fact, corroborating data from Explorer 1), so if you have a highly _specific_ conspiracy theory, around NASA rather than space stuff in general, that _could_ still work, I suppose?
No, because the Soviets have to in on faking the moon landing. They were also landing a spacecraft at the same time as the landings. To fake the moon landing you'd also have to fake the entire cold war.
I'm not disputing that conspiracy theorists tend to lack rigor but there is a full spectrum of positions between "space is fake" and "one specific extraordinary achievement with high incentive to fake it is fake".
There's indeed a full spectrum of positions in this case, but they are all worthless in the sense that they add nothing to someone's understanding of reality.
You know some people grow up in untrustworthy environments and auto didact their way to something like first principles thinking and depending on things shaking out you might only believe what you've personally seen with your own eyes. And well, earth looks pretty flat in daily life.
Any entertaining “Artemis II is a hoax” takes?
You just need to look at the Facebook comments on any official NASA post about Artemis to see depressingly many of them. Some are joking or trolling, I’m sure, but I don’t think all.
I haven't been actively looking for them, but a friend sent me something about the launch tower escape zipline/gondolas and how that somehow indicated something fraudulent. He is not a denier, but works with one and is always asking me to refute that person's claims.
If your friend is trying to "cure" the denier, then it might be helpful for them to learn some of the tactics for reaching/deprogramming cult members. One that might be helpful is "street epistemology".
That's a bit too much to ask of these folks, I'm afraid, but I did boil it down for him by saying that the real question is understanding why he is inclined to believe its a hoax, rather than trying to pile up evidence in front of him. I suppose that's what "street epistemology" is, though. Nice to have shorthand terms for these ideas.
I also included a thought experiment for him:
Imagine you take a conspiracy influencer and actually put them in the spacecraft with the astronauts so they could see the whole thing with their own eyes and wouldn't be able to deny it. They return to earth to tell their followers that it's all real. Do you think everyone will be convinced, or would they say he's now in on the conspiracy and find a new person to lead the conspiracy theory?
(I wonder if there is a sociological shorthand term for this?)
> Imagine you take a conspiracy influencer and actually put them in the spacecraft with the astronauts so they could see the whole thing with their own eyes and wouldn't be able to deny it. They return to earth to tell their followers that it's all real. Do you think everyone will be convinced, or would they say he's now in on the conspiracy and find a new person to lead the conspiracy theory?
https://en.wikipedia.org/wiki/The_Final_Experiment_(expediti...
"The participating flat Earthers all admitted that the midnight sun was a real phenomenon. The larger flat Earth community has largely rejected the results and accused the participants, including the flat Earthers, of having faked the expedition and of being part of a larger conspiracy to promote the spherical Earth model."
I am fairly certain that Artemis II has proven conclusively that they were right all along and the world is flat.
> Artemis II and the invisible hazard
Decent Harry Potter book title
I thought one of the things with New Space is that Commercial off the Shelf parts were being used more and more. I’m assuming if that’s a case there have been more mishaps.
How does SpaceX tackle this with both the rockets, and the thousand of Starlinks.
Rad Hardened parts are "Commercial off the Shelf" parts. VORAGO, TI, and others provide rad hardened parts via vendors like Mouser and Digikey. They're just much more expensive.
The threat of radiation is severely overblown.
NASA is overpaying for underperforming "hardened" hardware that performs no better than non-hardened. You can see this yourself with the mars helicopter ingenuity.
If you are desperate for extra safety then just include multiple computers, literally what spacex does.
The threat of radiation is not overblown at all.
The errors caused by radiation are extremely frequent and you definitely must guard against them, otherwise anything will fail immediately in space.
However that does not necessarily require hardware measures. It may be more efficient if instead of a slow antique CPU with hardware redundancy you use a fast modern CPU, even if it is more sensitive to radiation and even when it lacks hardware redundancy, but you do each computation several times, verifying that every time you get the same result, and if possible you use different algorithms or verification methods, to be able to detect some permanent errors.
This is what the Mars helicopter did. If it had used standard smartphone software, the helicopter would have failed instantly.
>>The errors caused by radiation are extremely frequent and you definitely must guard against them, otherwise anything will fail immediately in space.
I asked this in another thread but I will repeat it here - how come that their bog standard iPhones that they use for taking pictures with are still operating fine then? If like you said, "anything will fail immediately" - doesn't sound like that's the case? They have electronic watches with no radiation hardening, they have regular laptops with no radiation hardening.....I'm not saying that it's not a problem, but it definitely doesn't seem to be in the area of "immediately failing in space" if you don't have that.
As other posters have said, the personal devices of the astronauts are already used in spaces that are much better shielded against radiation than a typical satellite or the Mars helicopter.
Radiation shields add mass and volume, so it helps if the electronics is somewhat resistant to radiation, allowing for less efficient shields.
Even with the enhanced shielding, the personal devices experience errors from time to time, e.g. the photographs taken may have some wrong pixels and they sometimes have to reboot their laptops or smartphones, if weird behavior happens. Like others have said, these kinds of errors are not important, unlike in the computers that control the spacecraft, where errors are not acceptable, so those must use either hardware or software means to combat the effects of radiation errors.
None of these devices are mission-critical. Worst case they have to be restarted; then they are fine again and the world moves on.
Yes, but that wasn't the question. OP said anything that's not radiation hardened will fail immediately - to which I ask ok, what about all the stuff they brought up with them which doesn't seem to be instantly failing.
The radiation levels are much lower where humans live, otherwise they would not live for long. Without humans, thinner and lighter radiation shields are used, to reduce costs.
Theoretically, one could use the same electronic devices that are used on Earth, if one would add thick enough shields, but this is impractical, so one must make a compromise, by combining some less efficient shielding with devices more resistant to radiation.
The Mars helicopter had essentially no shielding, as it had to be extremely light to be able to fly in the Martian atmosphere.
Moreover, as explained in the parent article, the radiation levels are not constant. A great part of the radiation comes from the Sun, and that part fluctuates continuously (i.e. the so-called "space weather"). The electronic devices must be designed to withstand the peaks of solar radiation, even if the radiation levels are less than that much of the time.
The astronauts can shut down their personal devices, preventively, when there is a peak of solar radiation, or when they pass through the radiation belts.
Sounds like Microsoft have a credible excuse for two outlook instances ruining
“Ticket closed, not a bug, caused by radiation bit flip”
(I have no expertise or knowledge of this area but...)
tl;dr: people need (heavy) radiation shielding, cpus et al can live without it
I'd imagine their bog standard iPhones and watches are generally in parts of the craft which have more radiation protection than others and, further, that it's probably only the parts where people are going to be that get that protection (due to weight savings, etc.) and if you can mitigate radiation problems by using a $30 CPU instead of a $2 CPU and save $100K of weight on radiation shielding on the CPU compartment, that's a no-brainer.
Unshielded circuits are basically radiation detectors. Even here on planet Earth bitflips are an underappreciated source of unreproducible bugs.
A bit flip in an index variable, a pointers or in native code can send the CPU on a wild goose chase around memory.
To add insult to injury, applications like browsers use JITs, which generate and execute large amounts of native code on the fly, making them even more vulnerable for this kind of fault.
The same issue arises from overclocking, inconsistent power sources, and from damaged RAM cells, but those problem sources can presumably be dismissed on a vehicle with pristine, well-made hardware during a short hop to the moon and back.
> If you are desperate for extra safety then just include multiple computers, literally what spacex does.
That does nothing to protect the human body from the radiation damage.
Talking about microchips is a distraction.
Depending what model you subscribe too, small dose radiation can be healthy for you.
The radiation in space is not "small dose". It's firmly established that it is quite bad for human health.
The BAE Systems RAD750 radiation-hardened single-board computers used by Orion are commercial products but typically costs between $200,000 to $500,000 per unit
You should read the article. The problem is the destructive effect of radiation on the human body, not on the space hardware.