Artemis II and the invisible hazard on the way to the Moon
ansto.gov.au
ansto.gov.au
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.
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
* 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.)
* Gamma is [eaten], because whether [wherever it is], 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.)
Naturally there's a whole bunch of unstated "all else being equal" going on, where no cookie's' elements are extra-likely to be permanently incorporated into your bones versus excreted, etc.
The radiation that passes through is not the problem.
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.
https://ocw.mit.edu/courses/22-01-introduction-to-nuclear-en...
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?)
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."
When I was doing my student teaching, one of the teachers in my department was a creationist, but he didn’t seem to have read Genesis 1 at all because when I asked him about the firmament in the heavens separating the waters above from the waters below, he had no idea what I was talking about. At least the flat-earthers know enough scripture to follow their dogma all the way to its absurd endpoint.
Notes:
0 - https://rationalwiki.org/wiki/Flat_Earth
1 - https://rationalwiki.org/wiki/Crank_magnetism
2 - This is why religions such as Jehovah's Witnesses require members to proselytize (including going door-to-door) because outsiders are so adverse to the members that the other insiders remark things like "those outsiders are so depraved, that's why you can only be with 'true believers' like us".
This is one of the primary techniques of SE. People are open to answering questions and with some skill with Socratic questioning, you can get results. Dumping data just causes cult/hoax members to feel threatened because you're attacking some core beliefs and they will try very hard to avoid losing a sense of self value[0].
Notes:
0 - "What I believe is wrong" -> "I am wrong" -> "I am a bad person".
How would they do the zero gravity during the live streams? They have to actually be in space, not even the zero-G parabolic airplane sim can maintain zero gravity for as long as their live streams have been.
I’ve heard people claim you can’t leave Low Earth Orbit due to the Van Allen radiation belts, but most Apollo deniers still believe low earth orbit is possible and reasonable. If they did fake Artemis II, it would have to be that the astronauts actually launched into LEO, and just didn’t really leave.
There’s just no way to fake zero-G for that long.
Both sides get a great boogie man to denounce. Save a bunch of money on arms if they're mostly fake. Once you learn about the Van Allen Belt, you call over on the red phone and say hey guys, we know we can't send people, but think about the ratings? Maybe we send you a case of Pepsi and we're good?
Like, for example, people who live in Aberdeen.
How does SpaceX tackle this with both the rockets, and the thousand of Starlinks.
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 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.
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.
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.
“Ticket closed, not a bug, caused by radiation bit flip”
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.
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.
The fact that a handful of devices hasn't failed is hardly proof that they can't. Hell, I've driven thousands of times and never actually NEEDED my seatbelt.
Again, that's not what I'm saying. I'm just challenging OP's assertion that any device with no radiation hardening will "immediately" fail, which clearly isn't the case with these devices. That's not me saying that radiation hardening isn't needed, quite the opposite.
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.
That does nothing to protect the human body from the radiation damage.
Talking about microchips is a distraction.
Decent Harry Potter book title