5 ms·

Interview question: can you design a system to safely locate and retrieve the capsule?

by cloudking 4y ago

throwanem 4y ago
Do you want it to scale horizontally, vertically, or both?
- cloudking 4y ago
  It could be stuck in a tree, so probably both.
  - throwanem 4y ago
    Dang it, I wish I didn't have real architecture design work to do today, because this seems like it'd be a lot of fun to research. Pure horizontal scaling would be trucks with survey counters. Pure vertical would be getting the US to retask one of those radiation-sensing satellites they use to characterize stuff like the Urals trace. (Not that that'd be likely to happen - national security, etc. But have the embassy in DC call NASA anyway, just in case they do have something.) Both would be GA aircraft doing a broad survey while trucks retrace the route. In any case the logistics would be critical, and speed as ever would be costly - good thing we have government-scale resources to work with. And, yes, the system in this case would be implemented on a human substrate, not a silicon one. This isn't Chernobyl; we don't need robots to do this job, the problem is of limited enough scope to be safely handled by properly trained and equipped humans - finding whom would be an early logistical concern. (The surveyors would be safe enough barring a forced landing or breakdown very near the source, which is unlikely but we still want to get rescue services on standby, or hire a couple of civil helicopters from the oil industry or similar, for fast recovery just in case.) And for a one-off job like this that needs to be done as fast as possible, there isn't time to design, build, and debug robots that can do it.
    - perihelions 4y ago
      - "Pure vertical would be getting the US to retask one of those radiation-sensing satellites they use to characterize stuff like the Urals trace." That's an extraordinary thing to mention in passing; do you have a source for this?
      - throwanem 4y ago
        Not as such, no. On further research, it looks like the understanding that led me to surmise the existence of such a survey capability was significantly incomplete.
    - krisoft 4y ago
      > The surveyors would be safe enough barring a forced landing or breakdown very near the source Weird assumption. Forced landings anywhere are unsafe. They are also very rare, because aircraft are quite reliable. The chances of the surveyors having a forced landing near the capsule must be minuscule (tiny danger zone compared to the extent of full search area, small probability of an aircraft having a forced landing at all). If you are counting such minuscule dangers then you are ignoring much bigger (but still relatively small) dangers to the surveyors: they might trip during the survey, they might get into a traffic accident as they search or their aircraft might crash injuring them (irrespective of distance from the source). They might have a wildlife encounter as they are verifying a signal (false or true positive). They might suffer from heat stroke, or get sunburnt. My intuition says that if you send out teams of people scurrying around the countryside these listed dangers are all more likely than having a forced landing right on top of the source. I also assume that you ignored them because they are all “everyday risks”, and you had tunnel vision concentrating on the radiation hazard.
      - throwanem 4y ago
        Great catch, and you're right: lots of things can go wrong in a desert whether there's radiation involved or not, so we'd have needed those helicopters either way. This is why we work in teams - don't be shy about anything else you see me missing.
thomasmg 4y ago
I don't know if something like that would help, but in Switzerland there are annual measurement flights (with a helicopter): https://blog.alertswiss.ch/en/categories/focp-news/annual-neoc-radioactivity-survey-flights-with-international-partners/ https://blog.alertswiss.ch/en/categories/focp-news/annual-ne... Part of this seems to be (sometimes?) to find radioactive sources: "The goal of this part of the exercise was to find two radioactive sources which, for training purposes, had been placed somewhere in an area of about 2,500 km2"
- deleted 4y ago
  [deleted]
- dividuum 4y ago
  I like how they don't mention the result of that exercise. I guess they didn't find it?
evrydayhustling 4y ago
I'm kind of surprised that something this radioactive isn't pretty easy to hone in on with a good Geiger counter. Someone with better physics want to enlighten me about ranges and sensitivity?
- pfdietz 4y ago
  You wouldn't use a Geiger counter, you'd want to use a gamma ray spectrometer. For example, a sodium iodide crystal doped with thallium (acting as a scintillator, connected to a photon detector) or semiconductor detector (large crystal of Si, Ge, or other materials, preferably of high atomic number.) The Geiger counter is filled with gas and will not effectively interact with gamma ray photons; the solid state detectors interact much more strongly with them, and (particularly the semiconductor detectors) have very good energy resolution, to spot the particular energy of photons from this particular radioisotope.
  - skissane 4y ago
    One of these? https://georesults.com.au/product/radiation-solutions-rs-125-nai-gamma-ray-spectrometer-handheld/ https://georesults.com.au/product/radiation-solutions-rs-125... Or maybe even https://georesults.com.au/product/rs-350-backpack-human-portable-radiation-detector/ https://georesults.com.au/product/rs-350-backpack-human-port... I imagine they are both rather expensive.
    - car 4y ago
      Radiascan makes an affordable scintillation counter, the RadiaCode 101. https://radiascan.com/ https://radiascan.com/ A good intro to what it can be used for: https://www.youtube.com/watch?v=x1UZdLVlBXg https://www.youtube.com/watch?v=x1UZdLVlBXg
      - skissane 4y ago
        Link to their actual product page: https://radiascan.com/products/detector-of-ionising-radiation-gamma-spectrometer-radiacode-101-works-with-android-google-maps/ https://radiascan.com/products/detector-of-ionising-radiatio...
DrZootron 4y ago
These systems exist. To name a couple: https://www.arktis-detectors.com/products/ https://www.arktis-detectors.com/products/ https://www.ansto.gov.au/products/detection-and-imaging-coris360 https://www.ansto.gov.au/products/detection-and-imaging-cori...
- cloudking 4y ago
  Neat, a fleet of those drones working in coordination might be able locate it.

Interview question: can you design a system to safely locate and retrieve the capsule?

throwanem 4y ago

Do you want it to scale horizontally, vertically, or both?

cloudking 4y ago
It could be stuck in a tree, so probably both.
- throwanem 4y ago
  Dang it, I wish I didn't have real architecture design work to do today, because this seems like it'd be a lot of fun to research. Pure horizontal scaling would be trucks with survey counters. Pure vertical would be getting the US to retask one of those radiation-sensing satellites they use to characterize stuff like the Urals trace. (Not that that'd be likely to happen - national security, etc. But have the embassy in DC call NASA anyway, just in case they do have something.) Both would be GA aircraft doing a broad survey while trucks retrace the route. In any case the logistics would be critical, and speed as ever would be costly - good thing we have government-scale resources to work with. And, yes, the system in this case would be implemented on a human substrate, not a silicon one. This isn't Chernobyl; we don't need robots to do this job, the problem is of limited enough scope to be safely handled by properly trained and equipped humans - finding whom would be an early logistical concern. (The surveyors would be safe enough barring a forced landing or breakdown very near the source, which is unlikely but we still want to get rescue services on standby, or hire a couple of civil helicopters from the oil industry or similar, for fast recovery just in case.) And for a one-off job like this that needs to be done as fast as possible, there isn't time to design, build, and debug robots that can do it.
  - perihelions 4y ago
    - "Pure vertical would be getting the US to retask one of those radiation-sensing satellites they use to characterize stuff like the Urals trace." That's an extraordinary thing to mention in passing; do you have a source for this?
    - throwanem 4y ago
      Not as such, no. On further research, it looks like the understanding that led me to surmise the existence of such a survey capability was significantly incomplete.
  - krisoft 4y ago
    > The surveyors would be safe enough barring a forced landing or breakdown very near the source Weird assumption. Forced landings anywhere are unsafe. They are also very rare, because aircraft are quite reliable. The chances of the surveyors having a forced landing near the capsule must be minuscule (tiny danger zone compared to the extent of full search area, small probability of an aircraft having a forced landing at all). If you are counting such minuscule dangers then you are ignoring much bigger (but still relatively small) dangers to the surveyors: they might trip during the survey, they might get into a traffic accident as they search or their aircraft might crash injuring them (irrespective of distance from the source). They might have a wildlife encounter as they are verifying a signal (false or true positive). They might suffer from heat stroke, or get sunburnt. My intuition says that if you send out teams of people scurrying around the countryside these listed dangers are all more likely than having a forced landing right on top of the source. I also assume that you ignored them because they are all “everyday risks”, and you had tunnel vision concentrating on the radiation hazard.
    - throwanem 4y ago
      Great catch, and you're right: lots of things can go wrong in a desert whether there's radiation involved or not, so we'd have needed those helicopters either way. This is why we work in teams - don't be shy about anything else you see me missing.

thomasmg 4y ago

I don't know if something like that would help, but in Switzerland there are annual measurement flights (with a helicopter): https://blog.alertswiss.ch/en/categories/focp-news/annual-neoc-radioactivity-survey-flights-with-international-partners/ https://blog.alertswiss.ch/en/categories/focp-news/annual-ne... Part of this seems to be (sometimes?) to find radioactive sources: "The goal of this part of the exercise was to find two radioactive sources which, for training purposes, had been placed somewhere in an area of about 2,500 km2"

deleted 4y ago
[deleted]
dividuum 4y ago
I like how they don't mention the result of that exercise. I guess they didn't find it?

evrydayhustling 4y ago

I'm kind of surprised that something this radioactive isn't pretty easy to hone in on with a good Geiger counter. Someone with better physics want to enlighten me about ranges and sensitivity?

pfdietz 4y ago
You wouldn't use a Geiger counter, you'd want to use a gamma ray spectrometer. For example, a sodium iodide crystal doped with thallium (acting as a scintillator, connected to a photon detector) or semiconductor detector (large crystal of Si, Ge, or other materials, preferably of high atomic number.) The Geiger counter is filled with gas and will not effectively interact with gamma ray photons; the solid state detectors interact much more strongly with them, and (particularly the semiconductor detectors) have very good energy resolution, to spot the particular energy of photons from this particular radioisotope.
- skissane 4y ago
  One of these? https://georesults.com.au/product/radiation-solutions-rs-125-nai-gamma-ray-spectrometer-handheld/ https://georesults.com.au/product/radiation-solutions-rs-125... Or maybe even https://georesults.com.au/product/rs-350-backpack-human-portable-radiation-detector/ https://georesults.com.au/product/rs-350-backpack-human-port... I imagine they are both rather expensive.
  - car 4y ago
    Radiascan makes an affordable scintillation counter, the RadiaCode 101. https://radiascan.com/ https://radiascan.com/ A good intro to what it can be used for: https://www.youtube.com/watch?v=x1UZdLVlBXg https://www.youtube.com/watch?v=x1UZdLVlBXg
    - skissane 4y ago
      Link to their actual product page: https://radiascan.com/products/detector-of-ionising-radiation-gamma-spectrometer-radiacode-101-works-with-android-google-maps/ https://radiascan.com/products/detector-of-ionising-radiatio...

DrZootron 4y ago

These systems exist. To name a couple: https://www.arktis-detectors.com/products/ https://www.arktis-detectors.com/products/ https://www.ansto.gov.au/products/detection-and-imaging-coris360 https://www.ansto.gov.au/products/detection-and-imaging-cori...

cloudking 4y ago
Neat, a fleet of those drones working in coordination might be able locate it.