8 ms·

Interesting. > There is a low level radiation hazard area clearly marked on the bottom of the capsule Whats this?

trothamel 11y ago
IIRC, it's a sensor that uses reflected gamma rays to measure the distance to the ground. When the ground is close enough, braking rockets are fired to reduce the touchdown velocity, making a land-landing more pleasant.
- kevan 11y ago
  >making a land-landing more pleasant. Or at least a bit less unpleasant http://www.slate.com/blogs/bad_astronomy/2014/06/08/back_to_earth_how_astronauts_get_back_from_the_space_station.html http://www.slate.com/blogs/bad_astronomy/2014/06/08/back_to_...
flashman 11y ago
Cobalt-60. Here is some more information on the Kaktus gamma-ray altimeter in Soyuz landers: http://www.spacesafetymagazine.com/spaceflight/reentry-descent-landing/soft-landing-on-kaktus/ http://www.spacesafetymagazine.com/spaceflight/reentry-desce...
- s0rce 11y ago
  This book seems to say its 137Cs. Anyways TIL.
- blueintegral 11y ago
  Wow, a radar that uses ionizing radiation is a crazy idea.
  - db48x 11y ago
    It's slightly dumb, but on the other hand it doesn't need much power.
    - deleted 11y ago
      [deleted]
  - atroyn 11y ago
    Seems ingenious - it's an active system that uses entirely passive components. No power draw, and will always work.
    - avian 11y ago
      I'm pretty sure the receiver can't be passive. If the receiver doesn't work due to power failure or malfunction, what good is a functioning transmitter? It would be interesting to know why they decided to go this way instead of a more conventional radar. Soyuz is already full of RF equipment for communications and docking procedures. Adding a landing radar probably wouldn't add that much to overall complexity. It might be that gamma backscatter is more consistent over expected landing surfaces than microwave reflectivity. Also, I wonder how they shield their detector from direct gamma rays from source so that they don't overwhelm the weak backscatter signal. They can't have much in the way of heavy shielding.
      - VLM 11y ago
        It could theoretically land anywhere on the planet in an accident situation, some freaked out country could fire up the radar jammers, would be terrible bad luck to land next to a weather radar, even if nothing bad happens it'll have Russian military aircraft loitering around the LZ and now you have the technical problem of proving every Russian aircraft radar ever made won't interfere with the landing system. I would guess if the rockets fire early the astronauts will be severely hurt (killed?) on landing so not firing early would be a priority. They didn't make it triple redundant for fun... Also without any information its very hard to tell if this is just good old fashioned ALARA at work, or if its a real threat. On one hand a powerful source would require a smaller detector and size and mass are expensive in spacecraft. Then again the crew needs shielding from the source and they're using gammas so source intensity is also not cheap. My guess is its a combination of ALARA principle at work combined with some first responders might have radiological monitoring and that will detect it, causing a freak out unless previously warned.
    - soyuz2 11y ago
      Kaktus-2V altimeter Main gamma-ray source at 662 keV, backscatter peak at 200 keV, 3 redundant transmitters / receivers. "no power draw" :) Uses 50W, weights 10kg. Good old Russian Teknology. [0] http://www.rtc.ru/index.php/kosmicheskoe-priborostroenie/fotonnaya-izmeritelnaya-sistema-malykh-vysot-kaktus-2v http://www.rtc.ru/index.php/kosmicheskoe-priborostroenie/fot... [1] http://www.nucsafe.com/cms/Gamma+Interactions+and+ID/46.html http://www.nucsafe.com/cms/Gamma+Interactions+and+ID/46.html
  - gene-h 11y ago
    Perhaps it would be better to call it gradar? This is certainly the craziest sensor I have ever heard of.

IIRC, it's a sensor that uses reflected gamma rays to measure the distance to the ground. When the ground is close enough, braking rockets are fired to reduce the touchdown velocity, making a land-landing more pleasant.

kevan 11y ago
>making a land-landing more pleasant. Or at least a bit less unpleasant http://www.slate.com/blogs/bad_astronomy/2014/06/08/back_to_earth_how_astronauts_get_back_from_the_space_station.html http://www.slate.com/blogs/bad_astronomy/2014/06/08/back_to_...

flashman 11y ago

Cobalt-60. Here is some more information on the Kaktus gamma-ray altimeter in Soyuz landers: http://www.spacesafetymagazine.com/spaceflight/reentry-descent-landing/soft-landing-on-kaktus/ http://www.spacesafetymagazine.com/spaceflight/reentry-desce...

s0rce 11y ago
This book seems to say its 137Cs. Anyways TIL.
blueintegral 11y ago
Wow, a radar that uses ionizing radiation is a crazy idea.
- db48x 11y ago
  It's slightly dumb, but on the other hand it doesn't need much power.
  - deleted 11y ago
    [deleted]
- atroyn 11y ago
  Seems ingenious - it's an active system that uses entirely passive components. No power draw, and will always work.
  - avian 11y ago
    I'm pretty sure the receiver can't be passive. If the receiver doesn't work due to power failure or malfunction, what good is a functioning transmitter? It would be interesting to know why they decided to go this way instead of a more conventional radar. Soyuz is already full of RF equipment for communications and docking procedures. Adding a landing radar probably wouldn't add that much to overall complexity. It might be that gamma backscatter is more consistent over expected landing surfaces than microwave reflectivity. Also, I wonder how they shield their detector from direct gamma rays from source so that they don't overwhelm the weak backscatter signal. They can't have much in the way of heavy shielding.
    - VLM 11y ago
      It could theoretically land anywhere on the planet in an accident situation, some freaked out country could fire up the radar jammers, would be terrible bad luck to land next to a weather radar, even if nothing bad happens it'll have Russian military aircraft loitering around the LZ and now you have the technical problem of proving every Russian aircraft radar ever made won't interfere with the landing system. I would guess if the rockets fire early the astronauts will be severely hurt (killed?) on landing so not firing early would be a priority. They didn't make it triple redundant for fun... Also without any information its very hard to tell if this is just good old fashioned ALARA at work, or if its a real threat. On one hand a powerful source would require a smaller detector and size and mass are expensive in spacecraft. Then again the crew needs shielding from the source and they're using gammas so source intensity is also not cheap. My guess is its a combination of ALARA principle at work combined with some first responders might have radiological monitoring and that will detect it, causing a freak out unless previously warned.
  - soyuz2 11y ago
    Kaktus-2V altimeter Main gamma-ray source at 662 keV, backscatter peak at 200 keV, 3 redundant transmitters / receivers. "no power draw" :) Uses 50W, weights 10kg. Good old Russian Teknology. [0] http://www.rtc.ru/index.php/kosmicheskoe-priborostroenie/fotonnaya-izmeritelnaya-sistema-malykh-vysot-kaktus-2v http://www.rtc.ru/index.php/kosmicheskoe-priborostroenie/fot... [1] http://www.nucsafe.com/cms/Gamma+Interactions+and+ID/46.html http://www.nucsafe.com/cms/Gamma+Interactions+and+ID/46.html
- gene-h 11y ago
  Perhaps it would be better to call it gradar? This is certainly the craziest sensor I have ever heard of.