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Comment by ethbro | Hacker News Reader

So, simple question: why isn't everything electronic shielded inside big lead blocks?

I get why this isn't the prevailing approach in aerospace applications: weight. But for a ground based robot with an external power source, why not heavy shielding cubes with minimal connections to the necessary exposed bits?

And why not just load it down with 5x CotS sacrificial cameras, then expose them as needed when the previous one dies?

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For typical Gamma radiation of about 1MeV photon energy or higher, you need about 1cm thickness of lead to reduce the radiation to about a third (by a factor of 1/ℯ). One order of magnitude of radiation hardness (reduce radiation to 1/10th) needs two centimeters of lead. That's getting heavy pretty fast.

Radiation intensity inside your box depends on the thickness t: I(t) = I₀·exp(-tρμ)

t: thickness, say 1 cm ρ: density of the material, for Lead 11 g/cm³ μ: absorption coeffcient 0.1 cm²/g [see ref 1] I₀: intensity outside of the box

    ...import numpy as np...
    In [5]: np.exp(-0.1 * 11.34)
    Out[5]: 0.32174370422037013

I(1cm) = 32,2%, I(2cm) = 10,4%

[1] http://www.eichrom.com/PDF/gamma-ray-attenuation-white-paper...

Everything had to fit into a 100mm diameter pipe leading into the containment vessel.

https://youtu.be/rQVT9beES08?t=27s

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