Deep Space Radiation, Black Holes And Other Questions - Episode 14

Any discussion of black holes and similar always reminds me of Terry Pratchett's observation that it's hard to discuss physics using a language designed to tell other monkeys where the ripe fruit is ;)

Can't believe Scott completely missed the most important advantage of space planes over capsules: They look so much cooler!

My method for shielding is distance. I live on the East Coast and my radioactive in-laws on the West Coast. I don't recommend it though, as no matter how far away they are their going to send me to an early grave.

A planet tidally locked to a neutron star with one side uninhabitable due to the radiation is hilarious to me as a concept.

I worked for an R&D firm where we used high neutron and high gamma ray sources to measure the density and porosity of material being drilled through in the oil and gas industry. Gamma rays were easy to deal with as lead would quickly absorb them. Neutron particles were much more difficult as they are at a much higher energy state. Hydrogen works well to slow, then stop the neutrons, but it takes a fair amount of volume. For portable shielding, we needed something better. We came with with a sandwich of UHMW and lead. The UHMW (1") would drop the neutron to a lower energy state, changing most of the radiation to gamma, alpha, beta, and zeta. A relatively thin layer of lead (1/4") could then absorb this EM radiation. We were able to make 2' square panels that could be easily moved by hand to be put into place to shield personnel from the radiation sources as they were being loaded into the tool and then sent down hole. This ment that the drilling crew was not required to have radiation monitor badges issued to them, nor were they forced off the rig while the quick installation of the sources happened. Two area monitors was all that was required. We never exceed 1mr/h at any time.

Scott posts at bedtime. Ideal.

High Z-number elements to shield photons (X and gamma rays), low Z-number elements to shield neutrons.

I am a nuclear engineer and have never heard of using concrete with lead in it. Since concrete is a structural material, they use iron instead. Usually in the form magnetite.

For crewed missions to Jupiter's moons, there was the HOPE study, exactly for a mission to Callisto with numerous different variant depending on propulsion.

It's funny when certain people pretend space and especially the Van Allan belts are some sort of insta death nuclear reactor they have to fly through. Because, you know, "Radiation"... Also thumbs up for having "Universe building" as hobby.

"If you wanted to mount a mission to Callisto, it wouldn't be to hard. " - Scott Manley, January, 2022

The following was an eye-opener for me. A substance is a good gamma ray absorber if it offers a high amount of electrons per unit of volume, since it is ray-electron scattering events that dissipate the energy of the gamma rays. The substance Lead has a high density, but that is only indirectly the reason why Lead is a good gamma ray absorber; having such a heavy nucleus means Lead has more electrons per unit of volume than pretty much any other substance. LATER EDIT: As pointed out in the reply by Timmy Brolin: there are elements that are denser than Lead; significantly denser. We know that lead is quite reactive, indicating that the outer electrons of Lead are relatively loosely bound. Generally, having loosely bound electrons tends to correlate with a larger atom size. As we know, Gold is highly inert. I assume that is because all the outer electrons of Gold are tightly bound , which tends to correlate with smaller atom size.

The difference between radiation requirements for LEO vs GEO (and above) is night and day. A LEO capable FPGA is $5, a GEO capable FPGA is $15,000. Redundancy means nothing if the part latches up and burns out.

The greatest amazement of space is this: How easily it can turn great minds into nothing more then confused children. Well done black holes, may we never fully understand you!

Neutron stars can also go flying on exciting trips through the universe as a result of the dynamics of their birth. That presents the possibility of a neutron star being an extrasolar capture or even temporary visitor.

Paraffin is an excellent hydrogen rich absorber seldom mentioned. It has material advantages like castability or block walls and no toxicity.

1:20 on Earth we use both: heavy materials such as lead and even depleted uranium for gamma absorption, and light (high hydrogen, such as water, paraffins or polyethylene) materials for neutron shielding. When the radiation is mixed, a layered cake approach is used, called graded Z shielding, where the materials with an increasing atomic weight are stacked in proper order

One thing I always wondered, why not shield the sleeping bags? Lead lined sleeping bags, plastics for cabin shielding etc... You don't wear it all day but but it could cut a nice chunk out of the daily exposure.

@ScottF short answer: yes, everything falling in is imprinted on the horizon, from an outside perspective. It not only gets redshifted to invisibility but also roasted to a plasma soup in the accretion disk, so the imprint is massively scrambled. Finally, of you were to fall in you actually could witness the event horizon and you would reach the singularity in a finite time. PBS spacetime covers all this in detail if you want to know more.

From the vantage point of a distant outside observer, an object falling towards a BH and very near the event horizon would not only be gravitationally redshifted and frozen in time but also smeared and scrambled over the whole surface of the event horizon.