Pulling Gs and Mercury Shielding, readers ask

Once in a while, I plan on answering questions posed by my friends or followers--right now, you are one and the same.  Hi, guys!  And since Rob hasn't gotten me a list of things I should study about space to get spun up on the industry, I thought I'd tackle a few of those today from my friend Theresa:

Do astronauts feel the break from the atmosphere or from gravity?

No, they don't.  In order to break out of the atmosphere and the pull of gravity, they need to be speeding away from the earth at a great velocity.  That acceleration puts a lot of force on them, so much we measure it by how many times the earth's gravity the force is, or Gs.  The Apollo astronauts felt around 4Gs before they broke free of the Earth's gravity; the Space Shuttle pulls 3gs.  By the time the acceleration stops, they will go from that to weightlessness.  Note: the human body can stand about 10Gs before passing out, with training.  Fighter pilots have special suits to help them withstand the g-force. 
Pulling 6Gs, baby!  What a ride!

What do you know about Mercury as a shield against radiation?

Uh, nothing until tonight!  In fact, I was able to find very little about it on the internet, but I did discover one study by physicists in Egypt and Saudi Arabia, that being an interested amateur and not a scientist, I half understood and kind of skimmed over, but you gotta love the conclusion section!  They essentially experimented with liquid mercury as an addition to standard lead shielding.  They found that lead shielding did a significant amount all by itself--no surprise there--but that the mercury stopped another 10 to 15 percent of gamma radiation.  So from 2.3 cps to .00079cps.  CPS is counts per second as measured on a Geiger counter. 

Little perspective here:  1.6 cps is about 1 microservient/hour.  The average American gets 6,200 microservients of background radiation a year--or about .7cps.  Of course, in space, radiation is a LOT more dangerous, and spikes of radiation, like solar flares, can kill you.

So looking at this as an amateur space geek, this could be a good thing for spaceship shielding.  In theory.  The trouble is that mercury itself is very toxic, so it has its own dangers.  Also, it stays a liquid at room temperature, and freezes at -38 F/-39C.  Since I couldn't find anything that looked at its shielding powers as a solid, that would have to be looked into.  However, I think its toxicity is probably keeping it from being explored much as a shielding material.  Just imagine if the ship blew up on liftoff!

Danger, Will Robinson!  Don't spray that on Florida!

I did find this article about a nanofiber they're developing as a lightweight alternative to heavy shielding.  I'll report on it another day, and see if there's been any progress:  I'll do an article on shielding. (As a fun aside, I have magnetic shields in Discovery, which was fun to play with, from having to have counterharmonics when you crossed a shield to dock to how the viewscreens looked when you really saw what was out there and not the computer-sanitized version.)

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Walt said...

A couple of other problems with Mercury as shielding material is that it is only slightly lighter than lead and is definitely more expensive. Adding the Hazmat headaches, there has got to be a better material.

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