Half a croissant, on a plate, with a sign in front of it saying '50c'
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Incidentally, why isn't "spacecraft" another word for "interior design"?

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Alpha Pendant

An eternal heartbeat
  [vote for,

Sometimes life is little more than a series of disappointments. Moments are fleeting, meaningless. It would be erroneous to suggest that a mere pendant could make a difference, but an idea can be more than its physical manifestation. It can be a symbol, something eternal; an emotional anchor.

Exotic substances like polonium and americium exhibit alpha radiation. While deadly poisonous if swallowed, these materials are safe to handle as the alpha radiation is unable to penetrate skin, or even a few centimetres of air. The radiation consists of "heavy" particles, much heavier than other kinds of radiation.

Many people fear ionizing radiation, or more specifically, fear the concept of radiation. It is the ultimate threat: a toxin which you cannot see, hear, or smell. Pedantry over different types of radiation is irrelevant. To the ignorant, the invisible enemy is everywhere.

The Alpha Pendant contains a significant amount of radioactive americium. Beyond the visceral thrill of carrying a vial of poison around your neck, the americium serves a purpose.

The pendant consists of an evacuated glass cylinder, set in gold. Within the glass is a wheel of metal foil, mounted on the finest of needle bearings against jewelled supports. Every effort has been made to minimize friction of the wheel's rotation. Attached to the wheel are four paddles, and to each paddle a small disk of americium is attached on one side.

The alpha radiation carries momentum. The asymmetry of the paddles maximizes the effect. The power delivered is minuscule, but balanced against the inertia of the foil, the precision bearings, and the high vacuum it resides in, the resulting force is enough to rotate the assembly once per second.

The outer circumference of the wheel is partially coated in reflective silver, the remainder in absorptive black nanocrystals of gold. The pattern of reflective/absorptive coating is such that the reflected light, visible through the glass window on the pendant, creates the characteristic double-thump of a human heartbeat.

In essence, the pendant is a nuclear-powered trinket, both simpler and more intricate than a watch.

The mechanical heartbeat of the Alpha Pendant pumps no blood, but its silent pulse is a visible beacon of hope, a reminder that if we put our minds to it, it is possible to make something that lasts. With a half-life of 432 years, the americium-powered heartbeat will outlive your great grandchildren.

mitxela, Jun 13 2020

Alpha Patent http://www.alphapatent.com/company.htm
If you ever want to file with this idea [pashute, Jun 14 2020]

Alpha decay particle propulsion http://chinaxiv.org...d=8688&filetype=pdf
If it can propel a ship it can spin a radiometer [kdf, Jun 15 2020]

Half life calculator https://www.calcula...ife-calculator.html
[kdf, Jun 15 2020]

Helium Traps https://physicsworl...he-hunt-for-helium/
[kdf, Jun 15 2020]


       Coat the inside with phosphorescent paint and it will glow in the dark too!
pocmloc, Jun 13 2020

       Love it.   

       Make Americium Great Again!   

       i want one with spinning paddles that look like tiny american flags. just make sure it's adequately shielded.
sninctown, Jun 13 2020

       //The pattern of reflective/absorptive coating is such that the reflected light, visible through the glass window on the pendant, creates the characteristic double-thump of a human heartbeat.//   

       I just love this no matter what it is. The writing is so flowing and incredibly fluent that it's more like a poem than anything. Yes, yes, yes. +++++
blissmiss, Jun 13 2020


       //Make Americium Great Again!// [marked-for-tagline]
FlyingToaster, Jun 14 2020

       My mother was buried with her (working, to the best of my knowledge) pace maker.
pashute, Jun 14 2020

       Crookes radiometer.
xenzag, Jun 14 2020

       Your paddles could be made by a similar process to the americium disks in smoke detectors. But as you’d keep all of the emissions in a sealed container (instead of releasing them into an ionization chamber), the “high vacuum” in the pendant would eventually fill with trapped helium. This might slow the rotation down faster than you suggest from Am-241’s half life.
kdf, Jun 14 2020

       //trapped helium//   

       I'm uncomfortable to see those two words put together.
Voice, Jun 15 2020

       Uncomfortable? How so?   

       I haven't done the math to figure out how long it would take to build up enough ... uh ... mumble mumble ... trapped ... you know ... helium ... in an enclosed capsule to slow the device down. But looking online to see if anyone ELSE had done so, I stumbled upon suggestions of using alpha decay for space propulsion (link). So spinning the vanes of a pendant probably isn't too far fetched.   

       As long as you can get around the ... uh ... mumble mumble ... trapped ... you know ... helium ... problem.
kdf, Jun 15 2020

       Oh, and if it makes you uncomfortable, definitely DON'T read the linked article about h***** traps...
kdf, Jun 15 2020

       You could vent the trapped helium through a one-way valve
pocmloc, Jun 15 2020

       "one-way valve"
How does that work with a strong vacuum on the inside and presumably one atmosphere normal pressure on the outside? You'd have to get the valve open and somehow pump the helium out.

       That may be a non-issue though. Now that I've done a *little* of the math, I don't think helium build-up would be a problem, at least not for several decades. So here's a new puzzle - what size/mass/shape to you think the vanes should be if they are to turn once per second?   

       Under ideal conditions, an alpha particle leaves an unbound nucleus of an Am-241 atom at roughly 0.05c (5% of light speed). The remaining Np-237 nucleus (being 59.25x heavier) gets kicked in the opposite direction at 0.000844c. In practice though, with a bulk sample instead of a single atom... most of that energy goes into jiggling (heating up) the surrounding atoms. And all those alpha decays are randomly distributed - you only get useful thrust if you can bias enough of them in one direction.
kdf, Jun 15 2020

       Thanks for the comments everyone.   

       Before posting this, I had a go at working out how much americium would be needed. The part I struggled to estimate was the friction of the bearing, I'm not sure what a reasonable guess for that would be.   

       You can buy a "StaticMaster" anti-static brush that contains 500uCi of polonium on amazon. The alpha particles have an energy of about 5MeV, so the power output is around 15uW. Not all of that will go into pushing the wheel around, but a quick search and stackoverflow answer suggest that a mechanical watch uses just over 10uW. So, I convinced myself that with enough americium, the thing would work.   

       I did consider the accumulation of helium. One point to note is that ordinary silicate glass is permeable to helium, so it would diffuse out over time. This also implies that by osmosis, helium and hydrogen would seep into the vial from the moment it was made. My gut feeling is that the effects will be insignificant compared to the mechanical bearing.
mitxela, Jun 16 2020

       Very cool.
doctorremulac3, Jun 16 2020


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