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How do plutonium-powered pacemakers work?

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Re: How do plutonium-powered pacemakers work?

#81

Post by Kelbit »

ctdonath wrote: post #80
rplnt wrote: post #60

Earlier quoted context omitted.

Wouldn't wireless charging pad work well for this? Or is it unnecessary complicated considering how long batteries last?

The issue being rather close to my heart, I'd rather have a single-use 7-year battery + full modern replacement of unit, than have to fiddle with periodic recharging just to prolong use of aging technology. Nobody much wants their life relying on >10 year old computers. (Remember: it's already "old technology" when you first get it implanted.)

Rumor is Medtronic pacemakers still use 6502 processors (albeit on modernized custom silicon) with code written in the 80s. Big medical OEMs are loathe to change.

Re: How do plutonium-powered pacemakers work?

#82

Post by Kelbit »

bigiain wrote: post #44
Kelbit wrote: post #15

Earlier quoted context omitted.

Easier to replace the whole pacemaker than the battery, for a couple of reasons: * Pacemakers are hermetically sealed, usually laser-welded in a titanium case. Adding a replaceable battery with seals would complicate this arrangement. * By the time the battery winds down, there may be a newer, better pacemaker on the market that fits the patient's needs. * Since a battery replacement necessitates surgery, you might a…

> The exact lifetime depends on how much current the pacemaker takes to operate. Not so sure. I don't think the plutonium decay is affected by the current drawn via the thermocouple - it'll just keep putting out the same power (well, the same decaying power curve anyway) no matter how much current you try and draw. I suspect the thermocouple's voltage will just sag so the maximum drawn power will be the thermal outpu…

Correct, the decay is not affected by the amount of charge you've pulled out of the cell.

What I meant (and should have expressed more clearly) is that the pacemaker will have some minimum current it needs to be able to draw from the TEG to operate, and after the plutonium has decayed to a certain point it won't be able to source enough current to operate, so the pacemaker will brown out.

Re: How do plutonium-powered pacemakers work?

#83

Post by godelski »

bunderbunder wrote: post #16
acidburnNSA wrote: post #8

FTA: > I wondered if there wasn't also worry about plutonium being recovered for weapons use, but the risk seems much smaller The answer here is a simple "nope." Plutonium in radioisotopic thermal generators is always Plutonium-238 with a 87.7 year half-life. You can't make bombs out of it. The fissile isotopes of Plutonium are 239 (24,000 year half-life) and 241 (14 year half-life, but a beta emitter instead of alph…

It sounds to me like it's only a simple "nope" if the only weapons you are worried about are nuclear weapons. Pu-238 could still be useful for radiological weapons such as dirty bombs. If you're worried about them then it becomes a (slightly) more nuanced, "How many morgues do I have to raid, and can I do it before the authorities catch on to the Crematorium Bandit?"

The threat of dirty bombs is pretty low, there's a reason they aren't used. They are extremely hard to obtain, and don't add a significant amount more deaths (if the blast didn't kill you, the radiation will probably not. Though definitely send you to the hospital). They work great as weapons of terror, and there is a lengthy cleanup process, but there's a reason that they aren't common. The people working on the device are also more likely to die, and more easily caught. The materials are difficult to obtain, but definitely not impossible. It just probably isn't worth the time and effort when you could more easily make and/or obtain more conventional explosives.

This is all assuming the smaller type of explosives used in acts of terror.

Re: How do plutonium-powered pacemakers work?

#84

Post by taneq »

josu wrote: post #35
taneq wrote: post #32

Earlier quoted context omitted.

Titanium is nicely biocompatible. Tungsten can be poisonous. https://patient.info/doctor/tungsten-poisoning

Could you have an inner layer of tungsten to seal the plutonium, and an outer layer of titanium to avoid poisoning the host?

I guess that'd work - the patient is going to stop worrying about biocompatibility long before the titanium gets near its melting point!

Re: How do plutonium-powered pacemakers work?

#85

Post by toomuchtodo »

Kelbit wrote: post #81
ctdonath wrote: post #80

Earlier quoted context omitted.

The issue being rather close to my heart, I'd rather have a single-use 7-year battery + full modern replacement of unit, than have to fiddle with periodic recharging just to prolong use of aging technology. Nobody much wants their life relying on >10 year old computers. (Remember: it's already "old technology" when you first get it implanted.)

Rumor is Medtronic pacemakers still use 6502 processors (albeit on modernized custom silicon) with code written in the 80s. Big medical OEMs are loathe to change.

You don’t fix what isn’t broken when it’s a life critical system.

Re: How do plutonium-powered pacemakers work?

#86

Post by effie »

c3833174 wrote: post #71
effie wrote: post #65

Earlier quoted context omitted.

The project manager Suzy Dodd talks a lot about shutting down instruments in order to save the power. But the power output of radioisotope thermoelectric generator does not depend on how much power is drawn. Is there a conventional electric battery on the Voyagers that the instruments draw their power from instead?

By saving power she means leaving enough margin to keep the supply voltage stable, running the machine near the limit could cause voltage sag when another device like the tape drive is turned on. Just like apple limits power draw of it's devices to avoid possible reboots when too much current is demanded from an old battery.

That makes sense. I still wonder if there is battery that would be recharged by the RTG. Seem like it could save some useful energy for the future time when it is needed.

Re: How do plutonium-powered pacemakers work?

#87

Post by perlgeek »

effie wrote: post #86
c3833174 wrote: post #71

Earlier quoted context omitted.

By saving power she means leaving enough margin to keep the supply voltage stable, running the machine near the limit could cause voltage sag when another device like the tape drive is turned on. Just like apple limits power draw of it's devices to avoid possible reboots when too much current is demanded from an old battery.

That makes sense. I still wonder if there is battery that would be recharged by the RTG. Seem like it could save some useful energy for the future time when it is needed.

I don't know, but it wouldn't surprise me if no such battery was on the spacecraft.

You have to remember that Voyager is way past its originally planned mission life span, and that the nuclear battery was more than fine for the planned life span.

Batteries tend to be heavy, not operate well at very low temperatures, and wear down quicker than the 40+ years since construction of the space craft.

From the perspective of the original mission design, even with incredible foresight, it seems to be not worth the trade-offs.

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