# RTG Power Output

#### Max-Q

##### 99 40
So I'm working on an Orbiter addon project with an RTG, and I have a couple questions.
• Americium-241 vs Plutonium-238: what would be the advantages/disadvantages of going with Am-241? All the RTGs that I know of use Pu.
• How much power could I get from an Am-241 RTG? I'm guessing less than a Pu one, since the half-life of Am is longer.
• Can I increase the power output of an Am RTG by just stuffing more Am in there? That won't work for Pu since the critical mass is so low.
I guess what I'm getting at in a roundabout way is how much heat is produced by the decay of Am-241 vs Pu-238.

Thanks!

#### francisdrake

These are very specific questions. I found a paper of the IAEA, Americium-241 radioisotope thermoelectric generator development for space applications.

They intend to develop RTG's for ESA. In the paper, an electrical power of up to 50 W is mentioned. This shall be achieved by combining several modules, each of them having 5W electrical output only, with a thermal output of 80 W each. The specific power is assumed with 1.5 W/kg.

If you need more power, more RTGs can work in parallel, but keep in mind all the thermal heat has to be radiated away from each RTG, and shall not be radiated into its neighboring module.

#### Max-Q

##### 99 40
I could probably get away with 50 watts. That's about 1.78 amps @ 28 volts. I need 1.6 amps to keep the essential bus alive, absolute minimum.
My Pu RTG gives 5.36 amps, but Pu is so expensive.
That higher output means that the batteries could be trickle-charged in an emergency even while running the ECLSS, so that's good.

#### Urwumpe

##### Not funny anymore
Donator
Well, just remember that the RTG can't be turned off. It always produces heat, and it always produces electricity, that you either use or dissipate in a shunt (essentially a large resistor with a heatpipe or radiator).

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