NASA NIAC (NASA Advanced Innovation Concepts) has 2022 grants. It is a bit confusing as some of the projects have been written about before. This makes sense for phase 2 projects but there is a phase 1 project that has previously had work. Nextbigfuture covered this proposal six months ago.
The Atomic Planar Power for Lightweight Exploration (APPLE) is a low mass, high-reliability spacecraft power architecture that merges the extensive heritage of radioisotope power generation with a radiation-hard battery in an integrated modular system which can enable a wide range of vehicle and mission designs. A modular power architecture will open up the design space for space vehicle bus by enabling power designs to fit the mission for any vehicle shape or size, from 10’s of Watts to kilowatts.
APPLE uses small 238PuO2 (plutonium) tiles coupled to high efficiency thermoelectric devices joined to a thermal radiator that also serves as a 5Wh solid state radiation hard battery in a 10 x 10 x 1.7 cm tile. The unoptimized current design device is estimated to produce at least 1.2 We and last at least 15 years (238Pu half-life is 87 years). Moreover, in addition to power generation this power tile can be placed on the vehicle surface to provide heat for internal components or in a dual-sided configuration on a boom-type extension to provide more power (~2 We/tile). The Atomic Planar Power for Lightweight Exploration is an enabling architecture for solar system exploration with low mass vehicles. This proposal will develop an advanced vehicle power architecture that integrates lightweight radioisotope power with robust, radiation hard energy storage in a modular, scalable power system, demonstrate APPLE full system power generation and storage function. This proposal will then design deep space vehicle bus and mission plan for Solar Gravity Lens based on the APPLE architecture.
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I get what you're saying, but the radiation we're talking about, including cosmic rays, is so penetrating that shielding is basically a non-starter if you have any weight constraints at all.
What they'd have to do is make the components more radiation resistant.
I'm curious whether it's the power conversion, or the integrated battery, that is degrading first. Vacuum capacitors have a lot of potential for extremely radiation resistant storage, and could be directly charged by an alpha emitter.
Hm… If they used some kind of scintillator and photovoltagic diode, they would not need to place the tiles on the "outside" to radiate away the heat. And they could hence use a radiation shield to increase the longervity. Plus, the power level would not be proportional to the surface, but rather the volume. I.e. better scaling.
It's a matter of accumulated radiation damage. Not from the Pu, but from being out in space.
They did say that the current design isn't optimized in that regard.
Why would the system last only 15 years? 238Pu half-life is 87 years..? So you could make it last a lot longer, from the perspective of isotope power, at least…
Grams per watt would be power density, not energy density. Or rather the inverse of power density. The power density would be 0.005W/g, not terribly high, but I guess pretty decent for an isotopic battery. Energy density works out to about 650Wh/g, about 9,000 times that of a lithium ion battery.
Not your error, obviously, it's in their graphic.