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Erinalope t1_j1c87g4 wrote

Reply to comment by Lafuente_Astro in NASA astronauts unfurl 4th solar array outside space station by IslandChillin

Yes, the iROSA, improved rollout solar arrays. They attach to the old motors and fill in some of the empty space.

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IWasGregInTokyo t1_j1do7ky wrote

Wondering how efficient they are compared with the much larger original arrays. I'm assumng there's been some improvement in the years since the originals were installed.

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danielravennest t1_j1erg85 wrote

30% vs 12% in the original arrays when they were new. That's why the new ones are so much smaller.

The Space Shuttle ran off fuel cells, which meant a limited time on orbit. They had a goal of 30 day science missions, so a project was started for a "Power Extension Package" that had fold-out solar arrays.

That never flew on the Shuttle, but when the Space Station project started in the 1980's, it was adapted for the Station's main solar arrays. State of the art at the time was 12% efficient silicon cells.

Current state of the art are Gallium Arsenide + two other layers to capture more of the solar spectrum. So new satellite arrays get ~30% efficiency. Multi-layer cells are mostly too expensive for ground use, but silicon has been constantly improving, to where panels on Earth can convert up to 20-22% of incoming sunlight today.

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AWildDragon t1_j1dwa0g wrote

That and degradation of the old ones due to space exposure.

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Erinalope t1_j1dz42a wrote

I think I remember them being marginally more efficient, but all solar arrays start losing efficiency at first light, especially in the harsher environment of space. They’ll be way more powerful just by being newer.

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danielravennest t1_j1ernmg wrote

See my other comment in this chain. New space solar is 30% efficient, compared to 12% for the old Station arrays when new. That's why the new roll out arrays can be so much smaller.

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