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Chinese astronauts make rocket fuel and oxygen in space

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298 points Teever | 8 comments | 24 Aug 25 17:54 UTC | HN request time: 0s | source | bottom
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kevinmershon ◴[26 Aug 25 22:09 UTC] No.45032976[source]▶
> This is a similar reaction to photosynthesis in plants, which produces glucose instead of rocket fuel.

This is silly, but also begs the sillier question why we aren't bioengineering plants to produce rocket fuel

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andrewflnr ◴[26 Aug 25 22:20 UTC] No.45033082[source]▶
Why aren't we engineering plants to produce automotive fuel? We ought to at least be able to do diesel.
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philipkglass ◴[26 Aug 25 22:30 UTC] No.45033153[source]▶
Plants have very low sunlight conversion efficiency compared to solar farms. If you need chemical fuel instead of electricity, it would still be more efficient to use solar electricity to turn carbon dioxide and water into simple liquid fuels like methanol (usable in spark ignition engines) or dimethyl ether (usable in diesel engines).
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andrewflnr ◴[26 Aug 25 23:00 UTC] No.45033386[source]▶
> Plants have very low sunlight conversion efficiency compared to solar farms.

Measured how? If nothing else, they seem to be good at carbon capture. And I don't see how you it could account for engineered for plants engineered to store more of their energy as oil.

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philipkglass ◴[26 Aug 25 23:20 UTC] No.45033543{3}[source]▶
Measured by the fraction of incident sunlight that gets transformed to usable energy. Solar farms generate about 30 times as much power per hectare as corn farms, assuming that you can use electricity directly:

"Ecologically informed solar enables a sustainable energy transition in US croplands"

https://www.pnas.org/doi/full/10.1073/pnas.2501605122

As a rough estimate, you'd lose 2/3 of that energy if the electricity had to be turned into liquid fuels. That would still mean 10 times greater usable energy produced per acre.

Plants genetically engineered for fuel production might be somewhat more efficient in the future, but future solar farms are also probably going to be more efficient.

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1. mikeyouse ◴[26 Aug 25 23:37 UTC] No.45033675{4}[source]▶
For anyone wanting to learn more - the holy grail of Ag engineering would be to increase the efficiency of rubisco, which is the rate-limiting enzyme in photosynthesis - so understandably there’s a ton of research at doing just that.

https://en.m.wikipedia.org/wiki/RuBisCO

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2. murderfs ◴[27 Aug 25 01:45 UTC] No.45034545[source]▶
A somewhat less (but still!) ambitious project is to retrofit C4 photosynthesis into rice. It's something like 50% more efficient, and has evolved independently dozens of times, so it's probably a lot more feasible.
3. rendaw ◴[27 Aug 25 04:24 UTC] No.45035447[source]▶
Why do we need more efficient photosynthesis in plants? Is it for indoor cultivation?
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4. melagonster ◴[27 Aug 25 06:32 UTC] No.45036107[source]▶
Plants get more energy, so they generate more food.
5. JumpCrisscross ◴[27 Aug 25 08:53 UTC] No.45037030[source]▶
Strongly recommend for one of the light-dependent reactions from before that enzyme: https://youtu.be/WhCczIqADuI
6. mikeyouse ◴[27 Aug 25 12:47 UTC] No.45038924[source]▶
If you had a widely applicable improvement, you’d be able to grow fruit trees in Canada or have two harvests in one season for food crops, or grow much denser species of wood, much more quickly for construction lumber. It would be massively world changing — but it is a 4 billion year old enzyme so is pretty entrenched..
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7. rendaw ◴[27 Aug 25 13:56 UTC] No.45039758{3}[source]▶
Oh interesting! Is photosynthesis the main thing limiting growth speed?

I would have expected there to be multiple processes with similar or aligned timings, or some built in limiting mechanism or something... it's not like giving humans higher calorie food makes them become adults faster.

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8. mikeyouse ◴[27 Aug 25 16:45 UTC] No.45041998{4}[source]▶
Improving rubsico would be more along the lines of improving your metabolism so that you can process 4,000 calories per day with the loose analog of supplying more CO2 being the ‘higher calorie food’. It’s the single largest bottleneck in photosynthetic efficiency. TBH, it would likely take several more breakthroughs for plants to make use of an improved rubisco but it’s still a massive target for ag research.