Could a microbe plausibly generate lift gas for manned balloon flight?
QUESTION
I was thinking about ways of justifying practical balloon flight for a pre-industrial civilization, when I remembered that some microorganisms produce methane, and better yet, hydrogen.
This made me wonder, is it plausible to posit a hydrogen creating microbe that could produce enough lift gas to refuel a balloon, even in midflight?
NOTES
A balloon craft in this scheme would keep a lightweight fuel tank attached to the envelope by a hose. The tank would be filled with microbes and their food (hydrocarbons, biomass, whatever it is that they like to eat). The microbes then produce hydrogen gas. To rise, you throw in more fuel. To descend, you release some hydrogen. Depending on the fuel source that the microbes eat, trading towns might also farm wells full of the microbes where smaller balloons could fill up.
Now on to the potential problems:
First, I don't know if any organism could realistically produce the required volume of hydrogen gas. I know that a hydrogen balloon lifts about 68 lbs per 1000 cubic feet. I also know that the efficiency of methanogensis (which is the best example I've got for hydrogenesis) can be quite high, and I've seen numbers ranging from 20% to 80%. But even with some kind of awesomely efficient microbe, from there I have no idea how to calculate the cubic feet of hydrogen that could be derived from a given fuel source.
Second, though less important, I also don't know if any microbe could physically generate gas fast enough to allow for reasonably controlled changes in altitude.
Third, even if all of that (literally) flies, I need to make sure there's a reason these microbes don't get loose and just eat up all the fuel outside the tank.
Finally, this question may end up being pretty important to the world I'm working on right now, so if it ends up being more complex than a straightforward "no" then I'll also offer a thank-you bounty to anyone that gives me an especially in-depth answer.
BOUNTY EDIT: Bounty goes to Dubukay. In general this question received many high-quality answers, so thanks everyone!
This post was sourced from https://worldbuilding.stackexchange.com/q/103752. It is licensed under CC BY-SA 3.0.
1 answer
So the first question. If the microbe doesn't have to exist on Earth already, then there is no reason for it to not be possible.
Just say that this super microbe does exist, and when combined with other methods like a catalyst of some kind (like nickle for instance), is able to produce enough gas to make it possible.
Another possibility is that the organism works slowly, but the gas builds up over time. So say to fill a new balloon up to pressure takes a couple weeks, but if you keep putting in resources then the microbe will just keep producing and keep the balloon topped off. This option would require a material that holds the gas really well.
Second, there are other possible ways to control changes in altitude other than venting. If you compress the lifting gas then it will be less buoyant, and so you will go down. you could put a balloon inside of the balloon, and pump the inner balloon up with air when you want to descend.
As to the third question, this is a bit trickier. As a wise man once said "Life, uh, finds a way."
There are several self limiting mechanisms that could be used.
- The microbe has a natural microbe predator that keeps it from getting out of control in the wild. It could be another microbe, some kind of algae, etc.
- There is a compound in raw fuel that hinders the microbe that isn't present in refined fuel or something is added to the refined fuel that gives the microbe a boost. This could also act as a catalyst.
- The microbe has a genetically fixed colony size that is large enough to be used in a gas production system, but not large enough to cause problems in the wild.
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