Biological Rocketry and Spaceflight on a 1/100 scale Planet.

[Whirligig Girl]

Imagine you have a world like THIS, 1/100 the scale of Earth. 6 Kilometer Radius. Would it be possible for biological creatures in such a world to evolve the capability to orbit their little world? Let's imagine it's based upon a hypothetical robot-controlled experiment which artificially selects for this type of thing. Perhaps it starts with a species of bird.

Could a creature hypothetically come into being which could-of it's own accord-fly into orbit around it's planet? (Note that the point of this thread isn't about trying to ask whether such a thing is possible, but rather to explain how it might be possible. Basically, I want this, and I want it to be as realistic as possible given the unrealistic setting. The atmosphere isn't a problem in this hypothetical universe. Same as it isn't on Kerbin.)

Let's take a little look at the facts.

-The Delta-V to orbit for a largeish scale rocket in this world is about 1200 meters per second. The size matters, because a smaller object has more air resistance. This is why super-duper-tiny rockets aren't found on Earth, even though strictly speaking you could scale down a rocket and keep the same delta-v.

-Orbital Velocity is about 750 m/s

-Biological photovoltaics is possible. This could mean that a creature could drink a very large amount of water and then convert that into hydrogen and oxygen. But the Isp of a gaseous hydrogen-oxygen rocket is horrible. Perhaps a Methane-Gas Air-breathing Jet engine could push a creature to perhaps 50% of orbital velocity, and then it could use some other source to push it the rest of the way.

-Biological matter is notoriously flammable, so that might be a problem! But, as the saying goes, "life will find a way."

-The fastest Earth Bird can go about 83 meters per second. Orbital velocity is about 9 times that.

Let's assume the creatures have a subaverage human-level intellect (Neanderthals, perhaps?), which would allow them to think, use tools, and do a whole lot of social stuff. Perhaps you could find a group of Rocketcreatures who have decided they want to go to their moon, so they try and use all the resources they have to get someone into space with the resources to push forwards to the Moon!

Edited December 22, 2014 by GregroxMun

[SmartS=true]

You seem to ignore the fact that they probably would not have spacesuits...

[Bill Phil]

Umm... 1/100 Kerbin? Because 1/100 Earth is 60 km...

[lajoswinkler]

No, it could not be even possible, because of vacuum. Vacuum is absolutely hostile to the basics of life as a special kind of process. That's where the story ends.

[kerbiloid]

Atmospheric scale height H = RT/mg.

If we presume these creatures' biology similar to Earth one, "T" and "m" would be almost the same.

R = const.

The only variable is "g".

If presume, "g" is close to 9.81, the scale height would be the same 8 km, as on Earth.

Density ~ exp(-h/H), so the atmosphere thickness would be the same 100 km.

So, we get a 50..200 km diameter air ball with a 5 km stone ball inside.

[Bill Phil]

What distance does it assume "g" is at in that equation?

[Ralathon]

Assuming you handwave away all the physics problems with such a planet;

- It must have a density 30 times that of depleted uranium to maintain 1G.

- Such a low escape velocity means the atmosphere will bleed into space very quickly.

And also handwave the biological problems;

- Such a small surface area makes it unlikely for life to arise.

- Small surface area means you'll have only a small number of niches.

- A small planet is much more unstable than a big one. So life is likely to snuff itself out.

- A small planet takes in much less energy, thus it cannot support complex super predators like lions or tigers.

You are left with the problem of providing evolution a stimulus to develop rocketry. Evolution can't look forward and engineer for its goal. Fortunately you can easily imagine several paths towards biological rocketry. One example from the top of my head:

Say you start with a species like the bombardier beetle, one with a chemical defense mechanism. Due to evolutionary pressure and random chance the predator feeding on these beetles and the beetles get in a biological arms race. The beetle produces an ever more potent reaction while the predator becomes more and more immune to it. At some point the beetle has such a strong reaction that it can use it as propulsion mechanism to fly away from the predator. This becomes the new focal survival strategy of the beetle and you're left with a rocket propelled beetle.

The next step: long, sustained rocketry and orbital flights is a bit harder to imagine. There isn't really anything up there that life would want. The only resources life could exploit in orbit are unfiltered sunlight and safety from all predators. Sunlight is not exactly a premium resource that life wants. Plants only use a very small fraction of the sunlight they receive thanks to overheating problems. So it is hard to imagine any species migrating to orbital heights for light unless the entire atmosphere is saturated with dense airborne algea or something.

Long sustained rocketry is also very expensive from an energy PoV, so the payoff has to be really good. Safety might be able to do it, but I imagine evolution would take a different route. Not to mention that an organism with a lot of delta V has to be large, and thus has less natural predators.

If anyone is able to conjure up a reason for evolution to push towards orbital flight I'd like to hear it.

[kerbiloid]

What distance does it assume "g" is at in that equation?

I presumed that the topic starter means Earth-like life forms, so if the same "g" and the same air pressure are on planet surface, the more-or-less same atmosphere thickness you will get above.

Somewhat less because gravity will decrease faster due to greater height/radius ratio.

[Bill Phil]

Hmm... Are you talking about a different G value, OP? That'd be the only explanation...

Anyhow, I mean that some equations have assumptions involved with distances and whatnot. Because 1g is only experienced at a certain distance from Earth's point-mass, and in this mini-planet scenario would be much closer.

[magnemoe]

Thinking of Nivens stage trees, basically trees who also was an solid fuel rocket. Yes they was an constructed species, not natural however they used the rocket for spread seeds.

[Whirligig Girl]

Umm... 1/100 Kerbin? Because 1/100 Earth is 60 km...

1/100 Earth is what I said. The link goes to 1/10 scale Kerbin.

- - - Updated - - -

Hmm... Are you talking about a different G value, OP? That'd be the only explanation...

Anyhow, I mean that some equations have assumptions involved with distances and whatnot. Because 1g is only experienced at a certain distance from Earth's point-mass, and in this mini-planet scenario would be much closer.

Not Earth mass, not Earth density. It's fine tiuned so that it's at 1g at the surface. That's how hypothetical rescales of planets work.

[Whirligig Girl]

If anyone is able to conjure up a reason for evolution to push towards orbital flight I'd like to hear it.

Look at the OP. I say there is some A.I. Controlled artificial selection process pushing for this.

[Whirligig Girl]

No, it could not be even possible, because of vacuum. Vacuum is absolutely hostile to the basics of life as a special kind of process. That's where the story ends.

http://en.wikipedia.org/wiki/Tardigrade

Hold your breath.

[Whirligig Girl]

Thinking of Nivens stage trees, basically trees who also was an solid fuel rocket. Yes they was an constructed species, not natural however they used the rocket for spread seeds.

These are the coolest trees I ever heard of in Sci-Fi. Thank you.

[lajoswinkler]

http://en.wikipedia.org/wiki/Tardigrade

Hold your breath.

I see the stupid disinformation has spread around like a meme.

Tardigrades can not live in vacuum. If exposed to it, they will go into some sort of hibernation. They shrivel and stop doing what they do.

As days pass, chances of a successful "reviving" drop. IIRC they reach practical zero after more than a week.

So, no. No life in vacuum.

[Whirligig Girl]

I see the stupid disinformation has spread around like a meme.

Tardigrades can not live in vacuum. If exposed to it, they will go into some sort of hibernation. They shrivel and stop doing what they do.

As days pass, chances of a successful "reviving" drop. IIRC they reach practical zero after more than a week.

So, no. No life in vacuum.

Well, to be fair, Tardigrades didn't evolve a need to survive in a vacuum. If evolution has a need for it, and because of the A.I. control, it doesnt, then these creatures must evolve Vacuum Protection. Space suits can do it, why can't an animal for just 13 minutes? (Orbital period around the planet)

[NERVAfan]

The scenario as given isn't limited to natural evolution, so yeah, I think active life in vacuum is quite possible... for a while anyway.

The main reason conventional Earth life can't survive in vacuum is that a) it needs to breathe and as part of that need to breathe, the lifeform is constantly "open to" the surrounding air or water, so when exposed to vacuum, it loses what it does have (in the case of a human, not only are you not getting any new oxygen, you actually lose oxygen).

So a living thing that could close itself out from the ambient environment (IE airtight shutters over eyes/nose/mouth/etc equivalents) could survive and be active... until its stored oxygen (or whatever it uses, for an anaerobic species) runs out. (This could be quite a while, some whales can go over an hour on air stored in their lungs, and I think some underwater reptiles may be able to go even longer...)

There are other secondary problems but with the same level of 'directed evolution' that could be handled too.

UV exposure is probably the worst ... have the outermost level of skin and the 'shutters' be opaque to UV and made of non-living tissue, like hair or bark, so the skin isn't itself killed.)

Pressure difference... I'm pretty sure a tough skin could be developed that could hold at least 1atm pressure difference... proteins can be very strong (eg spider silk). Human skin exposed to vacuum doesn't actually rupture, just swells up hugely (though lung tissue can rupture... that's why you need the shutters). If our skin was reinforced with a web of thick spider-silk-protein strands every tenth of a millimeter or so...

(Also, you could probably get away with an internal pressure much less than 1atm... birds can fly very high, and they've got to be pretty much equalized with the outside pressure. A Ruppell's vulture collided with an airplane at 37000 feet, and the pressure there is ~0.21 atm.)

Edited December 23, 2014 by NERVAfan
remove pointless asterisk

[NERVAfan]

I see the stupid disinformation has spread around like a meme.

Tardigrades can not live in vacuum. If exposed to it, they will go into some sort of hibernation. They shrivel and stop doing what they do.

As days pass, chances of a successful "reviving" drop. IIRC they reach practical zero after more than a week.

So, no. No life in vacuum.

I think "disinformation" is harsh. It's a case of the distinction between "survive" vs. "live actively" getting lost when the research gets publicized.

That distinction is pretty common. E.g. for hyperthermophiles they distinguish between the temperature it can grow and reproduce at, and the temperature at which it merely survives.

(But, as GregroxMun says, no Earth lifeform is adapted for surviving vacuum - tardigrades are just using the same mechanism they use to survive desiccation etc., IIRC. No living thing could live entirely or indefinitely in vacuum since it would have no way of replenishing its resources, but temporary active life is probably possible with enough selective pressure or genetic engineering.)