What is required to make a Dyson Tree a feasible space habitat?

Question

Inspired by this question about a fantasy World Tree, I thought I’d ask about the science fiction equivalent: a Dyson Tree. Dyson Trees are a living tree planted in a comet, which when fully grown is used as a space habitat.

The Terracide RPG includes Dyson Trees as part of the setting. They sound really cool in a visual and artistic sense, but my zoologist instincts are telling me that trees aren’t really designed to live in hard vacuum! For instance, to me a tree’s leaves look like flat, thin structures almost designed to radiate away heat and freeze solid, which won’t do the tree any good at all. To me a Dyson Saguaro Cactus seems a better shape!

However, my botany is minimal, so perhaps I’m missing something that Freeman Dyson thought of (I can’t track down his original description of Dyson Trees, so can’t check).

Is there any way to make Dyson Trees realistic enough to fit in with the rest of the (relatively hard sf) Terracide setting? What features would you have to genetically engineer into them? Why would someone choose to live in a space tree instead of a space station or asteroid colony (apart from for aesthetic reasons)?

Answer 1

Lets make the assumption that we are genetically modifying a tree from currently existing stock into some sort of incredible creature. Also, we will assume that photosynthesis would be the main energy source. So lets talk about some adaptations that you would genetically engineer.

Regarding the principles of tree operation, the leaf photosynthesis would not be able to occur in the normal fashion, because carbon dioxide is normally taken in through the leaves through stomate. So your tree will need to get carbon dioxide from somwhere else, and also exhaust the created oxygen somewhere else (i.e. not to space). This means the leaves should be sealed against the vacuum of space, preferably with a clear waxy film like some leaves already have. The trunk would also be sealed, and it shouldn't be too hard to make the necessary adaptation to the bark to accomplish this.

So for getting carbon dioxide and exhausting oxygen, the answer would be the root system. The roots already grab minerals and water, now they would have to absorb carbon dioxide as well. The roots could also exhaust oxygen. The danger here is that oxygen is highly reactive with alot of things, and can start fires. So all this exchange needs to happen in the roots, but the roots must be in something...like a comet.

Fortunately, comets are more or less the perfect material for feeding a tree. Our tree needs carbon dioxide, water, and a nitrogen source. Fortunately those are three of the most common comet materials (nitrogen being in ammonia). Mix those into a slurry held together by gravity and so far so good. The problem is that those three materials (carbon dioxide, water, ammonia) are not all accessible liquids at standard pressures. But at about 50 bar and ~275 K, all three materials would be liquids. 50bar is 5 MPa which is a lot of pressure, but not unbearable. For example, this is below the sustainable compressive, shear, and tensile pressure limits for several common hardwoods like ash, hickory, and oak.

Now for heat, space is cold, but vacuum is a pretty good insulator. One of the advantages of the tree's thicket of leaves is that much of the energy radiated out from the leaves in the infrared spectrum will immediately strike other nearby leaves and so not act as a net heat loss to the tree. I don't have enough information and math to say that this is sufficient, but if we combine a waxy insulating film and convective heat transfer from other warmer parts of the tree, then it could be possible to keeping water liquid as it transfers to the leaves.

Also of note for reducing heat loss, some trees like the fever tree can photosynthesize in their bark, so that would probably be a useful adaptation and could reduce the number of leaves needed. I imagine a tree like this would produce a thin layer of leaves facing the sun, and a moderately dense network of photosynthesizing branches supporting them, like this acacia.

As far as people living in this tree....yeah. That's the big problem. I don't see any answer to your last question (other than being space hippies).

Answer 2

Form follows function.

Early nanotechnology of “growing” invented machines and materials will be based on and informed by the example of living cells, and will heavily borrow many of the nanoparts they use. So Earth examples of an equivalent such as mining landfills may in fact be heavily engineered plants and fungi.

But suppose they can’t get adapted/modified plant cells to work in space on an asteroid, at all. Later generations invent de nono a “cell” based on different materials that are capable of living in that environment.

Well, the deployment will still look like a tree! You would need a microscope and chemical tests to determine that it’s unrelated to Earth (natural) life. Form follows function. You will need roots to probe the comet and extract molecules of interest and transport them back using a vascular system. You will deploy solar panels on a branching hierarchy of beams in a manner to optimize the light gathering and the logistics of growing and maintaining them.

You will have structural members holding both major systems together.

The leaves may not be green, and will not be shaped to shed water, but the layout will strongly remind you of how tree canopies look! Everyone will call it a “tree”.

Answer 3

Plants and animals right here on Earth have shown remarkable adaptability to extreme environments even to the point of microbes being sent into low Earth orbit list from Wikipedia Genetic engineering is in its infant stage, as is AI and robotics, even though we have come a long way, there appear to be huge leaps forward coming in the years ahead.

I believe power production should come from numerous sources. Space is not empty. It is full of a very plentiful and diverse array of usable materials that could be incorporated into such a ship. I think the ships could be programed here and sent far away to stellar nursery's as seedlings that are programmed to return here once they have fully matured like Salmon or other migratory creatures.

Once they have made the round trip and have powered up they may even have the kind of energy needed for near instantaneous travel by warping space with gravitational waves. The possibilities are truly endless!

This is a rough Sketch of something I thought I came up with, but it is actually an idea that has been around for a long time. It is a genetically engineered plant designed for deep space travel and possibly colonization, that is called a Dyson Tree after the scientist that put forth the possibility of creating these things some time in the far future.

It is engineered to protect the occupants from the perils of space and provide them with the necessities for life as they travel to distant worlds throughout the cosmos. That is one tripping tree!