Inspired by the various delightful "half-baked" and "dubious" design threads around here, I was casting about for a cool sci-fi design to put together. I've yet to come up with a spacecraft concept completely sui generis, but in terms of bringing ideas from science fiction literature to life, a thought hit me as while watering my (very humble) bonsai garden. The idea is to make a flying model of a spaceship found in the Hyperion Cantos, a floridly imaginative 4-novel series penned by Dan Simmons: a Knights Templar treeship, the Sequoia Sempervirens.
As envisaged, a treeship is a faster-than-light-capable spaceship with an oversized living coast redwood tree (sequoia sempervirens) as its main structure. While another treeship, the Yggdrassil, is also featured in the story, that one's name is a reference to another tree from legend, which happens to be a non-redwood species. For the purposes of this project, the literalist name Sequoia sounds right to me.
Here's some descriptive text from Hyperion (1995), chapter 5:
[Minor spoiler alert for Hyperion, if you'd like to be surprised by reading this part]
I'd encourage you to take a moment before scrolling onward to think up your own vision for what a treeship might look like.
Back outside of the realm of Simmons's imagination, though giant sequoias (sequoiadendron giganteum) are the most massive trees, coast redwoods are the tallest. In fact the tallest one currently known, topping 380 feet tall (and its location a poorly-kept secret), has been dubbed Hyperion. I'm not sure, but I imagine that rather than a reference to the Simmons book or the Keats poem that Simmons in turn referenced, it's in honor of the original bearer of the name, the Greek mythological titan.
About the project at hand, to set expectations for a moment: it's ambitious, and it might never happen. On its own, cultivating the coast redwood sapling I'm starting with into the right shape and size will likely take a few years of growth and occasional trimming. It will take cutting back existing branches without them dying, the tree growing more branches, the trunk thickening over time (which still won't be all that thick in that amount of time), etc. I'm not even that good at bonsai! Though I could build the rocket up front and let the tree "grow into it;" we'll see.
In any case, for this design, right off the bat I'm going to deviate from the "spherical" descriptor for the overall shape. I don't know whether it was the author's artistic license or just by mistake—it's alternately a common misconception that the crown of a fully-grown redwood tree is pyramid-shaped—but the more accurate geometry for an old-growth redwood tree would be cylindrical, with approximately equal-length branches sprouting from the upper half or two-thirds of the trunk, tapering at the very top. Which is quite convenient for making a model rocket! Meanwhile, to make a cylindrical "containment field" tree envelope, luckily clear plastic 2-liter soda bottles have pretty close to the right shape, strength, and weight.
So, here we go:
As shown it's 32" long, with a full-circle "fin span" to the tips of the feet of 19". Regarding the tree envelope, a Sprite 2-liter bottle has some nice molded-in sci-fi-esque shapes, which also help with stiffness, while a generic smooth soda bottle has a blunter top shape, which makes the nose design easier to work out. The nose, with the bottle cap secured inside, unscrews for access to the treetop trunk anchor. For the envelope disassembly joint at the base of the tree, I'm envisioning using tape to attach the bottle parts together, to allow ready access for tending to the tree as well as "re-potting" it. The bottom of a 2-liter soda bottle has five lobes, so naturally the rocket should have five fins. This will be good for landing stability, like an office chair's legs, as well as for fin area for flight stability. The balsa ring fin is structural, like an aircraft wing strut, so that the fins have enough strength even though they're surface-mounted.
The shock absorbers are canted outward only so far as will still allow them to compress during a perfectly vertical landing. If the air damping is too strong, I can poke a small hole in the side of each cylinder to increase airflow. Funny enough, the 10mm diameter paper core of a dog poop bag roll seems about the right size to make a piston.
In the rear ejection system, the piece of coupler tube is there to prevent binding as the motor spool exits the body tube. The current concept is that shock cord lines run from the nose anchors to the motor spool and then from there to three parachutes. The shock cords being draped over the ring fin pre-deployment hopefully will help pull the motor spool and parachutes out to one side as the parachutes unfurl, to avoid shock cord entanglement with the landing legs as the body swings around to descend feet-first. Quite the aerial ballet to orchestrate! And perhaps overly stressful on the 2-liter bottles. If it comes to it, I could ugly it up with reinforcing stringers down the inside of the envelope, attached to the stiffener rings.
Hmm, perhaps there's a better place to attach the shock cords than at the tip of the nose. Like maybe the front tips of the fin roots, since those are likely ahead of the CG.
Meanwhile, I think anti-tangle precautions rule out having trailing streamers per Simmons's vision. Too bad, such a detail would've been very cool.
The overall functional concept motivating this design is to try to keep forces on the tree in the positive g range, and not too high of g. That means build as light as possible, employ rear ejection to avoid negative g's, and try my darndest to land it upright. Calm weather flying only here. The really tricky part is that landing it on its feet would be helped by an aft CG, for which the weight of the dirt at the bottom end of the tree envelope helps, but which is obviously in conflict with proper flight stability. Meanwhile, adding nose weight isn't really an option due to the fragility of the soda bottles. If it ends up needing more stability, if increasing the already large fin area isn't effective enough due to the short distance to the CG... the only option left would be to lengthen the motor tube section. Which again makes it harder to land upright. Plus it would take away from trying to make the tree be visually dominant. This isn't supposed to be just payload rocket that happens to have a tree in it, it's supposed to be a treeship. So, getting decent CG and CP location estimates before it's built will be critical. If not by simulation, maybe I should prove it out with a smaller-scale model in a homemade wind tunnel? Haha...
Finally, I'm disinclined to go overboard on detailing, especially given weight constraints, but also not to clutter it visually. Especially since the model is about 1/1250 scale! That said, it is tempting to have some fun with making passenger and crew accommodations. There'll have to be at least a little on there, dwarfed by the "great bulk" of the redwood tree.
As envisaged, a treeship is a faster-than-light-capable spaceship with an oversized living coast redwood tree (sequoia sempervirens) as its main structure. While another treeship, the Yggdrassil, is also featured in the story, that one's name is a reference to another tree from legend, which happens to be a non-redwood species. For the purposes of this project, the literalist name Sequoia sounds right to me.
Here's some descriptive text from Hyperion (1995), chapter 5:
[Minor spoiler alert for Hyperion, if you'd like to be surprised by reading this part]
I'd encourage you to take a moment before scrolling onward to think up your own vision for what a treeship might look like.
Back outside of the realm of Simmons's imagination, though giant sequoias (sequoiadendron giganteum) are the most massive trees, coast redwoods are the tallest. In fact the tallest one currently known, topping 380 feet tall (and its location a poorly-kept secret), has been dubbed Hyperion. I'm not sure, but I imagine that rather than a reference to the Simmons book or the Keats poem that Simmons in turn referenced, it's in honor of the original bearer of the name, the Greek mythological titan.
About the project at hand, to set expectations for a moment: it's ambitious, and it might never happen. On its own, cultivating the coast redwood sapling I'm starting with into the right shape and size will likely take a few years of growth and occasional trimming. It will take cutting back existing branches without them dying, the tree growing more branches, the trunk thickening over time (which still won't be all that thick in that amount of time), etc. I'm not even that good at bonsai! Though I could build the rocket up front and let the tree "grow into it;" we'll see.
In any case, for this design, right off the bat I'm going to deviate from the "spherical" descriptor for the overall shape. I don't know whether it was the author's artistic license or just by mistake—it's alternately a common misconception that the crown of a fully-grown redwood tree is pyramid-shaped—but the more accurate geometry for an old-growth redwood tree would be cylindrical, with approximately equal-length branches sprouting from the upper half or two-thirds of the trunk, tapering at the very top. Which is quite convenient for making a model rocket! Meanwhile, to make a cylindrical "containment field" tree envelope, luckily clear plastic 2-liter soda bottles have pretty close to the right shape, strength, and weight.
So, here we go:
As shown it's 32" long, with a full-circle "fin span" to the tips of the feet of 19". Regarding the tree envelope, a Sprite 2-liter bottle has some nice molded-in sci-fi-esque shapes, which also help with stiffness, while a generic smooth soda bottle has a blunter top shape, which makes the nose design easier to work out. The nose, with the bottle cap secured inside, unscrews for access to the treetop trunk anchor. For the envelope disassembly joint at the base of the tree, I'm envisioning using tape to attach the bottle parts together, to allow ready access for tending to the tree as well as "re-potting" it. The bottom of a 2-liter soda bottle has five lobes, so naturally the rocket should have five fins. This will be good for landing stability, like an office chair's legs, as well as for fin area for flight stability. The balsa ring fin is structural, like an aircraft wing strut, so that the fins have enough strength even though they're surface-mounted.
The shock absorbers are canted outward only so far as will still allow them to compress during a perfectly vertical landing. If the air damping is too strong, I can poke a small hole in the side of each cylinder to increase airflow. Funny enough, the 10mm diameter paper core of a dog poop bag roll seems about the right size to make a piston.
In the rear ejection system, the piece of coupler tube is there to prevent binding as the motor spool exits the body tube. The current concept is that shock cord lines run from the nose anchors to the motor spool and then from there to three parachutes. The shock cords being draped over the ring fin pre-deployment hopefully will help pull the motor spool and parachutes out to one side as the parachutes unfurl, to avoid shock cord entanglement with the landing legs as the body swings around to descend feet-first. Quite the aerial ballet to orchestrate! And perhaps overly stressful on the 2-liter bottles. If it comes to it, I could ugly it up with reinforcing stringers down the inside of the envelope, attached to the stiffener rings.
Hmm, perhaps there's a better place to attach the shock cords than at the tip of the nose. Like maybe the front tips of the fin roots, since those are likely ahead of the CG.
Meanwhile, I think anti-tangle precautions rule out having trailing streamers per Simmons's vision. Too bad, such a detail would've been very cool.
The overall functional concept motivating this design is to try to keep forces on the tree in the positive g range, and not too high of g. That means build as light as possible, employ rear ejection to avoid negative g's, and try my darndest to land it upright. Calm weather flying only here. The really tricky part is that landing it on its feet would be helped by an aft CG, for which the weight of the dirt at the bottom end of the tree envelope helps, but which is obviously in conflict with proper flight stability. Meanwhile, adding nose weight isn't really an option due to the fragility of the soda bottles. If it ends up needing more stability, if increasing the already large fin area isn't effective enough due to the short distance to the CG... the only option left would be to lengthen the motor tube section. Which again makes it harder to land upright. Plus it would take away from trying to make the tree be visually dominant. This isn't supposed to be just payload rocket that happens to have a tree in it, it's supposed to be a treeship. So, getting decent CG and CP location estimates before it's built will be critical. If not by simulation, maybe I should prove it out with a smaller-scale model in a homemade wind tunnel? Haha...
Finally, I'm disinclined to go overboard on detailing, especially given weight constraints, but also not to clutter it visually. Especially since the model is about 1/1250 scale! That said, it is tempting to have some fun with making passenger and crew accommodations. There'll have to be at least a little on there, dwarfed by the "great bulk" of the redwood tree.
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