# What is the most optimal thruster placement in a planet-sized creature?

As a follow-up to my previous question, I spoke about an anomalous planet-sized serpentine creature that lives in space and how close it could get to earth. However, while developing the thing, I ran into the problem of movement, since, while this thing takes clear inspiration from sea life in the classic space whale trope, it can't exactly rely on fins or flippers to travel through space.

The obvious solution to the mobility problem is to use thrusters instead, but in having problems figuring out where exactly said thrusters should be on the creature. Being something that actively roams throughout space, it needs to be able to travel and move in 3 dimensions, and so I originally pictured it having several groups of thrusters throughout its body, layed in groups of 3 with a roughly equal distance between each thruster, but I'm not certain what the optimal thruster arrangement would be to enable that kind of movement in something of such size, especially since, unlike a rocket, this thing is flexible and able to "bend" itself around like a normal living organism normally would.

If it makes it easier to picture, assume the creature's body plan and proportions (minus the flippers and tail fin part) to be roughly the same as those of a scaled up basilosaurus.

art by Harry-the-Fox on deviantart

Given what it needs to do and it's cylindrical serpentine-like body plan, what would be the optimal arrangement of thrusters in this planet-sized creature's body in order for it to move around through space? would the "thruster" placement more common in modern rockets (closer to the nose and near the back of the ship) still be the most effective despite the creature's more flexible nature or would other arrangements work better in such a situation?

In case it's important, recapitulating from the previous question: It's length is approximately 250000 km, it weights around $$6,25 \times 10^{26}$$ kg, the tissues its made of have a density of roughly 100000 $$kg/m^{3}$$, and its weight is distributed fairly equally throughout its body. The creature is also an "anomaly", something that "naturally" violates certain laws of our universe, so the problems that should normally arise regarding its structural integrity and matters related to fuel, nutrition and other matters related to living organisms and the square cube law are not a concern that needs to be addressed.

I'm mostly looking for what would be best in terms of number, size and placing of the thrusters in order for the creature to be able to move around effectively through the void of space in 3 dimensions.

• If it's planet sized then the physics involved with objects of that mass dictates that it shall by necessity also be planet shaped, so, that will be round then, so put it where you want, it will all look the same (for a given value of same) at any adequate distance to view the entire critter anyway. Dec 6, 2021 at 17:58
• Sorry, I've added the explanation to this question as well. The creature is an "anomaly", something whose existance violates certain laws of our universe, that's why it's not a concern in this specific scenario. Thank you for the heads up. Dec 6, 2021 at 18:37
• @ProjectApex there was already a lot of handwaiving regarding this beast, in an earlier question.. which was also supposed to be science based. Now, you want to add thrusters to it ? advanced aliens inhabit the beast ? Why not let it sail around the sun, like comets do.. I don't know your storyline, but the above Saurus is an animal, not a space ship. Evolution can't provide "thrusters" and fuel. Dec 6, 2021 at 19:14
• @Goodies I am aware of how implausible it is. I say it's science based because I want it to actually have a more realistic impact on its surroundings. The creature's existance violates several laws, but that is not to say I wish it to violate every law in our universe. I do however want it to be able to actively move on its own. I call it a creature for a lack of a better term, as it's not exactly an animal, or something that evolved naturally into being, but not exactly a machine either. Dec 6, 2021 at 19:39
• Come to make a joke, u know it, but I have to say, it won't be that easy to make a good setup for such creature, starting from u underestimate what it means and what it takes to flex such mass/size. But it not impossible and if u manage to make it good it could be quite epic, so wish u luck and patience. Dec 7, 2021 at 0:59

Since it's a relatively flexible thing, I'll suggest having the majority of the thrusters be at the front as a pulling or towing mechanic to drag along the entire length of its mass to wherever the head is pointing. It'd also make for a nice frill or mane of thruster fire if you're into that sort of thing. Might also end up looking sort of like a comet if the thrusters shrink in size as they go back.

Some minor thrusters will be required along the length of the body to minimize tension, sheer, bending, and torsion stresses and to make it seem more like it's 'swimming' through space if that's your intension.

Thrusters at the way back will be useless for a flexible object, unless you mean for it to have the ability to reverse but it may be more efficient for it to simply focus all of its power into forward motion and turning its head if it does want to go back somewhere.

• or exactly reversed. the way you suggested, when going towards something it would have its thrusters pointing away from it during the last hours of the chase. Dec 6, 2021 at 18:53
• @PostlimFort How so? The thrusters will be at the front but pointing backwards... I don't know how you could see it has having its thrusters pointing aware from whatever it's chasing Dec 6, 2021 at 19:22
• at first it would burn towards what it is chasing but to avoid slamming into it at high velocity it would be burning away. high velocity as in bullets from an high velocity rifle or faster. not the the snails pace of a car on the highway. that is just how things realistically move in space. (check out orbital mechanics if you would like to learn more) Dec 6, 2021 at 20:32
• @PostlimFort If it has the durability to not collapse in on itself from its sheer size alone(anomalous though the nature of the durability may be), it's not going to be concerned with a collision against basically anything, since its whole structure behaves like a solid at its scale when everything else in the universe essentially acts like a liquid at celestial object scales. Its ability to not get absolutely shredded by high speed space dust collisions alone is a testament to this. Dec 6, 2021 at 23:26

Far back, on the tail.

I am considering a jet pack. When wearing a jet pack you want all of your protuberant appendages to be well out of the way of the exhaust of the jet pack. A long floppy creature or appendage is at risk of being hit by the exhaust if the pack / thruster is mounted at some point forward. The least risk would be if the pack or thruster is as far aft as it can be placed.

For that reason my jetpack has attached foot placements (actually some old Crocs) on top of it, to keep the exhaust pointing well away from the rest of me. Your long floppy creature should have its exhaust coming from the tip of its tail. For reversing direction, the creature can bend in a C and point the tail forward. Hopefully it is not so flexible that it bends more than a C and points the thruster at its own head.

• We all come with an in-built thruster, near our tailbone, capable of expelling solid or gaseous propellant. The output is rarely so hot as to be damaging to one's legs, but most people try to keep their legs clear anyway. A snake/fish creature doesn't have legs, though... Dec 7, 2021 at 18:13
• @Jedediah I will testify on behalf of my people-food stealing elderly dog that creatures with elongated tailbones are even more likely to soil those with ""propellant" than they are their legs. Dec 7, 2021 at 19:42

It probably isn't optimal, but replace the fins with thrusters. If those fins were adapted for quick movement through the ocean it would be reasonable to assume that thrusters placed in the same location would grant quick movement through space.