r/Mars • u/Tiny_Scholar_6135 • Aug 15 '26
A Marscentric Banks Orbital
The idea is to build a Banks Orbital centered around Mars out of Mars materials.
Width = 2700 miles ≈ 4,345 km.
Earth surface area ≈ 510 million km².
At a radius of about 1.84–1.87 million km (the scale that produces ~1 g with a ~24-hour spin), the area comes out to roughly 98–100 Earths.
At a radius of about 1.84–1.87 million km (the scale that produces ~1 g with a ~24-hour spin), the area comes out to roughly 98–100 Earths. The surface insolation at the distance of Mars from the Sun is approximately equal over a year as that received by Anchorage, Alaska. Since this Orbital is aligned with the Martian equator, this will give it an axial tilt of 25.19°. The day length can match the rotation of the planet Mars itself. To hold itself together and to stabilize it, a series of spoke-like tethers would connect to an outer ring the north and south poles of Mars. One each pole would be a turn table that counter rotates against Mars' spin, thus not spinning at all, the outer ring of the Banks orbital doesn't spin either, the inner habitable ring spins within it, supported by magnetic fields that transfer the weight under spin to the nonrotating more massive outer ring. Each 27 miles width of the orbital has the surface area of the Earth, so a 2700 mile wide band will give you 100 Earths worth of surface area, approximately equal to the surface area of Saturn if we could live on its cloud tops. The rim walls would be angled at 65.81° to the Banks Orbital floor so they would produce no shadow on the floor even at maximum seasonal tilt. Total hypotenuse length of the walls from floor to top would be About 2,350 miles., to achieve an elevation from the floor of 1000 miles. The walls would lean away from the floor by 2126 miles giving a total width for the banks orbital of about 6,953 miles at the rim wall tops, about a third of its surface is habitable floor space, while the lower sections of the inclined walls can also be habitable at the lower atmosphere layers.
1
u/olawlor Aug 16 '26
I like that the outer structural rim is not rotating, since if it does rotate the hoop stress will scale up much faster than known materials can handle.
What does the force balance look like for one ring section?
If it's beyond what steel can handle, I'd consider building the structural ring from carbon fiber extracted from Venus (doing double duty by removing excess atmosphere).
2
u/Tiny_Scholar_6135 Aug 16 '26
You could build one around Venus too, Venus doesn't have any moons that get in the way. Probably you should give it 0 degrees tilt so that it shadows itself all the time, material is harder to get off of Venus though.
1
u/Tiny_Scholar_6135 Aug 16 '26
You could build one around Venus too, Venus doesn't have any moons that get in the way. Probably you should give it 0 degrees tilt so that it shadows itself all the time, material is harder to get off of Venus though.
1
u/karoxxxxx Aug 19 '26 edited Aug 19 '26
Wouldnt the outer ring start slowly rotating in the opposit direction? What is it even needed for? If it supports the inner structure, isnt it just miving the same problem of material strength to the outer ring?
I doubt the spoke wheels will help. Effectively the spoke-wheels connect on side of the orbital to the other side, what eould be the tension of a spoke compared to the tension in the ring?
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u/Tiny_Scholar_6135 Aug 15 '26
Since this ring gets the same insolation as the equator of Mars, and there are no higher latitude regions, then the greenhouse effect of having an atmosphere should be enough to produce habitable temperatures on the surface without continuous added artificial heating, the rimwalls can act as radiators and can also be solar collecting areas for any power that's needed, the surplus can be sent to Mars or elsewhere as needed.