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> Starship should bring those costs below $1000. It might even bring the costs below $100/kg.
by vardump 2y ago
> Starship should bring those costs below $1000.
It might even bring the costs below $100/kg.
- ben_w 2y agoIt might, but it's also at a scale where people can dust off the old plans for orbital rings and ask if this time the economics work out. (My guess is the economics are fine, but the politics would kill it on earth, so the moon or mars will get one, but that's just an interested amateur opinion).
- vardump 2y agoOnce you put something big in the LEO, you'll have to be able to boost its orbit indefinitely, because the orbit will otherwise slowly decay.
- DarmokJalad1701 2y agoThat depends on how high the orbit is. If it is high enough, the decay will take centuries.
- ben_w 2y agoIIRC, above something like geostationary they tend to decay upwards? Though the old orbital ring white paper wasn't suggesting anything like that, this was an alternative to needing to go so high in the first place. (I may be misremembering or getting confused with a thing specific to tidal locking?)
- AdammadA 2y agoI wonder if they could have an orbit high enough to move away from earth with some kind of drag cables dangling from them into low orbit to counter the outward movement. Would that work?
- dotnet00 2y agoYou mean something like a skyhook?
- AdammadA 2y agoYes but no hook or anchor needed I'd assume. The cable alone in lower orbit would weigh enough to be pulled by gravity.
- lovecg 2y agoThese orbits have vastly different speeds though. Consider a high geosynchronous orbit vs. something like ISS which goes around the Earth in an hour or two.
- AdammadA 2y agobut you are towing the cable and you'd only get so far down for the counteraction of force from gravity to pull on the cable. Would speed or friction on a cable be a problem.
- cjbillington 2y agoThat is indeed what you get with tidal forces - bodies closer than geostationary orbit lose angular momentum and decay inward, bodies further out steal angular momentum from Earth and move outward. I suppose the same effect is there with satellites much smaller than the moon, but it would be tiny.
- lucianbr 2y agoThe L in LEO means we're talking about orbits that are not very big.
- schiffern 2y agoBy definition, LEO extends up to 2,000 km. At that altitude orbital lifetimes can exceed 10,000 years. https://commons.wikimedia.org/wiki/File:Orbital_Debris_Lifetime_Diagram_Low_Eccentricity.png https://commons.wikimedia.org/wiki/File:Orbital_Debris_Lifet...
- ben_w 2y agoContiguous rings filling an entire orbit don't have much air resistance, and what little they do have is small in comparison to their momentum. But yes, eventually things decay.
- piombisallow 2y agoIf you have the infrastructure to build an orbital ring, you have the infrastructure to keep it supplied too
- pantalaimon 2y agoThere is some SciFi story about civilization collapsing and the survivors worrying that the sky will fall on them hidden in there.
- dyauspitr 2y agoGotta make the individual pieces small enough to mostly burn up completely on rentry.
- jaggederest 2y agoTerm of art for this is "design for demise", i.e. make everything of pieces small enough and materials ablative enough that there's less than 1 in 10k chance that any debris will survive to the surface. https://www.esa.int/Enabling_Support/Space_Engineering_Technology/CDF/Design_For_Demise_A_First_Look https://www.esa.int/Enabling_Support/Space_Engineering_Techn...
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- jvm___ 2y agoPlanned obsolescence but in a good way.
- Vecr 2y agoAlready exists, Chasm City by Alastair Reynolds. They absolutely trash orbit by planning very badly and over-packing habitats.
- mr_toad 2y agoPresuming it’s in LEO. When and if we ever get around to building these things they probably won’t be in LEO at least not for long. Some of them might not even be constructed from materials launched from Earth.
- Tepix 2y agoHow does the orbit or an orbital ring decay?
- adastra22 2y agoThere are relatively stable orbits over the equator.
- helpfulContrib 2y ago[dead]