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Space tethers take the old, defunct space elevator concept and shorten it. Rockets can fly up to a dangling hook in the sky and then climb to a higher orbit. If the tether rotates, it can act like a catapult, providing a significant boost in a location where providing thrust is expensive. Kurzgesagt has a nice explainer and ToughSF has a great piece explaining the mechanics and some applications.

Tethers make it cheaper to explore space, but how much cheaper? Let's look at the benefits.

Tether materials and characteristic velocity

The key performance metric for the tether material is the characteristic velocity:

_V_c = sqrt frac{2 T}{rho}_

Where T is the tensile strength and rho is the density.

The stronger and lighter the material is, the faster the tether [...]

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Outline:

(00:40) Tether materials and characteristic velocity

(01:58) Delta V and fuel savings

(06:06) Tether mass ratio and fuel costs

(07:51) Numerical examples

(12:05) Conclusion

(14:54) Appendix

(14:57) Tether materials

(18:41) Why tether material doesn’t matter too much

(21:09) Single stage to orbit is silly

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