• MASS EFFICIENCY of TENSEGRITY STRUCTURES using UHMWPE
Tensegrity mathematics includes theorems proving that tensegrity solutions are the most mass efficient solutions for the five classical problems of mechanics. The mass efficiency of tensegrity solutions will exceed that of rigid body solutions in every case, and in some cases by as much as 100 times. Given the high cost of launch, mass efficiency is critical in structures designed for deployment in space. This is doubly true for large rotating space habitat structures, which must spin to provide a simulated gravity effect of 1-g, turning the structure's self-mass into additional dead load. Use of materials having the highest strength to weight ratios is therefore a prerequisite for progress in such endeavors.
One candidate is Ultra High Molecular Weight Polyethylene, or UHMWPE, a widely used and inexpensive material, with a strength to weight ratio 15 times that of steel. (Another high efficiency candidate material is graphene, if and when suitable processes for manufacture of this material on a commercial scale can be devised.)
Unprotected UHMWPE is degraded in space by ionizing radiation, but in our application it will be protected from one to four meters of water acquired through asteroid mining, serving the dual function of keeping both the UHMWPE pressure hull and the people inside it shielded from this radiation. If the hull material over time does nevertheless become weakened, our NASA NIAC Phase 1 Final Report has demonstrated feasible procedures for completely rebuilding an inhabited pressure hull.
• GROWTH CAPABILITY of TENSEGRITY STRUCTURES
Combine this with the savings that accrue from starting at small scale and growing to large size, as required, without penalty, and the scale of advantage offered by Skyframe's growth-capable tensegrity approach should start to become clear. Ultra-lightweight tensegrity structures, because of their ability to change shape without loss of stiffness, and readily incorporate new elements, are the ideal choice of structural system for a rotating torus pressure hull capable of expansion while occupied.
When placed in the context of the emergence of commercial competition for asteroid mining, and the coming reductions in launch costs from reusability, the significance of this combination of mass efficiency and growth capability cannot be over-emphasized. This technology will remove the limitations that presently confine the human presence in space to Low Earth Orbit, and enable humans to conduct extended missions across the inner solar system.