Space polymer ropes

This project came to me and my lab partner Zbyszek after our idea for Moon Regolith Conveyor, where we noticed the importance of ropes in potential space applicaions. Tendons are widely recognized today as extremely useful elements in many mechanical designs and can be used as means of stiffening and supporting tall constructions (ex. lifts, cranes, tents, bridges, transmission belts and ropes, small satellites etc.). Tendons can also be used in robotic mechanisms and force transmission components. An important application for cords is also in stratospheric balloons used for wide array of research, parachutes (that can be used for landers or probes) and in the future possibly regolith conveyors on moon stations. As polymer materials continue being developed their potential in space applications needs to be researched.

Both of us had previous ideas about including ropes in robotics and for construction stiffening. We see the polymers UHMWPE (Ultra High Molecular Weight Polyethylene) and Kevlar (Aramid fiber) as potentially useful materials for ropes in space applications.

"26th ESA Symposium on European Rocket and Balloon Programmes and Related Research" in Luzern Swizerland

The Results :

For this study two types of polymer materials were selected: Kevlar (aramid fiber) and UHMWPE (Ultra High Molecular Weight Polyethylene). Both were tested in the form of thin ropes/cords that had the same diameter (0.7 mm) and weave and were produced by the same company (Atwood Rope MFG). Those materials have properties that could allow them to work with a good mechanical properties in outer space environment. Additionally to adapt UHMWPE for withstanding high temperatures (above 150 ˚C) it was subjected to β radiation in order to cross-link the polymeric chains to make it stiffer and more resistant to temperature change. 

The materials were tested for tensile strength first in room temperature and then low, cryogenic temperatures using liquid nitrogen cooling (down to −196 °C). Two types of tensile test were performed. One was done using a device made by authors and the other using Zwick Roell (ZWICK 1435) universal testing machine. Differential Scanning Calorimetry was performed to verify the working temperature range for both materials and the effects of cross-linking UHMWPE with β radiation. Additionally different methods of fixing the rope ends were tested for tensile properties and their durability. The results point to both materials being able of carrying load and being resistant to britteling in cryogenic applications. Both materials are able to withstand and carry high loads of even 90 kg and over, depending on treatment and material type. While UHMWPE proved to be up to 100% stronger in cryogenic conditions, Kevlar still performs better at high temperatures. Additionally an approximate 40% raise in strength was observed for cryogenic conditions in relation to room temperature in UHMWPE and a slight raise in case of Kevlar.

Poster for KGK Space Resources Conference in Kraków

The poster won 2nd place in the poster competition.

Currently UHMWPE AND Kevlar were both tested in room temperatures and cryogenic temperatures for their durability and tensile strength.