Long-life, damage resistant tether system for extended-duration, high-value,
and crew-rated missions.
Description:
The lifetimes of current single-line tethers are limited by damage due to
meteorite and orbital debris impactors to periods on the order of weeks.
Although single-line tether lifetimes can be improved by increasing the
diameter of the tether, this incurs a prohibitive mass penalty. The Hoytether,
illustrated in Fig. 1, is a tether structure composed of multiple lines
with redundant interlinking that is able to withstand many impacts.
Figure 1. a) Section of a tubular Hoytether ("Hoytube").
b) Schematic of undisturbed Hoytether. c) Secondary lines redistribute load
around a failed primary line without collapsing structure.
Research
Results:
Analytical modeling, numerical simulation, and ground-based experimental testing
of this design indicate that this tether structure can achieve lifetimes of
tens of years without incurring a mass penalty. Moreover, while single-line
tether survival probability drops exponentially with time, redundant linkage
in failsafe multiline tethers keeps the tether survival probability very high
until the tether lifetime is reached. The survival probability of a failsafe
multiline tether is compared to that of an equal-mass single line tether in
Fig. 2.
Figure 2. Lifetime comparison of equal-weight single
line and failsafe multiline tethers for a low-load mission.
Status:
Tethers Unlimited has successfully developed a method of fabricating long
lengths of Hoytethers. Using this process, we have fabricated over fifty
kilometers of Hoytether prototypes suitable for use in electrodynamic and
momentum-exchange tether missions, and tested them succesfully in several
tether deployment systems.
For further
information on a Hoytether™ customized for your space mission,
please contact
TUI at information@tethers.com
