TU SAT1
Tether Design
Purpose
There are two main forms of
satellite stabilization: active and passive. Active stabilization
includes such things as thrusters and dynamic electronic control
whereas passive stabilization involves such things as gravity
gradients and viscous dampers. We chose to use the passive
stabilization of a gravity gradient boom because it is cheaper, less
complex than burning fuels for thrust or writing AI code, and weighs
much less than other methods. The boom utilizes the fundamental law of
gravity to achieve its stabilized state. The tether assembly on TU Sat
1 spools out 100 feet of line with an attached mass on the end. When
deployed correctly, the mass will be 100 feet closer to the earth than
the satellite and thus be feeling a stronger gravitational force and
shorter orbital period. The result is that the tip mass, in essence,
orients the bottom of the satellite down towards the earth causing the
satellite to remain upright and in a stable attitude. Also, the tip
mass will be at a lower altitude than the satellite and will therefore
have a faster orbit. This will pull the satellite along and force it
to always point towards the earth.
 How
it Works
The deployment of the tether is
similar to the antique clothes dryers that wrung out water by
compressing the clothes between two rollers. Instead of clothes, we
are pulling a thin titanium wire (about seven thousandths of an inch
in diameter) off a spool and through two wheels which act as rollers.
One of the wheels is attached to a stepping motor. The potential
problem with this design is that the boom may be deployed the
satellite in the wrong orientation. If this happens, instead of being
stable with the bottom facing the earth, TU Sat 1 will be oriented
upside-down. Therefore, the tether must be retractable. To do this, a
small DC motor is attached to the spool. If deployed incorrectly, the
motor winds up the tether and then deploys it again properly. The
stepping motor attached to the roller creates enough tension to allow
the spool to be wound compactly and properly.
Design |
Overall Height:
2.125”