(Georgia Institute of Technology, 2015-05-02)
Long, Alexandra C.
Orbital debris is a growing problem in low Earth orbit; it has crossed a threshold of critical
density where the number of debris objects will grow exponentially unless mitigated. Spent
launch vehicle upper stages represent a problematic category of orbital debris in highly
utilized orbits. They can stay in orbit for well over 100 years if left to deorbit naturally,
and they represent a significant fraction of large space debris in low-Earth orbit. It is
estimated that removing a few large objects per year will mitigate the exponential growth
of debris. To address the debris problem, a trade study was conducted to determine
a deployable drag device to accelerate the orbit degradation of upper stages. Following
the operation of the upper stage, the drag device will be deployed to decrease the orbit
lifetime of the system. The design is targeted toward upper stages launched into orbital
altitudes ranging from 650-850 km. Three categories of deployable drag devices are being
investigated: drag sails, inflatable aerodynamic decelerators, and electrodynamic tethers.
These are compared to the option of using residual propellant in the upper stage to perform
a burn to initiate a deorbit trajectory. The device will be mounted to the upper stage using
a standardized secondary payload launch interface, such as a CubeSat deployer device or
the EELV Secondary Payload Adapter (ESPA). The trade study compared the drag device
configurations based on cost, risk, and deorbit time. A maximum deorbit period of 25
years is a performance design requirement. The propulsive option was shown to be the
lowest cost option, however the drag device is more mass efficient and has less of an impact
to the payload capability of the launch vehicle. A drag sail design is proposed as a baseline
design for the device. A stability analysis was conducted to determine the configuration of
the device, then the initial baseline design with preliminary component selection and an
initial structural analysis were investigated