CubeSat DeOrbit System Status Update 1
CubeSat testing has progressed steadily in spring 2014. The group has changed the membrane
to no longer be pressurized; instead the inflatable will be vacuumed sealed independently and placed
into the baseplate. The cutting wire will be installed in contact with the Mylar membrane, with Kapton
as an insulator above and below to achieve a thermal barrier. The team is currently investigating
methods to ensure the cutting wire does not come in contact with the baseplate and cause the energy
to be diverted away from the Mylar membrane. Testing is scheduled this week to determine if Kapton
can be used as an insulator.
A Matlab code was written to determine the voltage and power requirements needed to heat
the cutting wire above the melting point of Mylar. This will aid the team in selecting a properly sized
battery to supply the energy. From these calculations, the amount of energy required to do so can be
reduced by selecting a smaller gauge cutting wire. Therefore, 30 and 34 gauge wires were selected to
incorporate into the baseplate design and to demonstrate the material's durability.
A circuit design has been breadboard validated for the wireless communication which sends the
command to activate the cutting wire. Trouble shooting for the software on the wireless communication
was successful and testing was done in the lab which emulated the baseplate with a membrane and
cutting wire, which was also successful.
The baseplate currently has concurrent design developments to analyze a variety of alternatives
to the membrane cutting method. These models include various solid door options which utilize Shape
Memory Alloys (SMA) for actuation. As vacuum chamber testing moves forward requirements for the
opening mechanism will be established. The tether system is also being designed which will extend the
inflatable behind the CubeSat for stability during deceleration. A force gauge which is attached to the
tether system is being investigated to provide information on the drag force created by the inflatable
during deployment.
Cube and spherical prototype inflatables have been developed to show proof of production. In
the coming week two different sphere designs and a cube design will be fabricated. The two spherical
designs will resemble a soccer ball and a volley ball pattern. Once the inflatables have been fabricated
the three designs will undergo a pressure test and vacuum folding test. Once results have been obtained
the inflatable designs will be refined and one of the three inflatable designs will be chosen.
In order to ensure the inflatable deploys correctly research has begun on a heating element
which can assist the inflatable in reaching a large enough volume that solar energy can continue and
complete the sublimation of all benzoic acid contained in the inflatable. The plan is to find the most
efficient way to deploy the inflatable and sublimate the benzoic acid if it fails to expand and deploy by
itself due to trapped air in the inflatable. Communication with the past group to attain hardware and
research already conducted will accelerate the process in hopes of adding a heating element system to
the vacuum chamber testing procedures.
A study on how to ensure the solar energy reaches the benzoic acid in a manner conducive to
the sublimation of all benzoic acid contained in the inflatable is also underway. This allows the design
team to control the internal pressure in the inflatable by controlling the amount of benzoic acid placed
inside the inflatable based on altitude stipulations for deployment. Methods for applying the benzoic
acid includes a paste, powder, and aerosol approaches.
The thermal analysis is nearing completion and awaiting review with the faculty advisor. The
thermal analysis is dependent on orbit of the CubeSat and as such an orbit analysis using Systems Tool
Kit (STK) will be conducted by multiple team members in connection with the thermal analysis, as well
as providing information on communications using the ground station based here at ODU.
Vacuum chamber testing is planned at NASA Langley Research Center for the end of February
and early March. The team will be conducting a gravity assisted deployment for an initial analysis of the
system as it operates under vacuum. Future testing will validate design improvements and also
calculations for the thermal and orbital analysis.