Jeffrey Slostad

The Terminator Tape ™ : A Cost-Effective De-Orbit Module for End-of-Life Disposal of LEO Satellites

The rapid growth of the orbital debris population poses an increasing threat to military, commercial, and civilian science spacecraft in Earth orbit. NASA, the DoD, ESA, and other organizations have begun to respond to this problem by imposing requirements for debris mitigation upon new space systems. These requirements specify that spacecraft at end-oflife be disposed of by either atmospheric re-entry within 25 years, maneuver to a higher storage orbit, or direct retrieval. For most satellites operating in low Earth orbit (LEO), atmospheric re-entry is the most viable option. To provide a cost-effective means for satellite operators to comply with the 25-year post-mission orbital lifetime restriction, Tethers Unlimited is developing a lightweight de-orbit module called the “Terminator Tape ™ ”. The Terminator Tape is a small module that bolts onto any side of a spacecraft during satellite integration. At the completion of the satellite’s mission, the satellite will activate the Terminator Tape module. The module will then deploy a several-hundred-meter length of thin conducting tape. This tape will not only significantly enhance the aerodynamic drag experienced by the system, but will also generate electrodynamic drag forces through passive interactions with the Earth’s magnetic field and conducting ionospheric plasma, de-orbiting the satellite within 25 years. Two modules are currently in development, one sized for microsatellites operating at altitudes of less than 900 km, and the other sized for CubeSats. In this paper, we will present design overviews and concept of operations for both modules, as well as analyses of deorbit of satellites using these modules.

TRUSSELATOR: On-Orbit Fabrication of High-Performance Composite Truss Structures

The Trusselator program is investigating the value proposition and technical feasibility of fabricating composite truss structures on-orbit to enable construction of high-power solar arrays, high-gain antennas, and other large spacecraft components. In the Phase I effort, we developed a number of conceptual approaches to constructing large solar arrays, identified approaches that could minimize the complexity of the system required to implement them, and performed structural analyses of the top candidates. These analyses indicate that onorbit fabrication could enable structural mass fraction reductions of 2-5X for many-meter trusses with respect to state-of-the-art deployable mast technologies. To validate technical feasibility, we developed a detailed design for a prototype Trusselator device capable of processing Carbon Fiber/thermoplastic tape feedstock to form long continuous lengths of composite truss. We constructed a prototype, and successfully demonstrated fabrication of multi-meter lengths of truss. We then performed mechanical testing of the truss samples that demonstrated that the truss samples achieve a higher ‘bending stiffness efficiency’ than flight-heritage deployable truss technologies. Moreover, this superior result was accomplished using ‘standard modulus’ carbon fiber materials, and integration of highmodulus carbon fiber and optimization of the process is projected to enable further ordersof-magnitude improvement in structural efficiency. This structural efficiency reduces the launch mass, launch cost, and stowed volume of support structures for solar arrays, antennas, and other spacecraft components. Future work on the Trusselator will focus on minimizing its size, weight, and power as well as demonstrating reliable operation in the thermal-vac environment.

THE RETRIEVE MICROSATELLITE TETHER DEORBIT EXPERIMENT

We have designed and built prototype hardware for a very small electrodynamic tether device for deorbiting a microsatellite at the end of its mission. This experiment is intended to fly as a secondary payload on a microsatellite mission. It is designed to present no risk to the spacecraftOs primary payloads, remaining completely dormant until the spacecraft has completed its mission. At the end of the spacecraftOs mission, the tether device will deploy a 2 km long interconnected-multiline conducting tether upwards from the microsatellite, and will use passive electrodynamic drag to lower the orbit of the microsatellite. To minimize the mass of the device, we developed a new tether deployment mechanism in which the tether deployer ejects itself away from the spacecraft and becomes the tether endmass ballast. Laboratory testing of this deployment mechanism indicates that it can successfully deploy a multiline tether at tensions low enough for successful deployment. We evaluated several plasma contactor technologies for this experiment, and selected a thermionic device based upon a COTS dispenser cathode for its minimal mass and technology maturity. With this tether hardware, a ObarebonesO experiment to deorbit a 100 kg microsatellite can be implemented with a total mass of less than 2.5 kg., which is less than the propellant required to fully deorbit such a microspacecraft using thrusters. A more capable experiment, with active control of tether dynamics and diagnostics on tether performance and dynamics, can be implemented with a total mass of 3.5 kg.

Sensorpod sensor deployment technologies

This paper explores the technologies and capabilities of the SensorPod ™ System, a suite of technologies that has been developed to allow ballistic placement of tethered and wireless sensors into remote locations inaccessible by traditional hand- placed sensors or robotic explorers. These locations include potentially hazardous areas, or areas that would become contaminated or disturbed due to the placement of traditional sensor packages. The SensorPod ™ product line includes modular components to deploy individual or arrays of sensor, as well as support technologies such as compact mechanisms to enable the sensor packages to orient themselves relative to the surface and deploy short booms to achieve limited elevation after deployment.