NASA Funds Space Tether Research as Part of SBIR, STTR Programs

NASA recently announced that it would be conducting contract negotiations for 350 projects under its SBIR and STTR programs, which are aimed at promoting space technology development and transfer by small businesses. Parabolic Arc will be looking at a number of the proposals involving NewSpace companies that it regularly covers or which encompass interesting technologies.

This post looks at proposals put forth by Tech-X Corporation of Colorado and Tethers Unlimited of Washington for the purposes of de-orbiting and maneuvering spacecraft and reducing orbital debris. Two of the projects involve tethers, while a two others focus on developing magnetoplasmadynamic (MPD) thrusters and predicting hall thruster operational lifetimes. Tethers Unlimited has an additional project involving integrated power, propulsion, and pointing for CubeSats for which there is no public information.

STTR AWARD

SMALL BUSINESS CONCERN (SBC):RESEARCH INSTITUTION (RI):
NAME:Tech-X CorporationNAME:Colorado State University
CITY:Boulder, COCITY:Fort Collins, CO
PROPOSAL TITLE:Advanced Particle-in-Cell (PIC) Tools for Simulation of Electrodynamic Tether Plasma Interactions
RESEARCH SUBTOPIC TITLE:Technologies for Space Power and Propulsion

TECHNICAL ABSTRACT

Electrodynamic tethers are optimally suited for use in Low-Earth-Orbit (LEO) to generate thrust or drag maneuver satellites. LEO region is polluted with space debris from the left over of rockets and abandoned satellites. It becomes important to clean them, i.e., de-orbit and ED tethers are promising for such applications. ED tethers are operating without propellants, so less polluting in our space and also cost-efficient. Tether powered satellites can operate in dual mode (thrust or power generation). Advanced PIC tools can perform self-consistent 2-D and 3-D tether simulations to study the plasma interactions and will improve the understanding of the self-induced magnetic field effects on the current collection ability of these ED tethers. These tools once validated using tether ribbon tape experiments can help NASA researchers to analyze various tether geometries in efforts to optimize tether design for space missions on a wide range of operating conditions.

POTENTIAL NASA COMMERCIAL APPLICATIONS

ED tether plasma simulation tools will allow NASA researchers to determine the optimum tether design for space operations. The easy-to-use and user-friendly graphical user interface (GUI) plasma software from Tech-X is a viable high performance modeling tool for NASA to analyze the ED tether operation in LEO. Our validated numerical tool can significantly cut-down the expenses involved in running ground-based tether experiments. Similar tools are being already used for electric propulsion systems like NEXT ion thruster and Hall thrusters at NASA GRC. The fully electromagnetic capabilities in these codes make them ideal for modeling other advanced electric propulsion concepts like cathode less radio frequency (RF) ionization, micro size, nano size field emission and laser ablative propulsion.

POTENTIAL NON-NASA COMMERCIAL APPLICATIONS

Tether satellite is important to other government agencies including the DoD/Air Force. Air Force considers tether powered satellite system for space operations. Our tools will support this effort while it can also be considered for Hall thruster and other advanced electric thruster concept programs at Air Force. Multi-billion dollar military and commercial satellite and aerospace industries such as Boeing, Lockheed Martin, L-3 Communications, Northrop-Grumman, space research companies around the world have shown interest in using computational models to study the plasma characteristics around the tether structure. Also our tools are applicable to ion sources and plasma processing industries where increased performances are desired in terms of ion beam extraction and improved discharge efficiency via the effective predictions of plasma sheath structures.

TECHNOLOGY TAXONOMY MAPPING

Tethers

Estimated Technology Readiness Level (TRL) at beginning and end of contract:
Begin: 4
End: 5

SBIR AWARDS

COMPANY:Tethers Unlimited
LOCATION:Bothell, Wash.
PROPOSAL TITLE:Scalable, Lightweight, Low-Cost Aero/Electrodynamic Drag Deorbit Module
SUBTOPIC TITLE:De-orbit Devices/Technologies for Small Spacecraft

TECHNICAL ABSTRACT

The proposed effort will develop the “Terminator Tape Deorbit Module”, a lightweight, low-cost, scalable de-orbit module that will utilize both aerodynamic drag enhancement and electrodynamic drag to rapidly remove small satellites from LEO altitudes, enabling compliance with orbital lifetime restrictions such as NSS 1740.14 and DoD Instruction 3100.12, Sec. 6.4. Unlike de-orbit devices that rely solely upon aerodynamic drag, which provide no significant reduction in the probability of collision with another space object during orbital lifetime, the Terminator Tape’s generation of electrodynamic drag can dramatically reduce the Area-Time-Product of the system, minimizing chances of debris-generating collisions. The proposed Terminator Tape design utilizes space-qualified materials, requires only standard pyro signals from the host spacecraft for activation, requires no internal avionics, and its deployment method has already been demonstrated successfully in microgravity. It can also accommodate installation of solar cells or other devices on its surface to minimize footprint impacts on small spacecraft. It can also be configured to serve as a multifunctional element, acting as multi-layer insulation (MLI). Positive control of de-orbit timing is provided through a simple actuation requiring only a pyro signal. The device is readily scalable from picosats up to large spacecraft, and in the proposed effort, we will develop a flight ready prototype sized for testing on a CubeSat as well as detailed designs of modules sized for 15 kg nanosats and 100 kg microsats. We will also investigate and test innovative methods for maximizing electrodynamic current, including photoemissive and low-work-function thermoelectric materials. These Phase I efforts will prepare us to perform a flight test on a CubeSat or other low cost platform in the Phase II effort.

POTENTIAL NASA COMMERCIAL APPLICATIONS

The Terminator Tape will enable NASA small satellite programs to comply with end-of-mission orbital lifetime requirements such as NASA Safety Standard 1740.14, and do so with minimal cost, mass, and technical risks.

POTENTIAL NON-NASA COMMERCIAL APPLICATIONS

The Terminator Tape will enable all commercial spacecraft launched into LEO to comply with FCC requirements for end-of-mission orbital lifetime limits in a cost-effective manner. We have received an offer to fly a flight demonstration of a Terminator Tape module on an upcoming mission, and one satellite prime has baselined the Terminator Tape as the de-orbit method for a high-profile government-funded mission.

TECHNOLOGY TAXONOMY MAPPING

Deployment
Tethers

Estimated Technology Readiness Level (TRL) at beginning and end of contract:
Begin: 3
End: 6

COMPANY:Tethers Unlimited
LOCATION:Bothell, Wash.
PROPOSAL TITLE:High Thrust Efficiency MPD Thruster
SUBTOPIC TITLE:Electric Propulsion Systems

TECHNICAL ABSTRACT

Magnetoplasmadynamic (MPD) thrusters can provide the high-specific impulse, high-power propulsion required to support human and robotic exploration missions to the asteroids, Moon, Mars, and the outer planets. MPD thrusters, however, have traditionally been plagued by poor thrust efficiencies due primarily to power lost into the anode caused by the Hall effect. We propose to combine three innovative techniques to create a high thrust efficiency MPD thruster. The first is an unconventional applied magnetic field geometry that counter the Hall effect near the anode surface, the second is shaping of the electrodes to optimize current uniformity, and the third is “through-anode” propellant injection to prevent depletion of the anode plasma. In prior experiments we demonstrated elimination of the anode fall using these novel magnetic fields, and in recent simulation efforts we developed novel magnetic nozzle designs that succeed in counteracting the current concentrations and plasma starvation effects that cause the anode fall. These magnetic nozzles also showed the ability to increase the amount of axial thrust extracted from the accelerated plasma by over 50%. In the Phase I, we will test the effect of a prototype ‘optimized’ magnetic nozzle on the thrust efficiency of a MPD thruster; both the magnetic nozzle prototype and thruster test article are already constructed. Additionally, we will develop technology for through-anode propellant injection, and evaluate its performance through tests and simulations.

POTENTIAL NASA COMMERCIAL APPLICATIONS

Manned exploration of the asteroids, Mars, and the outer planets will require fast transport of personnel and supplies to these destinations. Due to their high specific impulses and ability to process hundreds or thousands of kilowatts of power in a small device, MPD thrusters can provide shorter trip times and higher payload fractions than currently available propulsion technologies. However, significant improvements in MPD thruster efficiency and lifetime are required to achieve this potential. The anode propellant injection and electrode geometry optimization innovations to be developed in the proposed effort have strong potential to achieve the necessary efficiency and lifetime improvements, and thus may enable MPD thruster technologies to dramatically reduce trip times and costs for manned and robotic Exploration missions.

POTENTIAL NON-NASA COMMERCIAL APPLICATIONS

Magnetically nozzled MPD thrusters will also provide cost-effective in-space propulsion for orbit raising of commercial spacecraft such as GEO communications satellites and orbit transfer of large DoD payloads. In terrestrial applications, MPD thruster derived technology has applications in environmentally-friendly materials processing, for uses such as selective material ablation, ion implantation, and surface tempering. Our PI has previously collaborated in the successful development of a magnetically nozzled plasma accelerator for materials processing that is now in commercial use by the 3M company. Additionally, magnetically-nozzled MPD technology has applications in pulsed-power systems as well as fusion power research.

TECHNOLOGY TAXONOMY MAPPING
Maneuvering/Stationkeeping/Attitude Control Devices
Spacecraft Main Engine

Estimated Technology Readiness Level (TRL) at beginning and end of contract:
Begin: 2
End: 4

COMPANY:Tethers Unlimited
LOCATION:Bothell, Wash.
PROPOSAL TITLE:PowerCube: Integrated Power, Propulsion, and Pointing for CubeSats
SUBTOPIC TITLE:Power Generation and Conversion

TECHNOLOGY TAXONOMY MAPPING

Distribution/Management
Fuels/Propellants
Generation
Maneuvering/Stationkeeping/Attitude Control Devices
Spacecraft Main Engine
Storage

Estimated Technology Readiness Level (TRL) at beginning and end of contract:

Begin: 2
End: 4

Editor’s Note: The proposal form for the CubSat project is online, although it does not provide any specific program details.

COMPANY:Tech-X Corporation
LOCATION:Boulder, CO
PROPOSAL TITLE:Predicting Hall Thruster Operational Lifetime Using a Kinetic Plasma Model and a Molecular Dynamics Simulation Method
SUBTOPIC TITLE:Propulsion Systems

TECHNICAL ABSTRACT

Hall thrusters are being considered for many space missions because their high specific impulse delivers a larger payload mass fraction than chemical rockets. With a low thrust, however, Hall thrusters need to operate for a long period of time to achieve the necessary velocity of the mission. For these missions, the lifetime requirements can reach into tens of thousands of hours. For Hall thrusters, the most important life-limiting process is the erosion of the channel walls. However, experimental verification of lifetime is time-consuming and expensive. Therefore, computational method is a useful tool to predict thruster lifetime. Many of the Hall thruster lifetime models were developed, and some of theses models gave quite promising results. However, while qualitatively interesting, the results did not match well with experiment. The reason of this discrepancy is that these numerical models assume electrons as a fluid. The proposed innovation will provide a better understanding of the erosion physics and will be useful for future Hall thruster development, such as HiVHAc, with low cost and time. This tool also will allow to aid in the acceptance and implementation of Hall thrusters as a primary propulsion device through improving confidence of their long term reliability.

POTENTIAL NASA COMMERCIAL APPLICATIONS

NASA’s Science Mission Directorate In-Space Propulsion Technology Project is funding the development of a high specific impulse long life Hall thruster, HiVHAc, a type of Hall thruster systems, as a lower cost electric propulsion alternative for future cost constrained missions. The kinetic molecular dynamics erosion model proposed here can reduce the time and money spent by NASA employees for the Hall thruster development. It also helps the researchers to design that the hBN discharge channel erosion always shields the Hall thruster magnetic circuit elements from ion impingement. The model also would allow for researchers to understand the effect of the operation conditions and the thruster geometry to the channel wall erosion process.

POTENTIAL NON-NASA COMMERCIAL APPLICATIONS

A kinetic molecular dynamic erosion model has numerous applications outside of the scope of NASA. There are a number of companies that develop electric propulsion system in US and other countries. All of these companies spent more than a thousand hours to test their thruster lifetime. They all need an accurate tool which can predict the lifetime for developing Hall thrusters. Recently, Space Systems/Loral has developed the BEPPA code for modeling plume interactions with spacecraft. They chose the detailed electron fluid model developed by Boyd at University of Michigan. It is known that the detailed model results are very sensitive to the channel exit conditions. The model proposed here can provide accurate initial conditions for plasma plume simulations for the hybrid model. The work proposed here is also directly applicable to relevant Hall thruster lifetime issues presently being studied at AFRL/RZSS.

The kinetic molecular dynamic erosion tool can be used to model low energy xenon ion impact for fabrication of hard coatings such as cubic boron nitride or titanium nitride films. The tool would also offer a way to understand and help to optimize the deposition process with low cost. It would offer a way to optimize the deposition process and to investigate the plasma surface interaction for future fusion device development such as ITER with low cost

TECHNOLOGY TAXONOMY MAPPING

Spacecraft Main Engine

Estimated Technology Readiness Level (TRL) at beginning and end of contract:
Begin: 3
End: 4