Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Better Electric Propulsion May Boost Satellite Lifetimes

23.10.2009
Researchers at the Georgia Institute of Technology have won a $6.5 million grant to develop improved components that will boost the efficiency of electric propulsion systems that are used to control the positions of satellites and planetary probes.

Focusing on improved cathodes for devices known as Hall effect thrusters, the research would reduce propellant consumption in commercial, government and military satellites, allowing them to remain in orbit longer, be launched on smaller or cheaper rockets, or carry larger payloads. Sponsored by the U.S. Defense Advanced Research Projects Agency Defense Sciences Office (DARPA-DSO), the 18-month project seeks to demonstrate the use of propellant-less cathodes with Hall effect thrusters.

“About 10 percent of the propellant carried into space on satellites that use an electric propulsion system is essentially wasted in the hollow cathode that is part of the system,” said Mitchell Walker, an assistant professor in Georgia Tech’s School of Aerospace Engineering and the project’s principal investigator. “Using field emission rather than a hollow cathode, we are able to pull electrons from cathode arrays made from carbon nanotubes without wasting propellant. That will extend the life of the vehicle by more efficiently using the limited on-board propellant for its intended purpose of propulsion.”

To maintain their positions in space or to reorient themselves, satellites must use small thrusters that are either chemically or electrically powered. Electrically-powered thrusters use electrons to ionize an inert gas such as xenon. The resulting ions are then ejected from the device to generate thrust.

In existing Hall effect thrusters, a single high-temperature cathode generates the electrons. A portion of the propellant – typically about 10 percent of the limited supply carried by the satellite – is used as a working fluid in the traditional hollow cathode. The DARPA-funded research would replace the hollow cathode with an array of field-effect cathodes fabricated from bundles of multi-walled carbon nanotubes. Powered by on-board batteries and photovoltaic systems on the satellite, the arrays would operate at low power to produce electrons without consuming propellant.

Walker and collaborators at the Georgia Tech Research Institute (GTRI) have already demonstrated field-effect cathodes based on carbon nanotubes. This work was presented at the 2009 AIAA Joint Propulsion Conference held in Denver, Colo. The additional funding will support improvements in the devices, known as carbon nanotube cold cathodes, and lead to space testing as early as 2015.

“This work depends on our ability to grow aligned carbon nanotubes precisely where we want them to be and to exacting dimensions,” said Jud Ready, a GTRI senior research engineer and Walker’s collaborator on the project. “This project leverages our ability to grow well-aligned arrays of nanotubes and to coat them to enhance their field emission performance.”

In addition to reducing propellant consumption, use of carbon nanotube cathode arrays could improve reliability by replacing the single cathode now used in the thrusters.

“Existing cathodes are sensitive to contamination, damaged by the ionized exhaust of the thruster, and have limited life due to their high-temperature operation,” Ready noted. “The carbon nanotube cathode arrays would provide a distributed cathode around the Hall effect thruster so that if one of them is damaged, we will have redundancy.”

Before the carbon nanotube cathodes developed by Georgia Tech can be used on satellites, however, their lifetime will have to be increased to match that of a satellite thruster, which is typically 2,000 hours or more.

The devices will also have to withstand the mechanical stresses of space launches, turn on and off rapidly, operate consistently and survive the aggressive space environment.

Part of the effort will focus on special coating materials used to protect the carbon nanotubes from the space environment. For that part of the project, Walker and Ready are collaborating with Lisa Pfefferle in the Department of Chemical Engineering at Yale University.

The researchers are testing their cathodes with the same Busek Hall effect thruster that flew on the U.S. Air Force’s TacSat-2 satellite. In addition, the cathodes will be operated with Hall effect thrusters developed by Pratt & Whitney and donated to Georgia Tech. The researchers are also collaborating with L-3 ETI on the electrical power system and with American Pacific In-Space Propulsion on flight qualification of the hardware.

The ability to control individual cathodes on the array could provide a new capability to vector the thrust, potentially replacing the mechanical gimbals now used.

The use of carbon nanotubes to generate electrons through the field-effect process was reported in 1995 by a research team headed by Walt de Heer, a professor in Georgia Tech’s School of Physics. Field emission is the extraction of electrons from a conductive material through quantum tunneling that occurs when an external electric field is applied.

The improved carbon nanotube cathodes should advance the goals of reducing the cost of launching and maintaining satellites.

“Thrust with less propellant has been one of the major goals driving research into satellite propulsion,” said Walker, who is director of Georgia Tech’s High-Power Electric Propulsion Laboratory. “Electric propulsion is becoming more popular and will benefit from our innovation. Ultimately, we will help improve the performance of in-space propulsion devices.”

John Toon | Newswise Science News
Further information:
http://www.gatech.edu

More articles from Power and Electrical Engineering:

nachricht Perovskite-silicon solar cell research collaboration hits 25.2% efficiency
15.06.2018 | Helmholtz-Zentrum Berlin für Materialien und Energie GmbH

nachricht Second heat source optimises heat pump system
12.06.2018 | FIZ Karlsruhe – Leibniz-Institut für Informationsinfrastruktur GmbH

All articles from Power and Electrical Engineering >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: AchemAsia 2019 will take place in Shanghai

Moving into its fourth decade, AchemAsia is setting out for new horizons: The International Expo and Innovation Forum for Sustainable Chemical Production will take place from 21-23 May 2019 in Shanghai, China. With an updated event profile, the eleventh edition focusses on topics that are especially relevant for the Chinese process industry, putting a strong emphasis on sustainability and innovation.

Founded in 1989 as a spin-off of ACHEMA to cater to the needs of China’s then developing industry, AchemAsia has since grown into a platform where the latest...

Im Focus: First real-time test of Li-Fi utilization for the industrial Internet of Things

The BMBF-funded OWICELLS project was successfully completed with a final presentation at the BMW plant in Munich. The presentation demonstrated a Li-Fi communication with a mobile robot, while the robot carried out usual production processes (welding, moving and testing parts) in a 5x5m² production cell. The robust, optical wireless transmission is based on spatial diversity; in other words, data is sent and received simultaneously by several LEDs and several photodiodes. The system can transmit data at more than 100 Mbit/s and five milliseconds latency.

Modern production technologies in the automobile industry must become more flexible in order to fulfil individual customer requirements.

Im Focus: Sharp images with flexible fibers

An international team of scientists has discovered a new way to transfer image information through multimodal fibers with almost no distortion - even if the fiber is bent. The results of the study, to which scientist from the Leibniz-Institute of Photonic Technology Jena (Leibniz IPHT) contributed, were published on 6thJune in the highly-cited journal Physical Review Letters.

Endoscopes allow doctors to see into a patient’s body like through a keyhole. Typically, the images are transmitted via a bundle of several hundreds of optical...

Im Focus: Photoexcited graphene puzzle solved

A boost for graphene-based light detectors

Light detection and control lies at the heart of many modern device applications, such as smartphone cameras. Using graphene as a light-sensitive material for...

Im Focus: Water is not the same as water

Water molecules exist in two different forms with almost identical physical properties. For the first time, researchers have succeeded in separating the two forms to show that they can exhibit different chemical reactivities. These results were reported by researchers from the University of Basel and their colleagues in Hamburg in the scientific journal Nature Communications.

From a chemical perspective, water is a molecule in which a single oxygen atom is linked to two hydrogen atoms. It is less well known that water exists in two...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Munich conference on asteroid detection, tracking and defense

13.06.2018 | Event News

2nd International Baltic Earth Conference in Denmark: “The Baltic Sea region in Transition”

08.06.2018 | Event News

ISEKI_Food 2018: Conference with Holistic View of Food Production

05.06.2018 | Event News

 
Latest News

Novel method for investigating pore geometry in rocks

18.06.2018 | Earth Sciences

Diamond watch components

18.06.2018 | Process Engineering

New type of photosynthesis discovered

18.06.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>