NASA Scientific and Technical Aerospace Reports

20040111038 NASA Marshall Space Flight Center, Huntsville, AL, USA
Plasma Interactions With a Negative Biased Electrodynamic Tether
Vaughn, Jason A.; Curtis, Leslie; Welzyn, Ken J.; 8th Spacecraft Charging Technology Conference; March 2004; 13 pp.; In
English; See also 20040111031; No Copyright; Avail: CASI; A03, Hardcopy
The ProSEDS conductive tether design incorporates two distinct types of tethers from a plasma interaction viewpoint. The
200 m closest to the Delta II spacecraft is insulated from the plasma, and the remaining 4800 m is semi-bare. This latter portion
is considered semi-bare because a conductive coating, which is designed to collect electrons from the plasma, was applied to
the wires to regulate the overall tether temperature. Because the tether has both insulating and conductive tether sections, a
transition point exists between the two that forms a triple point with the space plasma. Also, insulated tethers can arc to the
space plasma if the insulation is weakened or breached by pinholes caused by either improper handling or small meteoroid
and orbital debris strikes. Because electrodynamic tethers are typically long, they have a high probability of these impacts. The
particles, which strike the tether, may not have sufficient size to severe the tether, but they can easily penetrate the tether
insulation producing a plasma discharge to the ambient plasma. Samples of both the ProSEDS tether transition region and the
insulated tether section with various size of pinholes were placed into the MSFC plasma chamber and biased to typical
ProSEDS open circuit tether potentials (-500 V to -1600 V). The results of the testing showed that the transition region of the
tether (i.e. the triple point) arced to the ambient plasma at -900 V, and the tethers damaged by a pinhole or simulated debris
strike arced to the plasma between -700 V and -900 V. Specific design steps were taken to eliminate the triple point issue in
the ProSEDS tether design and make it ready for flight. To reduce the pinhole arcing risk, ProSEDS mission operations were
changed to eliminate the high negative potential on the insulated tether. The results of the testing campaign and the design
changes implemented to ensure a successful flight are described.
Author
Plasma Interactions; Tethering; Insulation; Space Plasmas; Electrons
20040111052 Astrium, Toulouse, France
Secondary Arcs on Solar Generators: EMAGS 2 Test Campaign
Gaillot, L.; Boyer, E.; Pelissou, P.; Levy, L.; Sarrail, D.; Fille, M-L.; Caswell, D.; 8th Spacecraft Charging Technology
Conference; March 2004; 11 pp.; In English; See also 20040111031; No Copyright; Avail: CASI; A03, Hardcopy
For few years, many tests have been performed on solar array samples around secondary arcs in order to validate a
theoretical model, to determinate the arcing conditions and to conceive some mitigating techniques. EMAGS 2 (Solar Array
Triggered Arc Phenomena Study - ESA contract) is the continued effort of ESA to try to better define how tests should be
performed. This study consists in an extensive test campaign on different solar array samples issued from actual EADS
ASTRIUM programs as on dummy SA samples.
Author
Solar Arrays; Mathematical Models; Arcs
20040111063 NASA Marshall Space Flight Center, Huntsville, AL, USA
Assessment of High-Voltage Photovoltaic Technologies for the Design of a Direct Drive Hall Effect Thruster Solar
Array
Mikellides, I. G.; Jongeward, G. A.; Schneider, T.; Carruth, M. R.; Peterson, T.; Kerslake, T. W.; Snyder, D.; Ferguson, D.;
Hoskins, A.; 8th Spacecraft Charging Technology Conference; March 2004; 17 pp.; In English; See also 20040111031
Contract(s)/Grant(s): NAS3-01100; No Copyright; Avail: CASI; A03, Hardcopy
A three-year program to develop a Direct Drive Hall-Effect Thruster system (D2HET) begun in 2001 as part of the NASA
Advanced Cross-Enterprise Technology Development initiative. The system, which is expected to reduce significantly the
power processing, complexity, weight, and cost over conventional low-voltage systems, will employ solar arrays that operate
at voltages higher than (or equal to) 300 V. The lessons learned from the development of the technology also promise to
become a stepping-stone for the production of the next generation of power systems employing high voltage solar arrays. This
paper summarizes the results from experiments conducted mainly at the NASA Marshal Space Flight Center with two main
solar array technologies. The experiments focused on electron collection and arcing studies, when the solar cells operated at
high voltages. The tests utilized small coupons representative of each solar array technology. A hollow cathode was used to
emulate parts of the induced environment on the solar arrays, mostly the low-energy charge-exchange plasma (1012-1013 m-3
and 0.5-1 eV). Results and conclusions from modeling of electron collection are also summarized. The observations from the
total effort are used to propose a preliminary, new solar array design for 2 kW and 30-40 kW class, deep space missions that
may employ a single or a cluster of Hall- Effect thrusters.
Author
Hall Effect; Charge Transfer; High Voltages; Solar Arrays; Electrolytic Cells
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