Power systems with voltages higher than about 55 volts may charge in Low Earth Orbit (LEO) enough to cause destructive arcing. The NASA STD-4005 LEO Spacecraft Charging Design Standard will help spacecraft designers prevent arcing and other deleterious effects on LEO spacecraft. The Appendices, an Information Handbook based on the popular LEO Spacecraft Charging Design Guidelines by Ferguson and Hillard, serve as a useful explanation and accompaniment to the Standard

Ferguson, Dale C.

NASA Technical Reports Server

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NASA Marshall Space Flight Center 
NASA STD-4005 - The LEO Spacecraft Charging Design Standard 
Dale C .  Ferguson* 
NASA Marshall Space Flight Center, Huntsville, AL 35812 
Power systems with voltages higher than about 55 volts may charge in Low Earth Orbit 
(LEO) enough to cause destructive arcing. The NASA STD-4005 LEO Spacecraft Charging 
Design Standard will help spacecraft designers prevent arcing and other deleterious effects 
on LEO spacecraft. The Appendices, an Information Handbook based on the popular LEO 
Spacecraft Charging Design Guidelines by Ferguson and Hillard, serve as a useful 
explanation and accompaniment to the Standard. 
I. Introduction 
HE space environment in Low Earth Orbit (LEO) is significantly different from that in geosynchronous orbit 
T ( G E O ) ,  and an increasing number of LEO satellites are being flown. Many of the interactions leading to 
spacecraft charging in LEO are completely different from those in GEO environments. However, for lack of a 
NASA standards document on LEO spacecraft charging, many spacecraft manufacturers still use the 1984 
Spacecraft Charging Guidelines of Purvis, Garrett, Whittlesey, and Stevens', intended only for GEO satellites, to 
design LEO spacecraft. This unfortunate state of events is being changed. The new NASA STD-4005 Low Earth 
Orbit Spacecraft Charging Design Standard has undergone its final review process, and is slated for release this year. 
II. Scope, Purpose and Applicability of the NASA STD-4005 Standard 
The NASA STD-4005 standard and information handbook presents an overview of the current understanding of 
the various plasma interactions that can result when a high voltage system is operated in the Earth's ionosphere, 
references common design practices that have exacerbated plasma interactions in the past, and recommends standard 
practices to eliminate or mitigate such reactions. The purpose of the standard is to provide a design standard for 
high-voltage space power systems (>55 volts) that operate in the plasma environment associated with LEO (altitude 
from 200 and 1000 km and latitude between -50 and +50 degrees). Such power systems, particularly solar arrays, are 
the proximate cause of spacecraft charging in LEO and can interact with this environment in a number of ways that 
are potentially destructive to themselves as well as to the platform or vehicle that has deployed them. 
High voltage systems are used in space for two reasons. The first reason is to save launch weight. First of all, for 
the same power level, higher voltages enable use of thinner wires (lighter cabling). This is because P = IV, and V = 
IR, so P = 12R (where P is power, I is current, R is resistance, and V is voltage). If I is decreased by use of higher V, 
then thinner wires can be used with no increase in power loss due to cabling. Of course, if one uses the same cable 
mass, higher voltages will enable higher efficiencies, since less power will be lost to resistance in the cables. For 
very large power systems, the decrease in cable mass can be substantial. 
Secondly, some spacecraft functions require high voltages. For example, electric propulsion uses voltages from 
about 300 V (Hall thrusters) to about 1000 V (ion thrusters). For low voltage power systems, conversion of 
substantial power to high voltages is required for these spacecraft functions to operate. The weight of the power 
conversion systems, Power Management and Distribution (PMAD), can be a substantial kaction of the total power 
system weight in these cases. It is more efficient, and can save weight, if the high voltage functions can be directly 
powered from a high voltage solar array, for instance. If the high voltage function is electric propulsion, we call such 
ive electric propulsion system. Because of these and other reasons for using high voltages in 
sigriers and manufacturers are using high voltages more and more. However, the use of high 
particular, spacecraft charging in LEO, in contrast to that in geosynchronous earth orbit 
, 
* Physicist, Space Environment Effects Branch, Mailstop EM50, AIAA Senior Member. 
1 
American Institute of Aeronautics and Astronautics 
https://ntrs.nasa.gov/search.jsp?R=20060025081 2019-08-29T22:01:37+00:00Z
(GEO), is caused by exposed high voltages, and can lead to arcing, power drains, power disruptions, and loss of 
spacecraft coatings. Thus, system designers need a standard to show them how to mitigate the spacecraft charging 
effects of using high voltages in LEO. In addition to system designers, NASA STD-4005 should be useful to project 
managers, solar m a y  designers, system engineers, etc. 
The NASA STD-4005 standard is applicable to high-voltage space power systems that operate in the plasma 
environment associated with LEO. As was stated before, it is intended for space systems that spend the majority of 
their time at altitudes between 200 and 1000 km (usually known as LEO applications) and at latitudes between about 
+ and - 50 degrees - that is, space systems that do not encounter GEO (geosynchronous orbit) charging 
conditions, that do not (often) encounter the auroral ovals of electron streams, and that do notfly through the Van 
Allen belts. For the extreme radiation protection that is necessary for orbits in the Van Allen belts, exterior 
spacecraft charging will likely be a secondary concern. However, internal charging will be very important. It is not 
in the purview ofNASA STD-400.5 to deal with internal charging. 
Some of the design standarb for LEO are at variance with good design practice for GEO spacecraft. Ifyour 
spacecraft will fly in both LEO and GEO conditions, care must be taken to use design solutions that are applicable 
in both environmental regimes. 
III. The Requirements Section 
There are sections on acronyms and definitions, defining all of the specific terms used in the Standard, that take 
up about 9 pages. Then comes the meat of the standard. Section 4 of the NASA STD-4005 Standard and 
Information Handbook is the Requirements Section. Here, all of the LEO requirements are given and references are 
given to the Appendices, which are the Information Handbook section, based largely on the Ferguson and Hillard 
(2003) LEO Spacecraft Charging Design Guidelines2. The main requirement is to prevent arcing. All of the types 
of arcing due to spacecraft charging are listed. 
Quoting from the standard, 
Arcs on spacecraft in LEO must be prevented because of their potentially 
disastrous consequences (see appendix C, section C.1.2.3). The four types of arcs which 
shall be prevented are as follows: 
a. Solar array or power system trigger arcs (see appendix C, section C. 1.2) 
b. Sustained solar array arcs (see appendix C, section C.1.2.3.1) 
c. Dielectric breakdown of structure surface coatings (can also become 
sustained, see appendix C, section C. 1.2.3.1) 
d. Paschen discharges (see appendix B, section B.2, and appendix 0, section 0.2.3). 
Strategies to prevent arcing are given, and techniques are detailed to implement the strategies. Secondly, 
prevention of large parasitic currents to the power system is emphasized. Strategies and techniques are given. 
Throughout NASA STD-4005, the importance of testing is emphasized. Many of the thresholds for arcing are 
poorly known, and if the strategy to prevent arcing is to keep voltages lower than the appropriate threshold, testing 
must be used to determine those thresholds and to guarantee that flight articles do not arc. Thus, it is listed as a 
requirement. The requirements section of NASA STD-4005 is about 6 pages long. 
IV. Appendices: The Information Handbook 
As stated before, the Requirements Section has many references to the Appendices, the Information Handbook 
Section. Based on the Ferguson and Hillard (2003) Low Earth Orbit Spacecraft Charging Design Guidelines2, the 
Information Handbook has been updated and revised to serve as an explanatory supplement to the NASA STD-4005 
standard. It has 6 main subsections, in addition to the document reference section. The main s 
APPENDIX A OVERVIEW OF PLASMA INTERACTIONS, 
APPENDIX B ENVIRONMENTS, 
2 
American Institute of Aeronautics and Astronautics 
APPENDIX C PLASMA INTERACTIONS, 
APPENDIX D MITIGATION TECHNIQUES, 
APPENDIX E MODELING, and 
APPENDIX F TESTING. 
In each section, a comprehensive descriptiodreview of the topic is given, with many references. The Information 
Handbook is intended as a description of the state-of-the-art in LEO spacecraft charging, and is fblly 52 pages long. 
NASA STD-4005, the Low Earth Orbit Spacecraft Charging Design Standard will be published and distributed 
in hardcopy and as a searchable electronic file. NASA STD-4005 is approximately 83 pages long, including the 
Appendices and References, and may be obtained through the NASA Technical Standards Program, which has the 
website http://standards. nasa.gov/. 
References 
Purvis, C. K., Garrett, H. B., Whittlesey, A. C., and Stevens, N. J., 1984, Design Guidelinesfor Assessing and Controlling 
Ferguson, D. C .  and Hillard, G. B., 2003, Low Earth Orbit Spacecraft Charging Design Guidelines. NASA TP-2003- 
1 
SpacecraJ Chargfng Effects, NASA TP-0236 1. 
2 12287. 
2 
3 
American Institute of Aeronautics and Astronautics 


NASA STD-4005: The LEO Spacecraft Charging Design Standard

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