d ! ? _'" / /_'_' i i_ I_ rv__ \/ " .. .... / NATIONAL AERONAUTICS AND SPACE ADMINISTRATION '_- ,# (NASA-TM-X-628_a) ANALYSIS OF APOLLO 12 N72-73_78 LTGUINING INCIDENT R. Godfrey, et al (NASA) feD, 197 87 p Unclas 'r - / ANALYSIS OF APOLLO 12 LIGHTNING INCIDENT _,_, ._e-W_ PREPARED BY MARSHALL SPACE FLIGHT CENTER KENNEDY SPACE CENTER I MANNED SPACECRAFT CENTER _ y.,:..,.:. r :.- • • " _ i FEBRUARY 1970 NAtIONAl. INr-oIIMATION SBIVIC_ J ll, II. lil_Itllillt _i_ I_IIIIB _ & MSC-O15_O ANALYSIS OF APOLLO 12 LIGHTNING INCIDENT PREPARED BY Marshall Space Flight Center Kennedy Space Center Manned Spacecraft Center R. Godfrey Manager, Saturn Program Marshall Space Flight Center E. R. M_hews Man_er, Apollo Program Kenned Space Center _/ James A. McDi_tt _er, Apollo Spacecra_ Program Manned Spacecra_ Center APPROVED BY Rocco A. Petrone Apollo Program Director NATIONAL AERONAUTICS AND SPACE ADMINISTRATION January 1970 ii TABLEOF CONTENTS Section Page PREFACE . • • • • • , • • • • • . • • • • • • • • • • • • • • iv SUNMARY ......... 1 2 LIGHTNING PHOTOGRAPHS ..................... 3 ATMOSPHERIC ENVIRONMENT .................... 12 EFFECTS ON SPACE VEHICLE ................... 18 Spacecraft ......................... 18 Launch Vehicle ....................... 23 Launch Complex ....................... 24 CAUSE OF DISCHARGES 25 Electrostatic Discharge Theory ............... 25 Vehicle-Triggered Lightning Theory ............. 26 FLORIDA METEOROLOGICAL CONDITIONS ASSOCIATED WITH ELECTRIFIED CLOUDS ..................... 29 Effects of Atmospheric Con_tions on La_ch Window ..... 30 Criteria 31 _HICLE DESI_ CONSIDERATIONS ....... 37 Spacecra_ ........... .............. 37 La_ch _hicle 42 La_ch Complex ........... -J- t_'_oeoe••ee 4h CO_L_IO_ ...... 48 CORRECTI_ ACTION .... * 50 REFE_NCES _D BI_IOGRAP_ ..... 51 iii Section Page APPENDIX A m LIGHTNING AND RELATED INSTRL_4ENTATION ...... A-I APPENDIX B m EXPLORATION OF SOME HAZARDS TO NAVAL EQUIPMENT AND OPERATIONS BENEATH ELECTRIFIED CLOUDS . B-I APPENDIX C --CIRCUIT ANALYSIS ................ C-i Automatic Abort System Circuit Analysis .......... C-I Ordnance Circuit Analysis .................. C-2 PREFACE Appreciation is extended to the following personnel for their exper- tise and help in the understanding of the Apollo 12 lightning incident at the special December meeting of the American Geophysical Union in San Francisco, California. Dr. Louis J. Battan Dr. J. D. Robb Institute of Atmospheric Physics Lightning and Transients Research University of Arizona Institute Dr. S. C. Coroniti Dr. J. D. Sartor Panametrics, Inc. Laboratory for Atmospheric Sciences National Center for Atmospheric Research Dr. George A. Dawson Dr. E. L. Schuman Institute of Atmospheric Physics Research Laboratories University of Arizona Environmental Science Services Administration Dr. Hans Dolezalek Dr. William Scott Atmospheric Sciences Program Department of Atmospheric Sciences Office of Naval Research University of Washington Department of the Navy Dr. H. W. Kasemir Dr. Martin A. Uman Research Laboratories Research and Development Center Environmental Science Services Westinghouse Electric Corporation Administration Dr. L. B. Loeb Dr. B. Vonnegut Department of Physics Department of Atmospheric Science University of California, Berkeley State University of New York at Alb any Dr. Forrest Mozer Dr. William P. Winn Space Sciences Laboratory Laboratory for Atmospheric University of California, Sciences Berkeley National Center for Atmospheric Research Dr. M. M. Newman Lightning and Transients Research Institute /V & To other participants of this meeting, a special thanks is given for their analytical contributions and consultations which were gracious- ly offered during the analysis of the phenomena associated with the light- ning incident. Dr. Marx Brook Dr. E. Philip Krider New Mexico Institute of Mining NASA-NRC Resident Research Associate and Technology Manned Spacecraft Center Dr. Arthur A. Few Mr. Charles B. Moore Department of Space Science New Mexico Institute of Mining Rice University and Technology Dr. Donald R. Fitzgerald Dr. Richard E. Orville Air Force Cambridge Research Department of Atmospheric Science Laboratories State University of New York at Albany Dr. G. Freier Dr. E. T. Pierce School of Physics Staff Scientist University of Minnesota Stanford Research Institute V oj 1 SUMMARY The Apollo 12 space vehicle was launched on November 14, 1969, at 11:22 a.m.e.s.t, from launch complex BgA at Kennedy Space Center, Florida. At 36.5 seconds and again at 52 seconds, a major electrical disturbance was caused by lightning. As a result, many temporary effects were noted in both the launch vehicle and spacecraft. Some permanent effects were noted in the spacecraft and involved the loss of nine non-essential in- strumentation sensors. All noted effects were associated with solid-state circuits, which are the most susceptible to the effects of a discharge. Analysis shows that lightning can be triggered by the presence of the long electrical length created by the space vehicle and its exhaust plume in an electric field which would not otherwise have produced nat- ural lightning. Electric fields with sufficient charge for triggered lightning can be expected to contain weather conditions such as the clouds associated with the cold front through which the Apollo 12 vehicle was launched. The possibility that the Apollo vehicle might trigger lightning had not been considered previously. The Apollo space vehicle design is such that a small risk of trig- gered lightning is acceptable. In accepting this minimal risk for future flights, launch rule restrictions have been imposed with respect to opera- tions in weather conditions associated with potentially hazardous elec- tric fields. INTRODUCTION Before the Apollo 12 flight, the only consideration of the effects of lightning on the space vehicle was for the period prior to flight. The methods and procedures used to cope with possible lightning prior to launch have been in existence since the inception of the launch complex. The possibility of the vehicle becoming involved with lightning after lift-off was not a launch consideration, unless natural lightning activ- ity was actually present in the launch complex area. This report discusses the significant elements of the lightning in- cident during the Apollo 12 launch. The report is addressed to what hap- pened and why, and what meteorological conditions could produce lightning with the presence of the launch vehicle. This report also recommends action for minimizing the possibility of creating a similar incident on future Apollo flights. An assessment of the spacecraft and launch vehi- cle electrical design to determine the effects of lightning is included. The investigative results represent the combinedefforts of the ap- propriate personnel at the MannedSpacecraft Center, the Marshall Space Flight Center, and the KennedySpace Center. The primary contributions to the understanding of the physics associated with the incident and of howto apply the present knowledge of atmospheric electricity to the Apollo Programhave been provided by recognized experts in the field. A number of authorities on atmospheric electricity have enthusiastically and voluntarily provided consultation and literature in this area. LIGHTNINGPHOTOGRAPHS Twolightning incidents occurred on Apollo 12 as evidenced by the onboard data. The first incident, at 36.5 seconds, was recorded photo- graphically at many locations around the launch complex. Four motion picture camerasrecorded lightning discharge channels near the launch tower. These photographs, together with video-tape rec- ords from the abort advisory television camera (figs. 1 and 2), show two discharge channels. The duration of each scan in figure 1 is 1/60 second with 1 millisecond between scans. These photographs were obtained from video-tape records of the actual event. The bright lightning channel apparently saturated the vidicon tube in scan b, and the tube remained saturated for scans c and d. The image began decaying in scan e and re- quired four scans for total decay. Scan f shows the second lightning channel, which developed approximately 60 milliseconds after the first. One of the channels, located about 1500 feet from the launch umbilical tower, showed pronounced downward branching and appeared to last 50 milli- seconds in the motion picture photographs. Another channel, partly ob- scured by steam and clouds and about 100 feet from the launch umbilical tower, also lasted about 50 milliseconds. One frame from each of the motion picture cameras that recorded the lightning strike at 36.5 seconds are shown in figure 3. Table I shows the types of cameras used together with films, lens openings, and shutter opening angles. All cameras were operated at a speed of 24 frames per second. Figure 4 shows the camera sites and the approximate locations of where the channels contacted the ground. I I 0 f_ _ m .1_ oM ,--I o_ o_,_ o_ o_ O m rD _D 0 0 0 4_ 0 _rx oO "_ OJ ,-I f-I o4._ I-I O3 ._o_ _ O .,.-I 0 I I _r-ll I I I.-I o_ % O4._ 0,1 0 0 0 0 O ! ._ 0 0_,._ I I-I 0 0 cO 0 0 0 % ,--t N C_ 0,1 .0 _1 o o _ _-_" e- 0 e- _J _J .o o 0 0 e- .o. E 0 _J _J x g e,J ! LI v I ._ ,o IJ. t-- -g o Z 6 c.) _n ..C c.3 GJ r-, aJ o t- c.) O I .I E g ,I c- I.i_ o °_ E .I X U ! ,,.-I .,C U 0o 0 ¥ ", Note: See Table I for camera details. ___..____.__----: _a .trom " IP.J Figure 2.- Lightning recorded at launch complex by camera D-120. 8 0_ u cJ_ "0 0_ CT_ _J 0 aJ W aJ 0 L- _J qJ 0 °_ i o ! c_ cJ I-I qJ 0 Z c_ 0 Q_ m o_ t_ I o Q_ c_ _J C_ 0 Z i0 Note: See table 1' for camera details. (c) Nevada all-sky camera. Figure 3.- Concluded. 11. North Lightning channel l_Television E-IO0 camera E_IOZ camera Launch umbilical tower Lightning C__i/_ Nevada camera D-120 camera Craw lerway Figure 4.- Camera locations and lightning channels on launch complex 39A. 12 ATMOSPHERIC ENVIRONMENT On November 13, the d_y before the Apollo 12 launch, an intense low- pressure trough in the upper atmosphere had evolved over the east central United States from the Great Lakes down the Mississippi Valley into the Gulf of Mexico.