The Space Congress® Proceedings 1976 (13th) Technology For The New Horizon Apr 1st, 8:00 AM Lightning -Apollo To Shuttle W. R. Durrett John F. Kennedy Space Center Follow this and additional works at: https://commons.erau.edu/space-congress-proceedings Scholarly Commons Citation Durrett, W. R., "Lightning -Apollo To Shuttle" (1976). The Space Congress® Proceedings. 7. https://commons.erau.edu/space-congress-proceedings/proceedings-1976-13th/session-4/7 This Event is brought to you for free and open access by the Conferences at Scholarly Commons. It has been accepted for inclusion in The Space Congress® Proceedings by an authorized administrator of Scholarly Commons. For more information, please contact [email protected]. LIGHTNING - APOLLO TO SHUTTLE W. R. Durrett John F. Kennedy Space Center ABSTRACT The lightning discharge that struck the Apollo 12 carefully for the protection offered, cost, spacecraft thirty-six seconds after launch pointed operational practicality, ruggedness, and safety. up a whole series of problems that called out for Nothing was considered "crackpot" at this stage. answers if the Manned Space Program were to Every solution was given the same screening. The proceed with minimum impact to future missions final choice was, as nearly always, compromise. and the crews that would fly them. This paper There were concepts that offered better pad traces the history of lightning study by the protection than the one selected, and concepts Kennedy Space Center from then to now with par­ that offered better rollout protection, but none ticular emphasis on the potential problems that that cost less or that did both jobs any better. may arise in the process of getting ready for and The design consisted of a folding mast (to allow carrying out the Space Shuttle Program. access in and out of the VAB doors) mounted on top of the hammerhead crane on top of the LUT, with a lightning rod on top. The assembly LIGHTNING - APOLLO TO SHUTTLE extended above the vehicle sufficiently so that a lightning stroke would terminate on the The experiences of the Apollo Program with lightning rod and not strike the vehicle itself. lightning strikes at the Kennedy Space Center This concept is known as the 1:1 cone of pro­ began with very little formality and with almost tection:- as long as the mast is higher above the no lost time. On May 25, 1966, the first Apollo tip of the vehicle than it is displaced from it vehicle rolled out of the Vehicle Assembly horizontally, the 1:1 concept is satisfied. Building. This was the 500F proof-test vehicle - Historically, the 1:1 cone of protection provides a full-scale mockup of a Saturn V moon mission an almost perfect protection umbrella from vehicle mounted on the Mobile Launcher and lightning striking anything under it, and it identical in size and weight to the real thing. proved so in Apollo - no flight vehicle was ever Its purpose was to provide a full dress exercise struck on the pad, although the LUT itself was of the Crawler and to validate the facilities at struck many times. When this occurred, the Pad A of Launch Complex 39. The rollout was a strike current passed from the lightning rod down success, and the vehicle was on the pad as of the mast structure, past the hammerhead crane that afternoon. Two days later, May 27, 1966, through wiping shoes (that allowed crane movement) the Launcher Umbilical Tower (LUT) on the Mobile and through the welded LUT structure and Mobile Launcher (ML) took a strike. The hook on the Launcher to ground. The whole pad area had an hammerhead crane on top of the LUT began dropping elaborate buried ground counterpoise of many in free fall as its brakes let go, and struck the copper cables, and at the pad the Mobile Launcher side of the second stage. The damage was not was connected to it by ground jumpers on each of severe, but the Apollo/lightning interface had the six outer pedestals that supported the Mobile begun. Examination showed the brake drum solenoid Launcher. There were, in addition, many other contacts welded open. ground paths from the structure by way of hyper- golic lines, fuel lines, and the multitude of The lightning protection design for Apollo had other installed paths that exist when a moon been adopted after consideration of many concepts rocket is connected to its ground support equip­ for protection of the vehicle during rollout and ment for checkout prior to launch. while at the pad. The concepts examined covered almost every possible approach:- masts along the There was no lightning instrumentation on the LUT crawlerway, balloons carrying grounded wires, for that first rollout, but by October of 1968, balloons carrying lightning rods, kites, folding for the first manned Saturn V (Apollo 8) rollout, screens enclosing the flight vehicle until launch magnetic slugs (to record peak stroke current) time, towed structures carrying shielding and a lightning stroke counter had been added to enclosures that moved back for launch, telescoping the lightning mast above the LUT's crane. The shrouds mounted on the LUT, removable grounded pad was under TV surveillance, but the video was shrouds mounted above the vehicle - the solutions not recorded. were literally legion. Each one was looked at 4-27 Apollo's busiest launch year was 1969. Five stroke current magnetic fields they have been vehicles went to the pads in that twelve-month exposed to, and the stroke counter could not be period* There had been no strikes since the. relied on to resolve every separate strike - its first one in 1966, but in 1967 and 1968 the pads reaction time did not exceed 0.1 seconds even were empty during the summer storm months, and when working. In those six strike days it is no LUT's had been there to be targets. This was not inconceivable that the complex may have taken not the case in 1969, but even so, no strikes to forty to fifty separate lightning strokes.) the complex were recorded, Apollo 11 took off on July 16 for its moon landing after being on The year 1972 again had vacant pads during the the pad for substantially the full 1969 storm summer; Apollo 16 launched April 17, .ami Apollo 17 sea,son 9 but it took no strokes. was on the pad from September 13 through December 6. There were two strike days in March, This period of bliss disappeared abruptly on the 5th and 31st. No damage resulted. November 9, 1969, when Apollo 12, thirty-six seconds into its flight, triggered a cloud-to- The lightning mast from Pad 34 was mounted on the ground stroke that momentarily put the space­ MSS in 1972. Wide and deep as well as tall, much craft's guidance system out of commission. The of the MSS was not inside the 1:1 cone of pro­ booster's guidance system, in command at this tection of the LUT's lightning mast and was point of the mission* was not disrupted, and the subject to being struck at almost any point on mission continued. It wasn't a strike on the pad, its upper surfaces. The mast gave it a single but the distinction didn't really amount to much; preferred attach point for a stroke. This from that day forward the.Kennedy Space-Center permitted accessible instrumentation to be became lightning conscious. mounted and also provided the flight vehicle on the pad with protection from an additional 1:1 The year 1970 was a repeat of 1967 and 1968 in cone. that there were no launches during the summer months:- Apollo 13 was launched on April 11 and (The tip of the MSS mast was 25 ft. lower than Apollo 14 did not rollout until November 9. the LUT mast and 130 ft. south of it when the There were no known strikes that year. MSS and LUT were both on the pad during checkout. This, of course, left the MSS mast as a secondary (The Mobile Service Structure, almost as tall as strike point, and as experience showed, it did the LUT, had been at its parksite south of the take a few low-energy strikes which came in from pads since 1965 when it was not on the pad for a generally southerly direction. The stronger checkout. It had magnetic slugs mounted on the strokes invariably went to the LUT mast.) various lightning rods that protected its vent stacks and extremities but their locations were The storms of 1971 had taught two lessons:- almost inaccessible and they had not been serviced improve instrumentation, and pay attention to regularly because of the hazard to servicing indirect lightning effects. Strike current that personnel. Although it is possible that it had went down the LUT mast to ground didn't go just been struck at the parksite, there was no valid . through the LUT. Some of it went across the data to support known strike activity.) swing arms and to ground through the skin of the vehicle and the MSS structure. This did no In 1971 the picture changed drastically. Storms direct damage to the bird, but the current in delayed Apollo 14's launch on January 31, but it the arm structures induced voltages in the was rainshowers, not lightning. Apollo 15 went umbilical cables leading from the LUT to the to the pad on May 11 and was launched on July 26. vehicle. Some of these cables ran for part of Its stay on the pad nicely spanned the lightning their lengths along the tops of the arm structures season, and in this two-month stretch, lightning and were thus exposed to the maximum induction hit the complex on six different days:- June 14, fields set up by the stroke current flowing in 15, and 25, and July 2, 19, and 21.