The problems encountered when protecting rockets and launch operations from the dangers of lightning are discussed. This reveals the need for a mesoscale network for observing important parameters that indicate lightning danger, as well as the need to develop a set of rules for forecasting potential lightning danger. Before developing methods to inhibit the generation of electricity inside thunderclouds, it is imperative that the charge seperation mechanism be thoroughly understood. The present state-of-the-art of lightning suppression uses either metallic chaff fibers to produce a continuous discharge current or rocket propelled projectiles to discharge the thundercloud with artificially triggered lightning

Ruhnke, Lothar H.

English

Embry-Riddle Aeronautical University

The Space Congress® Proceedings 1971 (8th) Vol. 1 Technology Today And Tomorrow Apr 1st, 8:00 AM Atmospheric Electricity Problems Lothar H. Ruhnke Physicist National Oceanic and Atmospheric Administration, Environmental Research Laboratories, Atmospheric Physics and Chemistry Laboratory, Boulder, Colorado Follow this and additional works at: https://commons.erau.edu/space-congress-proceedings Scholarly Commons Citation Ruhnke, Lothar H., "Atmospheric Electricity Problems" (1971). The Space Congress® Proceedings. 2. https://commons.erau.edu/space-congress-proceedings/proceedings-1971-8th/session-3/2 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 commons@erau.edu. ATMOSPHERIC ELECTRICITY PROBLEMS AT KENNEDY SPACE CENTERDr. Lothar H. RuhnkePhysicist National Oceanic and Atmospheric AdministrationEnvironmental Research LaboratoriesAtmospheric Physics and Chemistry LaboratoryBoulder, ColoradoABSTRACTas the fore- Be- theThe problems encountered when protecting rockets and launch operations from the dangers of lightning are discussed. This reveals the need for a mesoscale network for observing important parameters that indicate lightning danger, as well need to develop a set of rules for casting potential lightning danger fore developing methods to inhibit generation of electricity inside thunder­ clouds, it is imperative that the charge separation mechanism be thoroughly under­ stood. The present state-of-the-art of lightning suppression uses either metal­ lic chaff fibers to produce a continuous discharge current or rocket propelled projectiles to discharge the thundercloud with artificially triggered lightning.PRESENTATIONLightning, either by direct hits or by electric or magnetic induction, endangers launch vehicles as well as ground support operations. Nearby lightning strikes, through induced currents, can easily af­ fect complex electronic equipment and cause time-consuming checking and repair procedures. Explosives can also be ig­ nited by electrical sparks and strong currents. Last but not least, lightning endangers people.There are three ways to cope with these dangers: protection, prediction, and modi­ fication. Protection against lightning is an engineering problem. Usually equipment as well as people are considered to be suf­ ficiently protected against lightning cur­ rents as well as against electrical induc­ tion when they are inside a Faraday cage. Such shielding is usually insufficient pro­ tection against magnetic induction, un­ less special precautions are used. The problems of protection become particularly difficult if a direct hit by lightning must be anticipated. Electrical currents of lightning strokes are in the order of 10,000 to 100,000 A and last for about 100 microseconds. Even a small fraction ofthis current can burn out switches, cables, and connectors, not to speak of sensitive components of electronic circuitry, as semi­ conductors, capacitors, or induction coils. Although engineering techniques can cope with many of the protection problems, one must realize that there are limits in the procedures to protect against lightning.For predicting lightning danger, one needs, as in weather forecasting, a network to survey a suitable set of parameters and, additionally, a set of rules based either on physical laws or on a history of obser­ vations. Then, when potential lightning danger is forecast, equipment and people can be moved to a safe place and the oper­ ation delayed until the danger is over. The effectiveness of this approach is lim­ ited, because delays are often intolerable or very costly, and equipment sometimes can­ not be moved or only moved very slowly. Furthermore, forecasts of lightning danger are not very accurate with the present state-of-the-art, which leads to a high rate of false alarms as well as to insuf­ ficient warning of real danger.The design of a prediction system for lightning danger is not a straightforward engineering task, because some of the in­ strumentation needed is not commercially available and needs to be designed; also the forecast rules still need to be devel­ oped either empirically from observational data or from the physical laws that govern the development of thunderstorms and light­ ning. In contrast to the prediction sys­ tem for large scale weather phenomena, thunderstorms have lifetimes of only about 1 hour and extend over only about 5 miles. This makes it necessary to establish a mesoscale observational network with sen­ sors spaced about 2 to 5 miles apart and to gather a set of data for each 10-minute period. This necessitates a rapid data processing and analysis system which has not been developed yet.Once a good system for surveying and fore­ casting lightning danger exists, it is3-11necessary to ask whether we must let nature take its course or whether we can purpose­ fully modify and influence that what causes danger to life and equipment. Here we go to the root of the problem by treating the cause. This approach is relatively new, if we neglect all the attempts to modify light­ ning danger by praying or by wishful think­ ing. Unfortunately, the cause for lightning and high electric fields inside clouds is as yet unknown. Therefore, our efforts to eliminate or diminish occurrences of light­ ning should be directed strongly towards basic research on the fundamental processes of the generation of electricity inside clouds. Such an approach, however, is not likely to be favored by an organization like the Kennedy Space Center, in which launch operations, engineering, and technology are the major theme. Yet, without basic research, there can be no significant pro­ gress toward eliminating lightning danger to launch vehicles and launch support in- stallations.We should therefore attempt to explore the mechanism by which electrical charges are generated in clouds. This 200 year old problem has persistently resisted a solu­ tion despite the sincere efforts of many noted scientists. A strongly mission ori­ ented research project is necessary; it must be founded on sound physical concepts and make use of modern philosophies and technologies. Such a research effort should be well directed by competent management and should involve the major U.S. centers of competence in atmospheric electricity. As is generally true in bagic research, one cannot predict with certainty success as well as time and money expenditures. But I believe the time is right to solve the problem of charge generation and to find a means to eliminate charge accumulations.At present, the approach to diminish light­ ning strikes at KSC is also a mission ori­ ented one. Whenever hazardous conditions exist inside a cloud, e.g., electric fields of such a magnitude that they cause natural lightning or lightning that can be trig­ gered by a rocket and thereby endangering the rocket, the cloud or some portion of it should be discharged artificially.To discharge a cloud one can disperse small metallic fibers, which produce electrical corona currents in strong electric fields. Such corona currents will dissipate the cloud charges and will inhibit the build­ up of dangerous conditions. Preliminary field tests by the Atmospheric Physics and Chemistry Laboratory of NOAA have shown the feasibility of suppressing lightning by this method (i). The disadvantage ofthis method is that such metallic fibers scatter certain electromagnetic waves, which can interfere with vital communica­ tions between a rocket and the ground. Using this method therefore requires good coordination between communication engi­ neers and cloud physicists in the design of a workable lightning suppression system.Other schemes that promise success include the use of projectiles to trigger light­ ning in a controlled manner, such that no natural or unintended lightning occurs. Feasibility studies were made using small rockets that were connected to the ground during fliqht by a wire which triggered lightning (2).One project conducted by Atmospheric Physics and Chemistry Laboratory of NOAA, under NASA sponsorship, uses a small rocket, "Mighty Mouse," that triggers, at will, lightning inside clouds. Tests conducted in 1970 at Socorfo, N. M., (s) showed very encouraging results not only to dis­ charge some portion of the thundercloud but also to study, in general, the mecha­ nism by which rockets trigger lightning. Such studies are necessary to assess the danger of large rockets, like the Saturn V, unintentionally triggering lightning. The Apollo 12 lightning incident showed the necessity to understand fully the phys- cal conditions that lead to lightning.It is certain that in the future more con­ cepts will be proposed and tested to harm­ lessly dissipate electricity that is pro­ duced and stored in a thunderstorm. It is also certain to me that the atmospheric electric problems at KSC will be solved sufficiently only when the physics of the charge separation process inside clouds is well understood, and a means to control this process is found.REFERENCES(1) Kasemir, H. W. "Lightning Suppression by Chaff Seeding." ESSA Final Report on USAECOM Project 67-93906, June 1968.(2) Newman, M. M. "Use of Triggered Light­ ning to Study the Discharge Process in the Channel and Application V L F Propagation Studies." Problems of Atmospheric and Space Electricity. S. C. Coroniti ed. (Elsevier Publ. Co. Amsterdam.) 482-490, 1965.(3) Kas^fir, H. W. "Basic Theory and Pilot Experiments to the Problem of Discharging Electrified Clouds by Rocket-Triggered Lightning Discharges." NOAA Technical Re­ port (U. S. Government Printing Office, Washington, D. C.), April 1971.3-12

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