Protecting Space Systems from Lightning

Protecting Space Systems from Lightning

Alexander F. Rivera, Harry C. Koons, Richard L. Walterscheid, Richard Briët

Despite overcast skies and rain, countdown began as usual at Cape Canaveral Air Force Station in Florida on March 26, 1987. The Atlas-Centaur 67 rocket carrying a naval communication satellite awaited launch. Some observers, concerned about the weather, questioned the wisdom of moving forward, but others dismissed potential danger as minimal. After smooth ignition, the rocket arced into the sky. Then, as it passed through clouds, it triggered a lightning discharge.

Electric current flowed down the body of the rocket and its wiring, scrambling data in its guidance computer. Using erroneous data, the computer commanded maximum tilt to the thrusters. This extreme steering action destroyed the rocket.

The failure of the Atlas-Centaur 67 echoed the difficulties plaguing the Apollo 12 vehicle shortly after its launch in 1969. Lightning had also struck that mission and corrupted its guidance system. Fortunately, the astronauts took control and saved the mission. Like Apollo 12, the Atlas-Centaur 67 mission served as an expensive lesson on the hazard lightning presents to a space system.

Powerful enough to threaten everything on Earth, lightning can cause severe damage to space electronics (see sidebar, The Nature of Lightning"). The Aerospace Corporation conducts research to minimize this danger. Advances at Aerospace in measuring and predicting lightning and incorporating protection into space-system designs have reduced the likelihood of lightning damage to satellites and launch vehicles and have improved the cost efficiency of activities undertaken to mitigate risk during storms.

Aerospace scientists serve on a Lightning Advisory Panel for the U.S. Air Force and the National Aeronautics and Space Administration (NASA). This panel establishes Lightning Launch Commit Criteria—rules for making a launch decision when atmospheric conditions or electric-field measurements indicate that hazardous fields may be present along a planned flight path.

Cloud Electrification: The Cause of Lightning

Protecting a space system calls for an understanding of what causes lightning. A strike results from cloud electrification, which occurs when vertical movements of air within a cloud separate positive and negative charges (see sidebar, Charge Separation). When charge separation produces an electric field with a strength that exceeds the breakdown value for air, "natural" lightning can take place. (The breakdown value is the field strength at which an electrical discharge will occur.) Natural lightning can propagate between charge centers within a cloud, from one cloud to another, or from a cloud to the ground.

Lightning can terminate on a conducting body in the electric field, or it can pass through such an object on its path to the ground, between clouds, or between charge centers within a cloud. The object may simply be in the way of a natural lightning stroke, or its presence may actually induce the stroke.

An induced stroke is called "triggered" lightning. For a vehicle struck after launch, lightning is much more likely to be triggered than natural. After launch, a rocket is exposed to the threat of lightning triggered by the presence of the launch vehicle itself and its long, conducting plume, which together can locally enhance the atmospheric electric field to its breakdown value. Triggered lightning, resulting from conditions not necessarily conducive to natural lightning, is the greatest threat to vehicles and payloads during ascent. Natural lightning is the greatest threat at the launch site.

The largest electric fields are found in tall clouds where strong embedded updrafts sustain heavy rain and strong vertical development. The most powerful of these clouds are cumulonimbus clouds, the only important clouds in natural lightning. Simply put, lightning-producing cumulonimbus clouds are thunderstorms, and the greatest threat to vehicles from either natural or triggered lightning is associated with their strong electric fields.

Cloud electrification occurs when vertical motions within a cloud separate positive and negative charges. When this separation produces an electric field in excess of the breakdown value for air, lightning can occur. According to one theory, charge separation takes place within a mixture of particles that includes graupel (soft hail or snow pellets), ice crystals, and water drops. Cloud dynamics and microphysics usually limit the strongest charging to a region extending from the freezing altitude upward to the altitude where temperatures reach approximately -10 degrees Celsius.

Usually the lower part of a cumulonimbus cloud acquires a negative charge (although there may be a pocket of positive charge near the cloud base). The negative charge aloft induces a positive charge in the ground. The electric field from this charge separation accelerates free electrons until they can strip electrons from air molecules, a process known as ionization. When the field becomes large enough, an ionized channel forms, through which the negative charge is lowered to the ground. (Keep in mind that electrons are not "lowered" to the ground—they actually move only a few meters. "Charge is lowered to ground" is commonly taken to mean that current neutralizes about the same amount of charge at either end of the lightning channel.) A cloud-to-ground lightning discharge then takes place. About 10 percent of the time, the bottom of the cloud is positively charged and a positive charge is discharged to ground.

Observing a lightning stroke, one may note numerous pulses. A single flickering bolt may actually be dozens of strokes occurring in less than two seconds. The first faint discharge, a "stepped leader," proceeds zigzag from cloud to ground. This is followed by a bright return stroke moving back up the channel from ground to cloud. The peak current in the return stroke can be huge—hundreds of thousands of amperes. Intense heating of the channel produces a strong, outward-moving pressure wave heard as thunder.

Natural Lightning

Natural lightning is usually associated only with cumulonimbus clouds, whereas triggered lightning is associated with a number of weather conditions. Charge separation in the weaker updrafts in a variety of layered, rain-bearing cloud types can produce significant electric fields, especially in the mixed-phase (water-and-ice) regions near and above the freezing altitude. Thus, rain clouds that pose no threat of natural lightning can pose a significant threat of triggered lightning.

Knowing about what conditions cause lightning, we can anticipate its likelihood in launch planning. Extensive precautions can better protect both objects and people from the powerful danger lightning poses.

To address the threat of natural lightning, which is a greater threat before launch, researchers measure lightning strikes, then predict where and when future strikes may take place. Thus a natural-lightning protection strategy can be developed. Because triggered lightning, a greater threat during ascent, can result from a variety of weather conditions, a protection strategy for it consists of rules that identify conditions under which launches should be postponed.

Advances in research cannot completely remove the threat of natural lightning. If lightning strikes close enough to a system on a launchpad, damage can occur. Furthermore, inaccurate prediction can have costly consequences—false alarms and unnecessary prelaunch testing.

Often, equipment is tested after a natural lightning strike—it is actually retested—to determine the extent of damage. Sometimes the uncertainty about whether damage has occurred is so great that much expensive retesting is conducted with no benefit. Developing plausible predictions and minimizing the wasteful results of inaccurate predictions requires accurate measurement of the lightning energy impinging on a space system on a launchpad.

Measuring Natural Lightning

A national system of lightning detectors (the National Lightning Detection Network, operated by Global Atmospherics, Inc.) provides information on lightning strikes. It identifies strike locations with a level of accuracy satisfactory for most commercial purposes—analysis of insurance claims, determination of construction risk—but not precise enough for a launch site.

Aerospace and various contractors met with marginal success when they used data gathered by the detection system. They tested and retested many space systems before launch at costs of millions of dollars, usually revealing no damage. Uncertainty costs much time and money; the space community needed a more accurate monitoring system. One estimate put the amount of unnecessary testing as high as 95 percent, while a tally made in 1997 showed that 7 out of 17 prior Titan launch vehicles incurred some degree of lightning damage.

The hybrid on-line lightning monitoring system is bolted to a launchpad so that its sensors can monitor the same lightning-generated fields that illuminate launch vehicles and spacecraft. (SRI International)

In 1994 Aerospace proposed a new monitoring system, known as the hybrid on-line lightning monitoring system. Its design required an exhaustive study of the nature of lightning and the concerns of launch vehicle operators. The hybrid online lightning monitoring system determines the severity of natural lightning strikes to enable decisions about whether launch vehicles and satellites should be tested after strikes. The system comprises sensors that respond to lightning as do the sensitive circuits on launch vehicles and satellites. A sensitive electric-field sensor detects energy much as a radio receiver does; surface current sensors produce readings that correlate with energy that penetrates shielding. The monitoring system provides clamp-on current probes to monitor the imparted currents in the actual launch vehicle cabling.

Other on-line lightning monitoring systems have been deployed to support space launch operations. They are based either on analog technology that provides continuous monitoring but lacks actual waveform information, or on digital technology that provides detailed waveform information but may miss major lightning events because of "dead time" inherent in its process. The hybrid concept proposed by Aerospace combines the two technologies into one integrated system. This design offers continuous monitoring of lightning-induced electromagnetic effects and also provides detailed waveform information on selected significant lightning events.

A redundant recording system with up to 16 data channels captures the information by two separate means. In the first method, a waveform digitizer samples the signals at submicrosecond intervals and records the first fraction of a second of the signal. Engineers use the waveform characteristics to determine the exact nature of the lightning threat. The second method functions as a fail-safe backup if the digitizer misses the strongest part of the lightning strike. A special circuit remembers the highest electrical level attained every second. This redundancy guarantees consistent measurement of the peak power in a lightning strike.

Engineers review the data and compare susceptibilities to the lightning-caused stress levels with their electromagnetic models of the space system. They use this information to quickly and accurately make a launch or retest decision within a launch time window. To help automate the decision-making process, Aerospace developed a method called the chain algorithm. The algorithm, which takes into account the particular environment at the launch installation, uses specific damage data, historical data accumulated in a database, and real-time, correlated multisensor data to instantly provide the critical determination of launch or retest feasibility (see sidebar, The Chain Algorithm).

Predicting Natural Lightning

With information about past lightning, scientists may predict future strikes. No one can know exactly when or where natural lightning will strike, but more than 100 years of statistical studies show that it is more likely in some places than others, and in certain seasons and times of day.

A map of lightning strikes in the United States shows Cape Canaveral is near the region of greatest summer activity. If lightning probability were the sole criterion for launch site selection, Cape Canaveral would be an unlikely choice. Obviously, many other factors, such as public safety, national security, and launch vehicle performance, outweighed lightning risk in site selection. Even with the tough environment at Cape Canaveral Air Force Station, however, launches can be scheduled at times with less lightning risk, such as winter (see sidebar, Launch Scrubs from Lightning).

Left: U.S. lightning activity map. Activity varies greatly, with minimums along the west coast and maximums in Colorado and Florida. Right: Lightning activity at Cape Canaveral Air Force Station charted according to time of day and time of year. Numbers associated with portions of the graph denote probability of occurrence of thunderstorms, expressed in percent. For example, thunderstorms can be expected 25 percent of the time at 4 p.m. any day in July. The best time of day to launch rockets is 7 a.m., when thunderstorm probability is lowest; the best months for outdoor projects are October through February.

Weather reports provide advance warning that enables personnel to take precautions and avoid natural-lightning damage. Threats can even be determined on a minute-by-minute basis. A device called a field mill measures the electric field strength near Earth's surface. The greater the surface field strength, the greater the electrostatic field generated by buildup of charges in the clouds. Fields with more than 10,000 volts per meter indicate an imminent lightning event. A lower level triggers an alarm calling personnel to shelter (see sidebar, Electric Field Mills).

Unfortunately, even several days' warning does not always permit movement of space resources in time to avoid lightning. A rocket on a launchpad may not launch during a storm, but it still must weather the storm. Lightning measurement studies must therefore focus strongly on the amount of lightning-driven electrical stress that a rocket receives during the period of time it must sit on the pad.

Protecting Space System Equipment

Knowing where and when natural lightning is likely to strike helps the development of an equipment-protection strategy. Methods of protecting equipment from lightning fall into three categories: grounding, shielding, and blocking.

The drawing above depicts the four tall towers that surround pad 40 at Cape Canaveral. A network of stainless-steel wires provides a good grounding path for protection from lightning. The cabling must be strong enough to survive hurricanes and the corrosive effects of ocean spray and rocket exhaust.

Grounding. Lightning rods provide the primary form of grounding; they have served as protection for centuries. Their use is based on the premise that lightning will be attracted to grounded metal rods positioned at a higher point than the structure being protected. The lightning current takes a defined path from the top of the rod to the ground—thus the current is grounded and it avoids the structure. Historically, the most effective lightning rods were tall and tapered to a point.

At times lightning will bypass a lightning rod and instead hit a low, nonpointed structure. Electrodynamics, the theory of rapidly varying fields, is used to explain this phenomenon. Aerospace is working with finite-element electromagnetic codes to analyze the dynamic effects of lightning with the goal of providing more protection at lower cost. The intent is to get the lightning current to ground with a minimum of components. Current protection systems require much more than a simple lightning rod to provide adequate grounding of incoming lightning strokes.

In this photograph of pad 40, a Titan rocket launches through the central opening in the cable netting. The large white insulators on the towers prevent lightning energy from being carried to the launchpad.

A tent of wires over the structure to be protected would work more effectively than rods to supply grounding, while a solid metal dome would give the best grounding protection. Designers proposed a dome for pad 40, the Titan launchpad, at Cape Canaveral. Lightning could damage payloads, costing a significant amount of money. However, the impracticality of a dome for a large structure such as a launchpad together with the billion-dollar cost precluded acceptance. Instead, a net of stainless-steel wires offered a relatively economical solution. Aerospace provided analysis and experimental data used in determining the required arrangement of the wires, which are supported by four giant towers.

In this system of towers and wires, giant insulators situated atop the towers prevent the lightning current from passing down the towers. They protect not the towers, but the sensitive electronics in the launchpad near the base of the towers, where the lightning current is carried. The danger that lightning will not be attracted to the wires but will attach to the towers or the launchpad persists, however; there will always be a possibility, albeit remote, that such an event could occur.

If lightning does strike the wires, it will generate a tremendous electromagnetic field, posing yet another threat to the electronics. Humans are generally immune to this field, but electronics can readily be damaged. Shielding keeps the electronics safe from these fields.

Shielding. Continuous sheets of metal welded or bolted together constitute standard electromagnetic shielding. In a building that uses standard shielding, special metal doors with metal seals provide complete shielding. Unfortunately, costs often do not permit the construction of buildings with this type of shielding. The metal in conventional buildings can provide some shielding, but the exact quantity is difficult to determine. Conventional buildings contain gaps, and shielding measurement must consider these gaps. Shielding measurements of intentionally shielded buildings assume no gaps are in the building's shielding. Assessing that assumption involves measuring the effectiveness of the shielding material.

The shielding test of the Payload Processing Facility at Vandenberg Air Force Base utilized a 180-centimeter-diameter magnetic-loop transmitting antenna driven by a 400-watt amplifier. The transmitted energy was scattered by all metal components in the structure, including wires, pipes, and beams. The test was conducted to investigate how well the room's shielding protected a satellite from powerful electromagnetic radiation comparable to the threat a lightning strike would pose.

Aerospace developed a technique that could measure complete building shielding via a powerful signal source connected to a large transmitting antenna outside the building. Prior to testing, an exhaustive survey is made of sensitive equipment. Then a sensitive receiver inside the building detects energy that leaks in. The test is arguably the most accurate yet, but it has pitfalls—for instance, the powerful transmitter poses its own damage threat and must be carefully controlled.

Blocking. Lightning energy that damages electronic components usually travels by wire. The only way to stop a powerful lightning pulse moving down a wire is to place a sturdy component in its way. The strongest component, a spark gap, can reduce the millions of volts in a lightning bolt to a few thousands or hundreds of volts. Although spark gaps adequately protect phone and power lines, modern electronics require more protection.

Metal-oxide varistors reduce spike voltage from thousands and hundreds of volts to tens of volts. (A varistor is a resistor whose resistance depends on the applied voltage.) Special diodes, including Schottkey diodes, transzorbs, and Zener diodes, protect the most sensitive electronics. These diodes work well on most electrical interfaces, but load down or destroy the signal of special sensors and sensitive radio receivers. A new type of limiter, a PIN (positive-intrinsic-negative) diode, recently entered the market, however, and it can stop thousands of volts yet provides only a minimal load to signals. Aerospace has qualified PIN limiters for space use.

Long current filaments in a lightning strike may generate beams of electromagnetic energy that radiate into space. These beams may be responsible for the upper-atmospheric phenomena known as jets and sprites. The beams may also be responsible for some anomalous readings by satellite sensors, so an important area of research is what effects lightning may have on a satellite passing above a storm.

Component Damage and Radio Interference

In addition to working in the fields of shielding and blocking, Aerospace conducts other forms of natural-lightning research. Lightning-generated radio interference and the susceptibility of electrical components to lightning damage are two of the more important areas.

The quick pulses of a lightning strike produce a broad spectrum of radio waves that can interfere with virtually any form of radio communication. Advances in communication technology have led to sophisticated methods of eliminating radio noise, and better definitions of the myriad forms of lightning-generated radio noise will enable the development of advanced radio receivers that cancel the noise. Some unusual forms of interference have not been associated with any specific source. Simulations at Aerospace have indicated that intense directional radio beams could result from some forms of lightning. These beams may be responsible for some of the unusual interference.

Electrical components of space systems are the most common casualties of lightning, and learning their susceptibility is the first step in determining the susceptibility of a system. With the exception of data obtained from lightning protection devices, however, component damage information is notoriously variable and hard to obtain. A sensitive component must be tested in a setup that accurately simulates its operational state.

To gain statistically accurate data, given all the variables involved, researchers must test hundreds of components. Unfortunately, leading-edge technology components are expensive and in short supply. Researchers often cannot test a large quantity, so Aerospace developed procedures to determine accurate damage levels using a minimum of components. This solution involved careful simulations of component breakdowns and careful selection of test conditions to produce significant data with no redundancy.

Triggered Lightning

Triggered lightning is a vehicle-initiated discharge of atmospheric electricity that connects to a cloud charge center near the vehicle. In order for triggered lightning to occur, the following conditions must be present:

an ambient electric field that is high (although its strength may be far below the breakdown value)
enough energy stored in the field to propagate the discharge
a strong enhancement of the field at the vehicle, to trigger the strike

Field enhancement occurs in two ways—through the presence of a long conducting body (the rocket itself, together with its plume) and through the curvature of the rocket's surface, principally at its forward end.

Field Enhancement via a Conducting Body

The electric field in a region is proportional to the spatial concentration of surfaces of constant potential within the region (the denser the spacing, the greater the field). An electric field cannot penetrate a conductor, so when that conductor is an ascending rocket and its plume, the potential drop that affects electric fields at the surface of the vehicle occurs not within the vehicle, but a short distance outside it.

The high conductivity of the rocket and its plume causes the fields at the leading end of the rocket and the trailing end of the plume to have similar electric potentials; the voltage difference between these points is essentially zero. This means that the potential at the upper end of the rocket is approximately the same as the potential of the undisturbed ambient field at the lower end of the rocket's conducting plume.

A short distance above the vehicle, however, the field is similar in intensity to the undisturbed field. The potential difference that existed over the combined extent of the vehicle and its conducting plume before the vehicle was introduced into the ambient field is now condensed into the much shorter distance between the tip of the rocket and the undisturbed field a short distance above it. This concentration of potential difference greatly increases the electric-field strength at the tip of the rocket.

triggered lightning requires a high ambient field

Triggered lightning requires a high ambient electric field, a sufficiently large amount of energy stored in the electric field, and a strong enhancement of the electric field present at the vehicle. The conductivity of a launch vehicle causes a "draping" condition. The undisturbed potential difference that existed over the combined extent of the vehicle and its conducting plume becomes concentrated into the much smaller distance between the rocket's tip and the undisturbed field a short distance above it. This concentration of potential difference can greatly increase the electric field at the rocket's tip.

In this type of field enhancement, then, electric fields can be said to drape around the rocket as a result of the way in which levels of constant electric potential near the vehicle tend to conform to the shape of the vehicle. When this phenomenon is depicted graphically, curves representing surfaces of constant electric potential flow over and around the vehicle in a pattern like folds in a piece of cloth; hence the term "draping."

Field Enhancement via Surface Curvature

The second kind of field enhancement results from the curvature of the rocket's surface at its tip. An electric field at the curved end of the vehicle is typically of a higher strength than fields associated with flatter portions of the launch vehicle. The reasons behind this phenomenon have to do with the way charge is distributed at the surface of a conductor.

Charge at the surface of a conductor distributes itself until the net electrical force directed along the surface on charged particles is zero. This balancing out occurs when every point on the surface of the conductor is at the same electrical potential; the surface is said to be an "equipotential."

For example, consider a charged sphere; its surface is an equipotential. The sphere is surrounded by equipotential surfaces that are spherical, so the charge all appears to be located at a point at the center of the spherical conductor.

Assume now that our sphere is deformed into a highly eccentric ellipsoid—a solid shaped something like a football. When observed from some distance, the charge still appears to be located approximately at the center of the charged ellipsoid, and the equipotential surfaces are nearly spherical. Thus, at the ends of the ellipsoid, the potential surfaces must be more crowded together than on the flanks. The result is a stronger electric field at the highly curved ends than on the relatively flat flanks.

The situation of a conducting body, like a rocket, "embedded" in an ambient external electric field is more complicated, but the general result is the same: higher-strength fields tend to be associated with stronger curvature. (Note that this relationship is not precise. The field at any point is not a strict function of the local curvature.)

The Strike Occurs

Once a triggered-lightning discharge is initiated by the enhanced electric field, it propagates toward the region of charge that created the field, carrying with it the electric potential of the vehicle. This increases the field between the tip of the discharge and the cloud charge. When the potential difference between the tip of the discharge and the cloud charge exceeds the breakdown value, the lightning strike occurs.

The two forms of field enhancement, draping and surface curvature, are separate phenomena. Their effects are additive. Combined, they greatly increase the electric field at the top of the vehicle, heightening the likelihood of an induced lightning strike.

When a sphere deformed into an ellipsoid is observed from a distance, the charge still appears to be located at the center of the original shape, and the equipotential surface is nearly spherical. Since the flat flanks of the ellipsoid are considerably farther from the equipotential than the curved ends, there must be a higher-strength field at the curved ends. The presence of a higher-strength field at the curved tip of a rocket increases the likelihood of a triggered-lightning strike.

With its plume, the Saturn V vehicle that launched the Apollo 12 space capsule had a conducting length of 300 meters, and it tapered to a 10-centimeter-radius nose cap. The combined effect of field draping and surface curvature was estimated to give a 320-fold increase of the electric field. This enhancement would have produced a breakdown field in moderate electric fields and almost certainly explains the strike induced by Apollo 12.

For the Atlas-Centaur 67, field draping was estimated to give a 30- to 40-fold increase of the electric field and give fields at the nose of the vehicle strength to induce lightning in a field aloft of 50 or more kilovolts per meter. Fields aloft of this magnitude are consistent with the size of the fields measured at the ground during the Atlas-Centaur 67 incident (see sidebar, Two Struck by Lightning).

Launch Rules and Constraints

Launch weather officers analyze meteorological information to assess the possibility of triggered lightning and decide whether a launch should proceed. Launch rules have been created to document guidelines for making this decision, and they have frequently been updated to reflect the changing awareness of what constitutes a threat to launch safety. Prior to the Apollo 12 incident, the only lightning-related rule in effect urged the avoidance of clouds that produce natural lightning.

Following the incident, a committee of atmospheric-electricity experts developed a set of rules that reflected our knowledge of triggered lightning in 1969. The Post-Apollo 12 Launch Rules recognized the presence of large electric fields outside thunderstorms and anvil clouds, and they identified cloud types known to generate electric fields. The launch rules in effect at the time of the Atlas-Centaur 67 lightning incident in 1987 were basically the same as the Post-Apollo 12 Rules, except for a changed altitude reference.

Shortly after the Atlas-Centaur 67 loss, the U.S. Air Force asked Aerospace to study the weather conditions at the time of the incident, as well as the existing launch vehicle constraints. An Aerospace Lightning Review Committee published a set of new rules, known as the Post-Atlas-Centaur 67 Launch Constraints, in 1987. These constraints recommended delaying a launch under any of the conditions identified in a set of specific, quantitative criteria based on ground-based and airborne field-mill measurements. In subsequent years, panels that have included Air Force and NASA experts have met to recommend and update Lightning Launch Commit Criteria. The effort to ensure that the best launch rules are in place is an ongoing one, and it strives to maximize launch safety while allowing launches to proceed according to schedule in a reasonable manner (see sidebar, History of the Cumulus Cloud Rule).

Summary

Lightning is a complex phenomenon with the potential to substantially affect space projects. Although we know it is the result of the development of an electric field that comes about through charge separation in clouds, we are learning more about the details of how lightning occurs. Complicating matters is the important distinction between natural and triggered lightning. A vehicle awaiting launch may be struck by natural lightning, but a vehicle in its ascent is much more likely to be struck by lightning that it has induced.

Lightning-related expenses and delays to our nation's space-system launch activities decrease every year as a result of ongoing research at Aerospace. Effective use of grounding techniques, protective electromagnetic shielding, and voltage-limiting components help make space systems more resistant to lightning damage. Aerospace also studies the susceptibility of electrical components to lightning damage and the effects of radio noise generated by lightning.

Accurate monitoring of lightning, such as that performed by the hybrid on-line lightning monitoring system, helps eliminate uncertainties, and, together with accurate weather prediction, goes a long way toward avoiding possible failures. The ongoing development and revision of Lightning Launch Commit Criteria also make an important contribution to our effort to protect space systems. Lightning, like any force of nature, can never be fully controlled—but Aerospace works to minimize its threats to the utilization of space.