If lightning really never struck twice in the same place, Dr. Pedro Medelius's job would be a lot easier. But since bolts from the blue can hit wherever they please, figuring out what's been zapped within the 140,000 acres of NASA's Kennedy Space Center (KSC) could seem hopeless.
However, when lives and millions of taxpayer dollars are on the line, NASA can't afford to just hope sensitive equipment is OK after a thunderstorm. Anything that may have been hit or damaged by a lightning strike must be checked, particularly around shuttle launch pads.
"The problem," Medelius explains, "is when something is broke you can find it. But when something is about to break is when you really need to. If you don't know where lightning struck you just cross your fingers."
Until recently, the only method available for determining strike location was accurate to within a quarter mile - and that can translate into a lot of mission-critical equipment at KSC needing to be replaced. Even equipment that has only a slight chance of having been damaged often needs to be replaced for safety's sake. This creates launch delays and can cost up to hundreds of thousands of dollars in equipment replaced for safety's sake.
"They had to do a visual inspection to see if something had melted," said Medelius. So a team headed by Medelius was put together to figure out how to more accurately track lightning strikes. Their invention, which NASA has now patented for sale to the public, was christened the Sonic Lightning Locator (SOLLO).
Counting the seconds
Covering an area of up to one mile, SOLLO can detect the location of a lightning strike to within 15 feet (5 meters). And while the existing system covers a lot more ground, 30 square miles, SOLLO's superior resolution means units can be deployed around individual groups of buildings and other installations.
The way SOLLO works seems pretty straightforward, but it took the speed of modern computers to make it work. When a lightning bolt strikes within SOLLO's range, an electrical sensor registers the event and its precise time - and where there's lightning there's also thunder -- a sound that's hard to miss.
Since sound travels several orders of magnitude slower than the electrical impulse from the bolt to the computer, SOLLO's ring of microphones pick it up at different times. With the computer registering differences of tiny fractions of a second between microphones, the approximate distance from each to the point of impact can be calculated. SOLLO counts the moments after the visible flash and when the thunder arrives. Only SOLLO does it much, much faster than a human could. SOLLO also has to take more into account.
Unlike the speed of electricity, the speed of sound is hardly constant. "You have know what the speed of propagation is of that area," explains Medelius, "Temperature and humidity ... it can change fast during a storm."
These vagaries of the atmosphere can alter the speed of sound enough to give wildly different results. SOLLO must take all these elements into account to constantly calculate how fast the sound of thunder should travel through the air.
Hit me with your best shot
SOLLO is in its final rounds of formal testing before being deployed at KSC. Of course, testing a lightning detector means you need the cooperation of a thunder storm.
Lacking a hotline to some kind of celestial weather control, the SOLLO team has had to take a page from Dr. Frankenstein to give their creation life. When bad weather rolls in (which happens all too often on Florida's Space Coast) Medelius and his team try to tempt the fates into tossing a thunder bolt at a predetermined spot.
Their bait: a small rocket trailing a long copper-Kevlar wire. Fired up into a passing thundercloud, the wire eases lightning's pathway through the air, hopefully sparking a full-blown bolt that's point of impact with the ground is already known. Comparing the strike's actual target with the location registered by SOLLO's sensors allows the team to refine their technique, one bolt at a time.
But of course, as in any news story about someone who studies lightning, Medelius found out for himself that the elements can sometimes seem too cooperative. Shortly after completing the first SOLLO prototype, Medelius piled the equipment in his car for transport, but decided to stop off for dinner at home first. Seeing that a storm was rolling in, Medelius decided to set up the equipment in the yard before sitting down to eat. As luck would have it, irony chose that evening to pay Medelius a visit.
"I was having dinner and I heard thunder. So I ran to my driveway," remembers Medelius. With perhaps too much zeal to test the new device, Medelius pondered dashing through the rain to the control unit. "I was thinking 'should I go and adjust the gain or not?'" he recalls. "And just then lightning struck the box, like, 33 feet away from me."
That's one lightning bolt whose location Medelius will never forget.
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