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Launching with isolated thunderstorms predicted

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sam_midkiff

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I am hoping to have a launch tomorrow afternoon/early evening with some scouts working on the Space Exploration merit badge, and the forecast calls for isolated thunderstorms with a 30% chance of precipitation. In Indiana, 30% chance of precipitation means that likely there will be no rain. My worry, however, is precipitating a lightning strike by firing a rocket into a cloud and having the exhaust provide a path for the lightning to follow. Is this a reasonable worry? FWIW, the rockets will be Alphas on A and B engines.

If we are seeing lightning before launching, I plan to just try again another day, so I am worried about the case where there is no visible electrical activity.

Thanks,

Sam
 

RocketsNorth

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Sam I would say err on the side of caution and don't launch period.
In my part of the continent we had a mother and 2 small boys nearly killed couple of weeks ago when lighting struck near them. The day was overcast but there was no storm activity in the area....
Here's the link http://thestar.com/article/680181
Fate was on their side and they all recovered. :2:
 

Zeus-cat

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I would seriously doubt that rocket exhaust is conductive, so the likelyhood of lightning hitting a rocket and coming down the exhaust trail is nearly nil. However, you should not be standing around in a field where you are the tallest thing around if there is lightning activity nearby.

You would be OK to launch if one of the scouts is freakishly tall and you are rather short. Just kidding - stay inside during storms.

By the way, it is rather complicated, but lightning doesn't just come down from the clouds; it also goes up from the ground. You shouldn't be outside messing with steel launch rods and launch controller wiring during electrical storms.
 

dedleytedley

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I recall seeing a video feature about an institute located in Florida devoted to the study of lightning. They used rockets equipped with spools of fine stainless wire to induce lightning strikes when fired into thunderheads. It was explained that the wire only induced the electrical flow and most of the charge was carried by the air. Lightning is tricky stuff and often takes EVERY path possible.
When I was a child our 60 foot tv antenna was hit by lightning. Most of the charge must have gone straight into the ground but lightning jumped from the tower attached to our house to the steel beam supporting the brick over my window, blasted the plaster off the inside of the wall at the ends of the beam, and traveled across the room to hit the brass frame of my globe. The bolt fried our tv as well on the main floor.
When I was working with seismic charges any sight of lightning or sound of thunder required us to stop working and put all caps or sticks into the magazine. Sometimes lightning will travel for miles from a cloud giving us the phrase "a bolt from the blue".
Has anyone heard of a hobby rocket/lightning incident? Ted
 

Micromeister

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First:
WE are NEVER to launch a model rocket into clouds Period. It voilates the safety code.

As the group leader it's your responsiblily to know the expected altitude of the models your scouts will be flying and more important the cloud deck ceiling in the area your flying. That info is all to easy to obtain from the internet weather and avaition weather sites.

Also good to remember; If you can HEAR thunder you CAN be hit by lighting. In our neck of the woods we recently had a young man killed by a lighting strike from a far off distant approaching storm. Another boy standing close was also injured but thankfully survived.

That said as an Old Scoutmaster and Eagle; the Scout motto is Be Prepared. If storms and low clouds are likely, Safety says don't do it, postpone for a better flying day.... Space Exploration MB flights can wait another week.
 
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RangerStl

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After a Lightning bolt travels through 5 miles of air, the only better insulator being a vacuum, whether or not your rocket exhaust is conductive is not an issue.

If there are thunderstorms "Predicted" but you do not see any signs of weather, then there's no reason you can't go launch. However, if you see that weather is rolling in, see lightning, or hear thunder, pack up and find cover.

You take a terrible gamble when you stand in a field during stormy weather whether golfing, horseback riding, or rocket launching. If the weather looks questionable, don't. Lightning can occur and has killed people up to 15 or more miles away from the actual convective cell.
 

jadebox

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If there are thunderstorms "Predicted" but you do not see any signs of weather, then there's no reason you can't go launch. However, if you see that weather is rolling in, see lightning, or hear thunder, pack up and find cover.
Here in Central Florida, we have thunderstorms predicted for just about every afternoon especially during Summer. Generally, they don't roll in until the early afternoon, so they aren't too much of a problem. Once lightning is spotted on the horizon or we hear thunder, we start shutting down the launch.

There was one NEFAR launch, however, when we were overtaken by a quick moving storm. I can tell you that it's kind of scary standing near long metal launch rods and rails in the middle of an open field when a thunderstorm suddenly appears.

-- Roger
 

shreadvector

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Here in Central Florida, we have thunderstorms predicted for just about every afternoon especially during Summer. Generally, they don't roll in until the early afternoon, so they aren't too much of a problem. Once lightning is spotted on the horizon or we hear thunder, we start shutting down the launch.

There was one NEFAR launch, however, when we were overtaken by a quick moving storm. I can tell you that it's kind of scary standing near long metal launch rods and rails in the middle of an open field when a thunderstorm suddenly appears.

-- Roger

Have you felt the charge building? Now THAT is disturbing.
 

sam_midkiff

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First:
WE are NEVER to launch a model rocket into clouds Period. It voilates the safety code.

As the group leader it's your responsiblily to know the expected altitude of the models your scouts will be flying and more important the cloud deck ceiling in the area your flying. That info is all to easy to obtain from the internet weather and avaition weather sites.

Also good to remember; If you can HEAR thunder you CAN be hit by lighting. In our neck of the woods we recently had a young man killed by a lighting strike from a far off distant approaching storm. Another boy standing close was also injured but thankfully survived.

That said as an Old Scoutmaster and Eagle; the Scout motto is Be Prepared. If storms and low clouds are likely, Safety says don't do it, postpone for a better flying day.... Space Exploration MB flights can wait another week.
Thanks, and your warnings are appreciated. For the record, I was not going to launch into clouds, and was not going to launch if lightning or thunder was had been detected in the last 30 minutes. My fear was that providing a path of exhaust that effectively shortened the distance from a potential source of lightning (i.e. a cloud at 1500 feet when thunderstorms are possible) to the ground by 250 to 500 feet might prove fatal. Sorry if I wasn't clear on this.

Fortunately, the current forecast is more optimistic, so I'm hoping this question is, at least for tonight, theoretical.

Sam
 

sam_midkiff

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Thanks to everyone for their responses. My strategy will be to avoid launching into clouds (as always), and shut down if there are any signs of lightning.

Sam
 

AKPilot

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Sam, also be aware that lightning as struck ahead of storms, in some cases up to 30 miles out. Check the Weather maps and always err on the side of caution. You can always reschedule a launch - don't get into hurry-itis.
 

jadebox

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Have you felt the charge building? Now THAT is disturbing.
Yes, when I was in high school. Our marching band was practicing we felt that. Some kids had their hair start to stand on end. We took cover in a building very quickly! :)

-- Roger
 

sam_midkiff

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Sam, also be aware that lightning as struck ahead of storms, in some cases up to 30 miles out. Check the Weather maps and always err on the side of caution. You can always reschedule a launch - don't get into hurry-itis.
Good point. I did check the weather map before going out, and there was nothing for 100 miles. Indiana is not as bad as Florida, but we do get a lot of days with a 30% chance of rain and/or thunderstorms where everything just dissipates and nothing happens. But with lightning, you do need to make sure nothing really is happening.

Sam
 

luke strawwalker

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I would seriously doubt that rocket exhaust is conductive, so the likelyhood of lightning hitting a rocket and coming down the exhaust trail is nearly nil. However, you should not be standing around in a field where you are the tallest thing around if there is lightning activity nearby.

You would be OK to launch if one of the scouts is freakishly tall and you are rather short. Just kidding - stay inside during storms.

By the way, it is rather complicated, but lightning doesn't just come down from the clouds; it also goes up from the ground. You shouldn't be outside messing with steel launch rods and launch controller wiring during electrical storms.
Well... yes and no...

As a farmer I've worked a LOT out in the fields with approaching thunderstorms and nearly got struck by lightning twice within two weeks a few years back, and got a good "sympathetic shock" (induced by nearby lightning strikes) to prove my stupidity for doing so.

I tend to think that a higher density of particulate matter dissolved in a gas (the exhaust trail of the rocket), while technically non-conductive, would allow easier passage of lightning to the ground than the surrounding "clean" atmosphere would, therefore allowing a 'path of least resistance' to the ground which a lightning bolt would be likely to follow in the event of an imminent discharge in the area. At the voltages lightning typically achieves, NOTHING is truly "non-conductive" as the lightning can EASILY overpower it's dielectric strength, and hot recently expelled reactive particles would allow current to jump from particle to particle down the exhaust trail a lot easier than the "clean" air surrounding the launch site would, but then again, there is a certain element of chance to it all.

I know one time I was in the field disking and raising a HUGE cloud of dust, which was being drawn STRAIGHT UPWARD into the inflow convection of an approaching building thunderstorm, and even though it wasn't raining I went ahead and quit when I started seeing lightning on the horizon because I figured that the particulate dust, possibly electrostatically charged from rubbing on the disk blades and the particles rubbing together, made a perfect "virtual ground wire" back to the large iron/steel tractor and disk I was operating, and would likely attract lightning. Had the dust been blowing across the field near ground level by storm outflow I wouldn't have worried about it much, but STRAIGHT UP was just asking for it IMHO.

I saw the same program about the lightning-attracting rockets unspooling fine wire (like TOW missiles) to lead lightning strikes back to the test articles on the ground. IIRC, that's the national lightning lab in Florida, where they test a lot of electrical utility equipment against lightning strikes, because it's one of the most heavily lightning-hit areas of the world. They use some sort of electrostatic potential meters to tell them when a lightning strike is building and launch a rocket shortly before they figure a strike is to occur-- a lot of the time the wire leads a lightning strike right back down to their test articles, but sometimes they miss or the lightning dissipates or strikes elsewhere or strikes before the rocket is launched, or something like that. It was a fascinating program... can't recall offhand where I saw it; PBS maybe??

Messing with steel launch rods and stuff with lightning nearby is probably NOT a good idea, because 1) lightning is attracted to conductive metallic objects and 2) lightning is more easily attracted to sharper conductive metallic objects like launch rods than rounded ones. Even lightning strikes nearby can induce a current in metallic objects and give you a firm shock-- I experienced that myself twice in a half-month. I was working on a cotton picker, with my arms through the framework, extracting a PTO drive gearbox from the side of the transmission, when lightning struck just up the road. The magnetic field or residual electrostatic charge in the atmosphere induced a strong jolt in the metallic frame and basket of the cotton picker and zapped the heck out of me! A week or two later I was tarping down a load of recently dumped cotton in a trailer during a pouring rainstorm after pulling out of the field, getting ready to head to the cotton gin. I had climbed in the trailer and spread the tarp and shoved it down the sides between the cotton and 2x4 wire sides, and climbed out, and noticed the storm winds had torn one corner loose, so I ran to the back and reached through the wire sides to grab the tarp and pull it down, when a lightning strike up the road energized the steel trailer and it's 20 foot long 9 foot high sides, zapping me through the wire.

I've also heard lots of stories of cattle, horses, and other livestock being killed from lightning striking the fence a mile or more away, and the current jumping to them at the other end of the fence. Not good!

Can't be too careful about that sort of thing... :)

I'd say go ahead and launch, but if there's anything coming up 'in the area' just call it a day and head home... especially when you're talking about a group of kids... not worth the risk...

Later! OL JR :)
 
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cobra1336

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As a child my wife was swinging from a screen door on the front of her house. She was struck by lightning. She wasn't harmed but to this day I kid her that I always knew there was something wrong with her.:D
 

Zeus-cat

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I did some more reading on lightning. Objects on the ground become positively charged before a lightning strike. Usually, the tallest objects send positive leaders up towards the negative charge in the cloud. Some of these positive leaders attract the negative charge and others don't.

I am guessing that people who feel a charge are feeling a positive leader that does not connect to the negative leader.
 

shreadvector

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I did some more reading on lightning. Objects on the ground become positively charged before a lightning strike. Usually, the tallest objects send positive leaders up towards the negative charge in the cloud. Some of these positive leaders attract the negative charge and others don't.

I am guessing that people who feel a charge are feeling a positive leader that does not connect to the negative leader.
Correct. Feeling a charge build up is WAYYYY different from "feeling the current flow" (and if you feel the direct lightning current flow you are already dead).
 

JStarStar

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Most high school athletic associations, which have a lot of experience with outdoor events, now have rules mandating that outdoor competitions must be suspended immediately if there is any visible lightning or audible thunder. Michigan's rule is pretty typical:

http://www.mhsaa.com/Officials/ResourcesPolicies/GameSuspensionPolicies.aspx

B. When lightning is observed or thunder is heard and the contest is suspended, contestants shall not return to the playing field until lightning has been absent from the local sky and thunder has not been heard for 30 minutes.
Since rocketry activities involve a lot of standing around in open fields in close proximity to metal rods and other electric equipment, if I were serving as RSO and there was any sign whatsoever of lightning in the distance, I'd issue an immediate bust-down order: pack up the pads and get in the cars.

If there's actual thunderstorm activity on the way, anybody with a pop-up canopy will probably want to think seriously about folding up, too.

Obviously if you have more than scattered distant rumbling of thunder -- if you have actual lightning in the area -- you forget about busting down, get under cover, wait it out and come back for your stuff later. A launch pad or canopy getting messed up in a storm is an annoyance, getting hit by lightning is fatal.

When the storm is over, if you have at least 30 minutes of absolute all-clear -- not even a rumble -- you can start setting up the pads again. If all other conditions (rain, wind) are OK as well.

Needless to say, any time I launch, one of the last things I do before heading out the door is check out weather.com or wundeground.com to check out the winds and the radar screens.
 
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