Episode 69: 22,000 foot fall, Lights On or Off
- An explosion can save you from a 22,000 ft fall: busted
- It's better to leave light bulbs on: busted
The 22,000 Foot Fall myth was in many was a revisit of the Cement Mix Up myth, i.e. setting off a really big explosion in a Calaveras County quarry for kicks, though they were actually testing a myth this time around. This explosion had better footage than the cement truck as you could see the shockwave more clearly, and there is even a fire-fighting copter swooping in afterwards to put out fire on the surrounding hillside. As this myth did have a true story at its core, there was some hint of belief from Adam that this might actually work... until they were reminded what a 1,000 lb bomb looks like.
I was interested in the lights on or off myth as I had been told that its generally best if you leave fluorescent lights on all the time. I believe I had been told something like, "unless you leave the fluorescent lights off for more than an hour, you shouldn't turn them off." As it turns out, the actual rule for fluorescent lights is about 23 seconds. For other lights, about a second or less.
22,000 Foot Fall
"Biggest Explosion in MythBusters History"
Myth: a World War II gunner feel 22,000 feet from a bomber gun turret onto a train station. At the moment he was falling onto the train station, a 1,000 bomb exploded in the station, cushioning his fall and allowing him to survive. (source: factoid listed on a calendar)
- Cement Mix Up for another big explosion experiment at the same site
- Escape Slide Parachute for more falling from plane myths.
Adam and Jamie spoke to Joe Pruzzo of Castle Air Museum for background on WWII bombers. Pruzzo talked about one anecdote he had heard where a gunner fell 20,000 ft into a snowbank and survived with a broken leg. He also showed them a gun turret on a WWII bomber, which was so tiny that the gunners couldn't wear parachutes.
The MythBusters researchers were able to confirm that an airman did survive a 22,000 ft fall, but the question was whether or not the explosion was an element of the story.
15 lb. ball and air bag explosion test
Tory and Kari were tasked with creating a small-scale replica of this myth to test its feasibility. They dropped a 15 lb. ball onto a model glass-roofed house with a car airbag charge inside (no airbag, just the pyrotechnic charge). The shockwatches registered between 75g-100g for the ball falling by itself. After some trial and error, they got the charge to go off just as the ball was about to hit the roof. Side-by-side views of the ball falling with and without the explosion showed no real difference between the two; i.e. the explosion did not cushion the fall.
- Train station: Adam designed a 10'x20' mock train station out of welded steel and 2'x2' panes of glass. Jamie: "It's pretty, but it's going to go away pretty soon"
- 1,000 lb bomb: a 1,000 lb GP bomb contains about 500 lbs of high explosives, with the rest of the weight being the bomb casing. The decided to give the steel tubing from the Sharammer one final hurrah (see XMB fuselage for Exploding Hair Cream, barrel for the Archimedes Steam Cannon, and Jaws Special). They used a bunch of Dyno Trojan Spartan explosives to generate the 500 lbs of explosive force.
- Airman: they ruled out using Buster for the drop and instead used Ted (as in Busted), which was a dummy made out of ballistics gel.
- 22,000 drop: The MythBusters knew human terminal velocity is 120 mph, so they decided to use balloons to lift their airman to an appropriate height for terminal velocity: 487 ft (5.5 seconds). They also planned on using a guide wire to direct airman's fall directly into the mock train station. (NOTE: In Escape Slide Parachute, they calculated with a 14 second fall and 2000 ft drop height)
They setup at a quarry in Calaveras County. They were beset with difficulties at the blast site, from balloons popping to weather so hot that it was melting Ted and causing the fire marshals to cancel the explosion for the day.
The explosion itself was beautiful. The high-speed footage showed the shockwave radiating outward with a mushroom cloud forming upwards. The surrounding ground was set on fire and a fire-fighting copter swooped in to put it out. Steel shrapnel from the train station was also sent everywhere -- a piece of steel shrapnel even wrapped itself around a small tree, breaking the trunk. The shrapnel around the tree was evidence to Jamie that the myth was completely implausible: the airman would have been riddled by shrapnel as well.
As for Ted: that part of the experiment was a complete failure. Ted's guide wire failed and he fell far from the site, but still among the steel shrapnel.
busted: although they believe the story about an airman surviving a 22,000 foot fall to be true, the amount of explosive damage they witnessed led them to believe that there was no way that a explosive shockwave could cushion a fall.
Lights On or Off
Myth: You save on energy bills by leaving lights on. Some people believe that the energy to turn on lights exceeds savings of turning lights off.
They talked to Mark Reisfelt, manager of the Independent Electric Supply where they purchased their light bulbs. He felt that it was best to turn the lights off.
To test the myth, they needed to measure energy usage during startup, maintenance (steady state), and shutdown.
For steady state energy consumption, they turned on several different types of bulbs for 60 minutes and measured their consumption using a Kill A Watt: * Incandescent 90 Wh * Compact Fluorescent (CFL): 10 Wh * Halogen: 70 Wh * Metal halide 60 Wh * LED: 1 Wh * Fluorescent: 10 Wh
For startup energy consumption, Grant hooked up an inductive current loop to a computer and measured the amount of energy used when the turned on the bulbs. With an inductive current loop, you run a wire through the center, which induces a current in the loop. This current is then measured by a digital sampling oscilloscope.
Based on the amount of energy consumed turning on the bulb, they were able calculated how long the bulb would have to be turned off in order to make it worth the energy savings, i.e. "It's best to turn off the bulb if you are leaving the room for":
- Incandescent: 0.36 seconds
- CFL: 0.015 seconds
- Halogen: .51 seconds
- LED: 1.28 seconds
- Fluorescent: 23.3 seconds
In other words, its almost always best to turn the bulb off. Even the 23 seconds for the fluorescent lights isn't very long, and the rest of the times are pretty much blinks of an eye.
They tested one final element of this myth: frequently turning lights on and off decreases their life span, thus leading to greater costs. Grant setup a timer and relay to turn the bulbs on and off repeatedly every 2 minutes. After six weeks, only the LED bulb was still working. Based on this test, they extrapolated that it would take five years of ordinary usage to cause the bulbs to burn out.
* busted *
Side-note: 105-year bulb
Grant and Kari visited the Livermore/Pleasanton Fire Department to view their light bulb that has been burning for 105 years. It has a carbon filament that is much thicker than modern bulbs and also burns much cooler/darker. You can check on the light using the bulb's webcam.