How does the U.S. Navy test the electromagnetic aircraft launch system on the USS John F. Kennedy?
That's right, by launching "car-like structures of graduated weights up to 80,000 pounds" off the deck.
The only way this could be more entertaining is if real cars were used.
That's pretty great!
Since we're talking aircraft carriers, there's a great article on one of the enginerds related to arrestor hook design that was on Hacker News yesterday: Testing of the F-35C Tailhook
I haven't done one since early 90s, but I've helped launch a 6000 lb steel plate box full I've concrete a loooonngg way into out into the James river.
It made really cool (and tall) splashes
Fun times.
Stupid question, but do they go in after them later on or are these single-use things?
Actually, good question! I was thinking it as I was writing, and couldn't quite remember. I'm 90% sure they retrieved them. Don't remember how!
95 % of my time there was sub construction, so, only helped with the steam catapult those few days.
At a guess, coiled up rope with a balloon on it.
James is about 7 miles wide there, but other than the channel itself, you can almost walk out to the channel at low tide! (I. E. , not too deep. )
They look like an expensive build. 7800lbs. of anything, but with dial in resistance at the axles, I would assume there are divers on one of those tugs to apply a hook.
We used to fire cannon out into Chesapeake Bay, God help the poor fisherman in a row boat that didn't get the message that morning!!!
You'd need 10,000 gallons of water to hit 80,000 pounds, so I am guessing that the sleds were filled with different volumes of water to hit their target weights and then drained to make them lighter for retrieval.
It does not look large enough in this video, so the water theory seems to be out.
Top video, go to 1:06. Is the Tech dialing in a bit of brake?
I didn't watch the video, but it's less about testing the catapult and more about calibrating it for aircraft launches.
The Navy needs to know how much power the catapult needs to accelerate any given weight to any given speed. A P3 is not going to launch at the same power or speed as a F18. Not to mention an F18 can vary greatly in take-off weight depending on what it's carrying. The pilot and flight crew work up the take-off weight of their aircraft before launch. That weight is given to the catapult crew. They verify the weight and set the catapult. Without all that testing they wouldn't know what power lever to set the catapult to. With too much power they rip the nose gear off the plane, too little and the plane doesn't have enough speed to fly and hits the water in front of the boat.
In reply to pinchvalve (Forum Supporter) :
Water is no where near heavy enough for the tests I knew of. But I also don't know of any 80,000 pound test sleds, so could be. But the size we launched were 4' x 8' x 2' of concrete and steel, at around 8,000. Divers were definitely around during tests. That had to be fun for them, with visibility probably being 1/2" or so!
Finally got a chance to watch the video.
7800 looks to be stenciled on the one.
I do believe 80,000 is a typo.
it mentions they adjust weight, by using different sleds (each of different weight)
BTW, I don't remember Doug, but seem to remember the name, so probably ran into him back when he started as a helper apprentice. 
80,000 lbs seems a bit extreme, but maybe not. It seems like the heaviest they would launch would be is a C3 Greyhound (shown below), and they max out at 60,000 lbs. The F35C believe it or not is showing a max takeoff weight of 70,000 lbs!! (not sure it could take off from a carrier like that though).
7800lbs seem way to light (maybe just working there way up) since even an A4 Skyhawk (likely the lightest plane catapulted in the last 50 years, well out of service now) is going to be at least 15,000 lbs. Even an F-18 (non-super hornet) will push 30,000lbs (supers around 10,000 more).
Colin Wood said:The only way this could be more entertaining is if real cars were used.
I have a Hot Rod magazine from the early 1960s that had a letter to the editor from a sailor on a carrier, he included a photo of them launching a 1950-ish Plymouth coupe off the catapault.
I don't remember the number from back then; heck I'm sure it was a classified number, and my former clearance wouldn't let me say it, even now that it's public. (People here put me down one time when I said the federal government knows more about me than my family, but they were only normal military.)
But the joke was always throwing a VW (bug) across the river. That's a REALLY long way from 80,000. The sleds in the video wouldn't weigh that is the wildest tall tail, the video didn't mention that much, so... it's either a typo, or made up for sensationalisim.
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