Slashdot Mirror
Watch the US Navy Test Its Electromagnetic Jet Fighter Catapult
An anonymous reader sends word via Engadget that the U.S. Navy has tested its Electromagnetic Aircraft Launch System for the first time with a "dead-load" (a wheeled steel sled that weighs as much as a jet) aboard the Gerald R. Ford carrier. The article goes on to say: "Its advantages over traditional catapults that use steam instead of electromagnetic energy include smoother acceleration and its ability to place less stress on the aircraft — plus, it was designed to work even with more advanced carriers that the military will surely use in the future." You can watch a video of the "dead-load" testing here.
Steam seems like an ideal solution to me. Steam expands so well the dynamic range of it's force curve seems apropos to the task. How much of the EM energy goes into force? surge currents and magneto striction are usually things people find shorten the lifetime of electo devices yet here they are at the extreme in these. Presumably there's no shortage of steam available and it's a great way to store energy.
Some drink at the fountain of knowledge. Others just gargle.
http://en.wikipedia.org/wiki/E...
Advantages
Compared to steam catapults, EMALS weighs less, occupies less space, requires less maintenance and manpower, is more reliable, recharges more quickly, and uses less energy. Steam catapults, which use about 1350 pounds of steam per launch, have extensive mechanical, pneumatic, and hydraulic subsystems.[4] EMALS uses no steam, which makes it suitable for the Navy's planned all-electric ships.[14] The EMALS could be more easily incorporated into a ramp.[4]
Compared to steam catapults, EMALS can control the launch performance with greater precision, allowing it to launch more kinds of aircraft, from heavy fighter jets to light unmanned aircraft.[14] EMALS can also deliver 29 percent more energy than steam's approximately 95 megajoules, increasing the output to 122 megajoules.[4] The EMALS will also be more efficient than the 5-percent efficiency of steam catapults.[2]
Mit der Dummheit kämpfen Götter selbst vergebens
WHOOSH!
And it's on topic.
One of the reasons for this is to allow it to adjust the force used to lighter weight drones. Also, it is a lot less complex then the steam driven system, so easier to maintain.
They totally missed that white boat! Looks like about 30 degrees to starboard and they'd have nailed it. Bad aiming there.
Think "really long run", rather than hard acceleration. As in, a ramp from the bottom of Kilimanjaro to the top. Even IF that long a run can't accelerate the ship to orbital velocity, it won't take very much of a burn to finish the job, will it? Of course, for unmanned launches, they can ram the craft into orbit at any launch speed desired.
"Windows is like the faint smell of piss in a subway: it's there, and there's nothing you can do about it." - Charlie Br
Getting and keeping enough pure water on board ship is NOT easy! If the water is NOT pure; you get more rust. The coolant on the nuke power plant is NOT likely to be water and it is likely to be radioactive. Steam leaks are more likely to cause major injuries than blown electric breakers on a ship. Tim S.
Sorry but you didn't do much research before posting.
The carriers are all nuclear which means they boil sea water to turn steam turbines.
Boiling seawater would produce a lot of salt which would clog the boilers.
The EM system means you have high voltage lines running under the decks and I generally think the system is going to be more complicated and harder to repair/maintain than the steam version.
The high voltage lines take up a lot less space than all the pipes an insulation needed for steam. Pipes corrode and need to be replaced and are susceptible to vibration damage. Maintenance on a wire is much less than on a pipe.
Smoother acceleration? That also makes no sense.
Pistons provide maximum acceleration at the beginning of the stroke and less at the end. That is exactly the opposite of what is good for an aircraft. It is difficult to modify where in the stroke to apply thrust for different aircraft types.
We were hearing about them testing robots to go into a nuclear reactor in Japan.
So what? The catapult will not operate in a high radiation environment.
A steam piston is more reliable than some electro magnetic whatever.
There are a lot more to a steam powered catapult than a simple piston. If any of the valves jam the catapult is down.
Saying that you can't do this with finesse ignores that the most advanced robots these days actually make use of pneumatic actuators.
Which are limited in size and power by the difficulty in moving fluids. Sorry buy advanced robots do not accelerate aircraft weighing tons to flight velocity.
That old news was overcome by events over half a year ago. Prince of Wales is not going to be mothballed at infancy after all. 2014 September 5: "The Royal Navy's second new aircraft carrier, the Prince of Wales, is to be brought into service rather than sold off or mothballed, Prime Minister David Cameron has announced. ... Both carriers will not be fully operational until 2023, the Ministry of Defence said."
Jeeze, struggling to no more than the third and fourth sentences of Wikipedia would have told you that.
The Queen Elizabeth class aircraft carrier program has been beset with enough heavy weather without having to cite obsolete information.
The carriers are all nuclear which means they boil sea water to turn steam turbines.
No. Only a very modest amount of seawater gets boiled in a distillation plant heated by the reactor; the resulting freshwater goes into the propulsion engines, which are closed Rankine cycles. Water goes round and round from boiler to turbines, to a seawater-cooled condenser that turns it back into liquid, to the boiler again. Lather, rinse, repeat. If you tried to use seawater in the propulsion plant, it would fill up with salt in a matter of hours. The distillation plant only supplies enough water to the engines to replenish what leaks out; the rest of its output goes to the catapult system.
The EM system means you have high voltage lines running under the decks
Ever been in the same space with a battle-damaged steam line?
such big industrial machines are hydraulic in most cases. They rely on pressure
Steam machines rely on pressure times volume, which is an order of magnitude increase in control problems.
Steam catapults are on the top of the ship, and the reactors are near the bottom. You need an extensive network of pipes to fill the reservoir tanks at each catapult. The steam needs to maintain temperature the entire way. There is a reason we run power lines across the country, and not steam lines.
I hope you never buy a diesel powered car.
I want to shoot the messenger!
It's called Pentagon Wars - one of my favorite movies, actually. It's one of those "it's funny because it's true" things.
The American Dream has too much grinding and the leveling makes no sense. -GameboyRMH (1153867)
That's all well and good but surely the power you speak of is allocated for propulsion?
Some numbers: the Nimitz-class carrier generates at least 190MW, a steam catapult on that carrier requires up to 72MJ of energy per launch (at maximum). So a Nimitz-class carrier could launch one airplane per second without using a great deal of its power. In practice, it's rare for a steam catapult to launch more than one aircraft per minute, which means that even with 4 steam catapults going at their maximum rate and hauling a maximum load, the average energy use would be about 18MW, or less than one tenth of the steam power available.
Hint for you: not all of the steam power is allocated for propulsion; much is for "other uses". The Nimitz-class carriers can use only up to 140MW for propulsion.
something like the QE has: two gas turbines, 4 diesel, and 4 induction motors to the screws. 77,000 tons to 25+kt.
Political debates have me rolling my eyes so much I think I got optical whiplash. I should sue. - Foamy The Squirrel
The last time they had a plan like that Argentina took advantage of it - however they acted on the announcement and not the actual sale (Invincible) or scrapping (Hermes, Ark Royal) of all the carriers and were caught out.