Each EMALS flywheel unit stores 121 MJ.[1] This is roughly the energy in a gallon of gasoline.
Here's a big ultracapacitor bank, from Maxwell. This one is intended for temporary energy storage for buses, trucks, and trains, so it can take some banging around.[2] Capacity is 144 Watt-hours, or about half a megajoule. Weighs 64Kg, not including fans. So it would take about 250 of those units to equal one flywheel unit, for a weight of 16 metric tons.
The flywheel unit weighs about 11 metric tons. So using ultracapacitors increases weight, but it's not out of the question. Might be simpler. If the system were being designed today, it might well be capacitor-powered. No moving parts, unit-replaceable if damaged, and low-maintenance.
The EMALS system doesn't actually need 121MJ to launch.[3] Each launch uses maybe a quarter of that. Apparently the idea is to have enough energy stored for several launches on several catapults.
(A Marx generator is a setup for getting a high voltage at low current, by charging capacitors in parallel and then switching them to series. They're useful for powering some physics experiments and for making big sparks. The Museum of Science and Industry in Chicago used to have a big one, their old "Million Volt Lightning Generator". Not useful in this application.)
Here's a big ultracapacitor bank, from Maxwell. This one is intended for temporary energy storage for buses, trucks, and trains, so it can take some banging around.[2] Capacity is 144 Watt-hours, or about half a megajoule. Weighs 64Kg, not including fans. So it would take about 250 of those units to equal one flywheel unit, for a weight of 16 metric tons.
The flywheel unit weighs about 11 metric tons. So using ultracapacitors increases weight, but it's not out of the question. Might be simpler. If the system were being designed today, it might well be capacitor-powered. No moving parts, unit-replaceable if damaged, and low-maintenance.
The EMALS system doesn't actually need 121MJ to launch.[3] Each launch uses maybe a quarter of that. Apparently the idea is to have enough energy stored for several launches on several catapults.
(A Marx generator is a setup for getting a high voltage at low current, by charging capacitors in parallel and then switching them to series. They're useful for powering some physics experiments and for making big sparks. The Museum of Science and Industry in Chicago used to have a big one, their old "Million Volt Lightning Generator". Not useful in this application.)
[1] http://www.globalsecurity.org/military/systems/ship/systems/... [2] http://www.maxwell.com/images/documents/125vmodule_ds_101469... [3] http://vtb.ee.sc.edu/vtbwebsite/downloads/publications/emals...