Friday is here, and the "A Taste of Science for the Weekend" column is back — number 86.
This week: the connection between flywheels, electromagnetism, and glycol in aircraft carriers.
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Aircraft carriers are the most massive and expensive vessels in the world.
The aircraft carrier *Ford*, which will arrive in our region this week (see video), cost approximately $13 billion — and the way it enables aircraft to take off and land is truly fascinating.
Despite its size, an aircraft carrier is remarkably short relative to what a plane needs to build up enough speed for takeoff, or to slow down enough for landing.
To solve this problem, the aircraft is attached to a carriage on a track that is fired forward at high speed to accelerate the plane for launch, while a cable stretched across the deck allows a hook on the plane's tail to catch it and brake during landing.
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In the older generation of aircraft carriers, the aircraft's acceleration was achieved by high-pressure steam released all at once. The sudden, aggressive acceleration caused high wear on the aircraft, and because it always fired at the same intensity, lighter aircraft experienced higher acceleration forces than heavier ones.
On the *Ford*, this mechanism has been replaced with a more sophisticated system.
Energy from the ship's nuclear reactors is used to store kinetic energy in heavy flywheels, which spin faster and faster, up to 6,400 RPM.
The deck track is based on electromagnetic propulsion whose intensity can be adjusted with precision.
At launch, the flywheels' rotational energy is converted all at once into an electrical current that travels along the track and drives the carriage forward, while a computer gradually increases the current's intensity rather than releasing it as a sudden burst.
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Catching a taut cable with a tailhook is far from sufficient on its own to stop a landing aircraft.
To enable rapid deceleration, the cable is connected to giant turbines that spin inside water-filled tanks, converting the energy into heat and waves.
The rapid heating of the water could produce steam and cause the tanks to rupture, so glycol is mixed in — adding viscosity and allowing higher temperatures to be reached without vaporization.
On the *Ford*, an advanced and interesting braking mechanism is used.
Inside the water tanks are motorized plates whose angle can be adjusted to regulate the resistance the water exerts. This allows the braking force to be matched to the weight of the landing aircraft.
At the same time, the pull of the arresting cable spins the shaft of an electrical generator that converts the energy into electricity; the electricity is then dissipated as heat and released into the atmosphere through a bank of capacitors.
Gradually varying the electrical motor's resistance throughout the landing makes the arrestment smoother and more adaptable.
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The surfaces of an aircraft carrier face exceptionally high abrasive forces.
Beyond the aircraft taking off and landing, the flight deck is exposed to the elements and to the scorching temperatures of jet blast from aircraft engines.
The epoxy coating used in the past would break down and crumble, posing a risk of debris being ingested into aircraft engines.
In the new generation, the coating has been replaced with an aluminum-ceramic composite: the aluminum absorbs heat and dissipates it rapidly, while the ceramic provides the hardness required to withstand the stresses of landings and takeoffs.
Let's hope this will be the last time we need the presence of such a war machine in our region.
Shabbat Shalom 😊
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