Super cavitating torpedo.
I’m going to stick with my airliner scenario because I think it is lowest cost, lowest risk and will get the job done, with a little tweaking. On reflection, having a high-jacked plane dive bomb into a carrier from normal flight altitude will give the carrier group enough time to scramble and vaporize the aircraft before impact (especially if they got word from traffic control that it’s a high-jacked plane headed their way). And, while a quick impact from a taking-off or landing plane may work, the idea of attacking the carrier in blue water is more fun and challenging.
5 years is enough time to train and place a few operatives in key airliner positions (e.g. chief mechanic, hanger security, etc.) at a well-located commercial airport hub. 5 years is also enough time to develop a state-of-the-art preprogrammed automatic pilot system (APS) that can be installed stealthily into an airliner before it takes off on a flight plan taking it near the carrier group. This rogue APS will not take the place of the plane’s installed auto-pilot (that would no doubt be easily detected by the pilots or traffic control). It will work in tandem with the plane’s APS and will only kick in a set number of miles before nearing the carrier group. The rogue APS will, at first, act only as a critical fault device (creating normal catastrophic failures causing the plane to lose altitude and putting it at risk of crash). The pilot will call mayday and plans will be made with traffic control for a water crash landing.
I’m confident traffic control would quickly learn of the proximity of the carrier group and contact the Pentagon to say, “don’t shoot down that plane!” (If the public learned that the navy shot down a crashing airliner, mayday voice box conversation and all, there would be hell to pay). And very probably they would ask for the carrier group to head toward the plane for the pending rescue operation. They’d also tell the airline pilot to head toward the carrier group as best he can (not unlike a Trojan Horse scenario).
As the airliner gets close to the carrier, at low altitude, that’s when the second phase of the rogue APS kicks in. It was preprogrammed with the carrier bridge/control tower as it’s visual target and it locks on. At the last couple of seconds, the plane banks hard toward the target and impacts before any counter measures can transpire.
The only problem with this plan is that innocent American passengers must be sacrificed. So, I suggest we install the device in an Air France plane!
*I’m just kidding, some of my favorite pastry chefs are French.
That actually is how WWII torpedoes were supposed to work. The first of many problems identified in the Mark 14 torpedo was that the magnetic exploder which was supposed to detonate the warhead when the torpedo was directly below the hull of the ship was hypersensitive and causing premature explosions. Worse, since an explosion was seen and heard many of these premature detonations were mistakenly taken to be successful hits. Once the magnetic exploder was disabled and the back up contact detonator relied upon, it was first discovered that the Mark 14 routinely ran ~20 feet deeper than it was set for, so runs that should have resulted in hits only resulted in torpedoes passing harmlessly beneath the target ship. Once that was fixed it was discovered that it had been concealing the fact that the contact detonator would crush on impact without detonating the warhead.
You’d need a nuclear boat for step 2 though; the Type 65 is launched from a 650mm torpedo tube which the Soviets only ever fitted on nuclear powered boats starting from the aforementioned Victor III class.
Uh, I know that. However, for this discussion, it’s not relevant 
(former STS here)
Everyone’s getting all Tom Clancy/MacGyver here, but given the five-year time frame, a much simpler solution would be to plant an operative on the carrier. I think it’s a certainty that Russia, and maybe other nations, have moles in the US military; after all, if the Taliban, Al-Qaida, etc. could do it, so could a sovereign nation.
Once assigned to carrier duty, the simplest target for sabotage would be the fuel supplies and distribution systems. Drop a lighted match into a tank filled with 100,000 gallons of jet fuel and let the fun begin. Even if the ship withstood the damage quite well, the destruction of its aviation fuel systems would turn it into nothing more than a rather well-armed cruise ship, and not much of a threat to anybody.
You don’t know what happens when you drop a match into a tank filled with jet fuel, do you? The match gets extinguished. The fuel will not ignite.
Maybe get your operative to be a pilot. Wait for a live-fire drill, take off, turn around and shoot. You could add a kamikaze thingy just to make it sweeter.
Kerosene burns without a wick, doesn’t it?
How about sugar in the fuel tank, or a big banana in the exhaust pipe? 
Can non-nuclear torpedoes be powerful enough to make a big air bubble underneath a ship?
What are the countermeasures against torpedoes?
Using a torpedo to make a large air bubble underneath a carrier could use the carrier’s weight against it. breaking it apart like some mines do.
Primarily, decoys. Or putting lower value units in the way.
I’m not sure what this has to do with anything… but Mythbusters long ago tested the scene in Die Hard 2 where Bruce Willis blows up a plane by igniting jet fuel with a Zippo. It’s just impossible. Heck, throw a match into a bucket of gasoline and you have a damn good chance nothing will happen.
Given the quality of some of the responses in this thread, I’m waiting for someone to say that they intend to wrap a chain around the carrier’s propeller, hook the other end around a telephone pole, and wait for the carrier to be rushed out of port, at which point the screw and the shaft will be left dangling on the dock.
The US Navy is also working on the Surface Ship Torpedo Defense system, which basically involves an anti-torpedo torpedo. No word on whether China is working on an anti-anti-torpedo torpedo torpedo.
I think putting the carrier on a treadmill would be more effective.
L-17
:o
Sharks. With frikkin’ lasers attached to their heads.
Thanks ExTank I was thinking it and wish I’d said it!
Brilliant stuff.
Peter
You know, no exotic tech is needed.
Naval Mines are deadly to warships, & Iran knows this, & often threatens to mine the Persian Gulf.
The problem with naval mines is that the carrier has hundreds of miles of effective combat range. So it’s probably going to be positioned in some semi-random location far off the coasts. That’s too much area to effectively mine it.
Some people are irony-proof. Obviously, the sabotage method would have to be a wee bit more sophisticated than that. But not much more. A single person with even basic knowledge of the fuel storage and distribution systems could place an explosive/thermal device wherever it would do the most good. I was referring to the threat of sabotage itself, and was being mildly facetious when I used the match-into-the-tank metaphor (because that’s what it was). But there are always the literal-minded to deal with 