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According to Wikipedia USS Carl Vinson aircraft carrier range is unlimited distance.

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How can this be possible? It says it uses nuclear power/engines. How can this be safe for a military transportation? One hit and the carrier can blow up.

If the technology really is there and allows safe usage of the carrier why is this not used in another type of transportations?

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Grasper
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    It is. Nuclear submarines. As for why it's not widely used; Google the cost. – GeoffAtkins May 09 '17 at 19:19
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    Nuclear power plants do not equal nuclear explosive. Damage to the power plant is bad, but it generally proceeds losing the ship even on conventionally powered craft. – dmckee --- ex-moderator kitten May 09 '17 at 19:20
  • @dmckee so it is a floating nuclear power plant? Why is the navy crew not wearing a special protective outfit to prevent radiation? – Grasper May 09 '17 at 19:24
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    Most parts of a nuclear power plant are fine to walk around in shirtsleeves, and the plants on shipboard are designed with that in mind. For small reactors you can stand only a few meters from the core without overt danger. I've done that at a TRIGA facility. The engineering techs have access to protective kit if they need it, but they simply don't for most operations. – dmckee --- ex-moderator kitten May 09 '17 at 19:26
  • @dmckee, so why can't we use a similar system in cars, planes? – Grasper May 09 '17 at 19:33
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    Size, weight, expense, training requirements for operators, and the much more frequent incidence of damage to such conveyances. Take your pick. For that matter the US navy seems to be phasing out nuclear power for surface ships, though given the 50+ year design lifetimes of capital ships that's going to take a while. – dmckee --- ex-moderator kitten May 09 '17 at 19:35
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    The most important piece of protective gear is a rad detector for dose estimation. There are probably real nuclear weapons on board, and certainly enough conventional explosives and jet fuel to ruin your day. Nuclear cars and planes have been designed. –  May 09 '17 at 19:36
  • BTW-The US government *did* look into nuclear power for trains and planes in the 50s and 60s. Never went anywhere. – dmckee --- ex-moderator kitten May 09 '17 at 19:39
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    Your question seems more like "how can a nuclear-powered carrier be safe?" rather than "does it have an unlimited range". – Reinstate Monica -- notmaynard May 09 '17 at 21:37
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    Take note, that while it does say that it has an unlimited rage, it also states 20-25 years, meaning that the ship can run for 20 to 25 years without refueling, in that time it can reach any point on the globe, so it's not that the range is unlimited, it's that it is much larger than any possible travel distance on earth. – SIMEL May 10 '17 at 07:16
  • @GeoffAtkins: Also, [cruisers, destroyers, merchant ships, ice breakers](https://en.wikipedia.org/wiki/Nuclear_marine_propulsion). – DevSolar May 10 '17 at 10:00
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    Literally, no. Its fuel will exhaust itself eventually and then you'll need to refuel the reactor before the ship can move again. Practically, yes. The fuel is expected to last 25 years before it needs to be replaced, and that's a significant portion of the expected lifetime of a typical warship anyway. – GordonM May 10 '17 at 11:07

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tl;dr- Yes, this type of aircraft carrier can and does go for decades before refueling, able to circle the globe many times over that period. While not literally "unlimited", it's a decently close approximation for Wikipedia to show in a quick-facts table.

This aircraft carrier first refueled 25 years after being launched

According to the US Navy's website (via Archive.org) for Nimitz-class carriers:

Capability

  • Powered by two nuclear reactors that can operate for more than 20 years without refueling
  • Expected to operate as Navy warship for about 50 years

Apparently refueling is a pretty lengthy process. As the same US Navy site notes:

USS Nimitz (CVN 68) was the first to undergo its initial refueling during a 33-month Refueling Complex Overhaul at Newport News Shipbuilding in Newport News, Va., in 1998

Since the USS Nimitiz was first launched in 1972, that means that it went for about 26 years before refueling, and then the refueling process itself took 33 months.

Likewise, the USS Carl Vinson (asked about in this question) was launched in 1980, but didn't start to refuel until 2005.

Is that really "unlimited"?

Seems close enough to "unlimited", given that it could've circled the globe more than 300 times in that time if it maintained 30 knots as-the-crow-flies.

The 300-times figure appears to be generous, as there's significant reason to believe that the carrier can't actually sustain non-stop top-speed over this entire time period. A more informed ballpark figure might be on-the-order of 40-times-around-the-world-as-the-crow-flies.

Please note that these figures are meant to estimate scale in appreciable terms from the given figures, not to serve as an actual claim about real-life performance. More in the comments below.

[off-topic] Safety

This part of the question is off-topic for SE.Skeptics:

How can this be possible? It says it uses nuclear power/engines. How can this be safe for a military transportation? One hit and the carrier can blow up.

If the technology really is there and allows safe usage of the carrier why is this not used in another type of transportations?

However, for completeness's sake, it's worth mentioning that nuclear reactors don't blow up; they're not configured to cause that sort of violent chain reaction. Reactors just overheat (meltdown). Presumably the aircraft carriers have contingencies in place to handle meltdowns; the ocean provides tons of cooling water that might be used.

Wikipedia has more about emergency core cooling systems that can kick in if something causes the core to start overheating. But, a detailed discussion of such systems is outside the scope of SE.Skeptics.

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Nat
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  • I doubt the *USS Nimitz* could have maintained 30 knots for 26 years. A large amount of that time [it was in a state of "Selected Restricted Availability"](https://en.wikipedia.org/wiki/USS_Nimitz#Construction), in effect in dock for major repairs, overhauls or adaptation, and for much of the rest it would have been in dock while ready for sea – Henry May 10 '17 at 07:15
  • @Henry, the fact that it was in dock or on repairs doesn't mean that **if** the need arises it can't be used continuously for long period of times (although I doubt that they have rations and supplies for a decade long voyage at see on board). Even if you use your car only to drive to work and back, doesn't mean it can't farther destinations. – SIMEL May 10 '17 at 07:22
  • @Henry Added in a disclaimer that it's probably a generous estimate. – Nat May 10 '17 at 15:10
  • There's other consumables that may affect practical operating times. –  May 10 '17 at 17:42
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    To add some more context from a Navy nuke, the 'fuel level' of a nuclear reactor is measured in "Full Power Hours." A core has X full power hours before it needs to be refueled. The number of full power hours adds up to over a year, so if a carrier really were to steam at maximum speed, it wouldn't make it two years before its 'out of fuel'. However, a carrier is very rarely using over 50% power; mostly recovering an aircraft that lost an engine or (pretending to) dodge torpedoes. – kingledion May 11 '17 at 18:10
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    @fredsbend Regarding other consumables, the carrier can get everything it needs on the go, via at sea replenishment, or by flying in supplies (it is an _aircraft_ carrier). 6 months continuous operation at sea would not be much of a stretch for a carrier battle group. – kingledion May 11 '17 at 18:12
  • @kingledion Thanks for the info! So, hypothetically, say that a carrier were just trying to go as far as it can on its own fuel, choosing whatever cruise speed is most efficient for it under normal conditions. Would you know how we could get an improved estimate of how far it could go in that sort of situation? – Nat May 11 '17 at 23:20
  • "*effectively* unlimited" would be more accurate, if we wanted to nitpick. – Shadur May 12 '17 at 05:34
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    @Nat Optimal 'miles per g of uranium' would be in the 18-22 knot range. Since I'm not longer in the Navy, and the info is classified anyways, I can't be sure, but I'd estimate from memory you could do about a million miles at optimal cruising speed on one core. – kingledion May 12 '17 at 11:59
  • @kingledion Awesome, thanks! And definitely please feel free to decline if you're not comfortable answering anything, but if we'd say a million-miles-ish one one core, and Wikipedia says that it's got two cores, then would 2-million-miles-ish seem ballpark? That'd put it around 80 circles around the Earth (as the crow flies), which'd be around 25% the generous estimate I gave above, which sounds plausible to me. – Nat May 13 '17 at 23:01
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    @Nat No, my estimate is for using both cores at once. The carrier is almost always on both reactors, so I don't know if you could get better efficiency by alternating which reactor was online. There is a lot of ancillary equipment with high power demands that must be run to operate a rector, so you probably gain a lot in efficiency by keeping one reactor shut down. But that's not how carriers operate, so its kind of a moot point. – kingledion May 13 '17 at 23:23
  • I don't get it. Unlimited means that it has no limits, while the answer says pretty clearly that the Vinson need refuelling and cannot simply go on forever. So it is not a matter of being nitpick, is that it's totally wrong from every point of view, especially because saying "Yes" means that the thermodynamics laws can go to hell and that we invented perpetual motion. – motoDrizzt May 18 '17 at 10:23
  • @motoDrizzt Since it seems obvious that the aircraft carrier isn't a perpetual motion machine, I'd generally assume that folks would read "unlimited" in a more limited sense. But, you're right, it'd be weird if someone were to claim that some sort of transport was _literally_ unlimited. – Nat May 18 '17 at 10:31
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Using nuclear power to power the vessel, it's able to carry a fuel load many times beyond the longest possible missions and ranges. So, while not actually "unlimited," there isn't a plausible scenario where they'd run short. As mentioned in Nat's answer, the fuel core for Nimitz-class aircraft carriers is estimated to be at least 20 years. No mission would take 20 years, and that leaves plenty of leeway for outfitting with a replacement core if they are using up power faster than the original estimates.

USS Nimitz - wikipedia

How is it possible? Radioactivity <> explosiveness. You've probably noticed that nukes, while more widespread than we'd like, are not universal. The concept of fission and fusion are well known, so why is this? Because creating a device that is capable of creating an uncontrolled fission chain reaction is not that simple. You'd need to be able to have enough to create the reaction, but not enough that it would spontaneously happen.

Amid all the fear and confusion, one fact remains: It is notoriously difficult to build an advanced nuclear weapon.

"It's a very challenging goal," Leonard Spector, deputy director of the James Martin Center for Nonproliferation Studies, said today in a telephone interview.

... Other significant hurdles remain, related to everything from enriching the material, to building a successful detonation device, to delivering it all with a conventional missile that may not be able to carry the extra weight of a nuclear warhead.

... The tricky part

In order to sustain the type of chain reaction necessary for a bomb explosion, the atoms need to be held in a modified state known as "supercritical mass" so that more than one of the free neutrons from each split hits another atom and causes it to split. A supercritical mass is formed in a uranium bomb by initially storing the fuel as separate subcritical masses to prevent the bomb from detonating too early, and then joining the two masses together. The bomb also needs to be designed to allow enough of the chain reaction to take place before the initial energy from the explosion causes the bomb to fail.

But a major problem with uranium bombs... is the fact that the material happens to be the world's heaviest naturally occurring element.

Live Science: Why It's So Hard To Make Nuclear Weapons

Also, the main obstacle is enriching enough uranium to have it be capable of being used to trigger a thermo-nuclear explosion.

It seems like most of your concern focuses on the idea that a nuclear plant makes for a juicy explosive target that could set off a nuclear explosion. The differences between enrichment needed for power generation and weaponization make that not so.

In order to be "weaponized," uranium much be enriched to a level of Uranium 235 of 80% or more (ratio of U-235 to U-238).

Union of Concerned Scientists: Fissile Material Basics

In order to be capable of a fission reaction for power generation, that level is below 5%. So, even if I have a reactor running on 20% enriched fuel, a direct hit isn't going to trigger a massive explosion.

WorldNuclear.org: Uranium Enrichment

HOWEVER, due to space constraints and the desire to get maximum bang for the buck, the nuclear military vessels do use uranium that has been enriched to a weaponized level. The design of the power plants is such that it isn't concentrated all together to reach that supercritical mass. You have many separate fuel rods, along with slowly dissipating materials that dampen the reactions for a more even, long-term "burn" of the fuel.

On a side note, there is obviously concern about proliferation of stolen weapon grade materials with more uses in a more widespread manner. Moreso, probably, than fears about an accident or explosion from a strike.

Wikipedia: Nuclear Marine Propulsion

BlueBird Electric: USS Dwight D Eisenhower (has photo of nuclear fuel rod array)

In slamming together the sub-critical masses into a supercritical one, a conventional explosive charge is carefully crafted, designed and triggered. Being hit by a bomb or shell would not have these characteristics.

Now, there are the dangers of any normal nuclear power plant - if the reactions get too vigorous, the reactions will speed up to the point where the heat can't be controlled and the generator, itself, will melt down. There would be danger of fuel ignition if a carrier used diesel, kerosene, gasoline, coal or whale oil, though. Nuclear doesn't seem to be that much of a danger. Radioactivity is probably the main concern.

So why not use it in regular transportation? Well, the nature of a military naval vessel is that it's going to be heavily armored and protected against attack. As such, any kind of shielding or protection to prevent radioactivity from harming the crew would not be an imposition upon the design of the craft, which does not put a premium on maximum fuel efficiency.

They also have massive numbers of crews designated to running all of the ships processes and systems, including the power plants and engines, no matter what the design. Nuclear plants require constant monitoring and management.

Are we going to trust someone who doesn't know how to use the turn signal properly to monitor and manage a mini nuclear power-plant in their vehicle? The scale of the operation needed to run an aircraft carrier makes a nuclear plant not a bad option. Not true for your compact Kia.

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    Most of this answer is speculation and opinion. How do we know that these are the real reasons? – Oddthinking May 10 '17 at 00:47
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    "Uncontrolled fission chain reaction". I think the term is "collision cascade". https://en.wikipedia.org/wiki/Collision_cascade –  May 10 '17 at 02:08
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    My understanding is that shipboard reactors use bomb grade uranium. The thing is the only way you can get a nuclear explosion is if you assemble it very fast. Simply gathering together too much material results in a "blast" so weak that people at close range have been known to walk away (but they die later of the radiation.) – Loren Pechtel May 10 '17 at 02:53
  • Re "more widespread than we'd like", just who are you calling "we" here? – jamesqf May 10 '17 at 03:55
  • @fredsbend - instead of using the term, and then having to explain what it is, I just used the explanation. – PoloHoleSet May 10 '17 at 13:33
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    @LorenPechtel - WTF? Right you are, editing to reflect that, as soon as I get links to the amount used and how it's used. – PoloHoleSet May 10 '17 at 13:38
  • @Oddthinking - "How do we know these are the real reasons?" - can you be more specific? Those are the real reasons we don't have radioactive power plants for our cars (if so.... really?)? The real reasons why it won't set off a thermonuclear explosion if hit? – PoloHoleSet May 10 '17 at 13:41
  • "'s able to carry a fuel load many times beyond the longest possible missions and ranges" Says who? – Oddthinking May 10 '17 at 15:12
  • "Because creating a device that is capable of creating an uncontrolled fission chain reaction is not that simple." Says who? – Oddthinking May 10 '17 at 15:12
  • "So, even if I have a reactor running on 20% enriched fuel, a direct hit isn't going to trigger a massive explosion" Says who? – Oddthinking May 10 '17 at 15:13
  • "there are the dangers of any normal nuclear power plant" Who says the ones you listed are the only ones, or the most important ones? – Oddthinking May 10 '17 at 15:13
  • "They also have massive numbers of crews designated to running all of the ships processes and systems, including the power plants and engines, no matter what the design." Who says there is no possible design that can run without maintenance? [Counter-examples](https://en.wikipedia.org/wiki/Nuclear_power_in_space) – Oddthinking May 10 '17 at 15:15
  • "Not true for your compact Kia." Says who? – Oddthinking May 10 '17 at 15:15
  • Let us [continue this discussion in chat](http://chat.stackexchange.com/rooms/58514/discussion-between-poloholeset-and-oddthinking). – PoloHoleSet May 10 '17 at 15:17
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Does the aircraft carrier have unlimited distance range?

Not really true, no.

While the ship does have sufficient power, the crew will starve at some point, so it still needs to resupply after a couple of months.

The storage capacity of Nimitz Class carriers for refrigerated and dry food can support a crew of 6000 for Aproximatly 70 days.

But, the carrier's mission is to support Aircraft, not just sail around and feed the crew:

So normally, the Carriers are outfitted with 90 days of aviation and power plant related spare parts and has onboard repair capability for most all of high failure aviation components.

Additionally, Nimitz Class Carriers can carry a max load of 3.3M gallons of JP-5 jet fuel and average 2.6M Gallons onboard (with peacetime replenishments).

https://www.quora.com/How-long-could-a-U-S-aircraft-carrier-sustain-itself

How can this be possible? It says it uses nuclear power/engines.

Correct.

How can this be safe for a military transportation? One hit and the carrier can blow up.

Incorrect. Nuclear reactors don't create a nuclear explosion like a nuclear bomb if something goes wrong. Nuclear reactors and nuclear bombs are similar but different concepts.

However, if the reactor is damaged, there will be radiation leaks - but if you consider the fate of a carrier without power in a combat situation, the ship will almost certainly sink and the people on board will almost certainly die.

Additionally, most war ships, including carriers, have an armory. War ships with conventional propulsion have fuel tanks. If these are hit, the ship is somewhat likely to go down.

If the technology really is there and allows safe usage of the carrier[?]

For certain definitions of safe. Military applications have vastly different safety levels than civilian applications.

why is this not used in another type of transportations?

It is used in other military types of transportations on sea. It's also used for icebreakers. The technology makes use of the surrounding water for cooling, so it cannot be used on land or air.

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