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No, not that one. This one. USS Enterprise pic: courtesy Wikipedia/US Navy

I want to see the USS Enterprise fly, but I'm curious how it would be accomplished in any realistic fashion.

Now, the world I'm building that needs a flying Enterprise has some advantages that might help us. Gravity is at 0.6 Earth Standard, and the atmosphere is considerably more dense. (Let's say 50% more)

  • How could this be done in the field? (using scavenged parts not necessarily only from the Enterprise herself)
  • How could it be done with the benefit of a full shipyard? (with the full technological and industrial might of the US Navy)

Note that I am aware of the relation between gravity and atmospheric density. This world gleefully ignores it for... reasons.

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  • $\begingroup$ Um is anti-gravity fair game? Or only using known means? $\endgroup$ – mechalynx Oct 7 '14 at 11:50
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    $\begingroup$ I would prefer known means, within current or near technology. $\endgroup$ – Danny Reagan Oct 7 '14 at 12:31
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    $\begingroup$ The Enterprise as it exists, or a structure very similar to it? In other words, is it fair game to use different materials to reconstruct the carrier? For example, replacing regular steel with a much lighter composite? $\endgroup$ – NotMe Oct 7 '14 at 14:30
  • $\begingroup$ The Enterprise as she exists. Stripping out some of the internal bulkheads and such is acceptable. (In the current iteration of the story, the Enterprise is modified in the field, by her crew.) $\endgroup$ – Danny Reagan Oct 7 '14 at 14:50
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    $\begingroup$ The Enterprise is a floating nuclear reactor and they need A LOT of water. A sailing Enterprise has access to copious amounts of sea water for cooling, cleaning, distilling, and steam for the turbines. A flying Enterprise will need to make due with something else. $\endgroup$ – Schwern Oct 7 '14 at 17:37
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edit: This answer arrives at the wrong conclusion because I made a mistake in my calculation of the craft's mass in Newtons. Spoiler alert: you can't make it fly this way. The rest of the analysis stands however, as far as I know. See the end of the post and the comments for details.

Lets crunch some numbers:

  • We can use displacement to figure out its mass:

    • The Enterprise has a displacement of 94,781 tonnes[1] at sea-level gravity on Earth, which gives it a weight of 56,900 tonnes at .6g gravity.
  • While less gravity would normally mean less density in the atmosphere, we'll go with the prescribed +50% density from the question. While that would make the air heavier, since the carrier is immersed in the atmospheric fluid, the forces cancel out (especially during flight - but it might have a bit of trouble trying to disengage the water surface - we'll disregard it for now).

Lifting it up

There are two obvious ways to lift an aircraft carrier-sized object in the air - one is using a standard airship approach (stick it under a huge balloon) and the other would be a VTOL approach[7]. Since others have answered on the airship case, I'll stick with the VTOL - I think it's preferable since:

  1. You want to modify an existing craft to fly
  2. You'd want to maintain the same functionality, thus you want to reuse the same facilities and structures as much as possible

Making an airship is probably a lot simpler however - VTOL is more complicated and costly, but it's damn cool.

  • The Enterprise has 8 reactors, giving a total of 210 MW[1] of power.
    • The Avengers carrier resembles a Fan-in-Wing setup[8] and this seems viable as an option for such a craft
    • Thrust vectoring would be an option, but it doesn't give us enough control to use downward-facing engines to move forward fast.
    • Although ideally we'd be able to use all fans to lift and move, the requirement for stability here is high - the carrier, unlike a helicopter or plane, can't pitch at all (doing so might cause people and planes to roll off - real carriers tie planes to the deck, but there's still a very small margin for pitching here). This means we'll have to use separate fans to control altitude and translate.

quadcopter

Lets see if our reactors have enough power to lift the carrier:

  • Since we're reusing existing reactors and the Enterprise used them for propulsion as well, we'll assume we have no fuel capacity and we can't use jet engines. That means we're using helicopter mechanics pretty much.
  • We need to generate thrust higher than its weight in order to lift it up, which means over 560 KN of thrust (edit: this is incorrect, I was off by 1000 because of a mistake in my units, it's actually 560 MN. See end of this answer.). Using this propeller thrust equation[14] and assuming:

    • air density at 150%
    • 45 MW used per propeller
    • fan diameter equal to the width of the craft: 80m

      we get:

      ((pi/2)⋅(80)^2⋅(1.225⋅1.5)⋅(45e6)^2)^(1/3) = 3.34 MN

      assuming I haven't made a horrible mistake in the calculations.

That gives us a single fan capable of lifting the carrier with a TWR of almost 6:1. We can't use a single fan though, so we'll split it between two, each with a diameter of 50m, for altitude, which gives us a total of 4.89 MN. We have to place these so that their thrust vector aligns with the center of mass of the craft, so probably near the middle.

So far we're using 90 MW, so we have room for our propulsion propellers. If we have two of them, mounted in the back-side, 10m in diameter each and pumping 25 MW to each of them, we get 565 KN of thrust for each, which is enough to move the craft easily (TWR of 2:1).

Summing up

That's a total of about 9.8 MN upwards thrust and 1.13 MN of forwards thrust at 140 MW of power, which is 2/3 of our capacity. We haven't factored in the weight of the propellers yet so lets do that.

Extrapolating from the size of the GE90 jet engine[15] which is the largest one yet, we arrive at a weight of 110 kN for each of the 50m fans and 22 kN for each of the 10m fans. Adjusting for the lower gravity and summing, that's a total of about 160 kN of extra weight due to the fans. At our 720 kN of mass and accounting for all the engines, we have a TWR upwards of 13.6 and forwards of 1.57. This means we'll rise very fast and have a high maximum altitude but will move forwards relatively slowly.

These calculations aren't exact (obviously) and I'm not an expert on this kind of thing, but it seems that, if you're willing to deal with the extra engineering challenge of making it a VTOL, it should be possible at a lower gravity and higher air density. You could of course adjust the sizes to make better use of your power, but it depends on what you want to favor - flying or moving fast.

Demitri has found a horrible mistake I made. My original calculation of the mass of the craft in Newtons was off by 3 orders of magnitude (1000) which means everything after that is pretty much invalid. The engines would have to be about 100 times more powerful, even under lower gravity and higher atmospheric density to allow this craft to fly. Not sure what to do with the answer except note that the conclusion is incorrect. I'll leave it as it is so the overall post isn't confusing.

According to Demitri's corrections, with the correct mass of $558 MN$ for the carrier, the power required to lift it is $172 GW$, which far exceeds the capacity of the carrier's reactors.

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    $\begingroup$ @MikeL. I thought turbojets where fuel-based, that's why I went with fans. Couldn't having more small fans instead of the 2 massive ones solve the size issue? As I said above, the only reason I went with 2 was convenience in calculating things - there's plenty of power left and calculating for smaller fans is easy. $\endgroup$ – mechalynx Oct 7 '14 at 21:11
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    $\begingroup$ Accepted for showing the partial feasibility of modding the Enterprise as she is. (obviously, a lot of quality salvage would be needed to build the turbines) I must admit to being torn between blimp and VTOL, but I'm afraid the cool factor won out. :D $\endgroup$ – Danny Reagan Oct 8 '14 at 16:15
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    $\begingroup$ "there are two obvious ways to lift an aircraft carrier" - no. There are zero obvious ways to lift an aircraft carrier. You're a madman! $\endgroup$ – corsiKa Oct 20 '14 at 21:31
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    $\begingroup$ You made a mistake in your calculations: you used $1/g$ instead of $g$. So you need about 2000 times as much power as you used (to 1 significant figure). $\endgroup$ – Demi Apr 29 '16 at 7:16
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    $\begingroup$ @ivy_lynx $94,781~\text{tonnes} * 1000~\frac{\text{kg}}{\text{tonnes}} * (9.81 \frac{m}{s^2} * 0.6) = 558\text{MN}$ $\endgroup$ – Demi Apr 30 '16 at 2:31
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Of course there is always The Avenger's flying carrier (which is ridiculously impractical but should be mentioned).

Flying Aircraft Carrier

Moving away from fantasy towards reality then actually there have been some serious real-world investigations along these lines.

http://en.wikipedia.org/wiki/Airborne_aircraft_carrier

USS Akron (ZRS-4) and USS Macon (ZRS-5) were two rigid airships built for scouting duties for the U.S. Navy and operational between 1931 and 1933.

Following experiments with launching and recovering small aeroplanes using the USS Los Angeles (ZR-3), the USA designed the Akron and Macon with internal hangars able to house a number of Curtiss F9C Sparrowhawk biplane fighters. The fighters were launched and recovered using a "trapeze" mechanism

USS Akron in Flight

This leads us to our first point, the carrier will be slow moving and extremely heavy so it would not lend itself to heavier-than-air flight. However airships are excellent for lifting large loads at slower speeds. They also do not disrupt the airflow around themselves so would be better for landing and taking off from.

In earth conditions:

The USS Enterprise weighs 94,780 tons.

1000 cubic feet of helium can lift 65.82 lbs.

So we need 2 879 975 000 cubic feet of helium.

The carrier itself is 2106 feet long and 1522 feet wide so if we make the balloon the same size as the carrier that gives us a helium balloon 2106 feet long, 1522 feet wide and 900 feet high

That's a damn big balloon! There's no complete blocker on building it though, it would be expensive, slow, and vulnerable but it certainly could be done if enough money was thrown at it.

In our hypothetical world

The gravity is 0.6 earth standard, that will make the same change to the weight:

The USS Enterprise now weighs 56,868 tons.

The atmospheric density is hard to calculate for as the helium will also be compressed more if the pressure rises. Lets say the atmosphere has earth pressure but increased density. In that case Helium has 50% more effective lifting power and 1000 cubic feet of helium can now lift 98.73lbs.

So we now need 1,151,990 cubic feet of helium.

That now gives us a helium balloon 2106 feet long, 1522 feet wide and 359 feet high

As you can see the altered conditions of your world make things much easier.

But what about the weight of the ballon?

The weight of the lifting gas itself is already included in the buoyancy figures so can be discounted. The balloon structure itself will have a noticeable weight but it will still be a tiny fraction of the weight of the aircraft carrier so while it would need to be allowed for if someone were designing this for real it will not make large changes to these figures which are illustrative anyway.

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  • $\begingroup$ The Avengers carrier was exactly what I first thought about when reading this question :P I'm crunching numbers to see if it's doable. Nice one! - Btw, you mention the Enterprise weighs 94,780 tons, but that's the displacement, not the weight. $\endgroup$ – mechalynx Oct 7 '14 at 12:32
  • $\begingroup$ Don't forget the lesser gravity at work here. 0.6g should allow for some interesting stuff. $\endgroup$ – Danny Reagan Oct 7 '14 at 12:33
  • $\begingroup$ you're not including the weight of the balloon itself in your calculations $\endgroup$ – Colin Pickard Oct 7 '14 at 12:33
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    $\begingroup$ @ColinPickard You're right, I've added a section to discuss that. $\endgroup$ – Tim B Oct 7 '14 at 12:39
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    $\begingroup$ I'm way out of my depth here as physics go, but would this also be feasible using hot air for lift in lieu of helium? I mean, air is a lot cheaper than helium, you don't need to worry about leaks since you can always produce more on the spot, and you already have a nuclear reactor that will need cooling anyways. I just don't have any idea about the lift characteristics of hot air. $\endgroup$ – Mike L. Oct 7 '14 at 20:17
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Yes, an airship version of the USS Enterprise is practical. It would be several times the size of the Hindenburg but well within reach of modern technology.

The main constraints would be:

  • Weight. Without a 100% rebuild, the USS Enterprise is far too heavy to make a good gondola design. You would need a staggering amount of lifting gas. Not impossible though, and modern airship designs incorporate aerodynamic improvements, which you could take advantage of by using the copious electrical power from the nuclear reactor to propel it (think 100+ modern jet engines)
  • Aircraft operations. Assuming it carries the USS Enterprise's full complement of aircraft, a substantial part of it must be dedicated to aircraft operations. If you replaced the Enterprise's flight deck with a gigantic Zeppelin structure, you could operate from a runway on top, or change your aircraft to support cradle launch (this was done with biplanes, not sure if it would work for modern jet fighters)
  • Power. A large part of your weight budget has to go to the nuclear reactor and jet fuel for the aircraft.
  • Crew accommodation. not a problem if you keep most of the original structure intact.
  • Operations - You would need massive new mooring facilities around the world for maintenance.

Obviously the airship route requires the support of a full shipyard, including a lot of facilities custom designed for the project. All of it well in reach of current technology, if a little expensive.

EDIT: With the increased density and reduced gravity, the proposed airship would be about 3 times longer than the proposed US Army heavy lift cargo airship, so manoeuvrability and docking should not be too bad:

US Army heavy lift cargo airship

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So you want to write that a crafty crew in dire need made thier ship to fly. I think it is doable in 3 steps.

  1. They cut off the upper deck from the hull, reinforce it to be able to withstand weight, and mount all the equipment they would need in flight on the deck or under it. Modern ship can literally be peeled like an egg, as hull is not the integral part.
  2. They sew a lot of ballons from I don't know what material. They provide heating to the balloons.
  3. They tie balloons to the deck and get themselves something of a big flying raft.
  4. They are lucky to have appropriate winds.

Now, to the problems.

  • In big modern ships, all fixtures on the top are connected not to the desk, but to the internal structure. They will have to re-weld it all to the desk.
  • Energy. Not only electricity, ship has a network of pipes, supplying pressurised steam for all systems.
  • A shot from main weapon literally makes a battleship to shake and move in the water sideways. In case of flying, in will rock violently.

After all, I think, it is doable, but building several small zeppelins from ship's parts would be easier and more effective.

P.S. How happens that your planet has lighter gravity but thicker atmosphere? I though these things are connected. This although means that locals will invent balloon-flying nearly as early as sailing, which means they may end up with elaborate ships. They can literally jump from cliffs with umbrellas!

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    $\begingroup$ My world plays around with the laws of physics. A lot. Its part of the plot and stuff. +1 for jumping off cliffs with umbrellas, made me laugh. :D $\endgroup$ – Danny Reagan Oct 8 '14 at 11:58
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You would have to change the power supply. The reactor on the CVN-65 is water cooled using around 50gpm. SOURCE This works because the carrier is sitting on literally a sea of coolant. This allows the carrier to replenish cool water and expel waste heat quickly and easily with out having to maintain a large reserve of coolant on board. The need for the coolant would make nuclear power a poor choice for a large air ship like this.

Now if you have something like a ZPM you could make the types of changes that would be needed to make the Enterprise airworthy. Another issue is going to be keeping lift. Lets assume that 250knots would be sufficient for lift to keep the ship airborne. That is going to make the flight deck incredibly hazardous. Anything over 50-60 knots is probably going to be unmanageable for both aircraft landing and taking off, and crew working on the deck.

So you are going to need a hover capability. This would allow the ship to go into near stationary mode for deck work then resume normal flight speeds.

You will also need to make the control tower able to drop into the deck for flight speed mode. Something more interesting for full speed launches might be to drop the planes more like bombs allowing the planes to accellerate to flight speed after they have been dropped. This would allow for a much more rapid deployment of a squadron as well.

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  • $\begingroup$ An excellent point on the coolant, I had not considered that. $\endgroup$ – Danny Reagan Oct 8 '14 at 11:57
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I did a funny calculation that I want to share. Let's take a ship called "Oasis of the Seas" as example. Its gross tonnage is 225,282. We can estimate it's cargo volume as GT/0.32 = 700 000 m3 = 700 000 000 litres. One litre of helium on Earth can lift 1 gramm of weight besides itself. In your condition + heating let's say it is 4 gramms. 2800 000 000 gramms make 2 800 tonns of lifted weight.
This much lift will the crew get, if they fill cargo volume with hot balloons. Unfortunately, "Oasis of the seas" weights 100,000 tonns. But crew will have fun. Switching to hydrogen will double the lifting power, but remove the fun.

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  • $\begingroup$ For what it's worth, storing that much Hydrogen adds a lot of risk for a very different kind of "Fun" :) $\endgroup$ – Mike Caron Oct 10 '14 at 16:57

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