Month: March 2022

A few years ago, I did a thought exercise where I deduced what a robot tank would be like. I concluded that the lack of human crewmen would allow such a tank to be shorter, lighter, and less voluminous than manned tanks, but that it would still look unmistakably “tank-like” and would be in the size range of current tanks. Thus, the future of armored warfare will look much the same as its present, even if a lot of new technology will be hidden under the hood.

Now I wonder if this would be the case for warships. Given their great variety, I have to restrict my analysis to just one type, the aircraft carrier, but my key conclusions can probably apply to the rest. And since there are many types of aircraft carriers, I’m focusing this analysis on supercarriers in particular, which only the U.S. Navy has at present. The newest American supercarrier that is also fully mission-capable is the U.S.S. George H.W. Bush, and as such, it’s fair to call it America’s “best” aircraft carrier. So what would a robot George Bush look like?

First, the ship’s gross architecture would stay the same. It would need an oblong hull with a pointed front to minimize hydrodynamic drag. The top would need to be flat and uncluttered so planes could land on and take off from it. Even in the far future, most planes will still take off and land the traditional way on runways. Even with more advanced aircraft technology, fighter planes won’t hover straight up into the air to take off. Vertical takeoff and landing (VTOL) will, thanks to physics and the usefulness of “lift,” always be a MUCH less fuel-efficient way to get airborne and then return to the ground than speeding down a runway. Every extra pound that a VTOL plane needs to land and take off is one pound it doesn’t have for weapons.

In fact, the only external difference between the U.S.S. George H.W. Bush and its robot equivalent would be the ships’ islands. On an aircraft carrier, the “island” is a vertical protrusion on the otherwise-flat flight deck, and it somewhat resembles a small office building. It provides mounting points for radars, radios, and other sensors, and also contains the bridge, flight control room, and smaller rooms for specialized tasks.

The captain and his command crew are in the bridge, where they monitor and control overall ship operations. The flight control room is one level above that, and is where other officers coordinate aircraft movements on and off the carrier. It’s obvious why these crewmen need to be situated in a high place where they have good views of the ship’s flight deck and the surrounding waters. In turn, the physical sizes of human bodies and our need for clearance space to walk around each other dictate the dimensions of those rooms, and ultimately, the shape and size of the island. Thus, this part of an aircraft carrier is designed around the human form.

On an automated aircraft carrier, such considerations could be dispensed with since humans wouldn’t be aboard. Visual monitoring of the flight deck and seas could be done with cameras, allowing the bridge, flight control room, and other small rooms in the island that support their functions to be deleted (computers located deep inside the ship’s hull would watch the video feeds). As a result, the office-building-like island would be thinned down to a mast. It might be of a metal lattice design, or could be solid with a geometrically faceted exterior to reduce the ship’s radar signature.

A thinner island would help a robot aircraft carrier by increasing its flight deck area and reducing the air turbulence over it. The ship’s survivability would also be improved since its command staff wouldn’t be kept in an exposed, vulnerable location. Instead, it’s command functions would be done by a central computer located in an armored room below decks.

A Nimitz-class carrier like the George H.W. Bush typically contains 56 planes (mostly fighters like the F/A-18) and 15 helicopters. Our robot version of the carrier would have autonomous versions of those aircraft. Since the planes lack human pilots and crewmen, things like ejection seats, steering controls, bubble canopies, computer screens, and oxygen pumps could be deleted, reducing gross weight. That weight savings would let the aircraft take off and land a little more easily, possibly reducing the lengths of runway they needed, and hence reducing the overall length of the ship.

However, any such benefit would be tiny since the weight of the pilot and his supporting equipment is relatively minuscule. For example, an F/A-18 Super Hornet that is fully fueled and armed for a combat mission could weigh over 50,000 lbs, less than 1,000 lbs of which is represented by the pilot and his aforementioned support gear. An unmanned F/A-18 might be able to take off and land on a runway a few feet shorter than the manned version, but that’s it. Therefore, the lengths of the runways used for takeoffs and landings on the robot carrier would either be the same as those on the human-crewed counterpart, or imperceptibly shorter.

The reduction of the island’s mass might result in the flight deck being slightly narrower since the port side of the deck wouldn’t need to flare out as much to counterbalance the weight of the starboard side.

The robot ship’s “freeboard,” which refers to the vertical distance between the surface of the water and the top of its flight deck, would be the same or very close to the manned version’s, which is 57 feet. In general, as ships get longer and heaver, they need higher freeboards to keep stable. A high freeboard is also very important for ships meant to sail through rough seas, which an aircraft carrier would need to do since wars don’t pause for bad weather anymore. There’s no reason to think the manned USS George H.W. Bush’s freeboard is not optimal given the ship’s size and function, nor is there evidence that the crew’s uniquely human needs affected the freeboard.

The argument for this optimality is strengthened by the example of the USS Midway, another aircraft carrier that served the U.S. Navy from 1945 to 1992. In the 1960s, it went through a major renovation in which the flight deck was widened to accommodate the bigger planes that were entering service, which added substantial weight to the ship and made it sit lower in the water. The reduced freeboard hurt the Midway‘s performance in rough seas, and the ship also had more problems with waves splashing into the ship’s open side elevators, and even splashing over the bow to soak the flight deck. The problems kept it from conducting flights in sea conditions that the George H.W. Bush could still operate in. The contrast between the ships further supports the conclusion that the Bush’s freeboard is already optimized, and wouldn’t be different or would only be a tiny amount different in an autonomous version of the ship.

To summarize this analysis of the robot carrier’s exterior, it might have have a slightly different profile and slightly different dimensions to its flight deck compared to the manned version. However, this would be very hard to see, and by far, the most visible difference would be to the island.

The ship’s interior layout is the most subject to human needs since it is where almost 6,000 people work and live, 24 hours a day, for months on end. Before moving on to that half of this analysis, it’s important to point out that an autonomous aircraft carrier would still need crewmen, though they’d be robotic. They would need to be able to move around the ship for inspections, maintenance, repairs, emergency response, and to transport things. Therefore, the inside of the robotic George H.W. Bush would still be comprised of rooms, doors, stairways, and passageways to enable the crew to access every part of the ship.

To understand how the ship’s interior layout would change if human-centric design concerns were abandoned, first study these cutaway illustrations of the George H.W. Bush’s class of ships:

Let’s start by distinguishing the features and sections of the ship that exist because of the presence of humans, or are larger than they need to be because of human physiology, from the features and sections that do not. The hangar is massive and is necessary to house the carrier’s aircraft for maintenance, repairs and modifications. It’s size is dictated by the sizes of the planes and by the need to have enough space around each one to be able to move them around and provide crew with access to them. There’s no reason to assume the size or layout of the hangar deck would be different if the carrier were autonomous, so the largest single room in the ship would be the same.

This is also true for the series of large rooms at the ship’s lowest point, called “the fourth deck,” which contain its nuclear reactors, electrical generators and gearing that connects the engines to the propellers. Smaller rooms on the fourth deck that store jet fuel, munitions for the planes, and water for the steam catapults are also not designed around human needs. (They are stored at the lowest part of the ship to keep its center of gravity low, improving its stability.)

It’s impossible to generalize about all the other decks of the ship since rooms dedicated to purely mechanical functions (e.g. – jet engine repair shop, steam catapult piping spaces) are mixed in with those dedicated to human crew needs (e.g. – bunk rooms, hospital, cafeteria). All we can say is those of the former category would stay, while the latter would disappear, leaving a lot of empty space.

The robot crewmen wouldn’t need to eat, sleep, party, or satisfy hygienic needs, and would probably stay at their work stations almost all the time. The only room dedicated to their unique needs might be a specialized repair shop and spare parts room. Those rooms would take vastly less space than the bunk rooms, bathrooms, cafeterias, bakeries, laundromats, conference rooms, etc. that would need to be there to satisfy a human crew’s needs.

The ability to work constantly would also allow a robot crew to be smaller than a human one without reducing work output. Assuming an average sailor works a 12-hour day and works as efficiently as a robot when he’s on duty, 3,000 robots could to the work of 6,000 humans. The disparity might actually turn out to be more extreme.

Getting rid of the human crew wouldn’t just save internal space–it would save weight. The clothing, beddings, beds, furniture, cooking appliances, laundry machines, bathroom fixtures, lockers, food, and water (in excess of what is needed for the steam catapults), plus the plumbing and electrical/data cables needed to support some of those features add up, and if the humans disappeared, so would all of those things. Ironically, a robotic aircraft carrier would also have fewer computers and display monitors in it since the machines wouldn’t need them because they’d be able to directly interface their minds with the ship’s sensors and main computer. Lessening the number of devices would also save weight.

Moreover, the need to divide a ship’s internal space into rooms that only exist due to human needs, like walling off an area to create privacy for a bathroom, adds weight since the walls themselves are heavy. If the ship weren’t designed around human needs, more parts of the ship could be large, open areas, cutting overall weight.

With these considerations in mind, a low estimate for the amount of weight saved by eliminating the human crew is one ton (2,000 lbs) per person. The total weight savings is therefore 6,000 tons, which is a small but still helpful boost for a vessel displacing 114,000 tons.

Our robotic version of the George H.W. Bush could deal with its excess internal volume and weight savings in a three different ways. The simplest option would be to just accept having more empty space inside of itself, and to capitalize on the slight increase in sailing speed and ship energy efficiency that would owe to being lighter. The ship would have the same number of decks and the same internal volume and the manned version, but the rooms would be larger, there would be less of them, and they would be less full of stuff. This option would let the carrier be more mission flexible since it could double as a transport.

The second option would be to fill the robot George H.W. Bush‘s newly empty spaces with 6,000 tons of other stuff to improve its performance in some way. Nimitz-class aircraft carriers are powered by nuclear reactors whose uranium lasts for 20 years, so it wouldn’t help to add spare uranium rods to the ship (refueling is done in port for the sake of safety, anyway). However, other types of essential supplies are depleted over the course of a multi-month cruise, forcing a carrier to halt operations so it can pull alongside a cargo ship for a tedious resupply process called “replenishment.”

The lack of human crewmen would mean the carrier would no longer need food replenishments, but it would still need replenishments of aviation fuel, munitions, and spare parts for its aircraft and itself. Given that a Nimitz-class ship’s 8,500 ton supply of aviation fuel , called “JP-5,” only last about seven days during routine operations, and even less during round-the-clock combat operations, the robot version of the ship would derive the most benefit from adding more fuel tanks.

If the capacity of the robot George H.W. Bush’s aviation fuel storage tanks increase from 8,500 to 14,500 tons, if JP-5 is 6.8 pounds per U.S. gallon, and if a gallon of liquid is 0.134 cubic feet, then we can calculate how much volume the added 6,000 tons of fuel will take up inside the ship.

6,000 tons x 2,000 (pounds / ton) = 12,000,000 pounds
12,000,000 pounds / 6.8 (pounds/gallon) = 1,764,705 gallons
1,764,705 gallons x 0.134 (cubic feet/gallon) = 236,470 cubic feet

Glimpsing at this cross-section of the George H.W. Bush again, we see that aviation fuel in stored in long tanks stretching along the port and starboard sides of the ship (item #8 in the image). At the waterline, the ship is 1,092 feet long, and the draught (the distance between the waterline and the bottom of the ship’s hull) is 37 feet. So if we add 236,470 cubic feet of fuel tanks to the existing tanks indicated in the illustration…

1,092 feet x 37 feet = 40,404 square feet on port side and starboard side (80,808 total)
236,470 cubic feet / 80,808 square feet = 2.9 feet

…then we could fit in the extra fuel by widening the existing storage areas by a mere 2.9 feet. As a result, in the above illustration, item #8 would be very slightly wider on both sides of the ship, and item #10 would be very slightly narrower by the same amount. Adding 6,000 tons of aviation fuel is very doable.

The result would be a ship that weighed and handled the same as its manned counterpart, but could launch airstrikes against enemies for longer periods of time before having to pause to get a gas refill from another ship. The robot carrier’s upper decks would have a lot more empty space than the manned version, but it wouldn’t be able to fill it up without slowing itself down.

The third option would be to get rid of the surplus human spaces by deleting some of the ship’s decks, in turn reducing the carrier’s total interior volume. The mission-essential rooms that remained, like the repair shops and spare parts storage rooms, would then be reconfigured so they filled up the ship’s interior efficiently, with no empty spaces or oversized rooms. If you could explore this robot George H.W. Bush version, it would seem as claustrophobic as its manned counterpart, though it would take less time to tour the latter since it would have one or two fewer decks.

This modification would cut even more weight from the vessel, allowing it to travel faster with the same nuclear reactors, or to travel at the same speed with smaller reactors. The reduced mass would also make it faster and cheaper to build.

But this design change raises a potential problem: If we reduce the number of decks in the ship, then we reduce its overall height from the bottom to top. As discussed earlier in this analysis, we can’t reduce the freeboard because that’s already optimized. That means we have to reduce the “draught” (also called “draft”), which is the vertical distance from the bottom of the ship’s hull to the water’s surface. However, reducing the draught too much can make a ship unstable.

The George H.W. Bush‘s draught is 37 feet. If one deck were deleted, the draught would be 28.5 feet, and the ship’s weight would also decrease. Let’s say it drops from 114,000 tons to 100,000. Would the ship still be stable? Maybe. After all, there are several cruise ships whose dimensions with nearly identical dimensions, and they’re very seaworthy:

Ship name	Tonnage	Draught (ft)	Length (ft)	Width (ft)
USS George H.W. Bush (manned)	114,000	37	1,040	134
USS George H.W. Bush (robot) minus one deck	100,000	28.5	1,040	134
Carnival Sunshine	103,881	26.25	892	125
Costa Fortuna	102,587	27.23	892	125
MSC Orchestra	92,409	25.75	964	105
Norwegian Pearl	93,530	28.3	964	105

The cruise ships with draughts of 25.75 – 28.3 feet can handle rough seas, so the table suggests our robot aircraft carrier would presumably be able to do so just as well with a draught of 28.5 feet. However, it’s possible the demands placed on a ship designed for war are different from those of a ship designed for recreation, making a 28.5 foot draught insufficient for an aircraft carrier. A warship probably needs to be able to accelerate harder, make tighter turns, and endure worse weather conditions than a cruise liner. Unlike my research on the freeboard, I wasn’t able to find data on the optimal draught for a carrier, so I can’t answer the question, I can only conclude that a robotic aircraft carrier might have fewer decks and less internal volume than a manned counterpart.

In conclusion, while a robot version of the U.S.S George H.W. Bush wouldn’t look much different from a manned version on the outside, there would be substantial differences on the inside. All of the rooms and items that existed to service the needs of the human crew (bunk rooms, bathroom, cafeterias, offices, furniture, display monitors, etc.) would be missing. If the robot version retained the same amount of internal space as the manned version, then it would feel much emptier and more open inside. Its performance would also be superior to the manned version in one or more areas (e.g. – faster, more fuel for planes, better mission flexibility thanks to more storage space). If the robot version were designed to exclude excess volume, then it would feel about as constricted as the manned version, and it’s interior would be smaller, making it faster to do a full walking tour of the ship. A less capacious version of the USS George H.W. Bush may or may not have better performance in one or more areas than its manned counterpart, but for sure, it would be faster and cheaper to manufacture, allowing a country to make more ships for the same amount of money.

Finally, another observed difference would be lower levels of activity on an autonomous aircraft carrier since there would be far fewer crewmen. Moreover, since the crew would all be robots, they wouldn’t need to roam the ship to visit bathrooms, the cafeteria, buddies, or their bunks–they would stay put at their duty locations almost all the time. For example, a robot that fixed airplane engines would spend all its time in the engine repair shop. If it needed power, it would plug itself into a wall outlet in that room. It might only ever leave the room to visit the robot repair shop when it broke.

The robots would be of different sizes and designs to suit different roles on the ship. Obviously, they would need to be waterproof and capable of working normally underwater, to some reasonable depth and pressure level (100 – 200 meters). Unlike human crewmen, if the carrier were sinking, they would stay inside and focus on fixing the vessel, reducing the odds of it being lost. They could even keep working in parts of the ship that had filled with water.

Contrast that scenario with the premature abandonment of the U.S.S. Yorktown in WWII, which happened because the captain erroneously assumed the ship was doomed, and the human crewmen were afraid to risk their lives by remaining on it. The central computer of a robot George H.W. Bush would not make such a mistake, and its robot crew would unfailing execute its orders until the end, even in the worst of circumstances.

Links:

1. Basic info on the U.S.S. George H.W. Bush
   https://www.militaryfactory.com/ships/detail.php?ship_id=USS-George-HW-Bush-CVN77
2. An excellent cutaway illustration of the ship.
   http://patrickturner.com/carrier.html
3. George H.W. Bush contains 8,500 tons of aviation fuel.
   https://www.naval-technology.com/projects/george-h-w-bush/
4. That supply of aviation fuel only lasts a week during normal operations, and less during combat operations.
   https://www.quora.com/How-long-could-a-U-S-aircraft-carrier-sustain-itself-without-docking-or-restocking
5. The Midway-class carriers had poorer performance because they sat too low in the water.
   https://www.wikiwand.com/en/Forrestal-class_aircraft_carrier
   https://www.quora.com/If-the-USA-needed-to-could-they-make-the-museum-aircraft-carriers-USS-Midway-and-USS-Intrepid-operational-and-use-them-in-combat
   https://en.wikipedia.org/wiki/Midway-class_aircraft_carrier
   https://www.seaforces.org/usnships/cv/Midway-class.htm
6. A long list of cruise ships and their dimensions, including draughts.
   https://www.cruisemapper.com/wiki/753-cruise-ship-sizes-comparison-dimensions-length-weight-draft
7. A draught can’t be arbitrarily sized for a given ship. There’s a science to it (which I unfortunately don’t know). If a draught is too shallow, the ship will lose stability and be at risk of capsizing.
   https://www.marineinsight.com/naval-architecture/vessel-draft-vessel-draught-ship/