Mobile Modular Seabases were megaships whose individual modules could separate by themselves. It replaced the aircraft carrier as the dominant capital ship, and it, in turn, was replaced by the gravitic helicarrier.
(Note: The background section of this page uses most of the same words as Terra Futura's page on megaships to save time.)
The earliest capital ship in history was the ship of the line. In the 15th century, sailing ships began to be used not just to transport invaders, but also to fight battles at sea. This had been aided by the arrival of the cannon in Europe starting in Muslim Spain in the late 13th century. The first ship of the line was the carrack in the 15th century. This used by the Portuguese and Spanish navies. Other nations followed. In the 1500s, the ship of the line became longer and larger. The galleon was born. The galleon was the primary warship in the Battle of the Spanish Armada in 1588. The English galleons were superior to the Spanish ones. That is how the British won. In the 1600s, the English and Dutch navies adopted a tactic called line of battle. Ships went in single file and battered the enemy until they said uncle (That is a little joke on the fact tat they had had enough.) and retreated. Hand-to-hand combat became less essential. In the 18th century, designs became standardized. The USS Constitution was made of stronger wood than British ships and thus could resist cannon fire. In the 19th century, steam engines were added to ships of the line as an auxiliary power source. This would lead ship of the line to be replaced by the ironclad.
Ironclad warships first appeared in the second half of the 19th century. With the ironclad, steam power became the dominant power source on battleships. Guns that fired explosive shells replaced the old-style cannons. Wood was replaced with iron and steel. During the American Civil War, the CSS Virginia destroyed two Union ships of the line in the Battle of Hampton Roads. This showed that the ironclad was superior. The ironclad would become the dominant battleship in the second half of the 19th century. By 1892, the term ironclad fell out of common use in favor of the term battleship. But it was not until 1905, when the ironclad was obsolete.
In 1905, the Royal Navy commissioned the HMS Dreadnought, a revolutionary battleship design. The Dreadnought had a uniform main battery. Instead of a few big guns, there were a lot of small ones. The ship was also the first to be powered by a steam turbine. This started an arms race between the UK and Germany. The Dreadnought was so revolutionary it gave its name to a whole new generation of battleships: the dreadnoughts. This was the dominant type of battleship that was used in World War I. It helped win the war for the British. But so did air power, and by the end of World War I, planes made use of both guns and torpedoes. It was predicted that air power would replace the battleship. It was not until World War II that this prediction was proven to be correct.
The United States was the nation that made the aircraft carrier famous. Their first carrier was the USS Langley. The Langley had a solution for landing on a ship. The Arrester Gear was invented. A cable went across the deck. A plane with a hook used the cable to land. A hydraulic system then unstretched the cable. To take off, the plane used a pneumatic catapult. This design would be deployed on the USS Lexington, the USS Saratoga, the USS Ranger, the USS Yorktown, the USS Enterprise, the USS Wasp, and the USS Hornet. Despite the strides made by aircraft carriers, the Navy still firmly believed in the battleship. They viewed the aircraft carrier as a support. During World War II, however, the aircraft carrier was the dominant ship in the Pacific. The Essex-class was launched in 1943. Hydraulic catapults replaced pneumatic ones. The Essex-class proved important in defeating the Japanese. After World War II, the Midway-class was commissioned. It used steam catapults. The USS Midway also had an angled flight deck that became standard on all future aircraft carriers. A new system of mirrors and lights helped guide jet fighters to land. Very soon, aircraft carriers got bigger.
In 1955, the USS Forrestal was commissioned. Its class of ships were the first supercarriers. The Forrestal-class was so big, it could carry more than a conventional carrier. The Forrestal-class was soon followed by the Kitty Hawk-class. But aircraft carriers would be revolutionized by the USS Enterprise. The USS Enterprise was the first nuclear-powered aircraft carrier. This was followed by the Nimitz-class of supercarriers which became the dominant aircraft in the US Navy. However, by the early 21st century, the Nimitz-class was becoming obsolete. A new class of aircraft carriers was created to solve this problem.
In 2015, the USS Gerald R. Ford was commissioned. This ship and its sister ships, the USS John F. Kennedy and the USS Enterprise, were big and more advanced than the Nimitz-class. A new nuclear reactor design, the A1B, was used that was three times more efficient than the A4W used on the Nimitz-class. The RIM-7 Sea Sparrow missile was replaced with the RIM-162 Evolved Sea Sparrow Missile. A new radar was used. This was the AN/SPY-3 dual band radar. This used an Active Electronically Scanned Array system or AESA. The steam catapults were replaced by the Electromagnetic Aircraft Launch System or EMALS. This accelerated gradually, thus allowing the plane more aircraft as well as lighter and heavier aircraft. The arrester gear was also electric. Automation reduced the size of crews. Stealth features reduced radar profile. Later Gerald R. Ford-class carriers had other new technologies like laser weapons, dynamic armor, advanced tracking systems, and railguns. There was more stealth and more automation. These aircraft carriers, as well as civilian cruise ships, resulted in the development of megaships.
As ships got bigger, they could carry more passengers and cargo. One example of an early megaship was the Freedom. The vessel was 4,500 feet along its beam and a mile long. That was four times the size of the flagship of the Cunard line, the Queen Mary. The Freedom could hold 40,000 permanent resident, 20,000 permanent crew, and 40,000 passengers and visitors. In all, that was 100,000 people, more than could be carried on the USS Nimitz. If the Freedom were a solid unbroken hull, it would break in two from sheer bulk. Instead, the Freedom was made twelve separate modules connected seamless gimbaled joints. It slowly circumnavigated the globe every three years, stopping at seaports and islands. The ship was powered by 100 diesel engines at first. It was later refitted with fusion reactors. Drydocks had to be renovated to accommodate megaships like the Freedom. The military had a solution to this problem although it was unnecessary because drydocks were being renovated anyway. It was the mobile modular seabase.
Tech Level: 11
A mobile modular seabase was a megaship whose modules could separate in to separate ships. They could then assemble into one ocean-going air base. There were advantages to this design. They could be repaired in drydocks that had not been refitted to accomodate megaships. The modules could also move quickly to their destinations and assemble once there. This was useful during World War III. Mobile modular seabases helped the allies win. After World War III, the mobile modular seabase became the dominant capital ship on Earth, replacing the aircraft carrier. However, in the 22nd century, capital ships went into the air, and the mobile modular seabase was replaced with the gravitic helicarrier.