Net register tonnage (NRT, nrt, n.r.t.) is a ship's cargo volume capacity expressed in "register tons", one of which equals to a volume of 100 cuft .
 It is calculated by subtracting non-revenue-earning spaces i.e. spaces not available for carrying cargo, for example engine rooms, fuel tanks and crew quarters, from the ship's gross register tonnage.
 Net register tonnage is not a measure of the weight of the ship or its cargo, and should not be confused with terms such as deadweight tonnage or displacement.
The "Olympic"-class ocean liners were a trio of British ocean liners built by the Harland & Wolff shipyard for the White Star Line during the early 20th century.
 They were "Olympic" (1911), "Titanic" (1912), and "Britannic" (1915).
 All three were designed to be the largest and most luxurious passenger ships in the world, designed to give White Star an advantage in the transatlantic passenger trade.
 Two were lost early in their careers: "Titanic" sank in 1912 on its maiden voyage, after hitting an iceberg in the North Atlantic Ocean, and "Britannic" in 1916, after hitting a mine laid by the minelayer submarine "U-73" in a barrier off Kea in the Aegean Sea during World War I.
 "Olympic", the lead vessel, had a career spanning 24 years and was retired in 1934 and sold for scrapping in 1935.
Nimrod was the ship Ernest Shackleton used in his 1908 Antarctic Nimrod Expedition for the South Pole.
 It was a 41-year-old schooner of 334 gross register tons that had been used to hunt seals and whales.
 Shackleton, who paid £5,000 for the ship, had it re-rigged as a barquentine.
 It also had an auxiliary steam engine, but had a top speed of only six knots under this power.
 In addition, the ship was so overloaded with supplies for the expedition that it could not carry enough coal to make passage to the Antarctic from New Zealand, and Shackleton had to arrange for the ship to be towed to the edge of the pack ice by tramp steamer "Koonya".
 The New Zealand government paid half the cost of the tow; Sir James Mills, Chairman of the Union Steamship Company, paid the other half.
 The "Koonya" was captained by Fredrick Pryce Evans during the tow.
The "Athenic"-class ocean liners were a three ship class of ocean liners built by the Harland & Wolff shipyard for the White Star Line in the early 20th century.
Gross register tonnage (GRT, grt, g.r.t. "gt") a ship's total internal volume expressed in "register tons", each of which is equal to 100 cuft .
 Gross register tonnage uses the total permanently enclosed capacity of the vessel as its basis for volume.
The "Imperator" class ocean liners were a series of three ocean liners designed for the Hamburg America Line, commonly known as "HAPAG".
 These three ships were commissioned by the chairman of HAPAG Albert Ballin.
 Namely the "Imperator" (1912), the "Vaterland" (1913) and the largest, the "Bismarck" (1914).
 These liners were over 50,000 tons, sported three funnels and had a length ranging from 906 ft (276 m) to 955.8 ft (291.3 m).
 To this day, the "Vaterland" is the largest passenger ship operated by a German shipping company.
RMS "Majestic was a White Star ocean liner working on the North Atlantic run, originally launched in 1914 as the Hamburg America Line liner SS "Bismarck.
 At 56,551 gross register tons, she was the largest ship in the world until completion of  in 1935.
Titanic II is a planned ocean liner, to be built as a modern-day replica of the "Olympic"-class  .
 The new ship will have a gross tonnage (GT) of 56,000 while the original ship measured about 46,000 gross register tons (GRT).
 The project was announced by Australian millionaire Clive Palmer in April 2012, as the flagship of a proposed cruise company Blue Star Line Pty. Ltd. of Brisbane, Australia.
 The intended launch date was originally set in 2016, with the ship sailing from Southampton to New York within the same year.
 However, construction of the ship has been delayed to 2018.
 , construction is yet to commence.
The "Barbarossa" class was a class of ocean liners of North German Lloyd and the Hamburg America Line of the German Empire.
 Of the ten ships built between 1896 and 1902, six were built by AG Vulcan Stettin, three were built by Blohm & Voss, and one was built by Schichau-Werke; all were built in Germany.
 They averaged  gross register tons (GRT) and featured twin screw propellers driven by quadruple-expansion steam engines.
MS Princess of Tasmania was an Australian-built roll-on/roll-off passenger ship.
 She was built by the State Dockyard in Newcastle, New South Wales for the Australian National Line.
 Laid down on 15 November 1957, she was launched on 15 December 1958.
 As built, the ship had a tonnage value of  gross register tons (GRT) , was 113.32 m long, had a beam of 17.73 m , and a draught of 4.74 m .
 Two 9-cylinder Nydquist & Holm Polar M69TS diesels supplied 8600 hp to the propellers, allowing a maximum speed of 17.75 kn .
 Up to 334 passengers and 142 vehicles could be carried.
 "Princess of Tasmania" was given the IMO number: 5284986 .
 The ship was the first RO/RO passenger ship in the southern hemisphere, and at the time of launch, the largest vessel built in Australia.

Question: The largest ship in the "Imperator" class ocean liners had how many gross register tons?
Answer: 56,551