The National Museum of the Royal Navy has begun essential works to support the historic HMS Victory, with the 252-year-old vessel currently at risk of collapsing under its own weight.

The ship, which first set sail in 1765 and has been dry-docked in Portsmouth since 1922, is best known for its role as Lord Nelson's flagship at the Battle of Trafalgar in 1805. Open to the public as a visitor attraction since 1928, more than 30 million people have explored the Victory, which is also the oldest commissioned warship in the world.

Taking 18 months to complete, the £3m (US$3.8m, €3.3m) project is being carried managed by aerospace and defence company BAE Systems, who will create a better support system using a detailed laser scan of 89.25 billion measurements and computer modelling.

The new system has been designed to mimic how the ship would sit if it were floating in water. Replacing the existing steel “blades”, a new system of 15-foot adjustable steel props will be fitted over two levels. Each prop is telescopic – meaning it can change its length – and will feature a cell monitoring the 2,000 tonne weight load around the clock, which can be easily adjusted if necessary.

“Victory is possibly the most famous ship in the world. She remains a commissioned ship and the flagship of the First Sea Lord,” said Dominic Tweddle, director general of The National Museum of the Royal Navy.

“The dry dock, in which she sits, is also the oldest in the world, and this is the first time something like this has ever been done on a historic ship.

“We have been really tested with this scheme. Our priority is to stop the ship from moving, get her into a stable condition and then take the necessary steps to ensure the hull is here for another 250 years.”

Conservation work on HMS Victory started in 2011, when the masts and yards were removed to treat rot. Since then the ship’s hull has also been repainted, while the main cabins have also been refurbished. A new walkway for visitors was also installed enabling access to more of the ship, along with a new fire detection and fire suppression system.

The ship will remain open while works are carried out.