What happens in an implosion?

When a submarine hull collapses, it moves inward at about 1,500mph (2,414km/h) - that's 2,200ft (671m) per second, says Dave Corley, a former US nuclear submarine officer.

The time required for complete collapse is about one millisecond, or one thousandth of a second.

A human brain responds instinctually to a stimulus at about 25 milliseconds, Mr Corley says. Human rational response - from sensing to acting - is believed to be at best 150 milliseconds.

The air inside a sub has a fairly high concentration of hydrocarbon vapours.

When the hull collapses, the air auto-ignites and an explosion follows the initial rapid implosion, Mr Corley says.

Human bodies incinerate and are turned to ash and dust instantly.

Any investigation is sure to focus on the carbon fibre mid-section of the Titan sub.

The pressure vessels of deep vehicles like this are normally constructed from a robust metal such as titanium and are shaped in a sphere, to spread the immense pressure equally around the passenger compartment.

But to fit more people inside, the OceanGate sub adopted a cylindrical shape, with a carbon fibre tube inserted between to titanium end caps. Carbon fibre is very tough - they use it to build aeroplane wings and racing cars.

But did that immense pressure at depth - more than 300 times the atmosphere at the sea surface - play on the material to expose flaws in the original fabrication or to introduce and then worsen instabilities over repeated dives?

Any investigation would want to know about the practice non-destructive testing.

Aircraft are subjected to regular, very fine-scale inspections to ensure their materials are not developing cracks or that their layers are not starting to separate.

Photographing the Titan debris found on the ocean floor and bringing them back to the surface for study in a forensic lab may allow engineers to identify where on the sub structural integrity was lost, initiating the catastrophic implosion.

Until last year Prigozhin consistently denied mounting evidence that he controlled the group, launching lawsuits in British courts against Bellingcat journalist Elliot Higgins who accused him of running the private militia.

The deniable nature of his group's operations have made him popular with Mr Putin and allowed him to build up his own power base, over the last year coming to rival that of the military and security elite that rule Russia.KG娛樂城

A man at ease with violence, corruption and ambition - his rise is emblematic of the modern state built by President Vladimir Putin over the past 24 years.

But despite his increasing power, he has remained an outsider among Mr Putin's small inner circle of advisers, unafraid to criticise officials in Moscow he sees as corrupt, lazy or both.

And he has reserved a particular hatred for the head of the military, Valery Gerasimov, and the Defence Minister Sergei Shoigu - a fellow outsider - for years.

The attempt to seize Bakhmut - a small city with a pre-war population of around 70,000 people - is puzzling. Most observers believe that it has limited military significance and some say the campaign was designed by Prigozhin to allow him to claim credit for a victory amid the military's faltering campaign.

He regularly accused Mr Shoigu and Mr Gerasimov of "constantly trying to steal [credit for] Wagner's victory" in cities like Soledar, where thousands of paramilitary troops - often recruited from prisons - met their deaths.

And by contrast to his more bureaucratic rivals, Progozhin's often foul-mouthed rants made him a personality that often caught the attention of the world's media. Leaked documents suggested that the Russian defence ministry was unsure of how to combat his messaging and increasing popularity.