Probably tap undersea cables than bust them - which a fishing trawler could do with more deniability. Regardless, prototype Nuclear espionage sub, all officer crew of 25, 7 of the dead were Captain 1st Rank (right under admiral), 2 recipients of the Hero of the Russian Federation. My interest is certainly piqued.

Obviously there is lots of speculation since the Russians are tight lipped about the whole incident.

Some of the most speculative (but with little to no support) seem to think they were carrying a cobalt nuke larger than the Tsar Bomba.

There was also a mention that the sub is of an unusual design - a set of spheres rather than a conventional cigar shape.

I think that was based on graphics of how the interior is constructed. The sub in question should be a cigar shape: https://en.wikipedia.org/wiki/Russian_submarine_Losharik

Not sure if when the knowledge about it's design was made public, but name Losharik gave everyone a hint. It is a cartoon character that's made from spheres/balls connected with a wire. This is a logical way to create a submarine that's intended to go very deep, spheres are the best shape to handle high pressures. So logical conclusion based on the name was that internally it's based around connected spheres.

Submarine itself looks cigar shape, but that is just her outer shell, it's pretty certain that outer shell is not pressure sealed but rather that internal spheres withstand the pressure while the just the shell around it.

I believe the name is from a cartoon character, who is made out of balls:

https://www.youtube.com/watch?v=1F_hX-QjDQw

A better diagram of the sub here: https://cdn.arstechnica.net/wp-content/uploads/2019/07/Ru_Lo...

basically a series of interconnected bathyspheres with a hydrodynamic shell over them.

So basically personnel can't access the reactor and engine compartments from the life support units, the sub has to surface. Here's a bigger version of the same diagram with readable text:

http://www.hisutton.com/images/Ru_Losharik_Cutaway.jpg

Skegs, hydraulic manipulator, no weapons. It's clearly ment to tamper with undersea cables.

Are any of these details more than speculation? I had the impression that the best information was some not-so-clear pictures which happened to catch it on the surface, plus the admission a few days ago that it is in fact nuclear powered, and had a suspiciously high-ranking crew.

I agree that tampering with cables seems like the obvious reason for the military to go super-deep. With recovering sunken things made by your adversary a close second. And in the mid-1980s, they were much better at titanium than at video cameras.

I don't buy it that an all officer crew wasn't able to don rebreathers in time.

Fire drill is like a number 1 drill in the fleet, and a submariner, moreover a captain should be able to do it with his eyes closed

Growing up in an Eastern Eu country (former communism), nobody there underestimates the professionalism of soviet military. They are many, but not brilliant - see MH17 and so on.

Please expand, it is unclear from your words do you think they are professional or not. And what exactly should we see with MH17?

I'm not comfortable sharing details because they can be traced back to specific people and events, but I've seen people doing highly-skilled high-demand tasks under alcohol influence "to calm their nerves".

MH17 was shut down because the radar operator could not read his screen / correlate with other sources of information regarding civilian flights. Can tell you a bit about how professional those operators were.

I think it was pretty obvious what they meant.

An old friend of mine has recently finished his term in the Russian military. According to his words explaining his own experience, and things he heard during military exercises from guys from other parts of the country, most soldiers are being trained not to defend their country, but to do three things: paint walls, wash their clothes, and clean up the premises.

It's no wonder you can mistake a passenger airplane for a military aircraft after such a stimulating experience.

Russia still has military draft. Gotta do something with all that free labour. They do however also have actual professional soldiers, and lots of them. Those should be more trained / competent.

Considering that Americans who shot down Iran Air Flight 655 were given medals, shooting down a passenger plane is quite an achievement for a well-trained Navy.

https://en.wikipedia.org/wiki/Iran_Air_Flight_655#Post-tour_...

Making a major diplomatic incident to get $10 or $50 million? Using two subs that cost hundreds of millions to build?

Seems more like fantasy than speculation.