1) ship is moving head on to these 100 foot waves (brown pants for me) .... is it safe for cargo ships or warships to move at an angle also, or its always head on or tail on for such sea states?
100 ft waves are very rare. For commercial shipping, WNA (Winter North Atlantic) is the ginger weather with significant wave heights upto 30m (UK, Iceland, Greenland, Nova Scotia gap). Yes, ships operate in those weathers, with a loading line designated for that. Broaching/Quartering seas are okay for today's large cargo ships and shouldn't be too much of a bother (size matters) . In a storm, you will always turn into the waves . Following seas are among the most dangerous in heavy weather, with.
2) if due to freak conditions the distance between successive peaks is less than ships length , is there a danger both ends could float up and the trough below the middle could break or crack the ships back? or are ships designed for such bending loads ? I read that CVNs sailing like this flex upto 3 feet up and down in the middle....
No way. The ships are always built to a registrar's (ABS, LLoyds, Bureau Veritas ) guidelines and certified or it will not be insured. Those guidelines cater to all the kinds of conditions you talk about in the code.
3) can smaller corvettes, FFGs tackle such sea states and still operate ?
Of course yes, and not just militray, even fishing boats and trawlers. They take a big beating and undergo far more violent motions than a large cargo ship of course.
4) does such sea and rain conditions degrade the radars, ASMs, decoys(aerosol clouds/chaff) and SAMs?
Radars No. Rest I dont know.
6) I read in alistair mclean novels of rescues being helped by ships dumping diesel layer into the area to 'calm the waves' - is that legit?
No way. Waves are due to wind action (given a large enough "fetch", ), putting diesel on surface does nothing to waves. Yeah, the only thing it might do is to lighten a ship.
7) can the kind of enclosed automated deployment fibreglass n inflatuble lifeboats most ships have nowadays (seen in captain philips movie) survive in these conditions?
Yes. All life boats by SOLAS code have to be able to survive such conditions and areself righting as well . Even if they turn turtle, they will right themselves. They also have rations and emergency supplies and radios, batteries and even some of them have facility to catch rain water.
8) should the ship apply full power to ride these head on or throttle back?
Head on waves, you will make heavy way, so will take more power than usual. Following sea, you better ease up ,the motions in the rear will be violent (including instantaneous loss of stability, consider case, when ship speed is exactly same as wave speed and the ship is suspended in time with crests at the bows and stern and trough amidships , the ship will capsize) with screws coming out of the water or sections of prop clearing the water and slamming back in (shock loading of that guaranteed to break the screws and the associated shafts).
9) if the engine fails for any reason and the ship starts wallowing , will a 5000t ship survive this?
Probably. You really want to keep the bows pointed into the waves in such conditions.
10) to attempt a basket rescue in these conditions would a Dhruv manage or you want a bigger meatier EC725/Sh60/Merlin for it?
Range & Payload you need a big dedicated maritime helicopter with auto hover on a certain height. Impossible to hold station and hover manually in those kind of conditions. You want to fly a long distance, grab everyone and fly back.
11) are oil tankers filled with lighter than water oil and strong compartmentalization + double hull literally unsinkable? I mean they could ride low in the water but will not go down.
Yes, but that is true of most large cargo ships of any kind. Traditionally because of inherent safety, oil tankers were single hulled. What made oil tankers double bottom hull was pollution due to oil leakage if it gets holed for any reason (think Exxon Valdez) . So regulations mandated double bottom (and sides as well) for that. However, that LOWERS stability compared to the single hull design of old.
12) do we get such conditions in arabian sea or bay of bengal?
Probably in a super cyclone kind of thing that hit Orissa long ago. As a general rule , No.
Also watched the clip you posted. It doesn't seem like a normal sized cargo ship of today, but rather an ocean going service vessel /tug/tender of some sort. Even for that, the bow gets dunked underwater only twice. So not really the big enchilada. That big enchilada is when a 80,000 DWT bulk cargo carrier or a container ship having waves breaking over it's forecastle in regular intervals. That is when things are pretty rough.
Now most conventional ships with a flared bow will be built with a shear as well (basically, the side view will show a rising line from midships to the stem)so that the ship has good sea keeping. With a bow piercer like the Zumwalt, riding these kinds of storms will be a miserable and nasty experience, very analogous to a submarine trying to ride the waves , which a submarine will never do of course, it will take in ballast and submerge and ride out the weather with nary a problem underwater.