A problem in its own right, of course, as we saw with Columbia.

The entire function of engineering is to create designs that don’t come apart under the loads they will face. Designs where the flexing is within the proper margins to meet the loads.

It ain’t always easy. Most of my recent designs have not had wings.

My biggest worry with spacecraft is that allowing any kind of flex will give reentry forces enough leverage to rip the thing apart. You are our local spacecraft expert, so you know more about this than I do, though. This reasonable caution or paranoia I’m experiencing here?

Some materials more than others.

I watch the wings of airliners flex outside my window when I fly. They can go up and down a couple of feet. Doesn’t bother me. It’s built into the design.

The Space Shuttle wings flex like any other aircraft’s. The pressure vessel in the nose that protects the crew expands and contracts when there’s pressure across the walls.

The Shuttle’s external propellant tank expands and shrinks as fuel is loaded and drained. Bellows on propellant feed lines accommodate the movement.

Look at the ignition sequence in the “Riding the Boosters” video below. Look at how the entire structure moves under the loads.

Come to think of it – What are the flex limits for subs?

They were always pale and pimply from spending all their time below, and when on duty, they were always sweaty and covered with grease. Because of the nature of their work around hot greasy machinery, out of sight where most of us couldn’t see them, they were allowed to wear dirty and stained clothes, and oily t-shirts. Whenever they did come up on deck they kind of wandered about bumping into things and blinded at the bright lights.

When they did get time off, they were all fresh air fiends, spending hours at the rail in all kinds of weather, chain-smoking and looking at the water. When the ship was attacked by a plague of crab lice after one our trips to the fleshpots of Yokosuka, the guys in M division and their sketchy hygiene practices were the first to be blamed.

War ships are also highly compartmentalized into watertight spaces, not only to provide reserve buoyancy when partially flooded, but so the decks and bulkheads help provide structural support. they’re designed, for obvious reasons, to absorb enormous amounts of battle damage.

As for torque flexing of prop shafts, I would imagine that special “twistable” alloys were used in that application so the shafts would not be too brittle and snap under strain.

Did you check out this video on your link?

You want flexing, try aerospace structures. Yipes.

I talked to a machinist once who told me the propeller shafts on an aircraft carrier were 3′ in diameter and hollow. He said from end to end, they twist almost a full revolution at full load. I tried to verify that on the web but just got more anecdotes.

But I did find a video of ER in his youth.

The modern destroyer evolved from an earlier type of ship called the ‘torpedo boat destroyer’.

The invention of the steam turbine (as opposed to reciprocating piston engines) about the turn of the 20th century made compact, high speed vessels possible. The invention of the guided torpedo about the same time also made it possible for fast, maneuverable torpedo boats to threaten even the biggest battleships. Suddenly, guns and armor were not all that counted, and cheap, expendable fast torpedo boats could devastate a fleet of battlewagons, as the Japanese Imperial Navy demonstrated at Tsushima in 1905.

The response to the torpedo boat was the torpedo boat destroyer, a small, unarmored, fast ship which could keep up with torpedo boats, but overwhelm them with heavier guns. Torpedo boat destroyers could also carry torpedoes, so they also became a threat to battleships and cruisers, and the large ships now routinely were escorted by them.

Eventually, the term was shortened to “destroyer”, and the class evolved into other roles: scout, picket, escort, cruiser, shore bombardment, antisubmarine work, anti-aircraft platform, and all-around utility work. The destroyer played the role the frigate did during the days of sail, a ship too small to engage a ship-of-the-line, or fight in “the line”, but suitable for just about everything else.

Today, the battleship has disappeared and the cruiser is quickly going the same way (big targets, too expensive to lose). Even the torpedo boat has become a coastal raider with little blue water capability. Destroyers have evolved into all those missions, and are now undergoing specialization themselves. Modern destroyers are the size of WWII light cruisers.

Today, ther are basically three kinds of combatant ships: carriers, destroyers, and submarines.

When a formation goes from, say, “line ahead” to “bent line screen”, the signal flags go up to alert the squadron to the upcoming maneuver, and when the flagship pulls them down, the signal executes. For the next few minutes, its all assholes and elbows and ships are rushing about all over the place, flags flying, in a seemingly chaotic, but carefully planned and choreographed confusion. (If somebody screws up there is usually a collision!). When its all over, the ships simultaneously fall into their new formation, often at some new course and speed. Its a pretty awesome sight from the bridge of a destroyer, and it does make you feel all tingly and proud to be even a small part of it.

Its usually preceded by an ominous call over the 1MC “Now stand by for heavy rolls. All hands clear the weather decks while maneuvering at speed.” In this case, according to a reader comment, the side was manned by sailors to dress up the ship and impress civilians riding on the carrier alongside. My skipper would never have done that, its dangerous, you might lose someone over the side. Even below, you have to brace yourself to get around during a turn like that, and loose gear is flying around all over the place.

As for the “flex” question, I don’t know enough about ship construction to properly answer you. I do know that on my ship (which was approximately of the same size, mission and performance as the USS Gonzalez in this video), the main deck had an 8 inch neoprene spacer or “hinge” running athwartships at the beam which allowed the main deck plates to flex without buckling in a heavy sea. Whether there were arrangements like this all throughout the hull and superstructure, I don’t recall.