Postby kham » Wed Jun 06, 2012 11:11 am
Managed to find this essay from several years ago; it remains valid, doubly so since this thing was originally killed, but its cheerleading team managed to resurrect it. Worse still, if a civilian mariner can figure out most of the points made regarding hull, powerplant, electronics you should expect professional naval officers should have too. Unless of course their advancement and rice bowls supercede reality, and the good of the Navy and the Nation are subordinate to that....
Read
Weep
STUART SLADE ON THE DDG-1000, AUGUST 2008:
At its simplest, nobody has any faith the ships will work; and if they do work, nobody quite knows what they will be working for.
DDG-1000 has been a screwed program right from the start. The people behind it broke every single rule of naval design and consciously did not discuss the ship or her basic theoretical precepts with anybody.
The ship was, you see, a break from the hidebound traditions of the past that tied the navy to obsolete ideas and prevented them from striding forward into the bright days of the future.
Those thirty words have doomed more naval programs than guns, torpedoes and missiles combined. Some of the hide-bound conservative ideas they discarded included floating, moving, shooting, steering etc.
The big problem was that they changed everything in one go. They wanted new weapons, new electronics, new machinery, new crew levels, new hull design. Everything was new, everything was a major break with past practice. Of course, it all ended in tears, there's no way it could have done anything else.
Examples. The ship is supposed to use a radical hull form to reduce its radar cross section. Great, only that hull form uses a wave-piercing bow and a tumblehome shape. Now, let’s look at this more closely. It’s a wave-piercing bow. That means it - uhhhh - pierces waves. In fact the water from the pierced wave floods over the deck, along the main deck, washes over the forward weaponry, hits the bridge and flows down the ship's side. Now, that water weighs quite a bit, several tens of tons in fact, and it is moving at the speed of the wave plus the speed of the ship.
That wave, when it hits the gun mount and bridge front is literally like driving into a brick wall at 60mph. The gun mount shield is made of fiberglass to reduce radar cross section. The wave also generates suction as it passes over the VLS system, sucks the doors open and floods the silos. The missiles don't like that. Spray is one thing (bad enough) but being immersed in several tons of water flowing down is quite another.
Then we have the problem of the water flowing over the deck. It is strong enough to sweep men off their feet. In fact, it’s so dangerous that ships that operate under such conditions have to use submarine rules - nobody on deck. But to work the ship, we need people on deck. Uhhh, problem here?
Now for tumblehome hull form. This means the ship's sides slope inwards from the waterline, not outwards like normal ships do. Now, we take a slice through the ship at the waterline. That's called the ship's waterplane. There's a thing called tons per inch immersion, the weight of water needed to sink the ship one inch. TPI is proportional to waterplane area. As the ship's waterplane area increases it requires more tons to make it sink an inch. As the waterplane decreases it requires fewer tons to make it sink per inch. Now, with a conventional flared hull, as the ship sinks in the water, its waterplane area increases, so it requires a steadily increasing rate of flooding to make the ship sink at a steady rate. If the rate of flooding does not increase, eventually the ship stops sinking. This cheers up the crew immensely.
However, with tumblehome, the waterplane area decreases as the ship sinks into the water. So, the ship will have a steadily-increasing rate of immersion at a steady rate of flooding. In short, for a steady rate of flooding, the ship sinks faster and faster. The ship will not stop sinking. This is immensely depressing.
The problem is the damage goes much further than that. As a ship with a conventional flared hull rolls, the increasing waterplane area gives her added buoyancy on the side that is submerging and gives her a moment that pushes upwards, back against the roll. That stabilizes her and she returns to an even keel. With a tumblehome hull, as the ship rolls, the decreasing waterplane area reduces buoyancy on the side that's going down, giving a moment that pushes downwards in the same direction as a roll. This destabilizes her so she rolls faster and faster until she goes over.
Having dealt with the hull design, we now move to the machinery. The DDG-1000 is supposed to have minimally-manned machinery spaces. This will save manpower etc. etc. etc. There's a problem, all of that automation doesn't work. It’s troublesome, unreliable, extremely expensive and it needs somebody to watch it and make sure it does it's job. In fact, its useless. It gets worse. The purpose of a crew on a warship is not to make it go around and do things. Its to try and patch the holes and put out the fires when other warships do things to it. Repairing damage cannot be automated (did I tell you that DDG-1000 was supposed to have automated damage control systems? Ah, forgot that but it doesn't matter, they didn't work either.) So, having designed a hull that sinks if somebody looks at it crosswise, we now remove the people who were supposed to try and stop it sinking.
Now we come to the electronics. Great idea here. Put all the antennas into a single structure and we can cut RCS. That causes a problem called electronic interference. The systems all shut each other down. And they did. Very efficiently. The radar suite on DDG-1000 was the world's first self-jamming missile system. Oh, they took down the comms and gunnery fire control as well.
Did I also mention that the flow noise from the wave-piercing bow was enough to prevent the sonar working? That was an easy problem to solve. Remove the sonar. Anyway easy way to solve the interference problems, use multi-functional antennas. That sounds good. One day, when they get them working, I'll let you know. MFAs are pretty good when used in their place, but NOT for operating mutually incompatible systems.
The gun. Ah yes, the gun. It fires shells, 155mm ones. Guided shells whose electronics can withstand 40,000G. The acceleration in the gun barrel is 100,000G. Oops. Problems.
Then we come to the missiles. They're in new silos, all along the deck edge. Can anybody see the problems with that? Like moment and rolling inertia? The designers couldn't, which proves they know slightly less about the maritime environment than the deer currently eating the bushes outside my office window.
Now, all these problems are occurring at once and the fact that everything in the ship is new means that one can't be fixed until the rest are.
And that is why DDG-1000 got cancelled.
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NOTE: Later in the summer of 2008, the Navy reversed course a second time and decided to construct three DDG-1000s, assuring that the program would survive even if truncated at just three hulls.
