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My Father, O-5 USN, On The Zumwalt


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The Zumwalt-class DD was brought up in Mech's PLAN compendium thread. It reminded me that my father sent me an email a while back with his thoughts on the type; I found it to be a pretty interesting read:

  The DDG-1000 Zumwalt class of destroyers is very interesting, sometimes in a good way and sometimes in a bad way. The Navy terminated the class at only three ships based on cost per ship (~$3 billion each) but also based on perceived risk and a definite degree of mission mismatch (naval guns as the main armament). In this sense the Zumwalt class is clearly a failure (success looks like the DDG-51 Arleigh Burke class, where we are cranking them out at a steady rate off into the future and already have a whole bunch of them). However, it is the component technologies that make the Zumwalt class interesting in a good way:
  1. The ship is "all electric" in that there are no engines (gas turbines, steam turbines for nuclear, or diesels) directly driving the propellers via a reduction gear and shaft. Instead, main propulsion is provided via electric motors driving the propeller shafts using power taken from the main electric power bus. Thus, propulsion is just another electric power consumer that can be traded off against other electricity consumers (such as radars, weapon systems, etc.) all fed from a distributed network of gas turbine electric generators. There is literally nothing like this in the rest of the Navy, and I predict that this will be the biggest "feature" of the Zumwalt class and will be replicated over and over again in our future ship-class designs.
  2. The ship is fully networked, and all systems are on the net. (The CVN-78 Ford class aircraft carriers are also networked in this way.) This is both good and bad. Good because a fully networked system gets you great visibility and control of your systems. Bad, because "OMG, what if the Chinese sneak a military computer virus into our combat systems and it takes them down!" This concern has actually driven what is being called the Navy's "Cyber Awakening", where they are now starting to get their collective heads around this issue as a warfighting concern, not just a IT concern. In a close analogy to the Navy's "Sub Safe" program (where any component of a US Navy submarine has to be certified as being safe for submarine use), look for a US Navy "Cyber Safe" program coming to a warship near you in the near future.
  3. The ship has significantly reduced manning compared to other ships with similar capabilities (e.g. other destroyers). The DDG-1000 class has a crew complement of approximately 150 officers and men, compared to the DDG-51 class with a complement of nearly 300. This is huge, because the largest "cost" in the Navy is the cost of personnel, and therefore the Zumwalt should be significantly cheaper to man. (One the largest enablers of this reduced manning is the network capability mentioned above -- fewer folks needed in the engine room, etc.)
  4. The "Tumblehome" hull (where the hull slopes inward away from the water, rather than flaring outward as with other destroyers) is designed to provide significantly reduced radar cross-section, which should make the ship much harder to detect and track on radar. (Theoretically the DDG-1000 has the radar cross section of a small fishing boat.) However, reduced radar cross-section can be tricky to achieve and maintain (and how do you know in normal operations?), and the Tumblehome hull can cause significant problems with sea-keeping and stability -- 100 years ago, ships with this hull type routinely rolled over and sank because of this issue. The Navy claims that this problem has been dealt with and isn't an issue, but time and real-world operational experience will tell. I predict that this is a hull design that won't be repeated in future Navy ship designs, although there may be individual low-observable features that may make the leap to future designs.
  5. The two large guns (155 mm Advanced Gun System) as the ship's main armament. This is an advanced (but otherwise conventional, e.g. gunpowder) naval gun that can fire rocket-assisted, extended-range fin-glide precision-guided projectiles out to approximately 60 miles. However, it is hard to imagine that this has tremendous utility in today's Anti-Access/Area Denial (A2/AD) with regard to China, where stand-off needs to be measured in hundreds of miles. However, it will make a great naval gunfire support platform if Marines are ashore and the naval threat is low (admittedly a very limited-case operational scenario).
  6. Various other weapons system features, such as distributed Vertical Launch System (VLS) cells around the perimeter of the hull, the AN/SPY-3 radar (limited volume search capability, limiting it to a local air defense role), etc.
  7. Pre-planned "growth room" specifically for projected power-hungry future weapons, such as lasers and rail-guns.
So I predict that the Zumwalts will be excellent "experimental ships" and much of the technology will be proved out and rolled forward to a new ship class. However the ships themselves as they are currently configured will probably have limited utility compared to more general purpose Navy destroyers. Cheers,
     - Osa




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About the tumblehome, I remember someone who spent quite a while designing ships saying that it was great for reducing RCS except for the fact the things are in the sea, and thus pitching will sometimes cause the acute angle it sacrifices to achieve anyway and the wake the ship will throw has the potential to give a worse RCS underway than a more traditional hull. I believe he mentioned the Skjolds as a great example of a stealthy design that wasn't stealthy at all underway. They also have the problem that any steady leak from holing will cause a progressively faster sinking from the ship, rather than a traditional hull which will have its sinking slow as it gets lower because each progressive bit of the ship is bigger, and overall there's less reserve bouyancy.


The guns are a fantastic feature for winnning battles against the greatest foe the US faces, the USMC and their perfidious schemes to sabotage the US defense of their interests by insisting on the preservation of their fantasy of recreating Guadalcanal against a peer competitor in the modern day. This in a period where the role of force in international relations is basically as a regime veto card to deal with governments judged worse than the horrorshow of a smoking crater and a power vacuum, and any discussion of fighting with another power is in the sort of situation where the US is desperately short of the vital parts of any fight, like the ability to put ships and planes where they need to be. I am of course somewhat joking, but the point stands.


My general impression of the Zumwalts is they were a kind of crazy late Cold War plan for ships when we were if we want to put a positive light on things trying to do things that would break our economy but make the Soviets totally shift their behavior to cede land superiority in Europe or break their state trying to keep the status quo. They got everything. When the Cold War stopped they kind of became the equivalent of concept cars. They've got just about every idea the Navy thinks would be an improvement, and it's going to be interesting seeing what sticks.

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That too. I think there's a lot of good reasons why the Skjolds weren't very popular. It's a very expensive solution to a problem that could be better solved by more cheaper corvettes skulking in fjords. The Chinese approach is more like that, with enough ships to give good coverage without ridiculous speed and the low hanging fruit RCS reductions from superstructure shape without going all in on stealth at the expense of seakeeping and other useful traits.

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Quite. There's a real serious fight against the water to achieve serious stealth, there's a reason that when they built the Sea Shadow for stealth and only stealth it was a SWATH hull with seriously oblique angles between the hull and the water so it didn't get much wake and would be guaranteed not to make a reflective shape as well as having decent stability unlike a tumblehome design. The main problem is that SWATH is a pain to deal with the facilities for it, and those angles make the problems greater and compress the amount of room you get, and modern ships are in general volume-critical (roomy weapons, spaces for smart people to work them, and enough space that smart people won't just leave adds up, which is why modern warships are so underarmed looking compared to older ships).

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Yeah, then people blame the nerds going batty on the nuke training, and they can't jump overboard and try to swim for civilization because the room is too cramped. Jokes aside, the submarine is going to be the only really truly stealthy ship that is still potent in combat, since sensors work differently underwater. For all the rest, RCS reduction is just going to be another parameter the designers consider.

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