NATIONAL HARBOR: This is rocket science. As the US Navy tries to keep its crucial 1990-vintage Trident D5 nuclear-capable missile viable for decades to come, it’s working with everyone from the Royal Navy to the US Air Force to NASA to keep costs down and technology up to date. Meanwhile, the design team for the new nuclear missile submarine that will carry those Tridents after 2031 is already down in such low-tech weeds as salvaging launch tube doors from the existing Ohio-class nuclear subs as they retire from service.

“The issue with NASA [is] it takes 10 Trident missiles to make up one Space Shuttle booster,” in terms of the rockets’ relative size, explained Vice Adm. Terry Benedict, Navy director of Strategic Systems Programs, when I asked him about it after his remarks this morning at the massive Sea-Air-Space conference. “So when NASA dropped the Space Shuttle program [in 2011], the industrial base took a significant impact,” the admiral said. There’s no way the Navy’s much smaller demand for nuclear missile boosters can make up for the loss of Space Shuttle booster business.

Because the industry builds fewer missiles, each booster the Navy buys carries more overhead costs and a heftier price tag (though Benedict didn’t say how much). For now, said the admiral, “through a lot of concerted effort with industry we’ve been able to maintain costs at what I’ll call an acceptable level.”

In the longer run, however, the viability of the rocket booster industrial base and the affordability of the Navy’s nuclear missiles depends in large part on the decision NASA must make circa 2016 about how (or whether) to replace the shuttle. Benedict and his staff are “working closely” with NASA, but ultimately it’s not the Navy’s decision to make.

Meanwhile, while NASA wrestles with going to the Moon or Mars, Benedict’s busy just getting back from the UK. Just two weeks ago he was in London, consulting with the British on the Common Missile Compartment (CMC) that will hold the launch tubes for both the US Ohio replacement and the British Vanguard replacement. (The British also use the Trident). The Royal Navy’s nuclear submarine program is under heavy fiscal pressure and may be cut from four boats to three — not quite enough to keep one sub continuously at sea — but Benedict assured the audience at Sea-Air-Space that “there’d be no impact” on the US sub program if the UK buys one less missile compartment.

Then there’s the Air Force. Launching a missile from a silo in North Dakota is a lot easier than launching one from a submarine underwater, but once the missile is in the atmosphere, the technical challenges are the same. Benedict has personnel on all of the Air Force’s analysis-of-alternatives (AOA) teams for sustaining the ICBM force, and the two services have identified areas they can both buy the same components, from test range equipment to electronics hardened against the electromagnetic pulse (EMP) of a nuclear attack. (Obviously we never want to have to use that last one). The two services are already developing a common “fusing and firing circuit” for the updated Mark 5 warhead the Navy plans to build in 2019.

Meanwhile, Benedict’s counterpart for the sub itself, the Program Executive Officer (PEO) for submarines, is working on less apocalyptic issues like pumps and access doors. Last year, the service finalized general specifications such as length — 560 feet — and displacement — over 20,000 tons — but there are innumerable specifics yet to work out before production begins in 2021. That may seem like a lot of time, but every month counts in the marathon to replace the Ohios on sea patrol by 2031. That schedule will already require building the first Ohio Replacement in an unprecedented 84 months, less than historically required for submarines half the size, said Rear Adm. David Johnson, PEO-Submarines.

“We are looking at everything,” Johnson told reporters, “all the way down to trying to reuse the doors on the missile tube access covers from the Ohio” as those subs go out of service. “Those doors are dry” — i.e. they aren’t exposed to the ocean — “so they really see no wear,” he said.

It’s relatively easy to reuse missile tube parts because the tubes themselves are the same size on both the Ohios and the future missile sub, which will also carry the Trident for at least the first part of its service life. (An all-new nuclear missile is a notion for the distant future). But nobody’s building Ohios any more, so Johnson’s priority is taking advantage of the Navy’s ongoing Virginia­-class attack sub program.

The service is steadily buying two Virginia submarines a year to add to the 10 already in service. By contrast, the entire Ohio Replacement Program (formerly known as SSN(X)) will be 12 subs, so any way to piggyback off the higher-volume program will save money. Johnson wants to bundle procurement of at least some materials and components that will go on both submarines.

So how many components will the Virginia and the ORP have in common? There’s not even an estimate yet, Johnson said. “It’s not like ten percent, it’s not like 75%, it’s somewhere in the range there,” he said. But as the Navy and industry design the replacement for the Ohio-class, he said, with every component, “we see if we can make it fit using a Seawolf or Ohio or Virginia–class pump, valve,” etc.

But since the new nuclear missile submarine will be larger than anything now in service — the biggest submarine ever built in the US, said Johnson, roughly twice the size of the Virginia — a lot of its components will have to be bigger, too. Even with those scaled-up parts, though, the admiral said, the same factory can often build a big version and a little version of a given component, a pump for example, at a lower cost than two companies building entirely different designs.

Johnson has to squeeze out every dollar he can, because the Ohio replacement is a potential budget-buster, so much so that the Navy can’t fit it in its current shipbuilding budget without sacrificing almost everything else. (The service wants extra funding from the Defense Department on the grounds that nuclear deterrence is a national priority, not just a Navy one).

Setting aside research, development, and design, just building the first Ohio replacement will cost an estimated $6.8 billion. Just as with any other manufactured product, though, the cost per sub will drop over time. The Navy has orders to get the average cost of SSBN(X) 2 through 12 down to at least $5.6 billion, with a target of $4.9 billon. (All these figures are in 2010 dollars, since that’s the year the program’s Acquisition Decision Memorandum, the ADM, was issued).

Johnson currently estimates the design team’s already cut the cost by almost four percent, to $5.36 billion — but that’s still comparable to an aircraft carrier. So the submarine, like the missile it will carry, still has a long way to go.