Navy Adopts Hybrid-Electric Amphibious Assault Ships

Navy Adopts Hybrid-Electric Amphibious Assault Ships

The U.S. Navy is incorporating fuel-efficient hybrid-electric propulsion technology onto several of its next-generation big-deck amphibious assault ships, the service’s top civilian said.

The USS America (LHA-6) and the USS Tripoli (LHA-7) are part of what the Navy calls its now-in-development America-class amphibious assault ships designed with, among other things, a larger deck space to increase the ability to transport and utilized air assets, Navy Secretary Ray Mabus told an audience May 21 at the 2013 Energy Efficiency Global Forum, Washington, D.C. The ships are being engineered with a hybrid-drive propulsion system, meaning the ships can use diesel-electric propulsion as well as gas-turbine engines.

When asked about the service’s broader initiative to power ships and planes with alternative fuels, known as the “Great Green Fleet,” Mabus emphasized that “now is the time to do it.” The effort has drawn criticism from lawmakers such as Sen. Tom Coburn, R-Okla., who say it’s not worth the added cost.

Hybrid-electric propulsion systems use a gas turbine engine as well as an electric motor and diesel generator. The electric motors can help propel the ship at speeds up to around 12 knots and the generator can help produce electricity for the ship. When it comes to traveling at speeds greater than 12 knots or so, the ship can then rely upon its gas-turbine engine.  At the same time, the generators can provide on-board power for many of the ships systems such as sensors, weapons and other electronics, Navy officials indicated.

The hybrid-drive allows the ship to propel itself using either electric drives or a traditional gas turbine engine.  Electric propulsion and on-board electrical power generation are both integrated through what’s called a main reduction gear (MRG), a portion of the ship’s propulsion system which helps convert energy into the revolutions needed for the propellers to move the ship through the water, according to Navy officials.

“This unique auxiliary propulsion system (APS) is designed with fuel efficiency in mind. The APS uses two induction-type auxiliary propulsion motors (APM) powered from the ship’s electrical grid instead of using main propulsion engines to power the ship’s shaft. Instead of using its gas turbines which are less efficient at lower speeds, the ship will be able to use its APS for roughly 75 percent of the time the ship is underway,” a Navy official said.

Mabus cited the successful deployment of the USS Makin Island (LHD-8), a 40,000-ton Wasp-class big deck amphibious assault ship able to transport as many as 3,000 sailors and Marines along with massive amounts of equipment, air assets and a Marine Expeditionary Unit (MEU). The Makin Island, commissioned in 2009 and based at Naval Home Port, San Diego, uses a hybrid-electric propulsion system, Mabus explained. As a result, the ship can operate on much less fuel compared to previous ship models of its kind using traditional steam propulsion.

In fact, during its maiden deployment last year, the Makin Island’s hybrid propulsion system helped contribute to as much as $15 million in fuel-cost savings over the course of the excursion, Mabus told the audience.

One analyst said hybrid-electric propulsion technology shows great promise for ships in terms of both propulsion and on-board electrical systems.

“This technology is really coming along with things like the Prius and ground vehicles. We’ve had decades of work of hybrids and now we’re seeing the potential to exploit it to where it is really applicable at the ship level,” said Daniel Goure, vice president of the Lexington Institute,  a Virginia-based think tank.

The on-board power advantage could be substantial when it comes to powering up ship systems such as computer technologies, sensors and weapons such as high-energy lasers, Goure added.

Mabus discussed the Navy’s plans to develop more hybrid-electric propulsion in the context of a broader strategic discussion about the importance of projecting and sustaining Naval power while maximizing energy-efficiency and lowering costs wherever possible.

“The vast majority of power in the Navy comes from fossil fuels. Because we purchase our fuel on the open market, the price of oil has had a dramatic effect on our budget. Every time the price of oil goes up more than a dollar a barrel, it cost the Navy and the Marines S30 million of dollars in additional fuel costs,” Mabus said.

In fact, for fiscal year 2011–2012, the Navy wound up with roughly $1 billion in unfunded fuel costs, he added.

Reducing fuel costs are also a substantial part of the Navy’s “Great Green Fleet” initiative wherein an entire USS Nimitz Carrier group, including both ships and air assets, were successfully powered by a 50–50 blend of biofuels and traditional fuel during last-year’s Rim of the Pacific (RIMPAC) international maritime exercise, Mabus explained

“The ships and aircraft were operating as part of RIMPAC. The 2012 demo was for nearly two days wherein the ships and aircraft operated on biofuels. The intent was to have them sailing on the biofuels – demonstrating a 50–50 blend. Prior to demonstrating great green fleet, we had tested this capability.  This was an opportunity to showcase on a large scale that it was possible to use our existing ships and planes with biofuels,” said Capt. Pamela Kunze, spokeswoman for Navy secretary.

Kunze also explained that the biofuels in development needed to be “drop in” fuels that could work with existing ship or aircraft engines.

However, some critics and lawmakers in Congress have questioned the utility of the Navy’s “Great Green Fleet” initiative on the grounds that alternative fuel sources create vast expenditures in a time of needed fiscal constraint.  Also, Lexington’s Goure added to the chorus of criticisms regarding biofuels, saying the high expense was not likely to pay dividends in the future.

Overall, being able to substantially reduce fuel cost will better enable the Navy to perform missions, maintain a forward presence and achieve its tactical and strategic objectives in an increasingly challenging global environment, Mabus added.

“Being there means presence. Presence matters. When North Korea threatens a missile launch, our ships with missile defense technology are there. When Marines in Afghanistan need air support, Marine pilots from ground based units and pilots from our carriers are there. When the earthquake struck Haiti in 2010 and the tsunami struck Japan in 2011, we had Navy ships helping within hours because they were already there,” Mabus told the crowd.

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When SECNAV states the “generators store electricity”, it is either time to replace him, or his staff. A rifleman in the foxhole knows the difference between a generator and a battery. Sailors are smarter then that. The sailor’s boss ought to really be smarter than that. Fielding a more efficient fleet is an awesome goal and should be pursued, but spending precious defense dollars on ‘Biofuel development’ is nuts.

Spot on CC:
the whole biofuel scam is nothing more than a back door subsidy to biofuel producers. I would be real interested who the main suppliers are, and trace their rep’s on K st & who they & their employee’s made contributions to in the last election, not my area of expert. but I thought I read that biofuels are 1.35 x the cost of the normal fuels used, correct me If I’m wrong, in this era of reduced budgets, its a disgrace to the brave sailors of our Navy! KC OUT!

Jesus.….…just use nuclear reactors.…..Then Guess what? Its a 199,999% more fuel efficient.

So, it’s just a CODLAG arrangement then? It’s always good to see more efficient drivetrains used, but CODLAG isn’t anything revolutionary. And comparing it to a ground hybrid is hilarious, as there isn’t a effective way to use regenerative braking at sea. And those APMs are more commonly known as azipods, although using those terms would show how it actually isn’t some huge breakthrough. With fuel costs on the rise, they really should be reviewing the nuclear fleet ideas of old.

http://​www​.opensecrets​.org/​l​o​b​b​y​/​i​n​d​e​x​.​php is a pretty good site to track this stuff down, as it collates all the available public data on lobbyists and contributions. You’d still have to find the contractors involved, but this will tell you what those contractors did in terms of lobbying. And in the US, it is true that corn-based ethanol Biofuel is about 30% more expensive.

Funny u should say that, I worked on 688 & 726 subs. Early in the nuclear navy That was ADM Rickovers dream.….… but my god the cost of producing a all nuc powered Navy 100 trillion?

Fuel cost will drop by 35% once u get of this “green navy” madness, see my previos post about the cost of biofuels!

Talk about “back to the future”! The post WW-I battlecruisers that became the WW-II vintage Lexington-class carriers had steam-electric drives. Saved the weight and complexity of the reduction gears. NOW, we think its all sorts of innovative.… . . Read your history, folks!

Nah. Plus a lot of work is being done on making reactors smaller and more affordable. It pays for itself in the end anyways. Less worries about fuel, etc.

When it comes to ships this large why not just go with proven tech like nuke that will not cost billions in fuel over the life of the ship.

Have no problems with electric propulsion. Just have a huge problem with the way it’s being described here. They want to use biodiesel for fuel. Presently it costs to much to produce over fossil fuels. Farmers that grew acres of corn for food now grow a different type to make biodiesel. The federal government pays the farmers subsidies to grow biodiesel corn. This corn is cheaper to grow. The farmer gets a bump from that, the feds and then at the refinery. Other crops are used, like switch grass, but the type of refinery needed for these crops are few and expensive to build. If the farmer is not located within 80 miles of the refinery they can’t grow it for this use.

How about doing this. Use nuclear power to drive steam turbine generators. They then power Azipods , an electric powered propeller pod that is omnidirectional and powerful. Already in use pulling and pushing ships bigger than the Nimitz class.

It’s GREEN power . It just glows brighter.

Yes, and every twenty five years the ship is out of commission for refuelling. It’s a good opportunity to gut and upgrade the ship, but a poorly timed war would leave you an LHD/LPD/LHA short.

Someone needs to do the calculations regarding space and mass consumed by a nuke+steam vs diesel+gas turbine+bunkerage.

Learn something new every day. From the Wik’; until I find more.

“Turbo-electric transmission had been chosen for the battlecruisers and was retained when they were converted into aircraft carriers because American companies struggled to produce the very large geared turbines necessary for such big ships. One advantage of turbo-electric drive were that the substitution of flexible electric cables for bulky steam-lines, which allowed the motors to be mounted further to the stern of the ship; this reduced vibration and weight by shortening the propeller shafts. Another was the ability to go astern at full power without needing a separate reverse turbine to do so, simply by reversing the electrical polarity of the motors. Two more benefits were the facility to operate all four propellers even if one of the turbo generators failed, which eliminated loss of speed due to the drag of a non-rotating propeller, and the possibility of operating only some of the generators at low speed with suitably higher loading and greater efficiency. “[Turbo-electric drive] was efficient, rugged and always reliable. But it was also heavy, intricate, and not easy to maintain and keep tuned up.” It posed the danger of high voltage to the crew. The machinery also required special ventilation measures to dissipate heat and to keep out any salt air. Even with this and elaborate insulation measures, protection from moisture or from flooding due to battle damage or other causes remained problematic.

Each propeller was 14 feet 9 inches (4.50 m) in diameter and each of the four propeller shafts was powered by two 22,500-shaft-horsepower (16,800 kW) electric motors acting in tandem. These motors were about five times the size of any earlier electric motor. Four General Electric turbo generators powered each propeller shaft and each was rated at 35,200 kilowatts (47,200 hp), 5000 volts and 4620 amps of direct current (DC). Each of the four AC alternators produced 40,000 KVA [blight_: kilovolt*amps?]. Sixteen water-tube boilers, each in their own individual compartment, provided steam for the generators at a working pressure of 295 psi (2,034 kPa; 21 kgf/cm2) and a temperature of 460 °F (238 °C). The turbo-electric machinery of the Lexington-class ships was designed to produce a total of 180,000 shaft horsepower (130,000 kW) and propel the ships at 33.25 knots (61.58 km/h; 38.26 mph), but each ship reached over 202,000 shp (151,000 kW) and 34.5 knots (63.9 km/h; 39.7 mph) in sea trials in 1928. Six 750-kilowatt (1,010 hp) DC turbo generators were installed in the upper levels of the two main turbine compartments.

Sources cited by the Wik’:
Anderson, Richard M.; Baker, Arthur D. III (1977). “CV-2 Lex and CV-3 Sara”. Warship International (Toledo, OH: International Naval Research Organization) XIV (4): 291–328. ISSN 0043–0374.
Breyer, Siegfried (1974). Battleships and Battle Cruisers 1905–1970 (Reprint of the 1973 ed.). Garden City, New York: Doubleday & Co. OCLC 613091012.

I guess if anyone has these books on tap…

I think that was the author that said generators store electricity, not SECNAV. I know, I saw it too, I feel your pain. For the biofuel argument, you also have to look at another important factor — reducing dependance on Foreign Oil. The problem is that there is currently no one perfect solution for fixing our energy dilema. Hybrid Electric, LNG Propulsion, Biofuels, Fuel Cells, or otherwise. However, I think we should give the newer/smaller nuclear plants more consideration. Especially given increasingly stringent MARPOL exhaust emissions requirements.

For the folks going on about nuclear power, here’s a pertinent blurb on the America-class and nukes:

Of course, the practical question remains: is there a space savings, or a space loss? You still need to carry fuel for your complement of aircraft.

Canadian fuel is still cheaper and easier for us to get, until California’s Monterey shale kicks online.

Corn industry applauds Obama-corn subsidies (joking, corn subsidies for ethanol predate Obama, and farm subsidies for corn itself predate ethanol too).

Nuclear decay to heat water to steam Turbine to MRG to driveshaft to turn propellor
—————————————————————–MRG to Alternator to Electricity to do fun stuff

Classic turbo electric is steam turbine directly to alternator, generate power and what you want with it. Electric motor for your propulsion? Check. Radar? Check.

“Hybrid drive”

Bunkerage to Gas turbine to MRG to driveshaft to turn propellor
—————————————MRG to alternator to electricity to do fun stuff
Bunkerage to Diesel to MRG to driveshaft to turn propellor
——————————-MRG to alternator to electricity to do fun stuff
Large Battery Bank (Li-Ion? Nickel Metal Hydride? Lead Acid?)->electric motor->turn propellor
Large Battery Bank (Li-Ion? Nickel Metal Hydride? Lead Acid?)->Battery->do fun stuff

There’s pros and cons with the MRG vs simply generating electrical power and in turn powering an electric motor. If your electrical power system fails, but you still have the powerplant, you can still use mechanical energy for propulsion. I’m guessing this is what happened on the USS South Dakota, which famously lost electrical power, but was still able to leave the battlefield. Of course, if you have backup generators for electricity, you can still power your electric motors for propulsion and run.

I guess the con for going old school and using the MRG is the longer propeller shaft, or trying to work around shifting the location of your turbines closer to stern to reduce shaft length.

I guess if you are trying to sell CODLAG as “green”…

Much would depend on the type of ship, whether or not it requires the Prarie Masker system (compressed air pumped through orifices in propellor for sonic stealth). If it doesn’t, then a hubless direct rim driven ducted propulsor simplifies much (E-Boat’s RimJet is a good example) by incorporating a water cooled electric motor within the rim of the hubless propellor, the blades connected at the rim rather than to a center hub. That eliminates a lot of shafting, gearing, seals, large hull penetration, etc. Larger slower ships might do well with podded propulsion systyems.

That would be just “Prairie” because “Masker” is a different system that is hull mounted as opposed to being through the shaft and propeller as Prairie is.

Thanks for not letting that slip by. I was apparently typing faster than I was thinking.

Fuel costs can be better addressed by using the COTS technology for conversion of natural gas directly to diesel in the gas fields and pipelined to the refineries in the existing crude pipelines, no LNG. The USN (DOD) would be better served by investing in our national natural gas conversion than in the corn industry. The USN is well experienced in consuming ethanol in it’s more preferred forms and would be better off not being involved in some politicians dreams of grandeur. By the way, our politicians are preparing the way for their fraternity brothers to start shipping our national natural gas out of the country to maintain our national natural gas prices (profits).

We always have a chunk of the fleet docked for maintenance anyways. I don’t think it’s possible to have the entire 300 ship fleet in the water at the same time.

Playing devils advocate to the majority of comments — if we’re paying more for fuel oil but the payments are going back into the US economy rather than to Canada (love you Canada), Latin America, Africa, and the Persian Gulf (can’t forget those guys), wouldn’t the additional cost be worth it? I gues it depends on ensuring biofuel is cultivated in the US, but I still think its a valid consideration.

Theoretically, since the US gov can just squeeze the money back into its coffers with taxes anyways.

That said, we Americans are fond of chasing the cheapest dollar, even if means our jobs, dollars and sense leave the country, never to return.

The reasons for electric propulsion on the Lex and Sara are a bit different than the reasons today. If you but look at the electrical power demands for a FEL or a railgun you might see a logic. For example, what if the propulsion power source was momentarily / intermittently switched to weapons, or simply if any excess capacity was used to “trickle charge” a big bank of capacitors! It makes perfect sense.

With dual propulsion CODAG, you could use both simultaneously for extra electrical power.

“Hey we need more power, kick in the diesels!”

If this thing cant keep up with the Fleet Carriers The consept is a big waste of time and money.

We don’t have the facilities to do an all nuke navy and maintain it. Constructing that along with all the litigation headaches would erase any savings.

This argument about reducing dependence on foreign oil is BS. The fracking that is going on that will lead to just that by the end of the next decade is happening all on private and state land. If Obama’s admin was truly concerned about secure fuel sources they would open federal lands to exploration. The Green navy is a back door pay off to cronies in the bio fuel industry and nothing more.

Per blight’s link above, from page 2 of the CBO nuke report:

“Similarly, a fleet of nuclear LH(X) amphibious assault ships would become cost-effective if oil prices grew at a real annual rate of 1.7 percent, implying a price of $140 per barrel of oil in 2040—about the same price that was reached in 2008 but not sustained for any length of time.”

Well, that’s a relief! No worries about oil ever getting THAT expensive again over the next 27 years, especially in a hypothetical time of crisis!

Sarcasm aside, the issue isn’t really the aviation fuel — Gator Navy folks feel free to contradict me, but I expect an LH(X) group wouldn’t have to put up a lot of sorties during a transit to a hot spot. The issue is with the escorts. The flexibility of movement one gets from a nuclear-electric LHN only goes so far, unless they also build some DDN escorts. The Admiral’s staff would still need to worry about tankers and UNREP for fast transits to a combat zone, even if the LHN didn’t need it.

Fantastic read, although it only seems to take into account a narrow band of reactor designs. I see no mention of the currently commercially available Heavy water types, or of the in development thorium based Gen IV reactors. Other than that, it’s a great paper.

Any thought towards the stealth attributes of the power source? Heat trails, hydrocarbon leakage? Some sources leave a bigger footprint that details a bit about the source. Go Nuke, it’s cleaner and there when you need it.

You’d need pretty sensitive equipment to detect hydrocarbon emissions in the air above noise, let alone being able to triangulate a ship based on it.

Infrared suppression is a topic that hasn’t been talked of much. I suppose if the PLAN gets a bunch of high-loiter, high-altitude UAVs with IRST, they could indeed track the movements of the Navy before getting shot out of the sky. Nuke or conventional, both should be pretty visible…

From a logistical standpoint, roughly ten to twenty percent of the carrier force is undergoing a long refuel cycle; thus a nuclear force needs to be stood up by an extra 10–20 percent. Nukes are already expensive ships, and having to buy more of them compounds things. Of course, it’s possible that nuclear cruisers and destroyers would be easier to refuel, or you would scrap at 20 yrs old on the first refuel cycle?

The price of natural gas has fallen pretty sharply, to the point that they just burn it off at Bakken because it can’t be transported without losing money.

Additional exploration isn’t the problem — and the claims to the contrary are hardly fact based. There are millions of acres that have been open to exploration for oil companies for many years, but have remained unexplored by anyone.

Hence — that issue made for good political theater — but was never good for anything else beyond that.

On the comment about not being able to have a 300 ship navy in the water at one time.

First. The Navy must have 300 ships in commission. Then they need sailors, not contractors, on board to operate, maintain and repair systems. Then add a chain of command that gives a darn about ship, crew, mission, morale .

In the 1980’s the US Navy had over 500 ships in commission. With 95% mission ready. Sailors complained but when something broke WE fixed it not some contractor. When GQ sounded, whether a drill or for real, stations were manned and combat ready within the time set by navy requlations.

But thanks to the computer and video game. Add in political correctness and the Navy has become as effective as a ship in the Afghanistan Navy. Sarcasm intended.

I was on cv66 and went to the christening of the new USS America LHA6 it was a great experience to have steeped foot on both ships. New and old. A tradition carried on.

To both KrazyCol, & Jcross…YES, “corn-based ethanol biofuels” ARE a SCAM, of Big Ag, and the “Corn Belt”…what the media does NOT want you to know, is that cutting edge work on algae-based biofuels is VERY rapidly progressing…Now, Hmmm, *WHO* *MIGHT* be best positioned to *grow* algae for biofuel production…???…it’s all the innovative “little guys”, those “environmental types”, who grew up, and got to work…Yes, there will be some big up-front investments needed, but the promise will come true, sooner of later…The reality *IS*, *YES*, we CAN GROW our way out of fossil-fuel dependence, but not with *corn*…
There are also many land-based crops, such as hemp, that are also waiting for “BigOil” to get it’s head out of our asses and wallets…Why is America the ONLY major industrialized country that does NOT grow hemp…???…(Ans: BigOilGreed & Stoopidity.…)

What you do is let the ocean run the ship with hydroelectric generators. All the tech for this is already in use. The ship would suck in water which it already does for cooling and distillation of water for ship use. This water sucked in would run through hydro generators to create electricity then the ship would run on the electricity. Water tanks for storage can be added to start the ship while in port to bring it out to sea.

Great idea, Dennis…have you seen the Army’s prototype dirt-powered tanks, or the Air Force’s wind turbine aircraft?…no in-box thought for YOU, huh, Dennis!…

…ALL fossil fuels are dying investments…guess we’ll have to wait for Rand Paul as POTUS in 2016…

Let’s put wind turbines on top of the ships, and use the wind to power our ships.

Don’t let the Barbary pirates catch you becalmed, arr!

All of you completely miss the point or are completely ingnorant to the realities of national security. Secretary Mabus, other Navy officials and DOD are pushing for energy independence, not simply biofuels. Energy efficiancy (which this story is about, not biofuels) and alternative sources of fuel (this includes fracking, sand oils, off-shore drilling, biofuels and any other source that deminishes our reliance on middle eastern sources) will help keep those brave Navy Sailors that you talk about safe because once we achieve fuel independence for us and our allies, it will be our foes that will have to deal with issues in the middle east.

I would say there’s more engineering knowledge and political savvy in these remarks than in the entire DoD. Let ‘em try what they’e interested in. NavSea has a way of getting to sound engineering in spite of politics.


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