Alternative Propulsions For Australia's Future Submarines?

Pete Comment

My opinion is that the AUKUS submarine project will only survive (and make sense) if Australia actually uses the pressurised water reactors (PWRs) developed by the UK https://en.wikipedia.org/wiki/Rolls-Royce_PWR  

or US https://en.wikipedia.org/wiki/List_of_United_States_Naval_reactors#Submarine_reactors    

A major requirement of Australia nuclear subs will be their ability to inter-operate with UK and US nuclear subs. This includes the ability to move at a sustained speed of 30 knots and preferably faster.

Australia is in no position, and without the industrial base, to develop radically new types of alternative propulsion sources for submarine that are discussed below.

I therefore support Plan A which is already Australian AUKUS policy https://en.wikipedia.org/wiki/AUKUS#Nuclear-powered_submarines ie. choosing a UK or US attack submarine (SSN). The AUKUS SSN may have many UK and US characteristics.

As Submarine Matters is an equal opportunity website other Plans for alternative propulsion systems are being given “airtime” below:

ARTICLE

"How to Fall Forward, Not Back

[Plan A]

If Australia is to not stuff-up its program to acquire nuclear propelled submarines, the best path is that first spelled out [in October 2021] on this site https://gentleseas.blogspot.com/2021/10/strangely-sober-sermon-aukus-ssn.html ; i.e. begin early, by funding the RAN to wet lease Astute boats with RN crews, then spend the next ten years gradually replacing RN and other UK staff seconded to Australia with newly qualified Australian crew members and technicians as local capacities mature. 

As such a (potentially pear shaped) project like the nascent Australian SSN program is wide open to foreign or domestic financial, political or organizational attack - and the Collins class won’t last forever - there has to be a plan 'B' and preferably a plan 'C' to. 

To survive a perceived failure of plan 'A'; plans 'B' and 'C' should not resemble a warmed over, shrunken and re-scheduled version of whatever plan 'A' the government of the day first announces. 

A Possible Plan 'B' ? 

One 'fall-forward' alternative to [Plan A] the 7,000 tonne Astute LMA [ie. the Lockheed Martin Astute (LMA) for Australia. This would have Lockheed Martin’s integrating the AN/BYG-1 (or follow-on) combat system] , mooted on Submarine Matters last year, would be a 4,000 tonne hybrid LIB/nuclear boat that eschews the perennial PWR as a power source, in favour of modular micro-reactors driving, say, free-piston Stirling [AIP] engines paired with linear alternators. 

The so-called 'disruptive' technology, noted, above was pioneered not for the US Navy, but for NASA. 

In the 1980s, NASA began investing in innovative means of powering space missions that travel beyond the distance where solar cells are a viable power source. The US Idaho National Laboratory and its partner institutions, such as the Los Alamos National Laboratory, designed and tested engineering development devices under projects:

-  KRUSTY https://www.energy.gov/nnsa/articles/krusty-project-demonstrates-potential-power-sources-future-space-exploration

- Kilopower https://www.nasa.gov/directorates/spacetech/kilopower  

- and, most recently, Fission Surface Power (FSP) https://www.nasa.gov/mission_pages/tdm/fission-surface-power/index.html  .

* the devices built and stress-tested under each of these nuclear projects (for which NASA was the customer) all eschew traditional nuclear fuel-assemblies (so no fuel pellets and no zirconium); instead using solid uranium cores and non traditional cooling and power take-off systems (so no system-critical pumps, no water and no steam raising equipment).

One early engineering development was a solid nuclear core the size of a toilet roll (their description, not mine!) that provided the heat source for a Stirling-cycle generator delivering (low watts) for use on NASA interplanetary missions. 

The next technological maturity step for NASA was to fund a reactor project (Kilopower), which saw the same U.S. government agencies create and test a 1 KWe generator designed to withstand space flight, including the shock of being literally blasted off a launch pad. 

NASA's current FSP project (see above) is intended to deliver a power source for use on the moon or on Mars with a space launch date 'in the late 2020s'. 

On pages 3 and 5 of the relevant public RFP (see Request for Proposal - Fission Surface Power) prospective respondents are informed that the power source NASA needs (to keep on boldly going. . . ) must deliver 'not less than 10 KWe', run autonomously for not less than ten years and weigh less than 3.6 tonnes. 

On page 10 of the RFP, respondents are invKWeited to detail any devices they believe they can produce for NASA that generate up to 40 KWe, so long as such devices meet all the other essential design criteria. 

There are powerful, very persuasive commercial and professional interests that stand to lose heavily if anything other than a PWR ever goes to sea on a submarine. 

Therefore, if NASA had not invested the time, money, technical effort and reputation in its (Lunar and Martian) nuclear power generation systems, I'd be among the committed skeptics to any PWR alternative. 

But NASA did so, so I am not (yet) sceptical. 

From Nuclear Science to System Delivery 

Meanwhile, back on earth, one of the pioneering manufacturers of nuclear propulsion systems for U.S. submarines, Westinghouse, is currently 'aggressively' (again, this is not my word) developing modular micro-reactors 'for civil and military uses' rated at up to 5 MWe ; i.e. an order of magnitude more powerful than the nuclear power generation systems of interest to NASA. 

NB: The advertised power rating of the planned Westinghouse micro reactor seems to be about 20 per cent higher than the MTU4000 series diesel alternators that were likely to have equipped the 4,000 tonne Shortfin Barracuda 1A design. 

Therefore, two 5 MWe Westinghouse micro reactors appear sized to handle the entire battery recharging needs of a 4K LIB/nuclear boat, thereby reducing its indiscretion ratio to (?) zero and extending its submerged endurance to conventional SSN levels, rather than conventional AIP levels. 

The Westinghouse modular micro-reactor design appears to have little in common with the large number of PWRs Westinghouse previously supplied to the US Navy (eg. unlike the Westinghouse S6W submarine reactor https://en.wikipedia.org/wiki/S6W_reactor , it uses no water and produces no steam) but seems, (to this non-nuclear non-engineer) eerily similar to the innovative nuclear powered alternator designs NASA has sponsored. Westinghouse is reportedly seeking NRC authority to sell its micro-reactors to customers in 2025. 

The art work accompanying journal articles about Westinghouse's modular micro-reactors seems to show that the modules comfortably fit into a U.S. standard (8 x 8 x 20 foot) shipping container. If their compactness is an actual fact, then the complete reactor module is a cylindrical unit about 2 meters in diameter and 6 metres in length (eg. see page 27 of Nuclear Plant Journal, March-April 2019). 

Under the hypothetical plan 'B'; the work initiated by NASA and, it does seem to appear, built on by Westinghouse just might open two alternative technical pathways for submarine nuclear propulsion.

The first pathway would be to use, say, four FSP-model 40 KWe nuclear powered alternators per Australian LIB/nuclear boat to cover the submarine's full hotel load and use traditional diesel alternators to charge the submarine's batteries for everything else. 

Such a boat could be tasked, say, with sitting on the bottom of the Gulf of Tonkin for two months or so listening, looking, recharging, 'interrogating' and 're-briefing' XLUUVs, before returning to base for crew changes, re-storing etc. The mooted submarine's batteries could be kept at, or near, their full charge indefinitely by relying on a small trickle flow to the battery from the 160 KWe nuclear generation plant. 

While this technical pathway transforms the submarine's endurance and time on station, it does little or nothing to increase either its rate of advance (i.e. deployment speed) or its top underwater speed, since the nuclear plant cannot generate energy at a rate near that at which battery power is consumed by the submarine when it is underway. An un-modified Collins class boat would presumably outperform this style of hybrid LIB/nuclear boat, both for rate of advance and sustained underwater speed. 

The second pathway would be to use, say, three Westinghouse 5 MWe modular reactors per boat to generate a combined 15 MWe to simultaneously cover (a) the submarine's full hotel load; (b) the power needed for propulsion at sustained speeds up to 10 knots; and (c) continuous battery re-charging. 

This technical pathway both transforms the submarine's endurance and time on station, matches or betters the rate of advance of a Collins class boat and gives the submarine commander the option of using a fully charged LIB in ways outside of normal parameters (i.e. to meet or exceed SSN top speeds over short distances, but not an SSNs sustained rate of advance). 

Why would you not 'just go for a pure SSN'? - because repairing or replacing an SSN reactor can only be done in a tiny number of secure dry-docks and it reportedly takes hundreds of highly skilled workers between weeks (K15 reactors) and years (PWR2 reactors https://en.wikipedia.org/wiki/Rolls-Royce_PWR#PWR2  ) to do so. If designed for easy removal (like the gas turbines on a destroyer) a sealed modular reactor of the size and shape Westinghouse (or NASA) describe could be done by a crane in a day - an important advantage over PWR propulsion.

BUREAUCRATUS LEX JANUARY 26, 2022