Here is a question for you, the reader.
A new class of manned submarine will be a future "SSE". That means it will be an all electrical battery operated submarine with no on-board charging. Instead charging may occur at a wharf or from some other vessel, maybe a conventional or nuclear mothersub. Or perhaps charging by a mothership or boat with a diesel engine.
Would an SSE be viable?
For what kind of missions?
Regards Pete
7 comments:
Pete I think the answer is “No” for any kind of fleet submarine, but maybe “Yes” for a short-range submarine that could operate from a mother ship. But I think the most likely option is Diesel Electric.
The key question is energy density. In transport nuclear fuel has by far the highest energy density - several orders of magnitude higher than diesel or any other fuel. Hence SSNs can avoid refuelling for 30 years. Diesel fuel is the next best option. Petrol or hydrogen have lower effective energy density than diesel since diesel engines are more efficient. Even the best batteries have less than a tenth the energy density of diesel, which is why the average electric car is at least a half tonne heavier than the equivalent sized petrol or diesel car. This is why we have no prospect of long range electric planes.
Energy density in MJ/kg are:
Uranium. 3900000
Diesel. 45
Coal. 24
Lithium Ion battery 0.39
So roughly uranium is 100,000 times more efficient than diesel, which is 100 times more efficient than our current best batteries. Perhaps in a few more decades we will have batteries ten times as efficient, in which case a hybrid diesel electric submarine gets more feasible.
Pete
Different topic but I was a bit perturbed in the budget coverage last night to find no mention of the submarine project. It looks suspiciously like they are stalling the project.
The new SA Labor government claimed today there was nothign in the budget for Adeladie submarine construction.
https://indaily.com.au/news/2022/03/30/sa-labor-sounds-budget-alarm-over-subs-but-gst-is-ok/
I think that is a slight exaggeration but close to the truth. From my reading there is funding to close out the end of the French contract and presumably for staff in the SSN study group. There is also a (sensible) allocation to form an SSN division of ANSTO. But I can find no allowance for forward funding of SSN purchase or construction. More concerning, I can find no budget allowance for any of the critical preliminary works needed before local SSN construction can begin. These include:
- expand ARPANSA to provide safety and regulatory regime for operating RAN SSNs
- upgrade ASC Osborne to nuclear engineering standard to permit SSN construction as per RN or USN standards
Construction can’t start before these steps are completed, so despite the claims of urgency, I see no sign of prompt funding.
I thought they were planning a “Khaki election” but it looks like the “cash splash” has taken its place. I hope somebody tells China.
Hi Pete
Obvious for unmanned sub drones , as a sensor and a submerged weapon platform (Torpedoes but also Anti ship or Anti Aircraft/missiles). The progress in batteries but as important in inertial navigationsystem (specially for short duration of a few days),and in networks (such as L16 and subsequent) makes this development problably in the works
Less obvious for a manned system due to the absence of backup,the marginal value of a manned system vs significant costs for many missions and the "political" value of loosing a drone
I think that in a decade or two, the idea is more viable, and as others have said it is great for unmanned or very short range missions.
There is no reason for it, in my opinion. As stated above, uranium is far more efficient, and innovation can make reactors and drives smaller and quieter. Also, an all electric has just one power source, underwater that can be a terminal issue. SSNs have a diesel backup and some battery too, SSs can power on batteries.
I agree with the comments of Kelley and the other Anonymous. I will add a bit further on what I do think is possible in the next few decades. Personal opinion only, based on physics, not knowledge of naval research.
All electric is NOT likely to be a power option for a large submarine (SSE?) capable of a long range voyage and carrying any significant weapons load (torpedos or missiles). So if Australia needs to send a submarine to the South China Sea, it won't be electric. Even if Singapore wants to send a submarine to the South China Sea, it won't be electric.
Electric power will be useful for smaller short-range minisubs and drones able to undertake specific missions. Unless the range of these missions are only a couple of hundred KMs, these drones/minisubs will still be launched from a diesel (SSK) or nuclear (SSN) "mother-boat".
So continuing our Australian example, if the RAN sends an SSK or SSN to the South China Sea, it may stop 200km short of its target, and deploy electric drones or mini-subs to complete its mission.
If the role of submarines switches from being a carrier of a weapon/sensor package into a combat zone to safely transporting drones and mini-subs carrying weapons and sensors into a combat zone, the preference for SSNs over SSKs will actually increase. The SSN will have far more power for recharging drones and minisubs.
Smaller coastal submarines (modern successors to the German Type 23) that only operate from land into adjacent coastal waters (e.g. Germany into Baltic/North Sea, Vietnam or Philipines into South China Sea) could be electric. This would have many advantages, but mission duration will only be 10 to 20 days max.
Hi Anonymouses and Kelley
Thanks for your comments.
I would say that the current energy density of even quite advanced batteries falls far too short compared to subs with batteries used in combination with higher density diesel fuel or Uranium.
However, advanced batteries are energy density sufficient for unmanned craft that have intelligence collection (UUV or AUV) or weapons (torpdoes or mobile smart mines) mission loads. But insufficient for mission loads + crew + life support (especially safety).
Safety insufficiency includes:
- over reliance on battery only with no alternate fuel backup (eg. running diesels or AIP).
and
- very likely inability to allow a crew to escape (say) at 22 knots for 2 hours (ie. 44nm at speed) but then with no alternate energy source to operate the submarine and no way to recharge the batteries.
Maybe in the 2030s batteries may have 20 times more energy density than currently. With 2030s batteries being safe to use and manage.
Two issues that all-battery advocates are looking at are:
- the total cost of the propulsion for battery only subs compared with diesel-electric subs and nuclear subs
and
- How much of a submarine's total weight and size/space needs to be for propulsion. Maybe a quarter of a diesel-electric sub's weight is for propulsion?. But maybe half a nuclear sub's weight and size (including diameter to fit in a "tall" reactor) is for propulsion?
Regards Pete
Hi Anonymous [at Mar 30, 2022, 9:24:00 PM]
Yes, looking at the Government's Budget Speech https://ministers.treasury.gov.au/ministers/josh-frydenberg-2018/speeches/budget-speech-2022-23
there's nothing specific about the submarine project. This is even though the Government made a detailed Cash Splash Announcement of $10 Billion spending mainly for an East Coast Nuclear Submarine Base - see https://gentleseas.blogspot.com/2022/03/media-release-australia-to-build.html
Or was that an ILLEGITIMATE Government Announcement given that the Government was meant to be waiting for the Nuclear-Powered Submarine Taskforce's REPORT in April 2023 or later https://www.defence.gov.au/about/taskforces/nuclear-powered-submarine-task-force
Is the Government Cash Splashing BEFORE it can legitimately talk about spending $Billions on the subs and all the backup infrastruture and nuclear safety regulatory framework required?
Is the Government buying "East Coast Base" votes in Port Kembla OR Newcastle
OR Brisbane (Dutton's Dickson Electorate being in Brisbane https://en.wikipedia.org/wiki/Division_of_Dickson#Members )
But the hard graft of long term submarine program planning is ignored because it falls after the 21st May Election campaign.
China's new (cruise missile or bomber?) bases in the Solomons may be a little close to any base in Brisbane...
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