Launch HN: Maritime Fusion (YC W25) – Fusion Reactors for Ships
266 comments
·February 26, 2025FiatLuxDave
Greybeard former fusion founder here. Wishing you guys all the luck in the world! Email in profile in case you wish to chat.
For all the naysayers, as a fusion startup, targeting the marine market is a good move. They aren't even the first fusion startup to do so; IIRC Rostoker's group got their first major funding from the NRL. The marine market pays a premium for not having to refuel, and historically emerging energy technologies have early commercialization in ships. This was true for fission in the 50s and for photovoltaic solar in the 70s/80s.
Now, sure, they have to make power to be able to sell it. But to build a reactor, you have to raise funds, and in order to raise funds you have to show that you can make money if you are successful at making power. Explicitly aiming at a market that might actually pay for overpriced power shows their investors that there may be a valid business case. That doesn't make fusion happen any easier, but you don't make any reactions without first building a reactor.
You know, I'm sure these guys could work somewhere getting paid to get more people to click on stuff. Instead they are taking a risk to do something that might be important. Make no mistake: fusion founder is a tough gig. There is no established off-ramp, and many fusion founders find that it's a job that can easily eat your career. I hope their plan B is in order, as well as their prenups and/or wills. They are going off to fight a dragon that's eaten a lot of other people's careers, relationships and sanity.
As an aside, it's nice to see someone working on a tokamak actually not being overly optimistic about wall heat flux. It's like somebody actually paid attention to Stacey or something ;)
jtcohen
Thank you very much !!! Really appreciate this :)
nocoiner
Can you elaborate on the use of photovoltaics in shipping? After a few searches, I haven’t been able to find anything that suggests the marine industry was an important sector for its development.
Also, I feel extremely confident predicting that the commercial maritime industry will never ever pay a premium for a particular fuel source. There may eventually be some applications where fusion is most efficient, but fusion reactors aren’t going to make their debut in cargo ships.
defrost
I suspect they're referring to the use of PV cells in lighthouses, Light-Buoys, Wireless Relay Stations, LORAN (pre GPS marine navigation) stations, etc.
Economics at the time restricted their limited use to mountainous areas, deserts, isolated areas, remote island outcrops, etc.
I saw PV use in the 1970s in remote Austalian rail operations to power signal boxes and repeaters .. the higher costs offset the equally high costs of maintaining a fueled generator in a remote location.
Marine shipping wasn't, to the best of my recollection, directly using PV's shipboard as they already had massive engines driving propulsion and it was trivial to bled off a little torque for a electrical generator.
nradov
Sailboat owners were early adopters of photovoltaics in order to avoid having to run generators. Some newer merchant ships have installed photovoltaics to supply part of the hotel load and maybe save a tiny amount of fuel, but that's a newer development and probably more of a "greenwashing" thing.
defrost
Addendum:
I should have addressed this in my peer comment, from the Launch HN header above
Why ships? They don’t have great alternatives—the shipping industry is desperate to decarbonize. Hydrogen and ammonia are being explored, but come with serious downsides: low energy density, flammability, leaks, and massive infrastructure challenges.
DNV GL welcomes Lindanger to fleet – world’s first methanol fuelled ocean-going vessel (2016)
“We are very pleased to see the completion and launch of this exciting and innovative newbuilding,” says Knut Ørbeck-Nilssen, CEO at DNV GL – Maritime.
“This is the first time a dual-fuel engine with a Low Flashpoint Liquid (LFL) fuel system has been installed on an ocean-going vessel and it is a testament to the excellent cooperation between all the project partners that we have been able to complete this unique project and gain flag state approval. Methanol as a marine fuel is a very promising option to enable owners to reduce the environmental impact of their vessels and to comply with low sulphur and ECA regulations and we look forward to working on many more projects using this innovative marine fuel and technology.”
Methanol as fuel heads for the mainstream in shipping (2023) - https://www.dnv.com/expert-story/maritime-impact/Methanol-as...
Also - https://www.methanol.org/marine-fuel/ and https://www.methanex.com/about-methanol/marine-fuel/
algo_trader
Here is latest (2025) bio methanol project from China [1], at $150/barrel of oil equivalent
And its not even true e-methanol which will be $200-$300boe
[1] https://mp.weixin.qq.com/s/Va0XYtSXQJLVrOZsW5obXA
(if u have any actual contact with the maritime industry would love to connect and chat)
dredmorbius
PV energy capability per unit surface area is low enough that it's impractical for large-scale propulsion.
Marine PV has seen use on pleasure craft (particularly sailboats) for auxiliary power needs (electronics, nav, lighting, pumps, light cooking/heating), and for drone craft (there was a startup out of Alameda, CA, producing what seemed to be aimed as US Naval marine survey craft a few years ago, largely wind-powered but with electronics and back-up propulsion powered by solar arrays, see: <https://newatlas.com/marine/72-ft-autonomous-saildrone-map-s...>.
Wind-capture remains the most viable alternative to fuel-based marine transport, and "windjammers" remained in commercial operation through the 1950s particularly on very-long-haul routes, though ultimately even that niche was captured by oil-powered propulsion. See: <https://omeka2.hrvh.org/exhibits/show/a-new-age-of-sail/last...>.
Containerisation probably accelerated and/or solidified that decline as this permitted not only far more efficient loading and unloading, but requires clear decks and permits vastly larger ships and concommitantly greater crew efficiencies (crewing is almost entirely independent of ship size and capacity, so a larger and faster ship (factors which also trend together given hull speed and its relationship to length) is virtually always vastly more efficient than a smaller one, despite possibly greater total fuel consumption. Fuel use itself per unit cargo is also lower for larger shipping.
Current ship-size constraints are largely determined by harbour and canal dimensions (hence ship dimensions defined by <location>max, e.g., Panamax, Suezmax, Chinamax, Batimax (Baltic Sea, not Baltimore Harbour), etc. I'm fond of the designation "Handy Size", which calls to mind "fun sized" though I'm told there's little relation. Maximum length capable of sustaining large seas (waves) without keel breakage is another marine engineering consideration which has limited ships to ~1,200 ft / 660m maximum length. At larger sizes ships are simply too susceptible to coming apart in heavy conditions.
Ships in general are constrained by the smallest viable dimensions of a port of call or route, and larger ships have fewer viable available ports or routes, though the busiest of such tend also to favour larger hull dimensions.
mrweasel
> I'm sure these guys could work somewhere getting paid to get more people to click on stuff.
That, right there, that is what makes me go: You know what, go for it. Best of luck, go make something, go try something.
You're absolutely right. So much talent is wasted on getting people to click an ad, stay on a page just a few minutes longer, watch the next video. So much time, so much money thrown into the dumpster fire of social media, ad tech and stupid "but as-a-service" solutions. It's better for everyone if the funds are directed towards something that might actually make the world a better place.
justsid
Not just that, but fusion will never happen if no one tries their hands on it because everyone says it can’t be done.
DrNosferatu
No naysayer here, just curious:
- What does this bring to the table beyond marine fission power?
- Why do they think they can make it cheaper than military fission marine power?
nradov
There is at least the possibility that fusion power could eventually be viable for privately owned civilian merchant ships. Fission power is a non-starter in that market due to concerns (valid or not) over security, terrorism, proliferation, and meltdowns. Even if someone builds a new fission powered merchant ship it would be useless because many nations wouldn't allow it to enter their ports.
Military fission power plants were never optimized for cost. They have always been hand built in tiny numbers with a focus on safety, durability, and maximal output.
pclmulqdq
Aren't the products of fusion equally radioactive? I get that we all have the idea of helium being the main product, but don't you get a lot of tritium out of the process? It's not quite proliferation, but it's not non-radioactive either.
moffkalast
Their plain hinges on having net positive fusion in the first place, something that still remains a fantasy even in the largest reactors on land. I think those questions already take so much good faith that you couldn't possibly be a naysayer.
uranium
"Downtime for maintenance is part of normal operations, making this a far more forgiving early application of fusion, unlike the grid where every down hour is lost revenue."
Planned maintenance, sure, but unplanned maintenance means the same lost revenue, plus you're stuck floating in the middle of the pacific ocean, possibly in need of parts or debugging expertise that only exists half a planet away or, for that matter, food. It's certainly a good idea to find a niche to make market entry easier, but I would guess that reliability requirements are actually higher for ships than for microgrids. Find some isolated town or island running off flaky diesel generators on shipped-in fuel and negotiate a reasonable SLA.
This ignores, of course, the bigger problem: making fusion work at all at Q > 1. If it were me, I'd work on solving that before worrying too much about optimizing market entry. So far every single fusion effort has failed to clear that hurdle, and any effort on the other parts is wasted if you can't actually make power.
jimbru
The first ocean-going steamships still had sails - it took many years for steam power to fully displace sail. Presumably a new maritime power system, like fusion, would follow a similar pattern.
https://en.wikipedia.org/wiki/Steamboat#Sea-_and_Ocean-going
simpaticoder
There is something very compelling about a fusion-powered ship also having sails.
usrusr
Let's be realistic, it would have a diesel engine as a plan B.
But if you like sails: my pet hypothetical technology is wind-driven hydrogen tankers (or tankers for some other e-fuel derived from hydrogen) that sail out empty, then cruise around wherever there is plenty of wind. They'd have a turbine/generator setup driven by the water passing by and use the energy harvested there for filling the tank. Cruise around as long as it takes to nearly fill the tank then return to port (and fill the rest on the way back). There's a lot of oceans where systems like that could cruise around on. (same concept could also be used for desalonation, there it would not only be about energy but also about avoiding local brine concentrations)
throwawaymaths
sails on modern cargo ships is a thing (see pyxis ocean)
gpm
So your approach to fusion is "the same CFS but stay at roughly the size of the SPARC prototype instead of scaling up"?
When you say "Q > 1 within a few (say 3) years" are you talking about your own reactors, or others? For that matter, are you trying to partner with CFS and license their technology or are you intending on starting "from scratch" (from whatever is publicly available)?
If that timeline is for fusion in general, what do you think your timeline looks like? Assuming adequate access to funding how soon can you build a Q>1 reactor? How soon after that can you actually go to market and sell a reactor?
---
On an unrelated note, I'm curious what you think of the current approaches to commercial fusion being attempted. Are Tokamaks the only game in town in your mind? Or do the various other approaches also being tried out right now have a good shot (MIF/Zpinches/etc)? Any particular approaches you think are particularly likely to succeed.
This being ycombinator and a startup I'm obligated to say that I don't ask this question because I think it impacts your commercial viability much, the greatest risks in fusion definitely aren't the competitors. I ask it just because I'm curious what people willing to start a fusion company think of the competitors.
---
Ships make a ton of sense to me as an early market. An 11 figure market (according to my own napkin calculations awhile back) where power is much more expensive than on land. At the same time it's never struck me that the hardest part of building a fusion company is finding a market.
jtcohen
Our device is larger than SPARC (~3m major radius) and less power (100MW fusion), hence the confidence in being able to solve the steady-state (repeated inductive pulses) engineering challenges.
We won’t be the first to Q>1, I’m super excited for SPARC to achieve that and will be prepared with champagne.
We’re targeting early 2030’s for our reactor, we’re going straight for the full thing no sub scale reactor in between (we do have a plan for milestone-ing it out in a meaningful way)
I’ve worked on a few alternative approaches earlier in my career (FRC at Princeton, dense plasma focus at LPP Fusion) … I think all fusion approaches are worth looking at, but I’m placing my chips on the tokamak. If I were to pick a runner up, the stellerator.
jaronchong
I'm just going to put this here. Someone please make this a reality.
### *"Tokamak Sailor"* (To the tune of "Drunken Sailor")
*(Verse 1)* What shall we do with a tokamak sailor? What shall we do with a tokamak sailor? What shall we do with a tokamak sailor? Early in the mornin'!
*(Chorus)* *Ho, ho! Fire up the plasma!* *Ho, ho! Fire up the plasma!* *Ho, ho! Fire up the plasma!* *Fusion in the mornin'!*
*(Verse 2)* Raise the coils and heat up the torus! Raise the coils and heat up the torus! Raise the coils and heat up the torus! Early in the mornin'!
(Chorus repeats)
*(Verse 3)* Confine the plasma, don't let it scatter! Confine the plasma, don't let it scatter! Confine the plasma, don’t let it scatter! Early in the mornin'!
(Chorus repeats)
*(Verse 4)* Sail with the power of fusion glory! Sail with the power of fusion glory! Sail with the power of fusion glory! Early in the mornin'!
(Final Chorus, extra loud!) *Ho, ho! Fire up the plasma!* *Ho, ho! Fire up the plasma!* *Ho, ho! Fire up the plasma!* *Fusion in the mornin'!*
Now all aboard the reactor ship, lads! Keep that plasma hot, and may the tides be ever in our favor!
Terr_
Im·a·gine a ship that puts to sea
It pow·ers it·self with elec·tri·ci·ty
The a·toms knit more than they split
Oh glow, my fu·sion core, glow (hooh!)
Soon may the break·through flare
To make our prod·uct not va·por·ware
One day, when the bas·ics are done
We'll make our IPOviggity
Suno could do this, even with a reference melody :)
jtcohen
Lol - on it
tim333
Re Q>1, isn't that just the reaction making more power as heat than you put in and you need something like Q>5 to use the heat to make steam to make electricity to run the thing? (as in wikipedia https://en.wikipedia.org/wiki/Fusion_energy_gain_factor)
echoangle
How much design on an actual reactor can you do already if the whole technology isn't even demonstrated yet? How many changes are you prepared to do based on the results of the current scientific reactors?
jtcohen
We can get pretty far along! From magnetic system design, vacuum vessel, RF heating system, cryogenic system, tritium fueling, etc we can start making a ton of progress today. The main things we still need to learn that can influence the design is advanced divertor scenarios and what are best material choices for plasma facing components (PFC's).
echoangle
How certain is it that a tokamak is even able to be run in a stable manner? What if it turns out that a stellarator would be better? Or is that already validated by now?
lukan
The stellarator design makes more sense to me as well and speaking of it, those guys will build a stellarator on land:
https://www.proximafusion.com/press-news/proxima-fusion-and-...
Problems are still many, though (Paper:)
https://www.sciencedirect.com/science/article/pii/S092037962...
null
DrNosferatu
This feels a bit like launching a startup that offers services based on fully working quantum computing, depending on others to provide their fully working quantum computer.
Terr_
Or a startup based on using cryogenic hibernation chambers on ships to provide shift-changes, or ultra-low-cost travel... after someone else finishes inventing them.
loanedempathy
Thank you for putting it this way.
I watched people scam VCs with drone tech, and Theranos, and other things.
Can people please do any amount of critical thinking around this sort of stuff? It steals funding from serious efforts and pollutes the pool.
What is special in this approach compared to literal decades in the field?
What is special about these young dudes compared to better-funded ventures that haven't pulled it off yet and who have been working on it longer?
What is the difference between "yeah we can do design work look at all this stuff (that's the easy 60-80% of the problem space)" versus "we can actually solve the remaining work that's got everybody so screwed up"?
This feels like a scam y'all, knowingly or not.
artemonster
Seriously, why people are falling on this scam??
phtrivier
> and we believe we’ll witness Q > 1 within a few (say 3) years. That’s huge.
I think it fits squarely in the "requires extraordinary evidence" bucket - what makes you so bold ?
Also, what's you intermediate plans between :
2025 -> Post on HN
2028 -> Q>1 achieved (by you ? by someone else ?)
???? -> ????
20xx -> a ship goes to sea powered by a fusion reactor
???? -> ????
2060 -> fusion is so easy, let's use it for baseload
Sorry if I sound stark, but I'm already burnt out and fed up with the "breakthroughs" on batteries that never materialize - I have a very low tolerance threshold for startups promising fusion for next week ;)
If you're on to something, more power to you - we need that yesterday.
dust42
Also, what's you intermediate plans between :
2025 -> Post on HN
2028 -> Q>1 achieved (by you ? by someone else ?)
CFS plans Q>1 for 2027 with a tokamak design. If they succeed then there will be plenty of VC for similar designs. I'd place my bets that CFS succeeds with Q>1. And I think the real problem will be the energy flux and neutron handling and thus much more a material sciences problem than a plasma physics problem. Thus the idea to look for a niche that has lower power needs is a very clever one. My bet would be rather on Maritime Fusion than Helion. But nevertheless, CFS will be likely first at Q>1 however there is always space for another competitor.
jtcohen
Exactly this !!
beambot
Let's also be really explicit... CFS is targeting Q>1 by 2027 for nuclear fusion via the SPARC reactor, but not Q>1 for electrical generation. The latter is slated for sometime in the early 2030s via the subsequent ARC reactor.
All of this is driven by HTS. Fusion reactors (generically) scale to the inverse^4 of magnetic field strength. HTS doubled the achievable magnetic field strength of electromagnets, which means that ITER-like performance can be achieved in university-scale reactors at comercially-viable, lower costs.
Dr. Dennis Whyte (MIT Nuclear Eng Prof) gave a great seminar at Berkeley that covered some technical nuances. It's mandatory watching if you want to geek out and understand the fusion hype: https://www.youtube.com/watch?v=rY6U4wB-oYM
ClumsyPilot
> that ITER-like performance can be achieved in university-scale reactors at comercially-viable, lower costs
Are they going to upgrade it or it’s already obsolete before it was even finished?
kelseydh
Is that QPlasma>1 or QTotal>1?
AtlasBarfed
Batteries are steadily improving, at least in the cost factor. We haven't seen any 2x leaps in density from sulfur or solid state or aluminum air.
But LFP and Sodium Ion are making undeniable progress in cheap usable EV batteries that don't require nickel or cobalt.
phtrivier
> cheap usable EV batteries
I know this is going to sound harsh, but I will personnally consider EV batteries "cheap" only when they pass the very scientific "my mom can use the EV exactly like shes uses her car, and she does not notice" test:
* on one charge, drive 10-50km daily for 350 days in a year
* on one charge, drive 1000km in one go for the holidays
* it must be less than 10kE at a local car dealership
* it can be plugged in your garage
* if you forgot to charge it, you can stop every 10km to recharge in 10m
I know: "it's harsh" ! "We should change our car usage" ! "My mom should live differently to accomodate the technology", etc... Go tell that to my mom.
Still, that's the goal post I've been having for 20y, and 10y ago people where writing headlines about "breakthroughs" that would make this possible any time now. And it's not. So I'm burnt out, kinda.
Earw0rm
If you fix your goalposts for long enough, cohort effects will move around them.
I'm not sure how old your mom is, but 1000km drives aren't something most people want to be doing past 75 ish. And newer cohorts adapt their lifestyles and expectations to available technology, whether that's charging time, on-demand rental for the occasionally needed longer distance EVs, and so on.
Although I can't help thinking that hybrids are a better fit for this common usage pattern - given a choice between hauling the dead weight of a rarely-used gasoline engine, or the dead weight of the 80% of battery capacity you hardly ever use, the gas engine is cheaper and less demanding of rare metals.
It's a shame that weight considerations mean "rent 80% extra range in a removable module for occasional use" isn't a practical option. You could almost have a 10kWh/50km light EV with a gasoline generator or extra battery in a hitch trailer, but the trade-offs don't quite work.
AtlasBarfed
Dude, get a PHEV.
rgmerk
I'm not sure I'm seeing the relevance here. Incremental advances in battery tech (or even futuristic step-change prospects like lithium-air batteries) won't solve intercontinental shipping.
isatty
The HN battery checklist needs to be reworked for fusion power. Arguably, even though people think it’s trolling to use the checklist, I’ve found it surprisingly educational each time.
quchen
Sounds interesting, could you post that checklist?
d_silin
And one for fusion
----------------------------------
Dear Nuclear Fusion Power Claimant
Thank you for your submission of proposed new revolutionary nuclear fusion power technology. Your new technology claims to solve humanity's energy problems, produce unlimited clean energy, and is just months away from commercialization. Unfortunately, your technology will likely fail, because:
[ ] it requires materials that cannot be produced at any scale.
[ ] its energy gain (Q factor) is still substantially less than 1.
[ ] its plasma instabilities modes are completely unknown.
[ ] its plasma modeling behavior relies exclusively on numerical simulations.
[ ] it cannot sustain required plasma confinement criteria
[ ] it cannot handle the neutron flux without rapid degradation of components.
[ ] it requires magnetic fields stronger than currently achievable
[ ] it consumes more energy in cooling systems than it produces.
[ ] your claimed breakthrough violates fundamental physics.
[ ] the same approach was tried in the 1960s, 1970s, 1980s, 1990s and abandoned each time for good reason
[ ] by the time it ships, renewable energy plus storage will be far cheaper.
[ ] your timeline has been "5 years away" for the past 50 years.
[ ] your claims are lies.
Sincerely, The Energy Research Community
d_silin
This one I presume:
----------------------------------------------------------------
Dear battery technology claimant,
Thank you for your submission of proposed new revolutionary battery technology. Your new technology claims to be superior to existing lithium-ion technology and is just around the corner from taking over the world. Unfortunately your technology will likely fail, because:
[ ] it is impractical to manufacture at scale.
[ ] it will be too expensive for users.
[ ] it suffers from too few recharge cycles.
[ ] it is incapable of delivering current at sufficient levels.
[ ] it lacks thermal stability at low or high temperatures.
[ ] it lacks the energy density to make it sufficiently portable.
[ ] it has too short of a lifetime.
[ ] its charge rate is too slow.
[ ] its materials are too toxic.
[ ] it is too likely to catch fire or explode.
[ ] it is too minimal of a step forward for anybody to care.
[ ] this was already done 20 years ago and didn't work then.
[ ] by this time it ships li-ion advances will match it.
[ ] your claims are lies
buildsjets
If you are fantasizing the implementation of an imaginary future technology, why not fusion power for SPACE ships?
simne
Because nobody predict so large grow of space industry, which could make fusion profitable.
Second problem, for space weight is so expensive, that it made fission viable, and solve proliferation problem (very little risk, somebody will steal materials from Moon or beyond).
nancyminusone
You still need somewhere for the heat to go, and that's a lot easier if you're on top of water instead of nothing.
Although, a good radiator on a spacecraft still seems trivially easy compared to having a working fusion reactor in the first place.
oldgradstudent
Controlled by a quantum computer, obviously.
scrumper
"First-wall power flux" - am I right in thinking that means the heat energy the innermost wall has to contain? Half a megawatt per square meter? Good lord. You're not making it out of 3/4" plywood then.
Maintenance isn't just about downtime though right? This is gonna have to be supported by your crews traveling globally with trade secret, exotic parts. Not even on the top ten hardest things about this of course.
It's an exciting bet for sure, so good luck - if it works, you're taking a big bite out of a really nasty carbon source.
jandrese
I think your timeline is at best optimistic. I would personally like to see fixed land based fusion power work before we start trying to build them into moving vessels.
Your claim that the shipping industry is "desperate to decarbonize" also needs a citation. From what I've seen shippers top three concerns are "how to minimize costs", "how to reduce costs", and "how to save money". Can you make this system cheaper to operate than heavy fuel oil? If not it is unlikely to gain traction.
Terr_
> Your claim that the shipping industry is "desperate to decarbonize" also needs a citation.
If anything, I think the shipping industry will be the last to de-carbonize, in the same way it's been the refuge of burning dirty fuels and NOx emissions.
julosflb
Nearly 40% of shipping volume worldwide is moving fossil fuels (coal, oil, gaz). The easiest way to reduce drastically shipping emission is reducing usage of fossil fuels...
https://www.ics-shipping.org/resource/shippings-role-in-the-...
Terr_
That's... not what's being discussed, though?
We're talking about whether the shipping industry will choose to improve how their ships operate, but you're talking about new powerplants on land would remove the need to even have those/as-many ships at all.
marssaxman
> before we start trying to build them into moving vessels
Why wait, though? I agree that the timeline - the whole project! - seems extraordinarily optimistic, but I don't see why development of potential maritime applications should create any obstacle to the simultaneous development of grid power applications.
jandrese
Lots of potential complications when building something on a vessel and failure is more likely to be deadly, if for example it fails because the ship is being battered too much by a storm. Plus there is the complicating factors with needing to miniaturize the equipment enough to fit in the available space.
creer
To be fair, a small fusion reactor actually producing power day in, day out - would be a ridiculously huge success. Before worrying about reliability in a storm or miniaturizing (to the point of that being irrelevant). There will THEN be this challenge of reliability and size but achieving the first step would release a sea of additional funding.
marssaxman
That all sounds reasonable. Sometimes the economic problems are harder to solve than the technical ones, though, and that's what interests me about this proposal. I have had a bearish outlook on fusion power in recent years, because utility-scale grid power is the most competitive market there is, and the cost of solar & batteries have been dropping so fast that it's not clear there would be any economic justification for a fusion power plant even if we knew how to build one. An intermediate market, willing to pay much more money for far less power, where renewables cannot compete, seems like it might be just the thing fusion needs to transition out of research and into practical use - even if it does take more engineering to cope with the rigors of the sea.
rnhmjoj
> One common question is, why not fission? Fission works technically, but not practically. Small Modular Reactors (SMRs) could power ships, but licensing fission reactors on land is already brutally hard and expensive—doing it for vessels moving between international ports with enriched uranium is nearly impossible
What makes you think that licensing a fusion reactor will be easier? Safely handling tritium is fantastically more complicated that the fuel of a fission power plant.
Also, do you plan on breeding your fuel aboard the ship? If no, how do you plan to produce, store the tritium and refuel the ship? If yes, I'd like to know how you are planning to host the massive chemical plant to purify coolant, recycle unburt fuel, separate isotopes, detriatiate water and refuel that comes with your tokamak.
jtcohen
Safely handling tritium is fantastically more complicated that the fuel of a fission power plant - I disagree with this, especially when considering the infinitely long HLW with fission fuel. Handling Tritium isn't easy but it's much more manageable.
Tritium breeding: we will have a FLiBe blanket and breed tritium, but we won't be processing and pulling out the Tritium on board, that will happen on land, so at port you drain the Tritiated FLiBe and replace it with Li-6 enriched FLiBe. There's a few companies working on the Tritium fuel cycle technology that are making great progress.
rnhmjoj
> infinitely long HLW with fission fuel
You don't have to process high level wastes on your ship, but you do with tritium. Even if you don't plant to extract the tritium from the blanket modules, you do need to recycle the unburnt fuel (the burn-up fraction is at best a few percent).
Tritium is radioactive hydrogen: it's a gas that explodes in air at low concetrations, it reacts with organic compunds, it has high mobility in pretty much any material, by decaying it produces Helium bubbles that can embrittle metals, its β radiation crack glasses etc.
caycep
unless you're the US Navy...
outworlder
[flagged]
Hey HN, we’re Justin and Jason, co-founders of Maritime Fusion (https://maritimefusion.com/). We’re working on putting fusion reactors on ships—specifically, large container ships and defence applications. Should be easy!
Yes, we know: fusion has been the energy source of the future…and it always will be. But high-temperature superconductors (HTS) have changed the game for magnetic confinement, and we believe we’ll witness Q > 1 within a few (say 3) years. That’s huge.
(Side note: Q is the ratio of input power divided by output power. Q> 1 means the reactor is producing more power than it consumes, achieving ‘breakeven.’)
However, getting to breakeven is just the first daunting challenge. Making the first-of-a-kind (FOAK) reactors cost-competitive on the grid? That might be even harder than achieving breakeven.
That’s why we’re taking this soon-to-be breakthrough in fusion and applying it to the first market we believe makes sense: ships.
Instead of targeting 24/7 baseload grid electricity—where fusion has to compete with solar, wind, batteries, and natural gas—we’re focusing on large commercial shipping (>10,000 TEU) and mobile military vessels to provide ship-to-shore power capability.
Why ships? They don’t have great alternatives—the shipping industry is desperate to decarbonize. Hydrogen and ammonia are being explored, but come with serious downsides: low energy density, flammability, leaks, and massive infrastructure challenges. Fusion will provide a high-energy-density, long-range solution without the same infrastructure challenges—once it works, of course!
One common question is, why not fission? Fission works technically, but not practically. Small Modular Reactors (SMRs) could power ships, but licensing fission reactors on land is already brutally hard and expensive—doing it for vessels moving between international ports with enriched uranium is nearly impossible. Public perception is another major barrier: if we’re deploying thousands of nuclear reactors globally, they need to be meltdown-proof. Fusion is the only way to guarantee that. Regulation also isn’t as bad. While fusion won’t be a walk in the park to license, the NRC has declared a distinct framework for it—more like particle accelerators and hospitals than nuclear power plants. That’s a game-changer.
Instead of a 500+ MW grid-scale reactor, our system is 25 MWe, designed for ship propulsion. Our tokamak is roughly JET-sized, but with HTS magnets (8-9T) and higher plasma current (~10MA). The first-wall power flux is down from multi-MW/m² to nearly 500 kW/m²—still tough, but not nightmare mode. The materials challenges associated with the first wall and nuclear activation of the structures is greatly reduced. Also, ships don’t require 90% uptime like grid power plants. Downtime for maintenance is part of normal operations, making this a far more forgiving early application of fusion, unlike the grid where every down hour is lost revenue.
Jason and I come from SpaceX and Tesla, where we solved hard engineering problems at scale. My background is nuclear engineering (NC State, BS) and plasma physics (Columbia University, MS). We’ve been busy during our time in YC making technical progress on our reactor design, and are in the process of assembling a team of engineers who can pull this off.
This is a ridiculously hard problem, of course. But we think it’s the right hard problem—one that’s actually solvable (and worth solving!) with today’s tech if applied correctly. Eventually the cheaper and more robust SOAK and NOAK (second-of-a-kind and nth-of-a-kind) reactors will arrive in the coming decades (2050-2060) and then we'll pivot to decarbonising the grid and saving the world (we'll need to change our name), but until then we'll be out in the ocean!
Would love to hear your thoughts—whether you’re deep into plasma physics and engineering, skeptical-but–curious, or convinced it will never work . Ask us anything!