There's an annoying mix of units in the article. Li batteries described in terms of watt-hours per kg (energy density) but radioactive batteries described in watts per kg (power density?).
DARPA looking for battery that could power a laptop for months
Forget recharging or swapping out disposable AAs every day. What if you could power energy-hungry devices for months or even years at a time from a single, reasonably-sized battery? A Washington state-based fusion energy startup is helping to make that dream a reality for DARPA, which wants higher-power radioactive batteries for …
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Thursday 9th April 2026 01:50 GMT Bill Gray
I think the difference is that lithium batteries are (mostly) thought of in terms of capacity : total watt-hours, and you're concerned both with how much power they generate and how long they're going to do it. With a radioactive battery, you're concerned with the power generated and (usually) not so concerned about how long it's going to last.
So describe them in watt-hours, and the radioactive batteries look wonderful, and we quietly ignore the fact that most of their watt-hours won't come out until decades after the mission is over. Describe them in watts, and the chemical batteries look wonderful, and we ignore the fact that they die young.
When the Voyager spacecraft were launched, I'm sure a lot of thought went into how much power the RTGs would put out. The Pu-238 has a half-death of 87.7 years; that comes to a whopping number of watt-hours by the time they (for practical purposes) go dead, but most of it would occur long after the mission's expected end (about a dozen years from Voyager 2's launch to the Neptune flyby). If they got lucky enough that it lasted that long... I doubt anybody expected it'd still be running 48 years after launch.
And now I've been nerd-sniped again... the usual source tells me that Voyager 2's RTGs provided 470 watts at launch. Total power generated would be equivalent to running at that level for 87.7/ln(2) years and then stopping, so
470 watts * 87.7 years * (365 days/year) * (24 hours/day) / ln(2) = 6 million watt-hours
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Thursday 9th April 2026 02:00 GMT Bebu sa Ware
mix of units
"There's an annoying mix of units in the article. Li batteries described in terms of watt-hours per kg (energy density) but radioactive batteries described in watts per kg (power density?)."
Fair point.
I suppose for a battery that continuously supplies power for months W/kg makes sense - the W/kg × months probably not a particularly useful measure as unlike an Li battery you cannot extract your W-hrs at different rates. Bit like a fixed annuity v. bank deposit I suppose.
I don't realistically expect this type of tech to ever be used outside military, space and very specialised applications. Fortunately.
Fusion reactor in a shoebox — either a mob of one hand typists or grifters … likely both. Apart from the woolly mammoth of everything else, the elephant in the room with fusion is that it too produces significant radiation. Six fingered sprogs? … more like broiled prairie oysters.
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Thursday 9th April 2026 11:41 GMT itzman
Re: mix of units
Unlike 'renewable' energy which relies on well understood classical physics, and batteries which rely on well known electrochemistry, nuclear batteries rely on the fringes of quantum theory.
Whereas we can know the limitations of chemical batteries and renewable energy, all we know about nuclear batteries is that *in theory* they *could* be monumental.
Its worth keeping research going
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Thursday 9th April 2026 17:48 GMT M.V. Lipvig
Radioactive battery is where they went wrong as it's more like a nuclear reactor than a battery. A battery is a storage medium and the power is generated elsewhere. A radioactive "battery" is actually generating power, not storing it.
I do wonder what happens when the load disappears. A nuclear reaction also doesn't really have an off switch, and a failure in a dampener would be a bit of a mess.
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Thursday 9th April 2026 09:06 GMT frankvw
Re: Radioactivity on your lap ?
While the dangers of radioactivity are not to be sniggered at, it's not all a horror story. There's radioactivity and there's radioactivity.
The main and most well-known form of radioactivity comes in the form of gamma radiation, which is electromagnetic. In this case, however, we're talking about beta-radiation. Simply put, beta radiation is electrons. A beta-emitting source (as used in these beta-voltaic batteries) emits electrons, plain and simple. Electrons (like the helium nuclei that alpha radiation consists of) are, to all intents and purposes, particles, or at least behave as such when it comes to shielding. Alpha and beta radiation is easy to shield. Beta radiation, for example, is typically stopped adequately by 3mm of aluminium. Shielding alpha particles is even easier: two sheets of paper will do the job quite nicely.
That's not to say that a beta-voltaic battery in your laptop is necessarily a good idea, because shielding can always get damaged, and beta radiation can harm skin and eyes. However, it won't penetrate deeply into the body (unless the beta-emitting material is inhaled or ingested) and therefore will not damage your DNA or that of your offspring.
But the idea that a beta-voltaic battery equates to a small nuclear reactor that will make you glow in the dark is incorrect. Nor should it be compared to the radio thermal generator (RTG) that powers Voyager probes and Mars rovers, since those draw their power from the heat of decaying Plutonium.
The main technical challenge here is scale. Getting an output in the 100+W range will be challenging. A beta-voltaic battery could use, say, 53Ni which is a pure beta emitter (no alpha or gamma) and has a halflife of about 100 years but yields only low-energy beta radiation (electrons). 90Sr is a high energy beta emitter, but has a halflife of just under 39 years, so it won't last as long. That said, wrap the whole thing in a few mm of aluminium and you're safe.
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Thursday 9th April 2026 18:21 GMT jake
Re: Radioactivity on your lap ?
True enough.
However, in the contract under discussion, the batteries that DARPA wants, in this case, are of the alpha variety.
Does nobody know how to parse English anymore?
Read and parse the article for yourself, it's not exactly difficult.
And try to remember that the Artificial Idiocy summary is pure garbage often enough that it can never be trusted.
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Wednesday 8th April 2026 22:34 GMT DS999
This is easy to do
The reason current radioisotope batteries generate so little power per weight is that their contents aren't very radioactive. You need just to stick in something that wildly radioactive and it could generate kilowatts per kilogram - if you ignore the weight of the shielding!
The big problem with these is that there is no way to turn them off. If you have a laptop that when running maxed out consumes 100 watts that you want to handle, you have to generate 100 watts ALL THE TIME. So however hot your laptop gets when it is running flat out is how hot it will ALWAYS be, and it'll be worse when you've got it insulated away in a laptop bag. It will have the fan going flat out at all times, even when you are sleeping.
This seems like a terrible idea. No one wants or needs a laptop without an off switch!
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Thursday 9th April 2026 02:34 GMT Eric 9001
Re: This is easy to do
If you add a big enough heatsink, 100W of heat could be dissipated without needing fans - it would need to built tough enough to not need a laptop bag and would have a handle instead.
Although, heating the room constantly with 100W of heat would be an annoyance outside of freezing cold climates.
Sounds like a great idea for a free software laptop really - it doesn't need an off switch - the freedom keeps flowing.
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Thursday 9th April 2026 03:52 GMT Anonymous Coward
Re: This is easy to do
Heatsinks do not cool devices, except for short bursts. The heat going into the heatsink has to go somewhere else, so you need either active or passive cooling of your heatsink. On earth, 100w of power will mean quite large fins to cool by natural convection, or smaller fins to cool by forced convection (use a fan). In space, that means connecting to a radiating panel via a heat pipe. Oh, and you will *always* have to dissipate the full 100 watts, because the electric power gets converted into heat when you are using it.
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Thursday 9th April 2026 06:52 GMT Eric 9001
Re: This is easy to do
I am well aware - clearly I meant a heatsink with oversized fins.
An appropriately designed and sized heatsink will passively dissipate 100W - or if you're okay with a heatsink that reaches >100°C, you can design a small heatsink with a chimney hole that exploits the chimney effect for silent forced convection.
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Thursday 9th April 2026 20:43 GMT DS999
Re: This is easy to do
This is a laptop. If you have a heatsink inside it, it is not going to be able to radiate heat away. If you have the heatsink outside it can radiate heat but you'll have a "so hot it will burn your hand" piece of metal poking out of it somewhere. Hardly a "lap" top at that point.
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Thursday 9th April 2026 07:21 GMT Paul Crawford
Re: This is easy to do
It also really depends on what/where you want to use one. For deep-space stuff (not just lunar orbit but Jupiter and beyond) you need the RTG's waste heat to stop the electronics from freezing. For something powering a underwater drone you have endless cooling available without issue, and that might be a double-plus if you are wanting it to bore through ice.
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Thursday 9th April 2026 20:45 GMT DS999
Re: This is easy to do
For deep-space stuff (not just lunar orbit but Jupiter and beyond) you need the RTG's waste heat to stop the electronics from freezing
No you don't. Not above a certain level at least. It is a problem for Voyager because its RTG outputs so little power and not as much power as it did when it was new. If it produced 10x as much power then Voyager's problem would be radiating away the waste heat.
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Thursday 9th April 2026 18:03 GMT brainwrong
Re: This is easy to do
It's worse than that, if you want 100W of electricity then you'll have to dissapate substantially more than that in heat, the thermocouples that convert heat energy to electrical power aren't very efficient (<10%).
New technology may improve things, I recently read about a company called Fourth Power who had recently demonstrated a thermophotovoltaic cell with over 40% efficiency, although they may be using temperatures somewhat higher (up to 2400 C) than you could use with radioisotopes. Would anyone fancy a white-hot can of liquid Pu-238 inside their nuclear battery?!!
None of this shit is ever going to power your everlasting
gobstopperlaptop.Icon because fire!
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Friday 10th April 2026 20:55 GMT jake
Re: This is easy to do
"Yes whatever happened to that technology?"
The anti-science, back-to-earther hippies.
Paraphrased: "All radiation is bad, innit!" at the top of their lungs, everywhere, all the time.
Well, until they came down with smoking-induced lung cancer, of course ... fucking hypocrites.
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Thursday 9th April 2026 20:48 GMT DS999
Re: This is easy to do
Would anyone fancy a white-hot can of liquid Pu-238 inside their nuclear battery?!!
Why wouldn't I, the people (scientists) who claim that's dangerous are the same people who claim global warming is occurring, which I know isn't true because it was really cold here for a day or two a couple weeks ago!
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Friday 10th April 2026 18:02 GMT Excused Boots
Re: This is easy to do
Unless I’ve missed something in the article, which is quite possible, it doesn’t really talk about powering a laptop but a ‘laptop-class’ device. To me that means something that could provide sufficient power to, theoretically power a laptop continuously for decades but only have a mass of a few Kg. It’s quite a bit difference.
I don’t think anyone is suggesting actually putting something like this into a laptop - possibly either DARPA or the article writer had a bad choice of words.
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Thursday 9th April 2026 05:37 GMT Neil Barnes
Tsk, people are considering the wrong problem
Keep the existing lithium laptop batteries. Put the nuclear battery in a powerbank box. When you need it, plug it in; when you don't it's a (small) room heater. Of hand or foot warmer.
What could possibly[1] go wrong?
[1] The airlines might get a bit sniffy...
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Thursday 9th April 2026 07:20 GMT Richard 12
It's fake
The "Orbitron" is yet another near-identical fake in a long line of companies making the same cold fusion claims, long proven false, repeatedly. The linked summary page even contains much of the kind of nonsense one expects in the background of a Hollywood movie.
So why have DARPA awarded cash to such an obvious fake?
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Sunday 19th April 2026 14:49 GMT Jim84
Fusion gets all the love
I don't know why fusion articles get so much press, when advances in fission nuclear could provide the same outcomes much more feasibly (okay, its because fusion articles get eyeballs and clicks).
Advanced composite moderators (e.g. MgO-BeO composite) may enable high temperature gas cooled reactors without the reactor vessel being the size of a light water reactor reinforced concrete containment dome due to the thousand metric tonnes of graphite needed for moderation. They'd also enable better versions of any other type of reactor design currently using graphite as a moderator such as molten salt reactors, or thermal spectrum liquid metal cooled reactors.
Gas cooled reactors could allow very cheap electricity and high temperature output heat for sulphur iodine cycle thermal hydrogen production. Basically all the benefits of a fusion reactor without the (unsolvable?) problem of needing materials super resistant to very high energy neutron radiation.
News about the potential of composite moderators that work better than graphite in a fission reactor just doesn't get people's attention.
