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Comment by Clewza313 | Hacker News Reader

There's been talk of shipping a nuclear reactor to power a base on Mars. The Antarctic experience indicates pretty clearly that from a reliability point of view, we're almost certainly better off with solar panels, wind turbines and batteries.

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I feel like nuclear power is the only tech that people perceive to be static in development. Isn’t it like saying we should have stopped using computers in the 40s because they were big, expensive, slow, and we’re only frequently used to kill people?

Nuclear power was great until 1986. Then it was bad. Then it was getting a bit better until 2011. Then it was bad again. Now it's a getting bit better again.

...and up until today, we're still using reactor technology from 70 years ago.

Which to me indicates that it is a fantastic technology if they're still around after 70 years.

Nobody is building new reactors with 70 year old designs though.

Why? Could you source your statement? Not that I'm doubting you, but I would like to learn more. :)

1986: https://en.wikipedia.org/wiki/Chernobyl_disaster#Nuclear_deb...

2011: https://en.wikipedia.org/wiki/Fukushima_Daiichi_nuclear_disa... and in the aftermath for example https://en.wikipedia.org/wiki/Nuclear_power_phase-out#German...

One would hope that after such a disaster, and given the pros of the underlying technology, more funding and research would be focused on safety, rather than abandoning it.

I wonder to which degree has nuclear power's association with nuclear weapons affected its public perception.

It's a reference to the Chernobyl disaster in 1986 and Fukushima in 2011

Thanks. (Is a simple thanks a valid HN comment?)

1986 is chernobyl, 2011 is fukushima. His comment isn't on safety, but perception of safety.

You are right, perception… Knowing that those years referred to those disasters, it feels a tad ridiculous to have asked for sources, but thanks :-)

Fukushima nuclear disaster in 2011 was among the worst nuclear disasters in history; not only because its human toll was so high, but also because it was the "final straw" -- so to say -- in public opinion in Western countries that made people scared of nuclear energy. Nuclear energy remains the safest, cleanest way to produce energy but Chernobyl and Fukushima significantly reduced the funding going into this kind of research, because public opinion was very much against nuclear power. It is getting better recently, but if history shows anything in the next 20 to 30 years we will have another disaster that will change public opinion again.

>not only because its human toll was so high

1 radiation death and 18 injuries? (Only 2 of which involved possible radiation exposure.)

The "overly-conservative" decision to evacuate such a large area killed more people than if they hadn't evacuated at all.

Even Chernobyl only killed ~30 people, with maybe another 30 cases of cancer that workers had since then.

Sorry I phrased it wrong. I meant to say "not because". That "only" is extraneous.

I see. Thanks for the explanation. I had been thinking in terms of the technology rather than in its public perception (although sure… that perception influences funding for the technology).

Now I see that I would have been well served by looking up 'nuclear 2011' and 'nuclear 1986' since those disasters are very famous.

But thanks to all for telling me. :)

You forgot about 1979.

Wind turbines? We're going to ship 30 meter blades to Mars so we can barely power a microwave and a few lightbulbs? A 1MW installation in a good location on Earth will average ~300kW. On Mars that will likely be 1% because of the air density difference, or 3kW.

Solar power on Mars would also give you around half the energy you get on Earth, per unit area. It’s basically like running solar panels on earth well beyond Arctic circle.

30m sounds small. Also, not only is the atmosphere thinner, but sand particles are 4x smaller. Have fun repairing those moving parts with that erosion.

And this is one if many, many reasons why Mars is and always will be orders of magnitude harder to habitate than earth.

Given the different conditions, you would use a different design on Mars: probably a no-moving-parts ion-release system.

There simply isn't much energy in that wind, no matter how you plan to harvest it. It's like trying to get water from a stone (possible, but you won't get much.)

You just need to process a great deal more of it. But there is no upper limit to the size of an ionizing grid, and the mass is negligible.

> On Mars that will likely be 1% because of the air density difference,

Power goes as v^3, so a few x wind speed compensates for density. There are design sketches for a couple of kW at 10 m/s, ~10 kW at 25 m/s. Getting those speeds does require prioritizing it in site selection. IIRC, turbine mass is competitive with solar under dust storms.

I'd link to recent work, but sci-hub doesn't have it. :/

No, it indicates exactly nothing. You’re talking about 1970e technology (ie when the computing power on Apollo was roughly a pocket calculator) vs how we will actually get there, a period during which nuclear reactor designs have also evolved, and the navy in particular has learned a huge amount.

How does one article on the third portable reactor built tell us clearly anything at all about how we should power a hypothetical Mars base more than 60 years later

We've made great leaps in safety measures since then. I'm not convinced we've made much in the way of progress in terms of miniaturization, simplicity or cost of operation though, as you can see from the ludicrous cost overruns seen for basically all recent reactors.

Miniaturization is not desirable for nuclear power because of regulation. Each nuclear power plant is required to pay 375 million dollars in insurance, regardless of size. So this incentivizes building plants as large as possible.

Even without regulation, things like surface area to volume ratio still make larger reactors more efficient.

Are wind turbines really viable with Mars's atmosphere?

Not very.

https://www.nasa.gov/centers/ames/news/releases/2001/01_72AR...

> "Only during dust storms on Mars is there enough wind energy to operate a wind turbine," said Michael Flynn, another NASA Ames scientist. On Earth about 10 meters (33 feet) per second wind speed is needed to make electricity with wind turbines; on Mars about 30 meters (98 feet) is needed because of the extremely thin air, according to Bubenheim.

Incidentally, though, during storms is when power is needed most, as solar won't work very well during that time.

Sure, but a nuclear plant solves that issue without sitting around being useless 90% of the time.

But do you have the necessary infrastructure to maintain a nuclear reactor on Mars?

As the article points out, the device required significant manpower, had reliability issues and wasn't cost effective.

While it'd be relatively simple to build wind power locally once infrastructure is in place, the same cannot be said for nuclear power on Mars.

Autonomy and self-reliance are critical factors for outposts on Mars - a point that cannot be overstated.

We've made a lot of improvements to nuclear reactor design since the 60s, and potentially we'll have working fusion by the time we have a colony on Mars, which would probably be the best solution (can easily get H from water and then would have He which is useful).

I can't imagine a viable self-sufficient Mars colony that doesn't involve a lot of manpower anyway (I'm talking thousands of people).

Well a working fusion reactor would render any current power source obsolete anyway.

I wasn't necessarily thinking about complete self-sufficiency, just the fact that it might take up to 2½ years to get replacement parts.

Right but without complete self-sufficiency that applies to any power generation method. The only viable solution is to have enough raw material and redundancy on Mars that you can recycle things if something fails. e.g. have multiple redundant reactors, if one breaks you fix it, if it can't be fixed you dismantle it and start using the parts to build a new one, taking parts from other things when necessary and using parts you can't use for other things. Basically there needs to be enough "stuff" on Mars that you can use stuff to make other stuff in perpetuity. To my mind that would require enough diversity of equipment that you'd want on the order of 1000 / 10k people.

And of course Mars is not a totally barren world – another big part of the solution is to build things with materials that can be gathered on Mars.

We have since deployed many nuclear reactors in space, with totally different reliability, so those should be used as reference. They can be packed on a rocket, launched, turned on and work for years unattended ( they powered societ radar satellites)

Cost is dominated by weight in space, and a large wind turbine needs hundreds to thousands of tons of concrete for foundations - are those going to be brought from Earth? Can you make concrete on Mars?

Pray that the rocket doesn't blow up spreading nuclear fuel all over the place. Here is a Soviet "success story" involving a nuclear reactor on a sat.

https://en.m.wikipedia.org/wiki/Kosmos_954

Concrete would need cement made with limestone and massive amounts of heat and water which is scrace on Mars.

Nuclear fuel that has never been "fired up" in a reactor is almost hamless - its just uranium. You could have it under your bed and you'd be fine, just don't eat it.

In this case the reactor would only be started once it arrives on mars.

I know, that's why I did not say radioactive waste.

Let's do a simple calculation, shall we?

Wind power is calculated by A * v³ * ρ * η

A is the area, e.g. π/2 * r² for horizontal axis designs, ρ is the air density and η is the total system efficiency (limited to <59% and safe to assume to be >0.4 for modern systems) and v is the wind speed.

Mars' atmosphere is about 1% of Earth's atmosphere in density. Given a wind speed of 7 m/s² (the optimal wind speed for most modern wind turbines), on Mars we'd get only 1% of the power we'd get on Earth.

A 100m installation (~2.6MW on Earth) would deliver only 21kW on Mars. The average wind speed during a year is slightly higher on Mars, though, at 10 m/s² [0]. The average power output thus would be about 61kW.

The most important time, however, would be dust storms, which render solar useless. Wind speeds have been recorded to exceed 30 m/s² during dust storms. Assuming we can efficiently shield the generator from the dust, the power output would peak at 1.7MW.

A more conservative 17 m/s² for dust storms still yields about 308kW.

100m class wind turbines, while rare on Earth (e.g. GE Haliade-X [1]) would be easier to build on Mars given the significantly lower gravity.

Wind turbines would work on Mars and have great synergy with solar - when solar doesn't work (e.g. during dust storms), wind turbines would be most efficient.

Wind power wouldn't be the first choice for powering a Mars station, though. As can be seen above, installations would have to be pretty significant in size to deliver noteworthy amounts of power.

[0] https://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.htm...

[1] https://www.ge.com/renewableenergy/wind-energy/offshore-wind...

A 100m wind turbine would require a lot of material and/or energy to construct, though - some of the materials would have to be processed locally, I wonder what the embodied energy of such a structure would be, and how long it would take to be net energy positive.

I don't think 100m wind turbines on Mars are feasible anytime soon. Even Starship has only a 18m high cargo area, so even if we assume that blades are assembled out of two parts in-place, you get only a 40m radius. That reduces the average power to just 10 kW.

Furthermore, I think your average 10 m/s is an overestimation -- the source gives it as the high limit outside of dust storms.

> I think your average 10 m/s is an overestimation -- the source gives it as the high limit outside of dust storms.

You misread the source then - peaks during sandstorms are 17 - 30 m/s² with 10 m/s² being the annual average.

> I don't think 100m wind turbines on Mars are feasible anytime soon.

Manufacturing of the wind turbine is assumed to entirely take place on-site. Wind power is not something for a "starter station/settlement". The question was about general viability and given local manufacturing capabilities, wind power isn't completely useless on Mars.

> You misread the source then - peaks during sandstorms are 17 - 30 m/s² with 10 m/s² being the annual average.

Where on the page? The only wind speed related data I can see is this:

> Wind speeds: 2-7 m/s (summer), 5-10 m/s (fall), 17-30 m/s (dust storm) (Viking Lander sites)

Also m/s² isn't the correct unit for wind speed, since it's a unit of acceleration, not speed.

>Given a wind speed of 7 m/s²

Isn't speed m/s and acceleration m/s/s?

Yep it is - typo on my part.

> would be easier to build on Mars given the significantly lower gravity.

In one sense yes, but in another sense no. Consider erosion. It is the bane of existence for any system near the ocean. Mars has a similar problem with dust, which is smaller than what we see on Earth. This shreds electronics and other instruments on Mars. Sealing becomes far more important, but also more difficult. The other thing we need to recognize is that on Mars there's no electric ground.

So yeah, on surface things look easier but there's a reason why including domain experts in the conversation is necessary. This is a classic example of napkin modeling being representative of how things will work in reality.

So look to the domain experts. They've used solar and nuclear for a reason. Maybe dig into why those were the choices made.

What does it mean to say "there is no electric ground" on Mars? You would not be willing to drive a spike deep into the ground, as is done on Earth? Or are you saying that without ground moisture, the ground would not be conductive enough?

It has to actually do with the magnetosphere. It's not about will to put a spike of metal into the ground but that doing so doesn't create an electric ground like it does on Earth because there is not this electromagnetic differential.

There are solutions for that problem which involve a tiny source of alpha radiation and the atmosphere. Basically a modified lightning rod.

Source? I'm not quite sure what you're saying and I haven't heard of it myself.

Sure thing. Here you go:

  Safe on Mars
  Precursor Measurements Necessary to Support Human 
  Operations on the Martian Surface (2002)

  Ch.3 Physical Environmental Hazards, Pg. 21

> A combination of technologies might also be considered, such as point-discharge, needlelike devices or even small radiation sources to prevent charge buildup. [0]

The small radiation sources refer to weak sources of alpha radiation (think smoke detectors), whose low-energy alpha particles collide with the atmosphere, ionizing it in the process. The now conductive atmosphere in the vicinity of the rod-device would then be able to neutralize excess charge.

[0] https://www.nap.edu/catalog/10360/safe-on-mars-precursor-mea...

The PDF version is available free of charge. The book can also be read online for free.

That makes no sense.

What has a planetary magnetosphere got to do with electrical ground? The planet itself is a spherical conductor. There probably is an ionosphere, although I would not be surprised to find that it is much nearer ground level than ours.

Because without a magnetosphere there is 1) no potential difference between the ionosphere and the surface 2) charge particles from solar wind (and cosmic radiation but mostly solar wind) accumulate on the surface. There's technically an ionosphere but it is extremely weak because Mars's dynamo isn't moving.

Also ground is about a differential. What you don't want is floating potentials. You want a constant refernce value. Floating potentials are dangerous because you don't have a constant reference value and thus the chance of unwanted discharge.

> on Mars there's no electric ground.

I'm intrigued. Is it due to much drier conditions? Grain size? Mineral composition? Combinations? Anywhere I could read a bit more?

It's because Mars's magnetic core isn't spinning, which is also why there's no magnetosphere.

As a quick intro that isn't doesn't have much detail but has links I'd go with[0]. But if you pick up any book on Martian engineering or read any report (NASA reports are public) you'll find mentions of this. This is also discussed deeply in most astrophysics textbooks.

[0] https://hackaday.com/2017/08/17/living-on-mars-the-stuff-you...

The article says it is about dryness, not anything to do with a magnetosphere.

Are you talking about the Kilopower project https://en.wikipedia.org/wiki/Kilopower

it’s completely different design from conventional “pressurized water” reactors with drastically reduced complexity, using heat pipes and solid core, it’s more like a battery really, and we’ve been sending nuclear batteries to space for many decades

Is an experience with a reactor designed and built in the very early 1960's really relevant? Would you also use experiences with early solar cells to vet out their viability today?

Nuclear power requires serious amounts of cooling...

Without easy-access to water and evaporative cooling on Mars, I can imagine you'd be needing super big radiators pointing at the sky to make even modest amounts of electrical power. Solar might work out better...

From a reliability point of view, you're better off with constant power to keep humans alive, instead of fluctuating power that can cause humans to die.

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