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I've done a precursory skim of this and plan to start reading it in earnest next week. Looks comprehensive and accessible. Very excited.

e.g. HashCash


Regardless of net efficiency, that still entails collecting CO2 at a central facility (where it could have been dealt with in other ways, such as injection underground) and sprinkling it through the air as you fly over delicate ecosystems. I'm sure bankers see both as net zero, but condors might have more issues with your simpler workaround.


> sprinkling it through the air as you fly over delicate ecosystems

I wouldn’t be so sure spraying water vapour is innocuous. As long as it’s atmospheric CO2, the environmental impact of synthetic fuels is much less than rebuilding the world’s air fleet and fuelling infrastructure to accommodate hydrogen.


That gravimetric energy density is about 2 orders of magnitude higher than lithium ion batteries.


The difference in volumetric energy density is not that big though, and hydrogen is not as flexible as jet fuel or even batteries when it comes to how you can store it in the vehicle.

To be fair, high gravimetric density is a fairly large advantage for an air plane. But the bad volumetric energy density does present some serious challenges.


So why it’s not used in rockets?


It was used in the Space Shuttle and SLS uses the same engine as the shuttle.


Also nobody launches to orbit using lithium ion batteries as main propulsion.


> Also nobody launches to orbit using lithium ion batteries as main propulsion.

It can be part of the main propulsion.

https://en.wikipedia.org/wiki/Rutherford_(rocket_engine)

https://en.wikipedia.org/wiki/Electric-pump-fed_engine


That's why I phrased it that way.

Most internal combustion engine cars have a lead acid battery to start it up and run the spark plugs (or preheat the glow plugs if diesel). They don't get called "hybrid" or "battery powered" because the batteries aren't the propulsive power themselves.

This is akin to that: the batteries run the pumps, they're not the propulsive system itself.

Ion drives can be run off battery, but you can't launch with those.


Unlike a car battery though, these batteries provide a not-insignificant part of the energy that is generated by the engine. Each Rutherford engine generates around 37 mega-watts of power at sea-level (24900 N and 3.05 km/s exhaust velocity, Power = 1/2 * Thrust * v_e) and there are nine in the first stage. The first stage battery provides around one megawatt [1].

That's about 0.3% of all energy generated by the engines, which is significantly more than what a spark plug does in an ICE.

[1] https://theaeroblog.com/the-rutherford-rocket-engine-the-fir...

This is the closest we have to electric power directly powering the ascent of a rocket from Earth.

Something like a HyperCurie engine (which is also electric pump-fed), could probably lift off from a planetary body like the moon. When they used it in orbit, they actually had to wait for the batteries to charge up from solar panels between each engine burn.


> not-insignificant

> 0.3%

> the closest we have

I don't understand why you're trying to paint the battery as a significant contribution here.

Like a car battery, although it's neat that they consider it as part of the engineering, it's none of the actual thrust unless it explodes.


It is about 1 megawatt (1341 HP) of the power pushing the rocket into the sky (directly translated into exhaust velocity and therefore thrust). That would be like a spark plug generating 1 HP in a 300 HP engine (Which would exhaust the typical car battery in about 1 second if it could even push that much power out).

It is all semantics anyway.


Correction: It won't drain in a second. But my point is the same. We don't really have 1 HP spark plugs out there :)


Rough estimates I've seen say the starter motor is about that, though. (Not that I can tell real pages from GenAI ad content farms, I'm not a petrolhead).

I'd agree "it's all semantics", but yours are confusing me :P

(And for energy content, like for like is comparing the size of the fuel tank with the capacity of the battery, but cars aren't 90% fuel by weight).


How many kg’s to orbit/year vs other fuels?


What exactly is your "social advertising bot"? Is this a bot that makes contextual comments like the one you're replying to?


Horses used to be smaller.

Przewalski's horse, the closest thing to a pre-domesticated horse, is about 660lb. A modern draft horse is over 2000lb.

50 mya, Eohippus was around 20lb - the size of a fox.


This was a phenomenal read. Thanks for linking


This is awesome! Presumably you can make this work with any interface that doesn't enforce the total internal reflectivity of a fiber optic cable, and therefore allows light to leak out. Instead of an air gap, have you tried experimenting with removing the cladding of the fiber optic cable, but keeping the core intact?

Alteratively, could you use a short segment of colored cladding that allows certain wavelengths to leak out more than others? I think that would allow you to encode each bend point as a different color-- which might require a different (more expensive) rx sensor, but could be useful for certain applications.


I did experiment with various ways of allowing light to escape but nothing came close to the properties of a total air gap. You can actually measure (relative) bend angle with it like a protractor since the attenuation is very linear!

There is already existing work that uses colored segments for something similar but those techniques are hard to do outside a well equipped lab.


First few instances I tried are either returning no results, or only DDG results.

Error! Engines cannot retrieve results:

brave ( Suspended: too many requests )

google ( Suspended: too many requests )

qwant ( server API error )


I've run in to exactly that. By putting my SearXNG on a machine that also does NAT for a busy network, this can be avoided. This is definitely one instance where IPs from a colo are a bad thing and residential IPs are a good thing ;)


If someone was running a supermarket and you came in day after day and never paid for anything, they'd get suspicious and probably follow you around all the time, too.

You don't pay for (almost) anything on the internet. Nobody does, because the requisite infrastructure doesn't even exist to allow you to pay for a page at a time. Until that changes, the creepy companies will keep finding ways to follow you around- both to earn money from advertising, and to ensure you're not abusing their systems.


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