Hacker News Reader

mchouzaon Swarming Proxima Centauri: Picospacecraft Swarms over Interstellar Distances

They don't, see https://arxiv.org/abs/2309.07061 . The basic idea is to use "picosecond-level" synchronization to improve the signal-to-noise ratio. They mention that a truly phase-coherent swarm would perform much better but they consider that a longer term prospect (section 2.1.4).

mchouzaon Toyota has been developing a solid-state battery for EVs with a range of 745mi

Probably just converted from 1500 km.

mchouzaon Microsoft is investing $1B in OpenAI

I am quite confident all the current employees of OpenAI qualify as real people. They certainly have problems and probably a good share of those problems are "real" too.

Of course their priorities may be off and they could be open to be persuaded to work in a different direction. But I don't think that condescension would be very effective for that.

mchouzaon Surprises of the Faraday Cage

Many theoretical and experimental studies were done. One example from the early 70s is http://ipnpr.jpl.nasa.gov/progress_report2/II/IIO.PDF

mchouzaon Drop the Supersonic Aircraft Ban

That's true, but supersonic planes also travel higher (Concorde -> 18 km, XB-70 -> 22 km). The real problem is that L/D decreases at supersonic speeds. For example, the XB-70 had a L/D of about 7, while the 707 had a L/D over 18...

mchouzaon Why it takes so long to get data back from New Horizons

It's mostly a question of power. The 1987 design for the TAU probe communication system would have handled 20 kb/s from 1000 AU... by using between 100 and 260 watts for the transmitter (and relatively big antennas):

http://ipnpr.jpl.nasa.gov/progress_report/42-89/89L.PDF

mchouzaon Researchers see signature of “Majorana particles” inside superconducting iron

Photons are generally considered to be their own antiparticles: http://van.physics.illinois.edu/qa/listing.php?id=27107

mchouzaon China's Island Factory – New islands being made in disputed China Sea

Japan has more than 1000 kg of HEU: http://www.nti.org/analysis/articles/civilian-heu-japan/

mchouzaon Wireless electricity? It's here

He is the first author cited in their paper:

http://www.witricity.com/pdfs/highly-resonant-power-transfer...

mchouzaon Brazil, Europe plan undersea cable to skirt U.S. spying

It's already public: http://www.dawn.com/news/1077275/nsa-tapped-into-undersea-ca...

mchouzaon Former BP geologist: peak oil is here and it will 'break economies'

Oil can be produced synthetically: http://en.wikipedia.org/wiki/Fischer%E2%80%93Tropsch_process

Though the FT process is quite bad from a CO2 emissions POV.

mchouzaon Ethiopian Binary Math

No, the algorithm as described is very different from binary multiplication. It requires a number of stones proportional to the result, while the number of bits required when doing binary multiplication is polylogarithmic.

It's a big difference: 1000 * 1000 would require 1000000 stones if done with the "Ehiopian algorithm", but it can be done with less than 1000 stones by using normal binary multiplication.

mchouzaon Show HN: My Isometric GPU-Powered Voxel Engine

https://www.google.com/patents/US4710876

mchouzaon Russian Proton Rocket crashes Seconds after Launch

You can launch from the ocean, though with more limitations: http://en.wikipedia.org/wiki/Sea_Launch

mchouzaon Canada and science: NRC will now only do science that promotes “economic gain”

Maxwell didn't come up with anything himself [...]

Maxwell "invented" the displacement current:

http://en.wikipedia.org/wiki/Displacement_current

mchouzaon NASA-backed fusion engine could cut Mars trip down to 30 days

In the short run:

- Ion thrusters are way simpler and they are trying to do something that is much easier.

- Ion thrusters are relatively mature, working "fusors" don't exist.

- Existing machines that are trying to get fusion breakeven are building-sized.

- Trying to start a fusion reaction is hard, it only makes sense if you get a commensurate result (energy gain).

In the long run, I'm very optimistic about fusion.

mchouzaon NASA-backed fusion engine could cut Mars trip down to 30 days

Yes, I agree. My point was that you cannot do substantially better than ion engines without having energy gain and, in fact, you are probably going to do much worse due to the weight of the "fusion hardware".

I'm quite optimistic about magnetized inertial fusion. But the idea of doing the job much better than the Z-machine, with something lightweight enough to carry into space and in less than 10 years seems to me... unlikely, to put it mildly.

mchouzaon NASA-backed fusion engine could cut Mars trip down to 30 days

Well, controlled fusion hasn't reached energy breakeven at all, even taking into account the kinetic energy of the reaction products. But the low thrust of current ion engines is mostly due to power restrictions (https://groups.google.com/group/sci.space.science/msg/0cb332...). If your spaceship has a mass of one ton and you want an acceleration of 1 centigee with an exhaust velocity of 30 km/s, you will need at least:

0.5 * thrust * velocity = 0.5 * (0.1 m/s^2 * 1000 kg) * 30 km/s = 0.5 * 100 N * 3E4 m/s = 150E4 W = 1.5 MW

of power.

mchouzaon NASA-backed fusion engine could cut Mars trip down to 30 days

If fusion doesn't provide a substantial energy gain, it's not worth the effort. Existing ion thrusters are quite efficient (60+%) at translating electrical power to exhaust kinetic energy.

mchouzaon NASA-backed fusion engine could cut Mars trip down to 30 days

Project Orion was much more than science fiction (http://www.scribd.com/doc/28668567/Nuclear-Pulse-Space-Vehic...) though it was much less than operational. Very big Orion spaceships would have used fusion explosions (http://galileo.phys.virginia.edu/classes/321.jvn.fall02/Dyso...), but not the relatively small ones that were subjected to detailed analysis.

mchouzaon Laser fusion put on slow burn

Simulating explosions helps determine maintenance for nuclear warheads?

It's not completely unreasonable: they need to validate the computational models that are used to check if an aged nuclear weapon will explode.

mchouzaon Billion-Ton Comet May Have Missed Earth by a Few Hundred Kilometers in 1883

A more skeptical analysis by Phil Plait: http://blogs.discovermagazine.com/badastronomy/2011/10/17/di...

mchouzaon Can You Stop a Hurricane by Nuking It?

The basic idea is to ablate the asteroid to deflect it: https://e-reports-ext.llnl.gov/pdf/343984.pdf http://permalink.lanl.gov/object/tr?what=info:lanl-repo/lare...

mchouzaon The CIA and Jeff Bezos Bet on Quantum Computing

There are some places in the "natural universe" that are colder than the CMB. That's because they aren't in equilibrium:

http://en.wikipedia.org/wiki/Absolute_zero#Very_low_temperat...

mchouzaon The CIA and Jeff Bezos Bet on Quantum Computing

It's not as stupid as it seems. Due to the cosmic microwave background, the equilibrium temperature far from other natural radiation sources is about 3K. But, as we don't know the temperatures in the whole universe and there are natural processes that can cool things below their equilibrium temperature, they should have said "... anywhere in the known natural universe".

mchouzaon One hiring filter that works

The puzzle can be found at http://meshcapital.com/application.tar.gz

mchouzaon Efficient represention for growing circles in 2D space?

You can try posting your question in http://cstheory.stackexchange.com/

mchouzaon Our Galaxy Has at Least 100 Billion Planets, Study Shows

The paper can be found here:

http://www.eso.org/public/archives/releases/sciencepapers/es...

mchouzaon NASA's new Mars rover "Curiosity" to carry nuclear batteries

All plutonium isotopes can be used to make nuclear weapons [1], though Pu-238 would give big problems to weapon designers due to its intense decay heat.

[1] http://cstsp.aaas.org/files/selden.pdf

mchouzaon What is the Limit to Human Population Growth?

Fast-moving people will also be Lorentz contracted, so there will be plenty of room... if there's enough energy.