hwillis

8 ms·

31.
by hwillis 1y ago
> Not surprisingly a very common failure mode is that if you induce currents in the coils of the brushless motors No, that doesn't happen. Currents can be induced in the wires to the motors, but not in the motors themselves. For
32.
by hwillis 1y ago
> How much energy, how long is the pulse, how close were the drones? 1 millisecond pulses and 70 kW continuous usage[1] which is roughly equivalent to the AN/TPQ-53[2]. 2 km range. > Regardless I think the primary challenge with
33.
by hwillis 1y ago
Does radar or radar reflection not count as "hard"? There's a lot more to electronics and electrical engineering than ICs.
34.
by hwillis 1y ago
A good N52 neodymium magnet can be 1.5 tesla- MRIs are usually 1.5 tesla. The pull force is around the same too- a steel object will experience say 20g, and 100 lb fishing magnets are not hard to find. The difference is the size. Even a l
35.
by hwillis 1y ago
The switches are right next to each other and have a very short throw[1]- it would definitely be possible to do them in under a second and it looks possible to throw them together. IMO that looks like a spot that would be pretty difficult t
36.
by hwillis 1y ago
You're massively misrepresenting what I'm saying. I am not dismissing nuclear or suggesting overbuilding solar by 5x. I am responding to someone who is dismissing solar now for the fantastical idea that nuclear is cheaper now
37.
by hwillis 1y ago
That's just not true, unless you mean resource reserves. Taiwan has the largest NG strategic reserve I know of (11 days) and the US has the largest petroleum reserve in the world at 19 days: https://en.wikipedia.org/wi
38.
by hwillis 1y ago
> You still need enough power to cover that, especially if it has been a cloudy/rainy day, or week, or month. That's besides the point! The window of highest demand completely covers the window of solar. You can build a LOT o
39.
by hwillis 1y ago
Numbers: In poland the solar output in December is 1/5th of July output while demand is ~10% higher. Insolation drops off quickly at higher latitudes so it dominates much more strongly than heating demand even if heating were electric
40.
by hwillis 1y ago
A 747 burns ~9 tonnes of kerosene per hour, creating ~29.6 tonnes CO2. The Monroe Power Plant produces 3400 MWe at ~1 kg CO2 per kWh, so ~3400 tonnes CO2 per hour. It's a little complicated to weigh stratospheric emissions- the CO2 ha
41.
by hwillis 1y ago
> and the fact that cycles of power generation in most cases do not align with usage. This is false. Power usage everywhere is highest when the sun is shining. There are also very very few places where solar power ever causes the ma
42.
by hwillis 1y ago
Same, hah. The similarity between gridwall and powerwall in another comment also snagged me. "Perfboard" has also gotten me before- both are perforated board, but one is used for quick circuit boards and the other (more commonly
43.
by hwillis 1y ago
Yeah, fair to say its feasible. ROSA on the ISS produces 240 W/m^2 and weighs 4 kg/m^2. The S6W reactor in the seawolf submarines run at ~300 C and produce 177 MW waste heat for 43 MWe. If the radiators are 12 kg/m^2 and rej
44.
by hwillis 1y ago
> If you wanted to have a very-long eva spacesuit you'd have to have radiators much bigger than your body hanging off of it. I was curious about this! The Extravehicular Mobility Units on the ISS have 8 hours of life support runnin
45.
by hwillis 1y ago
Per wiki: radiators reject 100-350 watts per m^2 and weigh ~12 kg per m^2. Not unlikely you would need 10x as much radiator as server. You need about as much area for radiators as you do for solar panels, but radiators are much heavier. T
46.
by hwillis 1y ago
Radiative heat transfer is proportional to T^4. If your suit is 300 K(80F), bumping the temperature up by 100 C lets you radiate 3.16x as much heat from the same area.
47.
by hwillis 1y ago
> Another unrelated point, a significant number of Iranian civil engineering graduates are women. A somewhat dichotomous economy, when you consider the theocratic restrictions on costume and behaviour. Iran does not have the same degree
48.
by hwillis 1y ago
There are dozens of elements and isotopes used in radiopharmacology. Highly enriched uranium is absolutely one of them -hence why energy.gov is posting about it- and it's significantly cheaper than using a particle accelerator to crea
49.
by hwillis 1y ago
> His install would have a net negative value to the Texas grid without it. Absolutely untrue. Solar and wind can always just be disconnected at any moment. Wind resources are also a huge inertia source- windmill blades are massive g
50.
by hwillis 1y ago
Iran is one of the top producers or radiopharmaceuticals from highly enriched materials including uranium. This should be unsurprising because Iran has a natural abundance of radioactive isotopes- the background radiation of spots in Iran
51.
by hwillis 1y ago
Radiopharmaceuticals are enriched to 60%. Iran is one of the top producers in the world. Iran has a natural abundance of radioactive isotopes- the background radiation of spots in Iran is extremely high: https://en.wikipedia.or
52.
by hwillis 1y ago
There is some improvement in vehicle control, but the biggest impact was inside the engine. Controlling the vehicle at transonic speeds benefits a lot from simulation- control inversion is an example. When grid find pass the sound barri
53.
by hwillis 1y ago
Electrical engineer: motors and sensors are not really any better- motors have gotten more efficient and sensors have gotten cheaper, but gold standard sensors like ring laser gyroscopes have existed since the 60s. > Launch-thrust engine
54.
by hwillis 1y ago
The DC-X was 9.1 tonnes empty and 19 tonnes full- meaning landing thrust was ~half of takeoff thrust. The Falcon 9 was 400 tonnes full and 26 tonnes empty, so takeoff thrust was >20x higher than landing thrust. That's a huge engi
55.
by hwillis 1y ago
Not in industry, but: rockets can be like 90% fuel by weight. All engines on 105% can lift the rocket, so if you want to land while the tanks are nearly empty you need to be able to get to less than 1/10th of your thrust. Turning off
56.
by hwillis 1y ago
> As well as needing waaaay more of it Have you done an accounting of how many kilometers you can fit on a 200,000+ tonne boat? Seems to me you could cost-effectively carry nearly 20x as much cable weight as current cable layers. You n
57.
by hwillis 1y ago
> So that'll cause the tube to break. Glass builds up hige amounts of stresses when it cools down quickly (see prince ruperts drop) so needs an annealing step. Did you miss that the prestress is the point? There also could still be
58.
by hwillis 1y ago
High voltage does not induce pinch, only current. High voltage is used to create bursts of high current in can-crushing demonstrations. The cable is solid and the current is not concentrated in a thin cylindrical shell. The pinch is ne
59.
by hwillis 1y ago
Ever heard of fiberglass...?
60.
by hwillis 1y ago
It does have to be thin. You need to fit as much as possible on a boat and volume increases quadratically with thickness- so if glass is 500 MV/m and XLPE is 150 MV/m you would need to carry 11x more of it. Refilling means hundr

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