For Questions That Don't Merit Their Own Thread

[DDE]

2 hours ago, mikegarrison said:

https://www.ecfr.gov/current/title-14/chapter-I/subchapter-C/part-38

I worked on this rule for six years almost full-time, and it has finally become part of US code. (It's been law in other places for several years now.)

Sub-sub-sub-sub-sub-sub-sections? Well, here I was scared of sub-sub-sub-sub-sections in Russia's rendition of the Basel III standard.

[mikegarrison]

You see these ugly gloriously beautiful sketches? I made this in about three minutes in Powerpoint for one of my working papers in ICAO CAEP Working Group 3, and somehow they ended up in the final draft, never getting replaced by something nicer.

[kerbiloid]

It would be nice of you, if you were typing dimension numbers and arrows right on the painting.

Then the engineers would no need to measure them with a rule before building in metal.

Edited April 20 by kerbiloid

[DDE]

1 hour ago, mikegarrison said:

You see these ugly gloriously beautiful sketches? I made this in about three minutes in Powerpoint for one of my working papers in ICAO CAEP Working Group 3, and somehow they ended up in the final draft, never getting replaced by something nicer.

I know the feeling. Last week I found a non-material typo in the heading of a report we've worked on for a year. Cringe.

[AckSed]

Could someone chase down some scientific papers on how induction hobs work? Specifically, how the power circuitry works? I want to see if it's possible to change over from using the cheap, microwave-style on-off temperature control to something more gradiated.

[K^2]

4 hours ago, AckSed said:

Could someone chase down some scientific papers on how induction hobs work? Specifically, how the power circuitry works? I want to see if it's possible to change over from using the cheap, microwave-style on-off temperature control to something more gradiated.

It's generally difficult to regulate power precisely and efficiently in another way. A rheostat will be generating huge losses, expressed as heat. And while a variable transformer is an option in some applications, it tends not to work well with induction specifically. Technology Connections has very recently did an entire video on the topic, primarily on the standard solution of using simmerstats, but these are doing precisely the thing you're trying to avoid and precisely for the reasons outlined. Technology Connection - Simmerstats

There is an example of a place where we do need to deliver a very measured amount of power while still being constrained by the same problems of efficiency and heat dissipation, which is electric motors. Especially in drones and EVs, but even a lot of RC toys rely on this these days. The solution is using ECS to deliver power to the motor. ESC is a solid state device, and it is surprisingly efficient, but under the hood, or under the plastic, really, what they do is still just very fast power switching. They do the same work as a simmersat does, but on the time frames of a single polarity cycle step of a brushless motor. The good ones will match the frequency of the motor using back-EMF as an indicator of the cycle, and then deliver a measured duration of an applied voltage to the motor's coils. Because the frequency is so high, the power delivery is effectively continuous, and you can adjust the torque of the motor as desired.

Something like this can be built for the inductor stove. The challenge is largely the same. You have to match the oscillation frequency of the induction coil with your power pulses, and then adjust the duration of the pulses to deliver the right amount of power. You might be able to modify a brushless ECS to drive it, as it's doing the same job. But be warned that it's not a trivial task and ESCs in kW ranges tend to go for a few hundred dollars (or pounds, since you're calling the cooktops hobs, I guess). There are some designs out there that use an MCU and off-the-shelf parts to build a custom regulator that is capable of PWM adjustments. Here's one I found after a quick search. If you're good with soldering tools and aren't afraid of some MCU work, that's absolutely an option.

P.S. If you're unsure how the induction stoves work in general, Wikipedia article on Inductive Cooking gives a good enough intro. In short, it's a very high power AC generator utilizing an LC resonance. If you can power through concept of impedance and how that relates to damped harmonic oscillators, you're set on theory.

Edited May 3 by K^2

[AckSed]

The dream would be to find an actual commercial induction hob/stovetop that operates like this, no matter what premium I have to pay. (While I'm at it, a microwave too.) Wiring one up myself would be beyond me.

Regardless, thanks for enlightening me.

[darthgently]

Off the top of my head, you could perhaps buffer the bang bang nature of the microwave by having more thermal mass in the oven that will also get heated.  A smoothing capacitor of sorts.  

Beyond that I'm guessing you'd be looking at power MOSFETs or similar and regulating the pulse width of a square wave to the induction coils.

A final thought, what about replacing the logic in the microwave with a faster cycle circuit?  Are there physical reasons to not cycle a microwave faster?  One would need to know that before going down that path.  Maybe a klystron tube can't be safely cycled beyond a certain rate.  I could see it maybe stressing the power supply; the electron analog to water hammer, ha

[K^2]

4 hours ago, AckSed said:

The dream would be to find an actual commercial induction hob/stovetop that operates like this, no matter what premium I have to pay. (While I'm at it, a microwave too.) Wiring one up myself would be beyond me.

Maybe the above at least gives you some ideas for keywords to search, or what to look for feature-wise.

4 hours ago, darthgently said:

A final thought, what about replacing the logic in the microwave with a faster cycle circuit?  Are there physical reasons to not cycle a microwave faster?  One would need to know that before going down that path.  Maybe a klystron tube can't be safely cycled beyond a certain rate.

Microwaves use a magnetron, not a klystorn, but both devices have the same limitation in that the frequency is dependent on the cavity sizes. Moreover, the magnetron in a microwave oven is tuned to maximize absorption by water.

Fortunately, you don't have to get creative with these. While it's difficult to regulate the applied high voltage, which is what really drives the output power, magnetron relies on a heated cathode. Running it cooler results in lower internal current and lower power output. And that you can regulate with just some power mosfets very easily without a risk of burning anything out. There are a lot of microwaves on the market that have adjustable power. Most have a defrost option at least, which runs at partial power. So the problem's always just the lack of features in the control board. You might have to shop around, but you can find a microwave oven with good power adjustment. The caveat is that it might be highly non-linear and you'll have to get the correct power settings by trial and error, but that's just a matter of getting used to it, basically.

[Terwin]

40 minutes ago, K^2 said:

There are a lot of microwaves on the market that have adjustable power. Most have a defrost option at least, which runs at partial power. So the problem's always just the lack of features in the control board. You might have to shop around, but you can find a microwave oven with good power adjustment. The caveat is that it might be highly non-linear and you'll have to get the correct power settings by trial and error, but that's just a matter of getting used to it, basically.

I thought most microwaves running at X% power were actually turning on and off so that they run x% of the time at full power and 100-x% of the time it is off and just giving the heat time to spread out.

[darthgently]

7 hours ago, K^2 said:

Microwaves use a magnetron, not a klystorn

Always thought they were basically different names for same thing.  Thanks for that up.  The more you know!

[K^2]

On 5/3/2024 at 10:38 PM, Terwin said:

I thought most microwaves running at X% power were actually turning on and off so that they run x% of the time at full power and 100-x% of the time it is off and just giving the heat time to spread out.

Honestly, could be? Cathode temperature seems like a more straight forward way, but PWM is always an option, and I can't think of a reason why you couldn't go with short enough pulses where it doesn't matter that much.

I have seen microwaves where the magnetron main power and dish spinner are on the same relay, so you can't modulate power with these without stopping the spinner, but I haven't experimented with how defrost setting works with these, so I can't say anything for sure.

[darthgently]

18 minutes ago, K^2 said:

but PWM is always an option, and I can't think of a reason why you couldn't go with short enough pulses where it doesn't matter that much

This is what I had in mind.  High loads are forgiving and smoothing of square waves if the rate is high enough, typically

[monophonic]

On 5/6/2024 at 12:39 PM, K^2 said:

Honestly, could be? Cathode temperature seems like a more straight forward way, but PWM is always an option, and I can't think of a reason why you couldn't go with short enough pulses where it doesn't matter that much.

I have seen microwaves where the magnetron main power and dish spinner are on the same relay, so you can't modulate power with these without stopping the spinner, but I haven't experimented with how defrost setting works with these, so I can't say anything for sure.

I'm pretty sure the units I've owned all worked with bang-bang magnetron power control. Mind you majority of them have been visually identical other than the front panel, so probably all came from the same factory in china. The "PWM" frequency appears to be on the order of 0.1Hz or so, judging by the cyclical changes in the hum and how melting of butter in the first few seconds is not affected by the power setting. The spinner does not stop though so it must be powered separately from the magnetron. Never took one apart though, and ain't gonna touch the current unit as it still works.

[RunaDacino]

Just how horrible would a thermal nuclear aeorspike engine burning liquid helium be for health, ecosystem and the environment?

 

In MKS WOLF, I found the most optimal transport credit/payload vehicle to be a medium 7.5m tank, a scylla atomic aerospike engine, a 5 m kontainer and a probe core with batteries to 75 km LKO. 

I can't help but wonder, if envirionmental damage was a thing... just 3 launches would horribly irradiate KSC. Is this true, or would a thermal aerospike be "cleaner" provided it doesn't explode.

 

Edited May 26 by RunaDacino

[DDE]

38 minutes ago, RunaDacino said:

Just how horrible would a thermal nuclear aeorspike engine burning liquid helium be for health, ecosystem and the environment?

Depends on the design of NTR's fuel elements, but solid-core engines generally don't leak radioactivity and I don't think helium can be neutron-activated...

So the biggest damage will come from the carbon footprint of natural gas extracted to scavenge this much helium from it.

[RunaDacino]

Ah, I meant hydrogen. Was thinking of multiple things @.@

[RunaDacino]

Why exactly is the orientation of a spacecraft its "attitude"?

[magnemoe]

On 5/26/2024 at 12:58 PM, DDE said:

Depends on the design of NTR's fuel elements, but solid-core engines generally don't leak radioactivity and I don't think helium can be neutron-activated...

So the biggest damage will come from the carbon footprint of natural gas extracted to scavenge this much helium from it.

An reusable NTR rocket has two main problem, first is radiation after use it would make servicing it very hard. People was thinking of nuclear powered planes during the cold war. You could shield the crew of an bomber but not all around. 
Same issue with an rocket on ground. 
Second is accidents an failed landing will be an nasty mess at the best case. 

[JoeSchmuckatelli]

Question about potential energy and solar charging. 

Apologies if this sounds a stoopid question to the educated... But is there a potential energy or balance limit to a portable solar charger's ability to supply power to a phone battery? 

I'm in the second full day of no power and finally got to play with the 28w backpack solar charger I bought a year ago. 

The charger does great until I get to about 50% and then it begins to struggle. 

I know that there are issues about the angle of the sun and etc involved... I'm not asking about solar efficiency.... But the question is more about 'pressure' (as the analog for the correct technical term).  I. E. Is the battery reaching an equalibrium point with the charger such that once it hits 50% there is enough charge in the battery to resist further charging? 

[darthgently]

9 minutes ago, JoeSchmuckatelli said:

Question about potential energy and solar charging. 

Apologies if this sounds a stoopid question to the educated... But is there a potential energy or balance limit to a portable solar charger's ability to supply power to a phone battery? 

I'm in the second full day of no power and finally got to play with the 28w backpack solar charger I bought a year ago. 

The charger does great until I get to about 50% and then it begins to struggle. 

I know that there are issues about the angle of the sun and etc involved... I'm not asking about solar efficiency.... But the question is more about 'pressure' (as the analog for the correct technical term).  I. E. Is the battery reaching an equalibrium point with the charger such that once it hits 50% there is enough charge in the battery to resist further charging? 

Possibly.  The term you might be looking for is voltage, but potential is actually used also.  If you have a voltmeter you could check to see if the proper voltage is maintained under load of charging. 

Another possibility is that in your current situation you ran your phone battery so low and kept trying to use it that the capacity was permanently reduced. 

It may be the charger just doesn't like the quality of the power from the panel and stops doing it's thing at a certain point. 

Also make certain the phone is not sitting in direct sunlight.  Phones will shutdown the charging circuit if you hot (for good reason)

Edited May 27 by darthgently

[AckSed]

8 hours ago, RunaDacino said:

Why exactly is the orientation of a spacecraft its "attitude"?

Digging it out of here: https://en.wikipedia.org/wiki/Spacecraft_attitude_control

The geometry reason is that "Attitude and position fully describe how an object is placed in space."

The practical reason is there is no 'down' in space, and once you leave the orbit of a planet, no real orientation unless your instruments take that planet as your frame of reference.

Attitude is determined through some frame of reference e.g. how far it is from the Sun. You may say your probe is pointing north in space, but relative to what? The plane of the Solar System is not quite flat, especially when you take into account orbits of the gas giants.

Linguistically, "orientation" generally means where it is with a taste of which way it's pointing. "Attitude" only refers to which way it's pointing. It's more precise language.

[Jacke]

3 hours ago, magnemoe said:

An reusable NTR rocket has two main problem, first is radiation after use it would make servicing it very hard. People was thinking of nuclear powered planes during the cold war. You could shield the crew of an bomber but not all around.

NTR rockets with a solid core that are reusable also need to cool down the reactor after a burn.  which means they need to use propellant to cool down the engine.  This ends up providing some extra low-value thrust at the end of a burn, making exacting burns more complex.

[kerbiloid]

Crab Nebula

Associated with the SN_1054 superstar, offically lighted in 1054.

Quote

The event was recorded in contemporary Chinese astronomy, and references to it are also found in a later (13th-century) Japanese document, and in a document from the Islamic world. Furthermore, there are a number of proposed references from European sources recorded in the 15th century, as well as a pictograph associated with the Ancestral Puebloan culture found near the Peñasco Blanco site in New Mexico, United States. The pyramids at Cahokia in the midwestern United States may have been built in response to the supernova's appearance in the sky.^[3]

1. European sources from XV century.

Mwahah! They recalled it 400 years later?

2. Japanese document from XIII century, and not named Islamic document.

Mwahah! It took just 200 years to recall what happened.

3. Amerindian pictograms of unclear origin, let alone dates.

Just no comments.

 

So, actually, the only source telling about the superbright star in the sky, is a Chinese elder scroll (more precisely - 52th volume of the chronology, including the emperors riding flying dragons, and rebel armies of 2 million peasants).

 

Looks, like actually we have absolutely no information on the Crab Nebula birth date, but have a building of related astronomical calculation, based on this thought-out 1054 year.

P.S.
The most tragic part.

This object from kinda 1054 was used for calibration in astronomy, and as a key point in chronology.

Edited May 28 by kerbiloid

[magnemoe]

5 hours ago, kerbiloid said:

Crab Nebula

Associated with the SN_1054 superstar, offically lighted in 1054.

1. European sources from XV century.

Mwahah! They recalled it 400 years later?

2. Japanese document from XIII century, and not named Islamic document.

Mwahah! It took just 200 years to recall what happened.

3. Amerindian pictograms of unclear origin, let alone dates.

Just no comments.

So, actually, the only source telling about the superbright star in the sky, is a Chinese elder scroll (more precisely - 52th volume of the chronology, including the emperors riding flying dragons, and rebel armies of 2 million peasants).

Looks, like actually we have absolutely no information on the Crab Nebula birth date, but have a building of related astronomical calculation, based on this thought-out 1054 year.

P.S.
The most tragic part.

This object from kinda 1054 was used for calibration in astronomy, and as a key point in chronology.

I see two things here, the supernova and the nebula. Chinese documented the supernova, did the Islamic and Japanese describe an nebula or an supernova. 
Europeans was late and might only discover it after telescopes? 

And the Chinese source sound a bit weird, more of an over the top action movie. 

But why is it tragic is used for calibration, except that the nebula would expand.