i been playing a lot of Kerbal Space Program lately. ever since it was in beta i'd go through phases every couple months where i'd build impossible rockets for a week and then get bored when i couldn't easily get to the mun or whatever. this time around i'm putting the effort into actually learning very basic orbital mechanics (read: losing rocket after rocket as i slowly piece together how things work) and it is rewarding as fuck
anyway, my question is this. when we were first starting out with spaceflight, how exactly did the guys doing the theorizing and building the rockets learn about orbital mechanics? i know it's pretty much all predicted by classical physics, but how did they go from theory to practice without blowing up or otherwise losing tens of thousands of test rockets before they had a solid bead on things?
i been playing a lot of Kerbal Space Program lately. ever since it was in beta i'd go through phases every couple months where i'd build impossible rockets for a week and then get bored when i couldn't easily get to the mun or whatever. this time around i'm putting the effort into actually learning very basic orbital mechanics (read: losing rocket after rocket as i slowly piece together how things work) and it is rewarding as fuck
anyway, my question is this. when we were first starting out with spaceflight, how exactly did the guys doing the theorizing and building the rockets learn about orbital mechanics? i know it's pretty much all predicted by classical physics, but how did they go from theory to practice without blowing up or otherwise losing tens of thousands of test rockets before they had a solid bead on things?
The fundamentals of rocketry were known since the 1000s CE when the chinese first started building gunpowder rockets for festives. Going as far back as the founding of the US, liquid fueled rockets were used in wartime, they were just horribly unreliable. WW2 saw the advent of modern rocketry, fueled mostly by Nazi developments. The built the first the first guided missiles in the form of the V1 and V2. By the end of WW2 and the advent of the space age we already had a pretty solid understanding of rocketry and ballistics. You may have seen old timey videos of all the hundreds of failed rocket launches in the early 50s. You know the one where it just blows up on the launchpad or flies sideways into the ground. My and large it took a LOT of trial and error to work out all the mechanics. The very first object we managed to get into orbit had highly unstable orbits and would come crashing down within months. Sputnik for example only stayed in orbit for 3 months before it burned up.
This graph shows the ratio of failures to successes. You might notice that in 1958 the failure rate was nearly half. And this graph does not even show the massive failure rate of the V1 and V2. So, in a nutshell, we basically blew up hundreds of test rockets before we could figure this whole space thing out.
i been playing a lot of Kerbal Space Program lately. ever since it was in beta i'd go through phases every couple months where i'd build impossible rockets for a week and then get bored when i couldn't easily get to the mun or whatever. this time around i'm putting the effort into actually learning very basic orbital mechanics (read: losing rocket after rocket as i slowly piece together how things work) and it is rewarding as fuck
anyway, my question is this. when we were first starting out with spaceflight, how exactly did the guys doing the theorizing and building the rockets learn about orbital mechanics? i know it's pretty much all predicted by classical physics, but how did they go from theory to practice without blowing up or otherwise losing tens of thousands of test rockets before they had a solid bead on things?
There are a couple of very basic things about rocket flight and a ton of super complex things.
Orbital physics were well understood just from planetary orbital mechanics and the rest was super complex math to figure out how to get a rocket in to orbit.
Then there's the Tsiolkovsky rocket equation which is a mathematical proof that rockets can achieve space flight and a simple guide on how to build a rocket and how much load it could carry.
The modern rocket design is the brain child of Sergei Korolev who knowing the limits of the ticket equation figured out a clever way to bypass the limitation of traditional rockets by making it multi staged. Till then everyone was using a single stage rocket based on the V rocket designs, which are fine if you need to bomb London, but it get incredibly hard when you try to acheave orbit. The thing was however that he was working against the clock and with technology that has never been tested, however his engineering technique was really effective though counter intuitive. He planned to build and blow up six rockets. That is to launch them expecting them to blow up, bit of a waste of resources but a perfect way to learn about what unforeseeable things go wrong when you put all the component together. He ended up only blowing up three before he worked out all the bugs. So don't feel bad about blowing up rockets in Kerbal.
One incredibly tough thing to do was engineer a good rocket engine. Early German rockets got away with it by using absurdly high grade metals which made for a finicky and extremely expensive rocket program. Other space programs had to make damn sure that a slight impurity wouldn't cause engine 34 to blow, so they engineered the shit out of it. They also his to make sure that every ounce of fuel was put to good use so engines have to be rather volatile as the best way to do this is to add a lot of oxygen to the mix which as you may know had a way of melting metals.
So yeah, lots of engineering and lots of things exploding.
You are obviously going to spend a lot more sliderule hours if it takes millions of dollars and tens of thousands of man hours to build a thing.
In kerbal it costs tens of minutes.
This risk reward calculation sort of factors into diffrent software development models. Comparing the amount of rigor needed for testing a console game that would never seen an update or a database program that would mostly only have major releases and updates a few times a years to agile saas/web apps that might be updated multiple times a day.
I would still point to things like the SpaceX strut failure as evidence that we still haven't got it entirely figured out. That said: orbital mechanics is easy. You can math that out. The aerodynamic and structural stresses of the thing which turns it into applied orbital dynamics, is insane.
what i meant to ask was when for example NASA was gearing up for the Apollo missions, they had to be pretty much 100% certain of their trajectories and such before they could risk sending dudes to the moon. as far as i know they didn't just brute-force it with dozens of unmanned rockets until they got it right the way i'm doing in KSP, because that would be Expensive, so were they able to math the whole thing out without any special knowledge of how a rocket behaves in vacuum, or did they need telemetry from earlier test launches to understand what they were working with? how did they get a solid enough understanding of the interactions between planets and moons to work out the absurdly complex trajectory Voyager 2 took out of the solar system?
what i meant to ask was when for example NASA was gearing up for the Apollo missions, they had to be pretty much 100% certain of their trajectories and such before they could risk sending dudes to the moon. as far as i know they didn't just brute-force it with dozens of unmanned rockets until they got it right the way i'm doing in KSP, because that would be Expensive, so were they able to math the whole thing out without any special knowledge of how a rocket behaves in vacuum, or did they need telemetry from earlier test launches to understand what they were working with? how did they get a solid enough understanding of the interactions between planets and moons to work out the absurdly complex trajectory Voyager 2 took out of the solar system?
You can work out orbital maneuvers with classical newtonian physics. We had already accurately measured the mass of the moon, we had a decade of sending rockets into orbit before. You might have heard that Apollo 1 burned on the launch pad killing everyone aboard. This was NASA's queue to go back to the drawing board and run a bunch more unmanned tests.
Yeah, all the math and physics were well understood by the time they went in to space, and in addition to that they had the highest end computers on board to do the math for them. Now by today's standards you can probably do all of it on your phone in a fraction of a second, but this stuff would have taken a long time to do with pen and paper back then.
Also to put things in perspective, Apollo 8 was something like the 70th mission to the moon with a ton of fly by, orbit and landers that have gone before it. As always the big issue was adding the useless meatbags on the craft who are heavy and don't do anything other than eat, poop and play golf.
They basically played pen-and-paper KSP until they figured out exactly what they wanted to do. :P
life's a game that you're bound to lose / like using a hammer to pound in screws
fuck up once and you break your thumb / if you're happy at all then you're god damn dumb
that's right we're on a fucked up cruise / God is dead but at least we have booze
bad things happen, no one knows why / the sun burns out and everyone dies
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Andy JoeWe claim the land for the highlord!The AdirondacksRegistered Userregular
Are grounded electrical systems environmentally safe? They're not electrocuting earthworms or important soil bacteria or something, are they?
Are grounded electrical systems environmentally safe? They're not electrocuting earthworms or important soil bacteria or something, are they?
It would be super interesting to conduct some microbial comparisons between the soil around a ground wire and similar soil 20 feet away to see if they differ.
Are grounded electrical systems environmentally safe? They're not electrocuting earthworms or important soil bacteria or something, are they?
In household AC wiring, the ground circuit (green wire or bare copper) and grounding rod is there as a safety feature. It carries no current during normal operation. In case a hot wire (black wire) contacts the metal electrical boxes/conduits, it's there to provide a good conductive current path to ground rather than possibly through your body to ground.
SiliconStew on
Just remember that half the people you meet are below average intelligence.
They basically played pen-and-paper KSP until they figured out exactly what they wanted to do. :P
One of the nice things about P&P KSP is that the system requirements are a smart dude and a pencil.
I submitted an entry to Lego Ideas, and if 10,000 people support me, it'll be turned into an actual Lego set!If you'd like to see and support my submission, follow this link.
Are grounded electrical systems environmentally safe? They're not electrocuting earthworms or important soil bacteria or something, are they?
In household AC wiring, the ground circuit (green wire or bare copper) and grounding rod is there as a safety feature. It carries no current during normal operation. In case a hot wire (black wire) contacts the metal electrical boxes/conduits, it's there to provide a good conductive current path to ground rather than possibly through your body to ground.
Actually that system is there to stop earth potential voltage developing between your house's electrical system and the earth. This can be easily become thousands of volts depending on where you live and how high you live.
The GFCI is there to stop you being electrocuted.
We could easily stop everyone being electrocuted by wiring AC neutral to the case of appliances (and once did) - but that doesn't stop earth potential building up.
Are grounded electrical systems environmentally safe? They're not electrocuting earthworms or important soil bacteria or something, are they?
In household AC wiring, the ground circuit (green wire or bare copper) and grounding rod is there as a safety feature. It carries no current during normal operation. In case a hot wire (black wire) contacts the metal electrical boxes/conduits, it's there to provide a good conductive current path to ground rather than possibly through your body to ground.
Actually that system is there to stop earth potential voltage developing between your house's electrical system and the earth. This can be easily become thousands of volts depending on where you live and how high you live.
The GFCI is there to stop you being electrocuted.
We could easily stop everyone being electrocuted by wiring AC neutral to the case of appliances (and once did) - but that doesn't stop earth potential building up.
Why yes I have been reading about this.
I know that one submarines there is some sort of nutty grounding system that works, but for the life of me I don't remember how it works. I think the original explanation went over my head.
Are grounded electrical systems environmentally safe? They're not electrocuting earthworms or important soil bacteria or something, are they?
In household AC wiring, the ground circuit (green wire or bare copper) and grounding rod is there as a safety feature. It carries no current during normal operation. In case a hot wire (black wire) contacts the metal electrical boxes/conduits, it's there to provide a good conductive current path to ground rather than possibly through your body to ground.
Actually that system is there to stop earth potential voltage developing between your house's electrical system and the earth. This can be easily become thousands of volts depending on where you live and how high you live.
The GFCI is there to stop you being electrocuted.
We could easily stop everyone being electrocuted by wiring AC neutral to the case of appliances (and once did) - but that doesn't stop earth potential building up.
Why yes I have been reading about this.
Pretend I don't know what the potential consequences of earth potential voltage getting too high are.
Are grounded electrical systems environmentally safe? They're not electrocuting earthworms or important soil bacteria or something, are they?
In household AC wiring, the ground circuit (green wire or bare copper) and grounding rod is there as a safety feature. It carries no current during normal operation. In case a hot wire (black wire) contacts the metal electrical boxes/conduits, it's there to provide a good conductive current path to ground rather than possibly through your body to ground.
Actually that system is there to stop earth potential voltage developing between your house's electrical system and the earth. This can be easily become thousands of volts depending on where you live and how high you live.
The GFCI is there to stop you being electrocuted.
We could easily stop everyone being electrocuted by wiring AC neutral to the case of appliances (and once did) - but that doesn't stop earth potential building up.
Why yes I have been reading about this.
Pretend I don't know what the potential consequences of earth potential voltage getting too high are.
when you touch the device you get a thousand volt electric shock
(PSN: Morninglord) (Steam: Morninglord) (WiiU: Morninglord22) I like to record and toss up a lot of random gaming videos here.
Are grounded electrical systems environmentally safe? They're not electrocuting earthworms or important soil bacteria or something, are they?
In household AC wiring, the ground circuit (green wire or bare copper) and grounding rod is there as a safety feature. It carries no current during normal operation. In case a hot wire (black wire) contacts the metal electrical boxes/conduits, it's there to provide a good conductive current path to ground rather than possibly through your body to ground.
Actually that system is there to stop earth potential voltage developing between your house's electrical system and the earth. This can be easily become thousands of volts depending on where you live and how high you live.
The GFCI is there to stop you being electrocuted.
We could easily stop everyone being electrocuted by wiring AC neutral to the case of appliances (and once did) - but that doesn't stop earth potential building up.
Why yes I have been reading about this.
I know that one submarines there is some sort of nutty grounding system that works, but for the life of me I don't remember how it works. I think the original explanation went over my head.
My dad once was setting up a show or something on a Navy ship, and asked where he could plug in a piece of equipment to ground it, or something. The guy pointed to the anchor chain and said "That's sitting in about 250 billion gallons of salt water. There's your ground."
Are grounded electrical systems environmentally safe? They're not electrocuting earthworms or important soil bacteria or something, are they?
In household AC wiring, the ground circuit (green wire or bare copper) and grounding rod is there as a safety feature. It carries no current during normal operation. In case a hot wire (black wire) contacts the metal electrical boxes/conduits, it's there to provide a good conductive current path to ground rather than possibly through your body to ground.
Actually that system is there to stop earth potential voltage developing between your house's electrical system and the earth. This can be easily become thousands of volts depending on where you live and how high you live.
The GFCI is there to stop you being electrocuted.
We could easily stop everyone being electrocuted by wiring AC neutral to the case of appliances (and once did) - but that doesn't stop earth potential building up.
Why yes I have been reading about this.
Pretend I don't know what the potential consequences of earth potential voltage getting too high are.
Imagine a twinkie, this twinkie represents the standard household circuit voltage of your house. According to some readings the potential voltage developing between your house's electrical system and the earth would make a twinky that is easily the size of a sticky bun.
I don't know where I'm going with this, but i'm pretty sure that all your electric appliances would short the fuck out amd I need to get me a snack or something.
Are grounded electrical systems environmentally safe? They're not electrocuting earthworms or important soil bacteria or something, are they?
In household AC wiring, the ground circuit (green wire or bare copper) and grounding rod is there as a safety feature. It carries no current during normal operation. In case a hot wire (black wire) contacts the metal electrical boxes/conduits, it's there to provide a good conductive current path to ground rather than possibly through your body to ground.
Actually that system is there to stop earth potential voltage developing between your house's electrical system and the earth. This can be easily become thousands of volts depending on where you live and how high you live.
The GFCI is there to stop you being electrocuted.
We could easily stop everyone being electrocuted by wiring AC neutral to the case of appliances (and once did) - but that doesn't stop earth potential building up.
Why yes I have been reading about this.
Pretend I don't know what the potential consequences of earth potential voltage getting too high are.
when you touch the device you get a thousand volt electric shock
Yeaaah, but at what current?
They moistly come out at night, moistly.
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MorninglordI'm tired of being Batman,so today I'll be Owl.Registered Userregular
edited November 2015
No idea.
I spent fifteen minutes looking it up on the wiki. I'm not an expert.
I would imagine it isn't a healthy level of current or there wouldn't be such a hullabaloo about it.
The wiki entry for Earth Potential Rise has the relevant formula on it, so you can calculate the current if you are so inclined.
Morninglord on
(PSN: Morninglord) (Steam: Morninglord) (WiiU: Morninglord22) I like to record and toss up a lot of random gaming videos here.
Are grounded electrical systems environmentally safe? They're not electrocuting earthworms or important soil bacteria or something, are they?
In household AC wiring, the ground circuit (green wire or bare copper) and grounding rod is there as a safety feature. It carries no current during normal operation. In case a hot wire (black wire) contacts the metal electrical boxes/conduits, it's there to provide a good conductive current path to ground rather than possibly through your body to ground.
Actually that system is there to stop earth potential voltage developing between your house's electrical system and the earth. This can be easily become thousands of volts depending on where you live and how high you live.
The GFCI is there to stop you being electrocuted.
We could easily stop everyone being electrocuted by wiring AC neutral to the case of appliances (and once did) - but that doesn't stop earth potential building up.
Why yes I have been reading about this.
Yes, but to stop that charge buildup only requires the ground rod to the electrical panel's neutral circuit. And normally doesn't really represent a significant current flow because the charge is continuously dissipated without a chance to build up.
The ground wiring throughout the house is for electrical safety. GFI outlets are only required near sinks and in bathrooms because the water and/or pipes makes a very easily accessible path to ground that your body can come into contact with. GFI is extra protection on top of the protection afforded by having all the outlets and switches grounded as it is more sensitive to potential hazardous situations than just the circuit breakers.
All those electrical devices with a 3 prong plug do have their chassis connected to the ground circuit for safety.
Just remember that half the people you meet are below average intelligence.
Are grounded electrical systems environmentally safe? They're not electrocuting earthworms or important soil bacteria or something, are they?
In household AC wiring, the ground circuit (green wire or bare copper) and grounding rod is there as a safety feature. It carries no current during normal operation. In case a hot wire (black wire) contacts the metal electrical boxes/conduits, it's there to provide a good conductive current path to ground rather than possibly through your body to ground.
Actually that system is there to stop earth potential voltage developing between your house's electrical system and the earth. This can be easily become thousands of volts depending on where you live and how high you live.
The GFCI is there to stop you being electrocuted.
We could easily stop everyone being electrocuted by wiring AC neutral to the case of appliances (and once did) - but that doesn't stop earth potential building up.
Why yes I have been reading about this.
Pretend I don't know what the potential consequences of earth potential voltage getting too high are.
when you touch the device you get a thousand volt electric shock
Yeaaah, but at what current?
It'll be the result of capacitance/inductance of your entire house's electrical system, and depend on where and how close to the earth you are relative to that. But it does mean possibly a lot if you don't have good points of leakage to ground - which is why we have earth grounding in our electrical systems.
Are grounded electrical systems environmentally safe? They're not electrocuting earthworms or important soil bacteria or something, are they?
In household AC wiring, the ground circuit (green wire or bare copper) and grounding rod is there as a safety feature. It carries no current during normal operation. In case a hot wire (black wire) contacts the metal electrical boxes/conduits, it's there to provide a good conductive current path to ground rather than possibly through your body to ground.
Actually that system is there to stop earth potential voltage developing between your house's electrical system and the earth. This can be easily become thousands of volts depending on where you live and how high you live.
The GFCI is there to stop you being electrocuted.
We could easily stop everyone being electrocuted by wiring AC neutral to the case of appliances (and once did) - but that doesn't stop earth potential building up.
Why yes I have been reading about this.
Yes, but to stop that charge buildup only requires the ground rod to the electrical panel's neutral circuit. And normally doesn't really represent a significant current flow because the charge is continuously dissipated without a chance to build up.
The ground wiring throughout the house is for electrical safety. GFI outlets are only required near sinks and in bathrooms because the water and/or pipes makes a very easily accessible path to ground that your body can come into contact with. GFI is extra protection on top of the protection afforded by having all the outlets and switches grounded as it is more sensitive to potential hazardous situations than just the circuit breakers.
All those electrical devices with a 3 prong plug do have their chassis connected to the ground circuit for safety.
I agree, I just think the reasons are kind of interesting - i.e. once upon a time it was perfectly safe to handle 240VAC wiring without caring which was 'hot' or 'neutral' because both meant the same thing - there's a 240VAC difference, because you're floating relative to earth so it's just to the power station. The only issue is bridging the circuit.
Then you get earth potential problems, so you fix it by wiring one side to earth locally - but you've made all nearby humans part of the circuit possibly. So you have to enforce the hot/neutral distinction to make sure people don't wire the grounded side to appliance chassis or touch the hot wire (which is ungrounded).
But since you can't trust people and appliance makers not to be idiots or install wall sockets backwards, we get 3-prong sockets, and make "earth" wholly distinct.
Hence why you can't wire AC neutral to the case - because you can't trust everything else in the system, so it's only safe to do if you make the circuit float relative to earth which gives you the potential build up problems.
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MorninglordI'm tired of being Batman,so today I'll be Owl.Registered Userregular
I wish I knew enough about electricity that I could follow that. I kind of get it but I'd have to sit down and really put my thinking cap on to connect it all together.
(PSN: Morninglord) (Steam: Morninglord) (WiiU: Morninglord22) I like to record and toss up a lot of random gaming videos here.
Don't a lot of rectifiers, signal transformers, antennas and shielded cables make use of the extra ground plug to dissipate... Kinda crap electrons that get where they shouldn't and fuck with signals that would do bat things to sensitive equipment?
Like if you ran those to neutral you... uh... would lack a 'reference ground' or something. Same as the extra little cable on an oscilloscope probe?
I thought that was a thing.
Edit: no, reference ground is just DC version of neutral. Earth ground is the ground pin garbage voltage sink.
redx on
They moistly come out at night, moistly.
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MorninglordI'm tired of being Batman,so today I'll be Owl.Registered Userregular
Don't a lot of rectifiers, signal transformers, antennas and shielded cables make use of the extra ground plug to dissipate... Kinda crap electrons that get where they shouldn't and fuck with signals that would do bat things to sensitive equipment?
(PSN: Morninglord) (Steam: Morninglord) (WiiU: Morninglord22) I like to record and toss up a lot of random gaming videos here.
Another fun bit about early rocket development: even without 'good' computers, it was possible to simulate designs ahead of time due to a bizarre common thread in certain physical systems. The use of Analogous systems - the two most common ones being Masses, Springs, & Dampers (for physical objects) and their equivalence to Inductance, Capacitance, & Resistance (for electrical systems) respectively; two more similar relationships exist for Thermal and Fluid systems. The fun part is, you can simulate one analogous system with any other system, so you can literally simulate a car's suspension with analog electrical circuits... or in this instance, incredibly complex, huge rockets.
Are grounded electrical systems environmentally safe? They're not electrocuting earthworms or important soil bacteria or something, are they?
In household AC wiring, the ground circuit (green wire or bare copper) and grounding rod is there as a safety feature. It carries no current during normal operation. In case a hot wire (black wire) contacts the metal electrical boxes/conduits, it's there to provide a good conductive current path to ground rather than possibly through your body to ground.
Actually that system is there to stop earth potential voltage developing between your house's electrical system and the earth. This can be easily become thousands of volts depending on where you live and how high you live.
The GFCI is there to stop you being electrocuted.
We could easily stop everyone being electrocuted by wiring AC neutral to the case of appliances (and once did) - but that doesn't stop earth potential building up.
Why yes I have been reading about this.
Yes, but to stop that charge buildup only requires the ground rod to the electrical panel's neutral circuit. And normally doesn't really represent a significant current flow because the charge is continuously dissipated without a chance to build up.
The ground wiring throughout the house is for electrical safety. GFI outlets are only required near sinks and in bathrooms because the water and/or pipes makes a very easily accessible path to ground that your body can come into contact with. GFI is extra protection on top of the protection afforded by having all the outlets and switches grounded as it is more sensitive to potential hazardous situations than just the circuit breakers.
All those electrical devices with a 3 prong plug do have their chassis connected to the ground circuit for safety.
I agree, I just think the reasons are kind of interesting - i.e. once upon a time it was perfectly safe to handle 240VAC wiring without caring which was 'hot' or 'neutral' because both meant the same thing - there's a 240VAC difference, because you're floating relative to earth so it's just to the power station. The only issue is bridging the circuit.
Then you get earth potential problems, so you fix it by wiring one side to earth locally - but you've made all nearby humans part of the circuit possibly. So you have to enforce the hot/neutral distinction to make sure people don't wire the grounded side to appliance chassis or touch the hot wire (which is ungrounded).
But since you can't trust people and appliance makers not to be idiots or install wall sockets backwards, we get 3-prong sockets, and make "earth" wholly distinct.
Hence why you can't wire AC neutral to the case - because you can't trust everything else in the system, so it's only safe to do if you make the circuit float relative to earth which gives you the potential build up problems.
Except, it essentially is wired to the case, only back at the main panel. The neutral is never allowed to float, and it will wired to the ground at the main panel. I should mention that this primarily applies to the US and Canada and I'm not sure what the rest of the world uses. Household wiring is typically split-phase 240V with the neutral on the center tap. Industrial systems are typically Delta 3-phase on the distribution (MV/HV) side, and Wye 3-phase (MV/LV) on the equipment side with a neutral center tap.
Steam - Synthetic Violence | XBOX Live - Cannonfuse | PSN - CastleBravo | Twitch - SoggybiscuitPA
Are grounded electrical systems environmentally safe? They're not electrocuting earthworms or important soil bacteria or something, are they?
In household AC wiring, the ground circuit (green wire or bare copper) and grounding rod is there as a safety feature. It carries no current during normal operation. In case a hot wire (black wire) contacts the metal electrical boxes/conduits, it's there to provide a good conductive current path to ground rather than possibly through your body to ground.
Actually that system is there to stop earth potential voltage developing between your house's electrical system and the earth. This can be easily become thousands of volts depending on where you live and how high you live.
The GFCI is there to stop you being electrocuted.
We could easily stop everyone being electrocuted by wiring AC neutral to the case of appliances (and once did) - but that doesn't stop earth potential building up.
Why yes I have been reading about this.
Yes, but to stop that charge buildup only requires the ground rod to the electrical panel's neutral circuit. And normally doesn't really represent a significant current flow because the charge is continuously dissipated without a chance to build up.
The ground wiring throughout the house is for electrical safety. GFI outlets are only required near sinks and in bathrooms because the water and/or pipes makes a very easily accessible path to ground that your body can come into contact with. GFI is extra protection on top of the protection afforded by having all the outlets and switches grounded as it is more sensitive to potential hazardous situations than just the circuit breakers.
All those electrical devices with a 3 prong plug do have their chassis connected to the ground circuit for safety.
I agree, I just think the reasons are kind of interesting - i.e. once upon a time it was perfectly safe to handle 240VAC wiring without caring which was 'hot' or 'neutral' because both meant the same thing - there's a 240VAC difference, because you're floating relative to earth so it's just to the power station. The only issue is bridging the circuit.
Then you get earth potential problems, so you fix it by wiring one side to earth locally - but you've made all nearby humans part of the circuit possibly. So you have to enforce the hot/neutral distinction to make sure people don't wire the grounded side to appliance chassis or touch the hot wire (which is ungrounded).
But since you can't trust people and appliance makers not to be idiots or install wall sockets backwards, we get 3-prong sockets, and make "earth" wholly distinct.
Hence why you can't wire AC neutral to the case - because you can't trust everything else in the system, so it's only safe to do if you make the circuit float relative to earth which gives you the potential build up problems.
Except, it essentially is wired to the case, only back at the main panel. The neutral is never allowed to float, and it will wired to the ground at the main panel. I should mention that this primarily applies to the US and Canada and I'm not sure what the rest of the world uses. Household wiring is typically split-phase 240V with the neutral on the center tap. Industrial systems are typically Delta 3-phase on the distribution (MV/HV) side, and Wye 3-phase (MV/LV) on the equipment side with a neutral center tap.
That was badly worded, what I meant was: you could wire "neutral" directly to the case, but since some idiot might've got around swapping your electrical sockets around for live/neutral, if you built an appliance on this assumption and plugged it in, the moment you touched something wired correctly (or the actual earth) you'd short mains to ground via yourself.
But theoretically it *would* be safe if neutral floated, but that engenders other issues so instead we do the 3-prong thing.
Are grounded electrical systems environmentally safe? They're not electrocuting earthworms or important soil bacteria or something, are they?
In household AC wiring, the ground circuit (green wire or bare copper) and grounding rod is there as a safety feature. It carries no current during normal operation. In case a hot wire (black wire) contacts the metal electrical boxes/conduits, it's there to provide a good conductive current path to ground rather than possibly through your body to ground.
Actually that system is there to stop earth potential voltage developing between your house's electrical system and the earth. This can be easily become thousands of volts depending on where you live and how high you live.
The GFCI is there to stop you being electrocuted.
We could easily stop everyone being electrocuted by wiring AC neutral to the case of appliances (and once did) - but that doesn't stop earth potential building up.
Why yes I have been reading about this.
Yes, but to stop that charge buildup only requires the ground rod to the electrical panel's neutral circuit. And normally doesn't really represent a significant current flow because the charge is continuously dissipated without a chance to build up.
The ground wiring throughout the house is for electrical safety. GFI outlets are only required near sinks and in bathrooms because the water and/or pipes makes a very easily accessible path to ground that your body can come into contact with. GFI is extra protection on top of the protection afforded by having all the outlets and switches grounded as it is more sensitive to potential hazardous situations than just the circuit breakers.
All those electrical devices with a 3 prong plug do have their chassis connected to the ground circuit for safety.
I agree, I just think the reasons are kind of interesting - i.e. once upon a time it was perfectly safe to handle 240VAC wiring without caring which was 'hot' or 'neutral' because both meant the same thing - there's a 240VAC difference, because you're floating relative to earth so it's just to the power station. The only issue is bridging the circuit.
Then you get earth potential problems, so you fix it by wiring one side to earth locally - but you've made all nearby humans part of the circuit possibly. So you have to enforce the hot/neutral distinction to make sure people don't wire the grounded side to appliance chassis or touch the hot wire (which is ungrounded).
But since you can't trust people and appliance makers not to be idiots or install wall sockets backwards, we get 3-prong sockets, and make "earth" wholly distinct.
Hence why you can't wire AC neutral to the case - because you can't trust everything else in the system, so it's only safe to do if you make the circuit float relative to earth which gives you the potential build up problems.
Except, it essentially is wired to the case, only back at the main panel. The neutral is never allowed to float, and it will wired to the ground at the main panel. I should mention that this primarily applies to the US and Canada and I'm not sure what the rest of the world uses. Household wiring is typically split-phase 240V with the neutral on the center tap. Industrial systems are typically Delta 3-phase on the distribution (MV/HV) side, and Wye 3-phase (MV/LV) on the equipment side with a neutral center tap.
That was badly worded, what I meant was: you could wire "neutral" directly to the case, but since some idiot might've got around swapping your electrical sockets around for live/neutral, if you built an appliance on this assumption and plugged it in, the moment you touched something wired correctly (or the actual earth) you'd short mains to ground via yourself.
But theoretically it *would* be safe if neutral floated, but that engenders other issues so instead we do the 3-prong thing.
Ahh okay, I got you now.
Floating neutrals are the bane of my existence.
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Andy JoeWe claim the land for the highlord!The AdirondacksRegistered Userregular
Are grounded electrical systems environmentally safe? They're not electrocuting earthworms or important soil bacteria or something, are they?
In household AC wiring, the ground circuit (green wire or bare copper) and grounding rod is there as a safety feature. It carries no current during normal operation. In case a hot wire (black wire) contacts the metal electrical boxes/conduits, it's there to provide a good conductive current path to ground rather than possibly through your body to ground.
Actually that system is there to stop earth potential voltage developing between your house's electrical system and the earth. This can be easily become thousands of volts depending on where you live and how high you live.
The GFCI is there to stop you being electrocuted.
We could easily stop everyone being electrocuted by wiring AC neutral to the case of appliances (and once did) - but that doesn't stop earth potential building up.
Why yes I have been reading about this.
Pretend I don't know what the potential consequences of earth potential voltage getting too high are.
when you touch the device you get a thousand volt electric shock
I figured it'd be either that or "Your house burns down."
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i been playing a lot of Kerbal Space Program lately. ever since it was in beta i'd go through phases every couple months where i'd build impossible rockets for a week and then get bored when i couldn't easily get to the mun or whatever. this time around i'm putting the effort into actually learning very basic orbital mechanics (read: losing rocket after rocket as i slowly piece together how things work) and it is rewarding as fuck
anyway, my question is this. when we were first starting out with spaceflight, how exactly did the guys doing the theorizing and building the rockets learn about orbital mechanics? i know it's pretty much all predicted by classical physics, but how did they go from theory to practice without blowing up or otherwise losing tens of thousands of test rockets before they had a solid bead on things?
hitting hot metal with hammers
The fundamentals of rocketry were known since the 1000s CE when the chinese first started building gunpowder rockets for festives. Going as far back as the founding of the US, liquid fueled rockets were used in wartime, they were just horribly unreliable. WW2 saw the advent of modern rocketry, fueled mostly by Nazi developments. The built the first the first guided missiles in the form of the V1 and V2. By the end of WW2 and the advent of the space age we already had a pretty solid understanding of rocketry and ballistics. You may have seen old timey videos of all the hundreds of failed rocket launches in the early 50s. You know the one where it just blows up on the launchpad or flies sideways into the ground. My and large it took a LOT of trial and error to work out all the mechanics. The very first object we managed to get into orbit had highly unstable orbits and would come crashing down within months. Sputnik for example only stayed in orbit for 3 months before it burned up.
This graph shows the ratio of failures to successes. You might notice that in 1958 the failure rate was nearly half. And this graph does not even show the massive failure rate of the V1 and V2. So, in a nutshell, we basically blew up hundreds of test rockets before we could figure this whole space thing out.
There are a couple of very basic things about rocket flight and a ton of super complex things.
Orbital physics were well understood just from planetary orbital mechanics and the rest was super complex math to figure out how to get a rocket in to orbit.
Then there's the Tsiolkovsky rocket equation which is a mathematical proof that rockets can achieve space flight and a simple guide on how to build a rocket and how much load it could carry.
The modern rocket design is the brain child of Sergei Korolev who knowing the limits of the ticket equation figured out a clever way to bypass the limitation of traditional rockets by making it multi staged. Till then everyone was using a single stage rocket based on the V rocket designs, which are fine if you need to bomb London, but it get incredibly hard when you try to acheave orbit. The thing was however that he was working against the clock and with technology that has never been tested, however his engineering technique was really effective though counter intuitive. He planned to build and blow up six rockets. That is to launch them expecting them to blow up, bit of a waste of resources but a perfect way to learn about what unforeseeable things go wrong when you put all the component together. He ended up only blowing up three before he worked out all the bugs. So don't feel bad about blowing up rockets in Kerbal.
One incredibly tough thing to do was engineer a good rocket engine. Early German rockets got away with it by using absurdly high grade metals which made for a finicky and extremely expensive rocket program. Other space programs had to make damn sure that a slight impurity wouldn't cause engine 34 to blow, so they engineered the shit out of it. They also his to make sure that every ounce of fuel was put to good use so engines have to be rather volatile as the best way to do this is to add a lot of oxygen to the mix which as you may know had a way of melting metals.
So yeah, lots of engineering and lots of things exploding.
In kerbal it costs tens of minutes.
This risk reward calculation sort of factors into diffrent software development models. Comparing the amount of rigor needed for testing a console game that would never seen an update or a database program that would mostly only have major releases and updates a few times a years to agile saas/web apps that might be updated multiple times a day.
what i meant to ask was when for example NASA was gearing up for the Apollo missions, they had to be pretty much 100% certain of their trajectories and such before they could risk sending dudes to the moon. as far as i know they didn't just brute-force it with dozens of unmanned rockets until they got it right the way i'm doing in KSP, because that would be Expensive, so were they able to math the whole thing out without any special knowledge of how a rocket behaves in vacuum, or did they need telemetry from earlier test launches to understand what they were working with? how did they get a solid enough understanding of the interactions between planets and moons to work out the absurdly complex trajectory Voyager 2 took out of the solar system?
hitting hot metal with hammers
You can work out orbital maneuvers with classical newtonian physics. We had already accurately measured the mass of the moon, we had a decade of sending rockets into orbit before. You might have heard that Apollo 1 burned on the launch pad killing everyone aboard. This was NASA's queue to go back to the drawing board and run a bunch more unmanned tests.
https://en.wikipedia.org/wiki/List_of_Apollo_missions
As you can see, there were actually a lot more unmanned test flights than there were manned.
Also to put things in perspective, Apollo 8 was something like the 70th mission to the moon with a ton of fly by, orbit and landers that have gone before it. As always the big issue was adding the useless meatbags on the craft who are heavy and don't do anything other than eat, poop and play golf.
They basically played pen-and-paper KSP until they figured out exactly what they wanted to do. :P
fuck up once and you break your thumb / if you're happy at all then you're god damn dumb
that's right we're on a fucked up cruise / God is dead but at least we have booze
bad things happen, no one knows why / the sun burns out and everyone dies
Lighting rods will make glass.
So, it depends?
It would be super interesting to conduct some microbial comparisons between the soil around a ground wire and similar soil 20 feet away to see if they differ.
In household AC wiring, the ground circuit (green wire or bare copper) and grounding rod is there as a safety feature. It carries no current during normal operation. In case a hot wire (black wire) contacts the metal electrical boxes/conduits, it's there to provide a good conductive current path to ground rather than possibly through your body to ground.
One of the nice things about P&P KSP is that the system requirements are a smart dude and a pencil.
Actually that system is there to stop earth potential voltage developing between your house's electrical system and the earth. This can be easily become thousands of volts depending on where you live and how high you live.
The GFCI is there to stop you being electrocuted.
We could easily stop everyone being electrocuted by wiring AC neutral to the case of appliances (and once did) - but that doesn't stop earth potential building up.
Why yes I have been reading about this.
I know that one submarines there is some sort of nutty grounding system that works, but for the life of me I don't remember how it works. I think the original explanation went over my head.
Pretend I don't know what the potential consequences of earth potential voltage getting too high are.
well i got a pencil!
does that get me halfway to the moon?
sadly the pencil is only a catalyst
when you touch the device you get a thousand volt electric shock
My dad once was setting up a show or something on a Navy ship, and asked where he could plug in a piece of equipment to ground it, or something. The guy pointed to the anchor chain and said "That's sitting in about 250 billion gallons of salt water. There's your ground."
Imagine a twinkie, this twinkie represents the standard household circuit voltage of your house. According to some readings the potential voltage developing between your house's electrical system and the earth would make a twinky that is easily the size of a sticky bun.
I don't know where I'm going with this, but i'm pretty sure that all your electric appliances would short the fuck out amd I need to get me a snack or something.
Yeaaah, but at what current?
I spent fifteen minutes looking it up on the wiki. I'm not an expert.
I would imagine it isn't a healthy level of current or there wouldn't be such a hullabaloo about it.
The wiki entry for Earth Potential Rise has the relevant formula on it, so you can calculate the current if you are so inclined.
Yes, but to stop that charge buildup only requires the ground rod to the electrical panel's neutral circuit. And normally doesn't really represent a significant current flow because the charge is continuously dissipated without a chance to build up.
The ground wiring throughout the house is for electrical safety. GFI outlets are only required near sinks and in bathrooms because the water and/or pipes makes a very easily accessible path to ground that your body can come into contact with. GFI is extra protection on top of the protection afforded by having all the outlets and switches grounded as it is more sensitive to potential hazardous situations than just the circuit breakers.
All those electrical devices with a 3 prong plug do have their chassis connected to the ground circuit for safety.
It'll be the result of capacitance/inductance of your entire house's electrical system, and depend on where and how close to the earth you are relative to that. But it does mean possibly a lot if you don't have good points of leakage to ground - which is why we have earth grounding in our electrical systems.
I agree, I just think the reasons are kind of interesting - i.e. once upon a time it was perfectly safe to handle 240VAC wiring without caring which was 'hot' or 'neutral' because both meant the same thing - there's a 240VAC difference, because you're floating relative to earth so it's just to the power station. The only issue is bridging the circuit.
Then you get earth potential problems, so you fix it by wiring one side to earth locally - but you've made all nearby humans part of the circuit possibly. So you have to enforce the hot/neutral distinction to make sure people don't wire the grounded side to appliance chassis or touch the hot wire (which is ungrounded).
But since you can't trust people and appliance makers not to be idiots or install wall sockets backwards, we get 3-prong sockets, and make "earth" wholly distinct.
Hence why you can't wire AC neutral to the case - because you can't trust everything else in the system, so it's only safe to do if you make the circuit float relative to earth which gives you the potential build up problems.
Like if you ran those to neutral you... uh... would lack a 'reference ground' or something. Same as the extra little cable on an oscilloscope probe?
I thought that was a thing.
Edit: no, reference ground is just DC version of neutral. Earth ground is the ground pin garbage voltage sink.
Except, it essentially is wired to the case, only back at the main panel. The neutral is never allowed to float, and it will wired to the ground at the main panel. I should mention that this primarily applies to the US and Canada and I'm not sure what the rest of the world uses. Household wiring is typically split-phase 240V with the neutral on the center tap. Industrial systems are typically Delta 3-phase on the distribution (MV/HV) side, and Wye 3-phase (MV/LV) on the equipment side with a neutral center tap.
That was badly worded, what I meant was: you could wire "neutral" directly to the case, but since some idiot might've got around swapping your electrical sockets around for live/neutral, if you built an appliance on this assumption and plugged it in, the moment you touched something wired correctly (or the actual earth) you'd short mains to ground via yourself.
But theoretically it *would* be safe if neutral floated, but that engenders other issues so instead we do the 3-prong thing.
Ahh okay, I got you now.
Floating neutrals are the bane of my existence.
I figured it'd be either that or "Your house burns down."
Yes. While ground is often used for both, they are not technically the same thing. Neutral (aka Common) can be grounded, but Ground is not neutral.
http://www.popularmechanics.com/science/energy/a18274/plants-electrified-scientists-just-grew-conductive-wires-inside-roses/
now they can conduct fucking electricity!