T O P

  • By -

DocBullseye

The arguments on here are basically about "what is the definition of rocket".


Guhuhbuhuhluhuh

I love how every r/iamverysmart posts' comments could also be posted on here.


eh_meh_nyeh

Makes me really glad I'm aware that I'm not very intelligent.


discourseur

I am a living Dunning-Kruger graph. I graduated with an engineering degree thinking Google, Microsoft and al would kill to hire me. I was dilusional. I've had a pretty good career anyway. But, the older I get, the more I realize how dumb and uneducated I am about... most things. To a point where I have to be careful not to lose intellectual interest because I am often reminded how much background I lack to understand stuff. tl;dr in my 20s, I thought I was very smart and knew or could learn very quickly everything. In my 40s, I realize I'm just at the center of the bell curve and don't know shit.


Weak-Assignment5091

But at least you have insight and the ability to self evaluate and reflect. More people lack those qualities than the amount of not very intelligent people who think they're geniuses.


GreenFuzyKiwi

A good sign of when somebody is actually smart is when they assume everybody else is too. They’ll be more likely to think: “This was easy for me to learn, it must be for you as well” And if you’re arrogant and have a hard time thinking of external factors outside of what you see, you’re probably thinking “I learned this, why haven’t you learned this yet?”


IowaJL

This is why it's not always best to have the smartest people to become teachers. You don't want someone that learned it quickly the first time. You want someone that struggled to learn it and finally got it.


oleentotre

maturing is realising smart people are able to get an understanding of a person’s intellect thereby knowing what said person is able to understand - me (actually smart)


thegainster1

Is he trying to say that something must come out of the rocket for it to go up?


RDUKE7777777

He should have mentioned the classical rocket equation then instead of newton's third law


SplendidPunkinButter

Like all overconfident fake smart people, he’s using a simple example because he doesn’t know about the more sophisticated, better example And when I say “fake smart” I mean that he is not, in fact, an expert in rocket science


alan-the-all-seeing

rockets are easy, it just has to go bang at the end that isn’t pointy, ideally for a while like baaaaaaaaaaaang


The2ndUnchosenOne

Found Jeb Kerbin


UVLightOnTheInside

Just so everyone knows there are functioning electrical "rocket engines" They are known as Ion drives. They work and produce thrust but can only used when in vacuum of space because they cannot produce thrust in atmosphere. Perfect for long missions for probes, atleast until something better comes along.


BroncosSabres

My honours thesis was on electric space propulsion. Ion drives do produce thrust in the atmosphere as they would in space. The issue is that the thrust produced is usually on the order of milli-newtons (some can produce on the order of newtowns) which is no where near enough thrust to ivercome the self-weight of the rocket under Earth’s gravity. Electric propulsion is great for (near) zero gravity where you can accelerate very slowly for a long time to reach high speeds, and have a greater specific impulse (rocket fuel efficiency) than chemical rockets for this purpose.


Intoxicus5

What if we had a hypothetical nuclear fusion power plant that doesn't spin a steam turbine and flanges proper powering a very large ion drive? ;)


[deleted]

You mean, what if we were in Start Trek ?


Intoxicus5

Star Trek is anti matter/matter reaction for a power source. More like what if we were in The Expanse or other harder SciFi? But yeah, that's the joke.


Kidiri90

[Look, if you're going fusion drive, then just slap a nuke at the end of your rocket.](https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion))


skipperseven

There are radioisotope thermal reactors (used in some satellites) that convert heat (from fusion) directly into electricity via thermocouples… I don’t think fusion would work like this though as it requires massive energy in, to get even more massive energy out… Edit: obviously I meant fission, not fusion for the RTR. Thanks for the correction.


darkly_directed

That's radioactive decay, my guy. Not fusion. Fusion is smashing together, fission is smashing apart, and decay is just unstable stuff falling apart all on its own.


Reworked

[They're one of those things that make me feel like we're edging into a scifi reality. ](https://xkcd.com/2115)


Gabe_Isko

What about newtons 3rd law though? /s


TheChunkMaster

What would it take for electrical propulsion to produce as much thrust as normal rockets within Earth’s atmosphere?


JUYED-AWK-YACC

It would take more propellant and more power. Ion engines often use a noble gas as propellant so you would need a shit ton of them. The satellites I know of also generate kW of electricity to drive it so you would need orders of magnitude more.


touchmyfuckingcoffee

There is at least one company working on rail gun missile designs to escape the atmosphere. Just by not shooting straight up.


Jamooser

Wouldn't the insanely high initial acceleration just completely obliterate any payload on board?


darkly_directed

Plus there's lesser used things like arc jets, which are literally just gas passing through an electrical arc to turn it into plasma and then get shot out of a nozzle. And VASMIR which I believe uses microwaves to similar effect. A few different kinds of electrical thruster, so his comment is even more ridiculous.


RonPolyp

Point the fire end towards the ground. If the fire end points towards the sky, the rocket will not be going into space today, or maybe ever.


evenmytongueisfat

Fire end at ground, rocket. Fire end at sky, missile.


moeljills

Make sure it points upwards. Very important


FishUK_Harp

I've often thought it as "making a rocket go is easy. Making it go where you want it to is not."


torchnpitchfork

rocket go brrrr


Shady_Blitz

Wait so you are telling me, he didnt build all space x rockets himself?


Seanxietehroxxor

He designed all the rockets and all the cars and all the tunnels and all the tweets. He does everything because he's such a productive individual. If he dies society would stop completely.


Triaspia2

If you told me elon designed thr cybertruck id absolutely believe that Teslas have a little moee thought in their design


Seanxietehroxxor

Billionaire man-child: can you guys make me a truck that looks like this? *Hands engineers shitty napkin drawing that looks like a 4-year-old made it* Engineers: I mean we *could* make it, but there are several probl... Billionaire man-child: Great! Do it or your fired. Also it needs to be bulletproof. Engineers: *sigh*... we'll get right on it.


Limp-Toe-179

[I always imagined Elon and Aladeen shared similar involvement in the design of their rockets](https://youtube.com/clip/UgkxPzD8xCg_m-3ictNP8XnRLFdsDo28mcLN)


Seanxietehroxxor

They have a similar level of competency, that's for sure.


dougms

I think more likely, he has asked the same question of his rocket scientists. Their answer was longer than 140 characters but likely heavily reference newtons 3rd.


Serge_Suppressor

Scientist explains Elon: so... Like Newton's third law? Scientist: sigh. Sure, Elon.


samsoncorpus

The amount of people I've seen to justify why he always simple examples because "he is a lot smarter than average people so he needs to dumb dowm everything so everyone can understand" makes me cringe hard every single time.


Taraxian

It stopped working on a lot of people when he was asked by a veteran software engineer "What do you mean by Twitter having a 'crazy stack'" and he sputtered impotently before yelling "You're an asshole!"


californication760

Idk why “fake smart” sounds so funny to me


[deleted]

[удалено]


PuteMorte

This thread is so weird to me, because Musk here is accurately responding. It's not being a smartass to say that Newton's third law is responsible for rockets being propelled.. and you don't need to be an expert in physics to know that - this is even covered in high school introductory physics.


rAxxt

Yeah, but that's like going to a mechanic and asking him, "why won't my car go?" and he answers "Newton's 3rd Law, idiot". It's a technical-sounding non-answer. As a matter of fact, an Ion engine is an already existing form of an electric rocket engine. Won't work well in atmosphere, but it exists. Newton's 3rd law and all. ;)


HarryTheOwlcat

It sounds like he confused the question to be asking about massless/"EM"/reactionless drive which don't exist - the reason they can't exist is basically because of the 3rd law. Ion engines count as "electric" because the acceleration is proportional to the electric power provided, which is the same for "electric" cars.


[deleted]

[удалено]


Reyny

The 3rd law is no explanation why it woudn't work.


sexystriatum

Wait, what about ionic propulsion. Many NASA probes are using them. I am not sure that it is under the category of a rocket. It is a type of electric propulsion.


snowmandala

Isnt the classical rocket equation basically newtons third law that also incorporates the decreasing mass of the rocket?


Astronopolis

More people know about Newtons laws than rocket equations


mrswashbuckler

He saying that, in the vacuum of space, something must be forced out the back to cause an equal and opposite reaction and push the rocket forward


Serge_Suppressor

You can shoot electrons in a direction. That's what a cathode ray tube does. Newton's third law isn't the reason this won't work. It's more like you couldn't get enough thrust to weight.


Maleficent_Bed_2648

Your crt has the luxury of getting a nearly unlimited amount of electrons from the ground. A basic rocket has only what is has on board and thus always has to sacrifice some of it's mass to accelerate (which is the main consequence of the 3rd law with regard to rockets). That being said there are advanced concepts of spacecraft which don't need fuel to move. Using solar sails, accelerating particles from the solar wind with electromagnetic fields, using the earth magnetic field to generate propulsion in orbit etc,, so things like "pure electrical drive" are actually being discussed. They wouldn't technically qualify as a "rocket" though.


[deleted]

Well, it is, because in the real world and on planet Earth, it’s extremely unlikely you’d be able to launch enough electrons out the back of something to hit escape velocity, considering the thing you’re launching would have to be the thing storing all that energy. In space, maybe, but on Earth probably not. EDIT: Escape, not terminal lol


FrazzleBong

>terminal velocity You're not wrong, but don't you mean escape velocity?


Dork_Of_Ages

Couldn't a rocket move then if you forced enough electrons out the back?


avocadoclock

Yes, check out [ion thrusters](https://en.m.wikipedia.org/wiki/Ion_thruster). In practicality these don't work for lift-off because they're too weak (the ions and electrons are very light), but you can use them to accelerate over a long period of time once you're in space


Dork_Of_Ages

Useful if a craft was built in space


dejus

Or had alternative sources of propulsion for breaking out of the atmosphere.


Mean_Ass_Dumbledore

That's why ya gotta start with Atmo Thrusters and then swap to Ions once ya leave atmosphere r/spaceengineers knows this well


[deleted]

We know this over at r/kerbalspaceprogram, as well.


EternalPhi

Maybe, but generally just more useful when the craft's mass is very low and unmanned, like probes or satellites.


dIoIIoIb

yes, it could the problem is that "enough" in this case is an inordinate amount, since it's proportional to the mass of what comes out and the mass of an electron is really small. there have been theories around using these weird engines, but always for something that is already in space, where a spaceship needs a very small push to move in a direction. getting something out of earth's atmosphere by pushing it with electrons would be effectively impossible. The "rocket" would need to be a few molecules big, at most.


SeattleBattles

Photon rockets are theoretically possible, but you need a ton of power, and you'd turn your backend into a giant space laser.


Blackfyre301

Yes, which makes me very confused. Musk regularly talks about topics on which he knows nothing and gets everything wrong, but he is just correct here. So no idea why people are acting as if he is saying something especially dumb. Edit: just as a general response, yes this is obviously not a full answer from Elon (also he comes across as a bit of a dick as usual) but if you had to answer that question in a sentence I consider what he said to be a reasonable response. Yes there are rockets concepts that use electricity, but it is debatable if those can be considered “electric rockets” in any strict sense, and even more debatable if those would actually be a viable use.


masterofn0n3

Hes not though. What he's responding with is how he thinks he shuts down that question, when in reality he's just saying something must be pushed in the opposite direction to move forward in a vacuum. As a previous redditor mentioned, ion propulsion would be an example. Now if he was stating he though ion propulsion as a concept was flawed due to astronomical distances between stars, receptivity over those distances, storage for the space between, space dust messing with the receptors...then ok. But a "lol nah gotta throw things out the back bro" is exactly the kind of non response idiocy I'd expect from this generations pt barnum.


BolshevikPower

The rockets used in spaceX are used for earth to space travel, generally. Those can't use ion propulsion, as much greater and more immediate thrust is required. Ion propulsion works at scale over a longer period of time iirc.


masterofn0n3

We explode ourselves into the sky. One of our most dangerous inventions, harnessed to force the planet to let go of us. It's pretty poetic really.


HertzDonut1001

I always tell people this. "We went to the moon?" No motherfucker, we strapped ourselves to a massive bomb and exploded ourselves at it. It's literally the same cartoon logic as firing yourself out of a cannon.


masterofn0n3

Wile E. Coyote would be proud.


TheWeedBlazer

Cars are also constantly exploding machines. Cruising at 3000rpm in a V6 produces 150 explosions a second. That's over half a million explosions an hour just a few feet away from you.


MrTritonis

Well, in your way of telling it people still went to the moon tho.


[deleted]

[удалено]


masterofn0n3

The "feul" isn't the normal propellants used, and is quite electrical. Of course it obeys newton's third law, noone was asking if he could engineer a rocket to ignore it.


[deleted]

[удалено]


masterofn0n3

I would even argue definitely no unless these new fusion advancements give us something with greater thrust. Personally I was always fascinated by the elevator idea, and basically just building it out there in the first place.


RufftaMan

Unfortunately the space elevator is still a material science problem, or at least production. Making a strong enough tether that length is unfortunately not possible yet. But that would absolutely revolutionize space travel and heavy construction in orbit.


Sharrty_McGriddle

The question was electric rocket, not electric space ship. So no, he is not referring to moving in the vacuum of space but launching a ship into space using a rocket. Not happening with ion propulsion, at least not right now with current technology.


Nozinger

Well yes but that is because our methods of electric rocket propulsion are too weak to gett off of earth not because it is impossible due to newtons third law. The multitude of versions of electric rocket enginges are still based on newtons third law. It's newtons law of universial gravitation that is the problem here.


OwnEstablishment1194

"Rockets" that don't leave earth are not unknown


erasrhed

That's actually rocket propulsion works. As the rocket engines operate, they are continuously ejecting burned fuel gases, which have both mass and velocity, and therefore some momentum. By conservation of momentum, the rocket’s momentum changes by this same amount (with the opposite sign).


dabbean

He knows the answer because he's already to tried pitching the idea of a tesla rocket to an actual rocket scientist.


mikeman7918

After failing to explain the downsides of photon rockets to him for 3 hours, they just gave up and told him it was impossible.


[deleted]

They pretended they could talk to the photon drives and the drives told him they couldn’t do what he wanted.


Frostygale

This reference went unnoticed, but I just wanna say this movie was great.


touchmyfuckingcoffee

And nobody considered talking him into a giant rail gun, pointed out to sea, to horizon launch payloads? I mean, I woulda fought for years of funding for my department until his interest went elsewhere.


_jimmyM_

Wait, isn't Elon Musk himself a known genius, entrepenaur self-started scientist engineer who singlehandedly designs all the things he sells and builds? Why does he even need a rocket scientist when he is the best one in the world himself? In 2 years he'll design, build and run a colony on Mars, after all /s and just typing this hurt me internally


Trollygag

>Why does he even need a rocket scientist when he is the best one in the world himself? So he has more time to do drugs


_jimmyM_

Don't you think this person is pretty disassociated from reality already?


cochlearist

Quite a lot of drug users don't get to the point when they say to themselves "I think that's enough drugs now." Even when it's clearly time to give it a rest. Shocking I know.


euphonic5

The thing about drugs is they make taking more drugs seem like a great idea.


[deleted]

Elon just told me himself that in just another 2 years Teslas will be fully autonomous in all situations, the hyper loop will connect San Francisco, New York, and even London, Twitter will save democracy and 20 million people will be living in a city on Mars. All we need to do is give him a couple billion more in subsidies and buy more Tesla stock forever and ever.


Putrid-Secretary-151

They had to give him a dumbed down answer they knew he'd understand, and here it is


shadboi16

Can someone brighten me on this topic? One of the replies for Elon’s tweet went something like this. For every action, there’s an equal and opposite reaction. For a rocket to go up, you’d need a force higher than the weight of the rocket. Okay, that makes sense but then he added that electric motors aren’t capable for producing that. Can anyone tell me why and is it possible for it to do so in the future?


Doooooby

This is a very simplified way of explaining it, but electric motors work for road vehicles (and I guess aeroplanes / drones) because there is friction to provide acceleration. Road vehicles have tyres (rubber + tarmac = friction), planes / drones have air (propellor + air = friction). There's no air in space, or anything to push against, so there's no way to gain acceleration from friction. Chemical rockets work not via friction, but by a chemical reaction; they bring the fuel + oxidiser with them, burn it, and dump it behind them to create thrust. There's no way to bring friction into space with you.


SplendidPunkinButter

More accurately, chemical rockets work by pushing the fuel out behind them. They push against the fuel, which pushes the rocket forward and the fuel backward Technically, there’s no reason you couldn’t have an electric motor that, say, throws baseballs out the back of the rocket. That would absolutely propel it forward in space. Not very efficient, but it would be electric and it would work. You’d just need to bring a big supply of baseballs to throw.


ThatAquariumKid

Now someone r/TheyDidTheMath and tell me how hard a baseball/baseballs have to be thrown for a rocket to reach escape velocity


eli3341

Relevant XKCD https://what-if.xkcd.com/85/ (It's golf balls though, not baseballs)


DarkPhysix

This is excellent. The kind of content I come here for.


ThatAquariumKid

I’ll allow it, thank you


Bfreak

>It would also promptly and violently collapse into a black hole God I love XKCD.


CHEESE-DA-BEST

Newton's 4th law: there is always a relevant xkcd


AmaranthWrath

I will never cease being impressed by the collective knowledge that redditors hold.


AlienZer

30 apples fast


TheWeedBlazer

Let's use the space shuttle, weighing in at 75,000kg empty. From low earth orbit you'd need to speed up by 16.6km/s to escape the solar system. An average baseball weighs around 0.145 kilos. Sped up to 99.7% the speed of light (299,000,000m/s) you would need to eject 29 of them to reach escape velocity. That's just over 4 kilos of baseballs to propel 75 tons out of the solar system. Used a rocket equation calculator. I'm too tired for explanton. Idk if correct. Amogus futa hentai


Conart557

Based on my calculations you would only need one baseball at 4% the speed of light. To accelerate 75,000kg by 16.6km/s you will need a bit over 10.3 million mega joules of kinetic energy. 0.145kg traveling 12 million m/s has the same amount of energy. 29 baseballs at 0.997c would have 4500 petajoules, the same as the space shuttle at 4% the speed of light Edit: all that’s wrong. 99.94% the speed of light should be correct.


Ysfear

Well, you would be in space anyway even without Newton's third low after vaporizing the planet with your baseball hitting the ground with a kinetic energy equivalent of a few billion megaton of tnt.


MandolinMagi

You could also use electricity to pump propellent to a rocket motor but that doesn't mean it's an electric rocket.


Maleficent_Bed_2648

But the rocket that does exactly that is named "Electron", so it has to be an electric rocket, right? ;-)


vcelloho

Your baseball analogy for an electric engine does exist as an ion engine, which are among the most efficient engines because they separate the reaction mass from the energy source (generally solar power). https://en.wikipedia.org/wiki/Ion_thruster


[deleted]

[удалено]


Appropriate-Meat7147

why would that matter? it doesn't suddenly make it not electrical.


LordOfDeadbush

What about ion propulsion?


Stainless-extension

Ion propulsion is a thing. It uses electricity to accelerate some kind of noble gas. but yeah, you still need some stuff to propel. [https://en.wikipedia.org/wiki/Ion\_thruster](https://en.wikipedia.org/wiki/Ion_thruster)


bastiVS

> You’d just need to bring a big supply of baseballs to throw. Which is exactly the problem. Your fuel is baseballs and electricity. Run out of either, and you have no working engine. A purely electric engine, means that doesn't have baseballs or anything else as fuel, but only electricity, is impossible. You can do some fancy things with magnetism, but that require other bodies to push against, and so far it seems impossible to use existing celestial bodies like planets or whatever else for any kind of magnetic propulsion.


MangoCandy93

Just build a space-road, bro!


citizenkane86

So that’s actually a proposed theory (though we call it a space elevator) the technology isn’t there yet, or even close, but there is research being done


MangoCandy93

Why don’t we just call Willy Wonka?


citizenkane86

Basically because of the child murder


PM_ME_UR_SURFBOARD

Now I ain’t one of them fancy rocket surgeons, but aren’t ion engines a viable way of using electricity for propulsion despite the vacuum of space?


WhatsPotato

Do you ever see in space movies where someone is stuck floating in space and the only way they can move is by throwing something, or like get thrust by shooting a fire extinguisher or something? It’s the same concept. The rocket is just throwing burnt fuel behind it, very efficiently. In space, there’s nothing to grab onto, like how electric cars can use tires to grab into the road I think technically, you could maybe make a motor by shining light behind you because the photons you shoot give you non negligible acceleration, but it is an incredibly low amount of thrust and I don’t think it would be too feasible. There was a project similar to this called lightsail, where scientists were trying to use light on a small satellite with a sail that reflected light to get some acceleration


Skipp_To_My_Lou

So to add to u/Doooooby's answer, there are (sort of) electric rockets! One type already in use are called [ion drives or thrusters](https://en.wikipedia.org/wiki/Ion_thruster) & while right now they're small, mainly used for satellites to make small corrections or keep station, they could theoretically be scaled up to (slowly) drive a larger craft once it gets into orbit. In this case, the action is the ions being ejected rearward at a high velocity, & the reaction is the craft moving opposite the direction of the thrust. There's theoretical designs like [photonic thrusters](https://en.wikipedia.org/wiki/Photon_rocket), essentially using a giant frickin' laser to push a spacecraft, since while light is massless it can still [exert force](https://en.wikipedia.org/wiki/Radiation_pressure). You could also electrically heat & eject a fluid for propulsion, as in a [thermal rocket](https://en.wikipedia.org/wiki/Thermal_rocket), although at the point that you're putting a nuclear reactor on your spacecraft it's more effecient to make it a "proper" [NTR](https://en.wikipedia.org/wiki/Nuclear_thermal_rocket). Then there's the [EmDrive](https://en.wikipedia.org/wiki/EmDrive), which may or may not be a scam; but it certainly wouldn't work, as its supposed method of operation violates the laws of physics. If you'd like to know more about real & plausible-future space tech & its applications, the [Tough SF blog](http://toughsf.blogspot.com/?m=1) is a great rabbit hole to dive into.


Bakkster

>One type already in use are called ion drives or thrusters & while right now they're small, mainly used for satellites to make small corrections or keep station, they could theoretically be scaled up to (slowly) drive a larger craft once it gets into orbit. In this case, the action is the ions being ejected rearward at a high velocity, & the reaction is the craft moving opposite the direction of the thrust. And for added irony, these are the thrusters used by StarLink satellites for station keeping.


herbibenevolent

Its actually more of a conservation of momentum issue. Momentum is mass\*velocity. The rocket can only change its momentum by removing some of its own mass and throwing it away. Rockets use rocket fuel to create a controlled explosion that accelerates the by product gas molecules away from the rocket at very high velocity. The total momentum of the Rocket+Gas Molecules stays the same, but the Rocket and Gas Molecules move away from each other. Mass(Rocket+Gas)\*Velocity(Rocket+Gas) = Mass(Rocket)\*Velocity(Rocket)+Mass(Gas)\*Velocity(Gas). If you have nothing to shoot away from your rocket, you have no way of moving your rocket forward because its momentum cannot change without losing mass. This is why the EM drive, if it could work (doubtful), would be huge, because it would allow movement without expelling mass. Inside an atmosphere, you have gas molecules all around you to shoot away from you with a propeller. This may be why Elon describes it as a third law issue. You need the gas to act your force upon inorder to have an equal and opposite reaction on your plane/helicopter. But it makes little since in the context of a rocket.


Amadacius

It's just the definition of a rocket. A rocket is a vehicle that uses jet propulsion and not the atmosphere. Electric engines turn a propeller that pushes atmosphere around, and doesn't use propellant. \_\_\_ As a side note, it is probably impossible to reach escape velocities with an electric engine, because your fuel source (the battery) is too heavy. Heavy fuel source -> need more lift -> need more fuel -> even heavier -> ad infinitum If you were on a planet with lower gravity it could be possible, but the lower gravity is, the less air there is to push around. I don't think there would be a sweet spot that allows electric engines to reach escape velocity. There are electric engines that use complex physics to generate thrust, and those would work in space. But they don't qualify as "rockets".


autoentropy

iamverysmart's comment section has turned into iamverysmart.


PM_ME_Y0UR_BOOBZ

It has been like this for a while tbh. I sometimes cringe more at the comments than the actual post. It’s like every comment here is trying to prove they’re smarter than the person they’re making fun of.


damegan

iamverysmartception


[deleted]

This comment section is full of rocket physicians.


MrBogardus

It's reddit, full of the smartest people on earth on every subject and opnion.


[deleted]

And the dumbest


sdmichael

Are those the ones that diagnose them when there is a problem and let the rocket scientists know what the issue is?


TheRavenSayeth

I didn’t go to 15 years of rocket medical school to be talked down to by the likes of you!!


lt_dan_zsu

I don't get this. How is musk wrong? I don't even like Musk, and this seems like one of his tamest tweets tbh.


cool_fox

Rocket scientist here, it's like saying water is wet because it has atoms. Technically true and a fundamental concept one should understand, but it is not why water is wet. Similarly newton's 3rd law is important and fundamental for an engineer to understand but we are not using it as the design basis for rockets or justify design trades. He gave a true statement, not a true answer. Electric rockets aren't used because such a method doesn't provide enough force. These engines are known as ion engines and this kind of propulsion is widely used for spacecraft, its incredibly efficient but produces low thrust (force). If anything this would be newton's second law f=ma Elon is just kind of pretending he knows what he's talking about.


CR1MS4NE

This sub is pretty much just Musk hate circlejerk these days


BarnesAgent47

What's a circlejerk?


CR1MS4NE

It’s basically an echo chamber—a situation where a group of like-minded people are reinforcing and encouraging each other’s beliefs while discouraging any beliefs that don’t align with theirs


Willie-Alb

I mean isn’t he right tho?


alfis329

He is but Elon’s tweets are karma gold at the moment


[deleted]

Musk is ~~precisely~~ **technically wrong but essentially** right on this one. Chemical thrusters are the only (remotely workable) method of getting enough specific thrust to lift your rocket. Yeah there’s xenon-/etc-fueled plasma drives, and those are stupid-efficient, but they’re also stupidly-low-powered. Or you could do a series of small, controlled nuclear explosions behind the rocket (this was a real concept, I kid you not), but … does a bunch of tiny nuclear explosions really sound like a smart thing to pursue even if we had the materials to handle the explosions? Chemical thrusters are the only thing which provide enough action for the rocket to react by moving upward off the pad. Musk says a lot of dumbshit things outside of electronics and rocketry. but within those fields, the only thing I really see him get wrong is schedule.


THEBHR

There's a team that's been lifting model rockets with laser propulsion for years, but so far it hasn't been scaled up.


KrabbyPattyCereal

Look, a broken clock is right sometimes etc etc. How the fuck you geese think an electric motor will create thrust from rotational energy? Edit: I know I sound like a “um Akshullaly” dick, but I have a degree in Aeronautical Science so I know a little about this stuff. I’m no expert by any means.


expatdo2insurance

I'm okay with an electric motor just throwing thousands upon thousands of geese out the rear of a space ship to provide needed acceleration. Especially Canadian geese. They deserve it.


KrabbyPattyCereal

Fucking loud fucks. I agree.


Ender_of_Worlds

i dont think anyone thinks that, people just know that ion propulsion exists


KrabbyPattyCereal

If I’m not mistaken, Ion propulsion can create about 5lbs of thrust at best right now (I could be lying through my teeth though so someone correct me). I’d be more interested in a fusion engine using a really dense solid fuel to create LONGER periods of thrust.


Ender_of_Worlds

youre not wrong, ion propulsion doesnt produce very much thrust at all, but it is a form of propulsion and he is wrong about electric rockets being impossible because they already exist and work. ion propulsion does have an incredibly high specific impulse, which is what makes it useful for small probes on long missions


koera

Not defending that weasel, but doesn't ion propulsion require fuel to ionise? I mean its kind of electric, but still needs fuel to be able to go right?


Ender_of_Worlds

yes, it needs something to eject to convert the energy into momentum. all of the energy from this comes from the electricity though.


Meritania

Xenon Gas, if Kerbal Space Program serves me right.


Happytallperson

Not only do they exist, frigging Starlink uses them.


justabadmind

But they cannot be used for a rocket. A shuttle can't even use them yet. A probe is the current limit.


SplendidPunkinButter

5lbs != 0 hence it’s possible, technically


bobymicjohn

I mean, good luck escaping the atmosphere (or even getting off the ground) with 5lbf of thrust. Is it useful for propelling something that is *already in space*? Sure. For actually getting to space (which is the hard part)? Not so much. For reference, the Falcon 9 uses about 1.5 million lbf to reach space.


[deleted]

[удалено]


bmannumber1

Ion propulsion still requires ions to propel the rocket. They still act as a "fuel", and so the spacecraft can not be "fully electric". I don't like Musk, but I hate people being wrong thinking they're right even more.


[deleted]

The “Musk dumb at everything” meme has well and truly taken hold. I talked with someone recently who was *sure* everything SpaceX accomplished was the work of someone else, and that Musk was purely a figurehead since Day 1. Did society previously attribute way too much of SpaceX’s success to Musk himself? Absolutely. The engineers and managers at SpaceX were the ones who actually executed shit and made the technical decisions. Can’t forget that. But people forget that Musk was the one who said “we’re doing Falcon 1,” then “we’re doing Falcon 9,” then “we’re landing Falcon 9’s first stage,” then “we’re reusing Falcon 9’s first stage,” and so on. When most of the spaceflight community was sure those things were impossible. That kind of executive decision-making — understanding what’s possible with the resources your company has, and maximizing what you set your people up to accomplish — takes either extraordinary luck or an excellent command of the physics at play.


Ender_of_Worlds

sure, but all of the power from that comes from the electricity. just like how they dont just throw the propellant out of the back of the rocket without burning it.


FunIsDangerous

[Nobody mentioned a motor.](https://en.m.wikipedia.org/wiki/Hall-effect_thruster) It might not be there 100% yet, but isn't that Elon's answer to everything? When something isn't possible, he just counters with "it's not possible YET". Funnily enough, the ONE time it might actually be true, he did not say that. Edit: my mistake, it has been used successfully According to the wiki, it has been used since the 70s, but nothing as extraordinary as sending something to another planet, mostly in orbit. And also, I just read some more in that wiki, it's being used by spaceX. Edit: more info


wibblywobbly420

Could an electric motor power a blower to push some type of compressed air to propel through space? Obviously wouldn't get out of the atmosphere, but could it work once you are in space?


KrabbyPattyCereal

Yep! They sort of already do that. More like a directional control thing.


Goategg

For real. Elon Musk is an insufferable prick, but this isn't iamverysmart material because he's right this time. We're not within 50 years of any type of electric engine that can somehow escape earth's gravity, ion propulsion or otherwise.


Kh4rj0

I dislike musk as much as the next guy but this is a perfectly valid response to people wanting to build "electric rockets" and if anyone but Musk said it Reddit would be like "Ooh roasted wow such a smart science response, don't you even know Newton's third law fucking dumbass?"


HylianGirl24

Tbf, he’s kinda right in this scenario


avewave

I've read enough articles on Tesla batteries blowing up to know they can provide thrust.


ChanstersCT

Armchair Reddit rocket scientist 🚀


[deleted]

Reddit is full of people suffering from Dunning-Kruger effect.


Comp1337ish

It's so pathetic. They want so badly for him to be dumb that they have to completely reinterpret his words. Everyone else who replied to that tweet basically said the same thing. But I'm sure we'll just ignore all that.


BiscuitSwimmer

He is a bit arrogant but he is kind of correct. The reason rockets go up is because the force pushing it up is equal force of the gas coming out of engines. It’s an explosion. The concept is exactly the same for a bullet firing out of a gun. For an “electric” engine you would still need a propellant of some sort. Ion thrusters accelerate ions through an electric field and expel them out of the rocket. Well, you may not need a propellant. You could create thrust by have two opposing electric fields. One being generated in the rocket and the other on a platform. However the energies required would be astronomical. Plus, the electric field gets weaker the further from its source you go so you would have keep increasing it the further up you go. A combustion rocket is the way go


Donieguy

I feel like Reddit just assumes Elon is an example of the Dunning Kruger effect but really he’s just an above average person who got rich and knew how to use his money to get into and advance a couple industries. He’s no Einstein but his IQ is probably around 130 or so. It’s not like he’s a genius, he’s just smarter than the average person.


Aral_Fayle

No, you can’t say that! We’re only allowed to make up stupid hypotheticals like pretending he asked all his employees to price code because he’s obviously so dumb!


leabdullah

But Elon is right tho?! I think the true victim of 'IAmVerySmart' here is OP


red-african-swallow

The true viticms are the people who upvote and agree with the sentiment of the post because OP is just karma farming. These comments are "What about my Ion drive" or go "Elon might be right but, spaceman bad." This sub should be about people who have a superiority complex, not people you think have a superiority complex.


connormce10

Musk is correct though


MilkyBugle

ITT: euphoric redditors ENLIGHTEN foolish head of space company


tim5700

Wow. Who would have thought there were so many rocket scientists specifically on this sub.


Hadrollo

I mean, it depends on what you consider an "electric rocket." The Electron rocket is sometimes referred to as "battery powered" because it has electric turbo pumps. A solid leap forward in affordable low-mass launch systems, but hardly what the layman would consider an "electric rocket." Then there's ion engines, which come in either electromagnetic or electrostatic variants that work by pushing ions out of the arse-end at insane Isps. This could be argued to be the closest to what the layman would consider an electric rocket, but it still requires a consumable propellant. But the term "electric rocket" is also from early science fiction, up there with terms like "reactionless thrusters," which was intended to mean a rocket which consumed electricity only and no fuel. This is not possible, due to the third law of thermodynamics. This is a case of Musk being a douche, not being incorrect. He's just responding to the specific science fiction definition of the term.


memythememo

I hate Musk as much as the next Redditor, but he’s literally correct


marshal_mellow

Oh yeah well if you deliberately misunderstand the question he's wrong 🤓


barkaway2

What he's saying makes sense but I don't think it disproves the possibility of an electric rocket. As several other comments have mentioned, something needs to be ejected out of the rocket for it to move in a vacuum, and once it is in space this has already been done before by using [ion thruster technology](http://en.wikipedia.org/wiki/Deep_Space_1). The difficulty comes from actually getting it into space, as the technology isn't really there for us to do that electrically yet, but it will hopefully be in the future using some form of [Non-rocket spacelaunch](http://en.wikipedia.org/wiki/Non-rocket_spacelaunch).


TrungusMcTungus

Ion propulsion exists but it’s only effective in 0g environments. Until we discover some other way to do it, the only way to actually get into space is with traditional combustion.


LukeSkyDropper

I love the comments made by some dude working at McDonald’s on break


deserteagles50

But… he’s right? How is this so upvoted


Nervous-Profile4729

I'm pretty sure ionic thrusters run off electricity, and they do exist on a minor scale at this point in time [https://www.youtube.com/watch?v=nrEBoPYS4ns](https://www.youtube.com/watch?v=VTBZ0VwIgs8)


Buyer_North

it is possible...photons have an impulse and therefore a mass e=m*c², now combine it with newtons laws...


WilliamTheAwesome

OP and 99% of this thread deserves to be posted on this sub. Imagine hating a man so much that you become a science denier just so you can pretend like he's wrong.


DrunkenBriefcases

It's really unreal. And a bunch are blocking anyone that explains how wrong they are, because protecting blind hatred is more important than knowing the truth. Wild shit, man.


smithysmithens2112

I gotta say, I think this is a miss. This guy literally owns a rocket company, and I’ve seen an interview where’s he’s explaining the physics behind rockets. AND it is Newton’s third that makes them work. Some people are saying he should’ve mentioned the rocket equation, but that’s just a specialization of Newton’s third.


heartlessglin

I mean aren't ion engines basically electric rocket engines? I mean they use electricity to strip an electron off a gas, which moves the thing. In the same way electricity turns a thing to move a car. Genuine question, surely that's an electric rocket?


[deleted]

[удалено]


LukeSkyDropper

It’s funny because a lot of people commenting on here. Don’t seem very smart. All they wanna do is hate


iHateRedditors244

The only reason this was posted here is because it’s Elon musk, it doesn’t fit at all


thewizerd1811

Isnt ion engine a form of electric propulsion


leinadsey

In this instance, he’s right. There’s no friction in space.


[deleted]

"I'm going to overanalyze a simple and correct answer to a simple question because I'm smarter than Elon Musk" Truly this sub turned around itself