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/sci/ - Science & Math

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7136116 No.7136116 [Reply] [Original]

Why don't we use light as propulsion?


As you all know, E (energy)= (1/2) m*v^2, and so v, the speed, is the highest it can be at the speed of light. The energy, therefore, would be the highest possible energy in existence


Light rockets would provide the highest energy and therefore the highest propulsion.


Why arent we funding this?

>> No.7136120

We are:
https://en.wikipedia.org/wiki/Solar_sail

>> No.7136142

>>7136120
>sails

There's a reason we stopped using sails to navigate the oceans hundreds of years ago. They are slow as fuck.

>> No.7136209

fuck you guys. I start an actual science thread with original ideas, and you all ignore it to go post in le .99......threads

>> No.7136222

>>7136209
And which thread is that?

>> No.7136252

>>7136222
epic meme. Make sure to share it on reddit

>> No.7136289

>>7136209
It's not an original idea or actual science. It's more like listening to a stoned person get excited about something stupid.

If you honestly thought this was a coherent idea, I feel sorry for you, but you have to go learn some actual physics.

>> No.7136510

>>7136116

From Wikipedia:
Current commonly accepted physical theories imply or assume the photon to be strictly massless

Sort of a light engine:
http://www.qrg.northwestern.edu/projects/vss/docs/propulsion/zoom-solar-ion.html

>> No.7136576
File: 1.16 MB, 250x250, 1426090844031.gif [View same] [iqdb] [saucenao] [google]
7136576

>>7136510
>photons don't have momentum

>> No.7136587

>>7136209
>shits out retarded idea
>"I'm contributing!"

>> No.7136605

>>7136576

He didn't say they didn't have momentum.

>> No.7136654

>>7136116
>As you all know, E (energy)= (1/2) m*v^2, and so v, the speed, is the highest it can be at the speed of light. The energy, therefore, would be the highest possible energy in existence
>Light rockets would provide the highest energy and therefore the highest propulsion.
>Why arent we funding this?

your physics are completely wrong.
the Energy of a photon is calculated by E = h*f where f is the frequency of the photon and h is the Planck constant.
your formula for kinetic energy is a) only an approximation for v << c (non relativistic)
and b) only valid for particles/bodies with (rest-)mass.
This both is not the case for the photon.

You CAN associate an impulse with a photon though. It is given here http://en.wikipedia.org/wiki/Photon#Physical_properties

this is acutally used as a source for locomotion in the technology called "light sail", http://en.wikipedia.org/wiki/Spacecraft_propulsion#Electromagnetic_propulsion

>> No.7136706

>>7136510
Also from Wikipedia:
Although photons are considered to be zero-rest mass particles,
they have the properties of energy and momentum, thus exhibit the property of mass as they travel at light speed.

>> No.7136725

>>7136706
Which is why solar sails work. You could shine a flashlight out the ass of your spaceship, but the resulting acceleration is negligible unless it is a really fucking big flashlight. Solar sails let us get around having to make and lug around our own giant ass flashlight by using the sun.

>> No.7136737

>>7136510
>Sort of a light engine
>ion propulsion
wat

>> No.7137175
File: 54 KB, 602x350, lightthrustship.jpg [View same] [iqdb] [saucenao] [google]
7137175

>>7136654
So a billion candle power flashlight in the middle
of space.
Will it accelerate or not ?

>> No.7137192

>>7136706
> 2015
> rest mass

>> No.7137193

>>7137175
>So a billion candle power flashlight in the middle
>of space.
>Will it accelerate or not ?
it will accelerate.

>> No.7137208

>>7137193
Why ?

>> No.7137213

>>7137208
Conservation of momentum

>> No.7137242

>>7137213
What scientific experiment confirms the flashlight will accelerate ?

>> No.7137250

>>7136116
Kinetic Energy is not 1/2 mv^2 this is only at small velocities, it's dp/dt. Even Newton knew that.

>> No.7137254

>>7137250
Whoops not dp/dt, rather the integral with respect to time.

>> No.7137273

>>7136142
the only reason we don't use solar sails today is that we aren't very good at deploying them.

If you can make them light enough and send them on a trajectory close to the sun, they can be very fast.

>> No.7137275

>>7137175
http://en.wikipedia.org/wiki/Nuclear_photonic_rocket

>> No.7137280

>>7136116
E = .5 m v^2, yes.
What's the mass of a photon?
they're massless.
why?

because photons also have wave-like properties. They reflect and get absorbed off of surfaces, as opposed to applying a force to the surface itself.

In other words, the amount of light that you would need for propulsion (let alone propulsion of a fucking rocket) is way more than feasibly possible.

>> No.7137287

It's easier to burn light for fuel.

>> No.7137293

We already use light for propulsion, dumbass.

>get in rocket
>burn rocket fuel
>less mass; you become lighter
>this light propulses you

Did OP go to highschool??

>> No.7137300

>>7137242
heres an example you ca do at home. take a very powerful searchlight and bolt it to the hood of your car. turn it on and you're car will go slower than if you didnt have the search light on your car!

>> No.7137301

>>7136116
What is solar sail?

>> No.7137303

>>7137280
Suppose you give mass to the photons? It's been simulated already. Now how to harness it as propulsion?
http://phys.org/news/2014-05-scientists-year-quest.html
But I'm not qualified to give any real opinions.

>> No.7137319
File: 669 KB, 1394x1109, Nuclear_Rocket_Engine_Being_Transported_to_Test_Stand_-_GPN-2002-000143.jpg [View same] [iqdb] [saucenao] [google]
7137319

Its called nuclear power.

Check out some of Zubrin's concepts sometime.

NERVA was badass.

>> No.7137324

>>7136209
Can you kindly point me towards that thread?

>> No.7137339

>>7136116
> Why arent we funding this?

Found this online.

The PLT project is currently funded by a Phase II NIAC (NASA Institute for Advanced Concepts) grant, which funds ideas for next-generation NASA space missions
http://www.photonics.com/Article.aspx?AID=28582

>> No.7137341

no

>> No.7137345

>>7136252
did you mean this thread?
your premise is wrong.
E =/= (1/2) m*v^2
There can be infinite energy in a particle that travels closer and closer to the speed of light.

>> No.7137355

>>7137339
https://www.youtube.com/watch?v=8Gr3UtCaREY

Commenters at the YouTube Institute of Physics have harsh criticism.

>> No.7137361

The sun emits more light than we could ever hope to

and it doesn't go anywhere
checkmate

>> No.7137364
File: 15 KB, 250x250, mfw-caesar.jpg [View same] [iqdb] [saucenao] [google]
7137364

>>7137319
mfw the best rocket engine is 50 years old
>>7137272

>> No.7137369

>>7137175
http://physics.stackexchange.com/questions/112866/if-im-floating-in-space-and-i-turn-on-a-flashlight-will-i-accelerate

>> No.7137371

>>7137242
Again.
Anyone know the original experiment that establishes this ?

>> No.7137372

>>7136116

This would workif the photons were tunnelled through several Higgs Field Generators.

>> No.7137395

>>7137361
Regardless if the light 'pushes' anything anywhere, the sun would push light out 'equally' in all directions. Therefore going 'nowhere'.

>> No.7137398
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7137398

>>7137371
What scientific experiment establishes that dropping a screw will move the earth?

An engine like that would be ridiculously weak. You could get out into orbit and try to measure it, but it would have to be such an exact experiment that it's not really worth discussing at the moment. The earth accelerating from the force of a falling screw and a flashlight accelerating from the light it gives off are consequences of other well known bits of physics, Newton's third and the conservation of momentum respectively.

>> No.7137404

>>7137300
The searchlight should be pointed to the rear of the vehicle.
Drive at night and record the speed with the searchlight turned on (A) and switched off (B).
Drive the car west during sunrise with the searchlight off and record the speed (C).

Photonic thrust is calculated as A-B
Solar pressure is calculated by C-B

>> No.7137408

>>7137398
>What scientific experiment establishes that dropping a screw will move the earth?

There are probably many.
Research involving ocean tide effects due to the orbiting moon for example.

>> No.7137411

>>7137398
Translation: I dunno.

>> No.7137413

>>7137408
What do tidal forces have to do with this? No.

>>7137411
Good.

>> No.7137491
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7137491

>>7136116
>is this nigger really suggesting we use the visible light frequency as some sort of propulsion system?
Look up microwave space propulsion. We're already doing that as a replacement of traditional precious fossil fuel when in "free-fall". It still uses the electromagnetic spectrum, but is less retarded than what you suggested.

>> No.7137530

>>7136116
https://www.youtube.com/watch?v=LAdj6vpYppA

>> No.7137532

>>7137491
how does that work?

>> No.7137550

>>7137371
Just incase you are actually not just pulling and epic troll and just being plain retarded here is one
http://en.wikipedia.org/wiki/Nichols_radiometer

That being said, it's a commonly known fact that light carries momentum and can be used for propulsion, mainly in the form of a solar sail.
http://en.wikipedia.org/wiki/Radiation_pressure

>> No.7137571
File: 1.36 MB, 2100x1750, HiggsFieldGenerator.jpg [View same] [iqdb] [saucenao] [google]
7137571

>>7137550

You still need mass to move a mass...or...you must give the photons mass.

>> No.7137578

>>7137571
Are you retarded?

>> No.7137583

>>7137578

Do you even Newton's 2nd Law?

>> No.7137613

>>7137583
do you even relativistic impulse?

>> No.7137617
File: 20 KB, 709x531, newton2nd.gif [View same] [iqdb] [saucenao] [google]
7137617

>>7137613

NASA called and doesn't think it works and is sticking with Newton.

>> No.7137621

>>7137613
Do you even EmDrive?

http://nextbigfuture.com/2015/02/more-emdrive-experiment-information.html

>> No.7137623

>>7137361
That's what keeps it together.

>> No.7137624

>>7137613
>>7137621

Does anyone in /sci/ even Alcubierre drive?

>> No.7137626

>>7137621
wasn't that confirmed as fake?

>> No.7137631

>>7137626
No. It's awaiting confirmation from GRC once they achieve 100 microNewtons. It produces thrust, it's the ideas about how it works that were found to be bullshit. "Anomalous thrust" they call it, as in, I have no idea how it works, but it does.

>> No.7138342

>>7137571
Lrn2radiation-pressure

>> No.7138863

>>7137550
> What scientific experiment confirms the flashlight will accelerate ?

> Just incase you are actually not just pulling and epic troll and just being plain retarded
> http://en.wikipedia.org/wiki/Nichols_radiometer
> http://en.wikipedia.org/wiki/Radiation_pressure

Those both concern radiation pressure.

This
>> 7137242
is a different but closely related effect.

So the post is asking:
What are some early (fundamental and or famous perhaps) experiments that set up the apparatus to directly test photonic emission thrust ?

The Nichols experiment or referring to Crooke's radiometer would be a good answer if the question had been:
What scientific experiment confirms the solar sail will accelerate ?

This post:
>>7137404
although a little silly, actually describes the difference between the two experiments.

>> No.7138887

>>7137571
>implying photons don't have a mass
>unaware of quanta

>> No.7139131

>>7137631
This article raises a lot of doubt about EM drive:
http://blogs.discovermagazine.com/outthere/2014/08/06/nasa-validate-imposible-space-drive-word/#.VQoumI7HSSq

>> No.7139160

>>7139131
Check the dates.

>> No.7139164
File: 156 KB, 640x480, PhotonDrive.jpg [View same] [iqdb] [saucenao] [google]
7139164

>>7137371

I'm on this. Will place a flashlight in the back of my vehicle and measure the acceleration. Will keep you posted.

>> No.7139175

k-pax had this as a theory and if you didn't see it, we'd blow ourselves up.

>> No.7139256
File: 24 KB, 290x342, shipsfcomp.jpg [View same] [iqdb] [saucenao] [google]
7139256

>>7139131
Pic related. What's the difference ?

>> No.7139499

>>7139256

So crazy it might just work. Good Job anon.

>> No.7140064

>>7139164
Simpler, put flashlights on FRONT, then use them as brakes.

>> No.7141155

>>7136116
maybe i am missing your point, but the mass of a a photon is very small, so i dont see how you came to the conclusion that that energy would be the highest possible in existence.

im pretty sure the shit i just took contains a lot more energy than the kinetic energy of a single traveling photon

>> No.7141645

>>7141155

See this: >>7137372

It's like you guys keep wanting to ignore Newton.

Here...think about the surface area of a solar sail....also think about how many photons have to hit it to accelerate your vehicle.....

Now reverse that and think about how many photons you need to eject out of the back of a vehicle to accelerate it.

It's always going to be a mass problem. Either add mass to the photon or eject a mass of (mass-less) photons commensurate with the mass of the vehicle you want to impart an acceleration on.

Shit man, it's not like it's rocket science....

>> No.7142123

Because mass of light is like... zero. Go study you faggot

>> No.7142126

Stick light in yo ass bitch! If light could do this kind of shit everytime you turn on a lamp your going to b thrown away very far stupid fag

>> No.7142132

>>7142126
We can see that this wasn't the first post you made in the thread, so I think this counts as low-quality content.

>> No.7142141

>>7137617
No they would never calculate the impulse carried by photons with Newton's second law. Please shut the fuck up in the future.

>> No.7142146

>>7142141
*Momentum

fucking German

>> No.7142200

>>7142123

kek...

You mean the "rest" mass of a "photon" is like zero.

>> No.7142207

>>7136116

Because we don't have enough of it to push shit around.

>> No.7142284

>>7137371
>Crooke's radiometer