/sci/ - Science & Math

[Inurdaes !V1sPhobos. No.2235079]

Needs moar railgun.

[Anonymous No.2235104]

just throwing it out there, maybe somebody knows something about railguns

suppose you got a badass(??) railgun in space orbiting the Earth and you fire some shit towards Mars, how much time would it take for it to reach Mars ?

[Anonymous No.2235110]

>>2235104
Depends on the particulars.

Ideally, minutes. But realistically it'lltake months.

[Inurdaes !V1sPhobos. No.2235113]

>>2235104
It would depend on the amount of energy put in and the initial acceleration. Also the distance in between the planets

[Anonymous No.2235119]

>>2235110
>Ideally, minutes

that would be nice, sending supplies to the Martian bases would become cheap and easy

[Anonymous No.2235123]

>>2235113
>It would depend on the amount of energy put in and the initial acceleration

well, yeah, the question is what can we realistically do as of now

[Anonymous No.2235125]

>implying that Railgun wouldn't have to reach from Kanada through the US to Mexico.

[Anonymous No.2235129]

>>2235110
>Ideally, minutes.

LIGHT takes about 4.35 minutes when Mars is at opposition... and considering relativistic effects such as time dilation, I don't think this would be "ideal" for any human payload.

Not to mention the amount of energy needed to STOP this motion would be prohibitive of such speeds.

Not to mention that the railgun itself would have to be several orders of magnitude more massive than the payload. Newton's third law is a bitch.

I'm afraid we'd still have to use fairly conventional speeds... maybe a little faster since more fuel would be available for deceleration.

[Anonymous No.2235131]

>>2235119
Well, if you enjoy getting the base R-bombed with k-rations, making a new kilometers-wide crater, then sure.

The "minutes" part is if the railgun can be made to accelerate the projectile to a significant fraction of c.

Good for busting up the filthy martian rebels, not so good for sending supplies down gently.

[Anonymous No.2235133]

>>2235129
>Not to mention the amount of energy needed to STOP this motion would be prohibitive of such speeds.

we could use the Martian gravitation and atmosphere to stop it

[Anonymous No.2235134]

>>2235129
Hey! He just asked what kind of travel-time the projectile would have. He said nothing about what kind of a railgun we were talking about, less what he wanted to do with it.

[Inurdaes !V1sPhobos. No.2235135]

>>2235123
Assuming a railgun such as shown in the picture could work quite cheaply then a space-based railgun with SOLAR PANELS EVERYWHERE could fling something towards 'insert planet here' quite fast. I can't give you an exact speed though.

[Anonymous No.2235138]

>>2235079

Uhh...yea, gott daym. that shits a BIG Muthafukin railgun

mwf it would need its own set of nuclear power plants to work right

[Anonymous No.2235141]

>>2235138
No, it'd need it's own total-conversion-reactor, or solar panels the size of a major planet.

Even then, a relativistic railgun would almost certainly shatter at the first launch. If not from the lauch-shock itself, then from the spacetime-effect of the relativistic moving mass.

Of course, there are ways to engineer past those problems, but it would still be extremely unwieldy from almost any standpoint.

[Anonymous No.2235146]

>>2235133
Ummm, no. Kinetic energy at relativistc speeds:

           mc²
E = —–——— – mc²
       √[1-(v/c)²]

Try plugging in some numbers for, say, v = 0.5c, even with a mass of only 1kg. Atmosphere and gravity aren't going to to squat for that much energy.

[Inurdaes !V1sPhobos. No.2235152]

>>2235141
>>2235131
>>2235129
Where the shit did it say anywhere relativistic launches?

[Anonymous No.2235157]

>>2235146
who's talking about 0.5c ?? you're fucking crazy

also, atmosphere and gravity can stop anything but it may take some time

[Anonymous No.2235170]

>>2235152
>>2235157
Me. I talked about relativistic launches at >>2235110
>ideally, minutes
With Mars several light-minutes out from earth at the closest approach, the projectile would have to go at c-fractional speed to reach it in minutes.

Come on, use those lovely brains of yours a little.

[Anonymous No.2235173]

>>2235157
>who's talking about 0.5c ??
>>2235152
>Where the shit did it say anywhere relativistic launches?

This.
>>2235110
>Ideally, minutes.

[Inurdaes !V1sPhobos. No.2235174]

>>2235170
Yeah but other people seem to be talking about the ground-based railgun firing shit at relativistic speeds.
>>2235146

[Anonymous No.2235178]

>>2235174
Read the topic again, follow the post quotes.
You ought to notice that the whole discussion about relativistic projectiles started from my flippant quip about minutes.

[Inurdaes !V1sPhobos. No.2235180]

>>2235178
I realize this, I'm just a bit irked that now some people are arguing about relativistic railguns.

[Anonymous No.2235181]

>>2235170
>I talked about relativistic launches
well, forgedaboutit

this shit that we're developing would reach Mars in 250+ days, maybe you can reduce it to "a couple weeks" in the future but that would be awesome
http://www.janes.com/news/defence/jni/jni101214_1_n.shtml

[Anonymous No.2235183]

>>2235157
>also, atmosphere and gravity can stop anything but it may take some time

Try telling that to Arizona.

[Anonymous No.2235188]

>>2235183
that wasn't an intelligent object with a pre-planned orbit

[Inurdaes !V1sPhobos. No.2235192]

>>2235181
How fast would something need to go to reach Mars in 30 days and how much energy would it take up?

[Anonymous No.2235202]

>>2235192
>How fast would something need to go to reach Mars in 30 days

about 25 Km/s or more depending on the distance

>and how much energy would it take up?

idk, it's probably not a linear dependency

[Anonymous No.2235203]

>>2235183
...you can't fool me just by flipped a picture of a hill upside down.

[Anonymous No.2235210]

>>2235188
That was intended to be facetious.

But I still stand by the original statement, that gravity and atmosphere won't be able to stop (read: sufficiently slow) an object traveling at anything near relativistic speeds.

The problem with using the atmosphere is that this is so fast ANY material would just vaporize due to reentry heating.

The problem with gravity is that at such speads, the object would completely pass the planet it mere seconds. Calculate the required deceleration; compare that to Mars' gravitational acceleration at the surface (a paltry 3.73 m/s²) and you'll see why it can't be done. (This paragraph, I'm aware, is overly-simplified in using Newtonian, rather than Relativistic, motion. Using the Relativistic values markedly INCREASES the amount of gravity needed to stop such an object.)

[Anonymous No.2235217]

>mfw all these decades and $hundreds of billions of cold war arms race didn't produce reliable high tech railgun solutions and/or fusion energy generation
all we got out of it was a shitty Moor trip

humanity, I'm dissapoint.

[Anonymous No.2235218]

>>2235217
*Moon trip

[Inurdaes !V1sPhobos. No.2235219]

>>2235217

[Anonymous No.2235225]

>>2235217
>>2235218
lol, I thought you meant the iraqis or somalis

[Anonymous No.2235227]

>>2235210
>anything near relativistic speeds
we have a working 0.00001c railgun
probably 0.0001c or 0.001c would be realistic to hope for in the future

not really "near relativistic speeds"

[Colonel Coffee Mug !phJ7yIcs.Q No.2235235]

>IT fucking T

[Anonymous No.2235241]

>>2235227
READ
THE
WHOLE
FUCKING
THREAD
BEFORE
ADDING
ONE
MORE
NONSENSE
REPLY

[Anonymous No.2235249]

>>2235079
How does it feel being 12? what do you want to do when you grow up?

[Inurdaes !V1sPhobos. No.2235253]

>>2235249
Whoa, where'd this come from?

[Anonymous No.2235259]

>>2235241
>derp

u mad because you're an idiot ?

[Anonymous No.2235263]

>>2235235
I laugh at this. We aren't talking about some fringe of fucking M-theory superstrings or someshit; we're talking about basic LAWS OF MOTION. I think the success of our interplanetary missions (Pioneer, Voyager, Galileo, Cassini-Huygens, etc.) have proven we have a pretty firm grasp of this stuff.

(Besides, relativity is strongly grounded in experiments Einstein conducted "IN HIS HEAD," and only observationally confirmed later.)

Go back to /b/. Adults are talking.

[Anonymous No.2235264]

>>2235253
It came from my keyboard....lol.
Anyway, so, how does it feel to have your whole life ahead of you? Are you considering becoming a scientist when you grow up?

[Anonymous No.2235266]

>>2235253
I think that came from /b/
like this one >>2235259


Your detractor is probably one of those people that have only heard of railguns in a gaming-, or bad movie-context and are unaware of real-world applications.

My detractor on the orher hand is either lazy or stupid.

[Inurdaes !V1sPhobos. No.2235271]

>>2235264
In a few years once I get a fairly concrete source of income I wish to do a Masters in robotics/AI and perhaps some astrophysics or aerospace engineering as a minor or something. But I don't want to go into a job with that, I'm thinking of perhaps starting up a small company or something to launch shit up cheap.

Basically, I'm sorta unsure.

[Colonel Coffee Mug !phJ7yIcs.Q No.2235272]

>>2235263

Oh, I know that, the "experiments in my head" was because you guys are talking about a thousand kilometer-long superconducting railgun to launch payloads, not only at escape velocity, but on a hyperbolic orbit to Mars or some shit. Enjoy your completely ionized atmosphere.

You could at least mention the Lofstrom Loop. But it seems nobody here knows that one.

Go back to /3/. This is /sci/.

[Inurdaes !V1sPhobos. No.2235275]

>>2235272
>You could at least mention the Lofstrom Loop. But it seems nobody here knows that one.
I DO I DO

[Anonymous No.2235277]

>>2235272
Umm, CCM, you should read the thread too.

After Inurdaes started it, the topic turned to space-based railguns...

[Colonel Coffee Mug !phJ7yIcs.Q No.2235283]

>>2235277

That's even worse.

>Relativistic railguns
>Interplanetary space

Also, anything going above 100 km/s is probably too fast for even the best aerocapture.

[Anonymous No.2235284]

>>2235271
Ohh, Ic, well good for you. It is fairly easy to aquire wealth, but knowledge is a different story. Do you have an undergrad degree, a HS diploma?

[Inurdaes !V1sPhobos. No.2235286]

>>2235284
Yeah, graduated from high school.

[Anonymous No.2235292]

>>2235266
>>2235266
>herpaderp I ran out of real arguments and just derp

then quit posting, dumbshit

[Anonymous No.2235295]

>>2235283
And again. CCM, I am disappoint.

Read the thread, the thing about relativistic railguns was begun by me when I didn't know what the railgun was to be used for.

Someone asked what kind of travel time a railgun projectile would have when shot from earth orbit to mars.

The thing about relativistic railguns was buried already, so you could just, you know, have read the thread and contributed, instead of coming off as the same kind of douche as >>2235264, >>2235259
and >>2235249

[Anonymous No.2235298]

>>2235286
Ic, are you considering going to college? What do you think you will major in? (U need a undergrad degree before you can get a Masters)

[Anonymous !akMcdhDUV6 No.2235299]

>>2235129
>>2235146
>>2235173
>>2235183
>>2235210
>>2235263
All me. I hope you don't see me as anyone's "detractor;" I most certainly am not trying to entirely discount the feasibility of railguns for orbital/interplanetary launches... just the specific case of it taking "minutes" to deliver a payload to Mars.

Even in the case of only 0.001c, we're still going to have to stop that payload when it gets there. This is 300,000 m/s, so you'd have to stay in close gravitational contact with Mars for a minumum of 100,000 seconds to effectively brake. That's 10.2 DAYS. At 300,000 m/s, you'd bypass Mars completely in about 20 seconds. So you see the problem.

Solution? Think baseball: If the railgun is the "pitcher," we need some kind of "catcher" in the vicinity of Mars. Whatever form that "catcher" takes, we'd have to build it with labor and materials delivered conventionally. So we're talking about a 50-100 year timeframe probably.

[Anonymous No.2235302]

I think the easiest way would be to use an orbiting asteroid that's been depleted of easily exploitable resources.

Build the railgun through the center of the mass so shots don't make it tumble too much.

>>2235292
What do you care if I post or not, since you're too lazy to read the whole thread, are thus ignorant of the context of the posts and then post stupid shit instead of contributing?

[Anonymous No.2235304]

instead of trolling think about the still open questions:
1). how "hard" is it to stop an intelligent object going at 0.0001c using Mars's gravity and atmosphere

2). what's the relation between railgun speed and energy consumption

[Anonymous No.2235305]

>>2235302
>What do you care if I post or not, since you're too lazy to read the whole thread

I've been here since the beginning, you don't make any kind of sense with your relativistic bullshit so quit posting your nonsense

[Inurdaes !V1sPhobos. No.2235307]

I reckon any objects flung toward any celestial object should have attached rockets to decelerate and avoid potential asteroid collisions and such.

[Anonymous !akMcdhDUV6 No.2235310]

>>2235299

"probably" = "bare minimum"; I don't mean to imply we're in any position to undertake such a project NOW.

>Lofstrom Loop
Railgun technology has a number of advantages over a Lofstrom Loop, not the least being its relative simplicity. There's too much that can go wrong with a Lofstrom loop with potentially devastating consequences.

[Anonymous No.2235311]

>>2235307
>avoid potential asteroid collisions

that's a near zero probability event but yeah it must be able to correct its orbit

[Anonymous No.2235318]

>>2235305
I think what we have here is a case of mistaken identity.

I started it with my quip of a few minutes, but after that, I've tried to get people out of talking about it.

[Anonymous No.2235351]

>>2235079

Magnets

[Anonymous No.2235356]

>>2235351

[Anonymous No.2235375]

inb4coilgun

[Anonymous No.2235376]

[Anonymous No.2235378]

Sure is shitty ballistics in here

[Anonymous No.2235379]

[Anonymous No.2235381]

[Anonymous No.2235382]

[Anonymous No.2235384]

>>2235375
>>2235376
>>2235378
>>2235379
>>2235381
yesssssss

[Inurdaes !V1sPhobos. No.2235387]

I do not think a surface railgun will be able to launch shit directly to planets, so here is my (rough) proposal of 'on-the-go' acceleration. Comments and critique appreciated.

[Anonymous No.2235388]

Calculations for the lower bound of the energy contained in her projectiles.

tl;dr:

lol anime physics

[Anonymous No.2235392]

[Anonymous No.2235393]

>>2235387 Firing a ballistic missile through a tunnel floating through space.

No

[Inurdaes !V1sPhobos. No.2235397]

>>2235393
Why not? I would like to hear exactly why, if the guidance systems are all lined up etc etc.

[Anonymous No.2235399]

>>2235387
And the orbital barrel works.

Once.

Then it falls back to earth due to action-reaction pairs.

Also, all I have left is cutesy bullshit. If you want it, I guess I'll post.

[Anonymous No.2235401]

these threads have potential too bad its just pseudo science and assumptions

[Anonymous No.2235402]

>>2235387

A huge accelerator around the moon would be a better idea.

[Inurdaes !V1sPhobos. No.2235403]

>>2235399
I was actually thinking about that. The orbital railgun would have to be supplied with fuel to keep it's orbit stable.
>>2235402
Elaborate.

[Anonymous No.2235404]

Coffee and Inurdaes whats your scientific background / education?

[Inurdaes !V1sPhobos. No.2235408]

>>2235404
See
>>2235286

[Anonymous No.2235410]

>>2235401
>pseudoscience

I don't think you know what that means.

>>2235403
You'd need the same amount of fuel to keep the orbit stable after a launch as you would to accelerate the projectile with the fuel instead of the railgun.

In fact, due to the inefficiencies, it'd be more efficient to launch a vehicle from the ground with a railgun, and have rockets strapped on to it from there.

Basic physics.

[Anonymous No.2235411]

>>2235397

What shape are you going to build the orbiting launcher?

If you want to aim it you're not going to want to move it all over the place just to catch that really fucking fast thing.

[Inurdaes !V1sPhobos. No.2235415]

>>2235410
Aww shit.
>>2235411
What do you mean by shape? Also the plan was more that it doesn't move too much but the projectile itself guides itself through the accelerator tunnel.

[Anonymous No.2235419]

I'm sorry to crush your hopes but so far humanity has only been able to satellize stuff by using injector vehicles; shooting shit into the sky simply wont do, if the object can inject itself into orbit then using a railgun makes no sense to begin with.

[Anonymous No.2235423]

>>2235415
Now, to be fair, the orbital railgun would remove the need to carry (and thus accelerate) rocket fuel along with the vehicle, so higher velocities would be achievable, but you'd still need a shitload of fuel to maintain orbit.

Equal and opposite forces. F=MA.

[Anonymous No.2235427]

The railgun will be so massive the resulting force from the launch won't move it a huge distance and you can use it's orbit as a buffer.

[Inurdaes !V1sPhobos. No.2235430]

>>2235419
I'm going to assume you mean rockets.
Rockets are expensive.
>>2235423
Oh well.

[Anonymous No.2235434]

Then it'd be pretty expensive to put it in orbit in the first place though.

[Inurdaes !V1sPhobos. No.2235435]

>>2235427
So wait, there is still some merit to the idea?

[Anonymous No.2235436]

>>2235388
at /a/ we call that SCIENCE (capitalization matters).

[Inurdaes !V1sPhobos. No.2235437]

>>2235434
Indeed, but the surface railgun could launch the necessary parts into GEO for assembly, drastically bringing down the cost.

[Anonymous No.2235442]

>>2235430

So are railguns, 3x. energy output <<< energy input

[Anonymous No.2235445]

>>2235435
the oribital railgun would basically save vehicle mass by doing the accelerating and then reorbiting itself (e.g. via ion drives).

[Anonymous No.2235448]

>>2235423
force yes, but you can deliver more energy with less recoil, and energy is what's necessary to leave a gravity well.

[Inurdaes !V1sPhobos. No.2235449]

>>2235445
Sweeeet.

[Anonymous No.2235453]

>>2235410

Nope, orbital railgun will save fuel, because you can use highly efficient engines to keep it in stable orbit.


Another thing to consider for ground to orbit railgun is to place it up the mountain to decrease air resistance.

[Anonymous No.2235454]

>>2235430
If we're sending vehicle of mass M out into deep space conventionally, we'd need to accelerate it by using up fuel. If we use X amount of fuel, then we can get a set amount of energy out of it, which we use to accelerate it (force Y). Unfortunately, fuel has mas, so instead of sending up a payload of about mass M, we get M + X.

Using Newtonian Physics (because we don't need high precision to talk about the difference in efficiencies), we can see that F = MA. Now, the fuel gives a set amount of energy, which is converted into force, Y. In our conventional launch, we have a mass of M + X, and a force of Y. Thus, our acceleration is:

Y / (M + X)

Let's call that A.

Now let's look at if we had an orbital railgun segment. We have some sort of energy source, which we'll assume to provide the same amount of energy as the rocket fuel. That'll provide the same force, Y. This time, since the vehicle doesn't have any fuel to carry, the mass is just M. Looking back at F=MA, this means our acceleration is:

Y / M

Compare that to Y / (M + X), and you'll see that the more fuel we carry, the less acceleration we'll get! So the railgun launch is more efficient, right?

Now, remember, the railgun would be accelerated in the opposite direction of the vehicle. It would experience a force of the same magnitude, but opposite direction. In order to correct for this, we'll need to counteract the force completely, which means we need energy (to convert to a force) to do so. In fact, we need a force of Y in the opposite direction.

So, even though the railgun might seem better at first, you'll need twice the energy that you might first think. So long as X isn't over half the weight (the rocket fuel isn't most of the vehicle's mass), the conventional launch is more efficient.

[Anonymous No.2235456]

>>2235454
Now, the acceleration of the vehicle via the orbital railgun, B, would be much, much greater...if you didn't care about what happened to the orbital railgun afterwards.


And, of course, we're assuming that all the engineering problems associated with a railgun are solved.

[Anonymous No.2235461]

>>2235430
a railgun can put a spacecraft into space, but it can't change the spacecraft's velocity once it's up there. You'll need to change the spacecraft's velocity in order to put it into an orbit, otherwise it will be on a sub orbital trajectory so it will crash back into the earth.

so you need a rocket anyway.

besides, railguns are also expensive.

[Inurdaes !V1sPhobos. No.2235481]

I did another revision.

[Anonymous No.2235483]

>>2235461
anyway, railguns still make sense as a launch vehicle, or seem to anyway. the reason is that you don't need to carry the fuel needed to get up into space with you. So you can have a smaller structure and a more efficient rocket overall.
or it seems to, like I said. See, the problem with a railgun is that the spacecraft comes off the end of the thing at a ridiculously high speed. several kilometers per second at least. At those speeds aerodynamic heating is a pretty big deal. I've done some work on aerodynamic heating of reentry vehicles, and this would be even worse because you would have speeds even greater, and worse, they would be in the densest part of the atmosphere. The only way to deal with this heating is a big ass heat shield, and making the craft blunter. making the craft blunter would also increase drag, so it would require greater speeds, which would in turn increase heating. anyway, at the end of the day, if it's even possible, it would require such a large heat shield that the craft would be heavy enough that the energy saved on not carrying fuel would probably be cancelled out.

maybe not though, it's always worth research.

[Anonymous No.2235499]

It still doesn't make sense to shoot something into it from earth.

You can't really launch parts up with it either, it would destroy most things.

[Inurdaes !V1sPhobos. No.2235501]

>>2235499

[Anonymous No.2235503]

>>2235481
Only works for small vehicles/payloads, and there's the need of continuously supplying it with fuel.

[Inurdaes !V1sPhobos. No.2235512]

>>2235503
Damn.

[Colonel Coffee Mug !phJ7yIcs.Q No.2235530]

>>2235512

Let me draw up a version for you.

[Colonel Coffee Mug !phJ7yIcs.Q No.2235567]

[Inurdaes !V1sPhobos. No.2235579]

>>2235567

[Anonymous No.2235580]

>>2235567
Launch loop + Orbital railgun? Interesting idea for the power induction, but induction would reduce the speed of the projectile for the power produced. Otherwise, the orbital segment has the same problems.

[Colonel Coffee Mug !phJ7yIcs.Q No.2235581]

>>2235580

The loop draws energy from the solar wind, it would have little to no effect on the incoming project. Then again I didn't think about that part, you could just, I dunno, extend several small induction loops on booms or tethers.

[Anonymous No.2235583]

>>2235580
Actually, more problems if it's exactly as described. I'm assuming you have thrusters or rockets to keep the railgun in orbit.

[Colonel Coffee Mug !phJ7yIcs.Q No.2235584]

>>2235583

> I'm assuming you have thrusters or rockets to keep the railgun in orbit.
>Gigantic solar sail statite marked as solar sail statite

[Anonymous No.2235589]

>>2235584
Where is this railgun located? If it's in close orbit with earth, then it's not getting much in the way of solar wind. If it's further out, I can't really say anything except express my doubts, as I have too little understanding of the physics behind solar wind and solar sails to make proper judgment of the feasibility of maintaining orbit with primarily solar wind.

[Colonel Coffee Mug !phJ7yIcs.Q No.2235603]

>>2235589

A sail 632m2 in area would receive enough thrust to counterbalance that of the Sun, as to maintain orbit. I dunno how big it should be to hover above Earth, Robert Forward did the math and the numbers weren't really huge.

As for the induction loop, I don't know, but it's very lightweight and the superconductor deploys itself so with minimal materials you'd have your solar wind power plant set up.

Plus the magnetic field probably wouldn't be wide enough to touch the center, it would be torus and the projectile would go straight through it without deceleration, even if it went through the field it would not have enough deceleration.

[Anonymous No.2235611]

>>2235603
There's still the issue of recoil, unless you intend the railgun to be so high up that any change could be accounted for by repositioning/deploying of solar sails.

But threading the needle on that might be more trouble that it's worth, and any vehicle would have to be properly aligned and constructed to an insane amount of precision; remember railguns require actual contact between the rails and the projectile to function, so a coilgun concept might work better.

And, of course, other methods would probably be more...logical? I can't think of the word. Just because we can doesn't mean it'd be efficient or used.

[Inurdaes !V1sPhobos. No.2235640]

>>2235611
>remember railguns require actual contact between the rails and the projectile to function, so a coilgun concept might work better.
True that. Make it a coilgun.
>109 posts and 40 image replies omitted. Click Reply to view.

[Anonymous No.2235760]

pod

[Anonymous No.2235794]

>my face when the only people who will be using rail guns for the next 100 years will be the US Navy which doesnt give a fuck about space exploration

[Anonymous No.2236115]

>>2235567
I was thinking about something like that too.

Also, the orbit of the secondary railgun could also be corrected by simply shooting sacrificial masses through it, which the railgun decelerates, thus gaining velocity for itself.

That would make it kind of a variant of the Space Fountain concept.

[Anonymous No.2236260]

>>2236115
Unless it's a bidirectional system, you'd need to turn the gun around. Either way, it'd probably need _some_ sort of correctional thrusters, for minor adjustments...unless solar sails can make such minute changes?