up up and away in a: cannon!

[forufes]

you want to design a:

1-cannon

 

that will blast an:

2-object

 

as high as possible in the atmosphere, and again, reaching outer space is a bonus..

 

what are your ideas for 1 and 2?

[Xittenn]

Rail Gun! One launch method currently envisioned involves an under ground magnetic levio track that propels a shuttle forward which then reaches a really high speed before it is spit out at the end of the tunnel.

[insane_alien]

the big problem is the atmosphere. you'll have to have enough momentum and structural integrity to get through the extreme drag and stresses from friction with the atmosphere. a large ablative heatshield wouldn't go amiss either.

[Mokele]

Actually, the idea of rail-gun-only launch has pretty much fallen apart, mostly due to the immense length needed to keep accelerations within human tolerances, but also because of some rather nasty problems when anything close to the ground goes supersonic.

 

However, the spirit of the idea lives on in the idea of rail-assisted launch, where the craft is accelerated to just below Mach 1 before being released to continue on its own power. It seems modest, but it gets around a lot of the difficulties and apparently saves a LOT of fuel (and therefore weight).

[insane_alien]

it should be feasible on the moon and mars(the atmosphere there approximates a pretty good vacuum)

[Mokele]

True, plus the reduced gravity and therefore reduced escape velocity. Of course, constructing something like that on either the moon or Mars would also be quite difficult.

[insane_alien]

yes, it would probably require a base more akin to a small city before the resources become available enough to produce such a construction.

[cameron marical]

The American Navy is,Ii beleive working on something similiar.

 

http://thelede.blogs.nytimes.com/2008/01/29/navy-aims-to-break-record-with-next-test-of-railgun/?hp

[forufes]

Rail Gun! One launch method currently envisioned involves an under ground magnetic levio track that propels a shuttle forward which then reaches a really high speed before it is spit out at the end of the tunnel.

AWESOME!! i totally forgot that, i remember reading about it somewhere a long time ago, but what remains in my memory of it is a weird tank with a missile between two rods ready to be fired.. didn't know it can be implemented to such a huge scale as you mentioned, definitely worth more research..

the big problem is the atmosphere. you'll have to have enough momentum and structural integrity to get through the extreme drag and stresses from friction with the atmosphere.

so what in your opinion is the best way around that? any ideas on going around such extreme obstacles in a way other then head on?

a large ablative heatshield wouldn't go amiss either.

is that necessary?

Actually, the idea of rail-gun-only launch has pretty much fallen apart, mostly due to the immense length needed to keep accelerations within human tolerances,

the thing which will be launched (#2 in the OP) does not have to have a human or any other sensitive equipment onboard, the launched object's goal is to go as high as possible, a human isn't necessary for that.

 

and wen you said immense length, what did you mean? the tube it's launched from??

but also because of some rather nasty problems when anything close to the ground goes supersonic.

like what?

if you mean concussions and strong shockwaves then lets say it's launched from within a desert, are the problems still present?

 

However, the spirit of the idea lives on in the idea of rail-assisted launch, where the craft is accelerated to just below Mach 1 before being released to continue on its own power. It seems modest, but it gets around a lot of the difficulties and apparently saves a LOT of fuel (and therefore weight).

great, so if the idea is scrapped off as a fail for the sole method of launch, it can still be used as an augmentation with other methods, right?

 

and what properties does a projectile has to obtain to be launchable from a rail gun? does it have to be magnetized in some way?

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besides people, you've all given your ideas for #1, the launcher, how about the projectile?

 

personally, i was thinking of a HUGE cannon, erected vertically to help it support itself. have it's shaft connected to an underground chamber, in which the strongest explosives other than the nuclear will be ignited, and in BIG quantities.. the projectile will be a sheer metal (or any other durable material; titanium) slug.

 

so simply, a sheer kinetic method, based on monstrous mechanical power..

 

btw, how will you know he hight it reached, you embed it with some transmitter or follow it on radar? any insights?

[Mokele]

and wen you said immense length, what did you mean? the tube it's launched from??

 

Yep. To reach escape velocity it would have to be very long, possibly over a mile.

 

like what? if you mean concussions and strong shockwaves then lets say it's launched from within a desert, are the problems still present?

 

It's not a matter of disrupting people, but of the shock wave's interaction with the ground and the resultant forces and potential damage to the projectile.

 

and what properties does a projectile has to obtain to be launchable from a rail gun? does it have to be magnetized in some way?

 

Depends upon the railgun system - some do require it, others don't. Also, it's entirely possible to simply mount the projectile to a detachable carrier that has the needed properties.

[Sisyphus]

A cannon powered by explosives isn't going to work, because muzzle velocity has an upper limit based on the rate of expansion. A railgun has no such limit.

[Xittenn]

A mile is not really that long..........in fact 10miles isn't really that long. It could very easily be run underground. It would be interesting to see an approach on this within our lifetime.

[rockman]

I've thought about this over the years.

 

The problem with the cannon, is the sudden acceleration.

 

So why does it have to be a cannon?

 

Why not spin it to incredible speeds and then hurl it toward space like a rock on a string. Shape it like a frisbee. Spin it like a frisbee and throw it up there.

 

Not as far fetched as it seems.

 

If the object spun and thrown also carried a small rocket(s) to boost it that last distance, it may just make it.

[Xittenn]

So like with an acceleration of 3G or [math] 30m/s^2 [/math] on a 15km track you would hit a speed of [math] 948m/s [/math] in 31.6sec or roughly mach 2.7....

 

Not a bad start...........regardless of whether it's an orbital launch or an escape flight and pretty standard G forces too.

[forufes]

Yep. To reach escape velocity it would have to be very long, possibly over a mile.

 

escape velocity? you mean to orbit the earth or go straight up?

 

and the length, can't you make up for that with a bigger force or more efficient firing system?

 

is that length fixed?

 

 

 

It's not a matter of disrupting people, but of the shock wave's interaction with the ground and the resultant forces and potential damage to the projectile.

so the shockwave disrupt the ground which disrupts the cannon which disrupts the projectile, right?

 

so we should scratch anything going near mach?

 

any absorbing or dampening systems or something?

 

 

 

Depends upon the railgun system - some do require it, others don't. Also, it's entirely possible to simply mount the projectile to a detachable carrier that has the needed properties.

like a rollocoaster with an eject seat?

 

A cannon powered by explosives isn't going to work, because muzzle velocity has an upper limit based on the rate of expansion. A railgun has no such limit.

iNteResTInG

 

please elaborate

 

 

I've thought about this over the years.

 

The problem with the cannon, is the sudden acceleration.

why is that a problem?

 

no humans on board.

 

or are you referring to the immense length required for the cannon, the mach limit, or some other easons?

 

So why does it have to be a cannon?

 

Why not spin it to incredible speeds and then hurl it toward space like a rock on a string. Shape it like a frisbee. Spin it like a frisbee and throw it up there.

 

Not as far fetched as it seems.

 

If the object spun and thrown also carried a small rocket(s) to boost it that last distance, it may just make it.

 

the spinning method is definitly an excellent alternative, avoiding the problems mentioned earlier, but i think it'll be more complex to build.

 

but why shape it like a frisbee? what do you gain from it spinning?

 

So like with an acceleration of 3G or [math] 30m/s^2 [/math] on a 15km track you would hit a speed of [math] 948m/s [/math] in 31.6sec or roughly mach 2.7....

 

wow, you made the calculations seem very easy..

 

now how to administer the acceleration?

1-magnetic(rail gun)

2-chemical(explosives-traditional cannon)

3-electrical(for the revolving mechanical arm?)

4-???

 

as for the "track":

1-erected shaft;)

2-underground tunnel.

3-mechanical arm.

4-???

Not a bad start...........regardless of whether it's an orbital launch or an escape flight and pretty standard G forces too.

i want to know the difference between those two...one is vertical the other is a bit tilted, otherwise they're identical, right?

[J.C.MacSwell]

Rail gun + hollow tube with vacuum (less drag and no "mach/shock" concerns), either timed to open/close at the top with passage of the rocket, or simply long enough to reach space.

[Xittenn]

Rail gun + hollow tube with vacuum (less drag and no "mach/shock" concerns), either timed to open/close at the top with passage of the rocket, or simply long enough to reach space.

 

There could be a shutter at the end of the tunnel formed by a high velocity air current; similar to an air curtain fridge door. Atmosphere could be introduced at an appropriate gradient near the end of the tunnel. At this critical stage the shockwave that would develop could be squelched and siphoned off.

[rockman]

Forufes wrote:

 

"but why shape it like a frisbee? what do you gain from it spinning?"

 

I guess the best answer would be another question:

 

Why do you want a football to spin when thrown??

 

Ever take a pop can and cut the ends off and throw it? It gets good distance. But if you don't spin it, it will not work.

 

Ever try to throw a frisbee like a baseball?

_____________________________________

 

Spinning an object and throwing it into space makes a little more sense if your trying to get some kind of equipment in space without destroying it. Even a mile is too short of a track in my opinion. If your spinning it you have as many miles as you want.

 

I like the rail idea though.

[Xittenn]

Isn't a normal rocket just a cannon in reverse with no projectile and a long explosion with the cannon doing the flying? I'm pretty sure this is the closest one will come to putting things in space via this method. Unless they perfect the 'force field' and stuff a projectile in a barrel with a nuke. Yes/No?

[forufes]

Rail gun + hollow tube with vacuum (less drag and no "mach/shock" concerns), either timed to open/close at the top with passage of the rocket, or simply long enough to reach space.

the vacuumed tube idea is marvelous, i wonder if it's applicable though and practical.

 

how strong does the tube has to be to support itself?

 

is the reduced drag worth the trouble of vacuuming the tube?

 

but if it isn't too troublesome i think we will have what to win and nothing to lose.

There could be a shutter at the end of the tunnel formed by a high velocity air current; similar to an air curtain fridge door. Atmosphere could be introduced at an appropriate gradient near the end of the tunnel. At this critical stage the shockwave that would develop could be squelched and siphoned off.

 

that went totally over my head, i'm only aware of the squelching at the end:D

 

Forufes wrote:

 

"but why shape it like a frisbee? what do you gain from it spinning?"

 

I guess the best answer would be another question:

 

Why do you want a football to spin when thrown??

 

Ever take a pop can and cut the ends off and throw it? It gets good distance. But if you don't spin it, it will not work.

 

Ever try to throw a frisbee like a baseball?

_____________________________________

 

Spinning an object and throwing it into space makes a little more sense if your trying to get some kind of equipment in space without destroying it. Even a mile is too short of a track in my opinion. If your spinning it you have as many miles as you want.

 

I like the rail idea though.

 

shaping it like a Frisbee is understandable, the shape will give better penetration and less friction.

 

but why the spinning?

 

don't mix the two,.

 

when something spins while going achieving linear movement it will reach less further, because some of the energy is taken instead of propelling it further into spinning it.

 

that is useful when you have excess energy which will be wasted if the projectile was not spun, bullets spin while flying, that what makes them destroy or penetrate their target, i think the kinetic energy transferred from the spinning of the bullet to the contacted surface is of a greater magnitude than that transferred by the bullet ramming the surface.

 

of course i might be wrong, this is my personal analysis.

 

also, i think the thing with hand thrown things is that when designed, they know the human hand will spin the thrown obgect no matter what, so they actually include it in their design in a way the thrower spins it by his will; hence controlling the spin and the thrown thing flies better, instead of designing the thrown object while neglecting the human hand's slight spin which will screw the whole flight path of the thrown object.

 

frisbees, balls, boomerangs are thrown by hand, spinning is part fo their flight system.

 

toy rockets and planes are usually launched from a rubber launcher which ensures linearity.

 

Isn't a normal rocket just a cannon in reverse with no projectile and a long explosion with the cannon doing the flying? I'm pretty sure this is the closest one will come to putting things in space via this method. Unless they perfect the 'force field' and stuff a projectile in a barrel with a nuke. Yes/No?

wow, lol, you're brain certainly works in a strange way.

 

yup you're right in what you said..

 

but i think the problem is that a rocket is the cannon and the projectile.

 

a cannon should have tremendous power,

 

and the projectile would be better light.

 

usually tremendous power gains more weight,so having them together will mean you have to compromise one for the other, and that's usually achieved through a very complex balance, but when they're separated you can go to extremes more freely and be as clumsy as you want, i look at it like this; dig a big hole, fill it to the rim with dynamite, cover it and link it to a long tube welded well to the underground bunker, throw in a slug of titanium, light the fuse....and pray it doesn't blow YOU to outer space:D

 

which is i think where your force field jumps in:-p

[rockman]

forufes wrote:

 

"shaping it like a Frisbee is understandable, the shape will give better penetration and less friction.

 

but why the spinning?

 

don't mix the two,.

 

when something spins while going achieving linear movement it will reach less further, because some of the energy is taken instead of propelling it further into spinning it.

 

that is useful when you have excess energy which will be wasted if the projectile was not spun, bullets spin while flying, that what makes them destroy or penetrate their target, i think the kinetic energy transferred from the spinning of the bullet to the contacted surface is of a greater magnitude than that transferred by the bullet ramming the surface.

 

of course i might be wrong, this is my personal analysis."

---------------------------------------------------------------

Thanks for your reply,

 

And you may not be wrong.

 

My point for the spinning, and it "may" be wrong, is that it may help slice the air. Air is a medium, just like bread is a medium also. Bread can be cut with a knife without a slicing motion, but...you get the idea.

 

Of course I'm trying to consider the rapid entrance into the atmosphere at a very high velocity. No matter what the device...rail gun, spinning and flinging, the object will hit the atmosphere at a tremendous speed. Like a brick slapping water. Well...not exactly like that!

 

But...that being said,

 

Is there any way the atmosphere could be sliced, split, or seperated "ahead" of the object being launched???? It would be a lot easier if we just had to deal with gravity and eliminate some of the atmospheric drag.

[Sisyphus]

Bullets are made to spin so they fly straighter because of gyroscopic stabilization.

[forufes]

My point for the spinning, and it "may" be wrong, is that it may help slice the air. Air is a medium, just like bread is a medium also. Bread can be cut with a knife without a slicing motion, but...you get the idea.

aha, i see what you mean, like comparing a sword to a chain saw.

so when penetrating the air, slenderness and spinning are the two factors to consider.

 

designes with mixtures of different "shades" of each factor generates numerous possibilities.

 

definitly worth of more research...

 

Is there any way the atmosphere could be sliced, split, or seperated "ahead" of the object being launched???? It would be a lot easier if we just had to deal with gravity and eliminate some of the atmospheric drag.

the typical idea of "ahead" we have now is a cone head..i can't seem to find an innovative alternative which is also practical..

 

anyone else?

 

how about a laser in the cone of the projectile? is hot air easier to penetrate or cold air?

 

not to mention hot air will heat the cone, which is an already existing problem...idk

 

Bullets are made to spin so they fly straighter because of gyroscopic stabilization.

how much more stabilized will they be? look at arrows fired from bows, are bullets considerably more straighter??

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and hey, spinning DOES absorb some energy which would otherwise be used for propelling forward, right?

[Sisyphus]

Yes, it's much more stabile. Guns got a whole lot more accurate when they figured out how to spin projectiles by rifling the barrels. That is the reason - ignore all this stuff about "cutting the air" or whatever you and rockman are talking about.

 

http://en.wikipedia.org/wiki/Rifling

[rockman]

http://www.spacedaily.com/news/future-00o.html

 

I wonder if after more research has been done, if it would be possible to do this from the ground instead of building it into the nose cone which adds weight. On aircraft flying here and there, the nose cone would make sense. But with an object taking a predetermined path, ground based may be a possibility.