How High Can a Ground-Launched Projectile Reach?

[AtomicJoe]

Note the the projectile must rely on it's own kinetic energy after release from the projecting mechanism.

Also is there a practical limit on the height which can be achieved.

No new energy given to the projectile after release.
the height of the launching apparatus does not count thus assume the release takes
place at ground level to all extents and purposes.

 

[Ryan_m_b]

The most powerful tool for shooting unpowered projectiles is probably the US navy's experimental rail gun http://nydn.us/fGMVT2 Capable of firing a shot 200 miles across the Earth I imagine it would be able to fire quite high too.

 

[Bloodthunder]

Voyager 1? =D Highest it has gone is to the outer rim of the solar system, and still is going.

 

[Ryan_m_b]

Voyager 1? =D Highest it has gone is to the outer rim of the solar system, and still is going.

Lol true but I think the OP is specifically referring to a projectile fired from Earth rather than launched on a rocket.

 

[AtomicJoe]

The only reference there to an actual shot fired is of a distance of 5,500 feet. (about 1 mile)
Which is somewhat short of the 200 miles you quote, and indeed rather unimpressive to say the least.
The 200 miles seems to be an aspiration to be reached in 2025, there is also a figure of 100 miles mentioned although it is rather unclear if that distance was actually reached in practise or is some sort derived figure which may not be practically possible.

 

[Ryan_m_b]

The only reference there to an actual shot fired is of a distance of 5,500 feet. (about 1 mile)
Which is somewhat short of the 200 miles you quote, and indeed rather unimpressive to say the least.
The 200 miles seems to be an aspiration to be reached in 2025, there is also a figure of 100 miles mentioned although it is rather unclear if that distance was actually reached in practise or is some sort derived figure which may not be practically possible.

That's why I said "experimental". However it has launched a projectile at mach 8. As this is a record for a projectile I would estimate that under the right conditions it would be the best candidate. Unless you wanted to point a linear accelerator up and opened the end of it at the last second.

 

[SpectraCat]

I know that Gerald Bull was trying to design guns that could launch satellites into orbit from the Earth's surface. I think his record was an altitude of around 180 km, achieved as part of the HARP (High Altitude Research Program). I don't know if anyone has ever beaten that ... I don't think unpowered ballistic launches to orbit from the surface of the Earth have ever been demonstrated.

 

[AtomicJoe]

http://www.popularmechanics.com/technology/military/weapons/1280861

Well this one actually fired shells 25 miles high and is verifiable.

I am look for clear reports of higher heights.

 

[AtomicJoe]

OK this seem to verify 179km.

http://www.daviddarling.info/encyclopedia/H/HARP.html

By the end of 1965, HARP had fired more than a hundred missiles to heights of over 80 km. In Nov. 19, 1966, the Army Ballistics Research Laboratory used a HARP gun to launch an 84-kg Martlet to an altitude of 179 km – a world record for a fired projectile that still stands.

 

[Ryan_m_b]

Wikipedia covers some of the successes of Project HARP http://en.wikipedia.org/wiki/Project_HARP

 

[AtomicJoe]

Anyhow that is nowhere near the escape velocity of earth, something I had suspected from my initial question, hence it is hard to see it ever being used as a launch mechanism.

 

[turbo]

Even a measly .22 Long Rifle round can travel in excess of a mile. Some Googling is in order folks.

 

[Ryan_m_b]

This link* shows an interesting answer to the question of what escape velocity is when resistance is taken into account. It obviously depends on the shape, size, air density and drag coefficient of the projectile however the poster there concludes that for his hypothetical object escape velocity only increases from 11kps to 15kps.

Obviously HARP was discontinued but if the money was there a cannon capable of launching a projectile to orbit could be built. Why we would ever want to do that is another issue...

*http://physics.stackexchange.com/qu...stance-what-is-the-escape-velocity-from-earth

 

[Oudeis Eimi]

Anyhow that is nowhere near the escape velocity of earth, something I had suspected from my initial question, hence it is hard to see it ever being used as a launch mechanism.

Launch mechanism? You wouldn't want a satellite or a ship subjected to such tremendous accelerations.

 

[AtomicJoe]

This link* shows an interesting answer to the question of what escape velocity is when resistance is taken into account. It obviously depends on the shape, size, air density and drag coefficient of the projectile however the poster there concludes that for his hypothetical object escape velocity only increases from 11kps to 15kps.

Obviously HARP was discontinued but if the money was there a cannon capable of launching a projectile to orbit could be built. Why we would ever want to do that is another issue...

*http://physics.stackexchange.com/qu...stance-what-is-the-escape-velocity-from-earth

I read the escape velocity was mach 45 or 15 kps maybe they already too things into account.

 

[AtomicJoe]

Launch mechanism? You wouldn't want a satellite or a ship subjected to such tremendous accelerations.

Not a problem really is if a crew less satellite.

 

[Ryan_m_b]

I read the escape velocity was mach 45 or 15 kps maybe they already too things into account.

Escape velocity without atmosphere is 11kmps. With atmosphere it depends on the object but the link I gave above concluded 15kmps for the projectile listed.

 

[Ryan_m_b]

Not a problem really is if a crew less satellite.

A rocket gets to spread it's acceleration over minutes and tens-hundreds of km. A cannon would reduce this to barely seconds over hundreds of meters at best. The acceleration experienced by a cannon would be 2-3 orders of magnitude greater (potentially more) Satellites contain delicate and horrifically expensive equipment, you wouldn't want to fire it out of a cannon anymore than you would want to fire a cannon at it.

 

[AtomicJoe]

Seems to me the main problem is going to be the heat.

 

[AtomicJoe]

Escape velocity without atmosphere is 11kmps. With atmosphere it depends on the object but the link I gave above concluded 15kmps for the projectile listed.

Was it this link, if not here is another.
http://astroprofspage.com/archives/487

Leaves out the maths!

(until the end anyway).

 

[Ryan_m_b]

Seems to me the main problem is going to be the heat.

True. IIRC NASA's X-43 reached nose temperatures of over 1000 degrees and it was only traveling at mach 10.

Was it this link, if not here is another.
http://astroprofspage.com/archives/487

Leaves out the maths!

(until the end anyway).

The link is in comment 13

 

[AtomicJoe]

True. IIRC NASA's X-43 reached nose temperatures of over 1000 degrees and it was only traveling at mach 10.

The link is in comment 13

Indeed, and that would have been traveling at high altitude, ie over 30,000 meters.
The problem with a ground launch is the atmosphere is much thicker down there where it's speed must be highest.

I think it is fair to say that any projectile would have pretty much vaporised at such speeds.

I am not sure of the relationship between the speed and the temperatures but I doubt it is linear. I expect it is related to the square of the speed, thus you might be talking about
20,000 degrees. Which is almost 5 times higher than the melting point of any known material.

So it seems you will end up with a big puff of vapour.

 

[tedbmoss]

Back in the 1960's the Canadians and US Army built a gun at Yuma, AZ
see here http://www.astronautix.com/articles/abroject.htm
Supposedly it could hit the sun.

 

[DaveC426913]

Supposedly it could hit the sun.

Citation?

 

[AtomicJoe]

Citation?

Well it's a big target you could hardly miss it!

 

[AtomicJoe]

Interesting I am trying to find out some info about this harp gun.

Anyway from here:-
http://www.astronautix.com/stages/harpgun.htm


250 kg projectile accelerated at 13,000 peak G's to 2,300 m/s muzzle velocity

This 2,300 m/s is the fastest muzzle velocity I can find.

Anyhow those seem like the sort of speeds at which you will have serious heat problems perhaps, maybe also that is why the stopped the project.


Furthermore it seems this is not actually a gun at all!

It seems like it fires a rocket.

As you can see here it seems to be a gun fired rocket, which is ineligible!

http://www.astronautix.com/articles/abroject.htm

The altitude reported earlier of about 180km is wrong as it is no applicable to a gun.

 

[DaveC426913]

Furthermore it seems this is not actually a gun at all!

It seems like it fires a rocket.

As you can see here it seems to be a gun fired rocket, which is ineligible!

I wondered that too. No. They're just ballistic missiles.

Read.

 

[AtomicJoe]

So I expect it is possible to calculate a pretty much maximum possible height because I believe there comes a point at which the projectile is going to melt in the barrel with probably rather unpleasant consequences!

That was kind of the whole point of the initial thread.

So I think some of the comments aimed at me have been rather unfair.

 

[DaveC426913]

So I expect it is possible to calculate a pretty much maximum possible height because I believe there comes a point at which the projectile is going to melt in the barrel with probably rather unpleasant consequences!

That was kind of the whole point of the initial thread.

Except that that's simply an engineering problem. It is simply a matter of someone being clever enough to tinker with it until it goes faster.

For example, who needs a barrel at all?



("simply". Ha ha. The engineers are strangling themselves right now.)

 

[AtomicJoe]

Except that that's simply an engineering problem. It is simply a matter of someone being clever enough to tinker with it until it goes faster.

For example, who needs a barrel at all?



("simply". Ha ha. The engineers are strangling themselves right now.)

Well the problem seems to be that it needs to be fired at such a speed that projectile will burn up. That will it seems happen whether you have a barrel or not.

One way round it would be to use a bigger projectile or there would be something left after the melt but that just seems to scale up the problem.

I just can't see it being possible to escape Earth's gravity whatever method you use.

Getting rid of the barrel would create more problems than it solves I would imagine.