Space gun

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Space gun

Postby mahesh on November 6th, 2017, 6:04 am 

In 1992, I submit mathematical detail idea of space gun to NASA & ISRO. They appreciated that thoughts but problem is atmosphere. If anything moves suddenly with orbital velocity then it disintegrate. Spaceship will collide with dense atmosphere. This problem can be solve if we move gun to the upper atmosphere.
I am putting this new idea for discussion.
here, short paper is attached.
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Re: Space gun

Postby BurtJordaan on November 13th, 2017, 2:46 am 

This is not much different from a conventional multistage launcher, putting multiple small satellites into space. I do not see any benefits, but think it will need more propellant due to vertical "gravity drag". The final delta-V for orbital velocity needs to be delivered approximately horizontal, in order to avoid that drag.
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Re: Space gun

Postby mahesh on November 13th, 2017, 5:02 am 

1)Even ground artillery shell trace the parabolic trajectory when fire from ground & trajectory of rocket which fire satellite in space also trace curve trajectory because gravity always try to pull the trajectory in horizontal direction.
Only difference is in gun fire shell get all velocity in one stroke & in rocket this velocity is increases in stages.
2) In both cases vertical force component is require to overcome gravity drag component. So, rocket also overcome that drag.
3) Gun have some draw backs like human can not remain in that acceleration or for final trajectory correction this requires some additional fuel but human always achieves which is impossible.
4) In space, main thing get avoided is atmosphere which is main problem for NASA & ISRO when I send them proposal of ground base space gun in 1992, as given in www.maheshkhati.com
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Re: Space gun

Postby JMP1958 on November 13th, 2017, 12:10 pm 

mahesh » November 13th, 2017, 2:02 am wrote:1)Even ground artillery shell trace the parabolic trajectory when fire from ground & trajectory of rocket which fire satellite in space also trace curve trajectory because gravity always try to pull the trajectory in horizontal direction.
Only difference is in gun fire shell get all velocity in one stroke & in rocket this velocity is increases in stages.
2) In both cases vertical force component is require to overcome gravity drag component. So, rocket also overcome that drag.

There is actually a large difference between a rocket and a gun in terms of trajectory. Rockets follow a path that is called a gravity turn. As the rocket climbs, and is still firing its engines, it leans more and more towards the horizontal so that its thrust and thus its acceleration is directed more and more in the horizontal direction. A rocket's velocity also increases over the course of its flight so that it will have achieved orbital velocity upon reaching the correct altitude.

A gun shell follows a ballistic path. It starts out fast and loses velocity as it climbs. And while you can have the trajectory flatten out so that it is horizontal to the ground at a given altitude, by the time it get there it will not have enough velocity to maintain an orbit. If you try to compensate by just giving it more muzzle velocity, this increases the altitude at which the trajectory becomes horizontal, but the velocity lost in gaining that extra height will still leave you short of orbital speed. There is nothing you can do about this, it is just the way orbital mechanics work.

Of course if the muzzle velocity is high enough, you could achieve escape velocity, but now we are talking about at least 11 km/sec (loses due to air drag would make it even higher.). And even from the top of the highest mountain, the air friction would be too much. Meteors start burning up as high as 120 km, which is already a good part of the altitude of a low Earth orbit.
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Re: Space gun

Postby Braininvat on November 13th, 2017, 1:04 pm 

Wouldn't most payloads, unless we are talking metallic ores or other sturdy raw materials, be considerably damaged by a ballistic approach like that? Immense delta-V right at the start of the trip is not too good for cargo. Plus, it's cheaper to extract raw materials from asteroids or moons with shallower gravity wells. And, as JMP and others noted, meteoric burning is a big problem. Magnetic railguns might work, but only on the moon or similar.

For people, Arthur Clarke's space elevator seems a better way to go, and materials science is going to be reaching tensile strengths needed for the cables and such.
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Re: Space gun

Postby BurtJordaan on November 13th, 2017, 2:47 pm 

Braininvat » 13 Nov 2017, 19:04 wrote:Wouldn't most payloads, unless we are talking metallic ores or other sturdy raw materials, be considerably damaged by a ballistic approach like that? Immense delta-V right at the start of the trip is not too good for cargo.

Mahesh's idea was to use a combination of conventional rocket launch with a gun to replace the second and/or third rocket stages, i.e. at above the bulk of the atmosphere. The problem is that the energy required to lift the whole contraption to above most of the atmosphere dominates the equation, so the gun gains very little, if anything. And it creates the problems that you have highlighted.

Nice topic for discussion, but very little practical value, I think.
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Re: Space gun

Postby mahesh on November 14th, 2017, 3:56 am 

Main advantage of gun is explosion of gun powder push the shell very hard in barrel of gun due to sudden wave type expansion of gases. This gives very high velocity to shell suddenly. Nasa's general estimate is 3 bags of explosive in gun is sufficient to put satellite in lower orbit & 5 bags will be sufficient to give escape velocity for medium satellite.
in case of rocket, gases comes out from tail gives backward push to rocket but density of gases are very low. So, we require very large amount of fuel to burn continuously to get require continuous push. This require very heavy size of rocket to lift the relatively small satellite. Also, initial fuel burn to lift next level of require fuel in rocket.
So, combination of two may avoid negativity in both system.
This is my thought, I may be wrong.
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Re: Space gun

Postby bangstrom on November 14th, 2017, 5:27 am 

Around 1960, I recall reading about artificial satellites in an encyclopedia and an article stated that Werner von Braun in the USA attempted to launch a satellite into orbit in the mid fifties sometime before Sputink. The satellite was a solid aluminum pellet fired from a gun mounted on top of a V2 rocket. The launch went as planned but the aluminum pellet was never detected so there is no way of knowing if it went into orbit or not.
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Re: Space gun

Postby Braininvat on November 14th, 2017, 11:18 am 

Isn't explosive force less efficient a means of using chemical energy as a propellant? All the chemical energy from a thruster contributes to impulse, and combustion can be made highly efficient when the propellant is slowly used up in a rocket engine. But an explosion wastes some material and part of the force will heat and deform the base of the launching tube. Unless maybe it's composed of neutronium. :-)
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