The large accelerations experienced by a ballistic projectile would likely mean that a space gun would be incapable of safely launching humans or delicate instruments, rather being restricted to freight or ruggedized satellites.
Atmospheric drag also makes it more difficult to control the trajectory of any projectile launched, subjects the projectile to extremely high forces, and causes severe energy losses that may not be easily overcome. A space gun with a "gun barrel" reaching above the lower troposphere, where the atmosphere is most densely packed, may mitigate the issue.
A space gun, by itself, is generally not capable of placing objects into stable orbit around the planet.
If acceptable solutions to these fundamental issues could be achieved, a space gun could offer access to space at an unprecedented low cost.
[edit] Getting to orbit
A space gun, by itself, is not capable of placing objects into stable orbit. The laws of gravitation make it impossible to reach a stable orbit without an active payload which performs orbital correction burns to change the shape of its orbit after launch. The orbit is a parabolic orbit, a hyperbolic orbit, or part of an elliptic orbit which ends at the planet's surface at the point of launch or another point. This means that an uncorrected ballistic payload will always strike the planet within its first orbit unless the velocity was so high as to reach or exceed escape velocity.
Isaac Newton avoided this objection in his thought experiment by positing an impossibly tall mountain from which his cannon was fired. The projectile, however, would still tend to circle the planet and strike the point of launch.
As a result, all payloads intended to reach a closed orbit would have to perform some sort of course correction to create another orbit that does not intersect the planet's surface. The amount of fuel carried would thus reduce the payload-to-fuel ratio, decreasing the efficiency and increasing the complexity of such a system. It is conceivable that in a multi-body gravitational system, like the earth-moon system, that a trajectory could be found that does not re-intersect the earth's surface, although these paths would likely not be very simple nor desirable, and would require much more energy.
Saturday, February 6, 2010
space elevator
With a space elevator, materials might be sent into orbit at a fraction of the current cost. As of 2000, conventional rocket designs cost about $11,000 per pound ($25,000 per kilogram) for transfer to geostationary orbit.[62] Current proposals envision payload prices starting as low as 100$ per pound ($220 per kilogram)[63], similar to the $5-$300/kg. estimates of the Launch loop, although nowhere near the $310/ton to 500km orbit quoted[64] to Dr. Jerry Pournelle for an orbital airship system.
Philip Ragan, co-author of the book "Leaving the Planet by Space Elevator", states that "The first country to deploy a space elevator will have a 95 per cent cost advantage and could potentially control all space activities."
Philip Ragan, co-author of the book "Leaving the Planet by Space Elevator", states that "The first country to deploy a space elevator will have a 95 per cent cost advantage and could potentially control all space activities."
also from wikipedia
There are three options for mining:
1. Bring back raw asteroidal material.
2. Process it on-site to bring back only processed materials, and perhaps produce fuel propellant for the return trip.
3. Transport the asteroid to a safe orbit around the Moon or Earth. This can hypothetically allow for most materials to be used and not wasted.
Processing in situ for the purpose of extracting high-value minerals will reduce the energy requirements for transporting the materials, although the processing facilities must first be transported to the mining site.
Mining operations require special equipment to handle the extraction and processing of ore in outer space. The machinery will need to be anchored to the body, but once emplaced the ore can be moved about more readily due to the lack of gravity. Docking with an asteroid can be performed using a harpoon-like process, where a projectile penetrates the surface to serve as an anchor then an attached cable is used to winch the vehicle to the surface, if the asteroid is rigid enough for a harpoon to be effective.
There are several options for material extraction:
1. Material is successively scraped off the surface in a process comparable to strip mining. There is strong evidence that many asteroids consist of rubble piles,[8] making this approach feasible.
2. Asteroids with a high metal content may be covered in loose grains that can be gathered by means of a magnet.[9]
3. For volatile materials in extinct comets, heat can be used to melt and vaporize the matrix.[10]
4. A mine can be dug into the asteroid, and the material extracted through the shaft. This requires a transportation system to carry the ore to the processing facility.
Due to the distance from Earth to an asteroid selected for mining, the round-trip time for communications will be several minutes or more, except during occasional close approaches to Earth by near-Earth asteroids. Thus any mining equipment will either need to be highly automated, or a human presence will be needed nearby. Humans would also be useful for troubleshooting problems and for maintaining the equipment. On the other hand, multi-minute communications delays have not prevented the success of robotic exploration of Mars, and automated systems would be much less expensive to build and deploy
..............
Mining the Sky: Untold Riches from the Asteroids, Comets, and Planets is a book by John S. Lewis which discusses the development of interplanetary space within our solar system.
Lewis makes a prediction that the abundant resources of the solar system, including effectively-limitless solar energy, could support a vast civilization of 1016 people. He argues that shortage of resources is "...an illusion born of ignorance."
Lewis calculated the value of M-type asteroid 3554 Amun at US$20 trillion: US$8 trillion worth of iron and nickel, US$6 trillion worth of cobalt, and US$6 trillion in platinum-group metals.[1] Since the book was published, the value of platinum, for example, has tripled
1. Bring back raw asteroidal material.
2. Process it on-site to bring back only processed materials, and perhaps produce fuel propellant for the return trip.
3. Transport the asteroid to a safe orbit around the Moon or Earth. This can hypothetically allow for most materials to be used and not wasted.
Processing in situ for the purpose of extracting high-value minerals will reduce the energy requirements for transporting the materials, although the processing facilities must first be transported to the mining site.
Mining operations require special equipment to handle the extraction and processing of ore in outer space. The machinery will need to be anchored to the body, but once emplaced the ore can be moved about more readily due to the lack of gravity. Docking with an asteroid can be performed using a harpoon-like process, where a projectile penetrates the surface to serve as an anchor then an attached cable is used to winch the vehicle to the surface, if the asteroid is rigid enough for a harpoon to be effective.
There are several options for material extraction:
1. Material is successively scraped off the surface in a process comparable to strip mining. There is strong evidence that many asteroids consist of rubble piles,[8] making this approach feasible.
2. Asteroids with a high metal content may be covered in loose grains that can be gathered by means of a magnet.[9]
3. For volatile materials in extinct comets, heat can be used to melt and vaporize the matrix.[10]
4. A mine can be dug into the asteroid, and the material extracted through the shaft. This requires a transportation system to carry the ore to the processing facility.
Due to the distance from Earth to an asteroid selected for mining, the round-trip time for communications will be several minutes or more, except during occasional close approaches to Earth by near-Earth asteroids. Thus any mining equipment will either need to be highly automated, or a human presence will be needed nearby. Humans would also be useful for troubleshooting problems and for maintaining the equipment. On the other hand, multi-minute communications delays have not prevented the success of robotic exploration of Mars, and automated systems would be much less expensive to build and deploy
..............
Mining the Sky: Untold Riches from the Asteroids, Comets, and Planets is a book by John S. Lewis which discusses the development of interplanetary space within our solar system.
Lewis makes a prediction that the abundant resources of the solar system, including effectively-limitless solar energy, could support a vast civilization of 1016 people. He argues that shortage of resources is "...an illusion born of ignorance."
Lewis calculated the value of M-type asteroid 3554 Amun at US$20 trillion: US$8 trillion worth of iron and nickel, US$6 trillion worth of cobalt, and US$6 trillion in platinum-group metals.[1] Since the book was published, the value of platinum, for example, has tripled
from wikipedia
In 2004, the world production of iron ore exceeded a billion metric tons.[4] In comparison, a comparatively small M-type asteroid with a mean diameter of 1 km could contain more than two billion metric tons of iron-nickel ore,[5] or two to three times the annual production for 2004. The asteroid 16 Psyche is believed to contain 1.7×1019 kg of nickel-iron, which could supply the 2004 world production requirement for several million years. A small portion of the extracted material would also contain precious metals.
In 2004, the world production of iron ore exceeded a billion metric tons.[4] In comparison, a comparatively small M-type asteroid with a mean diameter of 1 km could contain more than two billion metric tons of iron-nickel ore,[5] or two to three times the annual production for 2004. The asteroid 16 Psyche is believed to contain 1.7×1019 kg of nickel-iron, which could supply the 2004 world production requirement for several million years. A small portion of the extracted material would also contain precious metals.
02 06 10
Hello and welcome to what I hope will become a community of like minded people interested in talking about the near term future of space.
Here are a few of the key points, which are obviously subject to update and revision
1. Space can and will be developed by humans
2. Where there is profit, man is sure to take extreme risks in order to obtain it
3. The learning curve is steep, but not impossible to overcome
4. How we can hope to become personally wealthy by understanding the trends
thank you for looking at this blog
Here are a few of the key points, which are obviously subject to update and revision
1. Space can and will be developed by humans
2. Where there is profit, man is sure to take extreme risks in order to obtain it
3. The learning curve is steep, but not impossible to overcome
4. How we can hope to become personally wealthy by understanding the trends
thank you for looking at this blog
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