On 6/14/07, Charles D Hixson <[EMAIL PROTECTED]> wrote: (...)
Check your energetics. Asteroid mining is promising for space-based construction. Otherwise you'd better at least have controllable fusion rockets.
(...)
Not really. Elements that are incredibly rare on Earth - such as platinum group metals - could be mined in asteroids and simply dropped into Earth in round-of-the-mill reentry capsules - and those would't even need rocketry tech beyond the current level. Take in consideration that even a few tonnes of platinum - well below the weight of the space shuttle - would be of immeasurable value. As for "bulk" elements like iron, copper, nickel, etc, there are small asteroids - a few tens of meters in length - that could potentially have thousands of tons of those metals. My suggestion for that would be a controlled crash - simply boost the asteroid (using a mass driver or whatever) to a trajectory where it will be aerobraked by Earth's upper atmosphere (preferably over the ocean to avoid hazardous hypersonic booms over populated areas) and then, stripped of most of its kinetic energy, crash in an uninhabited area. Probably the crash will still look like a small nuke, but then we devastate similarly larger areas for comparable gains (as in the case of hydroelectric plants or extensive surface mining). By the way, talking about mining on Earth, some of the ore deposits currently explored are in fact ancient asteroid crashes... Finally, in the long term space elevators may well be possible, and then the limitation of bringing raw materials from space to Earth will be similar to the limitation of moving materials between continents using ships. ----- This list is sponsored by AGIRI: http://www.agiri.org/email To unsubscribe or change your options, please go to: http://v2.listbox.com/member/?member_id=4007604&user_secret=7d7fb4d8
