Revised-Strategy

Revising the Space Colonization Strategy
by Dave Dietzler 2009
The original space colonizaton strategy proposed by Gerard K. O'Neill and others in the seventies involved using Space Shuttle derived heavy lift launch vehicles to land 3,000 to 20,000 tons of mining equipment and mass drivers on the Moon. A construction shack would be built in LEO and propelled to L5. Lunar materials would be launched with mass drivers to mass catchers at L2 then these materials would be hauled to L5 and workers at the construction shack would build a huge Bernal Sphere space colony to house 10,000 workers. Workers would ride the Space Shuttle to LEO and then travel aboard a space liner propelled by solar electric mass drivers to the L5 space colony and commence building solar power satellites with lunar materials. Aluminum was thought to be the primary construction material for SPS, the space colonly and spaceships. I propose several revisions to this scenario:
1) The Space Shuttle is soon to be retired. Ares launchers and perhaps Space X corporation Falcon launchers should be used.
2) Rather than land 3,000 to 20,000 tons of equipment on the Moon it would be more economical to land a "seed" of several hundred to several thousand tons of equipment consisting of small robotic mining shovels and solar wind implanted volatiles harvestors, inflatable habitat and work chambers, solar panels, 3D sintering devices, machine tools, etc. Lunar materials would be used to replicate and expand the industrial seed and build larger and larger pieces of equipment including mass drivers.
3) Raw metals and finished parts would be launched from the Moon to build robotic asteroid mining ships at the L5 construction shack. The human crews at the shack would teleoperate robots in space, go EVA only when necessary, and robots would also be teleoperated by Earthside crews. The robotic ships would then retrieve small NEOs and nudge them back to high Earth orbit. The ships would use clusters of VASIMR drives instead of mass drivers with high exhaust velocities to achieve low mass ratios or high mass fractions; otherwise we would be launching more mass from the Moon just for reaction mass than we obtained from small NEOs!
4) Metallic asteroids that are 85% iron-nickel and 15% rock along with carbonaceous asteroids will be dismantled with lasers, electron beams or focused solar energy to obtain materials for powersat construction. Iron and carbon will be combined using the old blister steel also called cementation process to make steel. Since steel has a higher strength to weight ratio than aluminum alloy and a much higher specific strength than unalloyed aluminum (there is very little to alloy aluminum with in space), steel powersats will actually amass less than aluminum powersats of the same strength. Since the powersats might be rotating in order to gyroscopically stabilize them and keep them aimed at the Sun, they will endure some structural stress and high strength will be important. Steel is also easier to weld than aluminum and titanium and it is easier to cold work than titanium. With iron rich M-Type and carbon rich C-Type asteroids an abundance of steel will be available in outer space. Both types of asteroids will supply silicon for solar panels if solar photovoltaic systems are used on powersats. By using small NEOs much less material has to be mined on the Moon, launched to L2 and hauled to L5.
5) Teleoperated robots controlled by crews in the construction shacks, on the Moon and on Earth should do most of the work rather than human beings in space, thus the 10,000 man space colony can be dispensed with or postponed to a time in the more distant future. This will greatly simplify and accelerate the building of powersats and making money by private space enterprises.
6) Since a heat engine working in space can take advantage of the super cold of outer space to achieve nearly ideal Carnot efficiency we must examine the possibilities of using turbines or Stirling motors to run generators on powersats rather than silicon solar panels. Power to weight ratios must also be considered. Solar thermal powersat designs must be compared to solar photovoltaic powersat designs in every way before the job is tackled.
7) If a small NEO goes off course due to some kind of malfunction of the robotic ship propelling it back to high Earth orbit or L5 there is a slight chance that it will slam into the Earth and create a disaster. Asteroid deflection systems consisting of gravity tugs perhaps should be erected in space as part of this project to do away with this possibility and asteroid deflection systems should be built anyway due to the real danger of a natural asteroid impact on Earth that would be catastrophic.
8) In addition to asteroid mining and powersat construction, fleets of large colony ships to Mars could be built as part of a continuing program to explore the solar system and terraform Mars to create a second planetary home for humanity. Development on the Moon could also lead to more lunar research, astronomy, farside SETI and space tourism