guest blogger john hare
Making use of off earth resources is a fairly constant topic of discussion. A recent Dennis Wingo comment made me think of a few paragraphs scattered through Mining The Sky by John Lewis. It is suggested that there are more asteroids in Jupiters’ Lagrange points than there are in the main asteroid belt. An asteroid has been found in a mars Lagrange orbit. Earth and Venus should be better collection points than mars. Earths’ L4-5 points are very difficult to see given the distance and sun angle. Lagrange points are actually volumes that could be millions of miles in diameter.
If I understood all the above correctly, it is possible that there are hundreds to thousands of asteroids in each earth sun L4-5 volume. They should be a cross section of types representing all known and unknown asteroid classes. This could represent one of the best possible concentrations of off earth wealth in the solar system for the next dozen generations. The points are at the same distance from the sun as the earth, so solar power and radiation are similar to that of the lunar surface.
If large numbers of asteroids of various types are semi-concentrated at 1 AU, a small probe could verify their existence with a flight path just sunward of the points. It could just miss the Lagrange focusing volume and keep going as an NEO spotter at distances well inside earths’ orbit if it turns out that the volumes are not worth exploring. The secondary mission of mapping NEOs that spend most of their time inside earths orbit would be worthy by itself. Those NEOs are exceptionally hard to spot from the earths’ surface. If the L4 or 5 volume is worth exploring though, a small burn could send the probe into the region for an extended survey of a concentrated resource base. The existence of the full spectrum of asteroid resources in one location would be of enormous value.
If a probe did locate large numbers of asteroids at the earth L points, a follow up sample return mission could visit dozens of bodies with quite modest propellant requirements. ISRU could possibly even occur at this early date if some available ice is located on one of the little bodies. A little bit of water could go a long way toward making the return trip more feasible. A small solar power system could crack it into H2 and O2 over a period of months, and be left behind for the next use. If hydrocarbons are located, then follow up missions could be even more efficient by using a small refinery to produce some cheaper form of fuel.
A serious manned prospecting mission could be more economically feasible than a mars mission, if enough resources are proved out in the robotic missions. It seems possible that metal rich bodies would be co-orbiting with volatile rich bodies and with enough other necessary ingredients to make an extended stay relatively self supporting. Water and minerals for a greenhouse, possibly Bigelow inflatable. Hydrocarbons as plastic and fuel feedstock. 24/7 solar power at earth normal concentration. Access to hundreds of locations that concentrated things with a mechanism totally different than terrestrial methods. Has it been proven that platinum must be parts per million mixed with something else? Is it possible that there is a process that concentrates precious metals to parts per hundred, or even pure chunks? I don’t know, and believe it possible that nobody else knows either for a definite fact.
If there is a serious material concentration at the earth sun L points, then a case can be made that a serious colony there would fare better than on mars. Both the raw materials and the zero gee for building SPS arrays would be at one basic volume of space at a constant distance from both the earth and sun. They could be drifted to GEO without going through the Van Allens, and provide power to the factory, moon, or solar sail of another vehicle by laser while in transit. The laser would be sent back to the factory for the next delivery with a microwave system installed for terrestrial power supply. Launch windows would be constant even though trip times would be fairly long. The two way supply pipeline could make constant use of whatever vehicles were tasked to the job.
Cyclers could be in constant use. I’m sure someone somewhere has worked the orbital numbers on a cycler with a one year elliptical orbit that arrived at both locations every year. It seems possible that there would be some special solar orbit that hit both L4 and L5 every year with earth access along the way, though I have no idea how to do it. Even though the trip times would be comparable to mars, the constant windows would allow a much higher usage rate of the ships involved.
There are thousands of NEOs with less time and delta V to reach from earth than the Lagrange points. A major question to me is how many of them have a diversified material availability that seriously leverages exploitation. How much time and money is required to prospect a dozen of them in a dozen orbits? Do any of them lend themselves to the complete process of life support, manufacture, and transportation of useful exports? Precious metals, complete SPS farms, exploration fuel base, and so on. It seems possible that no one body has the diversity to support a real off earth colony that is financially self sufficient, especially compared to a hundred or a thousand bodies.
If this is all wrong, then we can laugh at it all with little lost time. If there is something here worth looking into, then step one is to find the studies that must have been done already and look them over. Just because I haven’t seen any reference to this idea doesn’t mean that it hasn’t been checked out.