If a dinokoller asteroid was spotted on collision course for Earth with impact in the next ten years, it would be a race to divert it. I happen to disagree with many of my friends here that everyone would pull together to solve the problem. I happen to believe that all too many of the would be working their own agenda at the expense of us all. I also believe that many would oppose any effort to avert disaster with the belief that we would only make things worse, or possibly even that we planned on taking a near miss and turning it into a bulls eye strike on an enemy. Enemy can be anyone in the world if you go deep enough into the paranoia that tends to exist in many places.
In my opinion, what we need is a series of methods of mitigating the potential disaster of a real strike. This post is a thought experiment for using almost entirely ISRU resources with equipment that could be in space within the next decade without bankrupting the organization that funds it. By using assetts that are already in space, and under the control of people with real expertese in operating those resources, the possible political and hysteria roadblocks can be mitigated to a considerable degree.
The first set of assetts that absolutely must be developed is a survey of every reasonable threat to this world. Earth and space based telescopes and databases have to be developed in such a way that a comprehensive knowledge of every Earth crossing body of above a thousand tons or so is known and mapped for the foreseeable future. Second is to find and map orbits on the smaller bodies and bodies that intersect the potential dangerous Earth crossers. It would be cold comfort knowing that Humanitykiller One was caused by two ‘safe’ rocks that collided in such a way as to send either or both of them our way. Only after a thorough catalogue is available can we say with reasonable certainty that no danger exists within some given time frame.
The second set of assetts is an affordable and robust transportation industry to at least LEO and hopefully cislunar space as well. Developing asteroids is dependant on the first and would benefit hugely by the second. A fledgling asteroid development industry would vastly improve the Dinokiller diversion effort I am going to suggest, and a mature one would make protection trivial.
My suggestion this time is that a fully mapped NEO inventory could use one asteroid to bump another off course. If a gigaton rock were going to hit Earth in a few years, then a diversion of a single meter per second would make it miss by a substantial amount. A meter per second is 3.6 km/hr, which is 86 km/day, which is over 30,000 km/year. While theoretically a few months might be enough to save the Earth, I would prefer a lot more margin.
Say this gigaton rock named Eight Ball is scheduled to land in the Earth pocket in October 2025. A second asteroid named Cue Ball orbits inside of Earths orbit and has a near miss with Eight Ball in January 2024. A mining operation is diverted to Cue Ball in 2022 to fully characterize its’ orbit, mass and composition. In the meantime a comprehensive survey expedition is sent to Eight Ball. Both teams follow transponder units that have been sent ahead to tag both bodies in order to nail their orbits down to within a few meters at any given time for the next decade. By the time both missions arrive, it has been firmly established that Eight Ball will strike Earth on October 11, 2025 at 9:35 PM Grenwich time with the center somewhere in Iowa. The daylight strike will obliterate the US instantly with the rest of the world to follow in short order.
Cue Ball is determined to mass a megaton itself and has a rubble pile composition. A large boulder or bag of pebbles is lifted off the surface of Cue Ball and suspended a short distance above the surface, The mining ship reels out enough tether to be well clear of both the bag of material and the asteroid itself. Using solar sails or ion engines or both, the mining ship uses the ISRU material as a gravity tractor to change the orbit of Cue Ball. With a constant track of orbits of Cue Ball and Eight Ball, the adjusted orbit is changed enough that Cue Ball will strike Eight Ball dead center on January 15 2024.
The mining ship stays to Shepperd Cue Ball all the way to impact. With a megaton of rubble impacting a gigaton of asteroid at 10 km/sec, the orbit of gigaton Eight Ball, or its’ resulting rubble, should change by an average of 10 m/sec. If everything went according to plan, Eight Ball, or its’ debris field, should miss Earth outside the orbit of the moon.
The mining ship for Cue Ball is now in the wrong orbit to follow the results, but the survey expedition to Eight Ball can stay on site for a while after the impact to assess the result. If Eight Ball has been determined to now be in a safe orbit, the survey expedition does a comprehensive after strike analysis of the results. Any useful and readily available materials are collected for return to whichever facility seems appropriate for research or exploitation.
If Eight Ball has not been safed, then the survey expedition must go to diversion plan two. Diversion plan two is the one you suggest.