Roberto Gorelli points our attention at a recently published meteor related paper:

Terminal Planetary Defense

This article has been submitted by Philip Lubin.


Abstract: We present a practical and effective method of planetary defense that allows for extremely short mitigation time scales. The method involves an array of small hypervelocity kinetic penetrators that pulverize and disassemble an asteroid or small comet. This effectively mitigates the threat using the Earth’s atmosphere to dissipate the energy in the fragment cloud. The proposed system allows a planetary  defense solution using existing technologies. This approach will work in extended time scale interdiction modes where there is a large warning time, as well as in short interdiction time scenarios with intercepts of minutes to days before impact. In longer time intercept scenarios, the disassembled asteroid fragments largely miss the Earth. In short intercept scenarios, the asteroid fragments of maximum ~10-meter diameter allow the Earth’s atmosphere to act as a “beam dump” where the fragments either burn up in the atmosphere and/or air burst, with the primary channel of energy going into spatially and temporally de-correlated shock waves. It is the de-correlated blast waves that are the key to why PI works so well. Compared to other threat reduction scenarios, this approach represents an extremely rapid response, testable, and deployable approach with a logical roadmap of development and testing. The effectiveness of the approach depends on the time to intercept and size of the asteroid, but allows for effective defense against asteroids in the 20-1000m diameter class and could virtually eliminate the threat of mass destruction caused by these threats. A significant advantage of this approach is that it allows for terminal defense in the event of short warning times and short target distance mitigation where orbital deflection is not feasible. Intercepts closer than the Moon with intercept times of less than a few hours prior to impact are viable depending on the target size.
As an example, we show that with only a 1m/s internal disruption, a 5 hours prior to impact intercept of a 50m diameter asteroid (~10Mt yield, similar to Tunguska), a 1 day prior to impact intercept of 100m diameter asteroid (~100Mt yield), or a 10 day prior to impact intercept of Apophis (~370m diameter, ~ 4 Gt yield) would mitigate these threats. Mitigation of a 1km diameter threat with a 60-day intercept is also viable. We also show that a 20m diameter asteroid (~0.5Mt, similar to Chelyabinsk) can be mitigated with a 100 second prior to impact intercept with a 10m/s disruption and 1000 second prior to impact with a 1m/s disruption. Zero-time intercept of 20m class objects are possible due to atmospheric dispersion effects. Predeployment of the system into orbit or a lunar base is another possibility. The product of the mitigation time and the disruption speed is the key metric. Larger disruption speeds allow for even shorter mitigation times.
Using the Moon as a planetary defense outpost with both detection as well as mitigation (launch) capability is one option to be considered for the future to protect the Earth as are LEO, MEO and GEO deployment. The Moon is nearly ideal given the lack of atmosphere allowing for long range optical/NIR LIDAR detection, and the low escape speed allows for rapid launch and interception capability using existing solid fuel boosters. For an Earth launch-based system, we show that a single heavy lift launcher such as a Falcon Heavy, Starship, SLS etc. can conservatively mitigate a multi-hundred-meter diameter asteroid such as Apophis or Bennu. Pro-active mitigation of recurring threats is also an option. Having such a capability would allow humanity for the first time to take control over its destiny relative to asteroid and comet impacts. A similar system could also be employed for human bases as we spread out into the solar system. The specific implementation depends on the location such as lunar with no atmosphere or Mars with a much less dense atmosphere. 

You can download this paper for free: (137 pages).


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