PI-Terminal Planetary Defense

Terminal Planetary Defense

PI is a practical and effective method of planetary defense that allows for extremely short mitigation time scales as well as general use for longer warning time cases . 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 fragment cloud where the atmosphere acts as a “bullet proof vest” or “body armor”.  The effects of doing so are remarkable in their effectiveness. The key is to de-correlate the resulting acoustic blast waves on the ground and to take into account the optical signature due to fragment “burnup”.  Understanding both effects and and spreading the fragment cloud both spatially and temporally allows for virtually any threat to be mitigated. PI stands for “Pulverize It”.

The system allows a terminal defense solution to planetary defense 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 hours 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 or air burst, with the primary channel of energy going into spatially and temporally de-correlated shock waves. Compared to other threat reduction scenarios, this approach represents an extremely cost effective, testable, and deployable approach with a logical roadmap of development and testing. Pre-deployment of the system into orbit or a lunar base allows for rapid response on the order of less than a day if needed. 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 multi-hundred-meter diameter class and could virtually eliminate the threat of mass destruction caused by these threats. The great advantage of this approach is that it allows for terminal defense in the event of short warning times and target distance mitigation where orbital deflection is not feasible.

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https://www.deepspace.ucsb.edu/projects/pi-terminal-planetary-defense