Can Lasers Play a Ro^le in Planetary Defense?

It is now well‐established that a Near‐Earth Object (NEO) in the 5 to 10‐km size range extinguished the dinosaurs. Although such events have an impact interval on the order of 100 M years, a method of rapid response to such a threat is crucial, since warning time is short. Objects in the 0.1 to 1 km size range may not be detected before approaching within 1 to 10 astronomical units (AU) of Earth and, since their approach velocity may be 30–60 km/s, that situation leaves 100–300 days to respond. Although the most frequently suggested response to such a threat is a standoff nuclear detonation, physically delivered to the NEO, this paper finds significant advantages in retargeting, probability of success and even precise target location are possible with a high power laser alternative. Assuming a momentum coupling coefficient Cm = 3.5 dyn‐s/J and detection at 6.3 AU, a 770 kW repetitive pulse 355 nm laser (f = 1.7 ppm with 27 MJ, 10 ps pulses) will deflect a 200‐m‐diameter icy NEO sufficiently to avoid colli...