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Balloons' Probable Effectiveness

• Modeling suggests that balloons launched under favorable wind conditions can potentially penetrate deep into North Korea.
• But based on anecdotal reports, the balloons do not fly far across the border very often.
• It may be that the balloons are "saturating" the border area with leaflets but not fulfilling their full potential to reach larger areas of the country.

North Korean Air Defenses

• The balloons typically fly at an altitude of around 3,000 m, where they can be engaged by North Korean antiaircraft guns. Shooting down the balloons would be neither drastically cheaper nor drastically more expensive than launching the balloons, so a "war of attrition" would be about equally expensive for both sides.
• However, if the balloons were frequently shot down, activists could adjust tactics and fly the balloons higher, out of gun range.

Possible Technical Improvements

• Changes that substantially improve the effectiveness of leaflet delivery might be worthwhile even if they cost up to a few hundred dollars per balloon and/or take up a significant fraction of the payload weight.
• Activist groups could improve their success rate by choosing launch conditions more judiciously, with the aid of high-altitude wind forecasts.
• Adding pressure relief valves to prevent overpressurization of the balloons seems like a cheap improvement that could enable better flight times and better penetration.
• The use of powered drones has begun with hexacopters and could be extended to longer-range drones. Because these platforms are relatively expensive, their success may depend on finding relatively undefended points to enter and exit North Korea.
• A balloon-released glider is a more exotic but not entirely undemonstrated concept that could combine some of the more attractive features of balloons and controlled drones.