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Research Questions

  1. What is known about the technical characteristics of the South Korean activist groups' balloons?
  2. What can be said about the probable effectiveness of the balloons?
  3. Could North Korea shoot down the balloons, if it made a concerted effort to do so?
  4. In an era of personal drones, what technical improvements are likely in the use of unmanned air vehicles by activist groups?

For a number of years, various activist groups in South Korea have used hydrogen balloons — and, more recently, hexacopter drones — to carry political, religious, and humanitarian materials across the border into North Korea. The balloon delivery techniques have evolved over time, and the activist groups are overtly interested in new technologies to pursue their goals. This report reviews open-source reporting to assess the technical state of balloons and drones as means of delivering material into North Korea. It also compares efforts in Korea with Cold War efforts to achieve similar goals in Central and Eastern Europe and assesses plausible technological developments that might improve the airborne delivery of contraband.

Key Findings

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.

Research conducted by

This project is a RAND Venture. Funding was provided by gifts from RAND supporters and income from operations. The research was conducted by the RAND Center for Asia Pacific Policy (CAPP), part of International Programs at the RAND Corporation.

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