1. 1 RF Blackout During RLV Reentry: Public Safety Implications COMSTAC RLV Working Group Pradipta Shome 17 May 2007 Federal Aviation Administration

2. 2 High reentry velocity Steep angle of attack Body shape contributes to electron density Velocity is the major determinant of flow field temperature and level of ionization Onset of blackout ~ 300,000 ft and 25,000 ft/sec End of blackout approx 80,000 ft and 18,000 ft/sec ATC Implications Maintain continuous communications Summary of conditions that lead to blackout 2 Title of Presentation (This text must be edited in the Master Slide) Name or Date Federal Aviation Administration 2 2 Radio Frequency Blackout During RLV Reentry Federal Aviation Administration 2

3. 3 Orbital vehicles slated to come before AST in near future may be subject to blackout; e.g. Rocketplane Kistler OV and SpaceX two-stage reusable booster. Future RLVs could remain in attenuated or blackout mode for extended periods, during a critical phase of the flight Sub-orbitals might not blackout fully but experience communication degradation To meet public Safety concerns, may need to maintain: - Communications for telemetry and vehicle control - Navigation and Tracking of vehicle Why we should care 3 Title of Presentation (This text must be edited in the Master Slide) Name or Date Federal Aviation Administration 3 3 Radio Frequency Blackout During RLV Reentry Federal Aviation Administration 3

4. 4 Future Concerns Blackout remains a concern for space vehicles during critical phase of flight Need to derive feasible frequency bands from atmospheric and plasma attenuation considerations If frequency band is chosen, how to implement in spectrum management scheme  Spectrum plan may be changing  Spectrum is a finite resource  Spectrum allocation is a lengthy process Title of Presentation (This text must be edited in the Master Slide) Name or Date 4 4 Title of Presentation (This text must be edited in the Master Slide) Name or Date 4 4 4 4 Title of Presentation (This text must be edited in the Master Slide) Name or Date Federal Aviation Administration 4 4 Radio Frequency Blackout During RLV Reentry Federal Aviation Administration 4