Alternative Navigation System for Hypersonic Vehicles in Global Positioning System (GPS)-Degraded and GPS-Denied Environment

Endo-atmospheric flight at hypersonic speeds creates an extraordinarily harsh aerothermal environment where an ionized plasma layer (or sheath) may surround some parts of the vehicle. Free electrons in the plasma, due to their relatively small mass, are able to rapidly reflect and/or absorb radio frequency (RF) signals, particularly within the GPS frequency bands. This is often referred to as “RF communication blackout” in scientific literature and has been experienced by reentry vehicles dating back to NASA’s early Apollo programs. As the Department of Defense (DoD) pushes offensive and defensive capabilities further into hypersonic regimes, GPS loss due to RF communication blackout. Overcoming the loss of or reliance on GPS provides significant risk mitigation to the national defense of the United States and greatly improves the overmatch capability of DoD systems. Typically, DoD systems have augmented GPS reliance with Inertial Navigation Systems (INSs) to overcome temporary loss or deterioration. INSs however are subject to navigational drift error over time. Navigation solutions using Geophysical Fields of the Earth (GFE) have been pioneered since prior to World War II. These GFE include the Earth Gravitational Field (EGF), Earth Magnetic Field (EMF), and Earth surface terrain. There exist multiple approaches to blending INS and EMF navigational data, for which the EMF constrains the drift of INSs. Further investigation shows multiple methodologies for Geomagnetic Matching Navigation (GMN) for rectifying the error of the INS. The IERUS approach is to implement a tactical grade INS capable of minimizing drift and blend this data with GMN to refine the accuracy and precision of the INS navigation solution. IERUS projects we can use Machine Learning (ML) to correct INS bias, improving state estimates. IERUS further proposes to incorporate ML to minimize or eliminate the interference effects of any plasma on magnetic field readings to gain more faithful total magnetic field readings. IERUS will then incorporate off-line trained magnetic field matching models within the navigation computer system for use on board vehicles.  The model will identify the data read by the onboard magnetometer and match to stored geomagnetic mapping.