Beyond GPS

By Mychaela Kekeris, Boeing Writer

Boeing completed the world’s first recorded flight test of multiple quantum sensors in 2024, enabling an in-flight airplane to navigate without GPS for four hours.

Although quantum sensors for navigation have been researched in laboratory settings for years, the test was the first known operation of the sensors on an airplane during flight. That and subsequent flights produced real-time navigation data, which is needed to field any application of the technology.

The quantum navigation system does not typically experience the temporary disruptions in service that can arise with current GPS or other navigational systems. The quantum navigation system’s accuracy could enable airplanes on commercial routes to navigate without GPS for the entirety of flight.

Measuring success

The team conducted the test using a six-axis quantum inertial measurement unit (IMU). The IMU was integrated into a full inertial navigation system and deployed on a Beechcraft 1900D for the series of flight tests. A quantum IMU is designed to be more accurate than conventional IMUs. The improved accuracy can lead to reductions in navigation errors from tens of kilometers at the end of a long flight to as little as tens of meters.

The flight test out of St. Louis showed conclusively that the quantum sensors were able to operate successfully through takeoff, landing and multiple maneuvers.

“Boeing is leading the development of quantum technology that will help improve flight safety,” said Ken Li, Boeing Principal Senior Technical Fellow and principal investigator for quantum navigation.

Quantum qualifications

Boeing collaborated with California-based AOSense to design and build the quantum IMU.

“We designed our quantum IMU for robust operation in harsh environments, and we are pleased to confirm that during the flight test the sensor performed along all input axes much as we predicted,” said AOSense president Brenton Young. AOSense has been developing quantum sensors since 2004.

How it works

The IMU uses a quantum-sensing technique called atom interferometry to detect rotation and acceleration using atoms, providing navigational accuracy and precision without a GPS reference.

The IMU consists of three quantum inertial sensors, each of which measures single-axis accelerations and rotations of the airplane. The IMU keeps track of the path the airplane has taken from its initial position. Boeing engineers integrated the quantum inertial sensors with additional sensors and hardware to ensure reliable performance in flight. The result was the first known quantum-enabled navigation system of its kind.

Quick to quantum

“The ability to safely operate in GPS-denied environments is critical to both defense and commercial applications,” said Todd Citron, Boeing chief technology officer. “This flight test shows Boeing’s innovative approach to leveraging quantum technologies for operationally relevant challenges.”

Rapid iteration and testing enabled the Boeing and AOSense team to advance technology from three single-axis sensors operating in a laboratory environment to a quantum IMU operating in flight over a span of only 15 months. During this period, the team conducted multiple laboratory, ground vehicle and flight tests, each focused on identifying improvements to increase the sensor’s capability and reliability.

“Such rapid advancements indicate great promise for quantum sensors to be part of the next generation of navigation sensors,” said Jay Lowell, Boeing Principal Senior Technical Fellow and quantum technology research manager. “This flight test is a historic first step in that direction.”

Star tracker

The flights also tested Boeing’s All Source Positioning, Navigation and Timing (ASPNT) software. The software combines information from multiple GPS-denied navigation sensing modalities, including vision-based navigation, terrain-referenced navigation, gravity-anomaly-referenced navigation, magnetic-anomaly-referenced navigation, a star tracker, and signal of opportunity (SOOP) at various levels of technology readiness levels.

In addition to the quantum IMU, the flights tested two other sensors: AQNav, a full stack quantum navigation system from SandboxAQ, and a day-time-capable star tracker that Boeing developed with  HRL Laboratories. Pairing AQNav with the star tracker was key to developing magnetic-anomaly-referenced navigation technology.    

The star tracker provided precise attitude and position references to support the flight tests. The star tracker’s shortwave infrared (SWIR) technology is also a unique development. Compared with star trackers used in military systems 50 years ago, the Boeing-designed system is smaller, weighs less, uses a fraction of the power, and realizes better performance.

Two telescopes, together with the SWIR cameras, form the main portion of the star tracker. The star tracker mounts next to a custom window that is transparent to SWIR light, making the star tracker operable.

Magnetic measurement

AQNav uses the Earth’s magnetic field to compare real-time measurements to a premapped magnetic field. This approach, combined with the data from the IMU, significantly anchors IMU drift by limiting potential navigation errors through a process that correlates the aircraft’s trajectory with the observed magnetic data.

AQNav helps to ensure navigation deviations remain within an operational margin. This results in a highly reliable and accurate alternate navigation system that effectively curbs error accumulation over time, which is critical for flying in areas where GPS signals are unavailable. Designed to be unjammable, unspoofable, 24-hour, all-weather, and terrain-agnostic, AQNav is a passive technology that operates in the background without user interaction.

“Rapid advances were greatly accelerated thanks to Boeing’s collaborative approach and their exceptional ability to integrate with SandboxAQ,” said AQNav senior hardware engineer Eddie Rodriguez. “This strong partnership, combined with our expertise in artificial intelligence modeling, allowed us to deliver an enhanced system and demonstrate its capabilities within just six months.”

What's next

Boeing will conduct a series of laboratory tests to help understand how the quantum IMU navigation sensors behave under certain environmental conditions, such as temperature and vibration. These tests will provide data for Boeing and AOSense engineers to improve the quantum navigation system’s performance, robustness and reliability.  IQ