DARPA Veloci-RapTOR: Redefining Velocity Measurement with Force Sensors

For decades, measuring velocity has relied on external references like GPS or lasers. But what if we could ditch the external clutter and measure velocity directly through a platform’s internal forces? This is the ambitious goal of the Defense Advanced Research Projects Agency’s (DARPA) Veloci-RapTOR program.

Velocity measurement is critically important in a military context as it directly influences the accuracy and effectiveness of navigation, targeting, and situational awareness systems. Precise velocity data enables military vehicles, aircraft, and missiles to maintain course, execute maneuvers, and engage targets with high precision, reducing the risk of collateral damage and increasing mission success rates. Current methods of velocity measurement, which rely on external references such as GPS, can be compromised by jamming or spoofing, posing significant vulnerabilities in contested environments. DARPA’s  Veloci-RapTOR program addresses this need by aiming to develop self-contained, force-based velocity measurement systems that can operate independently of external signals, thereby enhancing the reliability and resilience of military operations in diverse and challenging conditions. This advancement would provide a robust solution for maintaining operational superiority and ensuring the success of critical missions in the face of evolving threats.

The Current Landscape of Velocity Measurement

Current methods of measuring velocity predominantly rely on external references and signals. These methods include:

• GPS and other human-made reference signals: They provide accurate velocity measurements but depend heavily on external infrastructures.
• Reflectometry methods (radar, lidar, sonar): These systems measure the reflection of signals off surfaces to determine velocity, which can be affected by environmental noise and clutter.
• Flow measurements (Pitot tubes): Common in aviation, these measure the flow of air to determine velocity but are susceptible to environmental conditions.

The fundamental limitation with these traditional methods is their reliance on external factors, making them prone to noise and clutter. Additionally, physics does not permit absolute velocity measurements; only relative velocities can be measured, necessitating an external reference point.

The Challenge: Isolating the Tiny Signal of Speed

Traditional methods struggle because velocity is inherently relative. You can only measure how fast something is moving compared to something else. This necessitates external references that introduce noise and complexity.

Veloci-RapTOR takes a radical approach. It explores whether force sensors can isolate the miniscule velocity-dependent forces from the much larger background noise experienced by the platform. It’s like finding a whisper amidst a roar.

The Solution: Leveraging Physics and Modulated Force Sensors

The Veloci-RapTOR Hypothesis

Veloci-RapTOR (Velocity via Rapid Transduction Of Relative-motion) aims to revolutionize how we measure velocity by leveraging force sensors to detect velocity-dependent forces. These forces are minuscule compared to the larger forces exerted on a platform, often referred to as “clutter.” The core hypothesis is that force sensors, when modulated by charge or mass, can isolate these tiny velocity-dependent signals from the overwhelming background noise.

The program centers around a clever hypothesis: By modulating the charge or mass of a force sensor, we can amplify the tiny velocity-dependent signal and separate it from the background clutter.

Force Sensors: The Backbone of Veloci-RapTOR

Numerous force sensor technologies can potentially meet Veloci-RapTOR’s objectives. These include:

• Atomic, ionic, and molecular sensors
• Cavity opto-mechanical systems
• Micro-electromechanical systems (MEMS)

The challenge lies in achieving precise force measurements with a high dynamic range while modulating charge or mass to isolate the velocity-dependent force.

Veloci-RapTOR will explore various force sensor technologies, with a focus on achieving two key goals:

• High Dynamic Range: Separating the weak velocity signal (think a feather) from the massive background forces (think an elephant) requires an exceptional dynamic range. Veloci-RapTOR aims to achieve this through modulated force sensors.
• Sensitivity vs. Control: There’s a delicate balance between precisely controlling the force sensor’s mass or charge and maintaining high sensitivity. Veloci-RapTOR needs to overcome this trade-off.

Leveraging Fundamental Forces

Veloci-RapTOR will exploit two well-known physical phenomena tied to the earth reference frame:

1. The Lorentz Force: This force acts on an electrically charged particle moving through a magnetic field. When charges within a substrate move relative to the earth’s magnetic field lines, a current is induced, providing a measurable force. When a charged object moves through a magnetic field (like Earth’s), it experiences a force. Veloci-RapTOR proposes embedding charged particles within a sensor. By modulating the charge and measuring the resulting current, the program aims to extract velocity information.
2. The Coriolis Force: This force is due to the earth’s rotation and affects a mass moving relative to the earth’s rotational vector. The force experienced by the moving mass can be measured and linked to velocity. Veloci-RapTOR will explore using controlled masses within the sensor to exploit the Coriolis effect for velocity measurement.

A Fundamental Research Program with Ambitious Goals

Veloci-RapTOR is a fundamental research program. Proposers will be challenged to develop their own metrics to track progress towards:

• Demonstrating a force transduction mechanism that can extract velocity.
• Isolating the velocity-dependent force from background noise.
• Achieving a velocity measurement.
• Developing a model for 1 mm/s velocimetry (extremely precise speed measurement).

Overcoming Key Challenges

Veloci-RapTOR faces two significant challenges:

1. Isolation/Dynamic Range: Defense Department platforms experience ambient clutter forces ranging from 10010^0100 to 10510^5105 N, while the velocity-dependent forces are as small as 10−2510^{-25}10−25 to 10−1510^{-15}10−15 N. Identifying the velocity-dependent signal amidst 15 orders-of-magnitude larger noise requires innovative methods. Modulating charge or mass is hypothesized to be a viable solution.
2. Sensitivity vs. Control: Balancing exquisite charge and mass control with superb sensor sensitivity is a critical tradeoff that Veloci-RapTOR aims to address.

Objectives and Scope

Veloci-RapTOR’s primary goal is to determine if a force-based measurement can achieve velocity extraction and signal isolation. Key program metrics include:

• Demonstrating a force transduction mechanism consistent with velocity extraction
• Isolating the velocity-dependent force from other forces using a control parameter in the force transduction measurement
• Achieving a demonstrable velocity measurement
• Developing a model/design consistent with 1 mm/s velocimetry

Methodologies deviating from the proposed force transduction mechanism but meeting these objectives are also considered within scope.

Program Structure

Veloci-RapTOR will be conducted in a single project phase of up to 24 months, structured as follows:

1. First Six Months: Focus on developing the theory and models behind the Veloci-RapTOR approach.
2. Remaining 18 Months: Develop and demonstrate a prototype in a fielded setting.

Each proposer team can receive up to $2,000,000 in funding for the project.

Conclusion

Veloci-RapTOR seeks to fundamentally change how velocity is measured by leveraging force sensors to isolate velocity-dependent signals from background clutter. By harnessing the Lorentz and Coriolis forces, Veloci-RapTOR aims to achieve unprecedented precision in velocity measurement, opening new possibilities for defense and commercial applications alike