This innovative project will deliver a 100g MEMS (micro-electrical mechanical systems) accelerometer, bringing MEMS technology into the navigation grade inertial sector and providing UK sovereign capability in a key technology area. Operating in GPS denied environments has become a critical area of focus with Inertial Navigation (INS) providing a resilient tool based on accelerometers and gyroscopes. GPS denied does not only apply when signals are jammed but also other applications such as underwater navigation and tracking of personnel in buildings. IMU is a dual use technology with multiple civilian applications including autonomous vehicles, robotics and aerospace. SMG has spent 7 years of research and development on our resonant MEMS accelerometers and gyroscopes. MEMS is smaller, lighter and with lower power consumption than traditional technologies. MEMS can be volume manufactured with associated cost savings. Our vision is to deliver a matchbox sized, navigation grade IMU system which will be game changing in multiple markets. We are not there yet but we have now developed a 25G accelerometer with a total bias of 35µg which puts it at navigation grade performance. This proposal is to work with Collins Aerospace, a Tier One defence contractor, to develop a 100g navigation grade accelerometer and to bring it to market for the UK defence supply chain. At the end of this project we will have completed the technical development and taken the manufacturing level to MRL5\.

Understanding the subsurface is critical to rail construction. A better understanding can reduce the risk of unknowns, saving time and money through the design, construction and lifetime of rail assets. In the UK rail industry this is clearly demonstrated by HS2\. In HS2 Phase One naturally occurring karsts in the Chilterns have led to subsidence and adverse publicity for HS2\. For HS2 Phase 2 specific challenges lie ahead in Cheshire were old salt mines present a significant hazard as do old coal mines in the Black Country. Detecting underground voids poses a considerable challenge that requires specialised technologies. Various methods, such as ground penetrating radar, electromagnetics, and seismic surveys, are used but they have limitations and depend on specific environmental conditions. In this project, we proposed the utilisation of gravity surveying as a novel approach to identify subsurface hazards, offering several advantages over existing techniques such as immunity to environmental ground conditions. Gravity surveying involves measuring minute variations in gravitational forces to image the subsurface. Traditionally, it has been widely used in large area surveys conducted from aerial platforms. However, its application to smaller area surveys has been limited due to the lack of a user-friendly and commercially viable sensor. To address this gap SMG, has developed a portable gravity sensor based on resonant MEMS (Micro-Electro-Mechanical Systems) technology. In Phase One two types of subsurface hazard were identified in the Washings Area of the GCRE site. The first were shallow pipes which ran across the site but were not present on any maps. The second was old coal mine shafts at a depth of approximately 10m which are very difficult to detect and had only been found by drilling multiple boreholes. The feasibility study gravity forward modelled these hazards and showed that gravity sensing should be able to detect these hazards. There are likely to be other old coal minings on the site that remain unidentified and present a hazard for construction. This project builds on the feasibility study by proposing the gravity survey the majority of the Washing Area to a) demonstrate that gravity sensing can detect the known features and then b) survey the remainder of the site to look for presently unknown hazards. This will reduce the risk of unknowns during future construction, reducing cost and increasing assurance. The demonstration will have direct benefits for GCRE but also provide a case study for the global rail industry.

The need for new mineral resources is key to the energy transition away from hydrocarbons. Unfortunately many of the easy to find mineral deposits have been already exploited leaving the world with the challenge of finding new deposits for batteries and electrification. Magnetic and gravity sensing have long been identified as tools for detecting mineral deposits, but current sensors have operational limitations and when used, are deployed independently. Exploiting quantum properties in nitrogen vacancy diamonds, SB Quantum have developed a cutting-edge quantum magnetometer which provides vector analysis removing the need for careful orientation. The compact and rugged sensors can be fitted into autonomous vehicles. However magnetometry provides a non-unique solution so complimenting the magnetometry measurement with additional sensors is important. Gravity surveys have been used in the mining industry for many years but with traditional technology are time consuming and expensive to deploy. They cannot be deployed via drone / ATV or combined with other measurements. SMG have developed a next generation gravity sensor based on proprietary resonant MEMS sensors. The MEMS sensors are small, lightweight, more robust and low power consumption with very high sensitivity. Field trials of the hand portable gravimeter will start in the second half of 2023 with strong interest already demonstrated from a range of industries. This project will combine the two technologies in a drone deployed solution in order to expedite the adoption of both new technologies. The drone will be required to land to take stationary gravity measurements but will have the ability to survey large areas with significant granularity in commercially viable timescales. The co-location of gravity and magnetic sensors will bring benefits not only in time to survey but also for data interpretation. Combining Quantum and MEMS technology in an integrated package will expedite the adoption of the quantum technology. Combining the two technologies into a drone mounted acquisition system will need to address issues such as the impact of the drone and gravimeter on magnetic measurements with a need to mitigate impact. For the gravimeter self-levelling and elevation measurement to high degrees of accuracy will be critical. Form factor and power requirements for the combined device will need to be minimized. The consortium has validated the project objectives with major mining companies such as BHP and organisations such as the Geological Society of Canada and will set-up a steering group of customers.

Identifying subsurface hazards is a critical issue for railway construction. Finding unexpected features during construction can have major cost and time impacts. Similarly, if not identified hazards can cause subsidence and deformation during the life of the track. Subsurface hazards may be man-made such as old minings or tunnels or natural in the form of sinkholes or karsts which can form over time. Traditional site survey technologies such as ground penetrating radar, electro-magnetics and seismic are used extensively for site surveying but all have limitations. Gravity sensing has long been identified as a measurement which would add significant value to site surveys. Any subsurface feature that has a change in density will create a change in gravity. But until now a commercially viable sensing system has been lacking. Silicon Microgravity has spent seven years of research and development on MEMS relative gravimeters. A prototype surface system has been successfully tested at the National Buried Infrastructure Facility in 2021 and the commercial prototype will be available at the end of Q1 2023\. This Project is a feasibility study to determine the applicability of gravity surveying to GCRE but also to the wider rail construction industry. The proposed project will start by working with GCRE to identify potential subsurface hazards at the site and agreeing a set of scenarios. This will involve defining the type of the hazard, the depth, size, and density versus the surrounding material. This data will then be used to forward model the gravity anomaly that the hazard would create. This will then be evaluated versus the projected sensitivity of the SMG gravimeter to determine which hazards can be identified in a real-world scenario. Using the forward modelling, a gravity station survey program will be developed to determine optimal survey station data density for hazard detection over large areas. This will demonstrate the commercial viability of SMG gravity surveys for site surveys at GCRE and more broadly in the rail industry.

The Quantum Hive project is a joint initiative between the University of Birmingham (UoB) and Silicon Microgravity (SMG). It aims to deliver an innovative, viable way forward for commercialising the cold atom Quantum sensor developed at the UoB by adopting a hybrid approach with MEMS gravity sensors developed by SMG. Gravity sensors have historically struggled to gain commercial traction but by adopting a hybrid approach using the technical strengths of each sensor system will deliver a gravity sensing system which meets the end-users needs. The Quantum gravity sensor has the ability to a) provide levels of sensitivity unachievable today with MEMS sensors, b) measure with very low levels of drift and c) provide absolute gravity and gravity gradiometer measurements. However, its form factor, lack of mobility and cost provide a challenge where surveying of larger areas is required. MEMS gravity sensors lack the absolute accuracy of Quantum sensors and have larger drift levels but have a form factor, power consumption and cost which enable them to be deployed either as a single sensor or swarm on drones or autonomous vehicles, stopping to make measurements and then moving again. As a result of these different attributes, a hybrid approach can take advantage of the relative strengths to provide a truly innovative system for use in real world environments. The Quantum system will be used as a Base station providing an absolute gravity reference for the MEMS sensors. The Quantum Base station (the hive) will have limited mobility being either stationary or mobile of a rail. The MEMS sensors (the bees) will leave Base station on autonomous vehicles or drones, stop to take stationary measurements at pre-defined locations and then return to the Quantum Base for drift elimination. By adopting this hybrid approach, the project will meet the needs of the end customers who require gravity surveys over a large area in an acceptable time period and at a viable cost. End customers are multiple but include civil engineering companies, utilities, environmental organisations, carbon capture facilities and defence/security entities.

There is an increasing need to accurately measure movement and position in a broad range of applications including aerospace, automotive, robotics, underwater to name a few. Key to this are Inertial Navigation systems that do not rely on global positioning systems to measure movement and determine location. Within Inertial Navigation systems, the key technology is the Inertial Measurement Unit (IMU). An IMU is a combination of 3-axis accelerometers and 3-axis gyroscopes. Accuracy and specifically Bias Instability are key to delivering accurate positioning. Presently the high end IMU market is serviced by Fibre Optic Gyroscopes but these are large in size and costly. MEMS sensors have long been seen as a potential solution to this due to their small size and ability to be manufactured in large volumes. However, the present capacitance-based MEMS sensors do not have the performance required for the high-end IMU market. Silicon Microgravity is a spin-out of Cambridge University which is developing high-end accelerometers and gyroscopes based on its resonant vibrating beam MEMS technology. This project builds on its work on accelerometers and gravity sensors to develop a Navigation grade MEMS gyroscope with a Bias Instability of 0.01⁰/hr. This would be a breakthrough technology allowing MEMS for the first time to compete directly with solutions hitherto the preserve of specialised fibre optic gyroscopes.

"Despite our increasing ability to detect and monitor objects that exist on land, sea, around buildings or in space, our ability to detect objects beneath the ground has not improved significantly. When it comes to attempting to locate a buried and forgotten pipe, telling the extent of a sink hole or assessing the quality of infrastructure we still often resort to digging or drilling holes. This presents a huge economic and societal cost as road networks are dug up, oil wells are dry or brown-field land is left undeveloped. Existing techniques are all fundamentally limited in either their sensitivity (classical microgravity), their penetration (Ground Penetrating Radar) or their cost (seismic). For over 30 years, universities and academics have been exploiting the strange effects of quantum superposition to measure gravity with astonishing sensitivity. Using a process called cold-atom interferometry, the wave-partial duality of a rubidium atom is compared to the phase of a laser beam in a way which can detect very small changes in the way atoms fall freely in a vacuum. Changes in this free-fall can be used to determine the local strength of gravity and if this measurement is sensitive enough, the measurement can be used to tell whether there are voids, pipes, tunnels, oil and gas reserves in the ground beneath your feet. Although the potential is there, there are huge scientific and engineering challenges to delivering this performance. This project is proposed by the UK consortium of the best scientific and engineering companies the UK has to offer. Working with leading UK universities, these companies are looking to overcome these challenges, and develop a new industry of 'quantum' cold-atom sensors in the UK. If these advanced performances can be demonstrated, the economic and societal benefit of this new 'quantum' industry in the UK is expected to be significant and long-lasting."

Silicon Microgravity Ltd. is a spin-out from Cambridge University. The company has developed a high-performance microelectromechanical systems (MEMS) accelerometer with a projected resolution of 1 billionth the Earth's gravitational field. The company is currently developing a borehole gravity tool for oil and gas applications. This project seeks to establish relationships with overseas partners providing services and expertise in test facilities and modelling; as well as explore applications for the technology in other areas.

Awaiting Public Project Summary