Defence Evaluation And Research Agency Research Articles

Doing things of value [profile of Sir John Chisholm

Sir John Chisholm, the IEE's 2005/6 President, is a firm believer in the importance of realising the economic potential of scientific discoveries and enjoys a formidable reputation as a business strategist. His career started in the motor industry with Vauxhaul, where his research on control engineering got him into computers. Sir John then joined Scicon, a computer consultancy wholly owned by BP, where he thrived for a time, but when it became clear that BP was not interested in what he was doing, he left to set up CAP Scientific. When this company became 90% French owned, Sir John became a civil servant, taking responsibility for the bulk of the Ministry of Defence (MoD) research establishments as head of the Defence Research Agency (DRA). Sir John played a prominent part in reforming government procurement strategies and was involved in the creation of agencies such as DERA (Defence Evaluation and Research Agency) in 1995 and, in 2001, QinetiQ. The article concludes by looking at his principal hobby, vintage car racing.

TOPSAT – HIGH RESOLUTION IMAGING FROM A SMALL SATELLITE

The Topsat mission is designed to demonstrate the capabilities of small satellites for classically high value remote sensing missions. Conceived by the UK’s Defence Evaluation and Research Agency (DERA), it will produce 2.5 m resolution panchromatic imagery and 5 m resolution multispectral imagery in three visible wavebands and allow direct transmission of the image data to a local mobile ground station. The Topsat programme is jointly funded by the UK Ministry of Defence (MoD) and by the British National Space Centre’s Mosaic small satellite initiative and includes provision for the spacecraft, ground segment, commercial launch and one year of planned operations. The mission will meet the national needs of the UK in two areas. The UK MoD will use Topsat to investigate the utility and issues of providing data acquisition and tasking resources to local command levels. BNSC are supporting the programme as a demonstration of an enhanced capability for UK small satellites leading to sales of similar systems and to allow the development of lower cost markets for remote sensing products producible from such systems. The Topsat mission is a collaboration between four UK partners. DERA are leading the mission and providing the data handling unit, high rate downlink, mobile ground station and operations. Surrey Satellites (SSTL) are providing the spacecraft bus and command and telemetry links. Rutherford Appleton Laboratory (RAL) are developing a near diffraction limited wide field of view camera which, when combined with a pitch compensation manoeuvre, allows the highly demanding optical performance characteristics to be achieved. Infoterra are responsible for developing potential markets for Topsat and future derivatives.

Submarine Escape Trials 1999-2001 -Provision of Medical Support

Since the early 1960s all Royal Navy submarines have been fitted with an escape system comprising a single escape tower (SET) and submarine escape immersion suit (SEIS). This system enables escape from a submarine at a depth of 180 metres (1.9 MPa) provided that the submarine compartment is at a pressure of no greater than 1 bar (0.1 MPa). Due to a variety of causes which may include flooding and leakage of high pressure air systems it is the highly probable that the submarine compartment will be at a pressure in excess of 1 bar (0.1 MPa) at the time of the escape. To investigate and determine what constitutes a 'safe' maximum escape depth from any given compartment pressure (the safe to escape curve), a purpose built chamber complex, the Submarine Escape Simulator (SES) has been constructed at the QinetiQ, formerly the Defence Evaluation and Research Agency (DERA), Alverstoke site. Unlike escapes from a submarine where once released from the submarine the escapee's ascent can not be halted, within the SES it is possible to halt the ascent phase. This article describes the systems and procedures developed to enable medical support to be provided rapidly to a subject at any stage of the compression decompression profile. The article also provides details of the results to date that have been obtained from this work.

Porous silicon a useful imperfection

Abstract When semiconductor developers noticed in the 1950s that electropolishing of bulk silicon left certain areas rougher than the rest and somewhat porous, they regarded these simply as imperfect areas. It was not until Leigh Canham, a scientist with DERA (the UK’s Defence Evaluation and Research Agency), discovered in 1990 that porous silicon (PSi) emits visible light when activated by external ultraviolet sources 1 that this morphological state of the material came to attract significant research interest. Elementary photonic sensors were soon proposed. In 1992 researchers discovered that PSi also emits light when an electric current is applied, a finding that raised prospects for new optronic sensors and other devices coupling light to electronics, including future high-speed computers. Technology extensions have since been found that make the material chemi- and bio-luminescent as well as photo- and electro-luminescent. In sight by the mid- to late-1990s, therefore, was a whole new class of solid-state sensors offering significant advantages over solid-state gas and other sensors. Many of these were based on bulk silicon and semiconducting oxides such as tin or indium oxide and alumina. Compared with them, PSi offers a high surface area-to-volume ratio and hence high reactivity and, as researchers have established, a porous structure whose morphology could be engineered for high selectivity to particular molecules. Along with high sensitivity and selectivity, comes a rapid response time.

A Comparison of Laboratory-conditioned and Naturally-weathered Bonded Joints

Adhesive bonding is often the most desirable joining method in terms of structural efficiency and cost and is being used in an increasing number of civil and military applications. One of the main stumbling blocks to the further use of adhesive bonding is the lack of confidence in long-term durability, particularly in humid environments. When designing bonded joints, the effect of ageing is usually accounted for by subjecting the joints to artificially high levels of loading or extreme environmental conditions for short times prior to testing. However, the relationship between the results from these accelerated tests and actual long-term ageing is poorly understood. The Defence Evaluation and Research Agency (DERA) has what is probably a unique set of experimental data for a wide range of adhesively-bonded joints subjected to both accelerated ageing in the laboratory and long-term outdoor exposure. In this paper the relationship between the naturally aged and accelerated aged joints is explored. It is concluded that no simple correlation can be made between joints aged in different environments. The best that accelerated ageing can achieve is to eliminate those adhesives likely to perform badly in conditions of high humidity and to indicate those systems likely to perform well.

Nonuniformity correction and restoration of passive millimeter-wave images

We discuss methods of improving the quality and resolution of passive millimeter-wave images, particularly those obtained using the Defense Evaluation and Research Agency (DERA) MITRE imager and the more recent MERIT imager. This later real time imager consists of some novel optics followed by a conical scanner in the form of a disk rotating about an axis through its center and tilted with respect to its normal. A horizontal array of receivers is scanned such that each receiver performs a conical scan pattern in the scene. The resulting image, which has a 40x20 deg field of view, consists of a series of circles whose centers are uniformly displaced horizontally. Each receiver is calibrated initially using a two point correction but then drifts in time and a scene based correction is applied. Following preprocessing the images are superresolved using nonlinear restoration techniques. Two such techniques are described. The first is an error energy reduction algorithm that uses background subtraction and the second assumes a Lorentzian distribution of gradients within an image. Both are able to superresolve without significantly enhancing the noise. These various processes are described and images presented.

Investigation into the use of nonlinear predictor networks to improve the performance of maritime surveillance radar target detectors

Recent research has claimed that sea clutter is a chaotic process with a nonlinear predictor function. Indeed, results have been reported which demonstrate that sea clutter is nonlinearly predictable, and that this predictability can be exploited, using nonlinear predictor networks, to improve the performance of maritime surveillance radars. The aim of the paper is to investigate if nonlinear predictor networks can be used to improve the performance of maritime surveillance radars, using sea clutter data sets which were provided by the Defence Evaluation and Research Agency (DERA). By presenting prediction results for radial basis function network predictors, Volterra series filter predictors, and linear predictors, it is shown that the clutter predictor functions are well approximated by a linear function, and that nonlinear predictor networks provide little or no improvement in performance. A novel and effective training methodology was used for the radial basis function network predictors.

Modeling enhanced gas generation rates in a 155 mm ETC gun

The Defence Evaluation and Research Agency (DERA) is investigating a number of different electrothermal-chemical (ETC) gun concepts which utilize solid propellants. One of these concepts uses a capillary plasma generator (CPG). In the CPG concept, electrical energy (EE) is discharged into a polyethylene tube, open at one end only, through two electrodes which are located at each end of the capillary. Plasma vents from the open end of the capillary into a combustion chamber which contains a charge of solid propellant. This paper describes some modeling of 155 mm ETC gun firings that used the CPG concept. In these firings the EE was used either to ignite the charge or to augment the combustion process at pressures up to about 80 MPa. In order to simulate successfully these gun firings, it was necessary to assume that enhanced burning, due to the plasma, of the solid propellant occurred. This paper describes the modeling that was conducted for the 155 mm ETC gun firings and compares the simulations with measured results. The simulations were conducted using one-dimensional (1D) and two dimensional (2D) internal ballistics codes and investigate the zone of influence of the plasma.

UK electric gun national overview

This paper reviews the current state of electric gun research at the UK Defence Evaluation and Research Agency (DERA). A decade or so of paper studies and experimental trials have led to this point, and the future can be faced with the real prospect of practical weapon systems appearing on the battlefield of the future. Both electrothermal-chemical (ETC) and electromagnetic (EM) research are covered, outlining the emphasis in both areas and summarizing progress achieved. In EM trials, shots at over 2000 ms/sup -1/ have become commonplace, and the examination of recovered armatures has paid dividends in reducing the mass thereof, as well as confirming theoretical predictions. Work has begun to determine the in-bore forces on both the shot and the launcher-factors that read directly into improved designs. ETC research continues to develop the fundamental knowledge base required for the optimum design of ETC guns whilst the scope for gun system improvements based upon current knowledge is explored. Progress has been made toward a more complete understanding of plasma generators, the plasmas they produce and the interaction of plasma with propellant. A better understanding of these areas remains a goal of the ETC programme. The ability to evaluate ETC concepts has been enhanced by the commissioning and development of a 155 mm, 52 calibre experimental ETC gun.

Defence Evaluation and Research Agency (DERA)

Defence Evaluation and Research Agency (DERA)

A new closed vessel for determining the ballistic performance of high energy solid and liquid gun propellants

A new closed vessel, designed and build by Cranfield University under contract to the UK Defence Evaluation and Research Agency (DERA), is described. The jacketed vessel, which can be operated at high pressure (500 MPa) and has the capability of firing liquid monopropellants, is fitted with a single instrumented head and a detachable liner. The internal surface profile of the combustion chamber is shaped so as to prevent the build up of shock waves which can occur between parallel surfaces and this feature leads to improved output signal quality. Vessel venting following a firing is carried out by remote control via a proprietary air-actuated high pressure valve. The vessel can be fitted with optical windows or converted to a vented device for gas erosion studies.

Turbines for Peace

This article discusses that military-sponsored research tools can improve the machines that drive civil applications. The Defense Evaluation and Research Agency (DERA) researchers tested the engine of the legendary DeHavilland Vampire single seat jet fighter in the late 1940s. This Vampire is owned by Fred Ihlenburg, president of Yakity Yaks Inc., an importer of foreign military aircraft, based in Aurora, Oregon. DERA is investigating heat transfer on turbine blades to help gas turbine manufacturers develop a cooling system that will keep blades at an optimum temperature while minimizing losses in engine performance. More efficient cooling means less air is bled from the compressor, thus improving performance while extending blade life. This work was co-funded by the Central European Commission under the Brite Euram Fourth-Framework Initiative, which is part of the European Union’s strategy to enhance European global competitiveness, and Britain’s Department of Trade and Industry’s Civil Aircraft Research and Technology Demonstration Program. The British program aims to advance the capabilities of the United Kingdom’s civil aerospace companies.

High aspect ratio micromachining (HARM) technologies for microinertial devices

In this paper, we review work on novel, high aspect processes for microinertial components at the Defence Evaluation and Research Agency (DERA). High aspect components may lead to significant cost-performance improvements in both accelerometers and gyroscopes. We have evaluated 3 low temperature process technologies – silicon on insulator (SOI) HARM, UV electroforming and bulk HARM. Prototype microinertial devices fabricated in these technologies are also presented. The potential of the processes for integration with on-chip CMOS electronics is assessed which may be either as part of a fully integrated MEMS process or as “value-added” post-processing on commercial CMOS wafers. Bonded SOI (BSOI) materials has been specially designed for micromachining applications to give a low stress material that is optimised for a sacrificial release process. Trench isolation is achieved by deep dry etching to the buried dielectric. These trenches may be refilled to allow metallisation to reach isolated components. Structures with aspect ratios of up to 50:1 have been realised using a combination of photolithography, deposition and deep dry etching. CMOS compatibility has been demonstrated. The process is an attractive manufacturing technology. Electroforming of nickel in resist moulds formed using conventional UV photolithography has also been investigated. Some of the early limitations with this technology have been overcome by using a new resist technology, SU8. The process needs to mature further, but remains a promising candidate. Bulk HARM uses deep dry etching of a bulk silicon membrane which is defined using wet etching. Device isolation is difficult and process control complex making this the least attractive of the technologies.

The STAR system: an interactive pronunciation tutor for young children

Between 1990 and 1998, the Speech Research Unit at the Defence Evaluation and Research Agency (DERA), and Hereford and Worcester County Council Education Department, a U.K. local education authority, conducted research into the use of speech recognition technology in an interactive computer-based pronunciation tutor for 5–7 year-old primary school children. The goal of the project was to develop a robust, autonomous system that would enable a child to practice the pronunciation of a given set of words by speaking them to a computer, which provided immediate feedback on whether the pronunciation was acceptable. This paper describes the development of the underlying speech recognition technology, the prototype real-time system which was developed, and the results of pilot trials of the system in a U.K. primary school.

Experimental research into human cognitive processing in an augmented reality environment for embedded training systems

Research into human factors issues associated with the use of augmented reality (AR) technology is very limited. Consequently, there is a need for formal human factors design guidelines to underpin the integration of AR into systems. The Defence Evaluation and Research Agency (DERA) Centre for Human Sciences (CHS) is evaluating the potential of AR for providing real-time training feedback in future advanced embedded training systems for the military. In order to understand the important human factors issues of augmented reality, DERA funded the Advanced VR Research Centre (AVRRC) at Loughborough University to investigate the cognitive ergonomics of this technology. An important aspect of this research is concerned with identifying any human information processing issues that may arise when information is presented via AR and overlaid upon one or more primary display surfaces such as a visual display unit (VDU). Two main issues are addressed in this research. First, the impact of AR on human information processing and second, subjective workload experienced when displaying information via the AR medium. The experiments reported in this paper assess issues of reaccommodation and reaction times to alarms on different display formats. They demonstrate also that AR performs as well as standard display formats.

Future satellite communications to military aircraft

This paper outlines some of the techniques being developed to provide affordable, reliable satellite communications suitable for a wide range of military aircraft, from agile platforms such as fast jets and helicopters to surveillance, tanker and transport aircraft. It gives an overview of the development of airborne SHF and also extremely high frequency (EHF) satcom techniques and terminal demonstrators by the DERA (Defence Evaluation and Research Agency) and its partners through the Ministry of Defence's applied research programme. This research is aimed at providing affordable, secure and robust satcoms to a range of UK military aircraft.

The STRV family of spacecraft

In 1990, the Space Department of the Defence Evaluation and Research Agency (DERA) initiated the Space Technology Research Vehicle (STRV) programme. The aim was to design, build, test and launch a relatively low-cost satellite weighing only 50kg and carrying a variety of experimental payloads derived primarily from MoD-sponsored research within the Department. What is the status of this programme 10 years later?

The single-event-effect behaviour of commercial-off-the-shelf memory devices-A decade in low-Earth orbit

This paper presents the results of a 10-year study on radiation effects in commercial-off-the-shelf (COTS) memory devices operating within the on-board data handling systems of five low-Earth orbiting micro-satellites, designed and built at the University of Surrey (UoS). The ionising particle environment inside three of these spacecraft has been investigated concurrently using radiation monitoring payloads developed by UoS and the Defence Evaluation and Research Agency (DERA). Through the use of these monitoring instruments, and an allied programme of ground-based testing of the memory devices, the industry-standard computer models of the radiation environment have been verified, and the memory device behaviour has characterised with respect to single-event (SEEs) due to galactic cosmic-rays, geomagnetically trapped particles, and solar particles.

DERA takes aim at MMC advances

Developing metal matrix composites for both defence and civilian applications is part of the extensive research activities undertaken by the UK's Defence Evaluation and Research Agency (DERA). Increasingly, the organization is looking to involve private industry in its endeavours. Simon Pickering visited Dr Alan Shakesheff at DERA's Structural Materials Centre within the Mechanical Sciences Sector in Farnborough to find out more.

Combined GPS/GLONASS LAAS flight trials

The use of GPS in aviation is now accepted, with extensive work being undertaken on the technological, precision and infrastructure requirements. Work has focused on providing a service that is able to operate continuously in all areas. GPS alone, however, is seen as being unable to satisfy the stringent requirements for some phases of flight. Of the many solutions proposed, the Russian GLONASS system has been regularly overlooked. The research described in this paper aims to present GLONASS as a realistic and proven augmentation to GPS for aircraft positioning. During October 1996 the Civil Aviation Authority (CAA) Institute of Satellite Navigation (ISN) at the University of Leeds, in conjunction with the National Air Traffic Services Ltd (NATS UK) and the Defence Evaluation and Research Agency (DERA), performed a series of landmark differential GPS/GLONASS flight tests using the DERA BAC 1-11 flying laboratory. A real-time differential system was constructed using two GPS/GLONASS receivers developed by the ISN and a C-band data link for the RTCA corrections. Integration onboard the aircraft with avionic sensors and flight management systems was achieved using the ARINC 429 protocol. Routes were designed and flown to evaluate the complete system over a variety of airborne dynamics for both en-route and approach situations. In total, over 16h of flying time was recorded, including 30 runway approaches over nine flights. A thorough evaluation of the accuracy and integrity of the positioning system was performed. Emphasis was made in comparing the flight statistics with recognized Required Navigation Performance (RNP) figures. The paper describes in detail the project development and the results achieved. An analysis of the results, showing that aircraft positioning with GPS/GLONASS augmentation in a local area augmentation system (LAAS) scenario can achieve accuracies that are both comparable with GPS-alone solutions and can satisfy up to CAT II precision approach criteria, is presented. Results are also given for position propagation using velocities derived from GPS and GLONASS carrier phase measurements.