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The increased participation in elite wheelchair sport has provided the need to investigate the physiological requirements of wheelchair sporting competition and daily wheelchair propulsion. However, from a nutritional perspective, guidelines that have been established from the able-bodied population tend to be used by the practitioners working in disability sport and it is not known whether this information is directly transferable to the wheelchair athlete. Wheelchair sport is complex and athletes differ with respect to their sports classification based on factors relating to disability and functional capacity. Therefore, if nutritional guidance is required to optimise performance then information regarding energy expenditure (EE) in the wheelchair sports population becomes important for specific feedback. The aim of this thesis was to investigate EE in wheelchair athletes. The results from Chapter 3 found resting energy expenditure (REE) in tetraplegic athletes to be lower than that calculated using predictive equations derived from an ablebodied cohort. However, paraplegic athletes showed comparable values to those which were predicted, suggesting these equations may be of use in paraplegic athletes. Chapter 4 extended this work and found similarities in the REE of the two aforementioned cohorts. This could have been due to the similarities that were found in their total-body fat free mass (FFM). The results from Chapter 5 showed EE reduced after both a short 36 minute exposure of wheelchair propulsion and after 3 weeks of wheelchair propulsion practice in novice wheelchair users. Temporal parameters improved after the practice period, suggesting there is an association between EE and propulsion technique. Chapter 6 extended these findings with results confirming that experienced wheelchair users expended significantly less energy during wheelchair propulsion than novice individuals who had up to 3 weeks practice. It is clear that EE of daily wheelchair ambulation should not be a generic value and different levels of experience must be considered so that the nutritional needs can be tailored accordingly. Chapters 7 and 8 examined the physiological demands of elite competitive wheelchair basketball players in relation to the International Wheelchair Basketball Federation (IWBF) classification categories and identified differences in the physiological demands and physiological fitness of wheelchair basketball and tennis players. These results found that IWBF Class 3 - 4.5 (high point) players expended more energy per hour during competition than those with a lower classification (IWBF Class 1 - 2.5). However, when actual playing time was considered the low classification group showed a similar EE to the higher classification group. Furthermore, wheelchair basketball players had a higher EE per hour than wheelchair tennis players during elite competition. However, the wheelchair tennis players spent a significantly longer duration on court resulting in similar EE during a typical competition within each sport. This suggests nutritional advice should be tailored both to the duration of competitive play (where EE may be similar between sports (basketball vs. tennis)); and to training (where athletes with a higher functional capacity may have higher EE). This thesis revealed several important physiological considerations to appreciate when investigating the EE of wheelchair sportsmen and women. Findings would suggest that type of disability, wheelchair propulsion experience and sport classification are all important considerations for the accurate assessment of EE in this cohort of athletes.

Radical aircraft and propulsion system architecture changes may be required to continue historic performance improvement rates as current civil aircraft and engine technologies mature. Significant fuel-burn savings are predicted to be achieved through the Distributed Propulsion concept, where an array of propulsors is distributed along the span of an aircraft to ingest boundary layer air and increase propulsive efficiency. Studies such as those by NASA predict large performance benefits when integrating Distributed Propulsion with the Blended Wing Body aircraft configuration, as this planform geometry is particularly suited to the ingestion of boundary layer air and the fans can be redesigned to reduce the detrimental distortion effects on performance. Additionally, a conventional aircraft with Distributed Propulsion has not been assessed in public domain literature and may also provide substantial benefits. A conceptual aircraft design code has been developed to enable the modelling of conventional and novel aircraft. A distributed fan tool has been developed to model fan performance, and a mathematical derivation was created and integrated with the fan tool to enable the boundary layer ingestion modelling. A tube & wing Distributed Propulsion aircraft with boundary layer ingestion has been compared with a current technology reference aircraft and an advanced turbofan aircraft of 2035 technology. The advanced tube & wing aircraft achieved a 27.5% fuel-burn reduction relative to the baseline aircraft and the Distributed Propulsion variant showed fuel efficiency gains of 4.1% relative to the advanced turbofan variant due to a reduced specific fuel consumption, produced through a reduction in distributed fan power requirement. The Blended Wing Body with Distributed Propulsion was compared with a turbofan variant reference aircraft and a 5.3% fuel-burn reduction was shown to be achievable through reduced core engine size and weight. The Distributed Propulsion system was shown to be particularly sensitive to inlet duct losses. Further investigation into the parametric sensitivity of the system revealed that duct loss could be mitigated by altering the mass flow and the percentage thrust produced by the distributed fans. Fuel-burn could be further reduced bydecreasing component weight and drag, through decreasing the fan and electrical system size to below that necessary for optimum power or specific fuel consumption.

Most manual wheelchair users will experience upper extremity injury and pain during their lifetime, which can be partly attributed to the high load requirements, repetitive motions and extreme joint postures required during wheelchair propulsion. Recent efforts have attempted to determine how different propulsion techniques influence upper extremity demand using broad measures of demand (e.g., metabolic cost). However studies using more specific measures (e.g., muscle stress), have greater potential to determine how altering propulsion technique influences demand. The goal of this research was to use a musculoskeletal model with forward dynamics simulations of wheelchair propulsion to determine how altering propulsion technique influences muscle demand. Three studies were performed to achieve this goal. In the first study, a wheelchair propulsion simulation was used with a segment power analysis to identify muscle functional roles. The analysis showed that muscles contributed to either the push (i.e. delivering handrim power) or recovery (i.e. repositioning the hand) subtasks, with the transition period between the subtasks requiring high muscle co-contraction. The high co-contraction suggests that future studies focused on altering transition period biomechanics may have the greatest potential to reduce upper extremity demand. The second study investigated how changing the fraction effective force (i.e. the ratio of the tangential to total handrim force, FEF) influenced muscle demand. Simulations maximizing and minimizing FEF both had higher muscle work and stress relative to the nominal simulation. Therefore, the optimal FEF value appears to balance increasing FEF with minimizing upper extremity demand and care should be taken when using FEF to reduce demand. In the third study, simulations of biofeedback trials were used to determine the influence of cadence, push angle and peak handrim force on muscle demand. Although minimizing peak force had the lowest total muscle stress, individual stresses of many muscles were >20% and the simulation had the highest cadence, suggesting that this variable may not reduce demand. Instead minimizing cadence may be most effective, which had the lowest total muscle work and slowest cadence. These results have important implications for designing effective rehabilitation strategies that can reduce upper extremity injury and pain among manual wheelchair users. / text

Spinal Cord Injuries (SCIs) are debilitating injuries where damage to the spinal cord causes a loss of mobility and feeling in muscles innervated below the injury point. Tetraplegia refers to an SCI in the cervical region of the spinal cord that impacts on the functionality of all four limbs. ‘Complete’ tetraplegia results in complete paralysis of the legs, partial or complete paralysis of the arms and trunk, and in the most severe cases, the neck. The independence of people living with tetraplegia is heavily dependent on assistive and mobility devices. Understanding the strength characteristics of people with tetraplegia is crucially important for the suitable and effective design of mobility and rehabilitative devices such as wheelchairs. A study using a stationary dynamometer and video capture measured kinetic and kinematic characteristics of wheelchair propulsion for 15 subjects with C5-C7 tetraplegia. This study differentiated between subjects with different injuries, at two different test resistances, and was more comprehensive than other reported studies on MWC propulsion. Some of the subjects in the study with C5-C6 injuries had no elbow extension capability, while others had undergone a deltoids-to-triceps tendon transfer procedure called TROIDS, which restores some elbow extension capability. No differences were found in any of the push phase metrics between those who had undergone the TROIDs procedure, and those who had not, suggesting that TROIDs provides no significant benefit for mobility. As expected, subjects with C7 tetraplegia recorded velocity and power outputs significantly higher than those for subjects with C5-C6 tetraplegia. To better understand the strength characteristics over the full range of motion in the sagittal plane, and thus potentially modify the design of mobility devices to better suit these characteristics, a novel method for gathering strength data in multiple directions and positions was developed. This method had advantages over other commonly used methods. In particular, it was inclusive of complex muscle and joint interactions that would otherwise be very difficult to build into a model. Sagittal horizontal push strength was measured using this method for 8 able bodied and 4 tetraplegic subjects. There were clear trends in the data from the able-bodied subjects, and a fourth order polynomial (R-squared = 0.8) was fitted to the data for modelling purposes. Data for the tetraplegic subjects varied significantly from the able-bodied data, but inter-individual variation was such that no model would provide a satisfactory fit to the data indicating a very high degree of patient-specific behaviour. One multi-directional data set, consisting 1584 measurements in the sagittal plane, was gathered for an able-bodied subject. The main trends in this measured data were successfully captured by a model consisting of twelve fourth-order polynomials. Building on these measurements, and employing a human model in the constraint modelling environment, SWORDS, this thesis develops a conceptual design tool for comparing the effectiveness of different hand force paths. Initial simulations using hypothetical hand paths indicated that the proposed method for predicting the direction of the applied force needs to be verified, and likely refined, for hand paths that differ significantly from the traditional wheelchair push-rim path. This proposed procedure has the potential to be a powerful tool for optimising and modifying the design of wheelchairs or human powered devices to utilise previously untapped abilities for any given population.

The PEGASES thruster (Plasma Propulsion with Electronegative Gases) is a novel type of electric thruster for space propulsion. It uses negative and positive ions produced by an inductively coupled radio frequency discharge to create the thrust by electrostatically accelerating the ions through a set of grids. A magnetic filter is used to increase the amount of negative ions in the cavity of the thruster. The PEGASES thruster is not only a source to create a strongly negative ion plasma or even an ion-ion plasma but it can also be used as a classical ion thruster. This means that a plasma is created and only the positive ions are extracted and accelerated making it necessary to neutralize the plasma behind the acceleration stage like in other ion thrusters. The performances of the PEGASES thruster have been investigated mainly in xenon in order to compare the obtained results with RIT-type ion thrusters. The thruster has been investigated with the help of a variety of probes such as a Langmuir probe, a planar probe, a capacitive probe and a RPA (Retarding Potential Analyzer). In addition, an ExB probe has been developed to measure the velocity of the ions leaving the thruster and to differentiate between the ion species present in the plasma.

This master thesis represents a life cycle impact assessment of a state of the art electrically driven power train. It is expected to be installed in a diesel engine passenger ferry boat, currently transporting passengers in downtown Stockholm archipelago. The assessment has a comparative character in between the currently operating and the new power train in order to differentiate and recognize which of the two propulsion options is the environmentally preferable choice. The scope of the study is directed towards the thorough examination of both power trains so that it can represent most closely the two specific technological cases. Studied and assessed were the three main life cycle phases of each power train – raw materials acquisition and manufacturing, use phase and end of life phase. The fundament of the study involved creating environmental models for each and every component of the drive trains, the propulsion fuel and energy used, and the services related to waste treatment in the last phase of their functional life. The environmental models were later used to build live cycle inventories that served to derive the respectful impact from the item analyzed. The data used to model the battery electric power train was provided directly from the manufacturer, where the end of life procedures carried out were assumed where possible. The main battery pack for the electric power train was not modeled in terms of  end of life procedures due to insufficiency of information. Almost no generic information was available to model the diesel engine and it was calculated by creating auxiliary simplified cad models. The rest of the data required to achieve an environmental inventory regarding the power train was available from a subcontractor. Both studied options were modeled with allocation approach that includes the avoided production of materials at the waste treatment stage where there was sufficient information to do that. There was none to model the main battery packs avoided production which is a major component of the battery electric system. To model the use phase of the diesel engine power train, research data regarding combustion emissions and waterborne emissions was utilized. A number of electricity mix models were applied to create a sensitivity analysis of the operation phase of the battery electric power train. Chosen for baseline scenarios simulating the use phases of both power trains are use of Nordel market electricity mix and the combustion of low sulfur diesel with five volumetric percent rape methyl ester additive. For the purposes of the assessment eighteen midpoint impact indicators were used to cover the areas of global warming potential, human health and quality of eco systems. The results from the study show that the estimated impact from both power trains is small enough to have almost no influence on the results from the two baseline scenarios. Based on this it was concluded that for future research of similar cases either generic information can be used or a cut-off can be applied. After the assessment, more environmentally favorable was estimated the diesel engine power train because of the large burdens from the battery manufacturing in the battery electric option. Further assessment determined that the diesel engine power train again is less environmentally intensive than the battery electric with the main battery burdens excluded. In the overall life cycle impact assessment both power train showed different results in the different impact categories, which could not place a definitive propulsion option of choice. The conclusions from the analysis are that the diesel engine power train causes higher impact in the categories related to global warming, fossil depletion and in most ecosystems quality indicators. The battery electric version in its base line scenario, on the other hand, expresses higher impact in categories related to human health and in the remaining eco system quality midpoint-scores.

This thesis explores how an Asteroid Sample Return Mission might make use of solar electric propulsion to send a spacecraft on a journey to the asteroid 1989ML and back. It examines different trajectories that can be used to get an asteroid sample return or similar spacecraft to an interplanetary destination and back in the most fuel-efficient manner. While current plans call for keeping such a spacecraft on the asteroid performing science experiments for approximately 90 days, it is prudent to inquire how lengthening or shortening this time period may affect mission fuel requirements. Using optimal control methods, various mission scenarios have been modeled and simulated. The results suggest that the amount of time that the spacecraft may spend on the asteroid surface can be approximated as a linear function of the available fuel mass. Furthermore, It can be shown that as maximum available thrust is decreased, the radial component of the optimal thrust vector becomes more pronounced.

CIVINS / The United States Navy has recognized the rising age of its nuclear reactors. With this increasing age comes increasing importance of backup generators. In addition to the need for decay heat removal common to all (naval and commercial) nuclear reactors, naval vessels with nuclear reactors also require a backup means of propulsion. All underway Navy nuclear reactors are operated with diesel generators as a backup power system, able to provide emergency electric power for reactor decay heat removal as well as enough electric power to supply an emergency propulsion mechanism. While all commercial nuclear reactors are required to incorporate muhiple backup generators, naval submarine nuclear plants feature a single backup generator. The increasing age of naval nuclear reactors, coupled with the dual reqmrements of a submarine's solitary backup generator, makes the study of submarine backup generators vital. / CIVINS / US Navy (USN) author

The mechanical pitching characteristic of the NPS flapping-wing Micro Air Vehicle (MAV) developed by Professor Kevin D. Jones are studied experimentally through the use of constant temperature anemometry and force balance techniques. The MAV without the main fixed-wing is placed in a laminar flow field within a low speed wind tunnel with the wake after the flapping wings characterized with a constant temperature anemometer and thrust generation measured by a load cell at various neutral angles, flapping frequencies and free stream velocities. The experiments seek to determine the effects on the MAV propulsion when the neutral angle of attack of the flapping wings is varied. Flow visualization is also performed to better enhance understanding of the flow field across the pitched flapping wings.