A Comparison of Laser and Microwave Approaches to CW Beamed Energy Launch

One approach to beamed energy propulsion uses a solid heat exchanger to absorb energy from a distant source and transfer it to a working fluid. Systems of this type can be designed using either microwave or laser sources. In general, microwave sources have been expected to be less expensive than lasers for a given power, but to be more limited in range and/or energy density. With the development of high power millimeter-wave sources and low-cost diode laser arrays, both assumptions are open to question. In this paper, we compare current and projected microwave and laser source technologies for a 100-kilogram-class ground-to-orbit launch system and identify key issues affecting the system-level trade between the two approaches

Feasibility and Performance of the Microwave Thermal Rocket Launcher

Beamed-energy launch concepts employing a microwave thermal thruster are feasible in principle, and microwave sources of sufficient power to launch tons into LEO already exist. Microwave thermal thrusters operate on an analogous principle to nuclear thermal thrusters, which have experimentally demonstrated specific impulses exceeding 850 seconds. Assuming such performance, simple application of the rocket equation suggests that payload fractions of 10% are possible for a single stage to orbit (SSTO) microwave thermal rocket. We present an SSTO concept employing a scaled X-33 aeroshell. The flat aeroshell underside is covered by a thin-layer microwave absorbent heat-exchanger that forms part of the thruster. During ascent, the heat-exchanger faces the microwave beam. A simple ascent trajectory analysis incorporating X-33 aerodynamic data predicts a 10% payload fraction for a 1 ton craft of this type. In contrast, the Saturn V had 3 non-reusable stages and achieved a payload fraction of 4%

Air traffic control by distributed management in a MLS environment

The microwave landing system (MLS) is a technically feasible means for increasing runway capacity since it could support curved approaches to a short final. The shorter the final segment of the approach, the wider the variety of speed mixes possible so that theoretically, capacity would ultimately be limited by runway occupance time only. An experiment contrasted air traffic control in a MLS environment under a centralized form of management and under distributed management which was supported by a traffic situation display in each of the 3 piloted simulators. Objective flight data, verbal communication and subjective responses were recorded on 18 trial runs lasting about 20 minutes each. The results were in general agreement with previous distributed management research. In particular, distributed management permitted a smaller spread of intercrossing times and both pilots and controllers perceived distributed management as the more 'ideal' system in this task. It is concluded from this and previous research that distributed management offers a viable alternative to centralized management with definite potential for dealing with dense traffic in a safe, orderly and expeditious manner

The Microwave Thermal Thruster Concept

The microwave thermal thruster heats propellant via a heat-exchanger then expands it through a rocket nozzle to produce thrust. The heat-exchanger is simply a microwave-absorbent structure through which propellant flows in small channels. Nuclear thermal thrusters are based on an analogous principle, using neutrons rather than microwaves, and have experimentally demonstrated specific impulses exceeding 850 seconds. A microwave equivalent will likely have a similar specific impulse, since both nuclear and microwave thermal thrusters are ultimately constrained by material thermal limits, rather than the energy-density limits of chemical propellants. We present the microwave thermal thruster concept by characterizing a novel variation for beamed-energy launch. In reducing the thruster concept to practice, the enabling physical process is microwave absorption by refractory materials, and we examine semiconductor and susceptor-based approaches to achieving this absorption within the heat-exchanger structure

Calibration of Multicurrency LIBOR Market Models

This paper presents a methodf or calibrating a multi currency lognormal LIBOR Market Model to market data of at-the-money caps, swaptions and FX options. By exploiting the fact that multivariate normal distributions are invariant under orthonormal transformations, the calibration problem is decomposed into manageable stages, while maintaining the ability to achieve realistic correlation structures between all modelled market variables.currency options; LIBOR market model; exchange rate risk; interest rate risk

Acute phase protein levels in dogs with mast cell tumours and sarcomas

<p><b>Context:</b> The acute phase protein response is part of a non-specific and complex host response to inflammation. It occurs shortly after tissue injury and may be induced by a range of different causes, including infectious, inflammatory, neoplastic, traumatic or immunological disease. Although it was conventionally believed that APPs were exclusively hepatocyte derived, there is increasing evidence to support extra-hepatic generation in neoplastic and other disease states. In people, C-reactive protein (CRP) has been shown to be of value in identifying metastatic disease from primary renal tumours as well as showing promise for monitoring rejection of renal transplants. Serum CRP correlates with survival in colorectal cancer and oesophageal squamous cell carcinoma while serum amyloid A (SAA) concentrations correlate with cancer activity, stage and prognosis in gastric tumours. Recent immunohistochemical studies in people with oesophageal carcinoma suggest that tumour tissue may itself elaborate APP with a poorer survival and outcome associated with tumours elaborating higher levels of CRP. A similar association has been seen between alpha-1 acid glycoprotein (AGP) and colorectal tumours and ovarian carcinoma.</p> <p>As yet, studies regarding APP values in neoplastic conditions in dogs are limited, and many are non-specific. In veterinary patients, elevated levels of AGP have been identified in dogs with a range of tumours with localisation to liver and splenic tissue in one study. Another study found higher levels of AGP in dogs with non-specific tumours of grade III-IV based on the WHO Tumour Node Metastasis (TNM) scale and elevated serum AGP has been documented in non-specific tumour-bearing cats. Elevated CRP levels have been documented in both dogs and cats with lymphoma and serum CRP may be used as an indicator of complete remission status in dogs with multicentric lymphoma. Elevated levels of CRP, Haptoglobin (Hp) and SAA have been identified in dogs with mammary tumours, with significant increases over normal in the presence of metastatic disease, primary tumours greater than 5cm in diameter and those with ulceration.</p> <p>In this study we evaluated an APP profile using four APPs (CRP, Hp, SAA and AGP), in dogs with mast cell tumours (MCTs) and sarcomas to assess whether the APP profile would change in reflection of tumour presence; whether the extent of any change would correlate with tumour grade; and whether the changes would differ with tumour type.</p> <p><b>Approach:</b> Patients with naturally occurring MCTs and sarcomas presenting for staging and treatment were included if they met the study criteria. Criteria for inclusion were that the patient was not currently being treated with steroids, did not have a recent history of infectious or inflammatory disease other than the tumour, a definitive histological diagnosis was available and a full staging procedure was completed prior to surgery using standard oncological protocols to identify metastatic disease where present. Following surgical resection each tumour was submitted for full histological evaluation and grading to include assessment of the margins of excision. Cases were only enrolled in the study if blood sampling formed part of the clinical investigation and/or treatment, and where residual blood was available after diagnostic sampling which would otherwise have been disposed of as clinical waste. In brief, the CRP levels were determined by immunoturbidometric assay and Hp by means of haemoglobin binding capacity assay. SAA was measured with a commercial canine ELISA kit (TriDelta Development, Dublin, Ireland) and AGP was measured with a commercial radial immunodiffusion assay (J-Path Inc, Tokyo, Japan).</p> <p><b>Results:</b> All comparisons using continuous data were checked for normality and equality of variances and appropriate statistical tests were employed (student’s t test operationalised as a two-sample Welch’s test for samples of unequal sizes and variances, Mann-Whitney, Chi-square and Fishers exact tests as appropriate). In MCTs, the CRP and AGP were elevated above reference ranges, Hp showed no significant change and SAA dropped relative to the reference range. In sarcoma patients CRP, Hp and AGP were all elevated above reference ranges. None of the tumour grade differences were significant apart from SAA in sarcoma patients where values in grade 2 sarcoma were significantly higher than those in grade 1.</p> <p><b>Interpretation and notes of caution:</b> The numbers in our groups were small which compromises the validity of statistical evaluation so our results must be interpreted with caution. However some interesting relationships have emerged from the initial evaluation which suggests that APP profiles may have potential for screening in patients with neoplastic disease. For patients with MCTs, CRP and AGP levels would be expected to increase, with a concurrent drop in SAA levels. In sarcoma patients CRP, AGP and Hp can all be expected to increase. These initial results need to be evaluated in larger numbers of cases with naturally occurring disease to validate the findings, to assess whether the presence and extent of metastatic disease has a significant effect, and also to confirm whether the values alter after surgical resection of the primary tumour.</p> <p><b>Significance of findings:</b> If there are consistent and specific changes in APP profiles associated with different tumour types in dogs, as is the case with a wide range of cancers in humans, then there may be potential for APP profiles on routine blood samples to be used as indicators of disease, or where monitoring for recurrence. Whether they could also have potential for assessment of the presence of metastatic disease and prognosis as in people is unknown as yet.</p&gt