Trailing-edge scalloping effect on flat-plate membrane wing performance

This investigation studies the effect of trailing-edge scalloping on the lift and drag force coefficients of flat, membrane wings that vibrate at low Reynolds numbers (<61,000). A series of rigid, flat plate frames with moderate aspect ratio and repeating membrane cell structure were studied and compared to a rigid plate and a rigid scalloped plate. Lift and drag measurements were acquired using an external force-balance; flow fluctuation measurements were captured with a hot-wire. Results showed that the size and aspect ratio of the latex cell had a greater impact on lift than scalloping and that scalloping had a greater effect on drag than the cell aspect ratio. Compared to the solid wings, the membrane wings exhibited higher lift and drag coefficients, likely due to both effective cambering and dynamic interaction with the free shear layer. While trailing-edge scalloping decreased both the lift and drag coefficients relative to no scalloping, the greater effect was on drag, thus, increasing aerodynamic efficiency. The maximum lift-to-drag ratio was attained for a 25% scallop with a repeating cell aspect ratio of one. A unique nondimensional scaling of the membrane vibration peak frequency is also presented.     

History of UK contribution to astronautics: Politics and government

In all developed countries, once it emerged from the amateur era, Space (and especially rocketry) moved on the public agenda because of its potential significance for both the civil and military policies of governments (coupled with its appetite for new money). In the UK the policy treatment of Space broadly paralleled that in other countries until the post-Empire trauma, the burn-out of the White-Hot Technological revolution of Harold Wilson, and the financial crises of the 1970s exhausted the public appetite for large scale publicly funded projects in high technology. The culmination for Space of these pressures came in 1986–1987 when the UK rejected the emerging international consensus and, almost alone, stayed outside the manned space commitments which developed into the International Space Station. In this paper, Colin Hicks will review the UK political developments which led up to the 1986–1987 decision and how the politics and organisation of UK space activity have developed since then to the point where in 2008 a major government review of the UK involvement in manned space was commissioned.     

Physical protection systems cost and performance analysis: a casestudy

Design and analysis of physical protection systems requires: (1) identification of mission critical assets; (2) identification of potential threats that might undermine mission capability; (3) identification of the consequences of loss of mission-critical assets (e.g., time and cost to recover required capability and impact on operational readiness); and (4) analysis of the effectiveness of physical protection elements. CPA-Cost and Performance Analysis-addresses the fourth of these four issues. CPA is a methodology that joins activity based cost estimation with performance-based analysis of physical protection systems. CPA offers system managers an approach that supports both tactical decision making and strategic planning. Current exploratory applications of the CPA methodology address analysis of alternative conceptual designs. Hypothetical data is used to illustrate this process     

Managing change through roadmapping [changes in aviation electronics]

Presently the USAF is operating with 90 different Model Design Series (MDS) aircraft. The 90 MDS aircraft make up a total of 5778 airframes, each with a different number of Line Replaceable Units (LRUs) which make up the avionics systems. Some of the MDSs have as few as 53 avionics LRUs while others as many as 495. The total dollar value of the USAF aircraft avionics LRUs is approximately $42.4B and $30.68B in spares. Depot repairable cost to maintain these components each year is approximately $1.2B. Each MDS is assigned specific missions and the avionics systems are developed to support those missions. Due to the evolution of mission types and user needs, change is constant for the avionics manager.     

Oxygen Isotopes and Sampling of the Solar System

The atmospheres of the four giant planets of our Solar System share a common and well-observed characteristic: they each display patterns of planetary banding, with regions of different temperatures, composition, aerosol properties and dynamics separated by strong meridional and vertical gradients in the zonal (i.e., east-west) winds. Remote sensing observations, from both visiting spacecraft and Earth-based astronomical facilities, have revealed the significant variation in environmental conditions from one band to the next. On Jupiter, the reflective white bands of low temperatures, elevated aerosol opacities, and enhancements of quasi-conserved chemical tracers are referred to as ‘zones.’ Conversely, the darker bands of warmer temperatures, depleted aerosols, and reductions of chemical tracers are known as ‘belts.’ On Saturn, we define cyclonic belts and anticyclonic zones via their temperature and wind characteristics, although their relation to Saturn’s albedo is not as clear as on Jupiter. On distant Uranus and Neptune, the exact relationships between the banded albedo contrasts and the environmental properties is a topic of active study. This review is an attempt to reconcile the observed properties of belts and zones with (i) the meridional overturning inferred from the convergence of eddy angular momentum into the eastward zonal jets at the cloud level on Jupiter and Saturn and the prevalence of moist convective activity in belts; and (ii) the opposing meridional motions inferred from the upper tropospheric temperature structure, which implies decay and dissipation of the zonal jets with altitude above the clouds. These two scenarios suggest meridional circulations in opposing directions, the former suggesting upwelling in belts, the latter suggesting upwelling in zones. Numerical simulations successfully reproduce the former, whereas there is a wealth of observational evidence in support of the latter. This presents an unresolved paradox for our current understanding of the banded structure of giant planet atmospheres, that could be addressed via a multi-tiered vertical structure of “stacked circulation cells,” with a natural transition from zonal jet pumping to dissipation as we move from the convectively-unstable mid-troposphere into the stably-stratified upper troposphere.