Aviation emissions have an impact on the global climate, and this is consequently an active area of research worldwide. By adapting replicable and transparent systematic review methods from the field of evidence-based medicine, we aim to synthesise available data on the effects of aviation emissions on climate. From these data, we aim to calculate lower and upper bounds for estimates of the effect of aviation on climate in an objective manner.

For the systematic review an appropriate protocol was developed and applied by two independent reviewers, to identify research that met the inclusion criteria. These included all aviation types, original research studies, climate models with aviation as a specific component, with outcomes for emissions, radiative forcing, global warming potential and/or surface temperature changes. These studies were prioritised and data extracted using a standard process. The 35 studies reviewed here reported radiative forcing, global warming potential and/or temperature changes as outcomes, allowing direct comparisons to be made.

Tabulated results and a narrative commentary were provided for overall effects on climate, and the individual effects of carbon dioxide, water, contrails, cirrus clouds, ozone, nitrogen oxides, methane, soot and sulphur oxides. Lower and upper bounds for these effects, and their relative contributions compared to overall radiative forcing and surface temperature changes, have been described.

This review shows that the most recent estimates for the contribution of aviation to global climate are highly dependent on the level of scientific understanding and modelling, and predicted scenarios for social and economic growth. Estimates for the future contribution of aviation to global radiative forcing in 2015 range from 5·31% to 8·04%. For 2050 the estimates have a wider spread, from 2·12% to 17·33%, the latter being for the most extreme technology and growth scenario. These global estimates should be considered within the context of uncertainties in accounting for the direct and indirect effects of different contributions. Variations between lower and upper bounds for estimates of radiative forcing are relatively low for carbon dioxide, around 131% to 800% for cirrus clouds effects, and 1,044% for soot. Advances in climate research, particularly in the area of contrail and cloud effects, has led to some revision of the 1999 IPCC estimates(1), and demonstrates that the research community is actively working to further understand the underlying science.

The approaches assumptions, limitations and future work were discussed in detail. We have demonstrated how the systematic review methodology can be applied to climate science, in a replicable and transparent manner.

Space transportation remains in the pioneering stages. What might this century bring if we had a ‘railroad to space’ that embodied the characteristics of the transcontinental undertaking? The X-33 and Venture Star projects were one attempt to achieve the characteristics of that transcontinental railroad. There are others, here and in other countries, but perhaps we need to begin with a smaller first step, a small, commercial reusable rocket with ballistic ascent to space altitude with a hypersonic glider return? Our challenge in space today is to develop vehicles that are in continuous use, maintained and operated on a fixed schedule despite weather or environmental hazards, which move payloads not only into space but back again. The X PRIZE was a $10 million prize awarded to Scaled Composites as the first privately financed spaceship that launched the equivalent of three persons to an altitude of at least 100 kilometers on two consecutive flights within two weeks. What about an analogous vehicle that flies two or three times a week, every week for a number of years? A major difference is that this challenge is to be accomplished without government support or government developed vehicles. The aerospace vehicle design (AVD) Laboratory team at the University of Texas at Arlington is developing a generic space access vehicle (SAV) design synthesis environment with focus on the conceptual design phase. The AVD Lab has applied elements of this toolbox to the study of a tourist aerospace vehicle under a grant from Rocketplane Limited, Inc. The development of a low-cost tourist vehicle based on the adaptation of a Learjet 25/35/45 series aircraft is the focus of this paper.

An experimental investigation was carried out to find the effect of an annular co-flow jet on the primary supersonic jet from Mach 2 nozzle at different levels of overexpansion. In this study, a convergent-divergent circular nozzle of exit Mach number 2, surrounded by an annular convergent circular nozzle with an annular gap of 4·4mm was used. Nozzle pressure ratios (NPRs) 3, 4, 5, 6, 7 are investigated for overexpanded states of the primary jet and NPR 8 is investigated for almost correctly expanded state. The centreline pressure distributions were taken at all NPRs for both with and without co-flow case, to investigate the supersonic core extent and mixing activity in the jet field. In the radial direction pitot pressure at different axial locations at all NPRs for both the cases are measured to find the jet development and shadowgraph visualisation of jet structure was done to visualise the shock structure in near-field. It is found that the co-flow acts as mixing inhibitor at all levels of overexpansion for Mach 2 nozzle.

Inlet unstart boundary is one of the most important issues of the hypersonic inlet and is also the foundation of the protection control of a scramjet. To solve this problem, the 2D internal steady flow of a 2D mixed internal/external compression hypersonic inlet was numerically simulated at different freestream conditions and backpressures with a RANS (Reynolds-Averaged Navier-Stokes) solver using a RNG (Renormalisation Group) k-ε turbulence model, and two different inlet unstart phenomena were analysed. The dimensional analysis method was introduced to find the essence variables describing the inlet unstart boundary based on “numerical experimental” data in this paper. The dimensionless pressure ratios of the forebody and isolator were analysed respectively. The results show that the unstart boundary of the 2D mixed hypersonic inlet is determined by M0, α and Re0. Pressure ratio π increases with M0 increasing, and it increases firstly and decreases then with α increasing. Pressure ratio π increases with Re0 increasing. Re0 (Re0 < 2 × 107) has a major effect on π and Re0 (Re0 > 2×107) has little effect on π.

Dual-mode scramjet is one of the candidates for hypersonic flight propulsion system which will be used in wide range of flight Mach numbers from 4 to 12 or higher, wherein dual-mode scramjet should be well designed to be suitable for subsonic/supersonic combustion operation according to the flight conditions. Therefore this system is required to operate in a finite number of operational modes that necessitate robust, stable, and smooth transitions between them by which selective operability of supersonic/subsonic combustion modes and efficient combustor operation in these modes may be realised. A key issue in making mode transition efficient and stable is mode transition control. The major problem in mode transition control is the handling of the various flow and combustion coupling effects of dual-mode scramjet whose physical states are spatially coupled and whose governing equations are partial differential equations. Involving these distributed parameter issues, our basic idea is using the shape control theory to study the control problems of mode transition for dual-mode scramjet with the aim of achieving the desirable design properties and increasing control reliabilities. This specific approach is motivated by the promise of novel techniques in control theory developed in recent years. Concrete control arithmetic of this approach, such as shape control model, sensitivity analysis and gradient-based optimisation procedure, are given in this paper. Simulation results for an axisymmetric, wall-injection dual-mode scramjet show the feasibility and validity of the method.