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What if the aviation industry contributed no carbon emissions?
Published in Nawal K. Taneja, Airimagination, 2023
Finally, while some airlines are thinking about the use of electric aircraft, some are also thinking about the use of supersonic aircraft. Leaving aside the question of the financial viability of a supersonic aircraft, there is also the question of its carbon footprint. Boom Technology claims that its supersonic aircraft, Overture, can achieve net-zero carbon emissions and should be able to operate on 100% sustainable fuel. United has ordered 15 with options to purchase another 35. Since supersonic aircraft are expected to fly at much higher altitudes than subsonic aircraft (e.g., at about 60,000 ft compared to about 35,000 ft), there is some concern about the level of emissions generated. Although at higher altitudes the air is thinner, producing less resistance, emissions generated from the supersonic aircraft, flying at higher altitudes, could also be higher than from the subsonic aircraft flying at lower altitudes. Nevertheless, imagine, if these supersonic aircraft took a significant percentage of business passengers out of corporate jets.
Introduction
Published in Doramas Jorge-Calderón, Aviation Investment, 2020
Besides the three fundamental reasons to invest in transport – including time and cost savings and safety improvements, as mentioned above – investment appraisal analysts are continuously confronted with myriad other reasons put forward to justify investments. Some of these reasons are ultimately invalid, but come mixed with elements of the three valid reasons set out above, making it hard to distil the extent to which an investment creates value, and the extent to which it constitutes waste and abuse. Arguments put forward may include the following:This investment will open up our region and lead to new economic activity and industry. This is a valid rationale insofar as it is reflected in the three fundamental reasons. Unfortunately, it tends to open the gates to all sorts of claims to benefits that are in fact mostly invalid. Examples of the resulting waste include newly built airports that remain virtually empty after opening and which end up constituting a sink of regional resources, the exact opposite of the original intention.This is the latest technology. The fact that a project introduces the latest technology does not make it necessarily a good investment. There may be a case for keeping the technology alive, but that does not imply its deployment. An example was the Concorde supersonic aircraft.And this technology will improve safety. In aviation, the safety argument has been used over the years all too often as an excuse to preserve market power (with the accompanying economic rents) and to justify transfers. Safety does not justify any expenditure, regardless of the cost. Expenditure on safety has to be set against the value of the expected safety improvement, and investments argued for on safety grounds in circumstances where operations already meet international safety standards tend to have other motivations.It will create jobs and the multiplier effect will generate more economic activity in the area. Many of the jobs ‘created’ may be crowded out from other activities. Moreover, loss-making investments also ‘create’ jobs and unleash multiplier effects. Contrary to frequent popular discourse, jobs and multipliers are not in themselves a sound reason to invest.We will bring more tourists. Whether this is a good reason or not will depend on the cost of bringing those tourists, and the added benefits the tourists generate.We need to increase market share. Many businesses have gone bust making wasteful investments in their chase for market share rather than profit. The history of the airline industry is full of examples of defunct airlines that had expanded too fast in the quest for market share.
The thermal-mechanical buckling and postbuckling design of composite laminated plate using a ROM-driven optimization method
Published in Mechanics of Advanced Materials and Structures, 2023
Ke Liang, Zheng Li, Zhenghu Wang, Yongjie Zhang
Composite laminated plates are commonly used as primary load-carrying components of aerospace structures subjected to high temperature environments, such as the outer skin of supersonic aircraft and space-to-earth vehicle [1, 2]. These structures are prone to have an “earlier buckling” compared to the purely mechanical loading case, due to the thermally induced compressive stresses in constrained structures [3–6]. In this case, the load-carrying capability of composite laminated plates is mainly governed by their buckling loads, and further weight savings can be achieved when the plates are allowed to continuously loaded into the postbuckling stage [7]. Therefore, it is desirable to enhance the buckling and postbuckling performance of laminated plates in a thermal-mechanical environment through design optimization of ply stacking sequences.
Laminar-to-turbulent transition in supersonic boundary layer: Effects of initial perturbation and wall heat transfer
Published in Numerical Heat Transfer, Part A: Applications, 2018
S. Sharma, M. S. Shadloo, A. Hadjadj
Since the advent of supersonic era of aviation, the understanding of boundary layer flow stability along with attaining the in-depth knowledge of transition of supersonic boundary layer (SBL) flows to turbulence has become vital. The knowledge of high-speed boundary layer flows poses fundamental challenges in fluid dynamics community and is equally important to be investigated at the same time. In high-speed applications like for supersonic aircraft and spacecraft, the temperature of the wall [1] becomes an important parameter to be incorporated in the study. The wall temperature of a speeding aircraft is significantly lower than the adiabatic temperature of the wall, but on the other hand in case of atmospheric reentry of a spacecraft, due to the friction of the atmosphere, the wall temperature becomes way too higher than the adiabatic wall temperature. The high temperature of the exhaust gases over the blade of a gas turbine [2] or the wall of any propulsive nozzle [3] also mimic the heated wall scenario. For a spacecraft, the initial laminar flow could be tripped to turbulence because of the surface roughness and turbulence intensity [4]. Therefore, acquiring the physical insight of the transition of the flow from laminar to turbulent state becomes an absolute necessity.
Sound shielding simulation by coupled discontinuous Galerkin and fast boundary element methods
Published in Engineering Applications of Computational Fluid Mechanics, 2022
S. Proskurov, R. Ewert, M. Lummer, M. Mößner, J. W. Delfs
The noise prediction technique described in this work has been developed with the objective to quickly evaluate new design concepts. The future work would involve application of the coupled method for simulating fan-tone shielding for a full-scale supersonic aircraft. It can be challenging to optimise a supersonic nacelle for take-off and approach subsonic phase. Currently, the method is limited to predictions in a free-stream flow of up to M ≈ 0.3 in the FM-BEM domain. This limitation comes from a low Mach number assumption used in the formulation of the BEM equations. It appears that there are no simple ways to overcome this restriction, also, bearing in mind that the FMM feature is very desirable and has to be retained for efficacy when solving engineering problems.