Search

The interest in flying wings dates as far as the early years of the aviation age. Early investigations of the feasibility of the concept demonstrated increased aerodynamic efficiency and reduced fuel consumption. However, structural, engine integration, and stability and control issues prevented further development. In the 1990s, a new concept, the blended wing body (BWB), was created to alleviate some of the concerns of flying wings while maintaining increased efficiency and adding further benefits, such as reduced pollutant and noise emissions. Despite the promise, technical hurdles once again proved to be a deal breaker and, as of 2024, the only successful flying wing is the B-2 Spirit, an extremely complex and expensive aircraft. Nowadays, with the world quickly transitioning towards cleaner energy, the interest in the BWB has been renewed. The latest technological advancements in the aerospace industry should make its development more plausible; however, passenger comfort issues remain. Surprisingly, the BWB development may come from an unexpected application, as a tanker aircraft. As the U.S. Air Force is seeking a replacement to hundreds of aging tankers, a startup company was recently funded to develop the concept and build a prototype. In this study, we explore the history of blended designs from its early days, highlighting its opportunities and challenges—and why the design is an intriguing fit for application as a tanker aircraft. [ABSTRACT FROM AUTHOR]

To protect civilian global positioning system (GPS) users from spoofing attacks, the U.S. Air Force Research Lab has proposed the chips-message robust authentication (Chimera) enhancement for the L1C signal. In particular, the Chimera fast channel allows users to authenticate the received GPS signal once every 1.5 or 6 s, depending on the out-of-band source utilized for receiving the fast channel marker keys. However, for many moving receiver applications, receivers often use much higher GPS measurement rates, at 5-20 Hz. In this work, we derive a stochastic reachability (SR)-based detector to perform continuous GPS signal verification and state estimation between Chimera authentications. Our SR detector validates the received GPS measurement against any self-contained sensor, such as an inertial measurement unit, in the presence of bounded biases in the sensor error distributions. We demonstrate via Monte Carlo simulations that our detector satisfies a user-defined false alarm requirement during nominal conditions, while successfully detecting a simulated spoofing attack. We further demonstrate that our SR state estimation filter successfully bounds the true state during both authentic and spoofed conditions. [ABSTRACT FROM AUTHOR]

Adhesively bonded doublers and adhesively bonded repairs are extensively used to extend the operational life of metallic aircraft structures. Consequently, this paper focuses on the tools needed to address sustainment issues associated with both adhesively bonded doublers and adhesively bonded repairs to (metallic) aircraft structures, in a fashion that is consistent with the building-block approach mandated in the United States Air Force (USAF) airworthiness certification standard MIL-STD-1530D and also in the United States (US) Joint Services Structural Guidelines JSSG-2006. In this context, it is shown that the effect of biaxial loads on cohesive crack growth in a bonded doubler under both constant amplitude fatigue loads and operational flight loads can be significant. It is also suggested that as a result, for uniaxial tests to replicate the cohesive crack growth seen in adhesively bonded doublers and adhesively bonded repairs under operational flight loads, the magnitude of the applied load spectrum may need to be continuously modified so as to ensure that the crack tip similitude parameter in the laboratory tests reflects that seen in the full-scale aircraft. [ABSTRACT FROM AUTHOR]

After the end of World War II, many military air bases in Greenland were abandoned with all the material left in place. One of these sites was the Bluie East Two military air base. A specific feature of this area is that it contained thousands of old barrels formerly used for fuel storage. In 2019, a rehabilitation of this area began. A few months prior to the rehabilitation, our expedition visited the area and mapped it using an unmanned aerial vehicle (UAV). This made it probably the latest documentation before the start of the sanitation. The aim of such mapping was to estimate the number of barrels in a given location. The second objective was to monitor the progress of the rehabilitation over the years. For this purpose, satellite data were acquired for the years 2019 through 2022. A supervised classification was performed to automatically detect sites with barrel occurrences, which enabled subsequent change detection. We conclude that a total of 33,786 old barrels were located in the investigated area in 2019. However, we suggest this number is a lower estimate of the actual number of barrels due to the factors we mention in our paper. The results further indicate that between the years 2019 and 2022 the barrels were removed from more than half of the area. [ABSTRACT FROM AUTHOR]

In their recently published letter to the editor, (1) Olsen et al. commented on the epidemiological study by Purdue et al. (2) and the accompanying 'Invited Perspective' by Steenland. (3) [...]

This article analyzes the possible consequences of the F-35 fighter crisis between the U.S. and Turkiye, particularly in terms of its effect on the tactical nuclear weapons (TNWs) now deployed in Turkiye as part of NATO's nuclear sharing program. It argues that the U.S. should respond to Ankara's demands by either allowing Turkiye to rejoin the F-35 fighter project or by selling new F-16 fighters and modernization kits to Turkiye that will permit its continued deployment of TNWs. This move would, in turn, prevent the 'brain death' of the alliance; otherwise, negative attitudes emanating from the U.S. may lead Turkiye to search for alternative suppliers, a move that could include buying fighter aircraft from Russia or China and might lead Turkiye to question its membership in NATO. Anything that causes Turkiye to do this is a problem in the current security environment since competition between NATO and Russia has reached dangerous levels with the Russian invasion of Ukraine under the shadow of the threat of the use of nuclear weapons. Keywords: F-35, Tactical Nuclear Weapons, Nuclear Sharing, Dual Capability Aircraft (DCA), Nuclear Assurance, Introduction Europeans have often been suspicious of American intentions, but nuclear weapons have long been one of the most important tools, and perhaps the most important one, by which the [...]

In late 1950s, designers of intercontinental ballistic missile launch facilities had to juggle hardening the facilities against nuclear weapon blast effects while maximizing reaction time and rapid force expenditure without [...]

When in early August 1990 the U.S. Air Force was called upon to deploy personnel, aircraft and equipment to the Gulf Region to persuade Iraq's Saddam Hussein to give up [...]

Lompoc yerba santa Eriodictyon capitatum (Namaceae) is an evergreen shrub endemic to west Santa Barbara County in coastal southern Calif. The species was listed as rare under the Calif. Endangered Species Act in 1979 and as endangered under the U.S. Endangered Species Act in 2000. At Federal listing in 2000, Lompoc yerba santa was known from four locations (five occurrences) in three geographic areas. In 2022, the species is known from 11 occurrences in four geographic populations of which 10 occurrences are considered extant and 1 occurrence likely extirpated: Orcutt Oil Field in the Solomon Hills, 2 occurrences; Burton Mesa on Vandenberg Space Force Base North, 6 occurrences; La Salle Canyon on Vandenberg Space Force Base South, 1 occurrence; and Santa Ynez Mountains, 2 occurrences. Lompoc yerba santa occurs mostly in chaparral and bishop pine (Pinus muricata) forest, and most occurrences are in sandy soil. The species stands up to 5 m tall and with vertical stems up to 10 cm diameter. Much of its reproduction appears to be vegetative by rhizome production, suggesting low dispersal ability, and it is a habitat specialist with apparent dependence on substrate disturbance and fire. Using all available information and international standards with a precautionary but realistic attitude to uncertainty, Lompoc yerba santa in 2022 meets IUCN criteria for endangered status: the small extent of occurrence is 433 [km.sup.2] (, Lompoc yerba santa Eriodictyon capitatum (Namaceae; Luebert et al. 2016; Fig. 1) is an evergreen shrub endemic to west Santa Barbara County in coastal southern Calif. (Fig. 2). The species [...]

Differentiating performance components across military occupations is critical to developing assessments and other applications for matching people to occupations in the military. However, identifying occupation-specific performance components is challenging and resource intensive. The current paper summarizes different methods the services use to define and identify occupation-specific performance components. The paper concludes with recommendations and future directions for advancing the military's needs for information and data on occupation-specific performance components. [ABSTRACT FROM AUTHOR]