Engineered solutions are becoming more complex and multi‐disciplinary in nature. This evolution requires new techniques to enhance design and analysis tasks that incorporate data integration and interoperability across various engineering tool suites spanning multiple domains at different abstraction levels. Semantic web technologies (SWT) offer data integration and interoperability benefits as well as other opportunities to enhance reasoning across knowledge represented in multiple disparate models. This paper introduces the digital engineering framework for integration and interoperability (DEFII) for incorporating SWT into engineering design and analysis tasks. The framework includes three notional interfaces for interacting with ontology‐aligned data. It also introduces a novel model interface specification diagram (MISD) that provides a tool‐agnostic model representation enabled by SWT that exposes data stored for use by external users through standards‐based interfaces. Use of the framework results in a tool‐agnostic authoritative source of truth spanning the entire project, system, or mission.

This article discusses ongoing research investigating the feasibility of supporting an interoperability and integration framework to enable the digital thread, or an authoritative source of truth with current technology. The question that initiated this exploratory research was, “Is there current technology that can enable cross-domain digital artifact data sharing needed for the digital thread?” A thorough review and investigation of current state-of-the-art model-based systems engineering was performed by reviewing literature and performing multiple site visits and interviews with organizations at the forefront of digital engineering. After this initial investigation and review, a Semantic Web-enabled framework that would allow data in the thread to be captured, stored, transferred, checked for completeness and consistency, and changed under revision change control management began to be formed. This framework has gone through revisions. This paper reflects the most current demonstration of the framework and its capability of acquiring digital data, and parsing and querying the data using Semantic Web technology to generate a decision table that allows the decision data to be visualized. The article concludes with future demonstrations of the framework to further advance toward a framework that can enable a digital thread in practice.

Modern underwater vehicles typically operate under the influence of autopilots or control systems. The hydrodynamic design of these vehicles is often undertaken without consideration of how the control system will change the dynamical characteristics of the vehicle. In a mathematical model for the dynamics of an underwater vehicle that also incorporates the control system, the parameters of the control system appear to modify the hydrodynamic coefficients. If the effect of the control system is understood to change the hydrodynamic characteristics of a vehicle, it suggests a certain futility to a hydrodynamic design effort aimed at achieving specific characteristics if those efforts are going to be undone by a few numbers in software. This paper illustrates this idea by considering the question of what makes an underwater vehicle stable. The examples illustrate that the effect of control on the mathematical model of an underwater vehicle is indistinguishable from hydrodynamic effects, and perhaps more significant. This idea is generalized to showthat it is possible for feedback to entirely cancel and replace the hydrodynamic effects in a mathematical model. This calls into question the relevance of stability metrics based on hydrodynamic coefficients when the underwater vehicle incorporates an autopilot. The paper introduces several design metrics that can only be affected by hydrodynamic design. The conclusions suggest an approach to achieving specified maneuvering characteristics for automated underwater vehicles by determining the set of hydrodynamic parameters that yield the desired results, and then evaluating how best to obtain those parameters using both hydrodynamics and software. The conclusions also question the validity of hydrodynamic experiments intended to understand submerged vehicle operations when they are performed without including the potential effect of a control system. The paper considers how the ideas presented might extend to the study of stability in fish.

This paper presents an explanation of why a spinning football rotates so that the spin axis remains nearly aligned with the velocity vector, and approximately parallel to the tangent to the trajectory. The paper derives the values of the characteristic frequencies associated with the football’s precession and nutation. The paper presents a graphical way of visualizing how the motions associated with these frequencies result in the observed “wobble” of the football. A solution for the linearized dynamics shows that there is a minimum amount of spin required for the motion to be stable and for the football not to tumble. This paper notes the similarity of this problem to that of spun projectiles. The results show that the tendency of a football to align itself with and rotate with the velocity vector is associated with an equilibrium condition with a non-zero aerodynamic torque. The torque is precisely the value required for the football to rotate at the same angular rate as the velocity vector. An implication of this is that a release with the football spin axis and velocity vector aligned (zero aerodynamic torque) is not the condition that results in minimum motion after release. Minimum “wobble” occurs when the ball is released with its symmetry axis slightly to the right or left of the velocity vector, depending on the direction of the spin. There are additional forces and moments acting on the football that affect its trajectory and its stability, but it is not necessary to consider these to explain the tendency of the ball to align with the velocity vector and to ”wobble.” The results of this paper are equally applicable to the spiral pass in American football and the screw kick in rugby.