Lunar lander conceptual design

This paper is a first look at the problems of building a lunar lander to support a small lunar surface base. A series of trade studies was performed to define the lander. The initial trades concerned choosing number of stages, payload mass, parking orbit altitude, and propellant type. Other important trades and issues included plane change capability, propellant loading and maintenance location, and reusability considerations. Given a rough baseline, the systems were then reviewed. A conceptual design was then produced. The process was carried through only one iteration. Many more iterations are needed. A transportation system using reusable, aerobraked orbital transfer vehicles (OTV's) is assumed. These OTV's are assumed to be based and maintained at a low Earth orbit (LEO) space station, optimized for transportation functions. Single- and two-stage OTV stacks are considered. The OTV's make the translunar injection (TLI), lunar orbit insertion (LOI), and trans-Earth injection (TEI) burns, as well as midcourse and perigee raise maneuvers

A case for the economics of secure software development

Over the past 15 years the topic of information security economics has grown to become a large and diverse field, influencing security thinking on issues as diverse as bitcoin markets and cybersecurity insurance. An aspect yet to receive much attention in this respect is that of secure software development, or 'SWSec' - another area that has seen a surge of research since 2000. SWSec provides paradigms, practices and procedures that offer some promise to address current security problems, yet those solutions face financial and technical barriers that necessitate a more thorough approach to planning and execution. Meanwhile, information security economics has developed theory and practice to support a particular world-view; however, it has yet to account for the investments, constructs and benefits of SWSec. As the frequency and severity of computer misuse has increased, both areas have struggled to impart a new mindset for addressing the inherent issues that arise in a diverse, connected and functionality-driven landscape. This paper presents a call for the establishment of an economics of secure software development. We present the primary challenges facing practice, citing relevant literature from both communities to illustrate where commonalities lie - and where further work is needed. Those challenges are decomposed into a research agenda, deriving from the application of principles in both themes a lack of models, representation and analysis in practice. A framework emerges that facilitates discussions of security theory and practice

Stability and Control Investigations in Early Stages of Aircraft Design

This paper provides an overview of current activities of DLR (German Aerospace Center) with respect to stability and control investigations in the context of early stages of aircraft design. For this purpose, DLR follows an interdisciplinary and multi-level design approach. Using an integration framework in combination with a central data exchange format, largely automated process chains are set up that combine calculation and simulation capabilities of the multitude of disciplines required in early aircraft design. Rather than using empirical relations and assumptions based on experience, the underlying methods applied by the tools are mainly based on physical model representations. The major aim of this design approach is to generate all relevant data needed for stability and control investigations, including aerodynamic damping derivatives and to assemble them within a flight dynamics model. Not only does this approach allow for an early consideration of stability and control characteristics, but it also respects interdisciplinary effects and enables automated design changes. This paper describes the infrastructure used for setting up the described process. It presents disciplinary tools used to calculate engine performance maps, calculate aerodynamic performance maps and structural properties, generate flight dynamics models with associated control laws and to assess aircraft handling qualities. Furthermore, this paper provides application examples of early stability and control considerations, using integrated interdisciplinary process chains. This comprises a handling qualities assessment under uncertainty considerations and vertical tailplane sizing for a blended wing body. In addition, engine and split flap sizing processes for an unmanned combat aerial vehicle are shown. The interdisciplinary design approach presented here, serves to find a well justified early configuration and reduces the risk of later design changes