Mission and System Design

Vasile, Massimiliano; Kemble, Stephen; Santovincenzo, A.; Taylor, M.

doi:10.1007/978-3-642-41101-4_25

Cited by 2 publications

(3 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The slope and intercept then correspond to the parameters n and K , respectively, and the resultant curve is shifted to determine the onset time of crystallization. Table presents the fitted values for the three different samples, including the crystallization halftime t 1/2 , which is given by …”

Section: Resultsmentioning

confidence: 99%

Fiber-Induced Crystallization in Elongational Flows

van Heugten,

Looijmans,

van Berlo

et al. 2024

Macromolecules

View full text Add to dashboard Cite

Morphology development at the fiber/matrix interphase in fiber-reinforced isotactic polypropylene composites is a widely studied topic. While the application of shear flow may strongly enhance the nucleation density around the fiber, little is known about the influence of fibers on the crystallization of polypropylene subjected to an extensional flow. In this work, the flow around a single glass fiber upon uniaxial elongation of the melt is examined using X-ray scattering and diffraction techniques and compared to the response measured for the neat matrix. A comparison between a neat and compatibilized matrix is made given the strong influence of the addition of an adhesion modifier on the bulk crystallization kinetics of polypropylene. The flow is applied using an in-house-built filament stretching extensional rheometer, which, due to its midfilament control scheme, allows for in situ X-ray experiments. Combined small-angle X-ray scattering/wide-angle X-ray diffraction patterns are acquired during the flow and subsequent crystallization step. Postcrystallization area scans of the filament show that the introduction of a single glass fiber gives rise to the development of β-phase crystals, particularly in the area around the fiber ends, and in contrast to what is observed for the matrix materials alone, where solely α-phase is found. Surprisingly enough, the addition of a single fiber (0.00045 vol %) alters the crystallizing polymorph in almost the entire filament. However, the addition of the adhesion modifier hinders the formation of β-phase crystals around the fiber due to an acceleration of the bulk crystallization kinetics. Finite element simulations provide insight into the flow field around the fiber during stretching and demonstrate that the flow is no longer uniaxial extension, but dominated by shear, even though the volumetric amount of fiber as compared to the matrix is negligible. These findings explain the experimental observation of substantial β-phase formation after the introduction of a single fiber, while this is not observed in the matrix material. Worth noting, the formation of β-phase polypropylene depends not only on the presence and the strength of the flow but predominantly on the type of flow, i.e., shear as opposed to elongation.

show abstract

Section: Resultsmentioning

confidence: 99%

Fiber-Induced Crystallization in Elongational Flows

van Heugten,

Looijmans,

van Berlo

et al. 2024

Macromolecules

View full text Add to dashboard Cite

show abstract

“…The space mission analysis and design activity aims at defining a space system that meets the mission requirements at the minimum over-all cost and risk [26]. The result may include spacecraft's systems and subsystems (e.g., payload, power, structure, attitude, communication, thermal), the mission planning and scheduling (from launch phase to operations, and ultimately spacecraft disposal), the ground segment (e.g., ground stations, control centers) and launch segment (e.g., launch facility, launch vehicle).…”

Section: The Role Of Space Mission Analysis and Designmentioning

confidence: 99%

“…The geometry of the trajectories obtained from MOLTO-IT Step 1 and MOLTO-ITStep 2 are displayed in Fig.5.22a and Fig.5.22b respectively. Detailed results for both mission profiles are presented in Table5 26…”

mentioning

confidence: 99%

Heuristic method based on Generalized Logarithmic Spirals for Low-Thrust trajectory design

González

Sanjurjo-Rivo

Arnedo

2016

AIAA/AAS Astrodynamics Specialist Conference

View full text Add to dashboard Cite

Department of Bioengineering and Aerospace EngineeringHybrid Multi-Objective Trajectory Optimization of Low-Thrust Space Mission Design by David Morante GonzálezThe overall goal of this dissertation is to develop multi-objective optimization algorithms for computing low-thrust trajectories. The thesis is motivated by the increasing number of space projects that will benefit from low-thrust propulsion technologies to gain unprecedented scientific, economic and social return. The low-cost design of such missions and the inclusion of concurrent engineering practices during the preliminary design phase demand advanced tools to rapidly explore different solutions and to benchmark them with respect to multiple conflicting criteria. However, the determination of optimal low-thrust transfers is a challenging task and remains an active research field that seeks performance improvements. This work contributes to increase the efficiency of searching wide design spaces, reduce the amount of necessary human involvement, and enhance the capabilities to include complex operational constraints. To that end, the general low-thrust trajectory optimization problem is stated as a multi-objective Hybrid Optimal Control Problem. This formulation allows to simultaneously optimize discrete decisionmaking processes, discrete dynamics, and the continuous low-thrust steering law. Within this framework, a sequential two-step solution approach is devised for two different scenarios. ContentsAcknowledgements v

show abstract

Mission and System Design

Cited by 2 publications

References 23 publications

Fiber-Induced Crystallization in Elongational Flows

Fiber-Induced Crystallization in Elongational Flows

Heuristic method based on Generalized Logarithmic Spirals for Low-Thrust trajectory design

Contact Info

Product

Resources

About