Use of a evolutionary algorithm to optimize interplanetary transfers

In this paper, it was studied the optimization of the cost of interplanetary missions with emphasis on reducing fuel consumption. To achieve this goal, a genetic algorithm was implemented to optimize the total impulse of orbital transfer. It was implemented a case of sending a space vehicle from Earth to a another planet using a gravity assist maneuver (swing by), in this paper it was chose sending a spacecraft from Earth to Mars with a close approach to the Venus. The method employed can be used for impulsive interplanetary missions in general, and so the solution found can become an initial solution for numerical methods of optimization of low thrust maneuvers

OXIDIZER AND GAS-ENVIRONMENT EFFECTS ON AFTERBURNING REACTIONS AND EXPLOSION PERFORMANCES OF HMX-BASED THERMOBARIC EXPLOSIVES

In this paper, confined explosions of HMX-based thermobaric explosives containing oxidizers in a spherical chamber were studied by changing the type of the oxidizer and the oxygen concentration in the environment. Based on an in-house developed optical-electrical system, the optical radiation signals of Al2O3 during the afterburning reaction were recorded. The results show that aluminum particles (5.4 µm) were strongly dependent on the oxygen concentration in the environment. Increasing the oxygen concentration can prolong the oxidation duration of Al and enhance the optical radiation intensity of Al2O3. The optical radiation result for Al2O3 in O2 and air showed that aluminum particles (the mass fraction was 33 %) were not completely oxidized in the air, and the oxidation duration was 500–700 µs. Moreover, the pressure data of the blast waves was obtained using a pressure-measurement system. The results showed that an increase in the oxygen concentration of the explosive could further enhance the total impulse, especially an addition of KP (its mass fraction was 10 %) could increase the total impulse by about 9 %.

Design and In-orbit Demonstration of REGULUS, an Iodine electric propulsion system

REGULUS is an Iodine-based electric propulsion system. It has been designed and manufactured at the Italian company Technology for Propulsion and Innovation SpA (T4i). REGULUS integrates the Magnetically Enhanced Plasma Thruster (MEPT) and its subsystems, namely electronics, fluidic, and thermo-structural in a volume of 1.5 U. The mass envelope is 2.5 kg, including propellant. REGULUS targets CubeSat platforms larger than 6 U and CubeSat carriers. A thrust T = 0.60 mN and a specific impulse Isp = 600 s are achieved with an input power of P = 50 W; the nominal total impulse is Itot = 3000 Ns. REGULUS has been integrated on-board of the UniSat-7 satellite and its In-orbit Demonstration (IoD) is currently ongoing. The principal topics addressed in this work are: (i) design of REGULUS, (ii) comparison of the propulsive performance obtained operating the MEPT with different propellants, namely Xenon and Iodine, (iii) qualification and acceptance tests, (iv) plume analysis, (v) the IoD.

Further evidence against a force-velocity trade-off in muscle driven dynamic lever systems

Levers impose a force-velocity trade-off. In static conditions, a larger moment arm increases a muscle’s force capacity, and a smaller moment arm amplifies output velocity. However, muscle force is influenced by contractile velocity and fiber length, while contractile velocity is influenced by the inertial properties of the lever system. We hypothesize that these dynamic effects constrain the functional output of a muscle-lever system. We predict that there is an optimal moment arm to maximize output velocity for any given muscle-lever configuration. Here we test this hypothesis by computationally building and systematically modifying a simple lever system. We generated 3600 modifications of this model with muscles with varying optimal fiber lengths, moment arms and starting normalized muscle lengths. For each model we simulated the motion that results from 100% activation and extracted the maximum output lever velocity. In contrast to a tradeoff between force and velocity in a lever system, we found that there was, instead, an optimal moment arm which maximized both velocity and total impulse. Increasing output velocity always required increasing output force. From this we conclude that in a dynamic lever system where muscle activation is held constant, there is no tradeoff between force and velocity.

Design and Test of a Student Hybrid Rocket Engine with an External Carbon Fiber Composite Structure

The development of hybrid rockets offers excellent opportunities for the practical education of students at universities due to the high safety and relatively low complexity of the rocket propulsion system. During the German educational program Studentische Experimental-Raketen (STERN), students of the Technische Universität Braunschweig obtain the possibility to design and launch a sounding rocket with a hybrid engine. The design of the engine HYDRA 4X (HYbridDemonstrations-RaketenAntrieb) is presented, and the results of the first engine tests are discussed. The results for measured regression rates are compared to the results from the literature. Furthermore, the impact of the lightweight casing material carbon fiber-reinforced plastic (CFRP) on the hybrid engine mass and flight apogee altitude is examined for rockets with different total impulse classes (10 to 50 kNs). It is shown that the benefit of a lightweight casing material on engine mass decreases with an increasing total impulse. However, a higher gain on apogee altitude, especially for bigger rockets with a comparable high total impulse, is shown.

Design and Test of a Student Hybrid Rocket Engine with an External Carbon Fiber Composite Structure

The development of hybrid rockets offers excellent opportunities for the practical education of students at universities due to a high safety and a relatively low complexity of the rocket propulsion system. During the German educational program STERN, students of the Technische Universität Braunschweig obtain the possibility to design and launch a sounding rocket with a hybrid engine. The design of engine HYDRA 4X is presented and results of first engine tests are discussed. Results for measured regression rates are compared to results from literature. Furthermore, the impact of the lightweight casing material CFRP on the hybrid engine mass and flight apogee altitude is examined for rockets with different total impulse classes (10 to 50 kNs). It is shown that the benefit of a lightweight casing material on engine mass decreases with an increasing total impulse. However, a higher gain on apogee altitude, especially for bigger rockets with a comparable high total impulse is shown.

How Many Impulses Redux

A central problem in orbit transfer optimization is to determine the number, time, direction, and magnitude of velocity impulses that minimize the total impulse. This problem was posed in 1967 by T. N. Edelbaum, and while notable advances have been made, a rigorous means to answer Edelbaum’s question for multiple-revolution maneuvers has remained elusive for over five decades. We revisit Edelbaum’s question by taking a bottom-up approach to generate a minimum-fuel switching surface. Sweeping through time profiles of the minimum-fuel switching function for increasing admissible thrust magnitude, and in the high-thrust limit, we find that the continuous thrust switching surface reveals the N-impulse solution. It is also shown that a fundamental minimum-thrust solution plays a pivotal role in our process to determine the optimal minimum-fuel maneuver for all thrust levels. Remarkably, we find that the answer to Edelbaum’s question is not generally unique, but is frequently a set of equal-Δv extremals. We further find, when Edelbaum’s question is refined to seek the number of finite-duration thrust arcs for a specific rocket engine, that a unique extremal is usually found. Numerical results demonstrate the ideas and their utility for several interplanetary and Earth-bound optimal transfers that consist of up to eleven impulses or, for finite thrust, short thrust arcs. Another significant contribution of the paper can be viewed as a unification in astrodynamics where the connection between impulsive and continuous-thrust trajectories are demonstrated through the notion of optimal switching surfaces.

11 Use of pressure mat gait analysis in measuring pain following normal parturition in dairy cows

Research investigating the pain of normal parturition is lacking as there are few objective methods for measuring pain. The objective of this research was to describe the gait of cows following eutocia using pressure-mat gait analysis; and determine if meloxicam alters the gait of cows. Twenty Holstein cows within 26 h of unassisted calving were enrolled into the study. Treatment groups included: 1) post-partum cows administered meloxicam (MEL; n = 10); and 2) post-partum cows administered placebo (PLBO; n = 10). Meloxicam was administered by oral bolus at 1 mg/kg within 26 hours of calving. Placebo cows were given an oral bolus of dry whey powder within 26 hours of calving. A commercially available floor mat-based pressure/force measurement system was used to compare ambulation between treatment groups. Cows were walked across the mat before treatment administration, and 2, 4, 6, 8, 12, 24, 48 and 72 hrs post-treatment. The percent of total force, percent total contact pressure, and percent total impulse of the rear limbs was calculated. Outcome measures were statistically analyzed using repeated measures, with the cow serving as the experimental unit. Cows in the MEL group placed 48.9% (95% CI: 47.4 – 50.5%) of total force on the rear limbs compared to 46.3% (95% CI: 44.7 – 47.9%) in PLBO cows (P = 0.02). Total impulse on their rear limbs for the MEL cows was 50.5% (95% CI: 48.6 – 52.4%) compared to 46.7% (95% CI: 44.8 – 48.7%) for the PLBO cows (P = 0.01). No differences in contact pressure of the rear limbs was observed (P = 0.27). The PLBO cows had a longer gait 101.3 cm (95% CI: 95.9 – 106.6 cm) versus 90.8 cm (95% CI: 85.4 – 96.1 cm) (P = 0.03). These findings show meloxicam treated cows have altered weight distribution to the rear limbs as measured by pressure mat gait analysis, suggesting meloxicam may effectively treat post-partum pain.