Design and simulation for large parafoil fix line object homing algorithm

Traditional parafoil homing usually uses a point as object. As the mobility of parafoil is limited by its glide ratio and wind, in some cases when the parafoil scatter area is large, or the glide ratio of parafoil is small, the deviation of its landing point to object point will be arduous to control. Accordingly, during these situations, when parafoil is used in recovery of spacecraft or satellite, the landing area of parafoil can be set as a rectangle, and the object of parafoil can be set as a line segment. The thesis of this work is designing an algorithm for parafoil homing using line segment as object. The algorithm of wind velocity and direction calculation in different flying segments was also investigated. The algorithm designed navigates the parafoil to land into the predestined area and largely reduce the probability of recovery loads falling to unwanted area to damage houses and people.

Ivar asteroid rendezvous mission system scenario and trajectory design

The asteroid exploration opportunities are searched and calculated with launch dates in 2006 to2010, and with asteroid Ivar 1627 as the target, the spacecraft and its subsystems are designed and analyzed,and the transfer trajectory is designed using △VEGA technology for the asteroid rendezvous. The design resultssatisfied the energy requirements for small explorers.

The Use of Drones in Forestry

Recently, drones have found applicability in a variety of study fields, one of these being forestry, where an increasing interest is given to this segment of technology, especially due to the high-resolution data that can be collected flexibly in a short time and at a relatively low price. Also, drones have an important role in filling the gaps of common data collected using manned aircraft or satellite remote sensing, while having many advantages both in research and in various practical applications particularly in forestry as well as in land use in general. This paper aims to briefly describe the different approaches of applications of UAVs （Unmanned Aircraft Vehicles） in forestry, such as forest mapping, forest management planning, canopy height model creation or mapping forest gaps. These approaches have great potential in the near future applications and their quick implementation in a variety of situations is desirable for the sustainable management of forests.

The State of Arts of Hall Thruster

Electric propulsion is broadly defined as the acceleration of a working fluid for propulsion by electrical heating and/or by electric and magnetic body forces. Compared with chemical propulsion, electric propulsion has the characteristic of higher specific impulse, lower thrust, lighter weight and longer lifetime. So electric propulsion is generally suitable for satellite attitude control, the orbit transfer and raising, orbit correction, resistance compensate, position keeping, reposi- tion, space exploration and interplanetary flight.

Study of Space Reactors for Exploration Missions

Nuclear propulsion has been studied for many decades. The power density of nuclear fission is much higher than chemical process, and for missions to outer solar system requiring several hundred of kilowatts, or for flexible manned missions to Mars requiring several megawatts, nuclear electric propulsion might be the only option offering a reasonable mass in low earth orbit. Despite the existence of low power experiences--SNAP10 in the 60＇s or Buk/Topaz in the 60-80＇s--no high power reactor has been developed： investment cost, long term timeframe, high technological challenges and radioactive hazards are the main challenges we must overtake. However, it seems reasonable to look at the technical challenges that have to be overcome for a next generation of nuclear electric systems for space exploration. This paper will present some recent studies going on in France, on space reactors for exploration. Three classes of power have been considered： 10 kWe, 100 kWe, and several megawatts. Available data from previous studies and developments performed in Russia, USA, and Europe have been collected and gave us a large overview of potential technical solutions. This was the starting point of a trade-off analysis aiming at the selection of the best options, with regards to the technological readiness level in France and Europe. The resulting preliminary designs will be presented and critical technologies needing maturation activities will be highlighted.

Merlin and Stonehenge in Daina Chaviano＇s Fables of an Extraterrestrial Grandmother

When Merlin first appears in Chaviano＇s Fables of an Extraterrestrial Grandmother as the wizard Soio, he reflects the imagination of Ana, the adolescent protagonist of the science fiction novel as she is in the process of writing the very novel the reader is reading. Later she will discover that her fictional creations are not the invention of her imagination but exist autonomously in parallel universes and are using her as a vehicle of inter-dimensional travel through time and space. Soio/Merlin gazes into his crystal ball, a microcosm that gathers the space-time energy fields of the parallel universes, and sees visions of the protagonists whose modes of existence are real in one and fictional in another parallel universe. Merlin is a Druid in exile from the Neolithic world of Celtic Britain who has crossed over from earthly life to existence in Rybel, a parallel universe. He had crossed over by lining up the Stone of the Past and the Mirror of the Future at the great circle of Stonehenge. The stone circle functioned as an astronomical observatory. Stonehenge is a microcosm, a circle that reflects and coordinates the larger circle of the universe, symbolized and embodied in the sphere or crystal ball that Merlin transmits to Ana in the form of the novel being read. All the characters are trying to coordinate dimensions of space and time in order to fly from one parallel universe to another. Chaviano emphasizes crossing boundaries of time and space. Her characters live in one world but belonging to another, yearn to make contact with the forces of the universe that will bring them home. Chaviano＇s use of the Merlin legend is original and takes into account archaeological evidence about the Celts, Druids, and Stonehenge.

LM-2C Launched Two Sets of Yaogan 30 Satellites

LM-2C launch vehicles launched two sets of Yaogan 30 satellites from the Xichang Satellite Launch Center respectively on November 25 and December 26.The second one was the last launch mission carried out by CASC in 2017.LM-2C was developed by the China Academy of Launch Vehicle Technology.It is the only one among the LM series launch vehicle that can conduct flight missions from the three inland launch sites.

A stealthy method to determine the relative position and velocity for satellite formation flying

To achieve the satellite formation control and the succeed formation missions, we present a new stealthy method to determine the relative states between formation satellites. In this method, the combination of a CCD camera and laser radar is used as the relative measure sensors. To reduce electromagnetic radiation, the laser radar works intermittently to minimize the probability of being discovered. And an unscented Kalman filter (UKF) is applied to estimate the relative states. The observability of this method is analyzed. The validity and effectiveness of the method is demonstrated in a typical application of formation relative navigation.

Airborne test flight of HY-2A satellite microwave scatterometer and data analysis

This paper introduces the background, aim, experimental design, configuration and data processing for an airborne test flight of the HY-2 Microwave scatterometer(HSCAT). The aim was to evaluate HSCAT performance and a developed data processing algorithm for the HSCAT before launch. There were three test flights of the scatterometer, on January 15, 18 and 22, 2010, over the South China Sea near Lingshui, Hainan. The test flights successfully generated simultaneous airborne scatterometer normalized radar cross section(NRCS), ASCAT wind, and ship-borne-measured wind datasets, which were used to analyze HSCAT performance. Azimuthal dependence of the NRCS relative to the wind direction was nearly cos(2w), with NRCS minima at crosswind directions, and maxima near upwind and downwind. The NRCS also showed a small difference between upwind and downwind directions, with upwind crosssections generally larger than those downwind. The dependence of airborne scatterometer NRCS on wind direction and speed showed favorable consistency with the NASA scatterometer geophysical model function(NSCAT GMF), indicating satisfactory HSCAT performance.

Trophallaxis network control approach to formation flight of multiple unmanned aerial vehicles

A novel network control method based on trophaUaxis mechanism is applied to the formation flight problem for multiple un- manned aerial vehicles （UAVs）. Firstly, the multiple UAVs formation flight system based on trophallaxis network control is given. Then, the model of leader-follower formation flight with a virtual leader based on trophallaxis network control is pre- sented, and the influence of time delays on the network performance is analyzed. A particle swarm optimization （PSO）-based formation controller is proposed for solving the leader-follower formation flight system. The proposed method is applied to five UAVs for achieving a ＇V＇ formation, and a series of experimental results show its feasibility and validity. The proposed control algorithm is also a promising control strategy for formation flight of multiple unmanned underwater vehicles （UUVs）, unmanned ground vehicles （UGVs）, missiles and satellites.

Analysis of residual gas disturbance on the inner satellite of Inner Formation Flying System

The Inner Formation Flying System （IFFS） consisting of an freely flying in the shield cavity can construct a pure gravity outer satellite and an inner satellite which is a sphere proof mass orbit to precisely detect the earth gravity field. The residual gas in the cavity is a significant disturbance source due to the temperature inhomogeneity and relative motion of the inner satellite. The expressions of the disturbance forces were derived based on the property of rarefied gas, including the radiometer effect and the damping force. According to the current design of IFFS, heat transfer analysis of the cavity and the inner satellite was carried out, and the surface temperature distribution of the cavity and the inner satellite was given. The relative motion of the inner satellite was obtained from the formation control simulation of IFFS. Then the residual gas disturbance was calculated. The disturbance acceleration acting on the inner satellite due to the radiometer effect was on the order of 10^-11 m s^-2 and the damping acceleration was on the order of 10^-15 m s^-2.