Abstract. The urban heat island phenomenon is one of the greatest challenges of the present days regarding the sustainability of our cities and settlements. A great amount of research has already been completed considering the urban heat island, with a significant part of them based on the utilization of remote sensing. The results show that in the case of the densely built-up areas of Hungary the maximal intensity of the urban heat island can be experienced in the industrial areas and in the extremely densely built-up zones, while water bodies and surfaces covered by vegetation proved to be the coolest zones under all circumstances. Thus, according to the results only water and green surfaces are capable of effectively reducing the urban heat island. Firstly, urban green surfaces and water bodies must be created to become capable of decreasing the urban heat island to the maximal extent. Secondly, it is possible to maximize the rate of green and water coverage within settlements only with the tools of urban planning. Thus it is essential in the case of urban planning to implement the existing regulation tools to prevent or minimize the further intensifying of the urban heat island.

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In the present days the effects of the global climate change can be observed everywhere. The negative impacts of this phenomenon, especially temperature rising, can be felt significantly in the cities of Central Europe. In these areas the effects of the global temperature rising and the urban heat island intensify each other. However, these phenomena grant the opportunity to find the most suitable vegetation types for moderating the warming up of such urban areas. The aim of this study is to provide support in determining these vegetation types. The examined area is Budapest, the capital of Hungary. This city has a wide selection of various urban green surfaces; consequently as a result of the examination it shall become clear which of these are the best vegetation types and the best vegetation structures in respect of the positive climatic effects. With the help of this study it shall also be clarified how the strength of this moderating effect depends on the water supply of the plants. The importance of this question lies within the fact that depending on the water supply different vegetation types may have totally different effects. Thus the main plant species and the structure of the canopy layers must be taken into thorough consideration. A collection of thermal infrared satellite images serve as the main source of data for this study. These images were produced in the last decade. They thoroughly show the thermal attributes of the examined area (green surface). The other important source of information is the examination of those structure species and vegetation types which are the most efficient in reducing the negative climate impacts under urban circumstances. The water supply dependence of this reducing effect is also very important piece of information.

Up to now interplanetary travel has virtually been unimaginable, mainly due to the great distance. The length of the Equator is 40 000 km, the distance between the Moon and the Earth is 400 000 km, and the orbit of the Mars is 40 million km away, thus the closest planet is a 1000 times farther than the greatest distance ever covered by man (to the Moon).Currently such long trips are impossible, as the applied propulsion provides only a relatively low speed (slightly higher than the second escape velocity, about 20 km/s); consequently such travels would take years. With the current technology there is simply no capacity for manned travels lasting such a long time.It is practical in all infrastructural, scientific, human, biological and psychological aspects to reduce the duration of the travel by increasing the speed. The radically reduced travel time would be highly beneficial also in the case of unmanned interplanetary travels. Meanwhile certain highly efficient propulsion systems capable of significantly increasing the speed of some space tools already exist; these are the ion thrusters.Due to their small thrust the widespread of ion thrusters is strongly limited; however, they are able to continuously provide this thrust for a long period. They have several disadvantages too, firstly the relatively low outflowing speed of the propellant (only a few 10 km/s, which is better in one order of magnitude than the speed provided by chemical fuelled rockets); in the second place the necessity of an outer electric energy source, which usually has very low performance in the case of the currently widely used ion thrusters. Furthermore, the efficiency of the currently used ion thrusters cannot exceed a certain value, as a remarkable amount of the electric energy has to be utilized for the ionisation of the propellant (usually xenon) and only the remaining amount can be used for accelerating the ions (for the thrust itself).The present study introduces a radically new ion thruster construction, in which the energy required by the ionisation can be radically lowered; furthermore the propellant used in this solution provides a significantly higher propellant speed. The possibility of using much more efficient electric energy sources will also be introduced, along with the possibility of another type of propulsion in accordance to the varying characteristics of different interplanetary journeys.The most essential element of the new propulsion system is the catalyser used instead of the ionisation chamber. The catalyser sets strong limits to the possible material of the propellant, which in turn is beneficial in this case. The useable propellant is hydrogen, which presently is absolutely unused as an ion thruster propellant due to the difficulties regarding its storage and transport (it is usually stored as liquid hydrogen, which is extremely dangerous). Its greatest disadvantage is that its energy requirement for ionisation is extremely high. However, the hydrogen (protium) ion has far the best electric charge/mass ratio; co...