Asymmetric wedging of elastic material with the formation of separation zones

The problem of asymmetrical movement of a thin rigid impactor in elastic material is considered with subsonic and transonic velocities. For all considered range of velocities the flow diagram was determined for contours in the forms of wedge and ogive. There is a limiting speed value when the impactor moves with velocity higher than the speed of transverse wave at which the separation zone in the nasal part of the body disappears. At this velocity forces acting on the impactor are independent of its shape.     

Eugen Sänger: Eminent space pioneer

In international literature on astronautics, three main space pioneers are mentioned: Konstantin E. Tsiolkovsky, Robert H. Goddard and Hermann Oberth. There are other two space pioneers that are very rarely mentioned: Robert Esnault-Pelterie and Eugen Sänger. Pelterie is known particularly in Europe, and Sänger is mentioned in the second half of the 20th century normally only in connection with space shuttle flights.Taking a look at Sänger's work and heritage, it is obvious that he greatly influenced the development of astronautics in terms of purely theoretical dissertations on achievable limits of space research as well as in terms of technical approaches to achieving the short- and long-term goals of astronautics, and in terms of setting tasks for organizing mankind to achieve these goals. Sänger's book “The Technology of Rocket Flight” was the first study based not only on basic research, but also on the applied research that he conducted and the findings of which he published in various papers. Sänger was clearly connected with and influenced the development of two experimental research groups in the US in the 1930s, which resulted in two of the most significant companies in the US in the 1950s that manufactured liquid propellant rocket engines. Basic and applied research in the field of space planes resulted in construction of rocket planes such as the US space shuttle and Soviet Buran shuttle.Sänger's research on subsonic and supersonic ramjets in combination with a turbojet engine provided a basis for developing this promising propulsion for use in subsequent space planes designed for flights into low Earth orbits. His pioneering work on the photon rocket represents human achievements in reaching almost unimaginable limits of space research.By striving for a peaceful international approach to space research, Sänger participated in establishing the non-governmental organization IAF (International Astronautical Federation) and realized his idea that space research is a concern for all mankind. He was therefore appointed the first president of the IAF.The paper presents how Sänger influenced the development of rocket technology and astronautics, which definitely ranks him with the first three space pioneers.     

Optimising filtering of two-line element sets to increase re-entry prediction accuracy for GTO objects

Predicting re-entry epoch of space objects enables managing the risk to ground population. Predictions are particularly difficult for objects in highly-elliptical orbits, and important for objects with components that can survive re-entry, e.g. rocket bodies (R/Bs). This paper presents a methodology to filter two-line element sets (TLEs) to facilitate accurate re-entry prediction of such objects. Difficulties in using TLEs for precise analyses are highlighted and a set of filters that identifies erroneous element sets is developed. The filter settings are optimised using an artificially generated TLE time series. Optimisation results are verified on real TLEs by analysing the automatically found outliers for exemplar R/Bs. Based on a study of 96 historical re-entries, it is shown that TLE filtering is necessary on all orbital elements that are being used in a given analysis in order to avoid considerably inaccurate results.