Mission analysis and performance comparison for an Advanced Solar Photon Thruster

The so-called “compound solar sail”, also known as “Solar Photon Thruster” (SPT), is a design concept, for which the two basic functions of the solar sail, namely light collection and thrust direction, are uncoupled. In this paper, we introduce a novel SPT concept, termed the Advanced Solar Photon Thruster (ASPT), which does not suffer from the simplified assumptions that have been made for the analysis of compound solar sails in previous studies. After having presented the equations that describe the force on the ASPT and after having performed a detailed design analysis, the performance of the ASPT with respect to the conventional flat solar sail (FSS) is investigated for three interplanetary mission scenarios: an Earth–Venus rendezvous, where the solar sail has to spiral towards the Sun, an Earth–Mars rendezvous, where the solar sail has to spiral away from the Sun, and an Earth-NEA rendezvous (to near-Earth asteroid 1996FG3), where a large change in orbital eccentricity is required. The investigated solar sails have realistic near-term characteristic accelerations between 0.1 and 0.2 mm/s². Our results show that an SPT is not superior to the flat solar sail unless very idealistic assumptions are made.     

An alternative to Hermes a solution for the European space industry

A variety of valuable roles can be foreseen during the next two decades for a reusable, piloted launch vehicle with a small payload. The authors argue that unfortunately, as currently proposed, the Hermes-Ariane 5 vehicle will not be able to fill the roles required. The authors propose a reusable aerospace transporter-a variant of Hermes - which will provide a solution and allow Europe to take the lead in developing the first fully reusable launch vehicle.     

Observations of ionospheric irregularities and its correspondence with sporadic e occurrence over South Korea and Japan

This study analyzed the occurrence of ionospheric irregularities over South Korea and Japan (mid-latitudes) during the years 2010–2015. The irregularities were quantified using the rate of change of total electron content (TEC) index (ROTI), which detects irregularities with scale sizes in the range of 400 m–2.5 km. The ROTI threshold for an ionospheric irregularity to have occurred was set as 0.1 TECU/min. Results showed that ionospheric irregularities mostly occur during night-time and around local noon-time in the seasons of spring and summer. In addition, the percentage of ionospheric irregularities had a high positive correlation with solar flux (F10.7) (r > 0.72). For the first time, we showed good correspondence between ionospheric irregularities measured by the ROTI index and sporadic E (Es). The median ROTI associated with ionospheric irregularities over a South Korea station (DAEJ) and a Japan station (KGNI) were 0.131 and 0.125 TECU/min, respectively. However, in severe cases of ionospheric irregularities, the ROTI values over DAEJ (KGNI) can reach 0.246 (0.217) and 0.314 (0.339) TECU/min during day and night, respectively. These critical ROTI values can be important in interpreting and monitoring ionospheric irregularity occurrence over South Korea and Japan.     

美国开始试验"变形"飞机

美国国防预研局将于今年7月开始对两种可以在飞行中改变机翼外形的原型飞机进行结构和空气动力试验。据称,这种改变机翼外形技术能在飞行中彻底改变机翼外形,甚至具有使机翼表面积扩大到原来的300%以上的潜在能力。     

Nitrous oxide cooling in hybrid rocket nozzles

The Department of Mechanical Engineering at the California Polytechnic State University, San Luis Obispo, has developed an innovative program of experimental research and development on hybrid rocket motors (where the fuel and the oxidizer are in different phases prior to combustion). One project currently underway involves the development of aerospike nozzles for such motors. These nozzles, however, are even more susceptible to throat ablation than regular converging–diverging nozzles, due the nature of their flow expansion mechanism. This paper presents the result of a recent development project focused on reducing throat ablation in hybrid rocket motor nozzles. Although the method is specifically targeted at increasing the life and operating range of aerospike nozzles, this paper describes its proof-of-concept implementation on conventional nozzles. The method is based on a regenerative cooling mechanism that differs in practice from that used in liquid propellant motors. A series of experimental tests demonstrate that this new method is not only effective at reducing damage in the most ablative region of the nozzle, but that the nozzle can survive multiple test runs.     

碳纤维复合材料电火花加工(EDM)机理究研

应用于航空航天技术的碳纤维复合材料具有相当高的比强度、高弹性模量、重量轻、热膨胀小、以及具有导电性、对酸、碱有机溶剂有很大的耐蚀性等诸多的优点。但由于材料本身为纤维织物的层压浸渍结构,使其在切削加工时难于达到较高的光洁度与精度,     

Flap contour optimization for highly integrated SERN nozzles

The performance of a Single Expansion Ramp Nozzle (SERN) for hypersonic cruise vehicles is examined with focus on the flow at the nozzle flap and the corresponding separation of the boundary layer. Two wind tunnel models are used to analyze the interaction of the free stream and the nozzle flow and the flow at the flap in detail. A finite element flow code is employed to support the design of the flap model and the analysis of the flow.Comparative contour studies show that the size and the location of the separation at the flap cowl and therefore the aerodynamic quality can be influenced by optimizing the flap cowl contour. The position of the separation is measured for different contours and varying Reynolds numbers at laminar, transitional and turbulent flow conditions. Numerical studies of a nozzle/afterbody configuration suggest an improvement of up to 3.5% in axial thrust for optimized flap contours in the examined Mach range between 1.64 and 6. At the same time the rotation of the thrust vector is reduced by up to 5° at lower Mach numbers.     

Geometry-free linear combinations for Galileo

Global navigation satellites of the European Galileo system transmit code signals on four carriers in the L1, E5a, E5b and E6 band.New geometry-free linear combinations are presented that eliminate the geometry terms (user to satellite ranges and orbital errors), the clock errors of the user and satellites and the tropospheric delay. The remaining parameters of these carrier phase combinations include integer ambiguities, ionospheric delays, carrier phase multipath and phase noise. The weighting coefficients are designed such that the integer nature of ambiguities is maintained. The use of four frequency combinations is highly recommended due to a noise reduction of up to 14.4 dB and an ionospheric reduction of up to 25.6 dB compared to two frequency geometry-free combinations.Moreover, a modified Least-squares Ambiguity Decorrelation Adjustment (LAMBDA) algorithm is suggested, which differs in two points from the traditional approach: the baseline is replaced by the ionospheric delay and the correlation is caused by linear combinations instead of double differences. For correct ambiguity resolution, the ionospheric delay can be determined with millimeter accuracy. This is quite beneficial as the ionosphere represents the largest source of error for absolute positioning.     

Development status of AEOLDOS – A deorbit module for small satellites

A prototype CubeSat module to deploy a gossamer aerobrake, using strain stored in tape-springs, at end-of-life is described. A novel hub geometry to reduce bending shock at end-of-deployment while simultaneously permitting radial, as opposed to tangential, deployment is proposed. The rpm of the hub is measured under various deployment conditions to verify that the system offers highly-repeatable performance, while high-speed photography is used to characterise the behaviour of the tape-spring during unspooling and contrast it to the behaviour of a traditional tangential-deployment system. Secondly the folding pattern of the membrane, which takes advantage of the symmetrical deployment offered by the petal hub, is developed and the unfolding mechanism is verified by numerical and experimental analysis. Finally, the release of the stored strain is considered and a novel burn-though device is designed and prototyped to meet this requirement.     

Generic functional modelling of multi-pulse auto-transformer rectifier units for more-electric aircraft applications

The Auto-Transformer Rectifier Unit (ATRU) is one preferred solution for high-power AC/DC power conversion in aircraft. This is mainly due to its simple structure, high reliability and reduced kVA ratings. Indeed, the ATRU has become a preferred AC/DC solution to supply power to the electric environment control system on-board future aircraft. In this paper, a general modelling method for ATRUs is introduced. The developed model is based on the fact that the DC voltage and current are strongly related to the voltage and current vectors at the AC terminals of ATRUs. In this paper, we carry on our research in modelling symmetric 18-pulse ATRUs and develop a generic modelling technique. The developed generic model can study not only symmetric but also asymmetric ATRUs. An 18-pulse asymmetric ATRU is used to demonstrate the accuracy and efficiency of the developed model by comparing with corresponding detailed switching SABER models provided by our industrial partner. The functional models also allow accelerated and accurate simulations and thus enable whole-scale more-electric aircraft electrical power system studies in the future.