Prediction of Tail-Off Pressure Peak Anomaly on Small-Scale Rocket Motors

Numerical studies intended to predict solid rocket motors anomalies are the major contributors when developing strategies to both limit expensive fire tests and to investigate and understand the physical phenomena from which anomalies can arise. This paper aims to present a mathematical–physical method to evaluate the pressure peak, namely Friedman Curl, occurring at the tail-off phase of small-scale rocket motors. Such phenomenon is linked to the grain solid particles arrangement (i.e., packing effect); indeed, those particles show a tendency to accumulate at a certain distance from the metallic case, implying a local burn rate increment and a combustion chamber pressure rise close to the tail-off phase. Comparisons between experimental and simulated combustion chamber pressure profiles are outlined to prove the effectiveness of the mathematical–physical approach. Simulations were carried out with an internal ballistic simulation tool developed by the authors of this work

Mission analysis for two potential asteroids threat scenarios: Optimal impact strategies and technology evaluation

The Space Mission Planning Advisory Group SMPAG's mission is to prepare for an international response to a Near Earth Object impact threat through the exchange of information, development of options for collaborative research and mission opportunities, and to conduct Near Earth Object (NEO) impact threat mitigation planning activities. This paper presents the preliminary work performed by the Italian Space Agency Delegation for defining few reference missions for different NEO-threat scenarios and carrying out Phase 0 studies. In this paper two scenarios are identified to study the possible response in case of a real NEO-threat. A direct and resonant impact scenario for an asteroid deflection mission are identified resembling to the asteroid 2010RF12 but with an increased asteroid mass. Then the mission analysis and spacecraft design for the direct impact case is performed and the results discussed

GrailQuest & HERMES: Hunting for Gravitational Wave Electromagnetic Counterparts and Probing Space-Time Quantum Foam

Within Quantum Gravity theories, different models for space-time quantisation predict an energy dependent speed for photons. Although the predicted discrepancies are minuscule, GRB, occurring at cosmological distances, could be used to detect this signature of space-time granularity with a new concept of modular observatory of huge overall collecting area consisting in a fleet of small satellites in low orbits, with sub-microsecond time resolution and wide energy band (keV-MeV). The enormous number of collected photons will allow to effectively search these energy dependent delays. Moreover, GrailQuest will allow to perform temporal triangulation of high signal-to-noise impulsive events with arc-second positional accuracies: an extraordinary sensitive X-ray/Gamma all-sky monitor crucial for hunting the elusive electromagnetic counterparts of GW. A pathfinder of GrailQuest is already under development through the HERMES project: a fleet of six 3U cube-sats to be launched by 2021/22

Detection of the Multipath Effect in the ING2 GPS Station with a New Developed Software

The multipath effect is one of the major error sources affecting the Global Positioning System (GPS) observables both in static and kinematic precise positioning and navigation. This effect occurs when satellite\u2019s signal is reflected from the ground or other objects in the vicinity of the antenna and it is received as secondary path which is superimposed on the direct-path signal. The effect of the multipath on the GPS observables can cause longer propagation time and significant distortion of the signal waveform amplitude and phase. By using a Differential GPS (DGPS) it is possible to reduce the clock, ephemeris, ionospheric and tropospheric errors to centimeter level. Afterwards the multipath effect can be considered the main error source in GPS measurements in a meters level. A GPS data analysis software (S/W) has been developed at the Radio Science Laboratory of the II Faculty of Engineering of the University of Bologna, with the purpose of the zenith wet path delay estimation due to the Earth troposphere based on the double difference techniques. Since the Earth troposphere delay estimation has been detected and some positive tests has been undertaken, the S/W has been used for the detection of the multipath effect in the stations involved in the analysis. A preliminary test has been undertaken with the GPS station installed in the Radio Science Laboratory of the University of Bologna, named ING2

Test Campaign of an Earth Troposphere Calibration System Based on Dual-Frequency GPS Measurements

The path delay introduced by the Earth troposphere is one of the main error sources for deep space tracking observables. In order to remove all the error sources from these observables, a precise Earth troposphere calibration system has to be developed in order to estimate this delay. ESA\u2019s Deep Space Antenna are currently equipped with meteorological stations, capable of measuring the atmospheric parameters and, thanks to mathematical models, to reconstruct the dry component of the Earth troposphere, leaving a residual, uncalibrated wet component which represents about 10% of the total tropospheric delay. In order to avoid this, the short time-scale variations of the wet component of the Earth troposphere must be calibrated at ESA deep space antennas by means of water vapour radiometers or GPS measurements. ESA ground stations must be upgraded to media calibration systems at least capable to calibrate the total (dry and wet) zenith path delay at centimetre level, to allow reducing S/C navigation uncertainties. The natural choice is the use of the high performance GPS receivers already installed at all ESA ground station complexes for station location purposes. At the Radio Science laboratory of the University of Bologna a GPS-based software has been developed and tested and the results compared with those obtained by other techniques

GNSS-based Troposphere Zenith Wet Delay Estimation Comparison with Microwave Radiometer At Cabauw

At the Radio Science laboratory of the University of Bologna in Forlì a dedicated GNSS data analysis software (S/W) code was developed as part of the radio science activities connected to the future ESA BepiColombo and ExoMars missions. After a short description of the algorithms used in the S/W code developed, the paper will reports the results of an intensive test campaign for the qualification of the S/W breadboard. The GPS-based delay estimations have been compared with the ESA microwave radiometer (MWR) measurements performed at the atmospheric remote sensing station of Cabauw, The Netherlands, of the KNMI (Dutch Meteorological Office) by ESA/ESTEC in the framework of the National Dutch CESAR project. The same GPS data has been processed by the KNMI data analysis centre and further comparisons have been undertaken with the UniBo GNSS S/W results