University Of Toronto Institute For Aerospace Studies Research Articles

Planning Stable and Efficient Paths for Reconfigurable Robots On Uneven Terrain

An analytical strategy to generate stable paths for reconfigurable mobile robots such as those equipped with manipulator arms and/or flippers, operating in an uneven environment whilst also meeting additional navigational objectives is hereby proposed. The suggested solution looks at minimising the length of the traversed path and the energy expenditure in changing postures, and also accounts for additional constraints in terms of sensor visibility and traction. This is particularly applicable to operations such as search and rescue where observing the environment for locating victims is the major objective, although this technique can be generalised to incorporate other potentially conflicting objectives (e.g. maximising ground clearance for a legged robot). The validity of the proposed approach is evaluated with two popular graph-based planners (A* and RRT) on a multi-tracked robot fitted with a manipulator arm and a range camera. Two challenging 3D terrain data sets have been employed: one obtained whilst operating the robot in a mock-up urban search and rescue (USAR) arena, and a second one, a reference on-line data set acquired on the quasi-outdoor rover testing facility at the University of Toronto Institute for Aerospace Studies (UTIAS).

The BRITE Constellation Nanosatellite Mission: Testing, Commissioning, and Operations**Based on data collected by the BRITE Constellation satellite mission, designed, built, launched, operated and supported by the Austrian Research Promotion Agency (FFG), the University of Vienna, the Technical University of Graz, the Canadian Space Agency (CSA), the University of Toronto Institute for Aerospace Studies (UTIAS), the Foundation for Polish Science &

BRIght Target Explorer (BRITE) Constellation, the first nanosatellite mission applied to astrophysical research, is a collaboration among Austria, Canada and Poland. The fleet of satellites (6 launched; 5 functioning) performs precise optical photometry of the brightest stars in the night sky. A pioneering mission like BRITE—with optics and instruments restricted to small volume, mass and power in several nanosatellites, whose measurements must be coordinated in orbit—poses many unique challenges. We discuss the technical issues, including problems encountered during on-orbit commissioning (especially higher-than-expected sensitivity of the CCDs to particle radiation). We describe in detail how the BRITE team has mitigated these problems, and provide a complete overview of mission operations. This paper serves as a template for how to effectively plan, build and operate future low-cost niche-driven space astronomy missions.

Canadian advanced nanospace experiment 2: Scientific and technological innovation on a three-kilogram satellite

The Space Flight Laboratory (SFL) at the University of Toronto Institute for Aerospace Studies (UTIAS) is developing its second nanosatellite, the Canadian Advanced Nanospace eXperiment 2 (CanX-2) as a part of the CanX program. The objective of the CanX program is to produce highly capable nanospacecraft, each within a 2-year period, i.e. the time it takes to complete a graduate degree. CanX missions offer extremely low cost and rapid access to space for scientists and commercial exploitation. CanX-2, which is compatible with the Stanford University and California Polytechnic State University “CubeSat” standard, is a “triple CubeSat” with dimensions measuring 10 × 10 × 34 cm and a mass of 3.5 kg. This nanosatellite features an ambitious suite of scientific and engineering payloads, and enlarges the envelope of capability for this class of spacecraft. The primary mission of CanX-2 is to test and demonstrate several enabling technologies for precise formation flying. The secondary purpose of CanX-2 is to fly a number of university experiments. The spacecraft mission, the engineering and scientific payloads, and their implication to planned SFL nanosatellite formation flight missions form the basis for this paper. CanX-2 is currently well within the 2-year design period and fast approaching flight-ready status with launch scheduled for mid 2006.

Normal and oblique hypervelocity impacts on carbon fibre/peek composites

A series of normal and oblique hypervelocity impact tests were performed on carbon fibre/PEEK composite specimens using the Light Gas Gun facilities at the University of Kent at Canterbury. The tests were conducted on 16 ply and 24 ply targets, using 1 mm and 2 mm aluminum projectiles, at velocities of approximately 5 km/s, and at impact angles of 0, 30 and 45 degrees. The primary objective of this investigation was to add oblique impact data to the University of Toronto Institute for Aerospace Studies (UTIAS) database on hypervelocity impact damage to composites. The parameters investigated in this study were debris cloud (primary and secondary) dispersion cone angles, (equivalent) entry and exit crater diameters, and front and rear surface delamination damage zones. The results of the analysis showed that the cone angles were not symmetric about the projectile velocity vector, maxima for both angles occurring at a normalized energy of approximately 55 J, followed by an asymptotic decrease. The results obtained for the entry crater diameter and equivalent entry damage diameter were found to be in good agreement with the existing UTIAS database. For a given impact energy, the damage area in the 24 ply targets was found to be nearly twice that of the damage in the 16 ply targets. Results were found to be in good agreement when compared, using an empirical equation, to predictions of impact damage of Al projectiles on aluminum targets (when a scaling factor of 0.9 was applied to the PEEK data to account for the greater damage in composites).

Atomic oxygen effects on polymer-based materials

This paper describes the operation and performance of an atomic-oxygen (AO) beam facility developed at the University of Toronto Institute for Aerospace Studies (UTIAS), capable of providing ground-state neutral oxygen atoms at ~ 2.2 eV for flux levels as high as ~ 1016 atoms (cm2 s)−1. Results are presented on the AO erosion of polymer thin films and composite materials containing graphite and aramid fibres in epoxy matrices. Comparisons with space flight tests are also given, including studies of samples recently retrieved from the UTIAS composite-materials experiment on the NASA Long Duration Exposure Facility after 70 months exposure in low Earth orbit. Parameters that have been investigated include synergistic effects of UV radiation, surface-morphology changes, and accelerated testing.

Numerical investigation of high-temperature effects in the UTIAS–RPI hypersonic impulse tunnel

The hypersonic impulse tunnel of the University of Toronto Institute for Aerospace Studies (UTIAS) and Ryerson Polytechnical Institute (RPI) is a short-duration blow-down experimental wind tunnel capable of producing high-Mach-number flows (Ma ≈ 8). A generalized quasi-one-dimensional nonstationary flow analysis and associated total-variation-diminishing (TVD) finite-difference solution schemes, including aproximate Riemann solvers, are presented for predicting the high-temperature flows in such facilities. The analysis is used to investigate the operation of the UTIAS–RPI facility and produce performance data that are not always easily determined or available from experimental measurements. The thermodynamic state of the nozzle-exit flow and high-temperature or real-gas effects are assessed for this facility under various operating conditions. Numerical results, coupled with additional comparisons with available experimental data, demonstrate the range of test-section flows that may be achieved. They also illustrate that for typical operating conditions, the air (working gas used in UTIAS–RPI facility) freezes in the nozzle very close to the throat and results in test-section flows with considerable energy bound in the vibrational modes of the nitrogen (N2) and oxygen (O2) molecules. In particular, the test-section temperatures associated with the vibrational modes of N2 are only marginally less than barrel-end stagnation temperatures, whereas the vibrational temperatures of O2, although lower than stagnation temperatures, are still much higher than the predicted translational–rotational temperatures.

A numerical study of oblique shock-wave reflections with experimental comparisons

A direct comparison is made for several occurrences of oblique shock-wave reflections between interferometric results obtained at the University of Toronto Institute for Aerospace Studies (UTIAS) 10 cm x 18 cm hyper­-velocity shock tube and numerical results obtained by using a current computational method for solving the Euler equations. Very good qualitative agreement is obtained for equilibrium and frozen flow fields except in small regions where the experiments were dominated by viscous flow. The quantitative agreement is very close in some cases but can be out by 10–15% in cases with non-equilibrium flow or viscous structures or both. Additional parametrized sequences of calculations are presented to assess the utility of the present numerical method in constructing the various reflection–transition lines for perfect inviscid flows in the shock-wave Mach number, wedge-angle (Ms,θw)-plane, and the validity of the ‘boundary-layer defect’ theory.

Pressures inside a room subjected to simulated sonic booms

The pressure variations inside a room of plaster-wood construction subjected to sonic boom loadings were investigated both analytically and experimentally to study the problems of dynamic structural response. The N-wave pressure signatures were generated in the UTIAS (University of Toronto Institute for Aerospace Studies) Travelling Wave Horn-Type Sonic Boom Simulator. The room overpressures in some cases were found to be twice as great as that in the incident sonic boom. The analysis and experimental data can be useful in assessing structural damage caused by supersonic aircraft overfligths.