Rocket Science, Reentry and the Race to Mars. From Science Fiction to Simulation

Transcription

1 Rocket Science, Reentry and the Race to Mars From Science Fiction to Simulation Julian Köllermeier RWTH Aachen, November 1st 2015

2 The Mars half the diameter of the Earth 40% of Earth s gravity 2 moons (Phobos and Deimos) 1 year = 687 (Earth) days 1 sol = 24 h 40 min

3 Race to Mars A short history of Mars exploration 1960 Mars M1 first start to Mars 1965 Mariner 4 first flyby 1971 Mariner 9 first orbiter 1971 Mars 3 first soft landing 1997 Pathfinder first rover Currently 7 active missions

4 Mars rovers Pathfinder (1997) 10,6 kg 7 sols Opportunity, Spirit (2003) 174 kg (2695) sols Curiosity (2012) 900 kg sols

5 Mars landings Phoenix 2008 Pathfinder 1997 Beagle Opportunity 2004 Curiosity 2012 Spirit 2004

6 Mars atmosphere Weather Durst storms Seasons Water clouds Very thin atmosphere 0.6% of Earth's pressure Equal to Earth s pressure at 35 km 95% CO 2, 2% Ar, 2% N 2 Reason for thin atmosphere Low gravity No magnetic protection Solar winds

7 Atmospheric reentry Atmospheric entry is the movement of human-made objects as they enter the atmosphere of a celestial body from outer space. Object can be: Spacecraft Space capsule Space ship Satellite Intercontinental ballistic missile

8 Mars reentry

9 Some hard facts about reentry Reentry starts at Karman line Earth 100km Mars 80km Velocity of reentry vehicle Low Earth orbit 7.8 km/s Mars return 14km/s Surface temperature more than 1000K Energy exchange between kinetic energy and thermal energy Mars landing is not possible above 2km ground level Further Mars missions require advanced technologies Reentry vehicle and Heat shield

10 Experiment vs simulation Development and optimization needs testing: In-flight measurements Wind tunnel experiments Numerical simulations Problems of experiments: Small parameter range Limited measurement capabilities Expensive Benefits of simulations: Variable conditions Detailed measurements possible Repeatable

11 Numerical simulations 1. Develop mathematical model and implement numerical solution method 2. Set up test case and run computer program on big machines 3. Get simulation results

12 Mathematical models for rarefied gases Rarefied flow characterized by large Knudsen number: Kn = λ L λ: mean free path length of molecules L: characteristic length of system Applications for large Knudsen numbers: Large λ: reentry flights, hypersonic flows Small L: microchannels, microelectromechanical systems

13 Solution methods Stochastic method: Direct Simulation Monte-Carlo (DSMC) Single particles that collide and move through space Needs many particles Stochastic noise in results Deterministic methods: Moment methods Derive equations for most important flow variables (density, velocity, temperature, heat flux) Extension of standard fluid dynamics

14 PhD topic A New Approach for the Approximation of Kinetic Equations - Stable Projections and High-Resolution Numerics of Real Applications Milestones: Derivation of new equation systems Investigation of analytical properties Development and implementation of numerical solution methods Simulation of test cases and comparison with different methods Goal: Simulation of real application problems Thank you for your attention!