Overview of Astronautics and Space Missions Prof. Richard Wirz Slide 1
Astronautics Definition: The science and technology of space flight Includes: Orbital Mechanics Often considered a subset of Celestial Mechanics Orbital Maneuvering Propulsion Spacecraft Attitude Control and Dynamics Slide 2
Anatomy of a Space Mission Mission design/planning Spacecraft (s/c) design/production Launch Post-launch maneuvers Orbit/Interplanetary Transfer LEO, MEO, and GEO Deployment Mission Note: Sequence of events See Applications on later slides depends on mission type Vehicle return, disposal, end-of-life Slide 3
VVEJGA (Venus-Venus-Earth-Jupiter Gravity Assist) trajectory Slide 4
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Applications of Astronautics Communications XM Satellite Earth Observation Space Observation Exploration Other Slide 6
ESA SMART-1 Lunar Mission Pi Primary Propulsion: li PPS-1350 Hall thruster Discharge Power: 0.46-1.19 kw Specific Impulse: 1100-1600 s Thrust: 30-70 mn First use of Hall thruster electric propulsion outside of Geosynchronous Orbit. Used SEP spiral orbit transfer Image: ESA In 2005, SMART-1 exhausted its xenon supply after flawlessly operating the thruster. Thruster operating time: 5000 h Xenon throughput: 82 kg Total Impulse: 1.1 MN-s Total V: 3.9 km/s PPS-1350 has established new records for Hall thruster operation in space Slide 7
Disciplines/Related Fields Celestial/Orbital Mechanics Space Mission Analysis and Design Spacecraft Control Propulsion Slide 8
Current Research Low thrust trajectories Lunar Obit Orbit Formation flying Moon High precision ecso orbits Earth Departure Earth Lunar Arrival Many other areas MAPS is Capable of Robustly Optimizing Multi-Spiral, Low-Thrust, Inter-Body Trajectories Such as This Low-Thrust, Earth-Orbit to Lunar Polar Orbit (LPO) Example Mission Scenario Slide 9
Brief History of Celestial Mechanics Slide 10
Ancient Times Aristarchus [300 BC] developed theory of fixed sun and stars with Earth revolving around sun in circular orbit Unpopular with philosophy of the time Apollonius and Hipparchus [~130 BC] introduced the epicyclical motion of the planets Ptolemy [150 AD] further developed this theory using about 80 epicycles assuming Earth-centered (Geocentric) Highly accurate and lasted for 1400 years Slide 11
The Scientific Revolution (1473-1543) Nicholas Copernicus published Revolution of Celestial Bodies (1546-1601) Tycho Brahe was a painstaking observer and recorder of the motions of the planets (without a telescope...). I've studied all available charts of the planets and stars and none of them match the others. There are just as many measurements and methods as there are astronomers and all of them disagree. What's needed is a long term project with the aim of mapping the heavens conducted from a single location over a period of several years. Tycho Brahe, 1563 (age 17). (1564-1642) Galileo Galilei used the telescope to observe the motion of Jupiter s four moons. He favored the Copernican heliocentric theory. These observations of Jupiter s moons lead to the general acceptance of the Copernican heliocentric theory Slide 12
Johannes Kepler (1571-1630) Johannes Kepler spent six years analyzing Tycho Brahe s 13 years of observations of Mars. He struggled for almost a year to explain a discrepancy of only 8 minutes of arc before he came upon the elegant solution, an ellipse. Kepler [1571-1630] used Tycho s observations to derive three laws: First law: Every planet moves in an orbit that is an ellipse, with the sun at one focus of the ellipse. Second law: The radius vector drawn from the sun to any planet sweeps out equal areas in equal times. Third Law [1619]: The squares of the periods of revolution of the planets are proportional to the cubes of the semi-major axes of their orbits And then came Newton, to provide the theory Slide 13
Issac Newton The venerable Isaac Newton [1643-1727] laid the foundation for much of modern science: including calculus, optics, dynamics, and orbital motion His three laws of dynamics were published in 1687 in Philosophiae Naturalis Principia Mathematica: First law: Every body continues in its state of rest or of uniform motion in a straight line unless it is compelled to change that state by forces impressed upon it. Second law: The rate of change of momentum is proportional to the force impressed and is in the same direction as that force. d F p, where p = mv dt Third law: To every action there is always opposed an equal reaction. Slide 14
Universal Law of Gravitation In Principia Mathematica, Newton also enunciated Universal Law of Gravitation: Two bodies attract each other with a force proportional to the product of their masses and inversely proportional to the square of the distance between them along the line joining the bodies. G GMm F 2 r (6.6726 0.0005) 10 11 3 m kg s 2 In the following lectures we will show how the vector forms of Newton s laws explain Kepler s Laws (and hence, Tycho s observations) Slide 15