Orbital Mechanics &
Other Fun StuffPart I Basic Orbital Mechanics
Tom RudmanThursday Morning
Space Odyssey Crew
Discussion Topics
• Basic Earth Orbits (Part I)• Traveling to Mars (Part I)• Going Beyond Mars (Part II)• Relativity Effects (Part II)
Earth and Moon as Seen from Mars by MRO HiRISE cameraImage Credit: NASA/JPL-Caltech/University of Arizona
How do Rockets Get into Space?• Isaac Newton showed if you can
achieve a sufficient velocity you will go into orbit around Earth– The orbital velocity balances the
acceleration due to gravity– It is all about Velocity
• The velocity comes from the rocket engine firing– Earth Orbit, 18,000 mph– Escape Earth, 25,000 mph
• Earth orbit is not “Zero-Gravity ” you are in FREE-FALL– There is gravity in orbit - it is what
is holding you in Orbit– You are always being pulled
towards the Earth
Isaac Newton’s Cannon
PERIAPSIS
APOAPSIS
Pictures NASA JPL
Ballistic
Geosynchronous Equatorial Orbit, (GEO)• Most Popular Orbit for Satellites
– Inclination is 0º or around the equator– Launch site latitude determines orbit plane change– Kennedy Space Center is at 28º– Baikonur (Russia ) is at 60º– Ariane launch site in French Guiana is near the equator
• The spacecraft stays over the same spot on earth– If you have satellite TV, that is where the satellite is located.– Weather Satellites are sometimes in this orbit (GOES), – All types of communications, broad band, pagers, etc
• Proposed by Arthur C. Clark for communications, 1945 – 1st Described in 1928, “The Problem of Space Travel - The
Rocket Motor”, Dr. Herman Potočnik (Austrian Rocket Engineer) for a Space Station
Source: Wikipedia.orgSuper Dish 121
Arthur C. ClarkDr. Herman Potočnik
Other Earth Orbits• GPS orbit 12,550 mi (20,200 km),12 hr circular, 24 satellites (USAF)
• Sun Synchronous (polar) Orbit–Earth weather & resources satellites - constant solar conditions–Altitude typically 600 - 1000 km, ~98 deg –NOAA weather satellites use this orbit
GPS block II, NASA & USAF
GPS block INo longer used
Source: wikipedia.org
Earth-Mars Transfer
Mars at Spacecraft Arrival
Mars at Spacecraft Departure
• A (nearly) Hohmann transfer to Mars
““To Orbit and Spacecraft Systems Engineering” To Orbit and Spacecraft Systems Engineering” Scott Schoneman Arizona State University Nov 2003Scott Schoneman Arizona State University Nov 2003
Phoenix
Viking
Mars 3 Orbiter
Mars Curiosity
Phobos
NASA Photo
Spacecraft Transfer Orbit