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