Launch Vehicles and Orbits

How Rockets WorkNewton's Laws of Motion are: An object at rest tends to remain at rest An object in motion tends to remain in motion For every action there is an equal and opposite reaction

Conservation of MomentumNewton's Laws are all contained in a more general principle called conservation of momentum. Momentum is mass times velocityIn a system that is not disturbed from outside, the total momentum stays constant.

Conservation of Momentum Means:If velocity is zero, momentum is zero (Newton's First Law) If velocity is not zero, and mass doesn't change, then velocity doesn't change (Newton's Second Law)

Conservation of Momentum and Newtons Third LawIf mass changes somehow, then so does velocity. If an object is stationary, and flings off mass, the rest of the mass moves in the opposite direction. The flung off mass has positive momentum, the rest has negative momentum, and the total momentum remains zero (Newton's Third Law).

Conservation of Momentum

Rockets and JetsRockets and jets work according to Newton's Third Law. They fire mass out at high speed and acquire velocity in the opposite direction. They do not need something to push against. They move because they are expelling exhaust gases at high speeds. Tthe rocket or jet is pushing mass away, and the mass is pushing back (equal and opposite reaction.)

How Rockets and Jets DifferRockets and jets expel mass by burning fuel.A jet gets the oxygen for combustion from the atmosphereA rocket carries oxygen in some form with it. Thus rockets can function outside the Earth's atmosphere; jets can't.

Rockets are Mostly Fuel (and Oxygen)A rocket or jet has to carry all its remaining fuel with it. (And oxygen, if its a rocket).Most of the mass of the Space Shuttle is fuel, and most of that is used to get the remaining fuel off the ground. The miles-per-gallon fuel economy of the Space Shuttle in its first foot off the ground is pretty terrible!

About Orbits and SatellitesSatellites travel elliptical paths with the center of the Earth at one focus (Kepler's First Law)Inertia causes object to continue moving in a straight lineGravity pulls object to EarthBalance between the two = orbit

Newtons Mountain

Important OrbitsLow vs. High InclinationAlmost all are ProgradePolar Orbits for global coverageCircular Orbits strongly preferredConstant altitudeConstant speedSun-SynchronousGeosynchronous12-Hour (GPS)

About OrbitsYou do not need to expend fuel to stay in orbitSatellites need attitude control fuel to correct for atmospheric drag, lunar and solar gravity, etc.May want thrusters to help maintain orbitsSpin stabilization helpsOnce below 200 km, atmospheric braking leads to re-entry

About OrbitsThe focus of a satellite orbit is the center of the earthThe plane of a satellite orbit always passes through the center of the earthThere is no such thing as an orbit over the poles, over a small region, etc.It is possible to have an orbit over the equator

PrecessionPut sideways force on anything moving in a circle, it will precessPrecession affects planetary rotationPrecession also affects orbitsWe can control precession of satellites by selecting orbital inclinationFixed with respect to starsFixed with respect to sun

Precession

Precession

Precession

Three Pioneers of RocketryKonstantin Tsiolkovsky (1857-1935)Worked out theoretical problems of spaceflightRobert Goddard (1882-1945)First Liquid Fuel RocketHermann Oberth (1894-1989)Helped create operational rockets

Robert Goddard -First Liquid-Fuel Rocket, 1926

The V-1

The V-2

From Sapwood to SputnikAn existing rocket, the SS-6, was used.The warhead section was removedA cluster of four more SS-6 engines was bolted around a central engineVery Dependable

Sputnik IOctober 4, 1957S- (with) + put (path) + -nik (one who) = SputnikLiterally, one who follows the same path

Early Rockets, Kennedy Space Center

Early Rockets, Huntsville AL

V-2 Huntsville AL

V-2 shrapnel

V-2 Components

Gemini, 1965

Sensor TechnologyPassive (senses only ambient signals)Active (emits signals)

ImagingNon-Imaging

Scanning (mechanical or electronic)Non-scanning

The Single Most Valuable Product of the Space Program

Crescent Earth

Himalayas from Space Shuttle

Volcano, Alaska

Fringing Reefs

Icebergs, Antarctica

A Noble MythIn my life, I've seen the images from space of a blue-white-green world there are no political lines drawn on this planet. Luis J. Rodriguez

The border between the United States and Mexico is an imaginary line. It cannot be seen from spaceThe Border Zone: A History of Trade between the United States and Mexico, Julia Albright; Age of Irony, Winter 2004

You Cant See Borders From Space

Mexican Border

Mexican Border

Menominee County, WI

U.S.-Canadian Border

Landsat View of Green Bay

Landsat View of Green Bay

Landsat view of Washington D.C.

Radar Image of New York City

Spy Satellite Views of Soviet Aircraft Carrier

Spy Satellite View of Soviet Airfield

World Trade Center, September 11, 2001

Pope John Paul II Funeral

Pope John Paul II Funeral

Barack Obamas Inauguration

Barack Obamas Inauguration

And Now For Something Completely Different.

Gulf Stream in Infrared

Ultraviolet View of Earth

The Ocean Floor From Space

Earth and Moon Together

Really Remote Sensing

An Eclipse of the Sun By Earth

*Sudan Chemical Plant*Afghan Terrorist Camp