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Launch Vehicles and Sensing Technology

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Launch Vehicles and Sensing Technology. How Rockets Work. Newton'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 Momentum.

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### Launch Vehicles and Sensing Technology

How Rockets Work
• Newton'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 Momentum
• Newton's Laws are all contained in a more general principle called conservation of momentum.
• Momentum is mass times velocity
• In 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 Newton’s Third Law
• If 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).
Rockets and Jets
• Rockets 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 Differ
• Rockets and jets expel mass by burning fuel.
• A jet gets the oxygen for combustion from the atmosphere
• A 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 it’s 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 Satellites
• Satellites 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 line
• Gravity pulls object to Earth
• Balance between the two = orbit
Important Orbits
• Low vs. High Inclination
• Almost all are Prograde
• Polar Orbits for global coverage
• Circular Orbits strongly preferred
• Constant altitude
• Constant speed
• Sun-Synchronous
• Geosynchronous
About Orbits
• You do not need to expend fuel to stay in orbit
• Satellites need attitude control fuel to correct for atmospheric drag, lunar and solar gravity, etc.
• May want thrusters to help maintain orbits
• Spin stabilization helps
• Once below 200 km, atmospheric braking leads to re-entry
Three Pioneers of Rocketry
• Konstantin Tsiolkovsky (1857-1935)
• Worked out theoretical problems of spaceflight
• Robert Goddard (1882-1945)
• First Liquid Fuel Rocket
• Hermann Oberth (1894-1989)
• Helped create operational rockets
From Sapwood to Sputnik
• An existing rocket, the SS-6, was used.
• The warhead section was removed
• A cluster of four more SS-6 engines was bolted around a central engine
• Very Dependable
Sputnik I
• October 4, 1957
• S- (with) + put’ (path) +-nik (one who) =Sputnik
• Literally, one who follows the same path
Sensor Technology
• Passive (senses only ambient signals)
• Active (emits signals)
• Imaging
• Non-Imaging
• Scanning (mechanical or electronic)
• Non-scanning
A Noble Myth

“In 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 space”

• The Border Zone:A History of Trade between the United States and Mexico, Julia Albright; Age of Irony, Winter 2004