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Spaceflight I

Spaceflight I. Leaving Earth. 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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Spaceflight I

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  1. Spaceflight I Leaving Earth

  2. 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

  3. 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.

  4. 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)

  5. 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).

  6. Newton’s Third Law

  7. 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.)

  8. 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.

  9. 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!

  10. 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

  11. Newton’s Mountain

  12. Three Pioneers of Rocketry • Konstantin Tsiolkovsky (1857-1935) • Robert Goddard (1882-1945) • Hermann Oberth

  13. Robert Goddard -First Liquid-Fuel Rocket, 1926

  14. World War II

  15. The V-1

  16. V-1

  17. Japanese Okha

  18. The Very First Cruise Missile

  19. The V-2

  20. V-2

  21. History That Might Have Been: • If World War II had lasted a bit longer, it might have been fought with: • Nuclear Weapons • Guided Missiles • Cruise Missiles • Jet Aircraft

  22. The Right Stuff • Chuck Yeager - Supersonic Flight, 1948 • Career fatality rate among military jet pilots is 25% • To cope, they cultivate a superstition of “the right stuff” • Title of Tom Wolfe book

  23. 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

  24. Sputnik I • October 4, 1957 • S- (with) + put’ (path) +-nik (one who) =Sputnik • Literally, one who follows the same path

  25. Sputnik II and III

  26. How Did Russia Beat the U.S? • German scientists were not involved • German scientists were not involved • German scientists were NOT involved!! • Germans built V-2 clones but did not work on main program • All returned home by the early 1950’s • They were debriefed on return - this has been known for decades

  27. So why does the myth persist? Because it’s what we wanted to believe

  28. Rockets and Geopolitics • We relied on manned bombers • We had bases close to Russia • We led in miniaturization • We decided to wait until nuclear weapons became smaller before putting them in missiles • Result, we had smaller rockets • And, most surprising of all---

  29. Much of our early efforts went into cruise missiles!

  30. How the World Looked to Russians in the 1950’s

  31. The Russian Decision • They had no bomber bases from which to attack the U.S. • Missile Submarines were rudimentary at the time • The only way to hit the U.S. was with missiles • Thus, the Russians poured efforts into building huge rockets

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