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Astronomy 4800 – Space Science: Practice & Policy
ASTR 4800 - Space Science: Practice & PolicyToday: Introduction to Outer Space
• Next Class: Visit with ISS astronaut Dr. Sandra Magus. Read bio at: https://www.aiaa.org/SandyMagnusBio/.
• Reading for next Monday: Chapters 2-5 in McDougall.
• Homework #1 – due on Friday, Feb. 3.
Astronomy 4800 – Space Science: Practice & Policy
Space in the News: NASA Selects Two Missions to Explore the Early Solar System
(Left): An artist’s conception of the Lucy spacecraft flying by the Trojan Eurybates – one of the six diverse and
scientifically important Trojans to be studied. Trojans are fossils of planet formation and so will supply important
clues to the earliest history of the solar system. (Right): Psyche, the first mission to the metal world 16 Psyche
will map features, structure, composition, and magnetic field, and examine a landscape unlike anything
explored before.
Presenter: Chris Davidoff
Astronomy 4800 – Space Science: Practice & Policy
Introduction to Outer Space
Explanatory Statement Preparedby President Eisenhower’s
Science Advisory CommitteeJames Killian, Chair & President’s Science Advisor
March 26, 1958
Astronomy 4800 – Space Science: Practice & Policy
Reasons for a Space Program?
• Compelling urge to explore and to discover (Edmund Hillary).
• Development of space technology for defense (ICBMs, satellite spying).
• National prestige (create confidence of other nations in U.S. technology).
• Scientific observations and experiments enhancing knowledge of Earth, solar system, & universe.
Have any of these reasons changed today?
Astronomy 4800 – Space Science: Practice & Policy
Reasons for a Space Program Today?
• Evidence for extraterrestrial life
• Survival – time limited on Earth
• Gather resources
• Exploration – part of being human
• To find out about our origins – water
• National defense
• Economics
• Creating high paying technical
• Communications across the planet.
Astronomy 4800 – Space Science: Practice & Policy
The physical principles governing spaceflight: Newton’s three laws of motion
Newton’s first law of motion: An object moves at constant velocity unless a net force acts to change its speed or direction.
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Astronomy 4800 – Space Science: Practice & Policy
Newton’s second law of motion
Force = mass acceleration = ma
Astronomy 4800 – Space Science: Practice & Policy
Newton’s third law of motion
For every force, there is always an equal and opposite reaction force.
Astronomy 4800 – Space Science: Practice & Policy
What determines the strength of gravity?
The Universal Law of Gravitation:1. Every mass attracts every other mass.2. Attraction is directly proportional to the product
of their masses.3. Attraction is inversely proportional to the square
of the distance between their centers.
Astronomy 4800 – Space Science: Practice & Policy
How is Newton’s concept of Gravity different from Einstein’s?
Astronomy 4800 – Space Science: Practice & Policy
Why satellites stay up
• F = ma, F = force, m = mass, a = acceleration.
• For gravity, F = GMEMS/R2.
• a = v2 / R, where v = orbital velocity.
=> V = [GME/R]1/2
Question:
What orbital velocity is needed to sustain a satellite in low Earth orbit? What about geosynchronous orbit?
R
ME
MS
This tells us what thrust and enginecapability our rockets must have!
Astronomy 4800 – Space Science: Practice & Policy
What science can be done fromspace with a satellite (in 1958)?
• Sample strange new environment (van Allen radiation belts, space weather, General Relativity experiments).
• Look down on the Earth (remote sensing, weather forecasting).
• Look out into the Universe (X-rays, ultraviolet, infrared, long wavelength radio).
Still true today!