lecture 4

Question 1

Why is earth inheriting a mini moon tmeporarily?

Answer 1

slow speed and close proximity makes it be pulled in by earths gravitational pull
- not the first or the last time
- member of the arjuna asteroids

Question 2

What are Apollo Asteroids?

Answer 2

they are asteroids that are constantly crossing earths orbital plane; is idenitcal to earths orbital plane
- can be a threat if over 1km

Question 3

Asteroid characteristics

Answer 3

known as NEO (near earth objects)
- we have asteroid terrestrial impact last alter system (ATLAS) to be constanly looking out for NEO’s
- 3 in each hemisphere, 120 degrees apart

Question 4

What is Comet tsuchinshan-atlas? (comet A3)

characteristics, when it was found

Answer 4

found in jan 2023, will be visible in octover in Southern hemisphere
- its at its perigee
- will likely never see it again

brightness
- cant predict bc of many factors
- closer = brighter
- how reflective (dust or not dust)
- dust = tail of comet; can block light

colour
- green (diatomic carbon)
- material inside nucleus gets heated when approaches sun
- absorbs sunlight and radiates at visible wavelengths

Question 5

how did rockets become developed after WW2?

Answer 5

germans developed the V2 rocket
- engineers who worked on it, when to the USA or soviet union

usa
- worked on development of rocketry to military purposes and space exploration

Question 6

How did Wernher Von Braun impact rocketry development?

Answer 6

worked on rocketry for non military purposes
- jupiter sea, and juno rockets (for satellites)

leading rocket designer for NASA
- research allows rockets to not explode on launch
- architect of saturn-V (most powerful rocket until recently)
- took humanity to the moon in 69

Question 7

How did Theordore von karman impact the space community?

Answer 7

defined were space starts and atmosphere ends
- ~100km amove mean sea level
- karman line; where aerodynapic stops and astronautics start (planes can no longer fly based off principles of aerodynamics)

Question 8

How do planes fly?

Answer 8

how planes fly
- aerodynamic surfaces (wings); allows lift to carry a certain mass
- associated with the altitude the plane is flying, and the speed its flying with
- greater area of wings = greater lift capability

planes and density
- lower in the atmoposher = higher density
- greater lift at a lower altitude
- air density 0 = lift 0
- as the altitude increases, density goes down, the lift you are able to generate begins to diminish
- can offest with more speed only to a certain point
- high enough that the air density is so low you cant achieve a high enough speed

Question 9

What is the lift equation?

Answer 9

lift equation
- the faster the speed, the greater the lift
- the greater the area of your wings, the greater the lift
- the greater the air density, greater the lift
- atmospheric density decreases with altitude

L = 1/2 pv^2 S CL

- L is lift force
- p is air density
- v is aircraft speed
- S is aircraft wing area
- CL is lift coefficient

Question 10

Lift vs. Orbital motion

Answer 10

• increasing altitude = decreasing atmospheric density
  
  • planes cannot fly past a certain point
• if u have a spacecraft flying at 125-150km altitude, you cant stay in orbit for very long; if circular
  
  • air density is almost 0
  • like friction, slow it down
  • further from earth = atmospheric density that slows you down
  • low altitude satellites (200-250km) run into this problem
    
    • they eventually de-orbit because of friction between spacecraft and low density gas in orbit
• elliptical orbits can have perigees closer to 100km for some time
  
  • higher = less friction
• the ISS loses orbit every 3 months; must be rebooted

Question 11

what does it mean by “free molecular flow”

Answer 11

space
- when the atmospheric density is sufficiently low that molecules essentially travel in straight lines with minimal to no collisions (75-80 km above sea level)
- on earth Oxygen and nitrogen dont move far without encountering another molecule
- gas is thick
- density of air is much lower the higher you go;

Question 12

space throughout the world

Answer 12

FAA and USA use 80km to determine when space begins
- international organization uses 100km

astronaut (star sailor)
cosmonauts (russia)
taikonauts (china)

681 people have reached space, 610 people have orbitted space

Question 13

Who is Sir Arthur C. Clarke?

Answer 13

• english science fiction writer
• wrote extensively and positively about the advantages of spaceflight
  
  • golden age of science fiction
• he recognized if you put a satelite high enough the earths surface it would form an orbit that would allow half the planet to be visible at any point in time
• convinced president kennedy to fund a space race in 1960s
• space station flies about 300-400km
• promotted idea for telecommunication in 1945 (clarke orbit)

Question 14

what is: Geostationary and Geosynchronus orbit

Answer 14

Geostationary
- orbits above the equator
- apears stationary, and doesnt move in sky as day progresses
- telecommunication orbit

Geosynchronous
- circular orbit that appear to remain above earth at a constant longitude; drifts north and south
- returns to same point in the sky at same time of day

Question 15

facts about satellites

Answer 15

• as satellites die, it is not incumbent on countries to move them out of orbit
  
  • graveyard orbit so another one can replace it
  • ~42,000km from center of earth
• if you put three, 120 degree separation you would have complete global communication coverage