New Deck Flashcards
Types of conic sections
Circle, Ellipse, Parabola, Hyperbola
What is Eccentricity?
Distance between foci / Major Axis; between 0 and 1; 0 indicates a circle
What is the Semi-major axis?
1/2 the Major Axis and is the satellite’s mean distance from its primary
Eccentricity, Semi-ajor Axis, Energy of: Circle
0, = radius, <0
Eccentricity, Semi-ajor Axis, Energy of: Ellipse
0<e>0, <0</e>
Eccentricity, Semi-ajor Axis, Energy of: Parabola
1, infinity, 0
Eccentricity, Semi-ajor Axis, Energy of: Hyperbola
>1, <0, >0
What are the six orbital elements?
Semi-major axis, eccentricity, inclination, argument of periapsis, time of periapsis passage, longitude of ascending node
What is inclination?
The angular distance between periapsis and the equatorial plane
What is the convention with inclination?
0 is above the equator and prograde, 90 is polar, and 180 is retrograde
What is periapsis?
The closest point in the orbit to the primary
What is apoapsis?
The point in the orbit farthest from the primary
What is the argument of periapsis?
The angular distance between the ascending node and periapsis
What is the ascending node?
The point at which the orbit crosses the equator in a south to north direction
What is the descending node?
The point at which the orbit crosses the equator in a north to south direction
What is the longitude of the ascending node?
This is the angular distance between the ascending node and a reference point (the vernal equinox)
What is the true anomaly?
The satellites angular distance past periapsis
Describe this orbit
Geosynchronous (GEO)
Circular orbits with 24 hr period; ideal for communication of meteorological satellites
Describe this orbit
Polar (PO)
Inclination of 90; ideal for mapping because as the earth orbits underneath the satellite has access to all locations on the surface
Describe this orbit
Geostationary
Geosynchronous with an inclination of 0 so the satellites hovers above a point on the ground
Describe this orbit
Walking
An orbit that takes advantage of other gravitational forces to precess
Describe this orbit
Sun synchronous (SSO)
Walking orbits whose plane precesses with the same period as the planets solar orbit period. Thus the satellite crosses periapsis at the same local time every orbit
Describe this orbit
Molniya
Highly eccentric with period of about 12 hrs. Orbital inclination chosen so that the rate of change of the perigee is 0, so apogee and perigee can be maintained over fixed latitudes.
Describe this orbit
Hohmann transfer
Interplanetary trajectories that consume the least amount of propellant. To get to an outer planet, the spacecraft accelerates to a speed that places it into a heliocentric orbit with a aphelion equal to its targets. When it arrives it decelerates to be captured by the planet’s gravity. It is timed so that it arrives at its target planets orbital distance just as the planet itself arrives.
How does g vary with altitude?
g = GM/r^2
What is mu
The constant, GM
