Orbital

Question 1

What is the gravitational parameter, μ

Answer 1

Represents the ability of a massive body to exert Newtonian gravitational forces on other bodies.
- For Earth centred systems, this is known as the geocentric gravitational constant
- For sun centres systems, it is the heliocentric gravitational contstant

Question 2

Talk through reaching the moon

Answer 2

1. Launch to orbital height and speed
2. Get into low earth orbit
3. Rocket boost to the required speed and direction for the moon
4. Reverse boost to slow down and enter orbit around the moon
5. Separation of lunar module
6. More reverse power
7. more reverse power to enable descent of lunar module prior to landing
8. Rocket required speed and direction to reach earth
9. Reverse thrust to re enter earth orbit
   10” renter, splash down and pick up

Question 3

What are Impulse manoeuvres

Answer 3

Impulse manoeuvres are the means by which rockets, satellites and other spacecraft are able to change their trajectories and orbital characteristics
Can be used to increase radius of orbit, change its plane, rotate the apse line or change phase.
They typically occur over short period of time and velocity increase, du, assumed to be instantaneous

Question 4

What is burnout velocity

Answer 4

How fast the spacecraft is moving once all the propellants have been burnt (burnout)
This determines whether or not the spacecraft is travelling at sufficient velocity to enter low earth orbit.

Question 5

Explain the Hohmann Transfer

Answer 5

Most energy efficient two-impulse manoeuvre for transferring between two coplanar circular or elliptical orbits sharing common focus.
First impulse Occurs when the spacecraft is at the periapsis, point A, of an initial orbit, orbit 1
This send the spacecraft on the transfer orbit, orbit 2.
When it reaches the apoapsis of orbit 2, point B, a second impulse is required to enter the final orbit, orbit 3.
The convention is for the first impulse to occur at point A and second one at point B.

Question 6

What is a phasing manoeuvre

Answer 6

Type of Hohmann transfer orbit which involves two impulses.,., one to change the orbit and another to return to the same one