Basic spacecraft concepts

Question 1

Definition of spacecraft

Answer 1

Vehicle or machines designed to fly in outerspace

Question 2

Definition of sub-orbital

Answer 2

enters space and then returns to the surface of the Earth - without going into permanent orbit

Question 3

Definition of orbital

Answer 3

enters closed orbit (permanent) around Earth or other celestial body (moon)

Question 4

Definition of interplanetary

Answer 4

travel between planets

Question 5

Definition of interstallar

Answer 5

leave solar system

Question 6

At what point is it considered spaceflight

Answer 6

Consider L = 0.5pSV^2Cl
as altitude increase, p decreases, therefore speed increases
when this speed = orbital speed the object stays in orbit which is considered spaceflight

Question 7

What distance from Earth is considered space flight and what is this boundary called

Answer 7

100km above the surface

called the Karman line

Question 8

Name the key stages of a complete space mission

Answer 8

• Pre-launch phase
• Launch phase
• Orbit transfer
• On-station operations
• Decommisioning

Question 9

What happens during pre-launch phase

Answer 9

ignition, separation from ground launch facilities

Question 10

What happens during launch phase

Answer 10

placing spacecraft into an intermediate orbit

Question 11

What happens during orbit transfer

Answer 11

transferring the spacecraft to its operational orbit

Question 12

What happens during on-station operations

Answer 12

mission itself, station keeping, attitude control

Question 13

What happens during decommisiong

Answer 13

place spacecraft into a higher orbit or controlled re-entry

Question 14

What is a launch window and how long is it

Answer 14

the limited time interval available for a launch.

Typically few minutes each day. However gets much smaller when trying to rendezvous with ISS or reach another planet

Question 15

What is Low Earth Orbit (LEO)

Answer 15

• Altitude is 160-2000km
• orbit period about 88-127 minutes
• spacecraft moves with respect to Earth’s surface
• simplest and cheapest, high bandwidth and low communication delay
• see Earth’s surface more clearly
• most statellites and ISS are in LEO

Question 16

What is Geostationary Earth Orbit (GEO)

Answer 16

• Altitude is 35,786km above equator
• Orbital period is 24hrs, therefore at a fixed position with respect to Earth’s surface
• used for communication and weather satellites
• high cost, communication delay of 0.25seconds

Question 17

How do chemical rockets change momentum

Answer 17

by discharging hot products of combustion at very high velocities
high power but limited energy

Question 18

How does electrical propulsion work and why is it useful

Answer 18

by electrically heating or charging particals to increase kinetic energy
useful as it is not energy limited and so used for station keeping and interplanetary missions

Question 19

Rocket equation

Answer 19

ΔV = Vex . ln(Mo/M1)

where:
ΔV = change in velocity
Vex = exhaust velocity
Mo = initial mass of rocket inc. fuel
M1 = final mass after fuel burn

Question 20

Calculating mass of the propellant (fuel)

Answer 20

Mprop = Mo - M1

Mprop = Mo(1 - e^-(ΔV/Vex))