Propulsion

Question 1

List three types of spacecraft

Answer 1

1. Earth orbiters
2. Planetary explorers
3. Manned spacecraft

Question 2

List types of spacecraft that are labelled as ‘Earth orbiters’

Answer 2

• comsats
• weather
• earth’s observers
• navigation
• astronomy / space physics
• military

Question 3

List types of spacecraft that are labelled as ‘Planetary explores’

Answer 3

• fly-bys
• probes
• orbiters
• landers/rovers

Question 4

List types of spacecraft that are labelled as ‘Manned’

Answer 4

• orbiters
• lunar landers
• stations

Question 5

Give 3 main methods of producing propulsion in space

Answer 5

1. Photon
2. Rocket
3. Solar sails

Question 6

Give 4 types of rocket propulsion

Answer 6

1. Thermal
2. Cold gas
3. Electric
4. Nuclear

Question 7

Give 2 types of thermal rocket propulsion

Answer 7

1. Chemical

2. Solar

Question 8

Give 3 types of chemical thermal rocket propulsion

Answer 8

1. Solid
2. Liquid
3. Hybrid

Question 9

Give 4 types of electrical rocket propulsion

Answer 9

1. Electrothermal
2. Electrostatic
3. Lorentz
4. Hall

Question 10

Describe photon propulsion

Answer 10

• laser power beam can provide momentum directly to spacecraft
• heating air below aircraft cause it to expand and generate lift
• has to be a light aircraft

Question 11

what is the spacecraft requirement to be able to use photon propulsion

Answer 11

needs to be light

Question 12

Describe solar sails propulsion

Answer 12

• large sheets of thin film, one side of which is covered by reflective coating which reflects solar radiation
• the reflecting photons pass on their momentum to spacecraft
• only theoretical designs at present

Question 13

What is the difference between aircraft Jet engine and liquid rocket engine

Answer 13

jet:

• uses oxygen in the atmosphere
• cannot be used in space

rocket

• oxidiser is carried by the rocket
• operates in and out of space

Question 14

Give rocket equation

Answer 14

Vmax = Vr x ln( M / (M - Mb)) + Vo

Question 15

What is the specific impulse

Answer 15

ratio of the thrust to the weight flow rate of propellant

Isp = Vr / g

Question 16

Describe cold gas rocket propulsion

Answer 16

• just a controlled pressurised gas source and a nozzle

- simplest form of rocket propulsion

Question 17

Describe solar thermal rocket propulsion

Answer 17

• solar energy can either be used directly or via solar cells that convert to electrical current

Question 18

Describe chemical rocket propulsion

Answer 18

• most common for space applications

- propellant can be solid, liquid or hybrid

Question 19

What are the advantages of using solid chemical rocket propulsion

Answer 19

• simplicity
• reliability
• launch time

Question 20

What are the advantages of using liquid chemical rocket propulsion

Answer 20

• controllability
• throttling ability
• restart ability

Question 21

What are the advantages of using hybrid chemical rocket propulsion

Answer 21

• safety
• controllability
• throttling ability
• restart
• environmentally cleaner

Question 22

Describe electrothermal electrical propulsion

Answer 22

• resistojet is the simplest

- propellant is heated by passing over tungsten heating element

Question 23

Describe electrostatic electrical propulsion

Answer 23

• take thrust from accelerating positive charged particles in a static electric field
• need to ensure stream of particles is neutralised so that charge doesn’t build up

Question 24

Describe Halls/Lorentz electrical propulsion

Answer 24

Halls / Lorentz force are used instead of an electrostatic field

Question 25

Describe nuclear propulsion

Answer 25

• solid phase reactor
• gaseous phase reactor
• nuclear charges

Question 26

Why are multistage rockets used

Answer 26

to get rid of unnecessary weight and so increase speed of rocket for same amount of fuel