Rockets

Question 1

Give 2 historical case studies in module

Answer 1

1. German V-2

2. Soviet R7

Question 2

Describe characteristics about German V-2 rocket

Answer 2

• first rocket to reach outside sensible atmosphere (80km)
• pumps were driven by steam turbine (steam produced by concentrated hydrogen peroxide with sodium permanganate catalyst)
• Very sharp tip which cause overheating because oblique shock wave
• first to use regenerative cooling
• used water in fuel (saved refinery cost and reduced combustion temp)

Question 3

How was unstable combustion and destructive vibration overcome in German V-2 rocket

Answer 3

• clustered 18 smaller combustion chambers to fire into a single large chamber
• made rocket very heavy and difficult to cool
• used regenerative cooling technique

Question 4

Describe engine config. of soviet R7

Answer 4

• 4 break-away liquid-fuelled engines surround a central core
• core acts like a ‘second stage’
• Pressure and Temp much higher than V2 rocket

Question 5

What fuel did Soviet R7 rocket use

Answer 5

kerosene and liquid oxygen

• meant much higher temperatures!

Question 6

How does regenerative cooling system work on Soviet R7 engine

Answer 6

• between thin inner wall and steel outer wall was corrugated steel sheets
• this helped structure and allowed for cooling fuel to flow past
• layers joined by brazing with silver solder

Question 7

Give heat flux equation to calculate heat between inner and outer walls

Answer 7

Q = heat flux = k (Twg - Twl) / L

Question 8

Why does Elon Musk use stainless steel for re-entry vehicle

Answer 8

• much stronger and not brittle at cryogenic temp

- much cheaper than carbon fibre

Question 9

Why was R7 rocket so innovative

Answer 9

Had the capability to use variable mixture ratio between fuel and oxidiser

Question 10

Describe Soyuz rocket

Answer 10

• direct descendant of R7 rocket
• world’s most used space launcher
• low cost
• highly reliable
• 20 times cheaper than space shuttle launch

Question 11

General issue with rocket propellants

Answer 11

Propellants of toxic so launch sites are not ideal

Question 12

Describe Titan rocket family

Answer 12

• USA
• Famous for manned mission
• phased out due to toxic propellant and high cost
• used aerozine 50

Question 13

Describe Atlas rocket family

Answer 13

• USA but used russian RD180 engine

- uses oxygen rich staged cycle

Question 14

How must RP-1 fuel be burned

Answer 14

Needs to be ORSC, not FRSC

Oxygen rich staged combustion

Question 15

Describe Delta rocket family

Answer 15

• still flying
• used RS68 engine
• used gas generator cycle t lower cost
• modified from space shuttle RS25
• operates at lower pressure
• Russian regenerative cooling applied

Question 16

Describe Falcon rocket family

Answer 16

• SpaceX Falcon
• brought about many innovations
• sub-cooling of propellants for densification
• cavitation reduction in the pump
• use small but many engines to reduce cost and increase stability
• partial re-use is a goal

Question 17

What is cavitation in a pump

Answer 17

cavitation is the formation of bubbles or cavities in liquid, developed in areas of relatively low pressure around an impeller.

Question 18

Describe Chinese Long March rockets

Answer 18

• hypergolic propellants used for long stability at ambient temp
• launch sites not idea in mainland
• used to send astronauts to space

Question 19

Describe European rockets

Answer 19

• Ariane 5 - 2 solid stage, main liquid hydrogen and oxygen

Question 20

How does size affect a rocket

Answer 20

• impacts capability, applicability and cost

Question 21

How does launch site impact rocket

Answer 21

• impacts payload
• effects orbit inclination
• at the equator, planet spins faster, also reason why rockets launched west to east

Question 22

Give 3 advantages of equatorial launch

Answer 22

1. Rotational speed of earth is greatest
2. The need for a ‘plane change’ to the 0 degree inclination of geostationary orbit is eliminated
3. Allows for bigger payload

Question 23

Give 2 advantages of ocean launch

Answer 23

1. Reduced risk of launching over populated areas

2. Absence of range conflicts with other launch systems (near total absence of ship/air traffic)

Question 24

List 5 concerns with human cargo:

Answer 24

1. Need to accommodate for human needs
2. Sufficient uncertainty
3. Capability of recovering crew
4. Higher redundancy requirement
5. Lower combustion chamber pressure

Question 25

What are the 4 components of LES - Launch escape system

Answer 25

1 - launch abort system 2 - crew module 3 - service module 4 - spacecraft adapter

Question 26

What are the differences between space shuttle and Buran rocket

Answer 26

- space shuttle main engines are with the shuttle - buran rocket did not have main engines so it is counted as 'payload' - therefore buran can have more payload but main engines are not recoverable

Question 27

Describe Saturn rocket family

Answer 27

- used for all Apollo missions - 2nd largest liquid engine - largest nozzle (creates instability issues) - Used F1 engine in first stage of rocket (this had +- 35 bar pressure fluctuations - very high!)

Question 28

Describe N1 rocket

Answer 28

- rocket soviets used in space race | - used ORSC with all oxygen flowing through pre-burner

Question 29

Describe Space X raptor engine

Answer 29

- full-flow staged combustion - eliminates the fuel-oxidiser turbine interseal - lower pressure required in pumps - can increase combustion chamber pressure

Question 30

List 5 advantages of using liquified methane

Answer 30

1. Better specific impulse 2. Better cooling capabilities 3. No/Less solid residue in pipe (compared to kerosene) 4. No need for extra infrastructure and cheaper 5. Can be produced on Mars from CO2 and Water

Question 31

Pros and Cons of tap-off cycle

Answer 31

Pros 1. Good for human space flight due to simplicity 2. Less stressful engine shutdown process Cons 1. Startup more complicated 2. Turbine has to withstand higher than normal temperatures

Question 32

Pros and Cons of re-using rockets

Answer 32

Pros 1. Fuel cost only 0.3% of total cost so saves a lot on manufacturing Cons 1. Payload possible reduces by 30% 2. Added cost of development, manufacturing, recovering, possible refurbishment 3. Needs at least 10 re-uses to make it economically even 4. Market for it might not be large enough

Question 33

Pros and Cons of air launch to orbit

Answer 33

Pros 1. Don't have to fly through the low, dense atmosphere, the drag of which is high 2. Nozzle can be optimised to lower ambient pressure 3. Lower insurance cost and special propellants may be applied 4. Launch from selected location 5. Weather is less limiting factor Cons 1. Limited by aircraft size 2. has to change from horizontal to vertical 3. Saving may not be that great

Question 34

Discuss space tourism

Answer 34

- Thus far 7 people have gone to space for a fee of 20-40 million dollars - humans do have desire to go - virgin galactic provide 6 mins weightless experience (hybrid rocket launched from aircraft)

Question 35

Provide applications for rockets in supersonic car racing

Answer 35

- note jet engine alone is not enough - can deliver good thrust-weight ratio - bloodhound SSC - has largest hybrid engine in europe using 3 engines