Rocket Propulsion - Liquid Propellant Rocket Engine Quiz(MCQ)

1 .

What kind of propulsion is used for trajectory adjustments and attitude corrections?

A)

Auxiliary propulsion

B)

Boosting propulsion

C)

Sustaining propulsion

D)

Cryogenic propulsion

Correct Answer : Auxiliary propulsion

Explanation : Auxiliary propulsion helps in trajectory adjustments and attitude corrections. Boosting propulsion imparts a high velocity to the payload. Boosting and auxiliary propulsion are one way of classifying liquid rocket engines.

2 .

How are liquid rocket engines classified on the basis of their feed system?

A)

Boosting or auxiliary

B)

Single flight or reusable

C)

Restartable or single fired

D)

Pressurized or turbopump

Correct Answer : Pressurized or turbopump

Explanation : Feed system is used for the transfer of the liquid propellants from their storage tank to the thrust chamber of the rocket engine. They can be a gas-pressurized feed system or turbo pump feed system.

3 .

If the total propellant flow rate is 24 kg/s and the mixture ratio is 2.3, determine the mass flow rate of the oxidizer.

A)

12.94 kg/s

B)

15.33 kg/s

C)

16.73 kg/s

D)

19.67 kg/s

Correct Answer : 16.73 kg/s

Explanation : mo = r m/(r+1)
= 2.3 x 24/(3.3) = 16.73 kg/s.

4 .

At what temperature are the liquid oxygen and the liquid hydrogen kept in their storage tanks of the cryogenic rocket engine?

A)

-253°C and -183°C

B)

-183°C and -253°C

C)

-183°C for both

D)

-253°C for both

Correct Answer : -183°C and -253°C

Explaination : Liquid oxygen is stored at -183°C and liquid hydrogen is stored at -253°C. Extensive care is taken to ensure that the vaporization losses are minimized for the cryogenic propellants.

5 .

Which of the following ways of thrust chamber cooling may use niobium metal?

A)

Film cooling

B)

Radiation cooling

C)

Cooling jacket

D)

Ablative cooling

Correct Answer : Radiation cooling

Explanation : Niobium is a special high temperature material that can radiate excess heat. So it is used as part of the radiation cooling of the thrust chamber.

6 .

The thruster is also called as ______

A)

nozzle

B)

injector

C)

thrust chamber

D)

combustion chamber

Correct Answer : thrust chamber

Explanation : Thruster is the same as the thrust chamber of a rocket engine. It is the combination of the injector, combustion chamber and the nozzle.

7 .

Which of the following is not a part of a simple pressurized feed system?

A)

Ignitor

B)

Gas starting valve

C)

Pressure regulator

D)

High pressure tank

Correct Answer : Ignitor

Explanation : A simple pressurized feed system has feed lines, gas starting valve, pressure ignitor, high-pressure tank, propellant valves, and propellant tanks. Ignitors are not part of the feed system but are an important part of the thrust chamber.

8 .

Which of the following is not the function of an OMS?

A)

Deorbit

B)

Rendezvous

C)

Orbit circularization

D)

Attitude control

Correct Answer : Attitude control

Explanation : OMS stands for Orbital Maneuver System. It provides thrust for orbital insertion, orbital transfer, orbital circularization, deorbit, abort and rendezvous. RCS (Reaction Control System) deals with attitude control.

9 .

For effective propellant utilization, the rate at which tank can expulse the propellants should be ____________ and the amount of residual propellants should be ___________

A)

low, Low

B)

high, Low

C)

low, High

D)

high, High

Correct Answer : high, Low

Explanation : Higher tank expulsion efficiency coupled with minimal residual propellants in the tank will enable effective propellant utilization for the rocket engine.

10 .

_____ is used for separating liquids from the pressurizing gas.

A)

Filters

B)

Check valves

C)

Elastic bladder

D)

Draining provisions

Correct Answer : Elastic bladder

Explanation : Filters retain contaminants from proceeding to the combustion chamber. Elastic bladder separates liquids from the pressurizing gas. Check valves are one-way valves that allow the flow to happen only in a single direction.

11 .

To enhance reliability on the feed system, the number of components/ subassemblies should be ____________

A)

lower

B)

higher

C)

non-existent

D)

more than 100

Correct Answer : lower

Explanation : Lower number of subassemblies will allow better reliability on the system. But it doesn’t mean that the system should be devoid of subassemblies as using them judiciously can achieve better results with ease.

12 .

___________ are used for preventing the propellant flow back into the tanks and avoiding inadvertent mixing of propellants in the flow passage.

A)

Filters

B)

Check valves

C)

Drainage valves

D)

Isolation valves

Correct Answer : Check valves

Explanation : Check valves allow flow to pass only in one direction. Using them will prevent the flow from going back to the tank or inadvertent mixing.

13 .

When a section of the system has a leak or malfunction ____________ are used to shut it off.

A)

filters

B)

control valves

C)

auxiliary power unit

D)

isolation valves

Correct Answer : isolation valves

Explanation : Isolation valves help in shutting off the system if a leak or malfunction occurs within the system. Control valve varies the size of the passage and controls the flow. Filters does its job by retaining the contaminants from passing to the next level of the system.

14 .

Which of the following materials of the propellant tank requires a thin inner liner of metal to avoid leakage?

A)

Titanium

B)

Aluminum

C)

Stainless steel

D)

Fiber-reinforced plastics

Correct Answer : Fiber-reinforced plastics

Explanation : Fiber reinforced plastics can have tiny pores through which the propellant can escape easily. In order to prevent that, it is coated with a thin layer of some impervious metal.

15 .

What is ullage?

A)

The extra volume of gas above the propellant in a tank

B)

The volume of propellant stored inside a tank neglecting its empty volume

C)

The ratio of the volume of extra gas to that of the propellant after 50% of the propellant has been consumed

D)

The ratio of the volume of the propellant to that of the extra gas after 50% of the propellant has been consumed

Correct Answer : The extra volume of gas above the propellant in a tank

Explanation : Ullage is the extra volume of gas that lies above the propellant in a sealed tank. It is necessary for this extra volume to exist as it takes into account the thermal expansion of the propellant fluid.

16 .

Which component of the external tank of Space Shuttle served the main purpose of distributing thrust loads from SRBs?

A)

LOX tank

B)

LH₂ tank

C)

Intertank

D)

Contractor

Correct Answer : Intertank

Explaination : In addition to the distribution of thrust loads from SRBs of the Space Shuttle, intertank also transferred the loads between other tanks. It is a structural connection between both the LOX and LH₂tanks. It also acts as a protective cover for accommodating some operational instruments.

17 .

Who is the innovative rocket designer who created Atlas ICBM?

A)

Stewart Powell

B)

John von Neumann

C)

Karel Bossart

D)

Bernard A. Schriever

Correct Answer : Karel Bossart

Explanation : Karel Bossart was the mind behind Atlas ICBM. It was first launched in June 1957. Atlas later was used for the first stage of satellite launch vehicles and served for about 5 decades.

18 .

When does the slosh-dynamics problem become useful?

A)

When the liquid is non-Newtonian

B)

When the liquid has a free surface

C)

When the liquid has no free surface

D)

When the material stored inside the tank is thixotropic

Correct Answer : When the liquid has a free surface

Explanation : The liquid stored inside the tank needs to have a free surface for slosh-dynamics to be applied. Propellant slosh in aircraft and rocket tanks are some examples of slosh dynamics problems.

19 .

A good propellant tank must ensure that sloshing is ___________ and vortexing is ____________

A)

minimized; minimized

B)

maximized; minimized

C)

minimized; maximized

D)

maximized; maximized

Correct Answer : minimized; minimized

Explanation : Both sloshing and vortexing need to be minimized. This becomes significant when the tanks are near empty. Sloshing refers to the movement of a liquid inside another body. Vortexing is also similar to sloshing, but the movement is circular in nature.

20 .

What happens to the vehicle mass ratio (Initial mass / Burnout mass) when the residual propellant is not available for combustion?

A)

Increases rapidly

B)

Decreases rapidly

C)

Increases slightly

D)

Decreases slightly

Correct Answer : Decreases slightly

Explanation : Residual propellant when not available for combustion is treated as inert mass. Since the inert mass increases, the burnout mass will also increase. The residual fuel amount is typically small. So the vehicle mass ratio (Initial mass / Burnout mass) will slightly decrease.

21 .

Determine the amount of propellant trapped in pipe, fittings, and valve corners and lost by other means, if the initial mass of the propellant was M and it had an expulsion efficiency of 97%.

A)

0.03M

B)

0.06M

C)

0.48M

D)

0.97M

Correct Answer : 0.03M

Explaination : Expulsion efficiency is the ratio of the amount of propellant available or expelled to the amount of propellant initially present in the tank.
So, 0.97 = m_expel/M
Then m_trapped = M – M_expel = 0.03M.

22 .

Tank pressure for the pressure feed system is between ___________ and _________

A)

100 psi; 2000 psi

B)

200 psi; 1800 psi

C)

300 psi; 2400 psi

D)

800 psi; 3000 psi

Correct Answer : 200 psi; 1800 psi

Explanation : Tank pressure for the pressure feed system lies between 200 and 1800 psi. 1 psi is about 6894.76 Pa. For pump fed systems, the tank pressure lies between 10 and 50 psi.

23 .

Pressurizing gas cannot perform ________

A)

operation of valves

B)

operation of controls

C)

admission of propellants into the tank

D)

expulsion of propellants away from the tank

Correct Answer : admission of propellants into the tank

Explanation : In some systems, pressurizing gases can operate valves and controls. But the main duty of pressurizing valves is the expulsion of propellants away from the tank.

24 .

Which of the following pressurization techniques involves combustion inside the propellant tank?

A)

This is not possible

B)

Gas fed pressurization

C)

Dynamic pressurization

D)

Chemical pressurization

Correct Answer : Chemical pressurization

Explanation : Chemical pressurization involves the injection of fuel or other suitable igniting material to cause combustion inside the propellant tank to produce gases to pressurize the tank. This is a small and light pressurization technique, but it doesn’t often produce reproducible tank pressures.

25 .

For pressurizing cryogenic propellant tanks, the amount of gas required is _________ compared to an equivalent tank containing a non-cryogenic propellant.

A)

more

B)

less

C)

equal

D)

not related in any way

Correct Answer : more

Explanation : A larger mass of the gas will be required in the cryogenic case. This is because the gas will be warmer compared to the cryogenic propellant and it will cool down increasing its density.

26 .

Propellant tanks containing oxygen and nitrogen tetroxide can be pressurized using _________

A)

helium alone

B)

nitrogen alone

C)

nitrogen and helium respectively

D)

helium and nitrogen respectively

Correct Answer : helium alone

Explanation : Nitrogen will react with oxygen and nitrogen tetroxide and decrease the density and concentration of the oxidizer. In order to avoid that, helium is used instead of nitrogen for pressurizing the tanks containing oxygen or nitrogen tetroxide.

27 .

Which of the following is not true about the pressurizing gas?

A)

It should be inert

B)

It should have at least 10% moisture content

C)

It shouldn�t be soluble in the liquid propellant

D)

It shouldn�t condense in the presence of the liquid propellant

Correct Answer : It should have at least 10% moisture content

Explanation : The pressurizing gas should be dry and shouldn’t contain any moisture. Else the moisture might react with the propellant or might dilute it.

28 .

Which of the following gases cannot be used for gas pressure feed systems?

A)

Argon

B)

Helium

C)

Ozone

D)

Nitrogen

Correct Answer : Ozone

Explanation : Inert gases are used in gas pressure feed systems. Ozone is not an inert gas. Hence it cannot be used in this case.

29 .

In turbopump feed systems, the pressurization of the propellants is done by ________ and they are driven by ___________

A)

pumps; pumps

B)

turbines; pumps

C)

turbines; turbines

D)

pumps; turbines

Correct Answer : pumps; turbines

Explanation : Pumps pressurize the propellants while they are driven by turbines. The turbines are run by propellants fed from the main propellant tank, separate propellant tank or by some other means.

30 .

Which of the following is not a characteristic of staged combustion cycle compared to other cycles?

A)

High fuel efficiency

B)

Use of preburners

C)

Engineering simplicity

D)

High engine specific impulse

Correct Answer : Engineering simplicity

Explanation : Staged combustion cycles involve multiple combustion chambers and its engineering design is complex compared to other cycles. The propellant flows through two kinds of combustion chambers – preburner and main combustion chamber.

31 .

Which of the following engines uses a staged combustion cycle?

A)

SpaceX Raptor

B)

Vinci

C)

Ariane 6

D)

Pratt & Whitney RL10

Correct Answer : SpaceX Raptor

Explanation : SpaceX Raptor uses a full flow staged combustion cycle. Rest of them uses expander cycles. Staged combustion cycles involve the propellant going through multiple combustion chambers to undergo its combustion. In full flow staged combustion cycle, both oxygen-rich and fuel-rich preburners are used.

32 .

Which of the following cycles is used in RL10 hydrogen/oxygen rocket engine?

A)

Gas generator cycle

B)

Expander cycle

C)

Staged-combustion cycle

D)

Combustion tap-off cycle

Correct Answer : Expander cycle

Explanation : Expander cycle was used in RL-10 hydrogen/oxygen rocket engine. In this cycle, fuel used for cooling the thrust chamber is used as the working fluid in the turbine used to power the turbopumps. The exhaust from the turbine is fed to the combustion chamber and burned.

33 .

In turbopump feed systems, the turbines derive their power from _______

A)

expansion of hot gases

B)

expansion of cold gases

C)

compression of hot gases

D)

compression of cold gases

Correct Answer : expansion of hot gases

Explanation : The power derived by the turbines come from the expansion of hot gases. This power is in turn used to run the turbopumps.

34 .

Closed cycles in turbopump feed systems are also called as ______

A)

open cycle

B)

engine cycle

C)

bottoming cycle

D)

topping cycle

Correct Answer : topping cycle

Explanation : Closed and open cycles are both engine cycles. Closed cycle is also called topping cycle. In this cycle, the working fluid from the turbine is injected into the combustion chamber so that the energy of this working fluid is also utilized in the engine cycle.

35 .

Open cycles perform better than closed cycle in a turbopump feed type rocket engine.

A)

True

B)

False

C)

Can Not Say

D)

None of the above

Correct Answer : False

Explanation : Closed cycle tends to perform a little better than closed cycles. This is mainly because the exhaust gas from the turbine expands through the thrust chamber nozzle in its full pressure ratio. For open cycles, this expansion process happens across a smaller pressure ratio.

36 .

The oxidiser flow (mo) through the gas generator is ____________ if its flow rate through the pump is 10 kg/s and through the thrust chamber is 5 kg/s.

A)

5 kg/s

B)

15 kg/s

C)

20 kg/s

D)

25 kg/s

Correct Answer : 5 kg/s

Explaination : m_o = (m_o)_gg + (m_o)_c
So, (m_o)_gg = 10 – 5 = 5 kg/s.

37 .

The fuel flow (mf) through the gas generator is ____________ if its flow rate through the pump is 18 kg/s and through the thrust chamber is 10 kg/s.

A)

10 kg/s

B)

8 kg/s

C)

18 kg/s

D)

28 kg/s

Correct Answer : 8 kg/s

Explaination : m_f = (m_f)_gg + (m_f)_c
So, (m_f)_gg = 18 – 10 = 8 kg/s.

38 .

What is the total mass flow rate through the gas generator if the oxidizer flow through it is 15 kg/s and fuel flow is 18 kg/s?

A)

3 kg/s

B)

33 kg/s

C)

48 kg/s

D)

53 kg/s

Correct Answer : 33 kg/s

Explaination : Total mass flow rate through the gas generator m_gg = (m_gg)_o + (m_gg)_f
m_gg = 15 + 18 = 33 kg/s.

39 .

If the pressure rise ΔP across a pump is half the discharge pressure, then which of the following relates the suction pressure P_s to discharge pressure p_d?

A)

P_s = p_d

B)

P_s = 2 x P_d

C)

2 x P_s = P_d

D)

P_s = 4 x P_d

Correct Answer : 2 x P_s = P_d

Explaination : p_d = P_s +ΔP.
Since ΔP = 1/2 P_d, P_d = 2P_s.

40 .

If power of turbines equals P_T, power consumed by pumps is P_P and the power consumed by auxiliaries is P_A, what is the expression for auxiliary power?

A)

P_A = P_P + P_T

B)

P_A = P_T x P_P

C)

P_A = P_T – P_P

D)

P_A = P_P – P_T

Correct Answer : P_A = P_T – P_P

Explaination : Turbine power produced is consumed by pumps as well as the auxiliaries. This is called as the power balance for turbopumps.

41 .

If the gear ratio for fuel pump is thrice that of the oxidizer pump, the shaft speed of fuel pump is _______ the oxidizer pump.

A)

half

B)

twice

C)

thrice

D)

one-third

Correct Answer : one-third

Explanation : One-third because it follows from the relation, a_oN_o = a_fN_f.
Given, a_f=3 x a_o.
Using this, N_f = 1/3 x N_o.

42 .

The power is expressed as the product of torque and _______

A)

shaft speed

B)

vehicle speed

C)

exhaust velocity

D)

volume flow rate per unit cross-sectional area

Correct Answer : shaft speed

Explanation : Torque L x Shaft speed N is a form of representation of the power P. Part of the power produced goes to waste by bearing, seal, transmission, and friction losses.

43 .

Which of the following expressions is true when there are no gears in a particular turbopump?

A)

N_T = N_o ≠ N_f

B)

N_T ≠ N_o = N_f

C)

N_T = N_o = N_f

D)

N_T ≠ N_o ≠ N_f

Correct Answer : N_T = N_o = N_f

Explaination : If there are no gears in a particular turbopump, then all the shaft speeds are same. So N_T = N_o = N_f is the correct expression.

44 .

Reaction control of the Space Shuttle is achieved using ________ thrusters.

A)

24

B)

34

C)

38

D)

48

Correct Answer : 38

Explanation : The Space Shuttle uses 38 different thrusters for its reaction control. Some of the thrusters are spare or redundant. Others perform such complex operations as rendezvous or docking maneuvers, station keeping, orbital corrections, etc.

45 .

For very short pulse duration of the thruster firing, the specific impulse is degraded by __________

A)

0.5-1%

B)

1-5%

C)

2-5%

D)

5-25%

Correct Answer : 5-25%

Explanation : The specific impulse degradation can be from 5% to 25%. This is because the performance during thrust build up and thrust decay are inferior compared to that at the rated operating conditions (without any transience).

46 .

What is range of side force required by a ballistic missile during its final closing maneuver just before nearing in on the target?

A)

100-4500 N

B)

200-6000 N

C)

800-8000 N

D)

1000-18000 N

Correct Answer : 200-6000 N

Explanation : The range of side force required is from 200 N to 6000 N. Upper stages of ballistic missiles are highly maneuverable owing to these high side forces that they require.

47 .

_________ system determines the maneuver to be performed and _________ system sends command signals to specific thrusters for number of signals required.

A)

Guidance; control

B)

Control; guidance

C)

Control; control

D)

Guidance; guidance

Correct Answer : Guidance; control

Explaination : Guidance system identifies the maneuver to be performed and the control system sends the signals to specific thrusters. The signals specify the number of pulses needed to complete the maneuver without fail.

48 .

What is the nature of thrusters and feed system for attitude control rocket engines?

A)

small; common pressurized feed system

B)

small; separate pressurized feed system

C)

large; separate turbopump feed system

D)

large; common turbopump feed system

Correct Answer : small; common pressurized feed system

Explanation : Thrusters used in rocket engines for attitude control, maneuvering and orbital adjustments are usually small. They are located at different spots on the rocket engine but have a common pressurized feed system.

49 .

Rocket engines used for orbital adjustments are also called as _______

A)

strap-on motors

B)

auxiliary rockets

C)

boost propulsion system

D)

primary propulsion system

Correct Answer : auxiliary rockets

Explanation : In addition to orbital adjustments, auxiliary rockets also serve the purpose of maneuvering and attitude control. They are also called as reaction control systems.

50 .

Reaction control systems produce larger thrust than auxiliary propulsion systems.

A)

True

B)

False

C)

Can Not Say

D)

None of the above

Correct Answer : False

Explanation : Reaction control systems are the same as auxiliary propulsion systems. So, the thrust is the same. But reaction control systems produce lesser thrust compared to the main propulsion system.

51 .

A thruster firing repeatedly for 0.010 seconds each time followed by a pause of 0.020 seconds or 0.150 seconds is an example for ________

A)

step input mode

B)

sinusoidal mode

C)

pulsing mode

D)

ramp input mode

Correct Answer : pulsing mode

Explaination : This kind of mode in which the thrusters are fired for a very brief period of time and then a brief pause is maintained just to repeat the whole process again is an example for pulsing mode of operation of the thrusters.

52 .

Which of the following modes of firing thrusters leads to pure modulation?

A)

Pulsing mode

B)

Step input mode

C)

Sinusoidal mode

D)

Ramp input mode

Correct Answer : Pulsing mode

Explanation : In pure modulation, some of the thrusters are fired in pulsing mode. This is a good method for achieving accurate velocity corrections.

53 .

For the application of pure torques in three directions, it requires ______ thrusters.

A)

3

B)

6

C)

9

D)

12

Correct Answer : 12

Explanation : It requires 12 thrusters for the purpose of creating pure torques in the three orthogonal directions. Some of them include roll, pitch and yaw thrusters with control valves.

54 .

When these valves are shut, it shuts off a portion of the propulsion system _________

A)

control valves

B)

burst diaphragm

C)

isolation valves

D)

drainage valves

Correct Answer : isolation valves

Explanation : Isolation valves are shut to negate the contribution from a portion of the propulsion system that it controls. Drainage valves help in draining propellants, while control valves help in controlling the amount of flow passing through the adjacent to the valve.

55 .

Water hammer phenomenon in pipelines can help in the determination of _________

A)

minimum pressure

B)

maximum pressure

C)

minimum temperature

D)

maximum temperature

Correct Answer : maximum pressure

Explanation : Maximum pressure can be determined using the water hammer phenomenon. It is usually caused by the sudden closing of valves.

56 .

Maximum pressure in pipelines is reduced by _______

A)

branching of the pipe but not its friction

B)

friction and branching of the pipe

C)

friction of the pipe but not its branching

D)

neither friction nor branching of the pipe

Correct Answer : friction and branching of the pipe

Explanation : Analysis of a particular hammer phenomenon in the pipelines will aid in determining the maximum pressure. This maximum pressure can reduce because of frictional losses and due to branching in the pipe.

57 .

Which of the following is the correct function of pipes and lines in a rocket engine?

A)

Allow thermal expansion and minimize vibrational effects

B)

Allow thermal expansion and maximize vibrational effects

C)

Minimize thermal expansion and minimize vibrational effects

D)

Minimize thermal expansion and maximize vibrational effects

Correct Answer : Allow thermal expansion and minimize vibrational effects

Explanation : Pipes and lines in a rocket engine should allow thermal expansion and it should minimize vibrational effects. Irregular fluid flow due to inadequate pipe design may lead to performance issues in the rocket engine.

58 .

Two valves commonly used in pressurized feed systems are _________ and _________

A)

latch valves and drainage valves

B)

burst diaphragm and latch valves

C)

burst diaphragm and drainage valves

D)

latch valves and Isolation valves

Correct Answer : latch valves and Isolation valves

Explanation : Isolation and latch valves are commonly used for pressurized feed systems. For opening and shutting them down, they require power, but when latched on to some position they don’t require any power.

59 .

Which of these is a very simple and light valve?

A)

Latch valves

B)

Isolation valves

C)

Burst diaphragm

D)

Drainage valves

Correct Answer : Burst diaphragm

Explanation : Burst diaphragm is a very simple and light valve. It is a circular disc like material which is designed so as to burst when it faces more than a particular pressure differential.

60 .

Fluids in a rocket engine are conveyed through __________

A)

pipes

B)

ducts

C)

channels

D)

contractions

Correct Answer : pipes

Explanation : Pipelines are used in conveying fluids in a rocket engine. The complexity of the pipeline network in rocket engines will increase with its size and capabilities.

61 .

Which of the following valves help in controlling gas pressures?

A)

Latch valves

B)

Isolation valves

C)

Burst diaphragm

D)

Pressure regulator

Correct Answer : Pressure regulator

Explanation : Pressure regulator, as the name mentions, helps in regulating or controlling gas pressure. Other valves serve different purposes, like maintaining the flow until a pressure differential (burst diaphragm) or for isolation of a particular flow region.

62 .

German antiaircraft missile Wasserfall used four of which of the following valves?

A)

Latch valves

B)

Burst diaphragm

C)

Isolation valves

D)

Drainage valves

Correct Answer : Burst diaphragm

Explanation : Burst diaphragm is used in the German missile Wasserfall. It actually used 4 of such burst disks.

63 .

Which of the following is not a property of the main liquid oxygen valve?

A)

Low pressure

B)

High pressure

C)

Cryogenic

D)

Reusable ball valve

Correct Answer : Low pressure

Explanation : Main liquid oxygen valves are under high pressure. Since liquid oxygen easily evaporates under normal atmospheric conditions, they are kept in cryogenic tanks. These valves also make use of reusable ball valves.