Spaceflight Mechanics - Planetary Atmosphere Quiz(MCQ)

Correct Answer :   Helium

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Explanation : Helium is the most common gas in the atmosphere of our solar system. It comprises of a significant portion in the atmosphere of Sun, Mercury, Moon, Jupiter, Saturn, Uranus and Neptune. The second common gas in the solar system is Hydrogen gas, followed by Nitrogen and Carbon dioxide gas.

Correct Answer :   Hydrogen

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Explanation : Stellar atmosphere refers to the atmosphere of the stars. It is mainly comprised of Hydrogen, which is about 70% of the total atmosphere by mass. The second major component of stellar atmosphere is Helium, which is about 25% of the total atmosphere by mass.

Correct Answer :   It is a thin blanket of gases surrounding a planet or an object

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Explanation : The term ‘Atmosphere’ can be defined as a thin blanket of gases surrounding a planet or an object in outer space. As it is made up of gases, it cannot be a hard shell. It is not caused due to solar radiations.

Correct Answer :   False

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Explanation : Atmosphere is not limited only to planets. Stars also have an outer atmosphere, generally referred to as Stellar Atmosphere. Celestial objects like comets also possess their own atmosphere.

Correct Answer :   Vertical variations of thermodynamic properties only

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Explanation : Horizontal effects, caused by weather & planetary rotation, have negligible variation in thermodynamic properties as compared to the Vertical variations. The thermodynamic properties of the atmosphere vary greatly with the altitude from the surface of the planet. More the change in the altitude, more is the variation in properties. So, only vertical variations are considered in all planetary atmospheric models.

Correct Answer :   It is under constant perturbation due to winds and two-phase non-equilibrium of water vapour & carbon dioxide vapour on Mars and Earth respectively

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Explanation : Weather is a local phenomenon which occurs only at low altitudes of the atmosphere. At low altitudes, the atmosphere is assumed to be in thermal equilibrium & is not influenced by external factors like electromagnetism or chemical reactions. But it is constantly disturbed by horizontal winds and two-phase non-equilibrium due to water vapour on Earth & carbon dioxide vapour on Mars.

Correct Answer :   Nitrogen

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Explanation : Carbon dioxide comprises of 96% of the atmosphere on Venus. It also contains small traces of nitrogen & sulphur oxides. So, the most abundant gas in the atmosphere of Venus is Carbon dioxide gas. This makes the atmosphere more denser & hotter as compared to Earth.

Correct Answer :   Core of the planet

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Explanation : Out of the options, Core of the planet is incorrect. The planetary atmosphere varies with difference in gravity, chemical composition, planetary magnetic field, solar radiation, planetary rotation etc. The core of the planet does not play a major role as a variable in atmosphere.

Correct Answer :   Mercury

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Explanation : The atmosphere of Mercury has 42% of oxygen, which makes it the highest percentage in the solar system. Earth’s atmosphere contains 21% of oxygen whereas Jupiter & Saturn contains negligible amounts of oxygen in their atmosphere.

Correct Answer :   78% and 21%

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Explaination : Earth’s atmosphere contains about 78% Nitrogen and 21% Oxygen. It also has other gases such as 0.97% Argon and 0.03% Carbon dioxide/Water

Correct Answer :   Troposphere

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Explanation : Troposphere is where most of the weather phenomena occur. This layer is situated between the mean sea level and 18 km above mean sea level if the tropopause is included.

Correct Answer :   216.65 K

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Explaination : The standard atmosphere temperature will remain the same between geopotential altitudes of 12 km and 13 km since both heights are a part of the tropopause which is an isothermal layer of our atmosphere. Therefore, the answer is 216.65 K, the same as at 12 km.

Correct Answer :   98.46 km

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Explaination : Given,
Geometric altitude (h_g) = 100 km
Radius of earth (R_E) = 6378 km
Geopotential altitude (h) = (R_E / (R_E + h_g)). h_g
= (6378/(6378+100))*(100)
= 98.46 km

Correct Answer :   95.5% of gravity at MSL

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Explaination : Given,
Gravity at MSL (g₀) = 9.81 m/s²
Geopotential altitude (h) = 300 km
Radius of earth (R_E) = 6378 km
Gravity at 300 km above MSL (g) = g₀.(R_E/(R_E + h))²
= 9.81*(6378/(6378+300))²
= 9.718 m/s²
Percentage = (9.718/9.81) x 100% = 95.5% of MSL gravity

Correct Answer :   250.17 K

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Explaination : Given,
Temperature gradient (a) = 0.001 K/m = 1 K/km
At point 1, h₁ = 20 km, T₁ = 216.65 K
At point 2, h₂ = 32 km, T₂ =?
T₂ = a.(h₂ – h₁) + T₁
= 1*(32-20) + 216.65
= 228.65 K

Correct Answer :   0.365 kg/m³

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Explaination : Given,
At MSL, Temperature (T₁) = 288.16 K
Pressure (p₁) = 101325 Pa
Density (ρ₁) = 1.225 kg/m³
At 11 km, Temperature (T) = 216.66 K
Pressure (p) = 22700 Pa
Density (ρ) =?
From the equation of state,
p/p₁ = (ρT)/(ρ₁/T₁)
ρ = (pρ₁T₁)/(p₁T)
= (22700*1.225*288.16)/(101325*216.66)
= 0.365 kg/m³

Correct Answer :   False

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Explanation : False because the stratosphere contains the ozone and cabin pressurization in the stratosphere could lead to ozone poisoning. Also, because the density at that altitude is very low.

Correct Answer :   Rocket Engine

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Explanation : All engines except the rocket engine require air to function. Since, there is no air/atmosphere within the mesosphere only a rocket engine will work. Rocket engine has its own propellant and oxidizer.

Correct Answer :   Mesopause

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Explanation : Mesopause is the coldest isothermal layer. It has a temperature of about 190 K or -83°C. Tropopause and Stratopause are relatively warmer. Whereas, exopause doesn’t exist.

Correct Answer :   1.54 x 10^-4 per meter

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Explaination : Given,
Acceleration due to gravity (g) = 9.81 m/s²
Specific gas constant (R) = 287 J/kg.K
Temperature (T) = 222.6 K
Combining hydrostatic equation and equation of state we get,
Change in pressure with altitude, (dp/p)/dh = g/(RT)
= 9.81/(287*222.6)
= 1.54 x 10^-4 per meter

Correct Answer :   390 ⁰R

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Explaination : Given,
Pressure (p) = 629.66 lb/ft²
Density (ρ) = 0.9408 x 10^-3 slug/ft³
Specific gas constant (R) = 1716 lb.ft/slug.⁰R
Using equation of state,
Temperature, T = p/(ρR)
= 629.66/(0.9408*10^-3*1716)
= 390 ⁰R

Correct Answer :   Karman line

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Explanation : The beginning of space is officially denoted at an altitude of 100 km which is also known as the Kármán line. After this line the aerodynamic effects are minimal. Cold gas thrusters are used to correct orientation after this line as aerodynamic control surfaces are useless.

Correct Answer :   262 K

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Explanation : Toussaint’s formula is given by T = 15 – 0.0065h
Where, T is the temperature in Celsius and h is the geopotential altitude in metres.
Therefore, T = 15 – 0.0065*(4000)
= – 11°C
= -11 + 273 K
= 262 K