patrickfleith/Astro-mcqa huggingface dataset:
Question: In spacecraft link analysis which is the name used to refer to the signal transmitted from end users (for instance military troops) to the satellite?
Options:
Forward uplink, Forward downlink, Return downlink, Return uplink
Answer key (one line per option, 1 = correct):
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Justification: Forward communications links carry information toward user terminals, while return communications links carry information away from user terminals. Both forward and return links include uplinks and downlinks
Question: What does an engineer means when she say that "the link closes" in communication link analysis?
Options:
The communication is finished and there are no more signal passing through the communication chain
The difference between the power-to-noise ratio and the detection threshold is positive
The difference between the power-to-noise ratio and the detection threshold is negative
The energy received by the receiving antenna is strictly equal to the emitted energy (outputting the emitter's amplifier)
The link margin is negative
Answer key (one line per option, 1 = correct):
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Justification: The difference between the power-to-noise ratio and tabulated detection thresholds refer to a parameter called the link margin. When the link margin is positive, the received signal can be detected, and the link is said to "close". When it is negative however the signal cannot be detected and the link does not close.
Question: Which satellite band in the electromagnetic spectrum correspond to the highest frequencies?
Options:
C-band, V-band, Ka-band, Q-band
Answer key (one line per option, 1 = correct):
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Justification: V-band, mostly used for inter-satellite links uses frequency between 40 GHz and 75 GHz, then Q-band (30-40 GHz), then are Ka-band (18 to 30 GHz). C-band are of much lower frequencies, in the range of 4 to 7 GHz.
Question: Which of the following satellite band is associated with its correct frequency range?
Options:
Ka-band (18 to 30 GHz)
Ku-band (11 to 18 GHz)
S-band (7 to 11 GHz)
C-band (4 to 7 GHz)
Q-band (2 to 4 GHz)
V-band (1 to 2 Gz)
Answer key (one line per option, 1 = correct):
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Justification: S-band frequencies are within 2 to 4 GHz, Q-band frequencies are within 30 to 40 GHz (much higher than those reported), and V-band are even higher frequencies, above 40 GHz. It is L-band which correspond to frequencies between 1 and 2 GHz.
Question: True or False: an electromagnetic wave to that is RHCP means it is right-handed circular polarised and the electric field vector rotates anticlockwise as viewed from the direction of propagation?
Options:
True, False
Answer key (one line per option, 1 = correct):
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Justification: It False because RHCP means it is right-handed circular polarised and the electric field vector rotates clockwise (not anticlockwise) as viewed from the direction of propagation.
Question: Why are Decibels used for communication links analyses?
Options:
In hommage of George Mikari Decibels, the inventor of the mechanical speaker
This is a standard introduced by German scientist in Huntsville, Alabama, during Rocket Engine Fire test and was kept for legacy purpose and now introduced in the ECSS
Because link analyses involves calculations with numbers that may differ by many orders of magnitude, decibel is simpler, faster and less error-prone.
Because of Aristote
Answer key (one line per option, 1 = correct):
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Question: What is the decibel equivalent of a 135 W amplifier output power relative to a 1 W reference?
Options:
16.0, 18.2, 21.3, 23.4
Answer key (one line per option, 1 = correct):
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Justification: The power in Decibels is given by P(dB) = 10 * LOG10( P / Pref ) = 10 * LOG10( 135 / 1 ) = 21.3
Question: How do you express the antenna gain G as a function of the antenna directivity D and various losses L?
Options:
G = D / L
G = D^2 / L
G = (D - L) / L
G = D - L
Answer key (one line per option, 1 = correct):
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Justification: The total amplification factor of an antenna is given by its gain G, a value that includes both the focusing effect of the antenna (directivity D), which is a mesure of the antenna's ability to concentrate energy in a given direction, and various losses (including ohmic transmission-line losses, L for example). The formula is G = D - L
Question: What does A refer to in the formula G = etha * (4*pi / lambda^2 ) * A for communication link analyses
Options:
A relates to the absorptivity of the emitting medium (dimensionless)
A relates to the physical size of the antenna aperture (m^2)
A to the antenna volume (m^3)
Answer key (one line per option, 1 = correct):
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Question: How do you compute theta (in degrees), the half-power beamwidth in link analyses?
Options:
You cannot, you need to measure it
Theta = frequency / Diameter
Theta = - k*frequency, k is a tablulated constant
Theta = 21 / (frequency * Diameter)
Answer key (one line per option, 1 = correct):
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Question: Which is a major contribution to the antenna pointing error on-board satellite?
Options:
thermal distortions, atmospheric residual drag, fixed misalignment
Answer key (one line per option, 1 = correct):
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Justification: Atmospheric drag is negligible and fixed misalignment is usually mitigated on-ground and static. However, a source for variable pointing error is related to thermal distortion that results from variable heating of different antenna and spacecraft structures, changing with as the orientation of the satellite and its antennas changes with respect to the Sun, Earth, and other satellite structures like solar panels and other antennas?
Question: What does typical design allow for maximum satellite antennas pointing errors?
Options:
Usually up to 50% of the beamwidth because it is sized to account for that loss
Usually around 10% of the beamwidth, so 0.1 degree for 1 degree beamwidth
Usually maximum 1% of the beamwidth, because beyond 1% the power-to-noise ratio decays exponentially minus infinity
Answer key (one line per option, 1 = correct):
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Question: Who is not a European Astronaut?
Options:
Thomas Pesquet, Christina Koch, Jeremy Hansen, Samantha Cristoforetti
Answer key (one line per option, 1 = correct):
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Question: What is the key difference between a jet engine and a liquid rocket engine?
Options:
The jet engine is in general more expensive, The liquid rocket engine has to carry the oxidizer, The jet engine produce a long flamme tail after combustion
Answer key (one line per option, 1 = correct):
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Justification: The difference between a jet engine and a rocket engine, the jet engine only needs to carry its own fuel. A rocket, on the other hand, has to carry not only its own fuel but also the oxidizer, which in most cases is oxygen, either a compressed gas or liquid oxygen.
Question: How do satellite communication missions usually cover irregular areas such as the United States, without providing bandwidth to unwanted areas (oceans, prohibited areas)?
Options:
Increasing satellite altitude, Utilising higher frequency bands, Encrypting the signal, Using shaped beam reflector antennas
Answer key (one line per option, 1 = correct):
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Justification: Increasing the altitude would actually broaden the signal. Higher frequency bandas can offer more focused beams, but don't inherently prevent signal spill-over into unwanted areas. The key is the shape and direction of the beam, not the frequency. Finally, encrypting the signal does not prevent it from being broadcast over unwanted area, it only controls who can access the content of the signal.
Question: Assuming that D_ideal is the ideal antenna maximum directivity and A_theta is the coverage area in deg^2: Which of the following is a valid formula expressing the maximum directivity achievable for an ideal antenna that covers a small solid angle?
Options:
D_ideal = 10 * log (A_theta)
D_ideal = exp(-A_theta)
D_ideal = A_theta / log(A_theta)
D_ideal = 46.15 - 10 * log(A_theta)
Answer key (one line per option, 1 = correct):
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Justification: This provides a first level approximation for the link equation.
Question: In space communication link analyses, the ideal directivity calculations do not include antenna radiated efficiency, which is a measure of the power being radiated outside of the desired coverage area. What is the typical range of antenna efficiencies to adjust the ideal directivity?
Options:
20 to 40%, 55 to 75%, 80 to 99%, 98 to 99.5%
Answer key (one line per option, 1 = correct):
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Question: For ground or satellite antennas, which of the following are typical contributing components to the noise temperature?
Options:
noise temperature that originates from the thermally radiated energy of objects that appear within the antenna's field of view
noise temperature that originates from the temperature of the antenna feed structure and transmission losses within the antenna and feed assembly itself
noise temperature that originates high energy ionizing particles deposited energy hitting the antenna structure
noise temperature that originates from the delta-phi (smalled boresight angle possible) product with the Earth reflected magnetic field when crossing of the south atlantic anomaly (SAA)
Answer key (one line per option, 1 = correct):
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Justification: noise temperature that originates high energy ionising particles deposited energy hitting the antenna structure is negligible and the following "noise temperature that originates from the delta-phi (smallest bore-sight angle possible) product with the Earth reflected magnetic field when crossing of the South Atlantic Anomaly (SAA)" is not a concept used or reference in space mission engineering.
Question: What are realistic mission objectives for a missions to Mars?
Options:
ISRU Technology Demonstration
Geological and topological study to understand the historical Mars-Earth collision which led to the creation of Earth's Moon.
Oild fields scoutting for future super tanker missions
Search for scientific evidence for past life on Mars
Answer key (one line per option, 1 = correct):
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Question: How long would a typical human crewed mission to Mars last (only the duration of the trip to reach Mars) for conjunction-type missions?
Options:
3 to 4 months, 6 to 9 months, 3 to 4 years, more than 7 years
Answer key (one line per option, 1 = correct):
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Question: How are the two types chemical compounds of bipropellant propulsion systems called?
Options:
Igniter and fuel, igniter and oxidizer, fuel and oxidizer
Answer key (one line per option, 1 = correct):
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Question: Which of the following rocket engine(s) is / were manufactured by "Aerojet" ?
Options:
MONARC-445, MR-111C, CHT-20
Answer key (one line per option, 1 = correct):
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Justification: The MR-111C is a flight proven monopropellant hydrazine thruster.
Question: Having stages in space launchers is advantageous because it disposes the the mass of the expended stage (tank, engine, etc...). But are there single stage launchers that are operational as of today in 2024 capable of launching a payload to Low Earth Orbit?
Options:
Yes, No
Answer key (one line per option, 1 = correct):
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Question: Select all the combinations of propulsion system and applications that are typical among the following?
Options:
Cold Gas propulsion for orbit insertion, Solid propulsion for orbit insertion, Liquid monopropellant for orbit insertion, Liquid monopropellant for attitude control, Electric propulsion for orbit maintenance and maneuvering, Liquid bipropellant for orbit insertion
Answer key (one line per option, 1 = correct):
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Question: What is the typical range of specific impulse for liquid monopropellant systems?
Options:
45 - 75s, 200 - 235s, 274 - 467s, 500 - 3000s
Answer key (one line per option, 1 = correct):
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Question: Select all the advantages of monopropellant hydrazine propulsion systems over bipropellants propulsion systems?
Options:
system simplicity, long term storability, capability to restart, higher specific impulse, lower toxicity
Answer key (one line per option, 1 = correct):
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Justification: Hydrazine monopropellant systems have lower Isp (max 230s) not higher than most bipropellants systems. Also hydrazine toxicity poses several challenges, and research is being conducted to find alternatives which are safer to handle.
Question: How does the combustion takes place for hydrazine monoprop system?
Options:
Hydrazine ignites spontaneous in contact of an hydrogen isotope, typically deuterium
Hydrazine decomposes on a micro-fluidic chip, typically made of palladium enriched carbon nanotubes in a sillicon wafer
Hydrazine ignites spontaneous in presence of an high-voltage electric discharge, typically 20,000 - 30,000 Volts
Hydrazine decomposes on a catalyst material, typically iridium
Answer key (one line per option, 1 = correct):
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Question: What is the name of the nozzle cooling technique, sometimes using in expander cycles, where one of the propellant (usually the fuel but not always) passes around the nozzle to cool it?
Options:
Regenerative cooling, Ablative cooling, Film cooling
Answer key (one line per option, 1 = correct):
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Question: What does ablative cooling in rocket engine propulsion systems refer to?
Options:
chamber walls made of ablative material which decomposes into gas when heat up, hence acting as a coolant
combustion-generated heat is conducted through the chamber walls and rejected through radiation
the heat is absorbed by a thin film coating made of ablatium
Answer key (one line per option, 1 = correct):
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Question: What does AOCS usually refer to in Astronautics?
Options:
Astronomical Observation and Calculation System, Advanced Orbital Communication Satellite, Aerodynamic Optimization for Crew Safety, Attitude and Orbit Control System
Answer key (one line per option, 1 = correct):
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Question: Which axis of the coordinate system for the ISS AOCS is used in the direction of the velocity vector?
Options:
+X (roll)
+X (pitch)
+X (yaw)
-X (roll)
-X (pitch)
-X (yaw)
Answer key (one line per option, 1 = correct):
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Justification: The choice of the ISS fixed coordinate system is pretty much like in aviation where we have the forward portion of ISS oriented toward the velocity vector and that's a + X axis. X is also correspond to the roll.
Question: In the LVLH coordinate system that is often used for AOCS, what is the direction of each axis ofr a spacecraft on orbit around the Earth?
Options:
X towards the center of the Earth, Y towards the rear of the spacecraft, Z towards the north of the orbit
X towards the Noth of the orbit, Y towards the center of the Earth, Z towards the spacecraft velocity vector
X towards the spacecraft velocity vector, Y towards the south of the orbit, Z towards the center of the Earth
Answer key (one line per option, 1 = correct):
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Question: ISS and Space Shuttle euler sequence was Pitch, Yaw, Roll. This is difference from most spacecraft. Which Euler sequence do spacecrafts in general?
Options:
Yaw Roll Pitch (YRP)
Yaw Pitch Roll (YPR)
Roll Pitch Yaw (RPY)
Roll Yaw Pitch (RYP)
Answer key (one line per option, 1 = correct):
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Question: How it is possible to maintain a certain orientation by spinning a spacecraft?
Options:
Due to the electron spin, Due to the gyroscopic effect, Due to the rotational speed being waved
Answer key (one line per option, 1 = correct):
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Question: How is it possible to use gravity gradient for attitude control?
Options:
For an elongated object, the gravity force at the bottom of the object is greater than the force at the top
For an elongated object, the gravity force at the top of the object is greater than the force at the bottom
For a spherical rotating object, the gravity at the bottom of the sphere is greater than the gravity at the top
For a spherical rotating object, the gravity gradient originates from the fluid forces momentum in the intern structure.
Answer key (one line per option, 1 = correct):
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Question: Which of the following is the primary factor determine the voltage of a solar array?
Options:
The temperature of the environment where the solar array is in, The solar cell thickness, The number of cells connected in series to form a string, The mounting structure of the solar cell
Answer key (one line per option, 1 = correct):
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Question: Which of the following time point is used to size a satellite photovoltaic system?
Options:
Beginning-of-life power requirements, Average life power requirements plus a 10 to 20 margin, End-of-life power requirements
Answer key (one line per option, 1 = correct):
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Justification: This is because power requirement have to be met, even at end-of-life otherwise the satellite would not be able to operate nominally at towards the end of its mission. This results in the system often being oversized for BOL requirements and can cause power problems if not taken care of.
Question: Which of the following are the lower costs cells that could be in use for satellite solar arrays?
Options:
Thin film amorphous Silicon cells, Gallium-Arsenide Triple Junction cells, Indium Phosphide cells
Answer key (one line per option, 1 = correct):
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Question: Which of the following rechargeable battery technologies used for satellite has the higher energy density?
Options:
Li-ion, Ni-Cd, Ni-H2
Answer key (one line per option, 1 = correct):
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Justification: Ni-Cd has about 30 Wh/kg, Ni-H2 has about 60 Wh/kg and Li-ion more than 125 Wh/kg energy storage density
Question: Assuming a similar lifetime, and temperature maintained range, which of the following orbit would enable to use secondary batteries with a higher depth of discharge?
Options:
Low-Earth Equatorial Orbit mission, Sun-Synchronous Polar Orbit mission, Geostationary Orbit mission
Answer key (one line per option, 1 = correct):
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Justification: Geostationary satellite experience less frequent eclipse than Low-Earth orbiting missing, reducing the number of charge/discharge cycle on the batteries. Relaxing the number of charge/discharge requirement enables usually to increase the depth-of-discharge.
Question: Which of the following are typical ranges of load input power requirements in satellite engineering?
Options:
Normal Steady State Voltage Range: 5 to 7 V DC, Normal Steady State Voltage Range: 25 to 21 V DC, Normal Steady State Voltage Range: 150 to 220 V DC, Max Current 60 Amp, Nominal Ripple 1 V peak to peak
Answer key (one line per option, 1 = correct):
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Justification: Typical max current is often around 15 Amp (even though not always!)
Question: Which are the most common power bus control techniques used in satellite electrical power subsystems?
Options:
Alternating Current Frequency Adjustment (ACFA)
Voltage Multiplication Regulation (VMR)
Capacitive Load Stabilization (CLS)
Direct Energy Transfer (DET)
Peak Power Tracker (PPT)
Answer key (one line per option, 1 = correct):
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Question: Which of the following buck-boost derived regulator is the most complex among the following?
Options:
Full Bridge Regulator, Flyback, Two-switch Forward
Answer key (one line per option, 1 = correct):
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Justification: From least complex to most complex are the flyback, single switch forward, two switch forward, push-pull, and full-bridge regulators
Question: Which technique used on spacecraft power regulators (buck-boost) enables to further enhance their efficiency?
Options:
Resonant Mode Switching, Continuous Current Calibration, Voltage Ripple Reduction
Answer key (one line per option, 1 = correct):
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Question: Which of the following power source in spacecraft design usually require storage in case of Eclipse?
Options:
Fuell cells, Nuclear reactor, Radioistope Thermoelectric Generator, Solar Thermal Dynamic, Solar Photovoltaic
Answer key (one line per option, 1 = correct):
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Justification: Both solar thermal dynamic and solar photovoltaic do not generate power during eclipse so storage is require to keep the satellite powered on.
Question: Which of these statements are true of solid rockets?
Options:
They are relatively simple to build and operate, They provide limited ability to control thrust, They inherently produce more thrust than liquid rockets, They generate a lot of noise and vibration
Answer key (one line per option, 1 = correct):
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Question: Which of these statements are true of liquid rockets? Tell all that apply.
Options:
They inherently produce less thrust than solid rockets
They must store the oxidizer and fuel propellant components onboard in separate compartments
To get high performance, they must use turbo pumps to direct the propellant into the combustion chamber
They encounter high temperatures and pressures during combustion
Answer key (one line per option, 1 = correct):
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Question: When applying the idea rocket equation, which components usually comprise the the rocket initial mass ?
Options:
Payload, Propellant, Structure
Answer key (one line per option, 1 = correct):
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Justification: The initial mass at launch consists of payload, propellant, and rocket structure. The final mass refers to when the propellant has been consumed, and thus consists of payload and structure.
Question: When applying the idea rocket equation, which components usually comprise the the rocket final mass ?
Options:
Payload, Propellant, Structure
Answer key (one line per option, 1 = correct):
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Justification: The initial mass at launch consists of payload, propellant, and rocket structure. The final mass refers to when the propellant has been consumed, and thus consists of payload and structure.
Question: Consider a rocket in free space having two engines with identical Isp, connected to a single propellant system. Recall that the relationship between specific impulse and exhaust velocity is  Vexhaust  = go * Isp.
If one engine fails, what is the impact on the total  ΔV  that can be obtained from the system?
Options:
ΔV will double, ΔV will be cut in half, ΔV will stay the same
Answer key (one line per option, 1 = correct):
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Justification: If one engine fails, there is no change in specific impulse, or in the total amount of propellant available. Therefore, the total ΔV that is obtainable from the system is the same. However, the thrust is cut in half, so it will take twice as long to achieve the same ΔV (until the propellant is consumed).
Question: Consider a rocket carrying 100,000 kg of propellant, 10,000 kg of structure and 5,000 kg of payload. What is the structure fraction of this rocket?
Options:
0.053, 0.075, 0.087, 0.019
Answer key (one line per option, 1 = correct):
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Justification: The structure fraction is given by the ration of the mass of the structure (10,000 kg) divided by the sum of the structure, payload and propellant (100,000 + 10,000 + 5,000). The result is 10,000 / 115,000 which is approximately 0.087.
Question: Consider a rocket carrying 100,000 kg of propellant, 10,000 kg of structure and 5,000 kg of payload. Using the ideal rocket equation, and assuming a specific impulse of 450s, what would be value of the Delta V in m/s that this rocket would be able to produce if all the propellant is consumed in one stage?
Options:
8991 m/s, 9991 m/s, 10991 m/s, 11991 m/s, 12991 m/s
Answer key (one line per option, 1 = correct):
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Justification: The ideal rocket equation gives ΔV = g0 * Isp * ln(mass_initial / mass_final).
g0 = 9.81 m/s^2
Isp = 450 s
We need to compute the initial mass of the rocket and the final mass of the rocket.

1. Initial mass of the rocket:
initial_mass = payload_mass + structure_mass + propellant_mass = 5,000 + 10,000 + 100,000 = 115,000 kg.

2. Final mass of the rocket (everything except the propellant that has been burnt)
final_mass = payload_mass + structure_mass = 5,000 + 10,000 = 15,000 kg

ΔV = 9.81 * 450 * ln( 115,000 / 15,000) = 8991 m/s