patrickfleith/Astro-mcqa huggingface dataset:
Question: What is the effect of a posigrade burn on a circular orbit?
Options:
There is no effect, The altitude 90° from the burn point is decreased, The altitude 180° from the burn point is decreased, The altitude 180° from the burn point is increased
Answer key (one line per option, 1 = correct):
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Justification: At the burn point, the velocity is increased. It means that the energy of the spacecraft changes and the geometry of the orbit changes. The altitude of the burn point will not change, but becomes the minimal altitude if the initial orbit is circular. Its maximum will be reached at the apogee, 180° from the perigee. Thus the altitude 180° from the burn point is increased.
Question: What is the reference point of the rendezvous profile diagram?
Options:
The chaser, The target, The center of the Earth, The control center
Answer key (one line per option, 1 = correct):
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Justification: The rendezvous profile diagram is centered and relative to the target.
Question: What is the shape of a circular orbit, for the chaser, in a rendezvous profile diagram? (assuming the target is higher than the chaser).
Options:
A point, A periodic wavy and pointy curve, A line, A sinusoidal, A cycloid
Answer key (one line per option, 1 = correct):
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Justification: On a circular orbit, the altitude does not change, so the value of the R axis does not change. The V axis does not stay the same as the velocity of the two spacecraft are not the same. The chaser will move along an horizontal line in the diagram.
Question: A spacecraft on a circular orbit at 400 km does a retrograde burn of 1 m/s. What will be the change in the altitude (in km) of the perigee?
Options:
1.5, 2.5, 3.5, 4.5
Answer key (one line per option, 1 = correct):
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Justification: This can be computed in a straightforward way using the equation Delta-r is close to 3.5 * Delta-V where Delta-r is in km and the burn value in m/s.
Question: A chaser is on a circular orbit at the same altitude as the target and few kilometers behind. Where will the chaser be one orbit after a posigrade burn ?
Options:
The chaser will be much further ahead, The chaser will be behind the target, further away than it was initally, The chaser will be higher than the target, The chaser will be lower than the target
Answer key (one line per option, 1 = correct):
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Justification: Since there is a posigrade burn, the altitude of the semi-major axis is increased, the orbital velocity is decreased. If the change of altitude is sufficient, the chaser will drift behind the target further away than it was initially.
Question: What is the definition of the Astronomical Unit (AU)?
Options:
It is the average distance between the Earth and the Sun, It is the average radius of the solar system, It is the average radius of the Sun, It is the average distance betwteen the Moon and the Earth
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Justification: An Astronomical Unit is the mean distance between the Earth and the Sun. In 2012, the International Astronomical Union defined the distance to be 149,597,870,700 meters.
Question: What is the sphere of influence?
Options:
A region in space that can be controlled by a spacecraft
The region around the Sun in which only planets have a gravitational influence
A sphere around each planet inside which the motion of a spacecraft must be considered a three-body Keplerian problem
A sphere around each planet inside which the motion of a spacecraft is considered to be two-body Keplerian
Answer key (one line per option, 1 = correct):
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Justification: For the Earth, the radius of the sphere of influence is about 924 000 km.
Question: What is the hyperbolic excess velocity?
Options:
The velocity required to get into a LEO orbit from the surface of the Earth, The velocity at which we cross the sphere of influence, The velocity needed to reach the arriving planet, The velocity needed to reach the sphere of influence
Answer key (one line per option, 1 = correct):
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Justification: It is the speed in excess of the minimum velocity required to reach the sphere of influence.
Question: A interplanetary probe is in the sphere of influence of the Earth, in transit towards an inner planet. What is its energy with respect to the Earth?
Options:
E <= 0
E < 0
E = 0
E > 0
Answer key (one line per option, 1 = correct):
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Justification: The energy for the hyperbola is epsilon = + mu / 2a (energy per unit mass), thus positive. Another way to see this, is that the probe is no longer gravitationally bounded to the Earth, ergo its energy is positive.
Question: What is the ideal shape of the transfer trajectory between two planets, and why?
Options:
A Hohmann transfer orbit, because it is the less expensive orbit in terms of energy
A straight line, because is it the shortest path
A Hohmann transfer orbit, because it is the shortest path
A straight line, because it is the less expensive orbit in terms of energy
Answer key (one line per option, 1 = correct):
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Justification: The Hohmann transfer is the optimal and ideal trajectory in terms of time of flight and fuel. However, in reality, different trajectories are preferred. For Mars transfer, more energetic trajectories are usually preferred to shorten the time of flight.
Question: An interplanetary probe is in transit towards an inner planet, very close to the arrival planet. How is the velocity of the planet with respect to the velocity of the probe?
Options:
faster, identifical, slower
Answer key (one line per option, 1 = correct):
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Justification: The transfer ellipse ressemble a Hohmann transfer to go from a high to a lower orbit, thus the velocity of the probe is higher than the arrival planet. When leaving the Earth, the probe should also reduce its heliocentric speed. This can be done by crossing the sphere of influence with the velocity vector of the spacecraft in the opposite direction of Earth's velocity vector.
Question: There is no burn during the slingshot maneuvers and yet the speed in the heliocentric reference frame increases. How is that possible?
Options:
At the periapsis of the slingshot, some massive object is jettisoned
An ion thruster is systematically switched on and this type of propulsion is only efficient in planetary neighborhood
The velocity vector of the probe is not changed in norm, but in direction in the planetocentric reference frame
Answer key (one line per option, 1 = correct):
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Justification: The norm of the velocity vector stays constant, there is no acceleration in the direction of the velocity vector. However, the direction of the trajectory of the spacecraft in the sphere of influence of the planet is a hyperbola. The direction of the velocity vector changes when the spacecraft is inside the sphere of influence.
Question: What can Gravity-assist be used for? (more than one answer possible)
Options:
Increase the heliocentric velocity, Decrease the heliocentric velocity, Make communications between the probe and Earth easier, Explorations of "worlds" during the transit flight to the destination
Answer key (one line per option, 1 = correct):
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Justification: The most common application of gravity assist is to increase the heliocentric velocity. However, it can be reduced if the direction of the spacecraft velocity vector is well chosen when entering the sphere of influence. Voyager and Pioneer probes took advantage of their multiple gravity assist maneuvers to explore and take close-up images of all the planets in our solar system. This was made possible due to a particularly favorable alignement of the planets.
Question: In space propulsion, what is true about the specific Impulse (Isp)?
Options:
It is expressed in seconds
it changes with the gravity value g
it is an expression of the propulsion system efficiency
It is related to the exhaust velocity
It expresses the impact of the local gravity on the launcher capability to reach orbit.
Answer key (one line per option, 1 = correct):
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Justification: The Isp is related to the exhaust velocity by multiplying its value always by g=9.81. This relation is not dependant on the local value of the gravitational acceleration.
Question: There are various combinations of fuel and oxidizer which exist. Which combination gives the biggest Isp among the following?
Options:
LOX/LH2, N2H4/LOX, N2H4/N2O4, Kerosene/N2O4, MMH/N2O4
Answer key (one line per option, 1 = correct):
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Justification: The LH2/LOX mixture provides an Isp of ~450s in vacuum. It was used for the Space Shuttle main engine and for the Ariane 5 vulcain engine for instance.
Question: Why is electric propulsion system more efficent than chemical propulsion?
Options:
It does not generate heat., It produces a higher exhaust velocity., Because of the recombination of ions and electrons to form neutral atoms., Because of the production of electrodynamics shock waves at the exhaust.
Answer key (one line per option, 1 = correct):
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Question: In the process of Orbit insertion what does MECO refer to?
Options:
Micro-Elliptic Catapult Orbit, Main Engine Cut-Off, It does not mean anything relevant
Answer key (one line per option, 1 = correct):
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Question: Which of the following statements are true?
Options:
LVLH is a coordinate system, LVLH is a french luxury clothing brand, LVLH is an inertial coordinate system, In the LVLH system, the z-axis points towards the center of the Earth, LVLH stands for Local Vertical, Local Horizontal.
Answer key (one line per option, 1 = correct):
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Justification: The LVLH, Local Vertical, Local Horizontal, is a local reference frame which is linked to the Earth's ground. x is in the direction of travel and z towards the center of the Earth.
Question: In orbital manoeuvres, is the order of the Euler sequence commutative? (i.e. can you inverse two or more rotations)
Options:
Yes, No
Answer key (one line per option, 1 = correct):
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Question: How does a magnetic torquer work ?
Options:
The needle of a compass presses on the thruster button to correctly orient the spacecraft
A coil is wrapped around an elongated rod. An electrical current runs through the the coil generating a magnetic field which has the tendency to align itself with Earth's magnetic field
Permanent magnets are placed at strategic places in the spacecraft, keeping it correctly oriented
Answer key (one line per option, 1 = correct):
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Question: Solar arrays should be oriented towards the Sun with a very low accuracy. The angle Theta from the normal of the solar array to the Sun, however, is directly linked to the power generated. Why is the requirement the pointing of the solar arrays to the Sun so loose?
Options:
The power generated is proportional to sine of Theta
The power generated is proportional to the cosine of Theta
The individual solar cells can points each towards the exact direction of the sun
We cannot point a higher precision
Answer key (one line per option, 1 = correct):
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Justification: cos(10°) ~ 0.985, still very close to 1, the supplementary computational, electrical and even consumable needed to increase the power generated by 1 point is not always worth the effort. This lessen also the constraints on the attitude of the spacecraft to give more possibilities to the payload.
Question: Select all propositons that applies to attitude maneuvers with thrusters
Options:
It is the most precise technique, It can be used to desaturate other attitude maneuver systems, 6 thrusters are needed to have pure rotations, A minimum of 12 thrusters are needed to have pure rotations, All thrusters systems need to have a ignition system
Answer key (one line per option, 1 = correct):
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Justification: Thruster is a very simple and quite crude method.
Thrusters are used to desaturate reaction wheels.
12 thrusters (4 per axis) are needed to be able to rotate and brake without translation.
All thrusters systems don't need to have a ignition system:  for example MMH/N2O4 is a hypergolic reaction and does not need an ignition system. For mono-propellant thrusters, the Hydrazine is catalysed on a berilium substrat.
Question: What is the fundamental principle that is used when working with rotation wheels?
Options:
Conservation of momentum, Conservation of angular momentum, Conservation of electric charge, Freedom
Answer key (one line per option, 1 = correct):
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Justification: When the rotation wheel starts to rotate, the spacecraft will counter-rotate in order to conserve its total angular momentum, thanks to this, the attitude of a spacecraft can be modified
Question: What was the main power source of the Space Shuttle?
Options:
Solar arrays
Fuel cells
Radioisotope Thermoelectric Generators (RTG)
Hamsters running in a wheel
Astronaut bicycle ergometer with a generator
Answer key (one line per option, 1 = correct):
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Question: A tether deployed from the Space Shuttle with a passive satellite at the end can be used as ...
Options:
Electrical Generator, Space elevator, Electrical motor, Dipole antenna
Answer key (one line per option, 1 = correct):
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Question: Which effect dominates the forces on a tethered systems?
Options:
Drag disturbances, Radiation pressure, Gravity gradient, Collision with other spacecraft
Answer key (one line per option, 1 = correct):
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Justification: A collision with another spacecraft is very unlikely. The dominant effect is the gravity gradient which tends to align the system along the orbital radius.
Question: What elements were part of selected configuration of the Space Shuttle? (Select all that applies)
Options:
An orbiter, A capsule, 3 main engines, Two solid rocket boosters, An external tank, A third stage
Answer key (one line per option, 1 = correct):
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Question: During which year the Shuttle approach and landing tests took place?
Options:
1974, 1975, 1976, 1977, 1978
Answer key (one line per option, 1 = correct):
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Question: Up to how many crew-members could participate in Space Shuttle Missions?
Options:
2, 5, 7, 10, 11
Answer key (one line per option, 1 = correct):
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Question: Which abbreviations correspond to real Space Shuttle Missions? (Select all that applies)
Options:
STS-1, STS-432, STS-75, STS-51L, STS-137, STS-118
Answer key (one line per option, 1 = correct):
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Justification: STS-1 was the first Shuttle flight in 1981, STS-51L corresponds to the Challenger accident in 1986, STS-75 was Claude Nicollier's third flight in 1996 with a tethered satellite. The last Shuttle flight was STS-135 so STS-137 and STS-432 do not make sense.
Question: What changes did occur after the Challenger accident? (Select all that applies)
Options:
The design of some components of the Space Shuttle Transportation System was modified
Crew to the ISS were sent only with Soyuz spacecraft
The Launch and Entry Suit was introduced
The Shuttle was not used by the Department of Defense or for commercial flights
Nothing
Answer key (one line per option, 1 = correct):
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Question: When did the ISS start to be assembled?
Options:
2001, 1995, 1998, 2011
Answer key (one line per option, 1 = correct):
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Question: Which of the following vehicles were able to bring crews to the ISS, until 2011? (Select all that applies)
Options:
Soyuz, Progress, Dragon, Space Shuttle, Shenzhou
Answer key (one line per option, 1 = correct):
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Justification: Only Soyuz spacecraft and the Space Shuttle were able to bring crews to the ISS. Shenzhou is the Chinese manned spacecraft which have been able to bring Chinese crews onboard the Chinese Space Station. Progress and Dragon are supply vehicles, not manned.
Question: What year did the first spacewalk take place?
Options:
1962, 1963, 1964, 1965
Answer key (one line per option, 1 = correct):
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Justification: The first spacewalk, realized by Alexei Leonov, took place on March 18, 1965 during the Voskhod 2 mission and lasted for 12 minutes.
Question: What new item was introduced in Apollo 15 to explore the Moon?
Options:
A second, scientific, deck to the LEM, A Lunar Roving Vehicle, A tent-like structure to analyze boulders, The spacesuits featured cold gas thrusters to fly small distances
Answer key (one line per option, 1 = correct):
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Justification: The A Lunar Roving Vehicle called "buggy" was electrically powered and was driven on Apollo 15, 16 and 17, the last three flights. During Apollo 17, it was driven on the surface for more than 20 km!
Question: Which of the following is NOT a branch within the European Cooperation for Space Standardization (ECSS) system?
Options:
Policy branch (P-branch)
System description branch (S-branch)
Environmental Sustainability branch (E-branch)
Configuration and information management branch (D-branch)
Answer key (one line per option, 1 = correct):
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Justification: The ECSS system includes several branches that cover a wide range of standardization disciplines, but an Environmental Sustainability branch (E-branch) as described is not one of them. The actual E-branch within ECSS refers to the Engineering branch, which defines standard engineering processes and technical requirements for space systems. The ECSS space sustainability branch (U-branch), was initiated in 2012, and defines two disciplines: space debris mitigation and planetary protection.
Question: Which ECSS standard series focuses specifically on the product assurance aspects of space projects?
Options:
E-branch, S-branch, Q-branch, P-branch
Answer key (one line per option, 1 = correct):
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Justification: The ECSS product assurance branch (Q-branch) defines the methods and requirements relevant to assure the safety and reliability of space products.
Question: The South Atlantic Anomaly (SAA) is an area where the Earth's inner Van Allen radiation belt comes closest to the Earth's surface. What does it lead to?
Options:
A screening from sun light., A decreased flux of energetic particles., An increased flux of energetic particles., A high number of auroras.
Answer key (one line per option, 1 = correct):
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Justification: It leads to an increased flux of energetic particles in this region and exposes orbiting satellites to higher than usual levels of radiation. The effect is caused by the non-concentricity of the Earth and its magnetic dipole.
Question: What might be the effect of the impact of a cosmic ray with the onboard electronics? (More than one answer possible)
Options:
Change the position of the satellite., Create single event upsets., Create single event latchups., Cause the loss of performance of the system.
Answer key (one line per option, 1 = correct):
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Justification: Single-event effects (SEE), mostly affecting only digital devices. When a high-energy particle travels through a semiconductor, it leaves an ionized track behind. This ionization may cause a highly localized effect. Single event upsets can be fixed by rebooting the system while single event latchups create a permanent localised failure, which in turn can result in loss of performance (that's why all electronic component are redundant on satellites).
Question: What causes the difference between the spectral irradiance at the top of the atmosphere and at sea level?
Options:
The passage of airplanes
The presence of water in the atmosphere
The presence of CO2
The high albedo (about 0.9) at the poles
Answer key (one line per option, 1 = correct):
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Justification: A lot of the solar flux is absorbed by different molecules present in the atmosphere. Certain regions of the atmosphere (in the UV for example) are opaque as the water molecule absorb all the available energy at that wavelength.
Question: A probe is leaving the vicinity of Earth to fly to Mercury. Where will the solar panels generate the most power?
Options:
In the vicinity of Earth., Mid-flight from the Earth to Mercury., In the vicinity of Mercury., The distance to the Sun does not matter.
Answer key (one line per option, 1 = correct):
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Justification: The solar irradiance decreases with the square of the distance to the Sun. Closer objects will receive more solar flux, thus more power is generated in the vicinity of Mercury than in the vicinity of Earth.
Question: The Earth receives an almost constant flux from the Sun of S = 1361 W/m^2. Which of the following is correct?
Options:
All the energy received is funnelled to the core of the Earth to keep it at a constant temperature.
The Earth reflects most of the energy received and is kept in its thermal equilibrium by the heat source in its core.
The Earth is in constant shadow due to the multitude of satellites that orbit, such that it is in thermal equilibrium.
The Earth is in thermal equilibrium because some of the heat received is reflected back to space and the Earth radiates away energy, mostly in the IR.
Answer key (one line per option, 1 = correct):
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Justification: There is an Earth energy budget. The input of energy are the Sun irradiance and the internal energy provided by the molten core. Some of the energy of the Sun is immediately reflected off the surface (via the albedo coefficient) and another output is the black body radiation of the Earth that peaks in the IR.
Question: The exterior of a satellite must be covered with a coating. What would be the best choice such that the temperature of the satellite is the lowest possible?
Options:
Gold (alpha = 0.299, epsilon = 0.023)
White Epoxy (alpha = 0.248, epsilon = 0.924)
Titanium (alpha = 0.448, epsilon = 0.129)
Aluminum (alpha = 0.379, epsilon = 0.0346)
Answer key (one line per option, 1 = correct):
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Justification: The best coating is the one that has the lowest alpha/epsilon ratio, because alpha describes the ability of the material to absorb heat while epsilon describes the capacity to radiate heat away. Among the proposed materials white epoxy is the best choice here. It has an alpha/epsilon ratio of about 0.27.
Question: Which modulation method can have a combination of 2 bits per symbol, a code rate of 0.5 and a spectral efficiency of about 1.0
Options:
BPSK, QPSK, 8-PSK, 16-PSK
Answer key (one line per option, 1 = correct):
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Question: Which of the following statements are true about Precipitation Losses for Communication Link Analysis?
Options:
precipitation losses attenuates RF signals by absorption
precipitation losses attenuates RF signals by scattering (depolarization)
Geographic databases of rainfall are needed for link analysis
precipitation losses are inversely proportional to the humidity in the atmosphere
Answer key (one line per option, 1 = correct):
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Justification: Precipitation in the form of rain and wet snow attenuates RF signals through both absorption and scattering (depolarization). Precipitation-induced losses are dependent upon the product of a rate-dependent attenuation coefficient and the path length that the RF signals are required to traverse through rainfall regions within the atmosphere. Because losses are a function of the concentration of water in the atmosphere, precipitation-induced losses are heavily dependent upon a geographic and seasonal variation in weather. To provide a means for predicting rain precipitation effects, the ITU has created a geographic database of rainfall rates. This helps for link analysis.
Question: Which of the following influence the total power at the receive amplifier in communication link analyses?
Options:
EIRP, the Equivalent Isotropic Radiated Power, mu, the Standard gravitational parameter, Ls, the Free-Space Losses, Lin, the input losses to the receiver, Ltx, the transmitter pointing losses, Na, the avogadro number
Answer key (one line per option, 1 = correct):
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Justification: The total power at the receive amplifier can be expressed as C = EIRP + Gr - Ls - Latm - Lprec - Lin - Ltx - Lrx where EIRP is the Equivalent Isotropic Radiated Power, Gr is the gain of the receive antenna, Ls are the free-space losses, Latm and Lprec are the losses due to the atmosphere and precipitation, Lin the input losses to the receiver, Ltx the transmitter pointing losses, and Lrx the depointing losses of the receiver. The standard gravitational parameter has to do with orbital mechanics but not with communication link analysis and the avogadro number is used in chemistry, not in this context.