HSI2010 Lect 1-5
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Questions and Answers

What is the primary characteristic of low Earth orbit (LEO)?

  • It is above an altitude of 5,000 km.
  • It allows for the highest communication latency.
  • It is below an altitude of 2,000 km. (correct)
  • It is the most expensive orbit for satellite placement.

    • What type of orbit allows satellites to obtain global coverage while operating at a lower altitude?

  • Polar orbit (correct)
  • Geosynchronous orbit
  • Medium Earth orbit (MEO)
  • Low Earth orbit (LEO)

    • Which of the following is NOT an advantage of low Earth orbit?

  • Easier access for crew and servicing.
  • Suitable for Earth observation satellites.
  • Requires low energy for satellite placement.
  • Provides high communication latency. (correct)

    • How often does a satellite in a semi-synchronous orbit complete one full orbit around the Earth?

    <p>Every 12 hours</p> Signup and view all the answers

    What unique feature does the Hubble Space Telescope possess?

    <p>It captures high-resolution images unaffected by Earth's atmosphere.</p> Signup and view all the answers

    Which organization was NOT one of the collaborating agencies for the International Space Station?

    <p>CNSA</p> Signup and view all the answers

    What is the minimum number of GPS satellites required for a receiver to calculate its own position and time?

    <p>Four satellites</p> Signup and view all the answers

    Which orbital period range do satellites in Medium Earth Orbit (MEO) typically have?

    <p>12 to 24 hours</p> Signup and view all the answers

    How long is the orbital period of a satellite in low Earth orbit, as indicated by Kepler’s third law?

    <p>128 minutes</p> Signup and view all the answers

    What is a defining characteristic of a satellite's orbit that allows it to pass over the same spots every day?

    <p>Predictably reliable orbit</p> Signup and view all the answers

    Which of the following objects is an example of a satellite that operates in low Earth orbit?

    <p>Hubble Space Telescope</p> Signup and view all the answers

    What is the primary purpose of a space station?

    <p>To remain in orbit and host humans for extended periods</p> Signup and view all the answers

    Which of the following statements is true about GPS satellites?

    <p>They carry accurate time and position data and broadcast it continuously.</p> Signup and view all the answers

    What is the significance of the ground track of a satellite moving west with each successive orbit?

    <p>It allows for scanning of different geographic areas.</p> Signup and view all the answers

    What is one of the main reasons satellites are placed in low Earth orbit?

    <p>To minimize energy costs for placement</p> Signup and view all the answers

    What altitude defines the edge of Medium Earth Orbit (MEO)?

    <p>Between 20,000 and 35,786 kilometers</p> Signup and view all the answers

    What unique characteristic defines a geostationary orbit?

    <p>It remains stationary relative to a specific point on Earth.</p> Signup and view all the answers

    What is the primary use of geostationary weather satellites?

    <p>To monitor Earth's atmosphere and weather continuously.</p> Signup and view all the answers

    Which of the following is a benefit of high Earth orbit (HEO)?

    <p>It provides an unobstructed view of Earth and deep space.</p> Signup and view all the answers

    How many satellites are needed to ensure line of sight from anywhere on Earth?

    <p>At least six.</p> Signup and view all the answers

    Why are communication satellites typically placed in a geostationary orbit?

    <p>To simplify tracking with fixed antennas.</p> Signup and view all the answers

    What was the main purpose of the Vela satellites?

    <p>To detect nuclear detonations.</p> Signup and view all the answers

    What does the Transiting Exoplanet Survey Satellite (TESS) specifically search for?

    <p>Exoplanets outside of our solar system.</p> Signup and view all the answers

    Which statement about a geosynchronous orbit is true?

    <p>It matches Earth’s rotation on its axis.</p> Signup and view all the answers

    What caused the phenomenon known as Iridium flares?

    <p>The satellite momentarily appearing as a bright object</p> Signup and view all the answers

    What feature distinguishes the new generation of Iridium satellites from the first generation?

    <p>They do not produce flares</p> Signup and view all the answers

    What is the purpose of thrusters on the Starlink satellites?

    <p>To de-orbit at the end of their life</p> Signup and view all the answers

    How many satellites does the Starlink internet constellation currently plan to deploy?

    <p>6,000 satellites with plans for an extension to 34,400</p> Signup and view all the answers

    What is a primary concern related to the increasing number of satellites in orbit?

    <p>Collisions between satellites and other objects</p> Signup and view all the answers

    Why are smaller satellites being used more frequently in satellite constellations?

    <p>They can be launched at a lower economic cost</p> Signup and view all the answers

    What concerns have astronomers raised regarding satellite constellations like Starlink?

    <p>Potential interference with ground-based astronomy recordings</p> Signup and view all the answers

    What technological feature allows satellites to avoid collisions in space?

    <p>Uplinked tracking data for autonomous adjustments</p> Signup and view all the answers

    What is the purpose of a graveyard orbit?

    <p>To safely dispose of satellites at the end of their life</p> Signup and view all the answers

    How does satellite flare occur?

    <p>Due to sunlight reflecting off satellite surfaces</p> Signup and view all the answers

    What was a primary criticism of the Iridium satellite constellation?

    <p>Contribution to light pollution</p> Signup and view all the answers

    What led to the name 'Iridium' for the Iridium satellite constellation?

    <p>The atomic number of iridium is 77</p> Signup and view all the answers

    What impact does light pollution from satellite flares have on scientific endeavors?

    <p>Negatively affects ground-based astronomy</p> Signup and view all the answers

    What is the duration during which the first-generation Iridium satellites were deployed?

    <p>1997–2002</p> Signup and view all the answers

    What is a key requirement imposed by the ITU on satellite designers?

    <p>To demonstrate safe disposal at the end of life</p> Signup and view all the answers

    What is the role of reflective antennas on first-generation satellites?

    <p>To focus sunlight on a small area of Earth's surface</p> Signup and view all the answers

    What is the primary danger posed by the vacuum of outer space to humans?

    <p>The lack of atmospheric pressure</p> Signup and view all the answers

    What physiological effect can result from prolonged exposure to weightlessness in space?

    <p>Deterioration of muscle mass</p> Signup and view all the answers

    Which factor causes the boiling point of water to decrease in outer space?

    <p>Reduced atmospheric pressure</p> Signup and view all the answers

    At what altitude does the Armstrong limit occur, where bodily liquids can boil away?

    <p>18-19 km</p> Signup and view all the answers

    How does gravity change with increasing altitude above Earth's surface?

    <p>Gravity decreases gradually</p> Signup and view all the answers

    Which of the following statements best describes the nature of Earth's atmosphere?

    <p>It is a mixture of gases retained by gravity.</p> Signup and view all the answers

    What is a significant hazard astronauts face due to radiation exposure in outer space?

    <p>Increased risk of cancer</p> Signup and view all the answers

    How does the temperature in outer space compare to the temperatures experienced on Earth?

    <p>Outer space has both extreme heat and cold depending on proximity to celestial bodies</p> Signup and view all the answers

    What is one of the main consequences of sudden exposure to a vacuum for unprotected humans?

    <p>Rupturing of eardrums and sinuses</p> Signup and view all the answers

    Which statement about the composition of the Sun is accurate?

    <p>It is primarily composed of hydrogen and helium.</p> Signup and view all the answers

    What is the baseline temperature of outer space?

    <p>−270 °C</p> Signup and view all the answers

    How do greenhouse gases affect Earth's surface temperature?

    <p>They insulate Earth from losing heat to space.</p> Signup and view all the answers

    What level of exposure to radiation do astronauts face in outer space?

    <p>High levels due to lack of atmosphere</p> Signup and view all the answers

    What phenomenon occurs without the greenhouse effect on Earth?

    <p>An average surface temperature of about −18 °C</p> Signup and view all the answers

    What radiation constitutes about 10% of the total electromagnetic radiation output from the Sun?

    <p>Ultraviolet radiation</p> Signup and view all the answers

    What detrimental effect can very low pressure in space have on the human body?

    <p>It can cause a rupture of the lungs.</p> Signup and view all the answers

    What primary factor causes the sensation of weightlessness for an astronaut in orbit?

    <p>Free fall due to gravity</p> Signup and view all the answers

    Which of the following is a significant health risk related to long-term exposure to weightlessness for astronauts?

    <p>Spaceflight osteopenia</p> Signup and view all the answers

    What type of radiation is stopped by a sheet of paper?

    <p>Alpha radiation</p> Signup and view all the answers

    How does space travel affect muscle health in astronauts?

    <p>Muscle atrophy is minimized with exercise</p> Signup and view all the answers

    What challenging environmental hazard is encountered during human exploration of outer space?

    <p>Vacuum conditions</p> Signup and view all the answers

    What is the term used to describe the deterioration of muscles and skeleton observed in astronauts during long space missions?

    <p>Spaceflight osteopenia</p> Signup and view all the answers

    Which type of radiation consists of energetic electromagnetic radiation and requires dense materials for shielding?

    <p>Gamma radiation</p> Signup and view all the answers

    What is necessary for a spacecraft to maintain acceptable living conditions for astronauts in space?

    <p>Life support systems controlling temperature and pressure</p> Signup and view all the answers

    What is the widely accepted model to explain the formation of the Solar System?

    <p>The nebular hypothesis</p> Signup and view all the answers

    Which element made up the majority of the mass of the early Solar System?

    <p>Hydrogen</p> Signup and view all the answers

    What process results in the center of the collapsing nebula becoming increasingly hotter?

    <p>Gravitational compression</p> Signup and view all the answers

    Which characteristics define scattered-disc objects?

    <p>High orbital eccentricities and inclinations</p> Signup and view all the answers

    Which of the following is classified as an extreme trans-Neptunian object?

    <p>Sedna</p> Signup and view all the answers

    What was the main effect of gravitational collapse in the early solar nebula?

    <p>Increase in angular momentum</p> Signup and view all the answers

    Which bodies are generally accepted as dwarf planets besides Pluto?

    <p>Haumea, Makemake, and Orcus</p> Signup and view all the answers

    What effect does the gravitational interaction of gas giants have on scattered-disc objects?

    <p>It causes perturbation and scattering.</p> Signup and view all the answers

    What role did solar wind play in the formation of the Solar System?

    <p>It helped clear away gas and dust in the protoplanetary disc.</p> Signup and view all the answers

    How did rocky planetesimals differ from icy planetesimals in the formation of planets?

    <p>Rocky planetesimals were formed where temperatures were too high for volatiles to condense.</p> Signup and view all the answers

    Which of the following correctly describes the formation of gas giant planets?

    <p>They captured hydrogen and helium before the solar wind cleared the disc.</p> Signup and view all the answers

    What process is primarily responsible for the formation of planets in the early Solar System?

    <p>Accretion of dust grains in a protoplanetary disc.</p> Signup and view all the answers

    Why did the inner Solar System consist mainly of terrestrial planets?

    <p>High temperatures prevented the formation of icy bodies.</p> Signup and view all the answers

    What was a consequence of the colliding and merging of protoplanets in the inner Solar System?

    <p>They ultimately became the terrestrial planets.</p> Signup and view all the answers

    What effect did the strong solar wind from the young Sun have on planetary formation?

    <p>It removed much of the gas and dust left in the protoplanetary disc.</p> Signup and view all the answers

    What was a significant factor in the growth of the giant planets?

    <p>The abundance of ices available in the outer Solar System.</p> Signup and view all the answers

    What primarily caused the disruption of planetesimals in the asteroid belt?

    <p>Gravitational perturbations from Jupiter</p> Signup and view all the answers

    Which hypothesis explains the formation of the Solar System, including the planets and moons?

    <p>Nebular hypothesis</p> Signup and view all the answers

    What is a characteristic feature of the moons around Jupiter and Saturn?

    <p>They originated from discs around their respective planets</p> Signup and view all the answers

    What event is thought to have led to the formation of Earth's moon?

    <p>A large head-on collision with a Mars-sized body</p> Signup and view all the answers

    What distinguishes the trans-Neptunian region of the Solar System?

    <p>It consists of a sparse population of icy planetesimals</p> Signup and view all the answers

    What theory explains the origin of Saturn's rings?

    <p>They are fragments of a moon that broke apart</p> Signup and view all the answers

    Which process describes the gradual accumulation of material into larger bodies in the context of planet formation?

    <p>Accretion</p> Signup and view all the answers

    How did planetesimals in the early Solar System initially form?

    <p>Through the merging of smaller particles in a protoplanetary disc</p> Signup and view all the answers

    What provides the initial thrust to overcome Earth's gravity during rocket launching?

    <p>Rocket engines</p> Signup and view all the answers

    Which characteristic of rockets allows them to accelerate in the vacuum of space?

    <p>Reaction to high-speed exhaust</p> Signup and view all the answers

    What is the Kármán line generally recognized as?

    <p>A conventional boundary of outer space</p> Signup and view all the answers

    What is the main function of an oxidizer in a chemical rocket?

    <p>To create high-speed exhaust through combustion</p> Signup and view all the answers

    What phenomenon occurs at the Kármán line that affects flight characteristics?

    <p>Gradual decrease in air density</p> Signup and view all the answers

    What is a primary reason rockets work more efficiently in a vacuum compared to the atmosphere?

    <p>Absence of surrounding air pressure</p> Signup and view all the answers

    Which law explains the operation of rocket engines expelling exhaust to generate thrust?

    <p>Newton’s third law</p> Signup and view all the answers

    Why does outer space lack a well-defined physical boundary?

    <p>Gradual changes in atmospheric density</p> Signup and view all the answers

    What is a key characteristic of bi-elliptic transfers compared to Hohmann transfers?

    <p>Involve more engine burns and may be more energy-efficient</p> Signup and view all the answers

    What happens to a spacecraft as it moves farther from the Sun?

    <p>It slows down due to the Sun's gravitational pull</p> Signup and view all the answers

    What is the primary disadvantage of using brute force acceleration in interplanetary travel?

    <p>It leads to extremely high fuel consumption</p> Signup and view all the answers

    Why is more fuel needed when launching a spacecraft into orbit for interplanetary travel?

    <p>To account for the fuel needed for speed changes during the mission</p> Signup and view all the answers

    What defines interplanetary spaceflight?

    <p>Travel between the planets of the Solar System</p> Signup and view all the answers

    What is the role of the second burn in a Hohmann transfer?

    <p>To transition into an elliptical orbit</p> Signup and view all the answers

    What must a spacecraft do to intercept a planet closer to the Sun?

    <p>Decrease its speed relative to the Sun by a large amount</p> Signup and view all the answers

    What is one of the main reasons Hohmann transfer orbits have been traditionally used for economical interplanetary travel?

    <p>They are generally the most energy-efficient method</p> Signup and view all the answers

    What is a primary focus of sub-orbital tourist flights?

    <p>Attaining the altitude required to qualify as reaching space</p> Signup and view all the answers

    What phenomenon do passengers experience during the free fall portion of a spacecraft's journey?

    <p>Weightlessness</p> Signup and view all the answers

    What defines an orbital spaceflight?

    <p>A spaceflight in which a spacecraft remains in space for at least one orbit.</p> Signup and view all the answers

    Which space tourism company offers orbital flights to the International Space Station?

    <p>SpaceX</p> Signup and view all the answers

    How do Kepler’s laws of planetary motion apply to a spacecraft under thrust?

    <p>They become completely invalid while thrust is applied.</p> Signup and view all the answers

    What effect does applying thrust in the direction of a spacecraft's motion have on its orbit?

    <p>It creates an elliptical orbit that is larger than the original.</p> Signup and view all the answers

    Why are rockets turned off during the high-altitude phase of a sub-orbital flight?

    <p>To conserve fuel</p> Signup and view all the answers

    What type of space tourism flight returns to the launch site after reaching space?

    <p>Sub-orbital flights</p> Signup and view all the answers

    What is a transfer orbit primarily used for?

    <p>To move a spacecraft between two circular orbits.</p> Signup and view all the answers

    Which of the following describes the term 'gravity assist' in space travel?

    <p>Using a planet's gravity to increase spacecraft speed</p> Signup and view all the answers

    What characterizes a Hohmann transfer orbit?

    <p>It involves two impulsive engine burns to establish and adjust a transfer orbit.</p> Signup and view all the answers

    What is one of the main applications for current and proposed spaceflight technologies?

    <p>Space colonization</p> Signup and view all the answers

    What happens when thrust is applied at only one point in a spacecraft’s orbit?

    <p>It will return to the same point on each subsequent orbit while altering its path.</p> Signup and view all the answers

    Which aspect of space tourism involves movement toward the edge of space without achieving orbit?

    <p>Sub-orbital tourism</p> Signup and view all the answers

    What distinguishes a bi-elliptic transfer from other transfer methods?

    <p>It consists of two half-elliptic orbits.</p> Signup and view all the answers

    What is the result of applying thrust in the opposite direction of a spacecraft's motion?

    <p>It creates a smaller elliptical orbit than the original circular orbit.</p> Signup and view all the answers

    What is essential for a spacecraft to successfully reach its destination planet?

    <p>The spacecraft must be launched while the planets are aligned.</p> Signup and view all the answers

    What does the synodic period represent in relation to planetary travel?

    <p>The duration it takes for two planets to align again.</p> Signup and view all the answers

    What is the approximate travel time for a spacecraft using a Hohmann transfer from Earth to Mars?

    <p>8.5 months</p> Signup and view all the answers

    What is a gravity assist maneuver primarily used for?

    <p>To redirect the spacecraft without consuming additional propellant.</p> Signup and view all the answers

    What happens to the velocity of a planet when a spacecraft performs a gravity assist?

    <p>The planet loses some velocity.</p> Signup and view all the answers

    What is a major limitation of performing a gravity assist maneuver?

    <p>The alignment of the planets is not always ideal.</p> Signup and view all the answers

    How long is the synodic period for Mars?

    <p>780 days</p> Signup and view all the answers

    What does a Hohmann transfer utilize to reach its destination planet?

    <p>Half of the orbital period of the outer orbit.</p> Signup and view all the answers

    Study Notes

    Satellite Overview

    • A satellite is an object, often a spacecraft, placed into orbit around Earth.
    • Satellites are classified based on altitude: Low Earth Orbit (LEO), Medium Earth Orbit (MEO), Geosynchronous Orbit (GSO), and High Earth Orbit (HEO).

    Low Earth Orbit (LEO)

    • LEO is defined as the area below an altitude of 2,000 km, approximately one-third of Earth’s radius.
    • The International Space Station (ISS) orbits within this region, completing a revolution in about 128 minutes.
    • Advantages include low energy requirements for placement, low communication latency, and easier accessibility for servicing.
    • Notable applications include the Hubble Space Telescope, space stations, and communication satellites.

    Hubble Space Telescope

    • HST is a highly versatile space telescope, capturing high-resolution images away from Earth's atmospheric distortion.
    • Designed for maintenance in space, Hubble has undergone five servicing missions for repairs and upgrades.
    • Launched in 1990 with a flawed mirror, corrective optics were installed during a servicing mission in 1993.

    Space Stations

    • Space stations host humans for extended durations and are primarily research facilities.
    • The ISS is a collaborative effort involving NASA, Roscosmos, ESA, JAXA, and CSA, emphasizing international cooperation.

    Earth Observation Satellites

    • Earth observation satellites operate in LEO to obtain clear images of the Earth's surface.
    • A polar orbit enables global coverage by shifting ground tracks with each orbit.

    Medium Earth Orbit (MEO)

    • MEO is the region above LEO and below geosynchronous orbit, characterized by orbital periods between 2 to 24 hours.
    • GPS operates in this region, utilizing a semi-synchronous orbit with a 12-hour orbital period for predictable coverage.

    Global Positioning System (GPS)

    • GPS provides geolocation services by requiring signals from at least four satellites for location triangulation.
    • The constellation comprises 24 to 32 satellites arranged to ensure at least six are visible from any point on Earth.

    Geosynchronous Orbit (GSO)

    • GSO matches Earth's rotation period, allowing satellites to stay over the same point on Earth.
    • A geostationary orbit, a special form of GSO, maintains a fixed position relative to the Earth’s surface.

    Communication and Weather Satellites

    • Communications satellites benefit from geostationary positions, allowing static antenna alignment.
    • Weather satellites monitor climate patterns continuously from geostationary orbits.

    High Earth Orbit (HEO)

    • HEO lies beyond geosynchronous orbit and offers an unobstructed view for astronomical studies.
    • The Vela satellites were developed for nuclear detection, serendipitously being the first to observe gamma-ray bursts.

    International Telecommunication Union (ITU)

    • ITU mandates that satellite designers demonstrate safe disposal methods, such as controlled atmospheric reentry or placing satellites in graveyard orbits.

    Satellite Flare and Light Pollution

    • Satellite flares occur due to sunlight reflection off satellite surfaces, briefly appearing as bright flashes visible from Earth.
    • The Iridium constellation became a prominent source of light pollution affecting astronomers.

    Iridium Satellite Constellation

    • Operated by Iridium Communications, this constellation includes 66 active satellites in LEO for global coverage.
    • Original satellites deployed (1997-2002) caused significant flares; the newer generation has resolved this issue.
    • Starlink, operated by SpaceX, consists of over 6,000 satellites planned to expand to nearly 12,000.
    • Small satellites reduce launch costs and can be more effective for communication purposes.
    • SpaceX has developed de-orbiting technologies for the satellites and designed them to avoid collisions autonomously.

    Astronomy Concerns

    • The proliferation of satellite constellations, such as Starlink, raises concerns among astronomers regarding impacts on ground-based observations due to increased light pollution.

    Astronaut in Orbit

    • Astronauts in orbit experience free fall, feeling only the force of gravity.
    • Orbital speed enables maintenance of orbit while creating a sensation of weightlessness.

    Weightlessness

    • Lack of normal force between the astronaut and surrounding objects results in weightlessness.
    • Close objects in space appear to float due to simultaneous free fall.

    Human Health Effects

    • Long-term exposure to weightlessness leads to muscle atrophy and spaceflight osteopenia, marking significant health risks.
    • Humans evolved in Earth’s gravity; absence of this force negatively impacts physiology.

    Challenges of Outer Space

    • Outer space poses hazards such as vacuum conditions, extreme temperatures, and radiation.
    • Weightlessness adversely affects human physiology, necessitating protective technology.

    Spacecraft and Spacesuit Technologies

    • Spacecraft and spacesuits provide necessary protection from harsh environmental conditions.
    • Life support systems ensure a supply of air, temperature maintenance, and pressure regulation.

    Radiation Shielding

    • Various types of radiation require different shielding:
      • Alpha radiation (helium nucleus) can be stopped by paper.
      • Beta radiation (electrons) is halted by aluminum.
      • Gamma radiation (high-energy electromagnetic radiation) requires dense materials for absorption.

    Exercise Regimen

    • Regular exercise can mitigate the effects of muscle atrophy and spaceflight osteopenia in astronauts.

    Outer Space Characteristics

    • Constitutes a near-perfect vacuum presenting immediate dangers due to lack of pressure.
    • Very low temperatures, reaching baseline levels around −270 °C, complicate exploration.

    Earth and Gravity

    • Earth is the only known astronomical body that supports life.
    • Gravity diminishes with altitude as one ascends above the Earth’s surface.

    Earth’s Atmosphere

    • The atmosphere consists of a gas mixture retained by Earth’s gravity, essential for supporting life.
    • Atmospheric density and pressure decrease as altitude increases.

    Boiling Point of Water

    • Water boils at 100 °C at Earth’s standard atmospheric pressure.
    • Boiling point lowers at lower pressure, impacting liquid behavior in space.

    Armstrong Limit

    • The Armstrong limit is the altitude at which atmospheric pressure is low enough that bodily fluids boil at body temperature, approximately 18-19 km above sea level.

    Effects of Low Pressure

    • Exposed to very low pressure in space, unprotected humans can experience lung rupture and other severe physical consequences due to pressure differentials.

    Environmental Conditions in Space

    • Outer space maintains very low temperatures and is permeated by radiation, increasing risk for astronauts.

    Sun and Energy

    • The Sun, mainly composed of hydrogen and helium, radiates energy primarily as light.

    Earth’s Atmospheric Composition

    • Earth’s atmosphere consists of approximately 78% nitrogen, 21% oxygen, and small amounts of greenhouse gases like carbon dioxide and water vapor.

    Greenhouse Effect

    • Greenhouse gases trap heat, preventing loss to space and raising Earth’s average temperature to about 15 °C, rather than a much colder −18 °C without this effect.

    Exposure to Radiation

    • Astronauts are exposed to high levels of radiation beyond Earth’s protective atmosphere and magnetic field, necessitating shielding for safety.

    Protoplanetary Disc and Formation of the Solar System

    • A contracting nebula flattened into a spinning protoplanetary disc due to competing forces of gravity and rotation, forming a hot protosun at the center.
    • Centrifugal force acts radially outward from the axis of rotation of the protosun.
    • The core of the Sun reached high temperature and density, initiating hydrogen fusion, leading to energy production.

    Accretion Process

    • Planets formed from the protoplanetary disc via accretion, starting as dust grains in orbit around the protosun.
    • Dust grains clustered together to form clumps, which collided to create larger bodies known as planetesimals.

    Planet Formation

    • In the inner Solar System, the temperature was too high for volatile molecules, resulting in rocky planetesimals composed of metals and silicates.
    • Beyond the frost line (between Mars and Jupiter), conditions allowed volatile icy compounds to remain solid, forming icy planetesimals.
    • Icy bodies beyond the frost line eventually grew into giant planets, capturing significant amounts of hydrogen and helium due to their size.

    Solar Wind and Its Effects

    • The early Sun emitted a strong solar wind that expelled gas and dust from the protoplanetary disc into interstellar space, terminating planet growth.
    • Uranus and Neptune formed later when much of the disc material had already been lost, leading to their accumulation of limited hydrogen and helium.

    Terrestrial and Other Planets

    • The inner Solar System's protoplanets, comprised of rocky materials, merged through collisions to form the four terrestrial planets.
    • Metals and rocky silicates were scarce, limiting the size of terrestrial planets.
    • Both the asteroid belt and Kuiper belt contain many small bodies, including Ceres and Pluto, which are significant trans-Neptunian objects.

    Dwarf Planets and Scattered Disc

    • Other recognized dwarf planets include Haumea, Makemake, Quaoar, and Orcus.
    • Scattered-disc objects exhibit high orbital eccentricities and inclinations due to gravitational scattering by gas giants.
    • Eris is noted as the largest scattered-disc object and most massive dwarf planet, alongside Gonggong.

    Extreme Trans-Neptunian Objects

    • Objects with very large orbits are categorized as extreme trans-Neptunian objects.
    • Sedna was the first extreme trans-Neptunian object discovered and is classified as a dwarf planet.

    Nebular Hypothesis

    • The nebular hypothesis posits the Solar System formed from the gravitational collapse of a giant cloud (presolar nebula).
    • This region had a mass just over that of the Sun, composed primarily of hydrogen and helium, with heavier elements making up 2% of its mass.
    • As the nebula collapsed, it spun faster due to angular momentum conservation, causing its center to heat up due to gravitational energy conversion.

    Asteroids and Trans-Neptunian Region

    • The asteroid belt formed from planetesimals disrupted by Jupiter's gravitational influence, with Ceres as its largest surviving body.
    • Beyond Neptune lies the trans-Neptunian region, sparsely populated by icy planetesimals.

    Moons and Their Formation

    • Most planetary moons formed through one of a few mechanisms; Earth's moon likely formed from a head-on collision that ejected material into orbit.
    • The large moons of Jupiter and Saturn may have developed from discs around these giant planets, analogous to the formation of planets.
    • Theories regarding Saturn's rings suggest they may be remnants of a disintegrated moon or leftover material from Saturn's formation.

    Summary of the Solar System

    • The Solar System includes the Sun, planets, moons, dwarf planets, and small bodies, all formed under the nebular hypothesis framework.

    Spaceflight Overview

    • Spaceflight utilizes science and technology to launch spacecraft into or through outer space.
    • Key phases of spaceflight: rocket launching, outer space travel, orbital travel, and orbital maneuvers.

    Rocket Launching

    • Achieved by rocket launching, which provides the necessary thrust to overcome Earth's gravity.
    • Rocket engines generate thrust through the expulsion of exhaust at high speed, in accordance with Newton’s third law.
    • Rockets use propellant stored within the vehicle and can function in a vacuum without air.

    Propellant and Fuel

    • Chemical rockets, the most common, burn fuel with an oxidizer to produce high-speed exhaust.
    • Rockets operate more efficiently in space, while atmospheric drag reduces thrust on Earth.

    Outer Space

    • Outer space is the region beyond Earth's atmosphere, lacking a definitive physical boundary.
    • The Kármán line, positioned at 100 km above sea level, is the conventional boundary of space, named after Theodore von Kármán.

    Orbital Spaceflight

    • Involves placing a spacecraft on a trajectory to remain in orbit, requiring minimal orbital speed.
    • Kepler’s laws of planetary motion apply when a spacecraft is influenced only by gravitational forces.
    • Orbital changes occur through thrust application; stopping thrust reverts to motion governed by Kepler’s laws.

    Orbital Maneuver

    • An orbital maneuver, or burn, adjusts a spacecraft's orbit using propulsion.
    • A transfer orbit is an intermediate trajectory facilitating movement between circular orbits, utilizing energy efficiently.

    Types of Transfer Orbits

    • Hohmann Transfer Orbit: Employs two engine burns to transition from one orbit to another, efficient for interplanetary travel.
    • Bi-Elliptic Transfer: Involves three burns to achieve a desired orbit, potentially requiring less total energy than Hohmann transfers.

    Interplanetary Spaceflight

    • Refers to travel between planets in the Solar System, influenced by gravitational dynamics.
    • Spacecraft must adjust speed based on proximity to the Sun and other celestial bodies to save fuel.

    Launch Windows and Synodic Period

    • Launch windows depend on the alignment of planets, defined by the synodic period, which indicates when two planets align for optimal travel.
    • For Mars, the synodic period is approximately 780 days, impacting the timing of expeditions.

    Gravity Assist

    • A technique where a spacecraft uses a planet's gravity to alter its speed and trajectory, conserving propellant.
    • The planet experiences a minuscule loss in velocity due to the conservation of momentum.

    Spaceflight Applications

    • Current and proposed spaceflight applications include:
      • Space tourism
      • Satellite operations
      • Space exploration
      • Earth protection from hazardous objects
      • Space colonization initiatives

    Space Tourism

    • Involves human space travel for leisure, encompassing orbital, suborbital, and lunar journeys.
    • Sub-orbital flights aim to reach space altitude and return to the launch site, typically using a steep ascent.

    Weightlessness in Space Tourism

    • During sub-orbital flights, spacecraft achieve free fall to minimize fuel usage, creating a weightless experience for passengers.
    • Passengers experience weightlessness, appearing to float inside the spacecraft.

    Orbital Tourist Flights

    • Companies like Space Adventures and SpaceX offer orbital flights to the International Space Station, catering to private individuals.

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    Related Documents

    02 Spaceflight - Part 1 PDF
    Satellite Orbits PDF
    04 Outer Space PDF
    Solar System Lecture 5 PDF

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