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?

Every 12 hours Signup and view all the answers

What unique feature does the Hubble Space Telescope possess?

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

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

CNSA 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?

Four satellites Signup and view all the answers

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

12 to 24 hours 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?

128 minutes 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?

Predictably reliable orbit Signup and view all the answers

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

Hubble Space Telescope Signup and view all the answers

What is the primary purpose of a space station?

To remain in orbit and host humans for extended periods Signup and view all the answers

Which of the following statements is true about GPS satellites?

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

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

It allows for scanning of different geographic areas. Signup and view all the answers

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

To minimize energy costs for placement Signup and view all the answers

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

Between 20,000 and 35,786 kilometers Signup and view all the answers

What unique characteristic defines a geostationary orbit?

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

What is the primary use of geostationary weather satellites?

To monitor Earth's atmosphere and weather continuously. Signup and view all the answers

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

It provides an unobstructed view of Earth and deep space. Signup and view all the answers

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

At least six. Signup and view all the answers

Why are communication satellites typically placed in a geostationary orbit?

To simplify tracking with fixed antennas. Signup and view all the answers

What was the main purpose of the Vela satellites?

To detect nuclear detonations. Signup and view all the answers

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

Exoplanets outside of our solar system. Signup and view all the answers

Which statement about a geosynchronous orbit is true?

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

What caused the phenomenon known as Iridium flares?

The satellite momentarily appearing as a bright object Signup and view all the answers

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

They do not produce flares Signup and view all the answers

What is the purpose of thrusters on the Starlink satellites?

To de-orbit at the end of their life Signup and view all the answers

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

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

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

Collisions between satellites and other objects Signup and view all the answers

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

They can be launched at a lower economic cost Signup and view all the answers

What concerns have astronomers raised regarding satellite constellations like Starlink?

Potential interference with ground-based astronomy recordings Signup and view all the answers

What technological feature allows satellites to avoid collisions in space?

Uplinked tracking data for autonomous adjustments Signup and view all the answers

What is the purpose of a graveyard orbit?

To safely dispose of satellites at the end of their life Signup and view all the answers

How does satellite flare occur?

Due to sunlight reflecting off satellite surfaces Signup and view all the answers

What was a primary criticism of the Iridium satellite constellation?

Contribution to light pollution Signup and view all the answers

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

The atomic number of iridium is 77 Signup and view all the answers

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

Negatively affects ground-based astronomy Signup and view all the answers

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

1997–2002 Signup and view all the answers

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

To demonstrate safe disposal at the end of life Signup and view all the answers

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

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

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

The lack of atmospheric pressure Signup and view all the answers

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

Deterioration of muscle mass Signup and view all the answers

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

Reduced atmospheric pressure Signup and view all the answers

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

18-19 km Signup and view all the answers

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

Gravity decreases gradually Signup and view all the answers

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

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

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

Increased risk of cancer Signup and view all the answers

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

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

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

Rupturing of eardrums and sinuses Signup and view all the answers

Which statement about the composition of the Sun is accurate?

It is primarily composed of hydrogen and helium. Signup and view all the answers

What is the baseline temperature of outer space?

−270 °C Signup and view all the answers

How do greenhouse gases affect Earth's surface temperature?

They insulate Earth from losing heat to space. Signup and view all the answers

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

High levels due to lack of atmosphere Signup and view all the answers

What phenomenon occurs without the greenhouse effect on Earth?

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

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

Ultraviolet radiation Signup and view all the answers

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

It can cause a rupture of the lungs. Signup and view all the answers

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

Free fall due to gravity Signup and view all the answers

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

Spaceflight osteopenia Signup and view all the answers

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

Alpha radiation Signup and view all the answers

How does space travel affect muscle health in astronauts?

Muscle atrophy is minimized with exercise Signup and view all the answers

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

Vacuum conditions 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?

Spaceflight osteopenia Signup and view all the answers

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

Gamma radiation Signup and view all the answers

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

Life support systems controlling temperature and pressure Signup and view all the answers

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

The nebular hypothesis Signup and view all the answers

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

Hydrogen Signup and view all the answers

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

Gravitational compression Signup and view all the answers

Which characteristics define scattered-disc objects?

High orbital eccentricities and inclinations Signup and view all the answers

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

Sedna Signup and view all the answers

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

Increase in angular momentum Signup and view all the answers

Which bodies are generally accepted as dwarf planets besides Pluto?

Haumea, Makemake, and Orcus Signup and view all the answers

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

It causes perturbation and scattering. Signup and view all the answers

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

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

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

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

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

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

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

Accretion of dust grains in a protoplanetary disc. Signup and view all the answers

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

High temperatures prevented the formation of icy bodies. Signup and view all the answers

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

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

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

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

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

They ultimately became the terrestrial planets. Signup and view all the answers

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

Gravitational perturbations from Jupiter Signup and view all the answers

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

Nebular hypothesis Signup and view all the answers

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

They originated from discs around their respective planets Signup and view all the answers

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

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

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

It consists of a sparse population of icy planetesimals Signup and view all the answers

What theory explains the origin of Saturn's rings?

They are fragments of a moon that broke apart Signup and view all the answers

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

Accretion Signup and view all the answers

How did planetesimals in the early Solar System initially form?

Through the merging of smaller particles in a protoplanetary disc Signup and view all the answers

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

Rocket engines Signup and view all the answers

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

Reaction to high-speed exhaust Signup and view all the answers

What is the Kármán line generally recognized as?

A conventional boundary of outer space Signup and view all the answers

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

To create high-speed exhaust through combustion Signup and view all the answers

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

Gradual decrease in air density Signup and view all the answers

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

Absence of surrounding air pressure Signup and view all the answers

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

Newton’s third law Signup and view all the answers

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

Gradual changes in atmospheric density Signup and view all the answers

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

Involve more engine burns and may be more energy-efficient Signup and view all the answers

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

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

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

It leads to extremely high fuel consumption Signup and view all the answers

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

To account for the fuel needed for speed changes during the mission Signup and view all the answers

What defines interplanetary spaceflight?

Travel between the planets of the Solar System Signup and view all the answers

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

To transition into an elliptical orbit Signup and view all the answers

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

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

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

They are generally the most energy-efficient method Signup and view all the answers

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

Attaining the altitude required to qualify as reaching space Signup and view all the answers

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

Weightlessness Signup and view all the answers

What defines an orbital spaceflight?

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

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

SpaceX Signup and view all the answers

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

They become completely invalid while thrust is applied. Signup and view all the answers

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

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

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

To conserve fuel Signup and view all the answers

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

Sub-orbital flights Signup and view all the answers

What is a transfer orbit primarily used for?

To move a spacecraft between two circular orbits. Signup and view all the answers

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

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

What characterizes a Hohmann transfer orbit?

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

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

Space colonization Signup and view all the answers

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

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

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

Sub-orbital tourism Signup and view all the answers

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

It consists of two half-elliptic orbits. Signup and view all the answers

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

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

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

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

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

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

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

8.5 months Signup and view all the answers

What is a gravity assist maneuver primarily used for?

To redirect the spacecraft without consuming additional propellant. Signup and view all the answers

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

The planet loses some velocity. Signup and view all the answers

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

The alignment of the planets is not always ideal. Signup and view all the answers

How long is the synodic period for Mars?

780 days Signup and view all the answers

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

Half of the orbital period of the outer orbit. 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 Satellite Internet

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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