Lecture 2: Spaceflight

Spaceflight Overview

• Spaceflight involves using technology and science to launch and navigate spacecraft into and through outer space.
• Phases of spaceflight include rocket launching, outer space dynamics, orbital trajectories, and orbital maneuvers.

Rocket Launching

• Rockets provide thrust to overcome Earth’s gravitational force by expelling exhaust gases at high speed (Newton’s third law).
• Rocket engines rely solely on propellant carried within the spacecraft.
• Chemical rockets are the most powerful, utilizing fuel combustion with an oxidizer to create high-speed exhaust.
• Rockets can operate in a vacuum, allowing for more efficiency and reduced atmospheric drag.

Outer Space

• Outer space is the region beyond Earth’s atmosphere, lacking a clear physical boundary.
• The Kármán line, located at 100 km above sea level, marks a conventional boundary of space established by Theodore von Kármán.

Orbital Spaceflight

• Orbital spaceflight occurs when a spacecraft achieves the minimum speed required for a closed orbit around Earth.
• Kepler’s laws describe the orbital paths of spacecraft under the influence of gravity when no engine thrust is present.
• Newton’s laws apply when thrust is utilized; stopping the thrust alters the orbit but allows the application of Kepler’s laws afterward.

Orbital Maneuvers

• An orbital maneuver, or "burn," uses propulsion to adjust a spacecraft's orbit.
• Transfer orbits facilitate movement from one circular orbit to another; they cannot be achieved with a single thrust application.
• Hohmann transfer orbits require two burns to establish a new orbit efficiently.
• Bi-elliptic transfers involve three burns and may use less energy over longer travel times compared to Hohmann maneuvers.

Interplanetary Spaceflight

• Interplanetary spaceflight refers to traveling between planets within the Solar System.
• Movement relative to the Sun significantly impacts spacecraft speed: closer planets require speed increases, while moving away requires decreases.
• Efficient interplanetary travel often utilizes Hohmann transfer orbits and gravity assists to minimize fuel needs.

Applications of Spaceflight

• Current and proposed uses include:
  • Space tourism
  • Satellite deployments
  • Space exploration
  • Earth protection from space hazards
  • Future space colonization

Space Tourism

• Space tourism offers recreational human space travel with categories including orbital, suborbital, and lunar missions.
• Suborbital flights aim to reach space with steep trajectories and return to the launch site.
• Passengers experience weightlessness during free-fall when propulsion is turned off.

Commercial Spaceflights

• Space Adventures provides orbital missions to the International Space Station (ISS).
• SpaceX offers paid flights for private individuals to the ISS.
• The Inspiration4 mission was the first orbital flight with only private citizens aboard, lasting almost three days.

Lunar Tourism

• Future lunar tourism may allow private trips around the Moon for unique views, like the far side and Earthrise.

Environmental Concerns

• Spaceflight generates pollution, mainly through rocket exhaust, which may include greenhouse gases and heavy metals from rocket production.
• Space pollution results from space debris and satellite flare, posing risks to operational spacecraft.
• Spacecraft undergoing atmospheric reentry face mechanical stress due to drag and heating from air compression and friction.

Spaceflight Overview

• Spaceflight involves using technology and science to launch and navigate spacecraft into and through outer space.
• Phases of spaceflight include rocket launching, outer space dynamics, orbital trajectories, and orbital maneuvers.

Rocket Launching

• Rockets provide thrust to overcome Earth’s gravitational force by expelling exhaust gases at high speed (Newton’s third law).
• Rocket engines rely solely on propellant carried within the spacecraft.
• Chemical rockets are the most powerful, utilizing fuel combustion with an oxidizer to create high-speed exhaust.
• Rockets can operate in a vacuum, allowing for more efficiency and reduced atmospheric drag.

Outer Space

• Outer space is the region beyond Earth’s atmosphere, lacking a clear physical boundary.
• The Kármán line, located at 100 km above sea level, marks a conventional boundary of space established by Theodore von Kármán.

Orbital Spaceflight

• Orbital spaceflight occurs when a spacecraft achieves the minimum speed required for a closed orbit around Earth.
• Kepler’s laws describe the orbital paths of spacecraft under the influence of gravity when no engine thrust is present.
• Newton’s laws apply when thrust is utilized; stopping the thrust alters the orbit but allows the application of Kepler’s laws afterward.

Orbital Maneuvers

• An orbital maneuver, or "burn," uses propulsion to adjust a spacecraft's orbit.
• Transfer orbits facilitate movement from one circular orbit to another; they cannot be achieved with a single thrust application.
• Hohmann transfer orbits require two burns to establish a new orbit efficiently.
• Bi-elliptic transfers involve three burns and may use less energy over longer travel times compared to Hohmann maneuvers.

Interplanetary Spaceflight

• Interplanetary spaceflight refers to traveling between planets within the Solar System.
• Movement relative to the Sun significantly impacts spacecraft speed: closer planets require speed increases, while moving away requires decreases.
• Efficient interplanetary travel often utilizes Hohmann transfer orbits and gravity assists to minimize fuel needs.

Applications of Spaceflight

• Current and proposed uses include:
  • Space tourism
  • Satellite deployments
  • Space exploration
  • Earth protection from space hazards
  • Future space colonization

Space Tourism

• Space tourism offers recreational human space travel with categories including orbital, suborbital, and lunar missions.
• Suborbital flights aim to reach space with steep trajectories and return to the launch site.
• Passengers experience weightlessness during free-fall when propulsion is turned off.

Commercial Spaceflights

• Space Adventures provides orbital missions to the International Space Station (ISS).
• SpaceX offers paid flights for private individuals to the ISS.
• The Inspiration4 mission was the first orbital flight with only private citizens aboard, lasting almost three days.

Lunar Tourism

• Future lunar tourism may allow private trips around the Moon for unique views, like the far side and Earthrise.

Environmental Concerns

• Spaceflight generates pollution, mainly through rocket exhaust, which may include greenhouse gases and heavy metals from rocket production.
• Space pollution results from space debris and satellite flare, posing risks to operational spacecraft.
• Spacecraft undergoing atmospheric reentry face mechanical stress due to drag and heating from air compression and friction.

Spaceflight Overview

• Spaceflight utilizes science and technology to transport spacecraft into or through outer space.
• Phases of spaceflight include rocket launching, traversing outer space, achieving orbit, and performing orbital maneuvers.

Rocket Launching

• Rockets provide the necessary thrust to overcome Earth's gravity and launch spacecraft.
• Rocket engines operate by expelling exhaust at high speeds, producing thrust based on Newton's third law.
• Chemical rockets are common, combining fuel with oxidizers to create high-speed exhaust.
• Rockets can operate in a vacuum, performing efficiently without atmospheric drag.

Outer Space

• Defined as the region beyond Earth's atmosphere, lacking a clear physical boundary.
• The Kármán line, set at 100 km above sea level, is often regarded as the boundary of space, named after Theodore von Kármán.

Orbital Spaceflight

• An orbital flight occurs when a spacecraft reaches the speed necessary for a closed orbit around Earth.
• Subject only to gravitational forces, the orbit follows Kepler's laws; thrust modifies the orbit temporarily.

Orbital Maneuvers

• An orbital maneuver, or "burn," involves changing a spacecraft's orbit using its propulsion system.
• Transfer orbits are intermediate elliptical paths used to transition between circular orbits and involve varying energy efficiency.
• The Hohmann transfer orbit requires two engine burns for efficient orbit adjustment.

Gravity Assist

• A gravity assist uses a planet’s orbit to alter a spacecraft’s speed and trajectory, conserving propellant.
• The conservation of momentum applies: the spacecraft gains velocity while the planet minimally loses speed.
• Practical use of gravity assists is limited by the alignment of planets in their orbits.

Applications for Spaceflight

• Spaceflight applications include space tourism, satellite deployment, space exploration, planetary defense, and colonization.

Space Tourism

• Involves recreational human space travel, with options including orbital, suborbital, and lunar tourism.
• Suborbital flights focus on reaching space altitudes, with parts of the flight involving free-fall and weightlessness.
• Orbital flights include missions to the International Space Station (ISS); companies like SpaceX facilitate such missions.

Lunar Tourism

• Future lunar tourism may allow access to the Moon for private audiences, with attractions including views of the far side of the Moon and Earthrise.

Environmental Impact

• Spaceflight contributes to pollution, primarily from greenhouse gases released by rocket exhaust.
• Concerns include space pollution from debris and satellites, which pose hazards to ongoing space activities.
• During atmospheric reentry, spacecraft experience significant mechanical stress and heating.

Summary of Key Concepts

• Interplanetary spaceflight involves the Sun's gravitational influence and utilizes techniques for efficient travel like Hohmann transfer or gravity assists.
• Understanding orbital mechanics and the physical principles governing space travel is crucial for current and future technologies.

This quiz covers the fundamental concepts of spaceflight, including the phases of rocket launching, outer space, orbit, and orbital maneuvers. Understand how science and technology enable us to navigate the cosmos and the principles behind spacecraft propulsion. Test your knowledge on this exciting topic of space exploration.