What is the fundamental definition of a sub-orbital spaceflight?

A sub-orbital spaceflight is a spaceflight where the spacecraft reaches outer space, but its trajectory intersects the surface of the originating body, preventing it from completing a full orbital revolution or achieving escape velocity.

How does a sub-orbital spaceflight differ from an orbital spaceflight?

Unlike an orbital spaceflight, a sub-orbital trajectory does not complete a full revolution around the Earth. This means the spacecraft does not become an artificial satellite and does not attain escape velocity.

What is the Kármán line, and who established it as an altitude threshold for spaceflight?

The Kármán line is an altitude boundary, generally considered to be between 83 and 100 kilometers (52 to 62 miles) above sea level, that is used to define the edge of space. This definition was established by the Fédération Aéronautique Internationale (FAI).

What altitude does the United States military and NASA use to award astronaut wings, and how does this compare to the FAI definition?

The United States military and NASA award astronaut wings to individuals who fly above 50 miles (approximately 80 kilometers) above sea level. This threshold is lower than the FAI's Kármán line definition of 100 kilometers.

What type of orbit does a sub-orbital trajectory follow, and why does it not complete a full orbit?

During freefall, a sub-orbital trajectory is part of an elliptical orbit. It fails to complete a full orbit because its perigee distance is less than the Earth's radius, causing the trajectory to intersect the Earth's surface.

How is the specific orbital energy of a sub-orbital flight mathematically described?

The specific orbital energy (ε) for a sub-orbital flight is given by the formula ε = -μ / (2a), where 'μ' is the standard gravitational parameter and 'a' is the semi-major axis. This value is greater than the minimum energy required for a full orbit, indicating less energy is needed.

What strategy is employed to minimize the delta-v required for sub-orbital flights, and why is this important?

Delta-v, a measure of the change in velocity needed for a spaceflight, is minimized by shutting off the rockets during the high-altitude, free-fall portion of the flight. This strategy reduces the overall fuel consumption required for the mission.

What is the approximate delta-v needed to simply reach an altitude of 100 kilometers?

To reach an altitude of 100 kilometers, the minimum delta-v required is approximately 1.4 kilometers per second.

How does the delta-v requirement for a sub-orbital flight compare to that for achieving a low Earth orbit (LEO)?

Achieving a low Earth orbit at an altitude of about 300 kilometers requires a speed of around 7.7 km/s, translating to a delta-v of approximately 9.2 km/s. This is significantly higher than the delta-v needed for a sub-orbital flight to reach space.

At what point in its trajectory is the maximum speed typically achieved during a sub-orbital flight?

The maximum speed in a sub-orbital flight is generally attained at the lowest altitude point of the free-fall trajectory, which occurs at both the beginning and the end of this phase.

How does the horizontal distance covered in a sub-orbital flight influence its speed and delta-v requirements?

For sub-orbital flights that cover horizontal distance, the maximum speed and required delta-v fall between those of a purely vertical flight and a low Earth orbit. As the horizontal distance increases, the horizontal speed component also increases.

What were the approximate maximum speed and range of the V-2 rocket when it successfully reached space?

The V-2 rocket, which reached space with a range of about 330 kilometers, achieved a maximum speed of 1.6 kilometers per second.

What is the announced maximum speed for the Scaled Composites SpaceShipTwo?

The announced maximum speed for the Scaled Composites SpaceShipTwo is 1.1 kilometers per second, possibly due to its engine shutting off at a higher altitude.

What are the typical maximum speed and altitude for a 10,000-kilometer intercontinental sub-orbital flight?

For a 10,000-kilometer intercontinental flight, such as that of an intercontinental ballistic missile (ICBM), the maximum speed is about 7 km/s, and the maximum altitude can exceed 1300 km.

How does the maximum speed of a sub-orbital flight affect aerodynamic heating during reentry?

The aerodynamic heating experienced during atmospheric reentry is directly related to the speed at the start of reentry. Flights with lower maximum speeds, like 1 km/s, experience significantly less heating compared to those with higher maximum speeds, such as 7 or 8 km/s.

What is the formula for calculating the minimum delta-v (launch speed) for a sub-orbital trajectory covering a distance 'd', neglecting Earth's rotation and atmosphere?

The minimum delta-v, or launch speed, is calculated using the formula: sqrt(2 * μ/R * (sin θ / (1 + sin θ))), where 'μ' is the standard gravitational parameter, 'R' is Earth's radius, and 'θ' is half the angle the projectile travels around the Earth. This can also be expressed as sqrt(2gR * (sin θ / (1 + sin θ))).

How does the required delta-v change as the range of a sub-orbital flight increases?

The required delta-v increases with the range of the sub-orbital flight, eventually leveling off at approximately 7.9 km/s as the range approaches halfway around the Earth (20,000 km).

What initial speed (delta-v) is required for an intercontinental ballistic missile (ICBM) to reach targets at least 5500 kilometers away?

An ICBM requires an initial speed, or delta-v, of at least 6.1 km/s to reach targets located 5500 kilometers away.

How does the amount of fuel needed for a missile relate to its delta-v, according to the Rocket equation?

The amount of fuel required increases exponentially with delta-v. This means that achieving higher delta-v for longer ranges or orbital capabilities necessitates a considerably larger missile and more fuel, as described by the Rocket equation.

What is the optimal initial direction for a minimum-delta-v sub-orbital trajectory, assuming Earth's rotation is ignored?

When Earth's rotation is disregarded, the optimal initial direction for a minimum-delta-v sub-orbital trajectory points halfway between directly upward and towards the destination point, which would be below the horizon.

How is the free-fall time calculated for a purely vertical sub-orbital flight?

For a vertical flight, the time spent in free-fall, both during ascent and descent, is calculated by dividing the maximum speed achieved by the acceleration of gravity (g). For a maximum speed of 1 km/s, this duration is approximately 3 minutes and 20 seconds.

What are the typical durations for the boost and midcourse phases of an intercontinental sub-orbital flight?

The boost phase for an intercontinental sub-orbital flight typically lasts between 3 to 5 minutes, while the subsequent free-fall or midcourse phase lasts approximately 25 minutes.

What happened to the Pioneer 1 probe that caused it to follow a sub-orbital trajectory?

Pioneer 1, NASA's first space probe intended for the Moon, experienced a partial failure that resulted in it following a sub-orbital trajectory. It reentered Earth's atmosphere 43 hours after its launch.

According to Kepler's third law, how is the period of a hypothetical full orbit calculated for a sub-orbital trajectory?

The period of a hypothetical full orbit can be calculated using Kepler's third law, which relates it to the semi-major axis of the trajectory and the period of a low Earth orbit. The formula involves (semi-major axis / R)^(3/2) multiplied by the period of a low Earth orbit.

What formula is used to calculate the time of flight for a minimum-delta-v trajectory?

The time of flight for a minimum-delta-v trajectory can be calculated using a formula derived from Kepler's second law. This formula incorporates terms related to the trajectory angle, Earth's radius, and gravity, often involving arcsin or arccos functions.

Approximately how long would a minimum-delta-v trajectory take to travel a quarter or halfway around the Earth?

A minimum-delta-v trajectory to travel a quarter of the way around the Earth would take approximately 32 minutes, while traveling halfway around would take about 42 minutes.

When and where did the first ballistic missile successfully reach space, and what altitude did it achieve?

The first ballistic missile to reach space was the German V-2, launched from Peenemünde on October 3, 1942. It achieved an altitude of 53 miles (85 kilometers).

What significant milestone did Albert II, a rhesus macaque, achieve in 1949?

Albert II, a rhesus macaque, became the first mammal in space on June 14, 1949. This occurred during a sub-orbital flight aboard a U.S. V-2 sounding rocket that reached an altitude of 83 miles (134 kilometers).

What prize did SpaceShipOne win in 2004 for its flights?

SpaceShipOne won the Ansari X Prize in 2004. This award was secured by successfully completing two flights within a two-week period.

What were Virgin Galactic's initial plans for its SpaceShipTwo vehicle regarding capacity and testing?

Virgin Galactic initially planned for its SpaceShipTwo vehicle to accommodate nine people, including one pilot and six passengers. The vehicle has since undergone captive-carry tests and glide flights.

What event caused a delay in Virgin Galactic's planned commercial flights?

A disaster that occurred during the SpaceShipTwo's PF04 flight caused a delay in Virgin Galactic's commercial flights. The company stated it would learn from the incident to improve safety and performance.

What is a primary current application for sub-orbital vehicles in scientific research?

A major current use for sub-orbital vehicles is as scientific sounding rockets. These vehicles enable researchers to conduct experiments in microgravity environments or to study phenomena above the Earth's atmosphere.

How were early sounding rockets developed from existing missile technology?

In the late 1940s, captured German V-2 ballistic missiles were repurposed and converted into V-2 sounding rockets. This adaptation laid the groundwork for the development of modern sounding rocket technology.

What was the concept behind the X-20 Dyna-Soar project concerning sub-orbital transportation?

Research conducted for the X-20 Dyna-Soar project suggested that a semi-ballistic sub-orbital flight could potentially enable travel between Europe and North America in less than an hour.

What is the SpaceLiner concept, and what are its proposed passenger capacities and travel times?

The SpaceLiner is a conceptual hypersonic suborbital spaceplane designed to transport 50 passengers from Australia to Europe in 90 minutes, or 100 passengers from Europe to California in 60 minutes.

How might SpaceX's Starship vehicle be utilized for transportation purposes?

SpaceX is considering the potential use of its Starship vehicle as a sub-orbital point-to-point transportation system for travel across Earth.

What was the first uncrewed sub-orbital spaceflight, and what altitude did it reach?

The first sub-orbital space flight was conducted by MW 18014, a V-2 test rocket launched from Peenemünde, Germany, on June 20, 1944. It reached an altitude of 176 kilometers.

What altitude and speed did the upper stage of the Bumper 5 rocket achieve in its 1949 flight?

On February 24, 1949, the upper stage of the Bumper 5 rocket reached an altitude of 248 miles (399 km) and attained a speed of 7,553 feet per second (2,302 m/s).

Who piloted the first crewed sub-orbital spaceflight, and on what date did it occur?

Alan Shepard piloted the first crewed sub-orbital spaceflight on May 5, 1961.

How did the X-15 aircraft contribute to sub-orbital spaceflight history?

The X-15 was the first winged craft to reach space. Its Flight 90 on July 19, 1963, piloted by Joseph A. Walker, achieved this milestone.

What event caused the Soyuz 18a mission to be classified as a sub-orbital flight rather than an orbital one?

The Soyuz 18a mission experienced a malfunction during stage separation, leading to an abort of its orbital launch. This resulted in the spacecraft following a sub-orbital trajectory.

What specific achievement by SpaceShipOne secured the Ansari X-Prize?

SpaceShipOne secured the Ansari X-Prize with its flight on October 4, 2004, which was the second of two required flights completed within a two-week period.

Who were the passengers on the inaugural crewed Blue Origin flight, designated NS-16?

The passengers on Blue Origin's NS-16 flight were Jeff Bezos, Mark Bezos, Wally Funk, and Oliver Daemen.

Which Blue Origin mission included William Shatner as a passenger?

William Shatner flew on Blue Origin's NS-18 mission, which took place on October 13, 2021.

What is noted about the rarity of manned vertically-launched suborbital flights prior to the advent of the New Shepard program?

Prior to the first launch of New Shepard, manned vertically launched suborbital flights were infrequent. They often occurred as a result of failures in manned rocket programs intended for orbital spaceflight.

What was the outcome of the STS-51-L mission, commonly known as the Space Shuttle Challenger disaster?

The STS-51-L mission, also referred to as STS-25, tragically ended in the Space Shuttle Challenger disaster on January 28, 1986. All seven astronauts aboard the shuttle were killed.

What were the reported outcomes of Mike Hughes' flights using his self-built rockets?

Mike Hughes sustained injuries during his first self-built rocket flight (Hughes 1). Tragically, he was killed during the crash landing of his third flight (Hughes 3) when the parachute was destroyed at launch.

What caused the Soyuz MS-10 mission to deviate from its intended orbital path and become a sub-orbital flight?

The Soyuz MS-10 mission was forced into a sub-orbital trajectory due to a launch abort caused by a malfunction during stage separation.

Which types of companies are showing interest in sub-orbital spaceflight, and what factors are driving this interest?

Private companies such as Virgin Galactic, Armadillo Aerospace (Exos Aerospace), Airbus, Blue Origin, and Masten Space Systems are showing interest in sub-orbital spaceflight. This interest is partly fueled by initiatives like the Ansari X Prize and the potential for applications like hypersonic aircraft.

What is the primary technical challenge for the SpaceLiner concept?

The main challenge for the SpaceLiner concept is enhancing the reliability of its various components, particularly the engines, to ensure the possibility of daily passenger transportation.

What types of cargo are anticipated to be the initial focus for sub-orbital transportation, given the high costs involved?

Due to the significant costs associated with spaceflight, sub-orbital flights are expected to initially concentrate on delivering high-value, very high-urgency cargo. This includes courier services, rapid military response operations, and space tourism.

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Defining Sub-Orbital Spaceflight

The Trajectory

A sub-orbital spaceflight is a journey where a spacecraft reaches outer space but does not complete a full orbital revolution around the Earth. Its trajectory intersects the planet's surface, preventing it from becoming an artificial satellite or achieving escape velocity.

Altitude Thresholds

The internationally recognized boundary for spaceflight is the Kármán line, approximately 100 km (62 miles) above sea level. However, the U.S. military and NASA often use a lower threshold of 50 miles (80 km) for awarding astronaut status.

Distinction from Orbital

Unlike orbital flights, sub-orbital trajectories are essentially ballistic arcs. They require less velocity and energy but do not provide sustained weightlessness or the ability to orbit the planet. Flights that de-orbit before completing one orbit are not classified as sub-orbital.

Orbital Mechanics & Physics

Trajectory Ellipse

The path of a sub-orbital flight is a segment of an ellipse, dictated by gravitational forces. The trajectory intersects the Earth because its perigee (closest point to Earth) is below the planet's surface, meaning it cannot complete a full orbit.

The specific orbital energy ( $\varepsilon$

Delta-v Requirements

Achieving a sub-orbital trajectory requires significantly less delta-v (change in velocity) compared to orbital flight. For a vertical ascent to the Kármán line, the minimum delta-v is approximately 1.4 km/s. This contrasts sharply with the ~9.2 km/s needed for a low Earth orbit.

The required launch speed ( $\Delta v$ ) is calculated as $\Delta v = \sqrt{2\frac{\mu}{R}\frac{\sin \theta}{1+\sin \theta}}$ , where $\theta$ represents half the angular distance to the target.

Speed and Altitude

The maximum speed during a sub-orbital flight occurs at the lowest point of the trajectory, typically at launch and landing. For longer ranges, the trajectory becomes more elliptical, potentially reaching higher altitudes (e.g., over 1300 km for a 10,000 km flight) but requiring higher speeds (~7 km/s).

The time of flight is calculated using Kepler's laws, with longer flights requiring more complex calculations involving the semi-major axis and the fraction of the orbit covered.

Historical Milestones

Early Pioneers (V-2)

The first vehicles to reach space were sub-orbital ballistic missiles. Germany's V-2 rocket, developed at Peenemünde, achieved an altitude of 85 km on October 3, 1942, marking the dawn of sub-orbital spaceflight. Post-war, captured V-2 technology formed the basis for early U.S. and Soviet sounding rockets and missiles.

The Space Race Era

During the Space Race, sub-orbital flights were critical stepping stones. NASA's Mercury-Redstone missions (MR-3 and MR-4) in 1961 carried Alan Shepard and Gus Grissom into space, respectively. The X-15 rocket plane also achieved spaceflight altitudes multiple times in the 1960s, pioneering winged access to space.

The Ansari X Prize

In 2004, Scaled Composites' SpaceShipOne, piloted by Mike Melvill and Brian Binnie, successfully completed two flights within two weeks, winning the $10 million Ansari X Prize. This event catalyzed the modern era of private sub-orbital space tourism.

Notable Sub-Orbital Flights

Mercury & X-15

The Mercury program's sub-orbital flights (MR-3, MR-4) were crucial for early American human spaceflight. The X-15, a hypersonic research aircraft, reached altitudes above 100 km on several flights, earning its pilots astronaut wings.

Key flights include:

Mercury-Redstone 3 (Freedom 7): May 5, 1961 - Alan Shepard (187.5 km apogee).
Mercury-Redstone 4 (Liberty Bell 7): July 21, 1961 - Gus Grissom (190.3 km apogee).
X-15 Flight 90: July 19, 1963 - Joseph A. Walker (107.9 km apogee).
X-15 Flight 91: August 22, 1963 - Joseph A. Walker (83.2 km apogee).

SpaceShipOne

This pioneering private venture achieved spaceflight three times in 2004, culminating in winning the Ansari X Prize. It demonstrated the feasibility of private sub-orbital transportation.

Flight 15P: June 21, 2004 - Mike Melvill (First commercial spaceflight).
Flight 16P: September 29, 2004 - Mike Melvill (First X-Prize qualifying flight).
Flight 17P: October 4, 2004 - Brian Binnie (Second X-Prize flight).

Modern Commercial Flights

Companies like Blue Origin and Virgin Galactic have revitalized sub-orbital space tourism. Blue Origin's New Shepard and Virgin Galactic's SpaceShipTwo vehicles have successfully carried numerous passengers beyond the Kármán line.

Notable recent flights include:

Blue Origin NS-16: July 20, 2021 (Jeff Bezos, Wally Funk, Oliver Daemen).
Virgin Galactic Unity 22: July 11, 2021 (Richard Branson).
Virgin Galactic Unity 25: May 25, 2023.
Blue Origin NS-25: May 19, 2024.

Diverse Flight Profiles

Ballistic Missiles

Intercontinental Ballistic Missiles (ICBMs) are designed for sub-orbital trajectories, delivering payloads over vast distances. Their flight paths are carefully calculated ballistic arcs, reaching high altitudes before re-entry.

Scientific Sounding Rockets

Uncrewed sounding rockets are vital tools for atmospheric and space research. They carry instruments to altitudes above the dense atmosphere, enabling experiments in microgravity and upper atmospheric studies.

Sub-Orbital Transportation

Concepts like the proposed SpaceLiner envision using sub-orbital spaceplanes for rapid intercontinental travel, potentially cutting journey times significantly. This application faces challenges in cost and operational reliability.

The Future Horizon

Expanding Access

The future of sub-orbital flight points towards increased accessibility for tourism, research, and potentially high-speed cargo delivery. Companies are continuously refining reusable vehicle technology to lower costs and improve safety.

Technological Advancements

Innovations in propulsion, materials science, and autonomous systems are crucial. Concepts like SpaceX's Starship hint at a future where sub-orbital point-to-point travel could become a reality, connecting distant locations on Earth in under an hour.

Global Participation

Beyond established space agencies and private companies, non-profit organizations and university groups are also contributing to sub-orbital research and development, fostering a broader ecosystem of space exploration.

Key Sub-Orbital Projects

Launch Vehicles

Numerous projects have defined the landscape of sub-orbital flight:

V-2 Rocket
Mercury-Redstone
X-15
SpaceShipOne
New Shepard (Blue Origin)
SpaceShipTwo / VSS Unity (Virgin Galactic)
Starship (SpaceX - test flights)
Sounding Rockets (various)

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References

Flights exceeding 80km but not 100km, including those flown by SpaceShipTwo, are recognized as spaceflight by the United States.

"Branson on Virgin Galactic crash: 'Space is hard â but worth it'". CNET. Retrieved August 1, 2015.

A full list of references for this article are available at the Sub-orbital spaceflight Wikipedia page

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Important Considerations

This content has been generated by an AI model, drawing upon publicly available data from Wikipedia. While efforts have been made to ensure accuracy and adherence to the source material, it is intended for educational and informational purposes only.

This is not professional aerospace or physics advice. Users should consult official documentation and qualified experts for any technical, engineering, or safety-critical applications. The information provided should not substitute professional consultation.

The creators are not liable for any inaccuracies, omissions, or actions taken based on the information presented herein.

Ascent Beyond Orbit

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Defining Sub-Orbital Spaceflight 🌌

⬆️ The Trajectory

📏 Altitude Thresholds

⚖️ Distinction from Orbital

Orbital Mechanics & Physics ⚙️

📈 Trajectory Ellipse

⚡ Delta-v Requirements

💨 Speed and Altitude

Historical Milestones 📜

🇩🇪 Early Pioneers (V-2)

🇺🇸 The Space Race Era

🏆 The Ansari X Prize

Notable Sub-Orbital Flights 🛰️

🇺🇸 Mercury & X-15

🏆 SpaceShipOne

⭐ Modern Commercial Flights

Diverse Flight Profiles 🗂️

💣 Ballistic Missiles

🧑‍🔬 Scientific Sounding Rockets

✈️ Sub-Orbital Transportation

The Future Horizon 🔭

📈 Expanding Access

🚀 Technological Advancements

🌐 Global Participation

Key Sub-Orbital Projects 🛠️

🚀 Launch Vehicles

Teacher's Corner 🧑‍🏫

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References

📜 References

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Academic Disclaimer ⚠️

📜 Important Considerations

Dive in with Flashcard Learning!

Defining Sub-Orbital Spaceflight

The Trajectory

Altitude Thresholds

Distinction from Orbital

Orbital Mechanics & Physics

Trajectory Ellipse

Delta-v Requirements

Speed and Altitude

Historical Milestones

Early Pioneers (V-2)

The Space Race Era

The Ansari X Prize

Notable Sub-Orbital Flights

Mercury & X-15

SpaceShipOne

Modern Commercial Flights

Diverse Flight Profiles

Ballistic Missiles

Scientific Sounding Rockets

Sub-Orbital Transportation

The Future Horizon

Expanding Access

Technological Advancements

Global Participation

Key Sub-Orbital Projects

Launch Vehicles

Teacher's Corner

True or False?

Test Your Knowledge!

Gamer's Corner

Discover other topics to study!

References

Feedback & Support

Academic Disclaimer

Important Considerations