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A sub-orbital spaceflight is a
spaceflight Spaceflight (or space flight) is an application of astronautics to fly spacecraft into or through outer space, either with or without humans on board. Most spaceflight is uncrewed and conducted mainly with spacecraft such as satellites in ...
in which the
spacecraft A spacecraft is a vehicle or machine designed to fly in outer space. A type of artificial satellite, spacecraft are used for a variety of purposes, including communications, Earth observation, meteorology, navigation, space colonization, ...
reaches
outer space Outer space, commonly shortened to space, is the expanse that exists beyond Earth and its atmosphere and between celestial bodies. Outer space is not completely empty—it is a near-perfect vacuum containing a low density of particles, pred ...
, but its
trajectory A trajectory or flight path is the path that an object with mass in motion follows through space as a function of time. In classical mechanics, a trajectory is defined by Hamiltonian mechanics via canonical coordinates; hence, a complete traje ...
intersects the
atmosphere An atmosphere () is a layer of gas or layers of gases that envelop a planet, and is held in place by the gravity of the planetary body. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A s ...
or surface of the gravitating body from which it was launched, so that it will not complete one
orbit In celestial mechanics, an orbit is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space such as a ...
al revolution (it does not become an
artificial satellite A satellite or artificial satellite is an object intentionally placed into orbit in outer space. Except for passive satellites, most satellites have an electricity generation system for equipment on board, such as solar panels or radioiso ...
) or reach
escape velocity In celestial mechanics, escape velocity or escape speed is the minimum speed needed for a free, non- propelled object to escape from the gravitational influence of a primary body, thus reaching an infinite distance from it. It is typically s ...
. For example, the path of an object launched from
Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...
that reaches the
Kármán line The Kármán line (or von Kármán line ) is an attempt to define a boundary between Earth's atmosphere and outer space, and offers a specific definition set by the Fédération aéronautique internationale (FAI), an international record-keeping ...
(at ) above
sea level Mean sea level (MSL, often shortened to sea level) is an average surface level of one or more among Earth's coastal bodies of water from which heights such as elevation may be measured. The global MSL is a type of vertical datuma standardised g ...
), and then falls back to Earth, is considered a sub-orbital spaceflight. Some sub-orbital flights have been undertaken to test spacecraft and
launch vehicle A launch vehicle or carrier rocket is a rocket designed to carry a payload (spacecraft or satellites) from the Earth's surface to outer space. Most launch vehicles operate from a launch pads, supported by a launch control center and system ...
s later intended for
orbital spaceflight An orbital spaceflight (or orbital flight) is a spaceflight in which a spacecraft is placed on a trajectory where it could remain in space for at least one orbit. To do this around the Earth, it must be on a free trajectory which has an altit ...
. Other vehicles are specifically designed only for sub-orbital flight; examples include crewed vehicles, such as the
X-15 The North American X-15 is a hypersonic rocket-powered aircraft. It was operated by the United States Air Force and the National Aeronautics and Space Administration as part of the X-plane series of experimental aircraft. The X-15 set speed an ...
and
SpaceShipOne SpaceShipOne is an experimental air-launched rocket-powered aircraft with sub-orbital spaceflight capability at speeds of up to 3,000 ft/s (900 m/s, 3240 km/h), using a hybrid rocket motor. The design features a unique "feathering" at ...
, and uncrewed ones, such as ICBMs and
sounding rocket A sounding rocket or rocketsonde, sometimes called a research rocket or a suborbital rocket, is an instrument-carrying rocket designed to take measurements and perform scientific experiments during its sub-orbital flight. The rockets are used to ...
s. Flights which attain sufficient velocity to go into
low Earth orbit A low Earth orbit (LEO) is an orbit around Earth with a period of 128 minutes or less (making at least 11.25 orbits per day) and an eccentricity less than 0.25. Most of the artificial objects in outer space are in LEO, with an altitude never ...
, and then
de-orbit Atmospheric entry is the movement of an object from outer space into and through the gases of an atmosphere of a planet, dwarf planet, or natural satellite. There are two main types of atmospheric entry: ''uncontrolled entry'', such as the entr ...
before completing their first full orbit, are not considered sub-orbital. Examples of this include
Yuri Gagarin Yuri Alekseyevich Gagarin; Gagarin's first name is sometimes transliterated as ''Yuriy'', ''Youri'', or ''Yury''. (9 March 1934 – 27 March 1968) was a Soviet pilot and cosmonaut who became the first human to journey into outer space. Tr ...
's
Vostok 1 Vostok 1 (russian: link=no, Восток, ''East'' or ''Orient'' 1) was the first spaceflight of the Vostok programme and the first human spaceflight, human orbital spaceflight in history. The Vostok 3KA space capsule was launched from Baikonur ...
, and flights of the
Fractional Orbital Bombardment System A Fractional Orbital Bombardment System (FOBS) is a warhead delivery system that uses a low earth orbit towards its target destination. Just before reaching the target, it deorbits through a retrograde engine burn. Mark ZastrowHow does China’s ...
. A flight that does not reach space is still sometimes called suborbital, but is not a 'suborbital spaceflight'. Usually a rocket is used, but experimental sub-orbital spaceflight has also been achieved with a
space gun Space Gun may refer to: * Space gun, a method of launching an object into space * ''Space Gun'' (album), a 2018 album by Guided by Voices * ''Space Gun'' (video game), a 1990 arcade game * Ljutic Space Gun, a 12 gauge single-shot shotgun See also * ...
.


Altitude requirement

By one definition a sub-orbital spaceflight reaches an
altitude Altitude or height (also sometimes known as depth) is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object. The exact definition and reference datum varies according to the context ...
higher than above
sea level Mean sea level (MSL, often shortened to sea level) is an average surface level of one or more among Earth's coastal bodies of water from which heights such as elevation may be measured. The global MSL is a type of vertical datuma standardised g ...
. This altitude, known as the Kármán line, was chosen by the
Fédération Aéronautique Internationale The (; FAI; en, World Air Sports Federation) is the world governing body for air sports, and also stewards definitions regarding human spaceflight. It was founded on 14 October 1905, and is headquartered in Lausanne, Switzerland. It maintai ...
because it is roughly the point where a
vehicle A vehicle (from la, vehiculum) is a machine that transports people or cargo. Vehicles include wagons, bicycles, motor vehicles (motorcycles, cars, trucks, buses, mobility scooters for disabled people), railed vehicles (trains, trams), wat ...
flying fast enough to support itself with
aerodynamic lift A fluid flowing around an object exerts a force on it. Lift is the component of this force that is perpendicular to the oncoming flow direction. It contrasts with the drag force, which is the component of the force parallel to the flow directi ...
from the
Earth's atmosphere The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing for ...
would be flying faster than
orbital speed In gravitationally bound systems, the orbital speed of an astronomical body or object (e.g. planet, moon, artificial satellite, spacecraft, or star) is the speed at which it orbits around either the barycenter or, if one body is much more mass ...
. The US military and NASA award
astronaut wings The United States Astronaut Badge is a badge of the United States, awarded to military and civilian personnel who have completed training and performed a successful spaceflight. A variation of the astronaut badge is also issued to civilians who ...
to those flying above , although the
U.S. State Department The United States Department of State (DOS), or State Department, is an executive department of the U.S. federal government responsible for the country's foreign policy and relations. Equivalent to the ministry of foreign affairs of other na ...
appears not to support a distinct boundary between atmospheric flight and
spaceflight Spaceflight (or space flight) is an application of astronautics to fly spacecraft into or through outer space, either with or without humans on board. Most spaceflight is uncrewed and conducted mainly with spacecraft such as satellites in ...
.


Orbit

During freefall the trajectory is part of an
elliptic orbit In astrodynamics or celestial mechanics, an elliptic orbit or elliptical orbit is a Kepler orbit with an eccentricity of less than 1; this includes the special case of a circular orbit, with eccentricity equal to 0. In a stricter sense, it ...
as given by the
orbit equation In astrodynamics, an orbit equation defines the path of orbiting body m_2\,\! around central body m_1\,\! relative to m_1\,\!, without specifying position as a function of time. Under standard assumptions, a body moving under the influence of a f ...
. The
perigee An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. For example, the apsides of the Earth are called the aphelion and perihelion. General description There are two apsides in any el ...
distance is less than the radius of the Earth ''R'' including atmosphere, hence the
ellipse In mathematics, an ellipse is a plane curve surrounding two focal points, such that for all points on the curve, the sum of the two distances to the focal points is a constant. It generalizes a circle, which is the special type of ellipse in ...
intersects the Earth, and hence the spacecraft will fail to complete an orbit. The major axis is vertical, the
semi-major axis In geometry, the major axis of an ellipse is its longest diameter: a line segment that runs through the center and both foci, with ends at the two most widely separated points of the perimeter. The semi-major axis (major semiaxis) is the long ...
''a'' is more than ''R''/2. The
specific orbital energy In the gravitational two-body problem, the specific orbital energy \varepsilon (or vis-viva energy) of two orbiting bodies is the constant sum of their mutual potential energy (\varepsilon_p) and their total kinetic energy (\varepsilon_k), divide ...
\epsilon is given by: \varepsilon = - > -\,\! where \mu\,\! is the
standard gravitational parameter In celestial mechanics, the standard gravitational parameter ''μ'' of a celestial body is the product of the gravitational constant ''G'' and the mass ''M'' of the bodies. For two bodies the parameter may be expressed as G(m1+m2), or as GM when ...
. Almost always ''a'' < ''R'', corresponding to a lower \epsilon than the minimum for a full orbit, which is -\,\! Thus the net extra specific energy needed compared to just raising the spacecraft into space is between 0 and \mu \over\,\!.


Speed, range, and altitude

To minimize the required
delta-v Delta-''v'' (more known as "change in velocity"), symbolized as ∆''v'' and pronounced ''delta-vee'', as used in spacecraft flight dynamics, is a measure of the impulse per unit of spacecraft mass that is needed to perform a maneuver such as ...
(an astrodynamical measure which strongly determines the required
fuel A fuel is any material that can be made to react with other substances so that it releases energy as thermal energy or to be used for work. The concept was originally applied solely to those materials capable of releasing chemical energy bu ...
), the high-altitude part of the flight is made with the
rocket A rocket (from it, rocchetto, , bobbin/spool) is a vehicle that uses jet propulsion to accelerate without using the surrounding air. A rocket engine produces thrust by reaction to exhaust expelled at high speed. Rocket engines work entirely f ...
s off (this is technically called free-fall even for the upward part of the trajectory). (Compare with
Oberth effect In astronautics, a powered flyby, or Oberth maneuver, is a maneuver in which a spacecraft falls into a gravitational well and then uses its engines to further accelerate as it is falling, thereby achieving additional speed. The resulting maneuve ...
.) The maximum
speed In everyday use and in kinematics, the speed (commonly referred to as ''v'') of an object is the magnitude of the change of its position over time or the magnitude of the change of its position per unit of time; it is thus a scalar quanti ...
in a flight is attained at the lowest altitude of this free-fall trajectory, both at the start and at the end of it. If one's goal is simply to "reach space", for example in competing for the Ansari X Prize, horizontal motion is not needed. In this case the lowest required delta-v, to reach 100 km altitude, is about 1.4  km/s. Moving slower, with less free-fall, would require more delta-v. Compare this with orbital spaceflights: a low Earth orbit (LEO), with an altitude of about 300 km, needs a speed around 7.7 km/s, requiring a delta-v of about 9.2 km/s. (If there were no atmospheric drag the theoretical minimum delta-v would be 8.1 km/s to put a craft into a 300-km high orbit starting from a stationary point like the South Pole. The theoretical minimum can be up to 0.46 km/s less if launching eastward from near the equator.) For sub-orbital spaceflights covering a horizontal distance the maximum speed and required delta-v are in between those of a vertical flight and a LEO. The maximum speed at the lower ends of the trajectory are now composed of a horizontal and a vertical component. The higher the horizontal
distance Distance is a numerical or occasionally qualitative measurement of how far apart objects or points are. In physics or everyday usage, distance may refer to a physical length or an estimation based on other criteria (e.g. "two counties over"). ...
covered, the greater the horizontal speed will be. (The vertical velocity will increase with distance for short distances but will decrease with distance at longer distances.) For the
V-2 rocket The V-2 (german: Vergeltungswaffe 2, lit=Retaliation Weapon 2), with the technical name ''Aggregat 4'' (A-4), was the world’s first long-range guided ballistic missile. The missile, powered by a liquid-propellant rocket engine, was develop ...
, just reaching space but with a range of about 330 km, the maximum speed was 1.6 km/s. Scaled Composites SpaceShipTwo which is under development will have a similar free-fall orbit but the announced maximum speed is 1.1 km/s (perhaps because of engine shut-off at a higher altitude). For larger ranges, due to the elliptic orbit the maximum altitude can be much more than for a LEO. On a 10,000-km intercontinental flight, such as that of an intercontinental ballistic missile or possible future
commercial spaceflight Private spaceflight is spaceflight or the development of spaceflight technology that is conducted and paid for by an entity other than a government agency. In the early decades of the Space Age, the government space agencies of the Soviet Uni ...
, the maximum speed is about 7 km/s, and the maximum altitude may be more than 1300 km. Any
spaceflight Spaceflight (or space flight) is an application of astronautics to fly spacecraft into or through outer space, either with or without humans on board. Most spaceflight is uncrewed and conducted mainly with spacecraft such as satellites in ...
that returns to the surface, including sub-orbital ones, will undergo atmospheric reentry. The speed at the start of the reentry is basically the maximum speed of the flight. The
aerodynamic heating Aerodynamic heating is the heating of a solid body produced by its high-speed passage through air. In science and engineering, an understanding of aerodynamic heating is necessary for predicting the behaviour of meteoroids which enter the earth's ...
caused will vary accordingly: it is much less for a flight with a maximum speed of only 1 km/s than for one with a maximum speed of 7 or 8 km/s. The minimum delta-v and the corresponding maximum altitude for a given range can be calculated, ''d'', assuming a spherical Earth of circumference and neglecting the Earth's rotation and atmosphere. Let θ be half the angle that the projectile is to go around the Earth, so in degrees it is 45°×''d''/. The minimum-delta-v trajectory corresponds to an ellipse with one focus at the centre of the Earth and the other at the point halfway between the launch point and the destination point (somewhere inside the Earth). (This is the orbit that minimizes the semi-major axis, which is equal to the sum of the distances from a point on the orbit to the two foci. Minimizing the semi-major axis minimizes the
specific orbital energy In the gravitational two-body problem, the specific orbital energy \varepsilon (or vis-viva energy) of two orbiting bodies is the constant sum of their mutual potential energy (\varepsilon_p) and their total kinetic energy (\varepsilon_k), divide ...
and thus the delta-v, which is the speed of launch.) Geometrical arguments lead then to the following (with ''R'' being the radius of the Earth, about 6370 km): \text = (1 + \sin\theta)R \text = R\sqrt = \sqrt \text = \frac(1 + \sin\theta + \cos\theta) \text = \left(\frac - \sin^2\frac\right)R = \left(\frac\sin\left(\theta + \frac\right) - \frac\right)R Note that the altitude of apogee is maximized (at about 1320 km) for a trajectory going one quarter of the way around the Earth (). Longer ranges will have lower apogees in the minimal-delta-v solution. \text = \frac - \frac\mu\text = \frac\frac \Delta v = \text = \sqrt = \sqrt (where ''g'' is the acceleration of gravity at the Earth's surface). The Δ''v'' increases with range, leveling off at 7.9 km/s as the range approaches (halfway around the world). The minimum-delta-v trajectory for going halfway around the world corresponds to a circular orbit just above the surface (of course in reality it would have to be above the atmosphere). See lower for the time of flight. An
intercontinental ballistic missile An intercontinental ballistic missile (ICBM) is a ballistic missile with a range greater than , primarily designed for nuclear weapons delivery (delivering one or more thermonuclear warheads). Conventional, chemical, and biological weapons ...
is defined as a missile that can hit a target at least 5500 km away, and according to the above formula this requires an initial speed of 6.1 km/s. Increasing the speed to 7.9 km/s to attain any point on Earth requires a considerably larger missile because the amount of fuel needed goes up exponentially with delta-v (see
Rocket equation A rocket (from it, rocchetto, , bobbin/spool) is a vehicle that uses jet propulsion to accelerate without using the surrounding air. A rocket engine produces thrust by reaction to exhaust expelled at high speed. Rocket engines work entirely fr ...
). The initial direction of a minimum-delta-v trajectory points halfway between straight up and straight toward the destination point (which is below the horizon). Again, this is the case if the Earth's rotation is ignored. It is not exactly true for a rotating planet unless the launch takes place at a pole.


Flight duration

In a vertical flight of not too high altitudes, the time of the free-fall is both for the upward and for the downward part the maximum speed divided by the acceleration of gravity, so with a maximum speed of 1 km/s together 3 minutes and 20 seconds. The duration of the
flight Flight or flying is the process by which an object moves through a space without contacting any planetary surface, either within an atmosphere (i.e. air flight or aviation) or through the vacuum of outer space (i.e. spaceflight). This can ...
phases before and after the free-fall can vary. For an intercontinental flight the
boost phase A ballistic missile goes through several distinct phases of flight that are common to almost all such designs. They are, in order: * boost phase when the main boost rocket or upper stages are firing; * post-boost phase when any last-minute changes t ...
takes 3 to 5 minutes, the free-fall (midcourse phase) about 25 minutes. For an ICBM the atmospheric reentry phase takes about 2 minutes; this will be longer for any soft landing, such as for a possible future commercial flight. Sub-orbital flights can last from just seconds to days.
Pioneer 1 Pioneer 1 (also known as Able 2) was an American space probe, the first under the auspices of NASA, which was launched by a Thor-Able rocket on 11 October 1958. It was intended to orbit the Moon and make scientific measurements, but due to a ...
was NASA's first
space probe A space probe is an artificial satellite that travels through space to collect scientific data. A space probe may orbit Earth; approach the Moon; travel through interplanetary space; flyby, orbit, or land or fly on other planetary bodies; o ...
, intended to reach the
Moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width ...
. A partial failure caused it to instead follow a sub-orbital trajectory, reentering the Earth's atmosphere 43 hours after launch. To calculate the time of flight for a minimum-delta-v trajectory, according to
Kepler's third law In astronomy, Kepler's laws of planetary motion, published by Johannes Kepler between 1609 and 1619, describe the orbits of planets around the Sun. The laws modified the heliocentric theory of Nicolaus Copernicus, replacing its circular orbits ...
, the period for the entire orbit (if it didn't go through the Earth) would be: \text = \left(\frac\right)^\frac \times \text = \left(\frac2\right)^\frac2\pi\sqrt Using
Kepler's second law In astronomy, Kepler's laws of planetary motion, published by Johannes Kepler between 1609 and 1619, describe the orbits of planets around the Sun. The laws modified the heliocentric theory of Nicolaus Copernicus, replacing its circular orbits ...
, we multiply this by the portion of the area of the ellipse swept by the line from the centre of the Earth to the projectile: \text = \frac\arcsin\sqrt + \frac \begin \text &= \left(\left(\frac2\right)^\frac\arcsin\sqrt + \frac\cos\theta\sqrt\right)2\sqrt\frac \\ &= \left(\left(\frac2\right)^\frac\arccos\frac + \frac\cos\theta\sqrt\right)2\sqrt\frac \\ \end This gives about 32 minutes for going a quarter of the way around the Earth, and 42 minutes for going halfway around. For short distances, this expression is
asymptotic In analytic geometry, an asymptote () of a curve is a line such that the distance between the curve and the line approaches zero as one or both of the ''x'' or ''y'' coordinates tends to infinity. In projective geometry and related contexts, ...
to \sqrt. From the form involving arccosine, the derivative of the time of flight with respect to ''d'' (or θ) goes to zero as ''d'' approaches (halfway around the world). The derivative of Δ''v'' also goes to zero here. So if ''d'' = , the length of the minimum-delta-v trajectory will be about , but it will take only a few seconds less time than the trajectory for ''d'' = (for which the trajectory is long).


Flight profiles

While there are a great many possible sub-orbital flight profiles, it is expected that some will be more common than others.


Ballistic missiles

The first sub-orbital vehicles which reached space were
ballistic missiles A ballistic missile is a type of missile that uses projectile motion to deliver warheads on a target. These weapons are guided only during relatively brief periods—most of the flight is unpowered. Short-range ballistic missiles stay within the ...
. The very first ballistic missile to reach space was the German V-2, the work of the scientists at
Peenemünde Peenemünde (, en, "Peene iverMouth") is a municipality on the Baltic Sea island of Usedom in the Vorpommern-Greifswald district in Mecklenburg-Vorpommern, Germany. It is part of the '' Amt'' (collective municipality) of Usedom-Nord. The commu ...
, on October 3, 1942 which reached an altitude of . Then in the late 1940s the US and
USSR The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, it was nominally a federal union of fifteen nation ...
concurrently developed missiles all of which were based on the V-2 Rocket, and then much longer range Intercontinental Ballistic Missiles (ICBMs). There are now many countries who possess ICBMs and even more with shorter range Intermediate Range Ballistic Missiles (IRBMs).


Tourist flights

Sub-orbital tourist flights will initially focus on attaining the altitude required to qualify as reaching space. The flight path will be either vertical or very steep, with the spacecraft landing back at its take-off site. The spacecraft will shut off its
engine An engine or motor is a machine designed to convert one or more forms of energy into mechanical energy. Available energy sources include potential energy (e.g. energy of the Earth's gravitational field as exploited in hydroelectric power gene ...
s well before reaching maximum altitude, and then coast up to its highest point. During a few minutes, from the point when the engines are shut off to the point where the atmosphere begins to slow down the downward acceleration, the passengers will experience
weightlessness Weightlessness is the complete or near-complete absence of the sensation of weight. It is also termed zero gravity, zero G-force, or zero-G. Weight is a measurement of the force on an object at rest in a relatively strong gravitational fie ...
.
Megaroc Megaroc was a British proposal for an crewed suborbital derivative of the V2 proposed by R A Smith of the British Interplanetary Society. The proposal was sent to the British Ministry of Supply on 23 December 1946. Though slightly smaller the ...
had been planned for sub-orbital spaceflight by the
British Interplanetary Society The British Interplanetary Society (BIS), founded in Liverpool in 1933 by Philip E. Cleator, is the oldest existing space advocacy organisation in the world. Its aim is exclusively to support and promote astronautics and space exploration. Stru ...
in the 1940s. In the autumn of 1945, the group M. Tikhonravov K. and N. G. Chernysheva at NII-4 rocket artillery Academy of Sciences technology on its own initiative the first stratospheric rocket project was developed by VR-190 for vertical flight two pilots to an altitude of 200 km based on captured German ballistic rocket V-2. In 2004, a number of companies worked on vehicles in this class as entrants to the Ansari X Prize competition. The
Scaled Composites SpaceShipOne SpaceShipOne is an experimental air-launched rocket-powered aircraft with sub-orbital spaceflight capability at speeds of up to 3,000 ft/s (900 m/s, 3240 km/h), using a hybrid rocket motor. The design features a unique "feathering" at ...
was officially declared by Rick Searfoss to have won the competition on October 4, 2004 after completing two flights within a two-week period. In 2005,
Sir Richard Branson Sir Richard Charles Nicholas Branson (born 18 July 1950) is a British billionaire, entrepreneur, and business magnate. In the 1970s he founded the Virgin Group, which today controls more than 400 companies in various fields. Branson expressed ...
of the
Virgin Group Virgin Group Ltd. is a British multinational venture capital conglomerate founded by Richard Branson and Nik Powell in February 1970. Virgin Group's date of incorporation is listed as 1989 by the Companies House, who class it as a holding ...
announced the creation of
Virgin Galactic Virgin Galactic is an American spaceflight company founded by Richard Branson and his British Virgin Group retains an 11.9% stake through Virgin Investments Limited. It is headquartered in California, and operates from New Mexico. The company i ...
and his plans for a 9-seat capacity SpaceShipTwo named VSS ''Enterprise''. It has since been completed with eight seats (one pilot, one co-pilot and six passengers) and has taken part in captive-carry tests and with the first mother-ship WhiteKnightTwo, or VMS ''Eve''. It has also completed solitary glides, with the movable tail sections in both fixed and "feathered" configurations. The
hybrid rocket A hybrid-propellant rocket is a rocket with a rocket motor that uses rocket propellants in two different phases: one solid and the other either gas or liquid. The hybrid rocket concept can be traced back to the early 1930s. Hybrid rockets avoi ...
motor has been fired multiple times in ground-based test stands, and was fired in a powered flight for the second time on 5 September 2013. Four additional SpaceShipTwos have been ordered and will operate from the new
Spaceport America Spaceport America, formerly the Southwest Regional Spaceport, is an FAA-licensed spaceport located on of State Trust Land in the Jornada del Muerto desert basin north of Las Cruces, New Mexico, and southeast of Truth or Consequences. With ...
. Commercial flights carrying passengers were expected in 2014, but became cancelled due to the disaster during SS2 PF04 flight. Branson stated, " are going to learn from what went wrong, discover how we can improve safety and performance and then move forwards together."


Scientific experiments

A major use of sub-orbital vehicles today is as
scientific Science is a systematic endeavor that builds and organizes knowledge in the form of testable explanations and predictions about the universe. Science may be as old as the human species, and some of the earliest archeological evidence f ...
sounding rocket A sounding rocket or rocketsonde, sometimes called a research rocket or a suborbital rocket, is an instrument-carrying rocket designed to take measurements and perform scientific experiments during its sub-orbital flight. The rockets are used to ...
s. Scientific sub-orbital flights began in the 1920s when
Robert H. Goddard Robert Hutchings Goddard (October 5, 1882 – August 10, 1945) was an American engineer, professor, physicist, and inventor who is credited with creating and building the world's first liquid-fueled rocket. Goddard successfully lau ...
launched the first
liquid fuel Liquid fuels are combustible or energy-generating molecules that can be harnessed to create mechanical energy, usually producing kinetic energy; they also must take the shape of their container. It is the fumes of liquid fuels that are flammable ...
ed rockets, however they did not reach
space Space is the boundless three-dimensional extent in which objects and events have relative position and direction. In classical physics, physical space is often conceived in three linear dimensions, although modern physicists usually con ...
altitude. In the late 1940s, captured German V-2 ballistic missiles were converted into
V-2 sounding rocket German V-2 rockets captured by the United States Army at the end of World War II were used as sounding rockets to carry scientific instruments into the Earth's upper atmosphere at White Sands Missile Range (WSMR) for a program of atmospheric and ...
s which helped lay the foundation for modern sounding rockets. Today there are dozens of different sounding rockets on the market, from a variety of suppliers in various countries. Typically, researchers wish to conduct experiments in
microgravity The term micro-g environment (also μg, often referred to by the term microgravity) is more or less synonymous with the terms '' weightlessness'' and ''zero-g'', but emphasising that g-forces are never exactly zero—just very small (on the ...
or above the atmosphere.


Sub-orbital transportation

Research, such as that done for the
X-20 Dyna-Soar The Boeing X-20 Dyna-Soar ("Dynamic Soarer") was a United States Air Force (USAF) program to develop a spaceplane that could be used for a variety of military missions, including aerial reconnaissance, bombing, space rescue, satellite mainten ...
project suggests that a semi-ballistic sub-orbital flight could travel from Europe to North America in less than an hour. However, the size of rocket, relative to the payload, necessary to achieve this, is similar to an ICBM. ICBMs have delta-v's somewhat less than orbital; and therefore would be somewhat cheaper than the costs for reaching orbit, but the difference is not large. Thus due to the high cost, this is likely to be initially limited to high value, very high urgency cargo such as
courier A courier is a person or organisation that delivers a message, package or letter from one place or person to another place or person. Typically, a courier provides their courier service on a commercial contract basis; however, some couriers are ...
flights, or as the ultimate
business jet A business jet, private jet, or bizjet is a jet aircraft designed for transporting small groups of people. Business jets may be adapted for other roles, such as the evacuation of casualties or express parcel deliveries, and some are used by pub ...
; or possibly as an
extreme sport Action sports, adventure sports or extreme sports are activities perceived as involving a high degree of risk. These activities often involve speed, height, a high level of physical exertion and highly specialized gear. Extreme tourism overl ...
, or for
military A military, also known collectively as armed forces, is a heavily armed, highly organized force primarily intended for warfare. It is typically authorized and maintained by a sovereign state, with its members identifiable by their distin ...
fast-response. The
SpaceLiner SpaceLiner is a concept for a suborbital, hypersonic, winged passenger supersonic transport, conceived at the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt, or DLR) in 2005. In its second role the SpaceLiner is intended as ...
is a hypersonic suborbital spaceplane concept that could transport 50 passengers from Australia to Europe in 90 minutes or 100 passengers from Europe to
California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the mo ...
in 60 minutes. The main challenge lies in increasing the reliability of the different components, particularly the engines, in order to make their use for passenger transportation on a daily basis possible.
SpaceX Space Exploration Technologies Corp. (SpaceX) is an American spacecraft manufacturer, launcher, and a satellite communications corporation headquartered in Hawthorne, California. It was founded in 2002 by Elon Musk with the stated goal o ...
is potentially considering using their
Starship A starship, starcraft, or interstellar spacecraft is a theoretical spacecraft designed for interstellar travel, traveling between planetary systems. The term is mostly found in science fiction. Reference to a "star-ship" appears as early as 188 ...
as a sub-orbital point-to-point transport.


Notable uncrewed sub-orbital spaceflights

* The first sub-orbital space flight was on 20 June, 1944, when MW 18014, a V-2 test rocket, launched from
Peenemünde Peenemünde (, en, "Peene iverMouth") is a municipality on the Baltic Sea island of Usedom in the Vorpommern-Greifswald district in Mecklenburg-Vorpommern, Germany. It is part of the '' Amt'' (collective municipality) of Usedom-Nord. The commu ...
in Germany and reached 176 kilometres altitude. * Bumper 5, a two-stage rocket launched from the White Sands Proving Grounds. On 24 February 1949 the upper stage reached an altitude of and a speed of . * Albert II, a male
rhesus macaque The rhesus macaque (''Macaca mulatta''), colloquially rhesus monkey, is a species of Old World monkey. There are between six and nine recognised subspecies that are split between two groups, the Chinese-derived and the Indian-derived. Generally b ...
, became the first mammal in space on 14 June 1949 in a sub-orbital flight from
Holloman Air Force Base Holloman Air Force Base is a United States Air Force base established in 1942 located six miles (10 km) southwest of the central business district of Alamogordo, and a census-designated place in Otero County, New Mexico, United States. Th ...
in New Mexico to an altitude of 83 miles (134 km) aboard a U.S.
V-2 sounding rocket German V-2 rockets captured by the United States Army at the end of World War II were used as sounding rockets to carry scientific instruments into the Earth's upper atmosphere at White Sands Missile Range (WSMR) for a program of atmospheric and ...
. * USSR —
Energia Energia or Energiya may refer to: * Energia (corporation), or S. P. Korolev Rocket and Space Corporation Energia, a Russian design bureau and manufacturer ** Energia (rocket) Energia (russian: Энергия, Energiya, Energy; GRAU 11K25) was a ...
, 15 May 1987, a Polyus payload which failed to reach orbit; this was the most massive object launched into sub-orbital spaceflight to date.


Crewed sub-orbital spaceflights

Above 100 km (62.14 mi) in altitude.


Future of crewed sub-orbital spaceflight

Private companies such as
Virgin Galactic Virgin Galactic is an American spaceflight company founded by Richard Branson and his British Virgin Group retains an 11.9% stake through Virgin Investments Limited. It is headquartered in California, and operates from New Mexico. The company i ...
,
Armadillo Aerospace Armadillo Aerospace was an aerospace startup company based in Mesquite, Texas. Its initial goal was to build a crewed suborbital spacecraft capable of space tourism, and it had also stated long-term ambitions of orbital spaceflight. The company ...
(reinvented as Exos Aerospace),
Airbus Airbus SE (; ; ; ) is a European multinational aerospace corporation. Airbus designs, manufactures and sells civil and military aerospace products worldwide and manufactures aircraft throughout the world. The company has three divisions: '' ...
,
Blue Origin Blue Origin, LLC is an American privately funded aerospace manufacturer and sub-orbital spaceflight services company headquartered in Kent, Washington. Founded in 2000 by Jeff Bezos, the founder and executive chairman of Amazon, the company i ...
and
Masten Space Systems Masten Space Systems was an aerospace manufacturer startup company in Mojave, California (formerly in Santa Clara, California) that was developing a line of vertical takeoff, vertical landing (VTVL) rockets, initially for uncrewed research su ...
are taking an interest in sub-orbital spaceflight, due in part to ventures like the Ansari X Prize. NASA and others are experimenting with
scramjet A scramjet (supersonic combustion ramjet) is a variant of a ramjet airbreathing jet engine in which combustion takes place in supersonic airflow. As in ramjets, a scramjet relies on high vehicle speed to compress the incoming air forcefully ...
based
hypersonic In aerodynamics, a hypersonic speed is one that exceeds 5 times the speed of sound, often stated as starting at speeds of Mach 5 and above. The precise Mach number at which a craft can be said to be flying at hypersonic speed varies, since ind ...
aircraft which may well be used with flight profiles that qualify as sub-orbital spaceflight.
Non-profit A nonprofit organization (NPO) or non-profit organisation, also known as a non-business entity, not-for-profit organization, or nonprofit institution, is a legal entity organized and operated for a collective, public or social benefit, in co ...
entities like ARCASPACE and
Copenhagen Suborbitals Copenhagen Suborbitals is an amateur, crowd-funded, and open-source human space program. Since its beginning in 2008, Copenhagen Suborbitals has flown five home-built rockets and two mock-up space capsules. Their stated goal is to have one of th ...
also attempt
rocket A rocket (from it, rocchetto, , bobbin/spool) is a vehicle that uses jet propulsion to accelerate without using the surrounding air. A rocket engine produces thrust by reaction to exhaust expelled at high speed. Rocket engines work entirely f ...
-based launches.


See also

* Canadian Arrow *
CORONA Corona (from the Latin for 'crown') most commonly refers to: * Stellar corona, the outer atmosphere of the Sun or another star * Corona (beer), a Mexican beer * Corona, informal term for the coronavirus SARS-CoV-2, which causes the COVID-19 di ...
* DH-1 (rocket) * Interorbital Systems * ''
Land of the Giants ''Land of the Giants'' is a one-hour American science fiction television series that aired on ABC for two seasons, beginning on September 22, 1968 and ending on March 22, 1970. The show was created and produced by Irwin Allen. ''Land of the Gi ...
'' *
List of rocket launch sites This article constitutes a list of rocket launch sites. Some of these sites are known as spaceports or cosmodromes. A single rocket launch is sufficient for inclusion in the table, as long as the site is properly documented through a reference. M ...
*
Lunar Lander Challenge The Northrop Grumman Lunar Lander Challenge (NG-LLC) was a competition funded by NASA's Centennial Challenges program. The competition offered a series of prizes for teams that launch a vertical takeoff/vertical landing (VTVL) rocket that achiev ...
*
McDonnell Douglas DC-X The DC-X, short for Delta Clipper or Delta Clipper Experimental, was an uncrewed prototype of a reusable single-stage-to-orbit launch vehicle built by McDonnell Douglas in conjunction with the United States Department of Defense's Strategic ...
*
Office of Commercial Space Transportation The Office of Commercial Space Transportation (generally referred to as FAA/AST or simply AST) is the branch of the United States Federal Aviation Administration (FAA) that approves any commercial rocket launch operations — that is, any laun ...
*
Project Morpheus Project Morpheus was a NASA project that began in 2010 to develop a vertical takeoff and vertical landing ( VTVL) test vehicle called the Morpheus Lander. It is intended to demonstrate a new nontoxic spacecraft propellant system (methane and o ...
NASA program to continue developing ALHAT and Q­ landers *
Quad (rocket) In rocketry, the Armadillo Aerospace Quad vehicle called Pixel is a computer-controlled VTVL rocket that was used in 2006 to compete in the Lunar Lander Challenge. General description The quad vehicle design is a pressure fed in blow-down mode ...
*
Reusable Vehicle Testing The Reusable Vehicle Testing (RVT) project was conducted by the Japanese Space Agency (JAXA) from 1998 until 2003. The project involved a series of experimental vehicles to test repeated flights of a reusable rocket. Four complete vehicles were d ...
program by
JAXA The is the Japanese national air and space agency. Through the merger of three previously independent organizations, JAXA was formed on 1 October 2003. JAXA is responsible for research, technology development and launch of satellites into or ...
*
Rocketplane XP The Rocketplane XP was a suborbital spaceplane design that was under development c. 2005 by Rocketplane Kistler. The vehicle was to be powered by two jet engines and a rocket engine, intended to enable it to reach suborbital space. The XP would ...
*
Spaceport A spaceport or cosmodrome is a site for launching or receiving spacecraft, by analogy to a seaport for ships or an airport for aircraft. The word ''spaceport'', and even more so ''cosmodrome'', has traditionally been used for sites capable ...
*
SpaceX reusable launch system development program SpaceX is privately funding the development of orbital launch systems that can be reused many times, in a manner similar to the reusability of aircraft. SpaceX has been developing the technologies over several years to facilitate full and ...
*
Supersonic transport A supersonic transport (SST) or a supersonic airliner is a civilian supersonic aircraft designed to transport passengers at speeds greater than the speed of sound. To date, the only SSTs to see regular service have been Concorde and the Tupo ...
*
XCOR Lynx The XCOR Lynx was a proposed suborbital horizontal-takeoff, horizontal-landing (HTHL), rocket-powered spaceplane that was under development by the California-based company XCOR Aerospace to compete in the emerging suborbital spaceflight mark ...


References

{{DEFAULTSORT:Sub-Orbital Spaceflight *