Information about 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 altitude at perigee (altitude at closest approach) above km ( mi) (this is by convention the boundary of space).
The expression "orbital spaceflight" is mostly used to distinguish from sub-orbital spaceflights, which are flights where apogee of a spacecraft reaches space but perigee is too low.
The only proven technique involves launching nearly vertically for a few kilometers while performing a gravity turn, and then progressively flattening the trajectory out at an altitude of 170+ km and accelerating on a horizontal trajectory (with the rocket angled upwards to fight gravity and maintain altitude) for a 5-8 minute burn until orbital velocity is achieved. Frequently 2-3 stages are needed to achieve sufficient delta-v.
Project HARP was a failed attempt, and a ram accelerator is another design, to launch an object into orbit with a gun, possibly with additional propulsion by a rocket.
Returning craft though (including all potentially manned craft), have to find a way of slowing down as much as possible while still in higher atmospheric layers and avoid hitting the ground (lithobraking) or burning up. The problem of deceleration from orbital speeds is solved through using atmospheric drag (aerobraking) to lose nearly all of the speed. On an orbital space flight initial deceleration is provided by the retrofiring of the craft's rocket engines, perturbing the orbit (by lowering perigee down into the atmosphere) onto a suborbital trajectory.
Aerobraking is achieved by orienting the returning space craft to fly so as to present the heat shields forwards towards the atmosphere so as to protect against the high temperatures generated by atmospheric compression and friction caused by passing through the atmosphere at hypersonic speeds. The thermal energy is dissipated mainly by compression heating the air in a shockwave ahead of the vehicle using a blunt heat shield shape, with the aim of minimising the heat entering the vehicle. Sub-orbital space flights, being at a much lower speed, do not generate anywhere near as much heat upon re-entry.
This has allowed maverick aircraft designer Burt Rutan recently (July 2004) to demonstrate an alternative or complementary approach to heat shield dependent reentry with the suborbital SpaceShipOne. It may be possible that the concepts utilized in SpaceShipOne's design can be applied to orbital space craft design and result in intrinsic stability of the vehicle through reentry (as opposed to the active stability used on the Space Shuttle.) Currently however, the need for an ultra high-performance and ultra reliable heat shield is a major difference between crafts designed for orbital flights (as opposed to sub-orbital ones), demonstrated in the Mercury program wherein the orbital flights used a typical ablative heat shield while the sub-orbital flights relied simply on a large metal heat-sink.
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The expression "orbital spaceflight" is mostly used to distinguish from sub-orbital spaceflights, which are flights where apogee of a spacecraft reaches space but perigee is too low.
Methods
Orbital spaceflight from Earth has only been achieved by large rockets that are capable of accelerating from rest to about 10 km/s. This figure allows for atmospheric drag (approximately 300 m/s with the ballistic coefficient of a 20 m long dense fuelled vehicle), gravity losses (depending on burn time and details of the trajectory and launch vehicle), gaining altitude, and the horizontal acceleration needed to reach orbital speed (~7.8km/s depending on altitude).The only proven technique involves launching nearly vertically for a few kilometers while performing a gravity turn, and then progressively flattening the trajectory out at an altitude of 170+ km and accelerating on a horizontal trajectory (with the rocket angled upwards to fight gravity and maintain altitude) for a 5-8 minute burn until orbital velocity is achieved. Frequently 2-3 stages are needed to achieve sufficient delta-v.
Project HARP was a failed attempt, and a ram accelerator is another design, to launch an object into orbit with a gun, possibly with additional propulsion by a rocket.
Stability
Any object in orbit at an altitude of less than roughly 200 km is considered unstable due to the amount friction caused by the atmosphere. For a satellite to be in a stable orbit (i.e. sustainable for more than a few months), 350 km is a more standard altitude for low Earth orbit.Orbits
There are three main 'bands' of orbit: low Earth orbit, intermediate circular orbit and geostationary orbit.Re-entry
Due to the high speeds of orbital spaceflight, atmospheric reentry is much more difficult compared to sub-orbital flights. Note however, that such considerations only apply to orbital flights where the vehicle needs to return to Earth intact. If the vehicle is, say, a satellite that is ultimately expendable, then there naturally is no need to worry about reentry.Returning craft though (including all potentially manned craft), have to find a way of slowing down as much as possible while still in higher atmospheric layers and avoid hitting the ground (lithobraking) or burning up. The problem of deceleration from orbital speeds is solved through using atmospheric drag (aerobraking) to lose nearly all of the speed. On an orbital space flight initial deceleration is provided by the retrofiring of the craft's rocket engines, perturbing the orbit (by lowering perigee down into the atmosphere) onto a suborbital trajectory.
Aerobraking is achieved by orienting the returning space craft to fly so as to present the heat shields forwards towards the atmosphere so as to protect against the high temperatures generated by atmospheric compression and friction caused by passing through the atmosphere at hypersonic speeds. The thermal energy is dissipated mainly by compression heating the air in a shockwave ahead of the vehicle using a blunt heat shield shape, with the aim of minimising the heat entering the vehicle. Sub-orbital space flights, being at a much lower speed, do not generate anywhere near as much heat upon re-entry.
This has allowed maverick aircraft designer Burt Rutan recently (July 2004) to demonstrate an alternative or complementary approach to heat shield dependent reentry with the suborbital SpaceShipOne. It may be possible that the concepts utilized in SpaceShipOne's design can be applied to orbital space craft design and result in intrinsic stability of the vehicle through reentry (as opposed to the active stability used on the Space Shuttle.) Currently however, the need for an ultra high-performance and ultra reliable heat shield is a major difference between crafts designed for orbital flights (as opposed to sub-orbital ones), demonstrated in the Mercury program wherein the orbital flights used a typical ablative heat shield while the sub-orbital flights relied simply on a large metal heat-sink.
See also
Spaceflight is the use of space technology to fly a spacecraft into and through outer space.
Spaceflight is used in space exploration, and also in commercial activities like space tourism and satellite telecommunications.
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Spaceflight is used in space exploration, and also in commercial activities like space tourism and satellite telecommunications.
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spacecraft is a vehicle or device designed for spaceflight. On a sub-orbital spaceflight, a spacecraft enters outer space but then returns to the planetary surface (such as Earth) without making a complete orbit.
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Outer space, sometimes simply called space, refers to the relatively empty regions of the universe outside the atmospheres of celestial bodies. Outer space is used to distinguish it from airspace (and terrestrial locations).
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Perigee is the point at which an object in orbit around the Earth makes its closest approach to the Earth. This term commonly refers to the Moon but can be applied to any earth-orbiting body, such as artificial satellites.
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Kármán line lies at an altitude of 100 km (62.1 miles) above the Earth's surface, and is commonly used to define the boundary between the Earth's atmosphere and outer space.
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A sub-orbital spaceflight (or sub-orbital flight) is a spaceflight in which the spacecraft reaches space, but its trajectory then intersects the atmosphere or surface of the gravitational body from which it was launched, and thus does not enter a stable orbit.
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The ballistic coefficient (BC) of a body is a measure of its ability to overcome air resistance in flight. It is inversely proportional to the deceleration—a high number indicates a low deceleration. BC is a function of mass, diameter, and drag coefficient.
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In astrodynamics, gravity drag (or gravity losses) is inefficiency encountered by a spacecraft thrusting while moving against a gravitational field. It describes an inefficient use of thrust, not some magical effect on the efficiency of the operation of the engines.
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A gravity turn or zero-lift turn is a maneuver used in launching a spacecraft into, or descending from, an orbit around a celestial body such as a planet or a moon.
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In general physics, delta-v is simply the change in velocity.
Depending on the situation, delta-v can be referred to as a spatial vector () or scalar (). In both cases it is equal to the acceleration (vector or scalar) integrated over time:
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Depending on the situation, delta-v can be referred to as a spatial vector () or scalar (). In both cases it is equal to the acceleration (vector or scalar) integrated over time:
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Project HARP, short for High Altitude Research Project, was a joint project of the United States Department of Defense and Canada's Department of National Defence created with the goal of studying ballistics of re-entry vehicles at low cost; whereas most such projects used
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A ram accelerator has the same function as a gun; i.e., it is a device for accelerating projectiles; however, it is totally different in that jet-engine-like propulsion cycles utilizing ramjet and/or scramjet combustion processes are used to accelerate a projectile to extremely
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gun is a common name given to an object that fires high-velocity projectiles. The projectile is fired through a hollow tube known as the gun's barrel. The projectile's caliber is usually designated in fractions of an inch or in millimeters.
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rocket is a vehicle, missile or aircraft which obtains thrust by the reaction to the ejection of fast moving fluid from within a rocket engine.
The history of rockets goes back to at least the 13th century[1].
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The history of rockets goes back to at least the 13th century[1].
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Low Earth Orbit (LEO) is generally defined as an orbit within the locus extending from the Earth’s surface up to an altitude of 2,000 km. Given the rapid orbital decay of objects below approximately 200 km, the commonly accepted definition for LEO is between 200 - 2000 km
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Low Earth Orbit (LEO) is generally defined as an orbit within the locus extending from the Earth’s surface up to an altitude of 2,000 km. Given the rapid orbital decay of objects below approximately 200 km, the commonly accepted definition for LEO is between 200 - 2000 km
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Medium Earth Orbit (MEO), sometimes called Intermediate Circular Orbit (ICO), is the region of space around the Earth above low Earth orbit (2,000 kilometres (1243 mi)
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A geostationary orbit (GEO) is a geosynchronous orbit directly above the Earth's equator (0° latitude), with orbital eccentricity of zero. From the ground, a geostationary object appears motionless in the sky and is therefore the orbit of most interest to operators
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Atmospheric reentry is the process by which vehicles that are outside the atmosphere of a planet can enter that atmosphere and reach the planetary surface intact. Vehicles that undergo this process include spacecraft from orbit, vehicles coming straight from other space bodies, as
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Lithobraking is a technique of descent by an unmanned space vehicle (usually a probe) to the surface of a body by which the vehicle is slowed by impact with the body's surface.
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Aerobraking is a spaceflight maneuver that reduces the high point of an elliptical orbit (apoapsis) by flying the vehicle through the atmosphere at the low point of the orbit (periapsis), using drag to slow the spacecraft.
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Perigee is the point at which an object in orbit around the Earth makes its closest approach to the Earth. This term commonly refers to the Moon but can be applied to any earth-orbiting body, such as artificial satellites.
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hypersonic speeds are speeds that are highly supersonic. In the 1970s, the term generally came to refer to speeds of Mach 5 (5 times the speed of sound) and above. The hypersonic regime is a subset of the supersonic regime.
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Elbert Leander "Burt" Rutan (born June 17, 1943 in Estacada, Oregon) is an American aerospace engineer noted for his originality in designing light, strong, unusual-looking, energy-efficient aircraft.
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Atmospheric reentry is the process by which vehicles that are outside the atmosphere of a planet can enter that atmosphere and reach the planetary surface intact. Vehicles that undergo this process include spacecraft from orbit, vehicles coming straight from other space bodies, as
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Scaled Composites Model 316 SpaceShipOne completed the first privately funded human spaceflight on June 21, 2004.
SpaceShipOne was an experimental air-launched suborbital spaceplane that used a hybrid rocket motor.
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SpaceShipOne was an experimental air-launched suborbital spaceplane that used a hybrid rocket motor.
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Space Shuttle
Space Shuttle Atlantis on the launch pad prior to the STS-115 mission.
Fact sheet
Function Manned partially re-usable launch and reentry system
Manufacturer United Space Alliance:
Thiokol/Boeing (SRBs)
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Space Shuttle Atlantis on the launch pad prior to the STS-115 mission.
Fact sheet
Function Manned partially re-usable launch and reentry system
Manufacturer United Space Alliance:
Thiokol/Boeing (SRBs)
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Project Mercury was the first human spaceflight program of the United States. It ran from 1959 through 1963 with the goal of putting a man in orbit around the Earth. The Mercury-Atlas 6 flight on February 20, 1962 was the first Mercury flight to achieve this goal.
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Atmospheric reentry is the process by which vehicles that are outside the atmosphere of a planet can enter that atmosphere and reach the planetary surface intact. Vehicles that undergo this process include spacecraft from orbit, vehicles coming straight from other space bodies, as
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