# orbital velocity

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## orbital velocity

The velocity of a satellite or other orbiting body at any given point in its orbit. It is also the velocity required by a satellite to enter an orbit around a body. The orbital velocity, v, is given by the expression
v = √[gR 2(2/r – 1/a )]
where R is the radius of the orbited body, r is the distance from the center of mass of the system (i.e. from the approximate center of the primary), a is the semimajor axis of the orbit, and g is the standard acceleration of gravity. For a circular orbit, r = a and the circular velocity is given by
v = √(gR 2/r )

To escape from an orbit a must tend to infinity and the escape velocity is then given by

v e = √(2gR 2/r )

The orbital period for an elliptical orbit is given by

P = 2πa 3/2/√gR 2

Collins Dictionary of Astronomy © Market House Books Ltd, 2006

## orbital velocity

[′ȯr·bəd·əl və′läs·əd·ē]
(astronomy)
The instantaneous velocity at which an earth satellite or other orbiting body travels around the origin of its central force field.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
From Figures 10 and 11, it can be seen that the best-fit CDF and the observed CDF of semi-major axis agree better than the case of mean orbital velocity. This should be due to the fact that the p value of the former is 0.9988, which is obviously larger than that of the latter 0.6607.
When the max-[DELTA]E strategy (here improperly so called) is adopted, [v.sub.[infinity]] and pump angle after the gravity assist are large, and a further flyby, without any DSM (and leveraging), could align the spacecraft velocity to the moon orbital velocity.
The orbital velocity of Venus ([v.sub.min] = 34.79 and [v.sub.max] = = 35.26 km/s) corresponds well to the main attractor node [-9; [infinity]] of the speed of light calibrated F (12):
* numerically evaluated the orbital velocity, particularly its horizontal components, including the effect of nonlinearity and current;
The craft measured their separation five times per second to extreme precision, detecting orbital velocity changes as small as 0.05 micron per second--"one twenty-thousandth the velocity that a snail moves," says principal investigator Maria Zuber (MIT).
[V.sub.xl](x, t) and [V.sub.zl](x, t) denote the horizontal- and the vertical-components of large-scale waves' orbital velocity. [H.sub.y] is the spectral disturbance induced by the HM.
But by studying how the starlight shifted as it passed through the atmosphere of exoplanet HD 209458b (illustrated), Dutch researchers found the planet's orbital velocity. Plugging the data into Newton's law of gravity gave a value for the planet's mass--about 64 percent of Jupiter's, the team reports in the June 24 Nature.
"Earth is a great place to pick up orbital velocity. This flyby will give our spacecraft a 1.5-kilometer-per-second [3,470 mph] boost, setting us up to get up close and personal with comet Hartley 2.," said Tim Larson, the EPOXI project manager from NASA's Jet Propulsion Laboratory in Pasadena, Calif.
It is not sufficiently powerful to reach orbital velocity on its own so has to be launched by a rocket.
Orbital velocity keeps space objects from being pulled in by gravity from a larger body such as the Sun.
Highlights include file footage of Sergei Korolev, designer of the R-7 rocket that launched Sputnik, and a lucid illustration of Isaac Newton's concept of orbital velocity. Sputnik Declassified traces the origins of the space race to the V-2 rocket Wernher von Braun designed to terrorize British civilians.
The second and third stages separated successfully and the missile reached orbital velocity, but the attempt failed because the third-stage booster malfunctioned.

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