Gravity loss

<p>In <a href="/facts/Astrodynamics/oB3tqNG9">astrodynamics</a> and <a href="/facts/Rocket/b6j4keIl">rocketry</a>, gravity loss is a measure of the loss in the net performance of a rocket while it is thrusting in a <a href="/facts/Gravitational_field/K1uTmJFy">gravitational field</a>.  In other words, it is the cost of having to hold the rocket up in a gravity field.
</p><p>Gravity losses depend on the time over which thrust is applied as well the direction the thrust is applied in. Gravity losses as a proportion of delta-v are minimised if maximum thrust is applied for a short time, and by avoiding thrusting directly away from the local gravitational field. During the launch and ascent phase, however, thrust must be applied over a long period with a major component of thrust in the opposite direction to gravity, so gravity losses become significant. For example, to reach a speed of 7.8 km/s in <a href="/facts/Low_Earth_orbit/rq1TwayJ">low Earth orbit</a> requires a <a href="/facts/Delta-v/eM4TaG9d">delta-v</a> of between 9 and 10 km/s. The additional 1.5 to 2 km/s delta-v is due to gravity losses, steering losses and <a href="/facts/Atmospheric_drag/vdl4jF7I">atmospheric drag</a>.
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Gravity loss open-in-new

Gravity loss