Roll

Roll may refer to:

Places

Music

Vehicles and maneuvers

Other uses

Flight dynamics

Flight dynamics is the study of the performance, stability, and control of vehicles flying through the air or in outer space. It is concerned with how forces acting on the vehicle influence its speed and attitude with respect to time.

In fixed-wing aircraft, the changing orientation of the vehicle with respect to the local air flow is represented by two critical parameters, angle of attack ("alpha") and angle of sideslip ("beta"). These angles describe the vector direction of airspeed, important because it is the principal source of modulations in the aerodynamic forces and moments applied to the aircraft.

Spacecraft flight dynamics involve three forces: propulsive (rocket engine), gravitational, and lift and drag (when traveling through the earths or any other celestial atmosphere). Because aerodynamic forces involved with spacecraft flight are very small, this leaves gravity as the dominant force.

Aircraft and spacecraft share a critical interest in their orientation with respect to the earth horizon and heading, and this is represented by another set of angles, "yaw," "pitch" and "roll" which angles match their colloquial meaning, but also have formal definition as an Euler sequence. These angles are the product of the rotational equations of motion, where orientation responds to torque, just as the velocity of a vehicle responds to forces. For all flight vehicles, these two sets of dynamics, rotational and translational, operate simultaneously and in a coupled fashion to evolve the vehicle's state (orientation and velocity) trajectory.

Euler angles

The Euler angles are three angles introduced by Leonhard Euler to describe the orientation of a rigid body. To describe such an orientation in 3-dimensional Euclidean space three parameters are required. They can be given in several ways, Euler angles being one of them; see charts on SO(3) for others. Euler angles are also used to describe the orientation of a frame of reference (typically, a coordinate system or basis) relative to another. They are typically denoted as α, β, γ, or φ, θ, ψ.

Euler angles represent a sequence of three elemental rotations, i.e. rotations about the axes of a coordinate system. For instance, a first rotation about z by an angle α, a second rotation about x by an angle β, and a last rotation again about y, by an angle γ. These rotations start from a known standard orientation. In physics, this standard initial orientation is typically represented by a motionless (fixed, global, or world) coordinate system; in linear algebra, by a standard basis.

Any orientation can be achieved by composing three elemental rotations. The elemental rotations can either occur about the axes of the fixed coordinate system (extrinsic rotations) or about the axes of a rotating coordinate system, which is initially aligned with the fixed one, and modifies its orientation after each elemental rotation (intrinsic rotations). The rotating coordinate system may be imagined to be rigidly attached to a rigid body. In this case, it is sometimes called a local coordinate system. Without considering the possibility of using two different conventions for the definition of the rotation axes (intrinsic or extrinsic), there exist twelve possible sequences of rotation axes, divided in two groups:

Orca (novel)

Orca is the seventh book in Steven Brust's Vlad Taltos series, set in the fantasy world of Dragaera. Originally published in 1996 by Ace Books, it was republished in 2003 along with Athyra in the omnibus The Book of Athyra. Following the trend of the Vlad Taltos books, it is named after one of the Great Houses and features that House as an important element to its plot.

Plot introduction

Vlad and his friend Kiera the Thief investigate a financial cover-up following the mysterious death of an Orca tycoon.

Plot summary

Reunions

Kiera the Thief sends a letter to Vlad's estranged wife Cawti, offering to meet and tell her of Vlad's most recent adventures. In return for not telling Vlad some of Cawti's secrets, Kiera insists on making some omissions from her story. The rest of the novel is Kiera's story, seemingly without the omissions she makes to Cawti.

Vlad contacts Kiera from the city of Northport and asks her a favor: break into the mansion of the late Orca businessman Fyres and take any documents she can find. She agrees if he will explain why. He tells her that he went to Northport to find a healer for Savn, a Teckla boy whose mind was damaged during the events of Athyra. A local healer, whom Vlad calls "Mother" because he cannot pronounce her name, agrees to help Savn if Vlad will help fix her problem: she's being evicted from her cottage. Vlad navigates through a labyrinth of business records to discover that Mother's land is ultimately owned by Fyres, who only a week ago died on his yacht.

Orca Symphony No. 1

Orca Symphony No. 1 is the fourth studio album by Armenian-American singer Serj Tankian. The album takes the form of a classical symphony. A professionally sampled studio version was released on November 30, 2012, while the live recorded version was released on June 25, 2013 through Serjical Strike Records.

A sample of the first act of the album was released on Tankian's SoundCloud page on May 2012.

Background

Tankian achieved fame as part of the American rock band System of a Down. Although the band experimented with various sounds, it wasn't until the band went on hiatus in 2006 that Tankian was free to launch his solo career and experiment further.

Tankian's experimentation with classical composition began with Elect the Dead Symphony. The live album featured the Auckland Philharmonia Orchestra performing reworked versions of songs from Tankian's debut album Elect the Dead. His second album, Imperfect Harmonies, blended classical with traditional rock elements. Tankian described the album as "music that has sat in the vat and matured", referring to the album's influences from several genres.

Orca (disambiguation)

Orca is a name for the killer whale, a large marine mammal.

Orca or Orcas may also refer to:

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Arts and entertainment

Fictional characters and vehicles