7.2 KiB
| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Glossary of aerospace engineering | 10/27 | https://en.wikipedia.org/wiki/Glossary_of_aerospace_engineering | reference | science, encyclopedia | 2026-05-05T07:50:15.292303+00:00 | kb-cron |
F
D
=
1
2
ρ
u
2
C
D
A
{\displaystyle F_{D}\,=\,{\tfrac {1}{2}}\,\rho \,u^{2}\,C_{D}\,A}
F
D
{\displaystyle F_{D}}
is the drag force, which is by definition the force component in the direction of the flow velocity,
ρ
{\displaystyle \rho }
is the mass density of the fluid,
u
{\displaystyle u}
is the flow velocity relative to the object,
A
{\displaystyle A}
is the reference area, and
C
D
{\displaystyle C_{D}}
is the drag coefficient – a dimensionless coefficient related to the object's geometry and taking into account both skin friction and form drag. In general,
C
D
{\displaystyle C_{D}}
depends on the Reynolds number. Drop test – is a method of testing the in-flight characteristics of prototype or experimental aircraft and spacecraft by raising the test vehicle to a specific altitude and then releasing it. Test flights involving powered aircraft, particularly rocket-powered aircraft, may be referred to as drop launches due to the launch of the aircraft's rockets after release from its carrier aircraft. Dual mode propulsion rocket – Dual mode propulsion systems combine the high efficiency of bipropellant rockets with the reliability and simplicity of monopropellant rockets. It is based upon the use of two rocket fuels, liquid hydrogen and more dense hydrocarbon fuels, like RP, which are all burned with liquid oxygen. Ductility – is a measure of a material's ability to undergo significant plastic deformation before rupture, which may be expressed as percent elongation or percent area reduction from a tensile test.
== E == Earth's atmosphere – The atmosphere of Earth is the layer of gases, commonly known as air, that surrounds the planet Earth and is retained by Earth's gravity. The atmosphere of Earth protects life on Earth by creating pressure allowing for liquid water to exist on the Earth's surface, absorbing ultraviolet solar radiation, warming the surface through heat retention (greenhouse effect), and reducing temperature extremes between day and night (the diurnal temperature variation). Eccentric anomaly – In orbital mechanics, the eccentric anomaly is an angular parameter that defines the position of a body that is moving along an elliptic Kepler orbit. The eccentric anomaly is one of three angular parameters ("anomalies") that define a position along an orbit, the other two being the true anomaly and the mean anomaly. Eccentricity vector – In celestial mechanics, the eccentricity vector of a Kepler orbit is the dimensionless vector with direction pointing from apoapsis to periapsis and with magnitude equal to the orbit's scalar eccentricity. For Kepler orbits the eccentricity vector is a constant of motion. Its main use is in the analysis of almost circular orbits, as perturbing (non-Keplerian) forces on an actual orbit will cause the osculating eccentricity vector to change continuously. For the eccentricity and argument of periapsis parameters, eccentricity zero (circular orbit) corresponds to a singularity. The magnitude of the eccentricity vector represents the eccentricity of the orbit. Note that the velocity and position vectors need to be relative to the inertial frame of the central body. Eigenvector slew – In aerospace engineering, especially those areas dealing with spacecraft, the eigenvector slew is a method to calculate a steering correction (called a slew) by rotating the spacecraft around one fixed axis, or a gimbal. This corresponds in general to the fastest and most efficient way to reach the desired target orientation as there is only one acceleration phase and one braking phase for the angular rate. If this fixed axis is not a principal axis a time varying torque must be applied to force the spacecraft to rotate as desired, though. Also the gyroscopic effect of momentum wheels must be compensated for. Electrostatic ion thruster – is a form of electric propulsion used for spacecraft propulsion. It creates thrust by accelerating ions using electricity. Elevator – is a flight control surface, usually at the rear of an aircraft, which control the aircraft's pitch, and therefore the angle of attack and the lift of the wing. The elevators are usually hinged to the tailplane or horizontal stabilizer. Elliptic partial differential equation – Empennage – The empennage ( or ), also known as the tail or tail assembly, is a structure at the rear of an aircraft that provides stability during flight, in a way similar to the feathers on an arrow. The term derives from the French language verb empenner which means "to feather an arrow". Most aircraft feature an empennage incorporating vertical and horizontal stabilising surfaces which stabilise the flight dynamics of yaw and pitch, as well as housing control surfaces. Enstrophy – In fluid dynamics, the enstrophy E can be interpreted as another type of potential density; or, more concretely, the quantity directly related to the kinetic energy in the flow model that corresponds to dissipation effects in the fluid. It is particularly useful in the study of turbulent flows, and is often identified in the study of thrusters as well as the field of combustion theory. Given a domain
Ω
⊆
R
n
{\displaystyle \Omega \subseteq \mathbb {R} ^{n}}
and a once-weakly differentiable vector field
u
∈
H
1
(
R
n
)
n
{\displaystyle u\in H^{1}(\mathbb {R} ^{n})^{n}}
which represents a fluid flow, such as a solution to the Navier-Stokes equations, its enstrophy is given by:
E
(
u
)
:=
∫
Ω
|
∇
u
|
2
d
x
{\displaystyle {\mathcal {E}}(u):=\int _{\Omega }|\nabla \mathbf {u} |^{2}\,dx}