Helios (/ˈhiːli.ɒs/; Ancient Greek: Ἥλιος Hēlios; Latinized as Helius; Ἠέλιος in Homeric Greek) was the personification of the Sun in Greek mythology. He is the son of the Titan Hyperion and the Titaness Theia (Hesiod) (also known as Euryphaessa (Homeric Hymn 31)) and brother of the goddesses Selene, the moon, and Eos, the dawn.
Helios was described as a handsome titan crowned with the shining aureole of the Sun, who drove the chariot of the sun across the sky each day to earth-circling Oceanus and through the world-ocean returned to the East at night. In the Homeric hymn to Helios, Helios is said to drive a golden chariot drawn by steeds (HH 31.14–15); and Pindar speaks of Helios's "fire-darting steeds" (Olympian Ode 7.71). Still later, the horses were given fiery names: Pyrois, Aeos, Aethon, and Phlegon.
As time passed, Helios was increasingly identified with the god of light, Apollo. However, in spite of their syncretism, they were also often viewed as two distinct gods/titan (Helios was a Titan, whereas Apollo was an Olympian). The equivalent of Helios in Roman mythology was Sol, specifically Sol Invictus.
The NASA Pathfinder and NASA Pathfinder Plus were the first two aircraft developed as part of an evolutionary series of solar- and fuel-cell-system-powered unmanned aerial vehicles. AeroVironment, Inc. developed the vehicles under NASA's Environmental Research Aircraft and Sensor Technology (ERAST) program. They were built to develop the technologies that would allow long-term, high-altitude aircraft to serve as "atmospheric satellites", to perform atmospheric research tasks as well as serve as communications platforms. They were developed further into the NASA Centurion and NASA Helios aircraft.
AeroVironment initiated its development of full-scale solar-powered aircraft with the Gossamer Penguin and Solar Challenger vehicles in the late 1970s and early 1980s, following the pioneering work of Robert Boucher, who built the first solar-powered flying models in 1974. Under ERAST, AeroVironment built four generations of long endurance unmanned aerial vehicles (UAVs), the first of which was the Pathfinder.
Helios is a design for a spacecraft propulsion system such that small (0.1 kiloton) nuclear bombs would be detonated in a chamber roughly 130 feet in diameter. Water would be injected into the chamber, super-heated by the explosion and expelled for thrust. It was a precursor concept to the Orion project. Like Orion, it would have achieved constant acceleration through rapid "pulsed" operation.
This design would have yielded a specific impulse of about 1150 seconds (compared to a modern chemical rocket’s 450 seconds). However, a number of technical problems existed, most prominently how to keep the combustion chamber from exploding from the great pressures of the atomic detonations.
The Helios propulsion system was conceived originally by Freeman Dyson.
Moment or Moments may refer to:
In mathematics, a moment is a specific quantitative measure, used in both mechanics and statistics, of the shape of a set of points. If the points represent mass, then the zeroth moment is the total mass, the first moment divided by the total mass is the center of mass, and the second moment is the rotational inertia. If the points represent probability density, then the zeroth moment is the total probability (i.e. one), the first moment is the mean, the second central moment is the variance, the third moment is the skewness, and the fourth moment (with normalization and shift) is the kurtosis. The mathematical concept is closely related to the concept of moment in physics.
For a bounded distribution of mass or probability, the collection of all the moments (of all orders, from 0 to ∞) uniquely determines the distribution.
The n-th moment of a real-valued continuous function f(x) of a real variable about a value c is
It is possible to define moments for random variables in a more general fashion than moments for real values—see moments in metric spaces. The moment of a function, without further explanation, usually refers to the above expression with c = 0.
Moment (Serbian: Трен, translit. Tren) is a 1978 Yugoslav war film directed by Stole Janković. It was entered into the 11th Moscow International Film Festival where Bata Živojinović won the award for Best Actor.