Reaction Wheel
A reaction wheel is a type of flywheel used primarily by spacecraft to change their angular momentum without using fuel for rockets or other reaction devices. Reaction wheels are devices which aim a spacecraft in different directions without firing rockets or jets. They are particularly useful when the spacecraft must be rotated by very small amounts, such as keeping a telescope pointed at a star. They may also reduce the mass fraction needed for fuel. This is accomplished by equipping the spacecraft with an electric motor attached to a flywheel, which upon spinup causes the spacecraft to turn the other way by conservation of angular momentum. However, they are not capable of moving the spacecraft from one place to another, they can only rotate the spacecraft around its center of mass.
Momentum wheels used in the Hubble Space Telescope are a different type of actuator, mainly used for gyroscopic stabilization of spacecraft: momentum wheels have high rotation speeds (around 5000 rpm) and mass, while reaction wheels work around a nominal zero rotation speed.
Reaction wheels are usually implemented as special electric motors. Both spin-up and braking are controlled electronically by computer controls. The strength of the materials of a reaction wheel determines the speed at which the wheel would come apart, and therefore how much angular momentum it can store.
Since the reaction wheel is a small fraction of the spacecraft’s total mass, easily-measurable changes in its speed provide very precise changes in angle. It therefore permits very precise changes in a spacecraft’s attitude. For this reason, reaction wheels are often used to aim spacecraft with cameras or telescopes.
Voyager Golden Record
The Voyager Golden Record is a phonograph record included in the two Voyager spacecraft launched in 1977. It contains sounds and images selected to portray the diversity of life and culture on Earth. It is intended for any intelligent extraterrestrial life form, or far future humans, that may find it. The Voyager spacecraft would take about 40,000 years to reach the distance of the star nearest the Sun, Alpha Centauri at a distance of 4.4 light-years, though neither craft is traveling toward that star.
As the probes are extremely small compared to the vastness of interstellar space, it is extraordinarily unlikely that they will ever be accidentally encountered. If they are ever found by an alien species, it will most likely be far in the future, and thus the record is best seen as a time capsule or a symbolic statement rather than a serious attempt to communicate with extraterrestrial life.
Voyager Golden Record
Pioneer plaque
The Pioneer plaques are a pair of gold anodized aluminum plaques which were placed on board the 1972 Pioneer 10 and 1973 Pioneer 11 spacecraft, featuring a pictorial message from humanity, in case either Pioneer 10 or 11 are intercepted by extraterrestrial beings. The plaques show the nude figures of a human male and female along with several symbols that are designed to provide information about the origin of the spacecraft.
The Pioneer spacecraft were the first human-built objects to leave the solar system. The plaque is attached to the antenna support struts in a position that shields it from erosion by stellar dust.
Pale Blue Dot
The Pale Blue Dot is a photograph of planet Earth made by Voyager 1 from a record distance, showing it against the vastness of space. It is also the title of a 1994 book by astronomer Carl Sagan that was inspired by the photo. In 2001, it was selected by Space.com as one of the top ten space science photos.
The photograph taken below was captured by the Voyager 1 spacecraft from a distance of approximately 3.7 billion miles. Earth is seen near the right side of the image, inside a band of light caused by side-effects of the camera.
Dyson Sphere
A Dyson sphere (or shell as it appeared in the original paper) is a hypothetical megastructure originally described by Freeman Dyson. Such a “sphere” would be a system of orbiting solar power satellites meant to completely encompass a star and capture most or all of its energy output. Dyson speculated that such structures would be the logical consequence of the long-term survival and escalating energy needs of a technological civilization, and proposed that searching for evidence of the existence of such structures might lead to the detection of advanced intelligent extraterrestrial life.
The concept of the Dyson sphere was the result of a thought experiment by physicist and mathematician Freeman Dyson, where he noted that every human technological civilization has constantly increased its demand for energy. He reasoned that if human civilization were to survive long enough, there would come a time when it required the total energy output of the sun. Thus, he proposed a system of orbiting structures designed to intercept and collect all energy produced by the sun. Dyson’s proposal did not detail how such a system would be constructed, but focused only on issues of energy collection.
via Dyson sphere – Wikipedia, the free encyclopedia
Kardashev Scale
The Kardashev scale is a general method of classifying how technologically advanced a civilization is. It was first proposed in 1964 by the Soviet astronomer Nikolai Kardashev. The scale has three designated categories called Type I, II, and III. These are based on the amount of usable energy a civilization has at its disposal, and the degree of space colonization. In general terms, a Type I civilization has achieved mastery of the resources of its home planet, Type II of its solar system, and Type III of its galaxy.
Space Fountain
Just in case space elevators were too boring for your tastes…
“A space fountain is a proposed form of space elevator that does not require the structure to be in geosynchronous orbit, and does not rely on tensile strength for support. In contrast to the original space elevator design (a tethered satellite), a space fountain is a tremendously tall tower extending up from the ground. Since such a tall tower could not support its own weight using traditional materials, massive pellets are projected upward from the bottom of the tower and redirected back down once they reach the top, so that the force of redirection holds the top of the tower aloft. Satellite payloads ascend or descend by coupling with this stream of pellets or by climbing up the side of the tower. The space fountain has several key advantages over a space elevator in that it doesn’t require materials with extreme strength, can be located at any point on a planet’s surface instead of just the equator, and can be raised to any height required. Its major disadvantage is that it is an active structure, and so requires constant power input to remain aloft.”
Space fountain – Wikipedia, the free encyclopedia
Starfish Prime
Starfish Prime was a high-altitude nuclear test conducted by the United States of America on July 9, 1962, a joint effort of the Defense Atomic Support Agency (DASA) and the Atomic Energy Commission (AEC). Launched via a Thor rocket and carrying a W49 thermonuclear warhead (manufactured by Los Alamos Scientific Laboratory) and a Mk. 4 reentry vehicle, the explosion took place 400 kilometers (250 miles) above Johnston Island in the Pacific Ocean. It was one of five tests conducted by the USA in outer space as defined by the FAI. It produced a yield of 1.4 megatons of TNT.
Because there is almost no air at an altitude of 400 kilometers, no fireball formation occurred, although there were many other notable effects. About 1500 kilometers (930 statute miles) away in Hawaii, the electromagnetic pulse (EMP) created by the explosion was felt as three hundred street lights failed, television sets and radios malfunctioned, burglar alarms went off and power lines fused. On Kauai, the EMP shut down telephone calls to the other islands by burning out the equipment used in a microwave link. Also, the sky in the Pacific region was illuminated by an artificial aurora for more than seven minutes. In part, these effects were predicted by Nicholas Christofilos, a scientist who had earlier worked on the Operation Argus high-altitude nuclear shots.
While some of the energetic beta particles followed the earth’s magnetic field and illuminated the sky, other high-energy electrons became trapped and formed radiation belts around the earth. There was much uncertainty and debate about the composition, magnitude and potential adverse effects from this trapped radiation after the detonation. The weaponeers became quite worried when three satellites in low earth orbit were disabled. These man-made radiation belts eventually crippled one-third of all satellites in low orbit. Seven satellites were destroyed as radiation knocked out their solar arrays or electronics, including the first commercial relay communication satellite ever, Telstar. Detectors on Telstar, TRAAC, Injun, and Ariel 1 were used to measure distribution of the radiation produced by the tests.
Penrose process
The Penrose process (also called Penrose mechanism) is a process theorised by Roger Penrose wherein energy can be extracted from a rotating black hole. That extraction is made possible by the existence of a region of the Kerr spacetime called the ergoregion, a region in which a particle is necessarily propelled in locomotive concurrence with the rotating spacetime. In the process, a lump of matter enters into the ergoregion of the black hole, and once it enters the ergoregion, is split into two. The momentum of the two pieces of matter can be arranged so that one piece escapes to infinity, whilst the other falls past the outer event horizon into the hole. The escaping piece of matter can possibly have greater mass-energy than the original infalling piece of matter. In summary, the process results in a decrease in the angular momentum of the black hole, and that reduction corresponds to a transference of energy whereby the momentum lost is converted to energy extracted.
The process obeys the laws of black hole mechanics. A consequence of these laws is that if the process is performed repeatedly, the black hole can eventually lose all of its angular momentum, becoming rotationally stationary.
Omega Speedmaster Professional
The Omega Speedmaster Professional, otherwise known as the “Moonwatch”, is a manual winding chronograph introduced in 1957 and made famous by its selection by NASA for the Apollo Program. The Speedmaster is the only watch to have been worn on the moon (except for the Waltham Watch Company wristwatch worn by Dave Scott after the crystal had popped off his Speedmaster), and the only watch flight-qualified for EVA use by NASA. It is also the watch chosen for use in outer space by the Russian space agency NPO Energia.
When the step-by-step procedures of the Project Gemini space-walks were first mapped out, NASA realized that they did not have an approved wristwatch for space travel. The normal procedure of soliciting bids for the design, manufacture and testing of special “Space Proof” wristwatches was a time consuming process. To save time, NASA sent two systems engineers into downtown Houston “incognito” to purchase several reputable “off-the-shelf” chronographs to be tested for possible use in space. A manual-winding watch was preferred to an automatic watch, as it was assumed that zero-gravity conditions would render the self-winding mechanism ineffective.
Five different brands of chronographs were purchased and returned to NASA for testing. The Speedmaster passed NASA’s numerous tests, which included exposure to extreme temperatures, vacuum, intense humidity, corrosion, shock, acceleration, pressure, vibration and noise, whereas the Rolex, Breitling, Bulova, Longines and Heuer, notably, all failed.
The tests were completed on March 1st, 1965. At the completion of the tests, three of the chronographs from different manufactures were still running, but only the Speedmaster had passed without any of the serious discrepancies encountered with the others. The Omega Speedmaster was adopted by NASA as the “Officially Certified Wristwatch For All Manned Space Missions.” At this point, Omega was completely unaware of these activities.
The Omega Speedmaster was re-certified in 1972 and in September 1978, for the Space Shuttle missions.
Today, all NASA-issued wristwatches are government property and must be turned in once the astronauts return to Earth. Astronauts are permitted to check the watches out before launch and take them home to familiarize themselves with the watch’s operation.
Omega Speedmaster Professional – Wikipedia, the free encyclopedia