Ion Propulsion: The Key to Deep Space Exploration

Sunday, November 8, 2015

Ion Propulsion: The Key to Deep Space Exploration

Ion Propulsion: The Key to Deep Space Exploration:

The comforting blue glow of an ion drive. Image Credit: NASA

When we think of space travel, we tend to picture a massive rocket blasting off from Earth, with huge blast streams of fire and smoke coming out the bottom, as the enormous machine struggles to escape Earth’s gravity. Rockets are our only option for escaping Earth’s gravity well—for now. But once a spacecraft has broken its gravitational bond with Earth, we have other options for powering them. Ion propulsion, long dreamed of in science fiction, is now used to send probes and spacecraft on long journeys through space.

NASA first began researching ion propulsion in the 1950’s. In 1998, ion propulsion was successfully used as the main propulsion system on a spacecraft, powering the Deep Space 1 (DS1) on its mission to the asteroid 9969 Braille and Comet Borrelly. DS1 was designed not only to visit an asteroid and a comet, but to test twelve advanced, high-risk technologies, chief among them the ion propulsion system itself.

Ion propulsion systems generate a tiny amount of thrust. Hold nine quarters in your hand, feel Earth’s gravity pull on them, and you have an idea how little thrust they generate. They can’t be used for launching spacecraft from bodies with strong gravity. Their strength lies in continuing to generate thrust over time. This means that they can achieve very high top speeds. Ion thrusters can propel spacecraft to speeds over 320,000 kp/h (200,000 mph), but they must be in operation for a long time to achieve that speed.

An ion is an atom or a molecule that has either lost or gained an electron, and therefore has an electrical charge. So ionization is the process of giving a charge to an atom or a molecule, by adding or removing electrons. Once charged, an ion will want to move in relation to a magnetic field. That’s at the heart of ion drives. But certain atoms are better suited for this. NASA’s ion drives typically use xenon, an inert gas, because there’s no risk of explosion.

Detail of an ion drive. Image: NASA Glenn Research Center. Vectorization by Chabacano

In an ion drive, the xenon isn’t a fuel. It isn’t combusted, and it has no inherent properties that make it useful as a fuel. The energy source for an ion drive has to come from somewhere else. This source can be electricity from solar cells, or electricity generated from decay heat from a nuclear material.

Ions are created by bombarding the xenon gas with high energy electrons. Once charged, these ions are drawn through a pair of electrostatic grids—called lenses—by their charges, and are expelled out of the chamber, producing thrust. This discharge is called the ion beam, and it is again injected with electrons, to neutralize its charge. Here’s a short video showing how ion drives work:

Unlike a traditional chemical rocket, where its thrust is limited by how much fuel it can carry and burn, the thrust generated by an ion drive is only limited by the strength of its electrical source. The amount of propellant a craft can carry, in this case xenon, is a secondary concern. NASA’s Dawn spacecraft used only 10 ounces of xenon propellant—that’s less than a soda can—for 27 hours of operation.

NASA Evolutionary Xenon Thruster. Image Credit: NASA

In theory, there is no limit to the strength of the electrical source powering the drive, and work is being done to develop even more powerful ion thrusters than we currently have. In 2012, NASA’s Evolutionary Xenon Thruster (NEXT) operated at 7000w for over 43,000 hours, in comparison to the ion drive on DS1 that used only 2100w. NEXT, and designs that will surpass it in the future, will allow spacecraft to go on extended missions to multiple asteroids, comets, the outer planets, and their moons.

Missions using ion propulsion include NASA’s Dawn mission, the Japanese Hayabusa mission to asteroid 25143 Itokawa, and the upcoming ESA missions Bepicolombo, which will head to Mercury in 2017, and LISA Pathfinder, which will study low frequency gravitational waves.

With the constant improvement in ion propulsion systems, this list will only grow.

About Evan Gough

Evan Gough lives on the West Coast of Canada with his wife and daughter, where he plays in the mountains and works as a technical writer.

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The National Aeronautics and Space Administration (NASA) is the United States government agency responsible for the civilian space program as well as aeronautics and aerospace research. President Dwight D. Eisenhower established the National Aeronautics and Space Administration (NASA) in 1958 with a distinctly civilian (rather than military) orientation encouraging peaceful applications in space science. The National Aeronautics and Space Act was passed on July 29, 1958, disestablishing NASA's predecessor, the National Advisory Committee for Aeronautics (NACA). The new agency became operational on October 1, 1958.

UFO SIGHTINGS PHOTO PHOTOGRAPHY

The Oxford English Dictionary defines a UFO as "An unidentified flying object; a 'flying saucer'." The first published book to use the word was authored by Donald E. Keyhoe. The acronym "UFO" was coined by Captain Edward J. Ruppelt, who headed Project Blue Book, then the USAF's official investigation of UFOs. He wrote, "Obviously the term 'flying saucer' is misleading when applied to objects of every conceivable shape and performance. For this reason the military prefers the more general, if less colorful, name: unidentified flying objects. UFO (pronounced Yoo-foe) for short." Other phrases that were used officially and that predate the UFO acronym include "flying flapjack", "flying disc", "unexplained flying discs", "unidentifiable object", and "flying saucer". The phrase "flying saucer" had gained widespread attention after the summer of 1947. On June 24, a civilian pilot named Kenneth Arnold reported seeing nine objects flying in formation near Mount Rainier. Arnold timed the sighting and estimated the speed of discs to be over 1,200 mph (1,931 km/h). At the time, he described the objects' shape as being somewhat disc-like or saucer-like, leading to newspaper accounts of "flying saucers" and "flying discs". In popular usage the term UFO came to be used to refer to claims of alien spacecraft. and because of the public and media ridicule associated with the topic, some investigators prefer to use such terms as unidentified aerial phenomenon (or UAP) or anomalous phenomena, as in the title of the National Aviation Reporting Center on Anomalous Phenomena (NARCAP).

UFO PHOTO PHOTOGRAPHY

UFO - Unidentified Flying Object An unidentified flying object, or UFO, in its most general definition, is any apparent anomaly in the sky that is not identifiable as a known object or phenomenon. Culturally, UFOs are associated with claims of visitation by extraterrestrial life or government-related conspiracy theories, and have become popular subjects in fiction. While UFOs are often later identified, sometimes identification may not be possible owing to the usually low quality of evidence related to UFO sightings (generally anecdotal evidence and eyewitness accounts). Stories of fantastical celestial apparitions have been told since antiquity, but the term "UFO" (or "UFOB") was officially created in 1953 by the United States Air Force (USAF) to serve as a catch-all for all such reports. In its initial definition, the USAF stated that a "UFOB" was "any airborne object which by performance, aerodynamic characteristics, or unusual features, does not conform to any presently known aircraft or missile type, or which cannot be positively identified as a familiar object." Accordingly, the term was initially restricted to that fraction of cases which remained unidentified after investigation, as the USAF was interested in potential national security reasons and/or "technical aspects" (see Air Force Regulation 200-2). During the late 1940s and through the 1950s, UFOs were often referred to popularly as "flying saucers" or "flying discs". The term UFO became more widespread during the 1950s, at first in technical literature, but later in popular use. UFOs garnered considerable interest during the Cold War, an era associated with a heightened concern for national security. Various studies have concluded that the phenomenon does not represent a threat to national security nor does it contain anything worthy of scientific pursuit (e.g., 1951 Flying Saucer Working Party, 1953 CIA Robertson Panel, USAF Project Blue Book, Condon Committee).

Photos of Nature | Nature Photography What is The Universe

Photos of Nature | Nature Photography What is The Universe

Sunday, November 8, 2015