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  • richardmitnick 10:05 am on March 30, 2020 Permalink | Reply
    Tags: , ESA's proposed Hera spaceraft, NASA's DART (Double Asteroid Redirection Test) mission, NASA's Evolutionary Xenon Thruster – Commercial (NEXT-C), NEXT-C is a powerful engine. It's nothing like a rocket which requires a massive amount of thrust to lift something away from Earth's gravity., , The Italian Space Agency is providing LICIA (Light Italian CubeSat for Imaging of Asteroids) for the mission., This Epic Ion Engine Will Power NASA's Test Mission to Redirect an Asteroid, Tiny binary asteroid system called Didymos   

    From Science Alert: “This Epic Ion Engine Will Power NASA’s Test Mission to Redirect an Asteroid” 

    ScienceAlert

    From Science Alert

    29 MARCH 2020
    EVAN GOUGH

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    (NASA/Bridget Caswell)

    Despite humanity’s current struggle against the novel coronavirus, and despite it taking up most of our attention, other threats still exist. The very real threat of a possible asteroid strike on Earth in the future is taking a backseat for now, but it’s still there.

    Though an asteroid strike seems kind of ephemeral right now, it’s a real threat, and one that has the potential to end humanity. Agencies like NASA and the ESA are still working on their plans to protect us from that threat.

    NASA’s DART (Double Asteroid Redirection Test) mission is scheduled to launch on 22 July 2021.

    NASA DART Double Impact Redirection Test vehicle depiction schematic

    It’s a demonstration mission to study the use of kinetic impact to deflect an asteroid. It’ll head for the tiny binary asteroid system called Didymos, (or 65803 Didymos.) This double asteroid system poses no threat to Earth.

    The larger of the pair, named Didymos A, is about 780 meters (2560 ft.) in diameter, while the smaller one, Didymos B, is only about 160 meters (535 feet) DART will crash itself into the Didymos B. It’s close to the typical size of an asteroid that threatens Earth.

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    A simulated image of the Didymos binary asteroid. (Naidu et al., AIDA Workshop, 2016)

    DART has a lot of space to cover to reach Didymos. After launching in July 2021, it will reach its target in September 22, when the binary asteroid is within 11 million km (6.8 million miles) of Earth. And to get there, it’ll rely on a powerful ion engine called NASA’s Evolutionary Xenon Thruster – Commercial (NEXT-C).

    The engine comes in two primary components: the thruster and the power processing unit (PPU.) NEXT-C is getting ready for the mission with a series of tests, both performance and environmental.

    The thruster was put through vibration, thermal vacuum and performance tests before being integrated with its PPU. It was also subjected to simulated spaceflight conditions: the extreme vibration during launch, and the extreme cold of space.

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    The power processing unit of the thruster is removed from another vacuum chamber after successful testing. (NASA/Bridget Caswell)

    NEXT-C is a powerful engine. It’s nothing like a rocket, which requires a massive amount of thrust to lift something away from Earth’s gravity. But in terms of ion drives, it’s a very powerful unit. It’s about three times more powerful than the NSTAR ion drives on NASA’s DAWN and Deep Space One spacecraft.

    NASA/DLR Dawn Spacecraft (2007-2018)

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    Deep Space One spacecraft. Wikipedia

    NEXT can produce 6.9 kW thrust power and 236 mN thrust. The engine has produced the highest total impulse of any ion engine: 17 MN·s. It also has a specific impulse, which is a measure of how efficiently it uses propellant, of 4,190 seconds, compared to NSTAR’s 3,120.

    Ion drives don’t burn fuel like a rocket, though they do use a propellant. Typically the propellant is xenon, like in NEXT-C. The NEXT-C ion engine is a double-grid system.

    The xenon is fed into a chamber, where it encounters the first, or upstream, grid. Solar arrays provide the electricity, and the first grid is charged positive. As the xenon ions pass through the upstream grid, they are charged positively.

    This draws them toward the second or accelerator grid, which is charged negatively. This propels them out of the engine, providing thrust. The thrust is equal to the force between the upstream ions and the accelerator grid.

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    NASA Evolutionary Xenon Thruster being tested in a vacuum chamber. (NASA)

    When DART reaches the Didymos binary asteroid, it will have some company. The Italian Space Agency is providing LICIA (Light Italian CubeSat for Imaging of Asteroids) for the mission.

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    https://www.nanosats.eu/sat/liciacube

    LICIA is 6 cubesats that will separate from DART prior to impact with Didymos B. It’ll capture images of the impact and the debris ejected from the collision and transmit it back to Earth.

    The impact is expected to change Didymos B’s orbital velocity by about a half millimeter per second. That will change its rotation period by a large enough amount that Earth-based telescopes will detect it. It will also leave a crater in the surface, about 20 m (66 ft) wide.

    Though DART will be destroyed when it impacts, the ESA is planning a follow-up mission. It’s called Hera, and it’s scheduled to launch in 2024, and to arrive in 2027.

    ESA’s proposed Hera spaceraft depiction

    Hera will investigate not only the effect of DART’s impact, but will carry a suite of instruments to learn more about binary asteroids, and the interior of the asteroid.

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

     
  • richardmitnick 8:04 am on April 23, 2019 Permalink | Reply
    Tags: , , , , , , , ESA's proposed Hera spaceraft, , NASA's Deep Impact spacecraft 2004, US Double Asteroid Redirect Test or DART spacecraft   

    From European Space Agency: “Earth vs. asteroids: humans strike back” 

    ESA Space For Europe Banner

    From European Space Agency

    22 April 2019

    Incoming asteroids have been scarring our home planet for billions of years. This month humankind left our own mark on an asteroid for the first time: Japan’s Hayabusa2 spacecraft dropped a copper projectile at very high speed in an attempt to form a crater on asteroid Ryugu. A much bigger asteroid impact is planned for the coming decade, involving an international double-spacecraft mission.

    JAXA/Hayabusa 2 Credit: JAXA/Akihiro Ikeshita

    On 5 April, Hayabusa2 released an experiment called the ‘Small Carry-on Impactor’ or SCI for short, carrying a plastic explosive charge that shot a 2.5-kg copper projectile at the surface of the 900-m diameter Ryugu asteroid at a velocity of around 2 km per second. The objective is to uncover subsurface material to be brought back to Earth for detailed analysis.

    “We are expecting it to form a distinctive crater,” comments Patrick Michel, CNRS Director of Research of France’s Côte d’Azur Observatory, serving as co-investigator and interdisciplinary scientist on the Japanese mission. “But we don’t know for sure yet, because Hayabusa2 was moved around to the other side of Ryugu, for maximum safety.

    “The asteroid’s low gravity means it has an escape velocity of a few tens of centimetres per second, so most of the material ejected by the impact would have gone straight out to space. But at the same time it is possible that lower-velocity ejecta might have gone into orbit around Ryugu and might pose a danger to the Hayabusa2 spacecraft.

    “So the plan is to wait until this Thursday, 25 April, to go back and image the crater. We expect that very small fragments will meanwhile have their orbits disrupted by solar radiation pressure – the slow but persistent push of sunlight itself. In the meantime we’ve also been downloading images from a camera called DCAM3 that accompanied the SCI payload to see if it caught a glimpse of the crater and the early ejecta evolution.”

    According to simulations, the crater is predicted to have a roughly 2 m diameter, although the modelling of impacts in such a low-gravity environment is extremely challenging. It should appear darker than the surrounding surface, based on a February touch-and-go sampling operation when Hayabusa2’s thrusters dislodged surface dust to expose blacker material underneath.

    “For us this is an exciting first data point to compare with simulations,” adds Patrick, “but we have a much larger impact to look forward to in future, as part of the forthcoming double-spacecraft Asteroid Impact & Deflection Assessment (AIDA) mission.

    “In late 2022 the US Double Asteroid Redirect Test or DART spacecraft will crash into the smaller of the two Didymos asteroids.

    NASA DART Double Impact Redirection Test vehicle depiction schematic

    As with Hayabusa2’s SCI test it should form a very distinct crater and expose subsurface material in an even lower gravity environment, but its main purpose is to actually divert the orbit of the 160 m diameter ‘Didymoon’ asteroid in a measurable way.”

    The DART spacecraft will have a mass of 550 kg, and will strike Didymoon at 6 km/s. Striking an asteroid five times smaller with a spacecraft more than 200 times larger and moving three times faster should deliver sufficient impact energy to achieve the first ever asteroid deflection experiment for planetary defence.

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    DART mission profile. APL – Johns Hopkins University Applied Physics Laboratory

    A proposed ESA mission called Hera would then visit Didymos to survey the diverted asteroid, measure its mass and perform high-resolution mapping of the crater left by the DART impact.

    DLR Asteroid Framing Camera used on NASA Dawn and ESA HERA missions

    ESA’s proposed Hera spaceraft

    “The actual relation between projectile size, speed and crater size in low gravity environments is still poorly understood,” adds Patrick, also serving as Hera’s lead scientist. “Having both SCI and Hera data on crater sizes in two different impact speed regimes will offer crucial insights.

    “These scaling laws are also crucial on a practical basis, because they underpin how our calculations estimating the efficiency of asteroid deflection are made, taking account the properties of the asteroid material as well as the impact velocity involved.

    “This is why Hera is so important; not only will we have DART’s full-scale test of asteroid deflection in space, but also Hera’s detailed follow-up survey to discover Didymoon’s composition and structure. Hera will also record the precise shape of the DART crater, right down to centimetre scale.

    “So, building on this Hayabusa2 impact experiment, DART and Hera between them will go on to close the gap in asteroid deflection techniques, bringing us to a point where such a method might be used for real.”

    Didymoon will also be by far the smallest asteroid ever explored, so will offer insights into the cohesion of material in an environment whose gravity is more than a million times weaker than our own – an alien situation extremely challenging to simulate.

    In 2004, NASA’s Deep Impact spacecraft launched an impactor into comet Tempel 1. The body was subsequently revisited, but the artificial crater was hard to pinpoint – largely because the comet had flown close to the Sun in the meantime, and its heating would have modified the surface.

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    NASA’s Deep Impact hitting a comet

    NASA Deep Impact spacecraft 2004

    Hera will visit Didymoon around four years after DART’s impact, but because it is an inactive asteroid in deep space, no such modification will occur. “The crater will still be ‘fresh’ for Hera,” Patrick concludes.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.

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