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vox_mundi

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Re: Astronomical news
« Reply #400 on: October 19, 2020, 04:19:58 PM »
Spacecraft Design Could Get to Titan in Only 2 years Using a Direct Fusion Drive
https://phys.org/news/2020-10-spacecraft-titan-years-fusion.html



The concept fusion drive, called a direct fusion drive (or DFD), is in development at the Princeton Plasma Physics Laboratory (PPPL). Scientists and Engineers there, led by Dr. Samuel Cohen, are currently working on the second iteration of it, known as the Princeton field reversed configuration-2 (PFRC-2). Eventually, the system's developers hope to launch it into space to test, and eventually become the primary drive system of spacecraft traveling throughout the solar system.

Though still under development, the engine itself exploits many of the advantages of aneutronic fusion, most notably an extremely high power-to-weight ratio. The fuel for a DFD drive can vary slightly in mass and contains deuterium and a helium-3 isotope. Even with relatively small amounts of extremely powerful fuel, the DFD can outperform the chemical or electric propulsion methods that are commonly used today. The specific impulse of the system, which is a measure of how effectively an engine uses fuel, is estimated to be comparable to electrical engines, the most efficient currently available. In addition, the DFD engine would provide 4-5 N of thrust in low power mode, only slightly less than what a chemical rocket would output over long periods of time. Essentially, the DFD takes the excellent specific impulse of electric propulsion systems and combines it with the excellent thrust of chemical rockets, for a combination that melds the best of both flight systems.



All of those improved specifications are great, but in order to be useful, they actually have to get a spacecraft somewhere. The paper's authors picked Titan, largely because it's relatively far away, but also extremely interesting due to its liquid cycles and abundant organic molecules.

Spacecraft performance, planetary alignments and orbital mechanics resulted in two different potential paths, one where constant thrust was only applied at the beginning and the end of the journey (called a thrust-coast-thrust—TCT—profile) and one in which the thrust was constant for the duration of the journey.

Both journeys involved switching the direction of thrust to slow the spacecraft down to enter into the Saturnian system. Providing constant thrust would put the journey at a little less than two years, while the TCT profile would result in a total trip duration of 2.6 years for a spacecraft much larger than Cassini. Both of those paths would not require any gravity assists, which spacecraft traveling to the outer planets have regularly benefited from.

... With all the orbital mechanics out of the way and the spacecraft safely in Titan's orbit, it can begin to take advantage of another of the DFD's benefits—it can provide direct power to the spacecraft's systems. Most outer solar system missions rely on radioisotope thermal generators (RTGs) for their power source. But a DFD is, in fact, a power source in addition to being a source of thrust. If designed correctly, it could provide all the power a spacecraft needs for an extended mission lifespan.



Trajectory design for a Titan mission using the Direct Fusion Drive:
https://webthesis.biblio.polito.it/15184/1/tesi.pdf
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Tom_Mazanec

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Re: Astronomical news
« Reply #401 on: October 19, 2020, 05:12:13 PM »
Two years to Titan is good, but what would be a game changer is a reasonable time to 550 AU from the sun, to take advantage of the solar gravitational focus.
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vox_mundi

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Re: Astronomical news
« Reply #402 on: October 21, 2020, 01:58:15 PM »
NASA Probe OSIRIS-REx 'Boops' Asteroid Bennu In Historic Mission
https://phys.org/news/2020-10-nasa-probe-osiris-rex-boops-asteroid.html



After a four-year journey, NASA's robotic spacecraft OSIRIS-REx briefly touched down on asteroid Bennu's boulder-strewn surface on Tuesday to collect rock and dust samples in a precision operation 200 million miles (330 million kilometers) from Earth.

... If OSIRIS-REx successfully comes home in September 2023, it will have collected the largest sample returned from space since the Apollo era.

... Scientists want at least 60 grams but the spacecraft is capable of picking up as much as two kilograms, or five pounds.

If it turns out the spacecraft didn't collect enough, it will have another go on January 12, 2021, at a backup site which is another relatively boulder-free area near the rock's equator.

https://www.nasa.gov/osiris-rex
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Tor Bejnar

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Re: Astronomical news
« Reply #403 on: October 21, 2020, 10:45:16 PM »
Quote
... Scientists want at least 60 grams but the spacecraft is capable of picking up as much as two kilograms, or five pounds.
On Earth, 2 kg ~ 5 lb., but on the asteroid, way less than a pound (link).  (2 kg on Pluto is about 0.3 lbs.)
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vox_mundi

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“There are three classes of people: those who see. Those who see when they are shown. Those who do not see.” ― Leonardo da Vinci

Insensible before the wave so soon released by callous fate. Affected most, they understand the least, and understanding, when it comes, invariably arrives too late

Sigmetnow

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Re: Astronomical news
« Reply #405 on: October 22, 2020, 02:57:13 AM »
Quote
... If OSIRIS-REx successfully comes home in September 2023, it will have collected the largest sample returned from space since the Apollo era.

But we’ll be collecting and returning lots of moon regolith before then. 
Probably.

“The sampling event brought the spacecraft all the way down to sample site Nightingale, touching down within three feet (one meter) of the targeted location.”  8)
People who say it cannot be done should not interrupt those who are doing it.

vox_mundi

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Re: Astronomical news
« Reply #406 on: October 24, 2020, 07:36:23 AM »
NASA’s OSIRIS-REx Spacecraft Collects Significant Amount of Asteroid
https://www.nasa.gov/press-release/nasa-s-osiris-rex-spacecraft-collects-significant-amount-of-asteroid




Two days after touching down on asteroid Bennu, NASA’s OSIRIS-REx mission team received on Thursday, Oct. 22, images that confirm the spacecraft has collected more than enough material to meet one of its main mission requirements – acquiring at least 2 ounces (60 grams) of the asteroid’s surface material.

The spacecraft captured images of the sample collector head as it moved through several different positions. In reviewing these images, the OSIRIS-REx team noticed both that the head appeared to be full of asteroid particles, and that some of these particles appeared to be escaping slowly from the sample collector, called the Touch-And-Go Sample Acquisition Mechanism (TAGSAM) head. They suspect bits of material are passing through small gaps where a mylar flap – the collector’s “lid” – is slightly wedged open by larger rocks.

The images also show that any movement to the spacecraft and the TAGSAM instrument may lead to further sample loss. To preserve the remaining material, the mission team decided to forego the Sample Mass Measurement activity originally scheduled for Saturday, Oct. 24, and canceled a braking burn scheduled for Friday to minimize any acceleration to the spacecraft.

From here, the OSIRIS-Rex team will focus on stowing the sample in the Sample Return Capsule (SRC), where any loose material will be kept safe during the spacecraft’s journey back to Earth.

https://www.theguardian.com/science/2020/oct/23/nasa-spacecraft-osiris-rex-asteroid-rubble
« Last Edit: October 24, 2020, 07:41:31 AM by vox_mundi »
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vox_mundi

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Re: Astronomical news
« Reply #407 on: October 26, 2020, 05:53:24 PM »
NASA’s SOFIA Discovers Water on Sunlit Surface of Moon
https://www.nasa.gov/press-release/nasa-s-sofia-discovers-water-on-sunlit-surface-of-moon/



NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA) has confirmed, for the first time, water on the sunlit surface of the Moon. This discovery indicates that water may be distributed across the lunar surface, and not limited to cold, shadowed places.

SOFIA has detected water molecules (H2O) in Clavius Crater, one of the largest craters visible from Earth, located in the Moon’s southern hemisphere. Previous observations of the Moon’s surface detected some form of hydrogen, but were unable to distinguish between water and its close chemical relative, hydroxyl (OH). Data from this location reveal water in concentrations of 100 to 412 parts per million – roughly equivalent to a 12-ounce bottle of water – trapped in a cubic meter of soil spread across the lunar surface. The results are published in the latest issue of Nature Astronomy.

As a comparison, the Sahara desert has 100 times the amount of water than what SOFIA detected in the lunar soil. Despite the small amounts, the discovery raises new questions about how water is created and how it persists on the harsh, airless lunar surface.


Clavius Base - 2001: A Space Odyssey

https://www.nature.com/articles/s41550-020-01222-x

-----------------------------------------------

Tiny Moon Shadows May Harbor Hidden Stores of Ice
https://phys.org/news/2020-10-tiny-moon-shadows-harbor-hidden.html

Hidden pockets of water could be much more common on the surface of the moon than scientists once suspected, according to new research led by the University of Colorado Boulder. In some cases, these tiny patches of ice might exist in permanent shadows no bigger than a penny.

"If you can imagine standing on the surface of the moon near one of its poles, you would see shadows all over the place," said Paul Hayne, assistant professor in the Laboratory of Atmospheric and Space Physics at CU Boulder. "Many of those tiny shadows could be full of ice."

In a study published today in the journal Nature Astronomy, Hayne and his colleagues explored phenomena on the moon called "cold traps"—shadowy regions of the surface that exist in a state of eternal darkness at -260°F.

Drawing on detailed data from NASA's Lunar Reconnaissance Orbiter, the researchers estimate that the moon could harbor roughly 15,000 square miles of permanent shadows in various shapes and sizes—reservoirs that, according to theory, might also be capable of preserving water via ice. Previous studies estimated less than 7000 square miles.

Moon water has been eyed as a potential resource by NASA, which created a program named Artemis in 2019, to send American astronauts back to the moon this decade. Launching water to space costs thousands of dollars per gallon. Future explorers may be able to use lunar water not only to quench their own thirst but to refuel their rockets.

Micro cold traps on the Moon, Nature Astronomy (2020).
https://www.nature.com/articles/s41550-020-1198-9

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« Last Edit: October 26, 2020, 06:10:53 PM by vox_mundi »
“There are three classes of people: those who see. Those who see when they are shown. Those who do not see.” ― Leonardo da Vinci

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vox_mundi

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Re: Astronomical news
« Reply #408 on: October 26, 2020, 07:55:45 PM »
Study Offers More Complete View of Massive Asteroid Psyche
https://phys.org/news/2020-10-view-massive-asteroid-psyche.html



A new study authored by Southwest Research Institute planetary scientist Dr. Tracy Becker discusses several new views of the asteroid 16 Psyche, including the first ultraviolet observations. The study, which was published today in The Planetary Science Journal and presented at the virtual meeting of the American Astronomical Society's Division for Planetary Sciences, paints a clearer view of the asteroid than was previously available.

... "We've seen meteorites that are mostly metal, but Psyche could be unique in that it might be an asteroid that is totally made of iron and nickel," Becker said. "Earth has a metal core, a mantle and crust. It's possible that as a Psyche protoplanet was forming, it was struck by another object in our solar system and lost its mantle and crust."

Becker observed the asteroid at two specific points in its rotation to view both sides of Psyche completely and delineate as much as possible from observing the surface at ul-traviolet (UV) wavelengths.

"We were able to identify for the first time on any asteroid what we think are iron oxide ultraviolet absorption bands," she said. "This is an indication that oxidation is happen-ing on the asteroid, which could be a result of the solar wind hitting the surface."

Becker's study comes as NASA is preparing to launch the spacecraft Psyche, which will travel to the asteroid as part of an effort to understand the origin of planetary cores. The mission is set to launch in 2022. Metal asteroids are relatively rare in the solar system, and scientists believe Psyche could offer a unique opportunity to see inside a planet.



Tracy M. Becker et al, HST UV Observations of Asteroid (16) Psyche, The Planetary Science Journal (2020).
https://iopscience.iop.org/article/10.3847/PSJ/abb67e
“There are three classes of people: those who see. Those who see when they are shown. Those who do not see.” ― Leonardo da Vinci

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Tom_Mazanec

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Re: Astronomical news
« Reply #409 on: October 27, 2020, 11:56:58 AM »
Extreme 'Black Widow' Star Identified as Source of Mystery Gamma Radiation
https://www.sciencealert.com/extreme-record-breaking-black-widow-star-is-the-source-of-mystery-gamma-radiation
Quote
Now, astronomers have solved the mystery and pinned down that second star by searching gamma-ray data obtained between 2008 and 2018. Together, the two stars constitute one of the weirdest binary systems we've ever seen.

"The binary star system and the neutron star at its heart, now known as PSR J1653-0158, set new records," said astronomer Lars Nieder of the Albert Einstein Institute Hannover in Germany.

"We have discovered the galactic dance of a super heavyweight with a flyweight: At slightly more than twice the mass of our Sun, the neutron star is extraordinarily heavy. Its companion has about six times the density of lead, but only about 1 percent the mass of our Sun.

"This 'odd couple' orbits every 75 minutes, more quickly than all known comparable binaries."
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vox_mundi

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Re: Astronomical news
« Reply #410 on: October 27, 2020, 01:23:26 PM »
Massive Asteroid Subject of New Findings
https://phys.org/news/2020-10-massive-asteroid-subject.html

A University of Hawaiʻi Institute for Astronomy (IfA) astronomer has revealed critical new findings linked to a large asteroid expected to pass extremely close to Earth. Dave Tholen and collaborators have announced the detection of Yarkovsky acceleration on the near-Earth asteroid Apophis. This acceleration arises from an extremely weak force on an object due to non-uniform thermal radiation. This force is particularly important for the asteroid Apophis, as it affects the probability of an Earth impact in 2068.

Prior to the detection of Yarkovsky acceleration on Apophis, astronomers had concluded that a potential impact with Earth in 2068 was impossible. The detection of this effect acting on Apophis means that the 2068 impact scenario is still a possibility.


Apophis is noteworthy because of its extremely close approach to the Earth on Friday, April 13, 2029, when the 300 meter-sized asteroid will become visible to the unaided eye as it passes within the belt of communications satellites orbiting the Earth.

Quote
... "The new observations we obtained with the Subaru telescope earlier this year were good enough to reveal the Yarkovsky acceleration of Apophis, and they show that the asteroid is drifting away from a purely gravitational orbit by about 170 meters per year, which is enough to keep the 2068 impact scenario in play."

... Further observations to refine the amplitude of the Yarkovksy effect and how it affects Apophis' orbit are underway. Astronomers will know well before 2068 if there is any chance of an impact.

https://www.hawaii.edu/news/2020/10/26/new-massive-asteroid-findings/

“There are three classes of people: those who see. Those who see when they are shown. Those who do not see.” ― Leonardo da Vinci

Insensible before the wave so soon released by callous fate. Affected most, they understand the least, and understanding, when it comes, invariably arrives too late