My Science School

On July 9, 1979, Voyager 2 made its closest approach to the largest planet in our solar system. Now in interstellar space. Voyager 2 altered some of our ideas about the Jovian system.

The Voyager probes are: humanity's longest running spacecraft as they have been flying since 1977 Both Voyager 2 and Voyager 1 are now in interstellar space, and though their power sources are gradually fading, they are still operational as of now.

It might seem counter-intuitive, but Voyager 2 was the first to be launched on August 20, 1977-about two weeks before the launch of Voyager 1. Both spacecraft were equipped with an extensive array of instruments to gather data. about the outer planets and their systems, in addition to carrying a slow-scan colour TV camera capable of taking images of the planets and their moons.

Based on Mariners

The design of the Voyagers was based on the Mariners and they were even known as Mariner 11 and Mariner 12 until March 7. 1977. It was NASA administrator James Fletcher who announced that the spacecraft would be renamed Younger. The Voyagers are powered by three plutonium dioxide radioisotope thermoelectric generators (RTGS) mounted at the end of a boom (a long metal beam extending from the spacecraft and serving as a structure subsystem).

Even though Voyager 1 was launched a little later, it reached Jupiter first in 1979 as it took a trajectory that put it on a faster path. Voyager 2 began transmitting images of Jupiter from April 24, 1979 for time-lapse movies of atmospheric circulation. For the next three-and-a-half months, until August 5 of that year, the probe continued to click images and collect data. A total of 17,000 images of Jupiter and its system were sent back to the Earth.

The spectacular images of the Jovian system included those of its moons Callisto, Europa, and Ganymede. While Voyager 2 flew by Callisto and Europa at about half the distance between the Earth and its moon, it made an even closer approach to Ganymede.

Ocean worlds

The combined cameras of the two Voyager probes, in fact. covered at least four-fifths of the surfaces of Ganymede and Callisto. This enabled the mapping out of these moons to a resolution of about 5 km.

Voyager 2's work, along with observations made before and after, also helped scientists reveal that each of these moons were indeed an ocean world.

On July 9, 1979, the probe made its closest approach to Jupiter. Voyager 2 came within 6,45,000 km from the planet's surface, less than twice the distance between Earth and its moon. It detected many significant atmospheric changes, including a drift in the Great Red Spot in addition to changes in its shape and colours.

Voyager 2 also relayed photographs of other moons like lo and Amalthea. It even discovered a Jovian satellite, later called Adrastea, and revealed a third component to the planet's rings. The thin rings surrounding Jupiter, as had been seen by Voyager 1 as well, were confirmed by images looking back at the giant planet as the spacecraft departed for Saturn. As the probe used the gravity assist technique, Jupiter served as a springboard for Voyager 2 to get to Saturn.

Studies all four giant planets

 Four decades after its closest approach to Jupiter, Voyager 2 successfully fired up its trajectory correction manoeuvre thrusters on July 8, 2019. These thrusters, which had themselves last been used only in November 1989 during Voyager 2's encounter with Neptune, will be used to control the pointing of the spacecraft in interstellar space.

In those 40 years, Voyager 2 had achieved flybys of Saturn (1981), Uranus (1986), and Neptune (1989), thereby becoming the only spacecraft to study all four giant planets of the solar system at close range. Having entered interstellar space on December 10, 2018, Voyager 2 is now over 132 AU (astronomical unit-distance between Earth and the sun) away from the Earth, still relaying back data from unexplored regions deep in space.

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Researches create lightweight flexible mirrors that can be rolled up during launch and reshaped precisely after deployment.

Mirrors are a significant part of telescopes. When it comes to space telescopes, which have complicated procedures for launching and deploying, the primary mirrors add considerable heft, contributing to packaging difficulties.

Researchers have now come up with a novel way of producing and shaping large, high-quality mirrors. These mirrors are not only thinner than the primary mirrors usually employed in space-based telescopes, but are also flexible enough to be rolled up and stored inside a launch vehicle.

Parabolic membrane mirror

The successful fabrication of such parabolic membrane mirror prototypes up to 30 cm in diameter have been reported in the Optica Publishing Group journal Applied Optics in April. Researchers not only believe that these mirrors could be scaled up to the sizes required in future space telescopes, but have also developed a heat-based method to correct imperfections that will occur during the unfolding process.

Using a chemical vapour deposition process that is commonly used to apply coatings (like the ones that make electronics water-resistant), a parabolic membrane mirror was created for the first time. The mirror was built with the optical qualities required for use in telescopes. A rotating container with a small amount of liquid was added to the inside of a vacuum chamber in order to create the exact shape necessary for a telescope mirror. The liquid forms a perfect parabolic shape onto which a polymer can grow during chemical vapour deposition, forming the mirror base. A reflective metal layer is applied to the top when the polymer is thick enough, and the liquid is then washed away.

Thermal technique

The researchers tested their technique by building a 30-cm-diameter membrane mirror in a vacuum deposition chamber. While the thin and lightweight mirror thus constructed can be folded during the trip to space, it would be nearly impossible to get it into perfect parabolic shape after unpacking. The researchers were able to show that their thermal radiative adaptive shaping method worked well to reshape the membrane mirror.

Future research is aimed at applying more sophisticated adaptive control to find out not only how well the final surface can be shaped, but also how much distortion can be tolerated initially. Additionally, there are also plans to create a metre-sized deposition chamber that would enable studying the surface structure along with packaging unfolding processes for a large-scale primary mirror.

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On April 16-17, 1976, Helios-B made its closest approach to the sun, thereby setting a record for the closest flyby of the sun.

April is here and with it comes searing heat as the sun beats down heavily on most parts of India. You must be aware, however, that the sun, with its entire mass of glowing, boiling heat, is the source of all life on Earth. Our sun, in fact, influences how every object in the solar system is shaped and behaves.

Studying solar processes

This means that learning more about the sun and understanding it better has always been a priority. Apart from studying it from here on Earth, which is what we did for most of our history, we have also started sending spacecraft to explore its secrets. The Helios mission was one such mission, sending out a pair of probes into heliocentric orbit (an orbit around the sun) to study solar processes.

Following the success of the Pioneer probes, which formed a ring of solar weather stations along Earth's orbit to measure solar wind and predict solar storms, the Helios mission was planned. While the Pioneer probes orbited within 0.8 AU (astronomical unit, mean distance between Earth and sun) of the sun, the Helios probes shattered that record within years.

A joint German-American deep-space mission to study solar-terrestrial relationships and many solar processes, it was NASA's largest bilateral project up until then. The Federal Republic of Germany (West Germany) paid around $180 million of the total $260 million cost and provided the spacecraft, while NASA provided the launch vehicles.

Named Helios-A and Helios-B and equipped with state-of-the-art thermal control systems, the pair of probes were renamed Helios 1 and Helios 2 after their launches. Launched late in 1974, Helios 1 passed within 47 million km (0.31 AU) of the sun at a speed of 2,38,000 km per hour on March 15, 1975. While this was clearly the closest any human-made object had ever been to the sun, the record was broken again in a little over a year by its twin probe.

Even though Helios-B was very similar to Helios-A, the second spacecraft had improvements in terms of system design in order to help it survive longer in the harsh conditions it was heading for. Launched early in 1976, Helios 2 was also put into heliocentric orbit like its twin.

Achieves perihelion

Helios 2, however, flew 3 million km closer to the sun when compared to Helios 1. On April 16-17, 1976, Helios 2 achieved its perihelion or closest approach to the sun at a distance of 0.29 AU or 43.432 million km. At that distance, Helios 2 took the record for the closest flyby of the sun, a record that it didn't relinquish for over four decades. It also set a new speed record for a spacecraft in the process, reaching a maximum velocity of 68.6 km/s (2.46.960 km/h).

Helios 2's position relative to the sun meant that it was exposed to 10% more heat or 20 degrees Celsius more heat when compared to Helios 1. In addition to providing information on solar plasma, solar wind, cosmic rays, and cosmic dust, Helios 2 also performed magnetic field and electrical field experiments.

Apart from studying these parameters about the sun and its environment, both Helios 1 and Helios 2 also had the opportunity to observe the dust and ion tails of at least three comets. While data from Helios 1 was received until late 1982, Helios 2's downlink transmitter failed on March 3, 1980. No further usable data was received from Helios 2 and ground controllers shut down the spacecraft on January 7, 1981.

This was done to avoid any possible radio interference with other spacecraft in the future as both probes continue to orbit the sun.

Parker Solar Probe gets closer and faster

After enjoying its position for over 40 years, Helios 2's records were finally broken by NASA's Parker Solar Probe. Launched on August 12, 2018 to study the sun in unprecedented detail, the probe became the first to "touch" the sun during its eighth flyby on April 28, 2021 when it swooped inside the sun's outer atmosphere. Already holding both the distance and speed records, it is expected to further break them both during its 24 orbits of the sun over its seven-year lifespan. When it completed its 15th closest approach to the sun a month ago on March 17, it came within 8.5 million km of the sun's surface.

Picture Credit : Google

 

Researchers have succeeded in printing robotic hands with bones, ligaments and tendons for the first time. Using a new laser scanning technique, the new technology enables the use of different polymers.

Additive manufacturing or 3D printing is the construction of a 3D object from a 3D digital model. The technology behind this has been advancing at great pace and the number of materials that can be used have also expanded reasonably. Until now, 3D printing was limited to fast-curing plastics. The use of slow-curing plastics has now been made possible thanks to a technology developed by researchers at ETH Zurich and a MIT spin-off U.S. start-up, Inhabit. This has resulted in successfully 3D printing robotic hands with bones, ligaments and tendons. The researchers from Switzerland and the U.S. have jointly published the technology and their applications in the journal Nature.

Return to original state

 In addition to their elastic properties that enable the creation of delicate structures and parts with cavities as required, the slow-curing thiolene polymers also return to their original state much faster after bending, making them ideal for the likes of ligaments in robotic hands.

The stiffness of thiolenes can also be fine-tuned as per our requirements to create soft robots. These soft robots will not only be better-suited to work with humans, but will also be more adept at handling delicate and fragile goods.

Scanning, not scraping

In 3D printers, objects are typically produced layer by layer. This means that a nozzle deposits a given material in viscous form and a UV lamp then cures each layer immediately. This method requires a device that scrapes off surface irregularities after each curing step.

While this works for fast-curing plastics, it would fail with slow-curing polymers like thiolenes and epoxies as they would merely gum up the scraper. The researchers involved therefore developed a 3D printing technology that took into account the unevenness when printing the next layer, rather than smoothing out uneven layers. They achieved this using a 3D laser scanner that checked each printed layer for irregularities immediately.

This advancement in 3D printing technology would provide much-needed advantages as the resulting objects not only have better elastic properties, but are also more robust and durable. Combining soft, elastic, and rigid materials would also become much more simpler with this technology.

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