Puricare Industrial Enterprises: October 2020

Saturday, October 31, 2020

SOLAR SAILS - Solar sails are a spacecraft propulsion method utilizing a curious quirk of photons. These particles of light have no mass and yet when they impinge on something, they can impart momentum and provide a tiny push. You get shoved by photons every time you step out into the sunshine but their incredibly small force is essentially unnoticeable to your body. In space, things take a different turn. The laws of physics state that every action must have an equal and opposite reaction, so, when photons from the sun bounce off a spaceship, the ship is propelled ever so slightly in a direction away from the sun. With a single photon the change is negligible but a large collection of them can provide significant thrust. Place a large, flat, mirror-like sheet in front of a spacecraft and the sun's power will push it forward. The material must also be strong and gossamer-thin in order to catch and control the sunlight. Solar sails can tack like regular sails to travel in many directions, according to the Planetary Society. The technology has an advantage over other propulsion methods because a ship does not need to carry fuel wherever it goes, instead relying on the freely-available light of stars. Since they get a continuous push from the sun, solar-sail-powered ships can constantly accelerate as they journey to the edge of the solar system, achieving super-fast speeds that would be much more difficult for chemical rockets.

This artist's conception shows a solar sail high above the Earth.

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Solar Sails

What Is a Solar Sail?

By Adam Mann

Like mariners of ancient days, cosmic adventurers might one day harness the power of sails to journey through the stars.

But rather than the ocean's wind, future space travelers would use sunlight to drive a technology known as a solar sail.

How do solar sails work?

Solar sails are a spacecraft propulsion method utilizing a curious quirk of photons.

These particles of light have no mass and yet when they impinge on something, they can impart momentum and provide a tiny push.

You get shoved by photons every time you step out into the sunshine but their incredibly small force is essentially unnoticeable to your body.

In space, things take a different turn.

The laws of physics state that every action must have an equal and opposite reaction, so, when photons from the sun bounce off a spaceship, the ship is propelled ever so slightly in a direction away from the sun.

With a single photon the change is negligible but a large collection of them can provide significant thrust.

Place a large, flat, mirror-like sheet in front of a spacecraft and the sun's power will push it forward.

The material must also be strong and gossamer-thin in order to catch and control the sunlight.

Solar sails can tack like regular sails to travel in many directions, according to the Planetary Society.

The technology has an advantage over other propulsion methods because a ship does not need to carry fuel wherever it goes, instead relying on the freely-available light of stars.

Since they get a continuous push from the sun, solar-sail-powered ships can constantly accelerate as they journey to the edge of the solar system, achieving super-fast speeds that would be much more difficult for chemical rockets.

Alternatively, solar sails can also be driven by gargantuan laser beams.

Examples of solar sails

NASA tested the concept of solar sailing in 1974 with its Mariner 10 spacecraft, which was designed to fly past Venus and Mercury.

When the probe ran out of fuel, mission control turned its solar panels to just the right angle to catch the sun's rays and push the spacecraft forward.

The first human-made solar sail to successfully fly was the Japanese Space Exploration Agency's Interplanetary Kite-craft Accelerated by Radiation Of the Sun (IKAROS) spacecraft.

The robot deployed its 46-foot-wide (14 meters) sail in June 2010 and proved the ability to control its direction and change orientation on command.

That same year, NASA launched the tiny NanoSail-D demonstrator mission, which had a diamond-shaped sail 10 feet (3 m) to a side.

The probe unfurled its solar sail in 2011 and circled the Earth for eight months before burning up in the atmosphere.

Lightweight and with little room to carry fuel, small satellites are thought to be ideal candidates for this type of propulsion.

In 2015, the Planetary Society launched the LightSail-1 spacecraft into orbit, which sported a 344-square-foot (32-square-m) solar sail, about the size of a boxing ring.

Despite some successes, and a selfie or two, the mission suffered from technical glitches and eventually stopped transmitting signals before entering the atmosphere a few weeks after it was launched.

But the Planetary Society is back at it and has high hopes for their new LightSail-2 mission. Launching at the end of June 2019, the craft is about the size of a bread loaf and intends to release a similarly-sized sail as its predecessor.

Mission planners said that one day solar-sail-driven ships could travel to the edge of the solar system or beyond.

The Breakthrough Starshot Initiative intends to do just that, sending lightweight microchip-sized probes to explore the nearest star system, Alpha Centauri, which is 4.3 light-years away.

Announced in 2016, the $100-million venture is investigating the feasibility of using a colossal Earth-based laser to accelerate the chips to 20% the speed of light and reaching Alpha Centauri in only 20 years.

Adam Mann is a journalist specializing in astronomy and physics stories. His work has appeared in the Wall Street Journal, Wired, Nature, Science, New Scientist, and many other places. He lives in Oakland, California, where he enjoys riding his bike. Follow him on Twitter @adamspacemann.

https://www.space.com/solar-sail.html

Wednesday, October 28, 2020

WHAT MAKES SOMETHING FIREPROOF - Nowadays many modern materials are less combustible than they used to be. The term "fireproof" is actually a misnomer, because almost anything containing carbon, if hot enough, can combust and catch fire. "Fire resistant" and "flame retardant" are more accurate terms. When used properly, these fire protective measures can interrupt the burning process. For instance, typical plastic is combustible because it has a lot of carbon and hydrogen available to fuel a fire. Gasoline also has carbon and hydrogen available — and it's volatile, so gasoline can evaporate easily, making it highly combustible. In contrast, a fire resistant material is one that doesn't burn easily. One example of this is the artificial stone used in kitchen countertops, like the DuPont brand Corian. The plastic of a Corian countertop is filled with finely ground rocks made of hydrated aluminum oxide, a chemical compound that doesn't burn. These rocks lower the fuel value (the amount of carbon available for combustion) of the countertop, making it more fire resistant. The aluminum oxide brought water with it, so when you compounded the two together [the plastic and hydrated aluminum oxide], what you in essence had was rocks that on a microscopic basis were wet. And you had them in a plastic matrix, so it was really, really hard to get any heat generated from this. Although the rock attracts and holds water molecules, it does not get wet enough to form a puddle. Water keeps the countertop cool and helps block heat from getting any fuel. Countertops like Corian don't have much plastic — there's just enough to hold the rock together.

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It looks like this chair could use some flame retardant.

What makes something fireproof?

Why do some things burn easily and others don't?

By Dani Leviss - Live Science Contributor

On Dec. 30, 1903, a spark from a stage light set Chicago's Iroquois Theatre ablaze.

"The stage and the curtain and the rest caught fire," said Bill Carroll, grandson of the theatre's co-owner and adjunct professor of chemistry at Indiana University Bloomington.

"There were insufficient exits, and it was terrible."

Over 600 people died in the disaster — the deadliest single-building fire in U.S. history.

Nowadays, this probably wouldn't happen, because many modern materials are less combustible than they used to be.

But what makes certain materials fireproof?

The term "fireproof" is actually a misnomer, because almost anything containing carbon, if hot enough, can combust and catch fire.

"Fire resistant" and "flame retardant" are more accurate terms, Carroll told Live Science.

When used properly, these fire protective measures can interrupt the burning process.

For instance, typical plastic is combustible because it has a lot of carbon and hydrogen available to fuel a fire.

Gasoline also has carbon and hydrogen available — and it's volatile, so gasoline can evaporate easily, making it highly combustible.

In contrast, a fire resistant material is one that doesn't burn easily.

One example of this is the artificial stone used in kitchen countertops, like the DuPont brand Corian.

The plastic of a Corian countertop is filled with finely ground rocks made of hydrated aluminum oxide, a chemical compound that doesn't burn.

These rocks lower the fuel value (the amount of carbon available for combustion) of the countertop, making it more fire resistant, Carroll said.

"The aluminum oxide brought water with it, so when you compounded the two together [the plastic and hydrated aluminum oxide], what you in essence had was rocks that on a microscopic basis were wet," he said.

"And you had them in a plastic matrix, so it was really, really hard to get any heat generated from this."

Although the rock attracts and holds water molecules, it does not get wet enough to form a puddle.

Water keeps the countertop cool and helps block heat from getting any fuel.

If there were a heat source (for instance, a lit cigarette resting on a Corian countertop), it would need to boil away the water surrounding the aluminum oxide first in order to then heat up the fuel, or the plastic molecules, enough to burn.

Moreover, countertops like Corian don't have much plastic — there's just enough to hold the rock together, Carroll said.

Fuel and heat are two sides of the fire tetrahedron, a triangular pyramid in which each side represents the elements necessary for fire.

The other two sides are oxygen and a sustainable chemical reaction, Carroll explained.

Most materials — aside from granite and asbestos, which are among the rare materials that are actually, literally fireproof — can be made more or less combustible only by eliminating one or more sides of the fire tetrahedron, he said.

The fire tetrahedron includes heat, fuel, oxygen and a sustainable chain reaction.

Unlike fire resistance — the properties that make it hard for a fire to either start in the first place or keep going — chemicals known as flame retardants can help to slow or extinguish an already-burning fire.

Chemical flame retardants contain chlorine, bromine, nitrogen, phosphorus, boron or metals.

One way flame retardants work is through the formation of a substance known as char foam.

When a piece of toast burns, for example, a char forms on the outside, which insulates the undamaged bread on the inside.

Once a fire starts on an object treated with a char foam-inducing flame retardant, a chemical reaction within the retardant bubbles up to create a rigid, inflammable foam out of the char from the initial burning.

This char foam then insulates the fuel from oxygen and, to some extent, heat, Carroll said. "[The char] kind of builds its own cocoon."

Flame retardant use has mushroomed since the 1970s, but it has sparked a controversy over the past few decades because of its potential toxicity.

Brominated fire retardant chemicals, banned in the U.S. since 2004, worked well at putting out fires, but weren't permanently bound to the material, for example a mattress, Carroll said.

That meant the chemical could potentially leave the mattress and end up in the dust or air, where it could be inhaled or ingested.

That's cause for concern, because these chemicals are linked to a slew of health problems; for instance they might disrupt thyroid function, interrupt the immune system and increase cancer risk, according to the National Institute of Environmental Health Sciences.

"New strategies for making fire retardants [are] to either bind the chemical to the mattress or make it another polymer [a long, repeating molecule chain], another absolutely huge molecule that doesn't migrate," he told Live Science.

In contrast, brominated fire retardants are smaller molecules that can easily leave materials and objects.

Can fire resistant materials and flame retardants be relied upon for fire safety?

They do work well, but think of them as the second line of defense, Carroll said.

Although it may seem like rather simple advice, keep fire, such as candles, out of bedrooms and carefully tend to stoves and other fire sources in the kitchen.

"Don't have a fire where you don't want a fire in the first place," he said.

Dani Leviss

Live Science Contributor

Dani Leviss is a freelance science writer who covers water, animals, art, chemistry and technology. She has written for Scholastic, Hakai Magazine, IEEE Earthzine and News-O-Matic. Born and raised in New Jersey, Dani studied chemistry by day and edited the student newspaper at Drew University by night. She completed her master's degree in science journalism at NYU. When not writing, you'll find Dani walking her dog, painting or gardening.

https://www.livescience.com/how-fireproofing-works.html

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