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Ion engines are the best technology for sending spacecraft on long missions. They’re not suitable for launching spacecraft against powerful gravity, but they require minimal propellant compared to rockets, and they drive spacecraft to higher velocities over extended time periods. Ion thrusters are also quiet, and their silence has some scientists wondering if they could use them on Earth in applications where noise is undesirable.

Powered flight is noisy. Helicopters make a horrible racket, and screaming jet engines can make life near an airport almost unbearable. Even small propeller-driven aircraft are noisy. But what if ion engines could be used instead of these louder propulsion systems, at least in some applications where noise is an issue?

Steven Barrett from MIT thinks the idea has merit. Barrett is a Professor of Aeronautics and Astronautics at the Massachusetts Institute of Technology. He’s also the Director of the MIT Laboratory for Aviation and the Environment. “The aim of Steven’s research is to help aviation achieve zero environmental impacts,” the MIT website says. “This includes developing low emissions and noise propulsion technologies for aircraft…” This is where Barrett’s work on ion propulsion comes in.

Barrett’s been interested in an ion propulsion system for many years. In 2018 Barrett and colleagues published an article in the journal Nature titled “Flight of an aeroplane with solid-state propulsion.” Solid-state propulsion systems have no moving parts, so they’re very quiet. The power for flight comes from electroaerodynamics, where electricity moves ions and provides propulsion. Barrett and colleagues call the flow of ions the “ionic wind.” They’ve used it to propel a small test aircraft on steady, stable flights.

“This is the first-ever sustained flight of a plane with no moving parts in the propulsion system,” Barrett said in 2018. “This has potentially opened new and unexplored possibilities for aircraft which are quieter, mechanically simpler, and do not emit combustion emissions.”

This video from 2018 explains Barrett’s work up to that point.

So far, Barrett and his team have successfully demonstrated the concept with a 2.26 kg (5 lb) glider with a 5-meter (16.4 ft) wingspan. The wing is strung with wires like horizontal fencing. Lithium batteries in the fuselage supply current to the wires. The batteries supply a positive charge to the wires along the front and bottom of the wing, while wires along the trailing edge of the wing act as negative electrodes.

The unique battery system supplies 40,000 volts of electricity to the positive wires. The positive charges strip electrons away from air molecules, ionizing them. The newly ionized molecules are then attracted to the negative electrodes at the wing’s trailing edges. This polarity creates the ionic wind that forces air around the wings, creating lift and thrust. As the ionized molecules travel to the negative electrodes, they collide with million of other air molecules, propelling the aircraft forward.

Barrett’s been further developing the idea for a solid-state electroaerodynamic aircraft since publishing the paper in 2018. Now he’s working with the NASA Innovative Advanced Concepts (NIAC) program. In an article from Feb. 7, 2022, Barrett explained the current state of the idea.

“Advanced air mobility (AAM) is an aviation ecosystem that envisions small, electric, vertical takeoff and landing (VTOL) aircraft operations in urban areas,” he wrote. The problem with that scenario is noise: communities won’t welcome additional noise. Ion electroaerodynamics (EAD) could alleviate that problem.

EAD systems have no moving parts, so they’re nearly silent. The silence benefits several potential missions. “Example missions enabled by silent EAD propulsion include those near noise-sensitive urban communities, or time-critical delivery missions at night (e.g. for critical medical supplies) when community opposition to noise is most severe.”

Ion propulsion benefits from being silent, but it also has a drawback. It generates a low initial thrust. In space travel, this isn’t a problem. For example, NASA used a powerful conventional rocket to launch their DART mission from Earth because conventional rockets develop enough thrust to reach escape velocity. But once DART left Earth and its gravity behind, it used an ion drive for propulsion.

Barrett and his team demonstrated that an EAD aircraft could fly in sustained flight. But can one perform a VTOL flight?

Barrett thinks they can. “Novel multi-stage ducted (MSD) EAD thrusters, in which multiple EAD thruster stages are enclosed inside a duct, will be used to increase thrust enough to enable VTOL operations,” Barrett wrote in the February article. “Under this effort, we will design a VTOL-capable, near-silent aircraft powered by MSD thrusters
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Stellar Winds Coming From Other Stars Measured for the First Time

interstellar jpg

An international research team led by the University of Vienna has made a major breakthrough. In a study recently published in Nature Astronomy, they describe how they conducted the first direct measurements of stellar wind in three Sun-like star systems. Using X-ray emission data obtained by the ESA’s X-ray Multi-Mirror-Newton (XMM-Newton) of these stars’ “astrospheres,” they measured the mass loss rate of these stars via stellar winds. The study of how stars and planets co-evolve could assist in the search for life while also helping astronomers predict the future evolution of our Solar System.

The research was led by Kristina G. Kislyakova, a Senior Scientist with the Department of Astrophysics at the University of Vienna, the deputy head of the Star and Planet Formation group, and the lead coordinator of the ERASMUS+ program. She was joined by other astrophysicists from the University of Vienna, the Laboratoire Atmosphères, Milieux, Observations Spatiales (LAMOS) at the Sorbonne University, the University of Leicester, and the Johns Hopkins University Applied Physics Laboratory (JHUAPL).

Astrospheres are the analogs of our Solar System’s heliosphere, the outermost atmospheric layer of our Sun, composed of hot plasma pushed by solar winds into the interstellar medium (ISM). These winds drive many processes that cause planetary atmospheres to be lost to space (aka. atmospheric mass loss). Assuming a planet’s atmosphere is regularly replenished and/or has a protective magnetosphere, these winds can be the deciding factor between a planet becoming habitable or a lifeless ball of rock.

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Logarithmic scale of the Solar System, Heliosphere, and Interstellar Medium (ISM). Credit: NASA-JPL

While stellar winds mainly comprise protons, electrons, and alpha particles, they also contain trace amounts of heavy ions and atomic nuclei, such as carbon, nitrogen, oxygen, silicon, and even iron. Despite their importance to stellar and planetary evolution, the winds of Sun-like stars are notoriously difficult to constrain. However, these heavier ions are known to capture electrons from neutral hydrogen that permeates the ISM, resulting in X-ray emissions. Using data from the XXM-Newton mission, Kislyakova and her team detected these emissions from other stars.

These were 70 Ophiuchi, Epsilon Eridani, and 61 Cygni, three main sequence Sun-like stars located 16.6, 10.475, and 11.4 light-years from Earth (respectively). Whereas 70 Ophiuchi and 61 Cygni are binary systems of two K-type (orange dwarf) stars, Epsilon Eridani is a single K-type star. By observing the spectral lines of oxygen ions, they could directly quantify the total mass of stellar wind emitted by all three stars. For the three stars surveyed, they estimated the mass loss rates to be 66.5±11.1, 15.6±4.4, and 9.6±4.1 times the solar mass loss rate, respectively.

In short, this means that the winds from these stars are much stronger than our Sun’s, which could result from the stronger magnetic activity of these stars. As Kislyakova related in a University of Vienna news release:

“In the solar system, solar wind charge exchange emission has been observed from planets, comets, and the heliosphere and provides a natural laboratory to study the solar wind’s composition. Observing this emission from distant stars is much more tricky due to the faintness of the signal. In addition to that, the distance to the stars makes it very difficult to disentangle the signal emitted by the astrosphere from the actual X-ray emission of the star itself, part of which is “spread” over the field-of-view of the telescope due to instrumental effects.”

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XMM-Newton X-ray image of the star 70 Ophiuchi (left) and
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How to Know How Hard a Hike Will Be

Tet19 047 Me on Teton Crest Trail copy cropped 16 jpg

By Michael Lanza

“How hard will that hike be?” That’s a question that
all dayhikers and backpackers, from beginners to experts, think about all the
time—and it’s not always easy to answer. But there are ways of evaluating the
difficulty of any hike, using readily available information, that can greatly
help you understand what to expect before you even leave home. Here’s

No matter how relatively easy or arduous the hike you’re considering, or where you fall on the spectrum of hiking experience or personal fitness level, this article will tell you exactly how to answer that question—and which questions to ask and what information to seek to reach that answer. This article shares what I’ve learned over four decades of backpacking and dayhiking, including the 10 years I spent as a field editor for Backpacker magazine and even longer running this blog, and this knowledge can help ensure that you and your companions or your family don’t get in over your heads.

Whether you’re new to dayhiking or backpacking, a
parent planning a hike with young kids, or a fit and experienced dayhiker or
backpacker contemplating one of the toughest hikes you’ve ever attempted, it’s
important to have a good sense of what you’ll face on a new and unfamiliar hike
and whether it’s within your abilities.

Tet19 047 Me on Teton Crest Trail copy cropped 17 jpg
Hi, I’m Michael Lanza, creator of The Big Outside. Click here to sign up for my FREE email newsletter. Join The Big Outside to get full access to all of my blog’s stories. Click here for my e-books to classic backpacking trips. Click here to learn how I can help you plan your next trip.

A backpacker hiking the Dawson Pass Trail in Glacier National Park.
” data-image-caption=”Pam Solon backpacking the Dawson Pass Trail in Glacier National Park. Click photo to read about backpacking in Glacier.
” data-medium-file=”″ data-large-file=”″ src=”×683.jpg?resize=900%2C600&ssl=1″ alt=”A backpacker hiking the Dawson Pass Trail in Glacier National Park.” class=”wp-image-61235″ srcset=” 1024w, 300w, 768w, 150w, 1200w” sizes=”(max-width: 900px) 100vw, 900px” data-recalc-dims=”1″ />Pam Solon backpacking the Dawson Pass Trail in Glacier National Park. Click photo to read about backpacking in Glacier.

Exceeding your limits or those of someone with you can
invite unwanted consequences—and the person with the least stamina,
abilities, or experience often dictates any party’s pace, limits, and outcomes.
Those consequences
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The 12 Best Down Jackets of 2024

Tet19 047 Me on Teton Crest Trail copy cropped 14 jpg

By Michael Lanza

Whatever you need an insulated jacket for, there’s a down or synthetic puffy for your needs, within your budget. And whether you want a puffy jacket for outdoor activities like backpacking, camping, skiing, climbing, and hut treks, or just to keep you warm around town or at outdoor sporting events, this review will help you figure out how to choose the right jacket for your purposes, and it spotlights the best down and synthetic insulated jackets available today.

I selected the jackets covered in this review after extensive testing on backpacking, camping, backcountry ski touring, climbing and other backcountry trips. I’ve field-tested dozens of insulated jackets over nearly three decades of testing and reviewing gear, formerly as the lead gear reviewer for Backpacker magazine for 10 years and even longer running this blog.

Technology has blurred the traditional lines between down and synthetics, with water-resistant down that traps heat even when wet—all but eliminating the weakness that had long been the Achilles heel of down—and synthetic insulation materials that approach the warmth-to-weight ratio and compressibility of down.

If you’d prefer, scroll past my buying tips to dive immediately into the jacket reviews.

If you have a question for me or a comment on this review, please leave it in the comments section at the bottom of this story. I try to respond to all comments.

Tet19 047 Me on Teton Crest Trail copy cropped 15 jpg
Hi, I’m Michael Lanza, creator of The Big Outside. Click here to sign up for my FREE email newsletter. Join The Big Outside to get full access to all of my blog’s stories. Click here for my e-guides to classic backpacking trips. Click here to learn how I can help you plan your next trip.

The Black Diamond Approach Down Hoody.
” data-image-caption=”The Black Diamond Approach Down Hoody in the Grand Canyon.
” data-medium-file=”″ data-large-file=”″ src=”×683.jpg?resize=900%2C600&ssl=1″ alt=”The Black Diamond Approach Down Hoody.” class=”wp-image-52287″ srcset=” 1024w, 300w, 768w, 150w, 1200w” sizes=”(max-width: 900px) 100vw, 900px” data-recalc-dims=”1″ />The Black Diamond Approach Down Hoody in the Grand Canyon.

How to Choose a Synthetic or Down Jacket

Insulated jackets today differ not only in type and amount of insulation, but also in water resistance, breathability, and as always, design features like the hood and pockets. When choosing between down and synthetic models, consider the usual conditions and temperatures in which you’ll use it—in other words, how wet and cold you expect to get, and your body type (how easily you get cold)—as well as the seasonal and activity versatility you require. Some questions to
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