Studying our solar system's protective bubble

DECEMBER 3, 2021, by Kat J. McAlpine, Boston University

https://phys.org/news/2021-12-solar.html

Is this what the heliosphere looks like? BU-led research suggests so. The size and shape of the magnetic “force field” that protects our solar system from deadly cosmic rays has long been debated by astrophysicists. 

Credit: Merav Opher, et. al

A multi-institutional team of astrophysicists headquartered at Boston University, led by BU astrophysicist Merav Opher, has made a breakthrough discovery in our understanding of the cosmic forces that shape the protective bubble surrounding our solar system—a bubble that shelters life on Earth and is known by space researchers as the heliosphere.

Astrophysicists believe the heliosphere protects the planets within our solar system from powerful radiation emanating from supernovas, the final explosions of dying stars throughout the universe. They believe the heliosphere extends far beyond our solar system, but despite the massive buffer against cosmic radiation that the heliosphere provides Earth's life-forms, no one really knows the shape of the heliosphere—or, for that matter, the size of it.

"How is this relevant for society? The bubble that surrounds us, produced by the sun, offers protection from galactic cosmic rays, and the shape of it can affect how those rays get into the heliosphere," says James Drake, an astrophysicist at University of Maryland who collaborates with Opher. "There's lots of theories but, of course, the way that galactic cosmic rays can get in can be impacted by the structure of the heliosphere—does it have wrinkles and folds and that sort of thing?"

Opher's team has constructed some of the most compelling computer simulations of the heliosphere, based on models built on observable data and theoretical astrophysics. At BU, in the Center for Space Physics, Opher, a College of Arts & Sciences professor of astronomy, leads a NASA DRIVE (Diversity, Realize, Integrate, Venture, Educate) Science Center that's supported by $1.3 million in NASA funding. That team, made up of experts Opher recruited from 11 other universities and research institutes, develops predictive models of the heliosphere in an effort the team calls SHIELD (Solar-wind with Hydrogen Ion Exchange and Large-scale Dynamics).

Since BU'S NASA DRIVE Science Center first received funding in 2019, Opher's SHIELD team has hunted for answers to several puzzling questions: What is the overall structure of the heliosphere? How do its ionized particles evolve and affect heliospheric processes? How does the heliosphere interact and influence the interstellar medium, the matter and radiation that exists between stars? And how do cosmic rays get filtered by, or transported through, the heliosphere?

"SHIELD combines theory, modeling, and observations to build comprehensive models," Opher says. "All these different components work together to help understand the puzzles of the heliosphere."

And now a paper published by Opher and collaborators in Astrophysical Journal reveals that neutral hydrogen particles streaming from outside our solar system most likely play a crucial role in the way our heliosphere takes shape.

In their latest study, Opher's team wanted to understand why heliospheric jets—blooming columns of energy and matter that are similar to other types of cosmic jets found throughout the universe—become unstable. "Why do stars and black holes—and our own sun—eject unstable jets?" Opher says. "We see these jets projecting as irregular columns, and [astrophysicists] have been wondering for years why these shapes present instabilities."

New research led by BU astrophysicist Merav Opher could explain why the heliosphere, a protective magnetic “force field” emanating from our sun and encompassing our solar system, is likely unstable and irregularly shaped. “The universe is not quiet,” Opher says. “Our BU model doesn’t try to cut out the chaos.” 

Credit: Merav Opher, et. al

Similarly, SHIELD models predict that the heliosphere, traveling in tandem with our sun and encompassing our solar system, doesn't appear to be stable. Other models of the heliosphere developed by other astrophysicists tend to depict the heliosphere as having a comet-like shape, with a jet—or a "tail"—streaming behind in its wake. In contrast, Opher's model suggests the heliosphere is shaped more like a croissant or even a donut.

The reason for that? Neutral hydrogen particles, so-called because they have equal amounts of positive and negative charge that net no charge at all.

"They come streaming through the solar system," Opher says. Using a computational model like a recipe to test the effect of 'neutrals' on the shape of the heliosphere, she "took one ingredient out of the cake—the neutrals—and noticed that the jets coming from the sun, shaping the heliosphere, become super stable. When I put them back in, things start bending, the center axis starts wiggling, and that means that something inside the heliospheric jets is becoming very unstable."

Instability like that would theoretically cause disturbance in the solar winds and jets emanating from our sun, causing the heliosphere to split its shape—into a croissant-like form. Although astrophysicists haven't yet developed ways to observe the actual shape of the heliosphere, Opher's model suggests the presence of neutrals slamming into our solar system would make it impossible for the heliosphere to flow uniformly like a shooting comet. And one thing is for sure—neutrals are definitely pelting their way through space.

Drake, a coauthor on the new study, says Opher's model "offers the first clear explanation for why the shape of the heliosphere breaks up in the northern and southern areas, which could impact our understanding of how galactic cosmic rays come into Earth and the near-Earth environment." That could affect the threat that radiation poses to life on Earth and also for astronauts in space or future pioneers attempting to travel to Mars or other planets.

"The universe is not quiet," Opher says. "Our BU model doesn't try to cut out the chaos, which has allowed me to pinpoint the cause [of the heliosphere's instability]…. The neutral hydrogen particles."

Specifically, the presence of the neutrals colliding with the heliosphere triggers a phenomenon well known by physicists, called the Rayleigh-Taylor instability, which occurs when two materials of different densities collide, with the lighter material pushing against the heavier material. It's what happens when oil is suspended above water, and when heavier fluids or materials are suspended above lighter fluids. Gravity plays a role and gives rise to some wildly irregular shapes. In the case of the cosmic jets, the drag between the neutral hydrogen particles and charged ions creates a similar effect as gravity. The "fingers" seen in the famous Horsehead Nebula, for example, are caused by the Rayleigh-Taylor instability.

"This finding is a really major breakthrough, it's really set us in a direction of discovering why our model gets its distinct croissant-shaped heliosphere and why other models don't," Opher says.

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The first habitable-zone, Earth-sized planet discovered with exoplanet survey spacecraft

OCTOBER 26, 2020, by Harvard-Smithsonian Center for Astrophysics

https://phys.org/news/2020-10-habitable-zone-earth-sized-planet-exoplanet-survey.html

A schematic of the planets around the nearby M dwarf star TOI-700, discovered by TESS. The third (the farthest planet from the star), TOI-700d, lies within the star's habitable zone (shown in green). Using the IRAC camera on Spitzer, the team refined the planet's mass as 2.1 Earth-masses and 1.14 Earth-radii. (The scale shows 0.2 astronomical units; AU being the average Earth-Sun distance.) 

Credit: Rodriguez et al 2020

TESS, the Transiting Exoplanet Survey Satellite, was launched in 2018 with the goal of discovering small planets around the Sun's nearest neighbors, stars bright enough to allow for follow-up characterizations of their planets' masses and atmospheres. TESS has so far discovered seventeen small planets around eleven nearby stars that are M dwarfs—stars that are smaller than the Sun (less than about 60% of the Sun's mass) and cooler (surface temperatures less than about 3900 kelvin). In a series of three papers that appeared together this month, astronomers report that one of these planets, TOI-700d, is Earth-sized and also located in its star's habitable zone; they also discuss its possible climate.

Center for Astrophysics astronomers Joseph Rodriguez, Laura Kreidberg, Karen Collins, Samuel Quinn, Dave Latham, Ryan Cloutier, Jennifer Winters, Jason Eastman, and David Charbonneau were on the teams that studied TOI-700d, one of three small planets orbiting one M dwarf star (its mass is 0.415 solar masses) located one hundred and two light-years from Earth. The TESS data analysis found the tentative sizes of the planets as being approximately Earth-sized, 1.04, 2.65 and 1.14 Earth-radii, respectively, and their orbital periods as 9.98, 16.05, and 37.42 days, respectively. In our solar system, Mercury orbits the Sun in about 88 days; it is so close to the Sun that its temperature can reach over 400 Celsius. But because this M-dwarf star is comparatively cool the orbit of its third planet, even though much closer to the star than Mercury is to the Sun, places it in the habitable zone – the region within which the temperatures allow surface water (if any) to remain liquid when there is also an atmosphere. That makes this Earth-sized planet TOI-700d particularly interesting as a potential host for life.

The TESS detections were exciting but uncertain: the signals were faint and a small possibility remained that the TOI-700d detection was spurious. Because of the potential importance of finding a nearby Earth-sized planet in a habitable zone, the TESS scientists turned to the IRAC camera on the Spitzer Space Observatory for confirmation. Before being turned off by NASA in February 2020, the IRAC camera was by far the most sensitive near infrared camera in space. The TESS team observed TOI-700 with IRAC in October of 2019 and January of 2020, acquiring clear detections of the planets with about twice the signal-to-noise of TESS, enough to give a 61% improvement in the planet's orbit and to significantly refine our knowledge of its other characteristics, refining the radius as above and finding the mass to be 2.1 Earth-masses. The results, especially when compared with other planets' properties, suggest that this planet may be rocky and likely to be "tidally locked" with one side of the planet always facing the star.

If there were liquid water on the surface of TOI-700d, the astronomers argue, there would also be water-bearing clouds in the atmosphere, and the team uses climate system models to estimate its possible properties and what more sensitive measurements might find. They conclude, however, that pending space missions, including JWST, will probably lack the sensitivity to detect atmospheric features by a factor of ten or more. Their detailed climate studies will nevertheless help astronomers constrain the kinds of telescopes and instruments that will be needed to investigate this exciting new neighbor.

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Soon, 1 out of every 15 points of light in the sky will be a satellite

DECEMBER 1, 2021, by Samantha Lawler, The Conversation
https://phys.org/news/2021-12-sky-satellite.html

Starlink satellites are quite visible in the night sky. 

Credit: Shutterstock

I'm outside at my rural Saskatchewan farm, chatting with my neighbors who I've invited over to appreciate the night sky through my telescope. After exclamations and open-mouthed wonder over Saturn's rings, and light that has been traveling through space for more than two million years to reach our eyes from the Andromeda Galaxy, our conversation inevitably turns to the pandemic, our work-from-home arrangements and complaints about rural internet. My neighbor casually mentions they've just switched to using Starlink for their internet provider.

I glance up and notice a bright satellite moving across the sky, almost certainly a Starlink, since they now make up almost half of the nearly 4,000 operational satellites and they're extremely bright. I take a deep breath and carefully consider how to discuss the substantial cost that we're all going to have to pay for Starlink internet.

I don't blame my neighbors for switching. Here, as in many rural parts of North America, there aren't great internet options, and with many people working and taking classes from home during the pandemic, anything that makes life easier is immediately accepted.

But I know exactly how high this cost could be. My paper, forthcoming in The Astronomical Journal, has predictions for what the night sky will look like if satellite companies follow through on their current plans. I also know that because of the geometry of sunlight and the orbits that have been chosen, 50 degrees north, where I live, will be the most severely affected part of the world.

With no regulation, I know that in the near future, one out of every 15 points you can see in the sky will actually be relentlessly crawling satellites, not stars. This will be devastating to research astronomy, and will completely change the night sky worldwide.

The future is too, too bright

In order to find out how badly the night sky is going to be affected by sunlight reflected from planned satellite megaconstellations, we built an open-source computer model to predict satellite brightnesses as seen from different places on Earth, at different times of night, in different seasons. We also built a simple web app based on this simulation.

Our model uses 65,000 satellites on the orbits filed by four megaconstellation companies: SpaceX Starlink and Amazon Kuiper (United States), OneWeb (United Kingdom) and StarNet/GW (China). We calibrated our simulation to match telescope measurements of Starlink satellites, since they are by far the most numerous.

Starlink has so far made some strides toward dimming their satellites since their first launch, but most are still visible to the naked eye.

Our simulations show that from everywhere in the world, in every season, there will be dozens to hundreds of satellites visible for at least an hour before sunrise and after sunset. Right now, it's relatively easy to escape urban light pollution for dark skies while camping or visiting your cabin, but our simulations show that you can't escape this new satellite light pollution anywhere on Earth, even at the North Pole.

The most severely affected locations on Earth will be 50 degrees north and south, near cities like London, Amsterdam, Berlin, Prague, Kiev, Vancouver, Calgary and my own home. On the summer solstice, from these latitudes, there will be close to 200 satellites visible to the naked eye all night long.

I study orbital dynamics of the Kuiper Belt, a belt of small bodies beyond Neptune. My research relies on long time-exposure, wide-field imaging to discover and track these small bodies to learn about the history of our Solar System.

The telescope observations that are key to learning about our universe are about to get much, much harder because of unregulated development of space.

Astronomers are creating some mitigation strategies, but they will require time and effort that should be paid for by megaconstellation companies.

Unknown environmental costs

Starlink internet might appear cheaper than other rural options, but this is because many costs are offloaded. One immediate cost is atmospheric pollution from the hundreds of rocket launches required to build and maintain this system.

Every satellite deployment dumps spent rocket bodies and other debris into already-crowded low Earth orbit, increasing collision risks. Some of this space junk will eventually fall back to Earth, and those parts of the globe with the highest overhead satellite densities will also be the most likely to be literally impacted.

Starlink plans to replace each of the 42,000 satellites after five years of operation, which will require de-orbiting an average 25 satellites per day, about six tons of material. The mass of these satellites won't go away—it will be deposited in the upper atmosphere. Because satellites comprise mostly aluminum alloys, they may form alumina particles as they vaporize in the upper atmosphere, potentially destroying ozone and causing global temperature changes.

This has not yet been studied in-depth because low Earth orbit is not currently subject to any environmental regulations.

Regulating the sky

Currently, low Earth orbit, where all of these satellites are planned to operate, is almost completely unregulated. There are no rules about light pollution, atmospheric pollution from launches, atmospheric pollution from re-entry, or collisions between satellites.

These megaconstellations might not even be financially viable over the long term, and internet speeds may slow to a crawl when many users connect at the same time or when it rains.

But companies are launching satellites right now at a frenetic pace, and the damage they do to the night sky, the atmosphere and the safety of low Earth orbit will not be undone even if the operators go bankrupt.

There's no doubt that rural and remote internet users in many places have been left behind by internet infrastructure development. But there are many other options for internet delivery that will not result in such extreme costs.

We can't accept the global loss of access to the night sky, which we've been able to see and connect with for as long as we've been human.

With co-operation instead of competition between satellite companies, we could have many fewer in orbit. By changing the design of satellites, they could be made much fainter, having less of an impact on the night sky. We shouldn't have to make a choice between astronomy and the internet.

But without regulations requiring these changes, or strong pressure from consumers indicating the importance of the night sky, our view of the stars will soon be changed forever.

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Space Exploration News: A whole new world: TOLIMAN to scan for habitable exoplanets in Alpha Centauri

 

A whole new world: TOLIMAN to scan for habitable exoplanets in Alpha Centauri

The TOLIMAN project will see a new space telescope launched in order to closely examine the Alpha Centauri system.

By AARON REICH, Jerusalem Post,  DECEMBER 2, 2021

https://www.jpost.com/science/a-whole-new-world-toliman-to-scan-for-habitable-exoplanets-in-alpha-centauri-687616

A view of the surface of the planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to our Solar System, is seen in an undated artist's impression released by the European Southern Observatory August 24, 2016. (photo credit: ESO/M. KORNMESSER/HANDOUT VIA REUTERS)

An exciting new project will see scientists take a closer look than ever before at Earth’s nearest interstellar neighbor to find new worlds, some of which could be able to host life.

Dubbed TOLIMAN, the project is the work of Breakthrough Watch, a project of the Breakthrough Initiatives program founded by Russian-Israeli billionaire Yuri Milner, along with the Australian company Saber Astronautics and NASA’s Jet Propulsion Laboratory. The project will see a new space telescope launched in order to closely examine the Alpha Centauri system. The mission’s name is an acronym for Telescope for Orbit Locus Interferometric Monitoring of our Astronomical Neighborhood but is also derived from the old Arabic name for Alpha Centauri.

The system in question is the closest star system to our own, located just over four light-years away. However, there are some very notable differences. Unlike our own solar system, which just has one star, Alpha Centauri has three, making it a triple star system. Two of these stars – Alpha Centauri A (Rigil Kentaurus) and Alpha Centauri B (Toliman) – are the same type of star as our sun. The third star, Alpha Centauri C (Proxima Centauri), which is the closest of the three to Earth, is a smaller, red dwarf star that is harder to notice.

But what is especially interesting about this star system is the presence of exoplanets, a term that refers to any planet discovered outside of the solar system. While scientists have long theorized that exoplanets exist, only a relative handful – around 5,000 – have definitively been identified throughout the infinite reaches of the cosmos. This is because it can be very difficult to truly spot them, especially since the brightness of stars tends to vastly overwhelm the brightness reflected off these worlds.

But scientists are confident that some planets exist in the Alpha Centauri system. One planet, believed to be a giant planet comparable in size to Neptune, is thought to be orbiting Rigil Kentaurus. It is likely a gas giant, though because it inhabits the habitable zone, its moons could potentially be able to support life, something Breakthrough Initiatives executive director Pete Worden compared to the planet in the 2009 James Cameron film Avatar.

The planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to our Solar System, is seen in an undated artist's impression. (credit: REUTERS)

But it is Proxima Centauri that is the most interesting.

While the existence of the giant planet is still unconfirmed, two exoplanets are confirmed to be orbiting Proxima Centauri. Proxima b and Proxima c. Of the two, the former is close in size to Earth and is in the habitable zone. And as an Earth-sized world in the habitable zone of a red dwarf star, some have drawn comparisons to Superman’s fictional homeworld of Krypton.

Though Proxima b is in the habitable zone, and scientists believe it is a rocky world, there is still so much unknown about it.

But why are we only now looking at our closest interstellar neighbors, whereas other missions have focused on more distant stars?

Part of this has to do with the brightness, which can make observation difficult. As a result, the new TOLIMAN space telescope uses measurements to find the exact position of these stellar bodies and, in turn, deduce their mass, a field of study known as astrometry.

When a planet orbits a star, its own gravity will tug on it ever so slightly, causing the star to “wobble,” Worden explained. This can help scientists detect the mass and distance of an exoplanet from the star.

“We can’t detect the composition of an exoplanet, but if we determine the mass - like five times of Earth - and we can measure the brightness - and we have a marginal measure for the giant planet - then we can make assumptions about the reflectivity,” he said. “From that, we can deduce the radius and then that way, you can get a mean density. So if it’s a rocky world or water world, you can figure it out.”

New Toliman SpaceTelescope Will Hunt for Alien Life In Alpha Centauri Star System 

But it is unclear if Proxima b can support life.

“Proxima Centauri is a flare star,” Worden explained. “Every few days, it has an explosion, it might brighten 100 times. It was thought that these would have blown the atmosphere of a planet away.”

But we don’t know for sure, and it is still worth looking at our closest neighbor in space.

The mission is tentatively slated to be launched in two years and will spend four to six years observing Alpha Centauri, and information gleaned from this observation as well as through future advancements in telescopes could eventually lead to atmospheric analyses, such as if the planet could support life.

Further, this could also determine if the planet was an ideal candidate for another Breakthrough Initiatives program: Breakthrough Starshot - a mission that would see specially designed spacecrafts head to Alpha Centauri and send a message back.

Though this journey would take over 20 years and would require traveling around 20% the speed of light, the research into this program seems promising so far.

But as for Worden and Breakthrough Watch, they are already looking into the future.

“There’s another star system further away called 61 Cygni,” he explained. “This is a binary star system, it has two stars similar to the Sun that might be able to support life. We want to look there and see what we can find.”

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Defense News: With T-7 on the way, why is ACC eyeing a new trainer?

With T-7 on the way, why is ACC eyeing a new trainer?

 By Stephen Losey, Defense News,  December 1, 2021

https://www.defensenews.com/air/2021/12/01/with-t-7-on-the-way-why-is-acc-eyeing-a-new-trainer/

While the Air Force has a new trainer designed to teach new pilots how to fly in 5th generation fighter aircraft, the T-7A Red Hawk, Air Combat Command has started exploring the possibility of another Advanced Tactical Trainer. (Boeing)

WASHINGTON — The Air Force is considering a new trainer aircraft — one intended to emulate 4th and 5th generation fighter jets and be able to better train the service’s newest fighter pilots how to fly in combat.

Nope, not the T-7A Red Hawk. Another one. Maybe.

The Air Force released a request for information for a new trainer aircraft, dubbed the Advanced Tactical Trainer, on Oct. 12. But given the service has the first T-7s on the way, scheduled to arrive at Joint Base San Antonio-Randolph in Texas in 2023, the service’s apparent interest in another — similar — trainer left some observers scratching their heads.

Dan Grazier of the watchdog group Project on Government Oversight said the Air Force’s consideration of another trainer aircraft raises questions about its strategy and priorities — and perhaps about the T-7.

“This does seem like a really curious move,” Grazier said in a Nov. 29 interview. “There’s a couple of things that this move communicates that I think the Air Force didn’t really mean to communicate.”

In 2018, the Air Force awarded a $9.2 billion contract to Boeing to build 351 of the Air Force’s next trainer, unveiled as the T-7A Red Hawk the following year. Its use of digital engineering, open architecture, and other innovative design techniques excited many service leaders, and was seen as a new model for rapid, efficient aircraft development.

In a statement, Boeing said it’s interested in exploring what ACC wants to see in an advanced trainer and stressed the capability of the T-7 to evolve and meet the command’s needs.

“From its digital beginnings, the T-7 was designed for growth,” Boeing said. “This exciting opportunity is being explored to see how the T-7′s growth path for future missions align with Air Combat Command’s ATT initiative.”

The T-7 is intended to replace the T-38 jet trainer, which dates back to the 1960s and has been at the center of several fatal crashes in recent years — the most recent on Nov. 19. The Air Force’s newest 5th generation fighters, the F-22 and F-35, are also far beyond the T-38′s capabilities.

“Every day, that [T-38] airplane becomes just another step more disconnected from the advanced avionics, advanced sensing, the advanced processing that our modern fighters have, and so we can’t fill that void fast enough,” Air Combat Command head Gen. Mark Kelly said in an Oct. 25 event with the Mitchell Institute.

Kelly said the T-7 is already slated to go to Air Education and Training Command to teach the service’s youngest aviators how to fly.

“But I need to get our [ACC] aviators, as soon as I can, something that is not such a leap from a 1964 T-38 to a 2021 F-35,” Kelly said.

Kelly acknowledged the T-7 may be able to do everything ACC needs it to do, and the answer could be buying more of them. But he also said industry may be able to offer some new ideas that could either be added to the T-7, or lead to a completely new air frame.

He added that ACC needs additional features in the aircraft it uses to conduct fighter pilot training — features the T-7 was never required to have.

Kelly said those features could include increased use of sensors, and increased fuel requirements for mission duration and afterburner use. And he expects it could have some rudimentary weapons computing capability and some simulation playback capabilities to teach pilots how to respond to threats.

“All of those drive requirements that weren’t in the original T-7 statement of requirements,” Kelly said. “And so it’s not a criticism of the T-7 — they built what they were designed to build. But it may or may not fit the demand of going from flying to fighting, because they’re a different avenue. They just happen to take place in the same space.”

Air Combat Command declined an interview request from Defense News, but said in written responses to questions that this proposed trainer’s requirements would differ from the T-7 and help ACC “most effectively and efficiently train fighter pilots.”

“The goal of the ATT is to provide pilots with training that emulates the aircraft (systems, displays, etc) they will eventually be flying at their operational unit, thus reducing the amount of training hours spent on operational fighter aircraft,” ACC said in a Nov. 23 email.

Flying the ATT would allow pilots to acquire “transferable learned skills” that would save combat fighters time they need for mission training and preparation, ACC said.

Two Boeing-Saab T-X jets fly above St. Louis, Mo. (John Parker/Saab)

Want vs. need

The Air Force first posted a request for information Oct. 12 for an Advanced Tactical Trainer that would primarily be used for Air Combat Command’s Initial Tactical Training program. The RFI said it would also be used to provide adversary air support, or playing the enemy during combat training exercises, and lastly as a tactical surrogate for existing or future fighters.

A Q&A document posted online Nov. 9, drawn from one-on-one exchanges with industry representatives, further detailed some of ACC’s hopes for this trainer. It would have to carry munitions for training purposes only, but not to release them. And it would have to emulate 4th and 5th generation fighters and their performance capabilities, possibly with transonic acceleration.

ACC said in the Q&A it hopes that using the proposed trainer instead of actual fighter aircraft would shave 12 to 18 months off the timeline required to fully train a pilot.

But in a time when future budgets are expected to be tight and Air Force officials regularly speak about the need to make tough budgeting choices and possibly divest aircraft, Grazier said the service’s apparent interest in another trainer doesn’t fit.

“This almost sounds like a ‘want-to-have,’ [rather] than a ‘need-to-have,’” Grazier said.

Todd Harrison, director of the Aerospace Security Project at the Center for Strategic and International Studies, said the RFI “does make you scratch your head and wonder, how can the Air Force afford another new-start aircraft program when their acquisition pipeline is already quite full?”

Boeing T-7A Red Hawk Flight Tests, 

Jun 25, 2021

Weighing T-7 upgrades

Harrison cautioned that the Air Force’s request for information on another trainer doesn’t necessarily mean it’s going to launch a whole additional program.

Instead, he said, the suggestions the Air Force collects could give it some ideas for improving the Boeing-built T-7A, allowing ACC to fly the F-35 less.

“This is definitely going to ramp up the pressure on Boeing to adapt the T-7 so that it can meet these types of requirements,” Harrison said. “The last thing Boeing wants to see is another training aircraft program being started that would compete for budget [dollars] with what they’ve already won.”

The T-7, which was designed to be easily adapted and upgradeable, should be able to do that, Harrison said. And if it means the Air Force could buy even more of their planes, he said, Boeing has a clear incentive to modify them to meet the ATT requirements.

But if the T-7 can’t do what ACC needs, Grazier said, it raises questions as to whether the Air Force should hit the brakes on the program before it goes any further.

“Does this mean that the requirements, and the design for the T-7A aren’t what we need?” Grazier said. “And if that’s the case, then should we still be pressing forward with a T-7A?”

John Venable, a former fighter pilot who now is a defense policy expert at the Heritage Foundation, said the apparent consideration of another trainer aircraft “makes little sense” — and could be a sign the Air Force left some gaps in the capabilities it requested when it asked industry to build a trainer jet that became the T-7.

“If Boeing is actually meeting the specifications that were called for in the RFI [for the T-7], they should be able to take that air frame and modify it,” Venable said.

It makes sense the Air Force would want to have an aircraft for fighter pilots to train in that doesn’t require time in an actual fighter jet — particularly the F-35, which has turned out to be more expensive to fly than expected, Harrison said.

“I could see where they’re coming from in terms of trying to … save wear and tear on the [fighter] platform,” Harrison said.

ACC would also benefit from having a dual-seat trainer like the ATT, so newer pilots could have an experienced pilot in the unit right behind them offering guidance, Harrison said. The 5th-generation F-22 and F-35 fighters are single-seat aircraft.

And, Kelly said, ACC needs a trainer that can fly at a much lower cost than aircraft like the F-35, which costs between $34,000 and $36,000 to fly for one hour.

“I need something … that’s not $20,000-plus cost per flying hour, closer to $2,000 to $3,000 cost per flying hour, that comes a little closer to our modern avionics,” Kelly said.

But this issue underscores broader issues with the sustainability of the Air Force’s current fighter fleet, Grazier said.

“Pursuing another training aircraft is a real indictment on the current fleet of fighter aircraft,” Grazier said. “Between the F-22 and F-35, this is further evidence that those programs really are unaffordable if we have to have an entirely new trainer aircraft to pick up the fleet.”

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Researchers shrink camera to the size of a salt grain

NOVEMBER 29, 2021, by Molly Sharlach, Princeton University

https://phys.org/news/2021-11-camera-size-salt-grain.html

Researchers at Princeton University and the University of Washington have developed an ultracompact camera the size of a coarse grain of salt. The system relies on a technology called a metasurface, which is studded with 1.6 million cylindrical posts and can be produced much like a computer chip.

 Credit: Princeton University

Micro-sized cameras have great potential to spot problems in the human body and enable sensing for super-small robots, but past approaches captured fuzzy, distorted images with limited fields of view.

Now, researchers at Princeton University and the University of Washington have overcome these obstacles with an ultracompact camera the size of a coarse grain of salt. The new system can produce crisp, full-color images on par with a conventional compound camera lens 500,000 times larger in volume, the researchers reported in a paper published Nov. 29 in Nature Communications.

Enabled by a joint design of the camera's hardware and computational processing, the system could enable minimally invasive endoscopy with medical robots to diagnose and treat diseases, and improve imaging for other robots with size and weight constraints. Arrays of thousands of such cameras could be used for full-scene sensing, turning surfaces into cameras.

While a traditional camera uses a series of curved glass or plastic lenses to bend light rays into focus, the new optical system relies on a technology called a metasurface, which can be produced much like a computer chip. Just half a millimeter wide, the metasurface is studded with 1.6 million cylindrical posts, each roughly the size of the human immunodeficiency virus (HIV).

Each post has a unique geometry, and functions like an optical antenna. Varying the design of each post is necessary to correctly shape the entire optical wavefront. With the help of machine learning-based algorithms, the posts' interactions with light combine to produce the highest-quality images and widest field of view for a full-color metasurface camera developed to date.

A key innovation in the camera's creation was the integrated design of the optical surface and the signal processing algorithms that produce the image. This boosted the camera's performance in natural light conditions, in contrast to previous metasurface cameras that required the pure laser light of a laboratory or other ideal conditions to produce high-quality images, said Felix Heide, the study's senior author and an assistant professor of computer science at Princeton.

The researchers compared images produced with their system to the results of previous metasurface cameras, as well as images captured by a conventional compound optic that uses a series of six refractive lenses. Aside from a bit of blurring at the edges of the frame, the nano-sized camera's images were comparable to those of the traditional lens setup, which is more than 500,000 times larger in volume.

Other ultracompact metasurface lenses have suffered from major image distortions, small fields of view, and limited ability to capture the full spectrum of visible light—referred to as RGB imaging because it combines red, green and blue to produce different hues.

"It's been a challenge to design and configure these little microstructures to do what you want," said Ethan Tseng, a computer science Ph.D. student at Princeton who co-led the study. "For this specific task of capturing large field of view RGB images, it's challenging because there are millions of these little microstructures, and it's not clear how to design them in an optimal way."

Previous micro-sized cameras (left) captured fuzzy, distorted images with limited fields of view. A new system called neural nano-optics (right) can produce crisp, full-color images on par with a conventional compound camera lens.

 Credit: Princeton University

Co-lead author Shane Colburn tackled this challenge by creating a computational simulator to automate testing of different nano-antenna configurations. Because of the number of antennas and the complexity of their interactions with light, this type of simulation can use "massive amounts of memory and time," said Colburn. He developed a model to efficiently approximate the metasurfaces' image production capabilities with sufficient accuracy.

Colburn, who conducted the work as a Ph.D. student at the University of Washington Department of Electrical & Computer Engineering (UW ECE), where he is now an affiliate assistant professor. He also directs system design at Tunoptix, a Seattle-based company that is commercializing metasurface imaging technologies. Tunoptix was cofounded by Colburn's graduate adviser Arka Majumdar, an associate professor at the University of Washington in the ECE and physics departments and a coauthor of the study.

Coauthor James Whitehead, a Ph.D. student at UW ECE, fabricated the metasurfaces, which are based on silicon nitride, a glass-like material that is compatible with standard semiconductor manufacturing methods used for computer chips—meaning that a given metasurface design could be easily mass-produced at lower cost than the lenses in conventional cameras.

"Although the approach to optical design is not new, this is the first system that uses a surface optical technology in the front end and neural-based processing in the back," said Joseph Mait, a consultant at Mait-Optik and a former senior researcher and chief scientist at the U.S. Army Research Laboratory.

"The significance of the published work is completing the Herculean task to jointly design the size, shape and location of the metasurface's million features and the parameters of the post-detection processing to achieve the desired imaging performance," added Mait, who was not involved in the study.

Heide and his colleagues are now working to add more computational abilities to the camera itself. Beyond optimizing image quality, they would like to add capabilities for object detection and other sensing modalities relevant for medicine and robotics.

Heide also envisions using ultracompact imagers to create "surfaces as sensors." "We could turn individual surfaces into cameras that have ultra-high resolution, so you wouldn't need three cameras on the back of your phone anymore, but the whole back of your phone would become one giant camera. We can think of completely different ways to build devices in the future," he said.

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