Sunnyvale, California-based Amprius kept a low profile for several years, despite its founder, Yi Cui, being a leading light in battery development.  Their December 4th press release, though, finds the company to be in a more open mood, their advanced lithium-ion cells with 100-percent silicon anodes having flown Airbus’ Zephyr High Altitude Pseudo Satellite (HAPS) for over 25 days, “setting a new endurance and altitude record for stratospheric flight.”

This milestone represents a great leap forward since Alan Cocconi flew his So Long solar-powered model for 48 hours, the first of many projects of which he would be an integral part, and the first solar airplane to fly overnight.  He worked on the General Motors EV1 and Eric Raymond’s Sunseeker 1 – just a small part of the automobiles and aircraft which he would help create or refine.

Amprius performance with silicon nanowire anode compared to that of battery with graphite anode

Your editor first saw Cui at an early electric aircraft symposium nine years ago.  Cui discussed the benefits of developing silicon anodes in batteries, with a potential 10X increase in energy density.  Pitfalls surrounding that hoped-for outcome were plentiful, including the granulation and crumbling of silicon after repeated charge-recharge cycles.  Cui and his graduate students at Stanford University worked to counter this problem, fielding several solutions.  At some point, Cui and his colleagues apparently found an answer.

Roll-to-Roll processing machine combines silicon nanowires with chemical vapor deposition

Their breakthroughs are reinforced by the installation of a “revolutionary” roll-to-roll manufacturing tool which enables high-speed forming of three-dimensional silicon anodes. The tool, created in partnership with Meyer Burger (Netherlands) B.V., uses a multi-step, Chemical Vapor Deposition (CVD) process.

In a 2008 Nature Nanotechnology paper, Stanford Professor Yi Cui and team unveiled a nanowire design that enables using ultra-high-capacity silicon in a lithium-ion battery in place of today’s carbon. The thin nanowire “hairs” allow the silicon to swell and shrink as it takes in lithium without fracturing. (Figure from Chan et al., 2008.)

Steven Chu, a Nobel Laureate and Amprius Board Member, explains this “very big step forward” enables Amprius to go beyond laboratory and pilot-scale manufacturing to “a significant advance towards high-volume and high-quality manufacturing.”

Silicon Valley venture capitalists provide funding, and Airbus has provided a huge platform on which to demonstrate Amprius’ capabilities.

The Zephyr Platform

The Zephyr platform is similar to other HAPS (High Altitude Pseudo Satellite) aircraft that almost hovers at stratospheric heights for indefinite periods.  Airbus points out that Zephyrs can be “used in a wide range of emerging applications, including maritime surveillance and services, border patrol missions, communications, forest fire detection and navigation.”

Sophie Thomas, Airbus’ HAPS Program Director, explains, “Our collaboration with Amprius in the application of their silicon nanowire based lithium ion cells to the Zephyr has been important to the success of the HAPS program.  The high specific energy of Amprius batteries enable the Zephyr to fly uninterrupted in the stratosphere which would not be possible with lower performance batteries. This will further extend the capability and utility of the Zephyr platform for our customers.”

Airbus is putting Zephyrs into series production, a plant at Farnborough,England  capable of turning out 30 of these persistent vehicles each year.  With the first to fly already having achieved 1,000 hours of flight time, those flight hours should grow with growing numbers of craft in service.  Just think of all the ground crews sending this largest of hand-launched aircraft skyward!

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Ironing Out Cheap Molecules for Solar Panels

Making a Designer Iron Molecule

To make more affordable solar cells, researchers at Sweden’s Lund University are not just trying to be cheap, they are avoiding tightening markets in expensive noble metals like ruthenium, osmium and iridium. A more common metal such as iron, constituting six percent of the earth’s crust, might just be the answer to several issues. One problem keeps it from being a great solar cell component. Iron just doesn’t take a shine to solar radiation.

Enhanced iron molecule with light-absorbing, luminescent properties

In the careful words of the abstract for the research team’s paper, iron’s shortcoming is exposed. “However, the photoexcitable charge-transfer (CT) states of most Fe complexes are limited by picosecond or sub-picosecond deactivation through low-lying metal centered (MC) states, resulting in inefficient electron transfer reactivity and complete lack of photoluminescence.” In other words, ordinary iron is just a flash in the pan when light strikes it and doesn’t kick any electrons around – not great behavior for solar cells.

Chemistry Professor Kenneth Wärnmark worked with colleagues to create molecules that could absorb photons from solar radiation and produce electrons. He explains, “Our results now show that by using advanced molecule design, it is possible to replace the rare metals with iron, which is common in the Earth’s crust and therefore cheap.” “Advanced molecule design” means tweaking atoms around the iron core and producing characteristics that make the iron respond like a more “noble” element. the molecule absorbs light and even glows for a time – a very un-iron type of reaction. It is able to hold on to that reaction long enough to cause a reaction with another molecule.

Because of this, the new molecule is not great just for solar cells, but can be an inexpensive catalyst in hydrogen production. Low-cost solar cells and hydrogen would be readily accepted in the marketplace. Or would they?

Solar cost drop over several decades seems to show no sign of slowing down

No Wonder Economics is the Dismal Science

Unfortunately, having a low-cost designer metal That has such outstanding capabilities doesn’t mean we will see an immediate rush to use it. Solar cell prices have been on a steady decline for decades: now – evidenced by the Swanson Effect, the solar industry’s equivalent of Moore’s Law for the computer industry.

As explained in SynchoSolar.com, “‘Swanson’s Law’ is named after Richard Swanson, the founder SunPower, an American solar manufacturer. It is a set of consistent observations around the price of solar panels.

“Swanson Effect” is solar equivalent of Moore’s Law in computers.  Note that price drops since 2013 are in line with previous trends

“Essentially, when the global manufacturing capacity for solar panels doubles, the average price of producing those panels drops by about 20%. Just about every time. This leads to periods of exponential change where the cost of solar can plummet.” And that plummet continues, and will continue with low-cost materials such as Lund’s iron molecule coming into play. But market forces may present at least temporary impediments.

​Bloomberg New Energy Finance (BNEF) has predicted a 34% decline in multicrystalline solar module prices in China, caused by” an abrupt withdrawal of support for the nation’s solar PV market.” This is expected to spread worldwide. Bloomberg notes “Oversupply is universal.”

Oddly, this may stall installations while contractors wait for less expensive panels to become available. This may lead to “enhanced inventory,” with large quantities of multicrytalline wafers already in warehouses in May. Further slowdowns will add to the inventory, and lower costs for materials will lower product pricing, with profit margins already thin. Bloomberg sees a module production cost decline to $0.24 per watt – great news for buyers, but not necessarily for producers.

Bloomberg spells out the multiple variables and the possible scenarios that darken otherwise bright news. In the meantime, solar cell researchers will keep making their devices more efficient and more cost-effective. We may see solar modules as commodities soon, and the producers – desperate for markets – finding applications for transportation to shrink their inventories.

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EMBATT and the FAB Four

No, it’s not the discovery of an unknown Richard Lester film*, but the impending prototype manufacturing collaboration for a battery that promises 450 Watt-hours per liter. Four heavy-hitters in German industry plan on making (fabricating) the flat-panel EMBATT battery into a reality – with all speed.

thyssenkrupp System Engineering GmbH, IAV GmbH, Daimler AG, and Fraunhofer IKTS (Institute for Ceramic Technologies and Systems) have teamed up for the “EMBATT-goes-FAB” project sponsored by the Federal Ministry for Economic Affairs and Energy.

thyssenkrupp specializes in planning, designing and implementing production lines for cylindrical, pouch, and prismatic batteries, and will apply that expertise to the new format. IAV provides engineering and consulting services to auto makers worldwide, and has a depth of knowledge in battery development. Daimler, of course, would have testbeds ready in car or truck size, and would have a vested interest in seeing batteries that can promise 1,000 kilometer (620 mile) range for their vehicles.

Fraunhofer explains the relevant technology in their press release. “In contrast to conventional Li-ion batteries, these electrodes are, as the name indicates, bipolar. This means that the active materials for the battery cathode and, overleaf, the active materials for the anode are applied to a common electrode carrier. The individual Li-ion cells are then no longer packed separately in aluminum housings. Only the finished stack of electrodes is given a fixed housing. This eliminates housing components and connecting elements, which saves costs and space in the vehicle. Instead, the freed-up space can be filled with more active material. As a result, the battery can store more energy and the vehicle can drive further.”

Production of the bipolar electrode on a pilot scale.  Credit: © Fraunhofer IKTS

Dr. Mareike Wolter, Project Manager at Fraunhofer IKTS explains the formulation and application of Fraunhofer’s special coatings. “We use our expertise in ceramic technologies to design the electrodes in such a way that they need as little space as possible, save a lot of energy, are easy to manufacture and have a long life.”

Company scientists mix powdered ceramic materials with polymers and electrically conductive materials to form a suspension. “This formulation has to be specially developed — adapted for the front and back of the tape, respectively,” Wolter explains. The process applies the suspension to the tape in a roll-to-roll process. “One of the core competencies of our institute is to adapt ceramic materials from the laboratory to a pilot scale and to reproduce them reliably,”

EMBATT (short for Embedded Battery) shows it multi-layer approach to condensing energy storage

EMBATTs are bipolar Li-ion batteries, which like fuel cells, consist of stacked electrodes connected in series. In contrast to conventional Li-ion batteries, these electrodes are, as the name indicates, bipolar. This means that the active materials for the battery cathode and, overleaf, the active materials for the anode are applied to a common electrode carrier.

The individual Li-ion cells are then no longer packed separately in aluminum housings. Only the finished stack of electrodes is given a fixed housing. This eliminates housing components and connecting elements, which saves costs and space in the vehicle. Fewer internal connection – thousands in a Bolt or Tesla battery pack, for instance – mean fewer points of potential and lower losses due to resistance.

The FAB four will share development and production duties. Fraunhofer will produce improved bipolar electrodes based on lithium-nickel-manganese-cobalt oxides and graphite as storage materials. thyssenkrupp will scale assembly technology up to a size of 1000 x 30 cm² (393.7 inches by 11.8 inches). IAV will incorporate an electric battery monitoring system, and Daimler will create safety simulations to address specific vehicle requirements.  The EMBATT project seems destined to meet its 2020 deadline for larger-scale production.

*Lester directed the original Fab Four in the films A Hard Day’s Night and Help.

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Volocopters to Fly Doctors

Helena Treeck of Volocopter alerted your editor of an exciting development for the multicopter manufacturer.  ADAC Luftrettung (ADAC Air Rescue) wants to use volocopter’s capabilities to take doctors or other qualified medical personnel to points of need – and rapidly.  ADAC’s slogan, “Against time and for life,” sums their mission, and Volocopters seem apt choices to help fulfill it.

Rotary-wing aircraft have a well-established reputation for rescues in treacherous locales and circumstances.  An outstanding job of flying earlier this year on Mt. Hood, Oregon highlights this.

Electric vertical take off and landing craft may be even better at this than fossil-fuel powered ones.  They don’t run out of oxygen at altitude – the rescue on Mt. Hood took place near the summit at 11,000 feet, adding to the plentiful hazards.

As noted in Helena’s dispatch, “ADAC Luftrettung is the first air rescue organization in the world to test the use of manned multicopters in emergency medical services – both in theory and in practice. The charitable company from Munich has started a feasibility study for the groundbreaking pilot project, supported by the ADAC foundation.”  The object will be to get emergency doctors to patients faster than by existing rapid response vehicles and provide immediate care upon landing.

Tests will take place in two selected model regions in Germany: the emergency service area of Ansbach with the Dinkelsbühl HEMS base in Bavaria, and the State of Rhineland Palatinate.

Tests will start in spring, 2o19, when the Institut für Notfallmedizin und Medizinmanagement (INM, Institute for Emergency Medicine and Medical Management) at Ludwig Maximilian University in Munich will begin computer simulations of rescue mission scenarios.  By the winter and autumn, actual flight test will follow, hoping to show “the potential usability and cost-effectiveness in emergency medical services.”

Florian Reuter, CEO of Volocopter agrees: ““The Volocopter is based on a technical platform permitting its diverse and reliable use as an air taxi, heavy lifting drone, or in rescue missions.  “I firmly believe in the Volocopter’s potential for large-scale use as an air shuttle for emergency doctors, and I look forward to our joint systematic validation with ADAC air rescue.”

Volocopters that may be deployed for emergency medical services will look similar to the one pictured here. ©ADAC/Volocopter

Frédéric Bruder, Managing Director of ADAC air rescue , regards this study as the dawn of a new age in air rescue. “50 years ago, ADAC was among the first in Germany to field test the use of rescue helicopters. Consequently, it is only logical for us to be the first to lead German air rescue into the future with new technologies.”

One wonders how far this experiment can go.  Can an autonomous Volocopter set down, allow the doctor to tend to a patient, and be configured in such a way as to allow a single medic to load the patient on board and return to a medical center?  will hospitals have hubs similar to the air taxi idea promoted by Volocopter?

The ADAC Foundation, a charitable organization, supports the study with 500,000 euros (about $570,000) over the next one- and-a-half years.  Dr Andrea David, Managing Director of the ADAC foundation , explains, “Our goal in supporting this project is to improve emergency medical care, thereby making an important contribution to the future of the EMS system.  Scientific support comes from the German Aerospace Center (DLR), with whom ADAC has cooperated in research and development.

Volocopters operating in their system will be deployed on emergency calls, not entirely different from their urban mobility role in going to passengers on request, but with very different payloads and purposes.

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David Ullman Receives Patent on IDEAL Airplane

David Ullman a Professor Emeritus at Oregon State University, has used his expertise in mechanical engineering to design his IDEAL airplane.  That stands for Integrated Distributed Electric-Augmented Lift, and like all good projects with good acronyms, almost explains itself.  Recently, the U. S Patent office thought the IDEAL is worthy of being patented.

It might be helpful to read the full patent, filed with working partner and neighbor Vincent Homer, because the ideal looks simple, but has years of development behind it.  The two live in Independence, Oregon, on an airport that includes hangars on every house and taxiways linking them to the main runway.  Both their hangars are filled with evidence of their skilled handiwork.  Vincent’s houses giant models and evidence of aeronautical investigations.  David’s shelters a very large wind tunnel, used to help verify his computations about blowing air over the wing and augmenting the lift while providing thrust.  On one wall hangs the twisted wing strut that defines the sad shape of the Jabiru four-seater David rolled into his shop two years ago.  Now rebuilt with David’s abilities for working with composites, the compound curves display a deep knowledge of topology.

Dave Ullman’s wind tunnel in his Independence, Oregon hangar. Bikes on wall were results of design class he taught at OSU

David and Vince presented at every major scholarly aeronautical event in the last year, upholding the idea of a winged Ultra-Short Take Off and Landing (USTOL) aircraft against a cloud of Vertical Take Off and Landing (VTOL) craft.  The eVTOL News™ reports there are over 125 different electric and hybrid VTOL designs, with heavy backing from organizations such as Uber.

IDEAL’s comparison of air-taxi visions uses a “simple analytical model to estimate range based on type of vehicle, battery characteristics and number of passengers.” David and Vince hang out some controversial words based on their findings.

  1. “Electric rotor-craft such as the eHang 184 and the VoloCopter 2X have very limited range even with next-gen batteries.
  2. “VTOL aircraft need to be very large to be effective (UBER is focused on 5000lb machines). Further, the high power needed, as with the rotor-craft, imply inefficiencies that may not be overcome with any foreseeable batteries and sound levels that may be unacceptable.
  3. “USTOL aircraft have high potential. They are perhaps the least developed of the three classes considered but can operate on near future batteries and very small “pocket” airports.
  4. “Clearly the use of batteries for air taxis is problematic. Even next-gen batteries are limiting. Other forms of energy storage need to be explored and developed.
  5. “It is possible to use a fairly simple model to compare and contrast different classes of air vehicles without getting caught up in the details.”

What Jsabiru will look like in first iteration. Later revisions will include high-aspect ratio wing

David and Vince are not hiding their light under a bushel, but rather share their expertise openly.  One benefit of going to David’s web site is the opportunity to request the formulas he and Vince used to derive their ideas.  This “open source” approach will only help to get more researchers on board and to make such experimentation more widespread.

As we can probably surmise, neither the eVTOL nor the USTOL will work in all circumstances.  There are places where the best bushplane can’t safely land, or even worse, take off.  There are limitations to what eVTOLs offer with current batteries regarding range and payload.  Only relentless testing and experience operating all types of these new craft will prove what is possible – and supportable.

In the meantime, check out David Ullman’s site and read the patent and the ideas behind the IDEAL.

For Your Reading Pleasure

David is the author of several books, all worthy of your time.  The Mechanical Design Process, now in its sixth edition, is a basic text in design. “Beyond its title, The Mechanical Design Process is a book for all product designers.  It provides students with a holistic, systematic view of how to discover their customers’ needs and see them through to on-time, cost effective, quality products.”

The Mechanical Design Process: Case Studies shows how the principles in the text have been applied in real-life circumstances.

David collaborated with 24 of his students to produce What Will Your Grandchildren See When They Look Up?  The book provides visions of future aircraft, defined by solid engineering and imaginative leaps.

Living up to his reputation as a decision architect, his book Making Robust Decisons, can guide individuals or groups through the intricacies of making valid decisions that lead to productive outputs.

David’s body of work keeps growing and will soon include his IDEAL airplane.

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This week, a kerfuffle tsunami has swept through the aeronautical press, with the announcement by Steven Barret of the Massachusetts Institute of Technology (MIT) that he has flown an ion-powered airplane that “doesn’t depend on fossil fuels or batteries.”*  (A minor point – the airplane does have a battery that gets its output voltage ramped up by a custom power supply.)

Five years ago, your editor reported on ionic thrusters, several of which were being tested by Barrett, associate professor of aeronautics and astronautics. These little devices have great promise for moving vehicles in space, where the vacuum presents no aerodynamic drag to overcome. Even a small nudge from a thruster in space will cause a vehicle to accelerate. They work fine for low-speed propulsion of small balloons here on earth, or for lightweight lifters as part of science demonstrations, but have been neglected for heavier-than-air craft until now.

Comparing the development level of his ionic airplane to that of the Wright Brothers’ Flyer 115 years ago, Barret says, “This is the first-ever sustained flight of a plane with no moving parts in the propulsion system. This has potentially opened new and unexplored possibilities for aircraft which are quieter, mechanically simpler, and do not emit combustion emissions.”

Unlike the Wrights’ aircraft, and every other one since, Barret’s plane does not rely on propellers or turbines to move it through the air. Instead, it is powered by a flow of ions produced aboard the airplane, which generate enough thrust to propel the plane over a sustained, steady flight.

The craft’s 40,000 Volts supplied across the leading edge wires gives one pause, though. In a 2015 Cycle World Interview, Zero Motorcycle Chief Technical Officer Abe Askenazi said his company limited voltage on its battery packs to 102 Volts for operator safety. Perhaps, for the same safety concerns, many manufacturers are developing 48-Volt mild hybrid drive trains. The battery “stack” in Barret’s ion plane has its voltage electronically transformed to the 40,000 Volts necessary for forward motion.

EAD airplane design. a, Computer-generated rendering of the EAD airplane. b, Photograph of actual EAD airplane after multiple flight trials. c, Architecture of the high-voltage power converter (HVPC). The HVPC consists of three stages: a series–parallel resonant inverter that converts 160–225 V direct current to a high-frequency alternating current; a high-voltage transformer that steps up the alternating-current voltage; and a full-wave Cockcroft–Walton multiplier that rectifies the high-frequency alternating current back to direct current. The three stages contribute a voltage gain of about 2.5×, 15× and 5.6×. Xu et al.

Professor David Perreault of the Power Electronics Research Group in the Research Laboratory of Electronics designed a power supply that increases low-voltage battery power to high-voltage wire power.

The five-pound airplane has a five-meter (16.4-feet) wingspan with an array of thin wires under each wing panel. According to MIT, “The wires act as positively charged electrodes, while similarly arranged thicker wires, running along the back end of the plane’s wing, serve as negative electrodes.”

The team, which included Barret and Lincoln Laboratory staff members Thomas Sebastian and Mark Woolston, made ten flights of 60 meters, limited by the size of MIT’s duPont Athletic Center gymnasium – which accounts for the basketball games in the background of some scenes in the video.

The MIT announcement gives a description of the action that propels Barret’s plane. “Once the wires are energized, they act to attract and strip away negatively charged electrons from the surrounding air molecules, like a giant magnet attracting iron filings. The air molecules that are left behind are newly ionized, and are in turn attracted to the negatively charged electrodes at the back of the plane.

“As the newly formed cloud of ions flows toward the negatively charged wires, each ion collides millions of times with other air molecules, creating a thrust that propels the aircraft forward.”

Barret, inspired by the noiseless shuttlecraft in the background of Star Trek TV episodes and films, found answers finally after “a sleepless night in a hotel when I was jet-lagged… and I was thinking about this and started searching for ways it could be done. I did some back-of-the-envelope calculations and found that, yes, it might become a viable propulsion system. And it turned out it needed many years of work to get from that to a first test flight.”

In the near future, he sees such propulsion systems powering small drones, certainly less buzzy than even the electric ones. Farther out, “he envisions ion propulsion paired with more conventional combustion systems to create more fuel-efficient, hybrid passenger planes and other large aircraft.” Certainly, the idea of a delivery drone silently dropping off The Times or a pint of yogurt would save many sleepless mornings for many of us.

The team’s paper on their exploits can be found in the journal Nature under the title “Flight of an aeroplane with solid-state propulsion.”

*This was reported so widely and effectively that no fewer than four readers sent links.  Thank you, all.

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Named for a mythical hero like its evolutionary predecessors, Aurora Flight Science’s Odysseus is a huge, but ephemeral thing. A wingspan larger than the largest 747’s and a weight no greater than a Smart Car’s (around 1,500 pounds) means this airplane will be slow and frail.  A carbon fiber tube structure covered by lightweight Tedlar™ resembles the construction of Solar Impulse, but without the bulk of carrying a pilot.

Odysseus, larger in span than a 747 and as light as a Smart Car, will stay aloft indefinitely

Since its antecedent was the world record holding distance champion in human-powered aircraft, the manner of flight is no surprise.  Its intended altitude is.  Odysseus takes it to the stratosphere.

It’s the latest revelation in a thirty-year exploration of low-powered, extreme-endurance aircraft.  Before he founded Aurora, John Langford led a group of Massachusetts Institute of Technology (MIT) students in a four-year program that developed three human-powered craft – the Daedalus series.  In its final iteration, Daedalus set the still-extant world record for human-powered flight distance, 72 miles emulating the flight of its mythical namesake between Santorini and Sicily.  The airplane suffered structural failure just yards from its destination, dumping its pilot into the Mediterranean.

Michelob Eco Eagle over Roger Dry Lake during 1987-1988 test flight. This was prototype of Daedalus which would set world record of 72 miles

Aurora Flight Sciences took out the pilot and replaced him with an array of electronics enabling the Solar Eagle to fly extended reconnaissance missions.  In the quest to make the missions perpetual, Aurora continued to expand its aerodynamic and solar-powered fleet.  The latest and larger Odysseus is another milestone in persistence.

Langford explains, “Aurora was founded by the idea that technology and innovation can provide powerful solutions to tough problems that affect all of humankind. Odysseus was an idea born out of Daedalus that is now a real solution to advancing the important research around climate change and other atmospheric chemistry problems.  Odysseus offers persistence like no other solar aircraft of its kind, which is why it is such a capable and necessary platform for researchers.  Odysseus will indeed change the world.”

Carbon tube structure is visible though Tedlar covering. Structure is truss-type like Solar Impulse or classic era light aircraft

Aurora points to Key Enablers that will guarantee Odysseus’ success:

“1. Odysseus can persistently and autonomously remain on station. This enables communication and data gathering over a specific location. No other solar aircraft offers this capability.

“2. Odysseus has a greater year-round global operating zone than any other vehicle in its class.

“3. Odysseus can carry a larger payload than any other aircraft in development or production in its class. This enables more missions and better resulting data quality from each mission.

“4. Odysseus can be deployed at a fraction of the cost of a satellite and can spend dramatically more time aloft than a conventional UAV. It can receive payload and hardware options and can be quickly customized, re-tasked, and re-located as missions evolve”.

Aurora Flight Sciences sees its High Altitude Long Endurance (HALE) machine as providing capabilities for climate and weather researchers, terrestrial observation for agriculture and persistent, on-station operations for communications, connectivity, and intelligence.  Low costs of operation compared to satellites will make these applications more affordable.

Aurora hopes for first flight in the spring of 2019.  Its 243 foot wingspan and light weight will take careful ground handling, with launches by pickup truck.  Almost unlimited endurance, with solar cells charging batteries all day and a feather-like descent during the night, will enable long-range, long-endurance missions.  First flights will involve performing air quality studies over the Midwestern United States.

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Rice Defeats Dendrites

Dr. James Tour of Rice University makes news regularly with different ways of making better batteries.  His latest, a thin-film coating of carbon nanotubes, will enable lithium metal batteries to potentially achieve their full potential.

Rice University chemist James Tour, left, graduate student Gladys López-Silva and postdoctoral researcher Rodrigo Salvatierra use a film of carbon nanotubes to prevent dendrite growth in lithium metal batteries, which charge faster and hold more power than current lithium-ion batteries. Photo by Jeff Fitlow

According to the Tour Laboratory, that potential is worth considering.  “Lithium metal charges much faster and holds about 10 times more energy by volume than the lithium-ion electrodes found in just about every electronic device, including cellphones and electric cars.”  This promise is offset by problems with dendrite growth, the intrusion of tooth-like projections from the surface of the anode metal.  If these growths expand far enough, they poke through the battery’s electrolyte and severely limit battery life.  Worst of all, if the dendrites reach the cathode, they short out the battery, and possibly cause thermal runaway and  fires.

Microscope images of lithium metal anodes after 500 charge/discharge cycles in tests at Rice University show the growth of dendrites is quenched in the anode at left, protected by a film of carbon nanotubes. The unprotected lithium metal anode at right shows evidence of dendrite growth. (Credit: Tour Group/Rice University)

Tour and his student researchers have found that coating the lithium metal electrodes with a thin layer of carbon nanotubes keeps dendrites under control, and allows fast charging and an extended number of charge-discharge cycles.

Tour explained a surprising aspect of the team’s solution. “What we’ve done turns out to be really easy.  You just coat a lithium metal foil with a multiwalled carbon nanotube film. The lithium dopes the nanotube film, which turns from black to red, and the film in turn diffuses the lithium ions.”

Researchers explain, “When the battery is in use, the film discharges stored ions and the underlying lithium anode refills it, maintaining the film’s ability to stop dendrite growth.”

An illustration shows how lithium metal cathodes developed at Rice University are protected from dendrite growth by a film of carbon nanotubes. (Credit: Tour Group/Rice University)

Rice postdoctoral researcher Rodrigo Salvatierra, co-lead author of the paper with graduate student Gladys López-Silva explains, “Physical contact with lithium metal reduces the nanotube film, but balances it by adding lithium ions. The ions distribute themselves throughout the nanotube film.

After stopping dendrite growth for 580 charge-discharge cycles, a sulfurized-carbon film helped the full lithium metal test cells retain 99.8 percent of their coulombic efficiency, “the measure of how well electrons move within an electrochemical system.”

Current research is just the latest in several breakthroughs announced by the school.  Last May, the Tour Laboratory announced development of a graphene nanotube hybrid lithium metal battery with three times the energy density of a conventional lithium-ion cell.  Another development, the use of asphalt, of all things, to help lithium batteries charge faster was announced last October.

Co-authors of the paper, published in Advanced Materials, are Rice alumni Almaz Jalilov of the King Fahd University of Petroleum and Minerals, Saudi Arabia; Jongwon Yoon, a senior researcher at the Korea Basic Science Institute; and Gang Wu, an instructor, and Ah-Lim Tsai, a professor of hematology, both at the McGovern Medical School at the University of Texas Health Science Center at Houston. Tour is the T.T. and W.F. Chao Chair in Chemistry as well as a professor of computer science and of materials science and nanoengineering at Rice.

The research was supported by the Air Force Office of Scientific Research, the National Institutes of Health, the National Council of Science and Technology, Mexico; the National Council for Scientific and Technological Development, Ministry of Science, Technology and Innovation and Coordination for the Improvement of Higher Education Personnel, Brazil; and Celgard, LLC.

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Fred To Receives a Well-Deserved Award

Fred To (pronounced Toe) lives in England and was one of a small group who built and flew the world’s first solar-powered airplane in December 1978. They flew just a few months before Larry Mauro lofted his solar-riser in April 1979. Both airplanes were limited by the technology of the day, lithium-ion batteries still over a decade away, and the best solar cells achieving less than five-percent efficiency. Fred wrote to tell your editor of the award.

Fred To stands on stage with Prince Albert of Monaco, a patron to green aviation

“I was in Montreux Switzerland a few weeks ago, and on the 22nd of October I received an award from prince Albert II of Monaco for Solar One, which is now formally accepted as the first solar powered aircraft to fly. It was a great occasion and my family are so proud. All the great past pioneers were there and it was an honor to meet them; now I have new friends from all over the world. ”

The occasion, described on Raphael Domjan’s SolarStratos web site, commemorated pioneers in solar energy.  “HSH Prince Albert II of Monaco attended the grand opening of the ‘Pioneers and Adventurers of Solar Energy’ exhibition at the PlanetSolar Foundation hosted by the Fairmont Montreux Palace Hotel. Foundation director, Raphaelle Javet, our very own eco-explorer and Foundation president, Raphael Domjan, and a group of solar energy pioneers gave the Prince a preview of the exhibition.”

Fred wit some of his new friends in the SolarStratos hangar

Surrounded by his family and relishing his new friendships, Fred had what looks to be a great evening and some interesting trips to workshops of fellow innovators.  Inexplicably, Eric Raymond of Sunseeker fame does not seem to have been in attendance.

Self-effacing as always, Fred shared the glory of the moment. “I accepted this award on behalf of my late partner David Williams, also on behalf of Larry Mauro and all the other pioneers present there at the ceremony. I pointed out that not many of those present would have even heard of Larry Mauro. To the credit of the organizers, they also mentioned Larry in their book for that occasion. And to think that my ex-wife and David’s widow Anne both used to say that David and I were playing at building aeroplanes and not earning a living. I’m glad that I was also a film maker and so there is a video record of the project.” His half-hour film shows the efforts he and David Williams exerted to bring the project to fruition.

After this achievement, what was Fred to do? He followed up with dozens of other amazing flying machines, including an inflatable flying wing that featured the first fly-by-wire control system.

Popular Science, in its March, 1982 issue, noted the most impressive part of a most impressive project. “The most intriguing feature of the design is that flight control by the pedaler is not necessary. The 11 electric model airplane servos that operate the ailerons, elevator and rudders can be remotely-controlled with a transmitter by a ‘pilot’ on the ground.”

Phoenix Prototype on London Docklands, March 1982

Fred had the first “fly-by-wire” aircraft in the world, brought about by the airplane’s extreme flexibility that obviated the use of conventional control cables. That extreme flexibility led to extreme crashworthiness, the aircraft (and pedaler) surviving several short plummets to earth with a flubber-like resilience.

These excursions into human-powered flight led to Fred’s long-term association with what became the British Human Powered Flying Club. His work with inflatable craft led to an association with Prospective Concepts, a Swiss firm that often astounds with its flying creations. He helped create a flying Stingray that swept its way through Czech and Swiss skies with over 300 flights from 1995 through 2000.

Commentary with the video explains, “Res Kammer worked side by side with Fred To to develop cutting patterns for all fabrics and the construction of this prototype for Prospective Concepts in Switzerland. The workshop was based at Burgdorf. Alan and Fred To shared the camera work. The pneumatic management was designed and produced by Hansueli Ammann. Thomas Rozhon, Jorg Kammer and Stepfan Zechner did all the cutting and gluing. The fabric was obtained from Greengate polymer in the UK.”

Prospective Concepts had some interesting prospects in mind for the Stingray, although they don’t seem to have yet been realized. A “new and improved version” is to have pneumatic controls, a cabin integrated into the weight-bearing geometry, electric ducted fan propulsion and “a multifunctional landing gear.”

Whatever comes of his enormously creative machines, Fred will continue with more surprises for all of us. These surprises will be quietly astonishing, joyful things, reminding us all of what dreams can become.

This Just In!

Fred sent an additional detail about his inflatable wing this morning.  “I am now trying to develop a smaller version of Phoenix, it will be machine made and will be 0.8 scale of the original, weight will go down a lot and I hope it could be sold cheaply. The owner will only need to order a replacement wing if it is damaged. I’m starting to get a small team together and find a backer.”

The original Phoenix was a hand-made effort, with Fred recruiting some talented seamstresses to sew a complex inflatable structure together.  Machine production could bring production costs down considerably.  Since the original could be rolled up and transported on Fred’s compact car, the 80-foot version should be even more portable.  At one point, Fred had considered putting an electric motor on Phoenix to assist the human power plant.

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The Diamond/Siemens Hybrid Test Bed

One should follow Dr. Frank Anton’s Twitter account – or at least check it occasionally.  Dr. Anton is head of Siemen’s Electric Aviation Division and posts new developments regularly.  Siemens is supplying motors to Diamond Aircraft’s prototype hybrid, a tidy tri-motor if you count the engine/generator in the nose of the formerly single-engine airplane.

Diamond/Siemens DA-40 reconfigured with canard-mounted motors.  Photo: Diamond Aircraft

Partnered with Austria’s Diamond Aircraft Industries GmbH, Siemens motors powered an adaptation of their DA40 four-seat airplane.  A Diesel engine/generator in the nose of the formerly single-engine machine charges two 12-kilowatt batteries behind the passenger compartment and provides power to the two Siemens motors on the canard.  The whole thing looks a bit like a large economy-size Cri-Cri.

Started in 2013, the project is under the supervision and finance of the Bundesministerium für Wirschaft und Energie (BMWi, German Ministery of Economics) and the Forschungsförderungsgesellschaft GmbH, FFG (Society for the development of the research, Austria). The project has been split into two main work packages.

Siemens AG was responsible for the design and development of the electric powertrain, done within the framework of the German LuFo program, run under the DLR, Germany’s NASA.  Diamond Aircraft was responsible for the reconfiguration of the aircraft and installation of the hybrid-electric powertrain.  Diamond partnered with the TERA Group and the Johannes Kepler Universität Linz to perform aerodynamic analysis of powerplants and airframe.

Modified DA40 in front of Austria’s Diamond Aircraft factory. Photo: Diamond Aircraft

With a 110 kilowatt (147.4 horsepower generator in the nose and two motors on the canard putting out a combined 150 kilowatts, a pilot has a range of choices that allow safe flight.  Diamond reports, “With a dedicated power lever, the pilot can control the energy flow between the generator, batteries and motor. The pilot can select either pure electric mode (generator off), cruise mode (generator provides all power to the motor), and charge mode (generator charges the batteries). Pure electric, the aircraft has an endurance of approximately 30 minutes. The hybrid system extends this to 5 hours.”

Diamond’s test pilot Ingmar Mayerbuch’s smile reflects success of initial flight.  Photo: Diamond Aircraft

Diamond’s test pilot, Ingmar Mayerbuch, was satisfied with the system and the results of his 20-minute outing in the hybrid.  “The first flight exceeded all our expectations. The combination of the hybrid powertrain and the configuration of the aircraft is just perfect. We reached 130 knots at medium power output and climbed to an altitude of 3,000 feet.”  Ingmar was able to try out all three power modes during the October 31st flight.

Siemens and Diamond anticipate a five-percent growth per year in air traffic over the coming decades.  Each firm realizes it needs to take responsibility to counter growing aircraft emissions.  Until batteries are able to pull all the weight of that charge, we will probably see hybrid aircraft of varied configurations to increase fuel efficiency and lower emissions.

This configuration provides added safety, with the airplane capable of a safe landing even with partial systems’ failure.  Dr. Anton sees the reduced use of fossil fuels, the economy of operation and the safety of the approach as good omens for the future.  He explains, ““Serial-hybrid electric propulsion systems and distributed propulsion architectures for us are the key to a more sustainable flight future also in higher power classes. The Diamond flying testbed will help us to understand the requirements for these new propulsion technologies and to be prepared for the challenges of larger-scale applications.”

He sums it all up in an October 30 Tweet.

#HybridElectricPropulsion technology for #eAircraft is more than just a compromise until batteries improve. Many advantages of its own. Distributed propulsion with cables instead of shafts. Battery as backup power. Low noise. Better fuel economy.

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