torsdag 17. mai 2018

Uber utvikler urban massetransport, men hva mangler? - AW&ST

Bortsett fra ideer, så er svaret alt. Abosloutt alt. Standarder for tekniske løsninger, luftrommets beskaffenhet, flygere, om de er i flyet eller på bakken, software sikkerhet dersom der er automatiske flyvninger det er snakk om; ja, absolutt alt. Det tar mange å å utvikle slikt, og USAs FAA sier rett ut at standardene må være de samme som for regelmessig kommersiell flyging i dag. Om 10 år kan vi kanskje se praktiske, godkjente løsninger med FAR/JAR standarder eller tilsvarende. (Red.)

Industry may be unsure whether it is a vision or a mirage, but Uber’s Elevate initiative is pushing hard across a wide front in an effort to advance urban air mobility from concept to reality as fast as possible.
At its second Elevate Summit in Los Angeles on May 8-9, Uber presented an aggressive path to aerial ridesharing “at scale”—networks of hundreds of vehicles making tens of thousands of flights carrying hundreds of thousands of passengers per day between scores of dedicated “skyports” over gridlocked cities around the world at affordable prices.
To support this ambitious end-state vision, Uber has announced more partnerships on electric vertical-takeoff-and-landing (eVTOL) vehicles, batteries, motor and rotor technology, airspace management and vertiport design. And some of its vehicle partners have revealed their thinking on eVTOLs meeting Uber’s targets.
“We want to make sure people understand that we are not designing this to be a handful of aircraft and something for the elite, that right from our initial requirements we are forcing every single element to be focused on a real transportation capability, and that we are never going to develop systems that can’t be scaled,” says Mark Moore, director of engineering for vehicle systems.
  • Elevate vehicle partners unveil eVTOL air-taxi concepts
  • Uber to develop its own safe, certifiable battery packs
  • Reference models to help industry tackle noise challenge
Uber has revealed Karem Aircraft as its latest vehicle partner, joining Bell, Boeing subsidiary Aurora Flight Sciences, Embraer and Pipistrel Aircraft. Karem is developing the Butterfly, a quad tiltrotor with optimum speed rotors. The large-diameter, low-speed rigid rotors reduce the power required and noise in hover, enabling the aircraft to meet Uber’s mission requirements on today’s batteries, says Karem President and CEO Ben Tigner.
An agreement was also announced with Taiwanese battery maker E-One Moli Energy Corp. to use its lithium-ion cells in prototype battery packs that Uber will develop and offer to its vehicle partners. Battery packs are planned to be ready for demonstration flights in 2020, with certified batteries to be available for commercial operations in 2023, says Celina Mikolajczak, Uber’s director of engineering for battery systems.
Each module in Pickard Chilton and ARUP’s Sky Tower can handle 180 landings and takeoffs and 1,800 passengers per hour. Credit: Uber Concept

Uber worked with Karem to model its eVTOL performance with Moli batteries. These provide a pack energy density of 179 Wh/kg, well below Uber’s target. But even at an end-of-life density of 143 Wh/kg, the modeling showed these batteries provide an 84-mi. range. And they allow the vehicle to complete 10 25-mi. missions over the 3-hr. surge period, carrying four passengers and a pilot and maintaining a 6-mi. reserve, with 8 min. charging between flights, she says.
“Our battery experts have analyzed that vehicle and shown that, with the Moli cells, it can have a reasonable range that meets our needs—even with current batteries and the overhead from the cell to pack, that can be achieved with the current state of the art,” says Moore.
Some are skeptical about Uber’s aggressive timescale, which Moore describes as a “forcing function” for the required advances. Partners are supporting the plan for demo flights with experimental vehicles in 2020, but commercial operation will require certification. The industry is hoping to certify eVTOLs under revamped Part 23 rules. “I don’t think that is too ambitious, but I am not going to make any commitments,” FAA Acting Administrator Dan Elwell told the summit.
Uber says eVTOLs must be all-electric and fairly fast (150-200 mph) to fit into its network, which calls for high throughput to minimize costs. This means using aircraft that transition to wingborne flight for cruise efficiency. The company is not interested in multicopter or hybrid-electric vehicles. “We’re 100% certain that is not the right solution, because it is about throughput and productivity, and you have to be able to guarantee time savings because that is our value proposition,” says Moore.
Embraer unveiled the first eVTOL concept developed by its Embraer X innovation unit in the U.S. The lift-plus-cruise configuration has eight rotors on two wingtip booms for vertical flight and a shrouded pusher propeller for forward flight. The design characteristics are derived from interviews with potential users in several U.S. and international cities, says Antonio Campello, president and CEO of Embraer X.
DreamMaker is the first eVOTL concept produced by the Embraer X innovation unit based in Melbourne, Florida. Credit: Uber Concepts

Aurora CEO John Langford showed several potential eVTOL configurations the company is studying but emphasized that “the key underlying technology is certifiable autonomy.” Aurora’s research shows urban air transport will not make money if the vehicles are piloted, he says, adding, “Autonomy is absolutely essential to getting the utilization and safety rates—and there are not enough pilots.”
Slovenia’s Pipistrel teased its “different” eVTOL concept, a winged lifting-body “cruise-plus-lift” design optimized for speed and range but without any visible means of vertical lift. “Nothing tilts,” says Tine Tomazic, director of research and development, declining to reveal the “magic bits” of the dedicated, “completely integrated” lift system, which he says is simplified and distributed, easy to maintain and affordable.
Uber unveiled its own eVTOL common reference models (eCRM), developed to help industry design new classes of aircraft with which it has no experience. “Manufacturers know how to produce aircraft, but none have developed an eVTOL for urban air mobility,” says Rob McDonald, Uber’s head of vehicle engineering. “We look for gaps in technology, tools and testing and spend money to fill those gaps and share the results with our partners.”
Taking a leaf out of NASA’s book, Uber is developing the distributed-propulsion eCRMs for industry to use to develop and validate designs. The first, eCRM-001, has four sets of paired rotors for vertical lift and tilting wingtip propellers for vertical lift and forward thrust. Another concept, eCRM-003, has four sets of rotors for vertical flight and a tail-mounted propeller for cruise flight.
NASA uses the CRM to enable different teams to work on the same hard problem—the design of high-lift systems for commercial aircraft—and share their results. “All these vehicles have complex flow problems, where propulsion, aerodynamics and control interact and cause acoustic issues,” Moore says. “This requires variable-fidelity tool sets that need to be validated and compared, similar to what NASA does with the high-lift CRM.” The eCRMs also help Uber validate its Elevate requirements, he says.
Uber’s concepts feature retractable, stacked corotating rotors for vertical lift. These have two independently driven blade sets placed on top of each other and rotating in the same direction, and promise to be quieter than traditional coaxial contrarotating rotors, with higher performance.
Noise is a critical concern for Uber, as it will drive public acceptance of eVTOLs, and its goal is to achieve acoustic signatures that map into background city noise levels. This equates to sound exposure levels around 15 dB quieter than existing light helicopters, or about 70 dB at 500 ft., the company says.
Rather than being at right angles to each other, the corotating blade sets are just 10 deg. apart. This means the stacked blades act like a wing and high-lift flap, increasing performance. Nonuniform blade spacing, used on the scissor tail rotor of the Boeing AH-64, also changes the acoustic signature and reduces noise. “When the rotors are rotating in the same direction, they don’t have the wake interference problems that contrarotating rotors have,” says McDonald.
Butterfly is a quad-tiltrotor eVTOL using Karem’s optimum-speed rotor technology to reduce power and noise. Credit: Uber Concept

Uber has signed a cooperative research and development agreement with the Army Research Laboratory (ARL) to develop the stacked corotating rotor. LaunchPoint Technologies will develop a “unique” motor to power the rotors. “If we drive them from independent electric motors, then we have a level of redundancy in the system because we have a simple way of driving them individually. We can also use modern digital controllers for these motors, to do phase control very precisely,” says McDonald.
The agreement with ARL, at Aberdeen Proving Ground in Maryland, will produce the first usable set of stacked corotating rotors. “We’ll be proceeding into validation testing in partnership with them, and this will provide concrete data, first as an isolated vertical-lift propulsor, and then later in an integrated context, which we can share across all of our [vehicle] partners,” says Moore.
Another key challenge to scaling up urban air mobility is the infrastructure required at skyports to fast-charge the battery-powered eVTOLs in the few minutes available between flights as passengers board and deboard aircraft. Uber has partnered with ChargePoint, the largest electric-vehicle charging company, to develop the required DC fast-charging infrastructure.
ChargePoint President and CEO Pasquale Romano displayed a prototype charging connector at the summit. The rugged design provides four 500-amp, liquid-cooled circuits capable of delivering 2 megawatts of power to charge an eVTOL in 5 min. between flights. The connector will also cool the batteries to remove 50-75 kW in waste heat during fast charging and is designed to withstand repeatedly being dropped and reeled in under the skyport flight deck to keep the ramp clear.
Romano says the connector is similar to that being developed to charge large electric trucks such as Tesla’s Semi, which have huge battery packs, and he urges the two industries to cooperate on a common design. While air taxis will have smaller batteries, they will be split into multiple packs for redundancy and safety. The connector will allow four packs to be charged simultaneously, he says.
Uber plans to begin with demonstration flights of experimental vehicles in 2020 in Dallas/Fort Worth and Los Angeles—plus an international city, for which it has launched an open call for bids after abandoning plans to fly in Dubai. Commercial service is slated to begin in 2023, involving about 50 certified eVTOLs making 1,000 flights a day between a handful of skyports in each city. But by 2025, the company wants to begin scaling up operations so it can bring down costs to attract more riders.
At scale, skyports would need to handle 1,400 flights per hr., with vehicles spaced 15 sec. apart in multiple arrival and departure “skylanes.” Futuristic designs for these skyports were unveiled at the summit. Selected from dozens of submissions, the concepts from six architecture firms are designed to meet specifications that include the ability to handle more than 4,000 passengers an hour within a 3-acre footprint.
The concepts, from the Beck Group, BOKA Powell, Corgan, Gannett Fleming, Humphreys & Partners Architects and Pickard Chilton with ARUP, will be further developed under partnerships already established by Uber with real estate companies Hillwood Properties and Sandstone Properties. Most of the designs are modular and scalable from fewer than 100 landings per hour to more than 1,000.
Ideas showcased include the ability to turn vehicles around in as little as 6 min. BOKA Powell’s concept features a 930-ft.-long J-shaped track along which vehicles would move from landing to takeoff at 2 mph, all the while tethered to a recharging cable. In Corgan’s design, multiple conjoined modules would straddle highways to take advantage of the existing infrastructure.
Uber is also eyeing the challenge of manufacturing thousands of eVTOLs per year to meet its projected demands at scale. “It is OK if vehicle production is in the typical 50, 150, 300 aerospace quantities through 2025, but then it gets real,” says Moore. “Then, these vehicles need to start being produced at 2,000, 3,000, 5,000 units per year per manufacturer to be able to accomplish our objectives.” Moore says Uber is trying to build a bridge between aerospace and the automotive industry to enable high-volume production of high-quality products at much lower cost.
The air traffic management necessary to enable such high throughput in airspace shared with other aircraft, manned and unmanned, is perhaps the most challenging aspect of Elevate, and Uber has formed an internal team to help find solutions. Uber has signed a second Space Act Agreement with NASA under which it will share plans for implementing an aerial ridesharing network. NASA will use its airspace management modeling and simulation tools to assess the impact of small aircraft—from delivery drones to eVTOLs—in dense urban airspace. 
Cracking the airspace code is critical to reaching the scale Uber needs to be profitable. “For economic viability, the No. 1 parameter is trip density. Trip density is why the VLJ [very light jet] market failed,” says Moore, citing the collapse of DayJet and the Eclipse 500. “If we stick to the urban core, which is what the battery technology enables in the nearer term, we get fantastic trip density. We can have an efficient network that actually makes sense at a reasonable price,” he says.  “I will not repeat the VLJ fiasco.” 

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