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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