E-ROP is a multi-party program using an Antares self-launching sailplane. FES and Adventec have crafted a hybrid version of the Antares 20e with a front electric sustainer (FES) motor in place of its tall mast-mounted motor. An incremental program, E-ROP begins by replacing the retractable unit with an FES motor on the nose. This reduces the drag created by the motor being raised into position and simplifies operation.
The FES Antares flew for the first time on April 19 with Klaus Ohlmann at the helm. Ulrich Bronet recorded this short video.
Under development since 2016, E-ROP will benefit from an advanced battery package from research partner AdvanTec GmbH. According to the project, “The concept provides for batteries in the fuselage and wings, which have an energy capacity of 22 [kilowatt-hours] at a total take-off weight of 650 [kilograms] (1,433 pounds) MTOM (Maximum Take Off Mass).” 22 kWh is about one-fifth of a Tesla battery package and will allow up to 450 kilometers (280 miles) range for the Antares.
Initially, a smaller battery pack behind the pilot, with only four kWh capacity, allows a takeoff and about 100 kilometers (62 miles) range. The larger pack with additional batteries in the wing enables the 450 kilometer noted above.
With a range extender (REX, or motor generator) installed, The Antares takes off with battery power and, “While cruising the motor generator supplies the necessary energy and charges the battery at the same time.” Depending on fuel load, the craft could achieve a range of 2,500 kilometers (1,553 miles). In the video, Senger notes the Antares can travel 1,000 kilometers (620 miles) on 20 liters of fuel. This is exceptional since the generator is driven by a Wankel engine, normally a fuel-hungry powerplant.
Senger explains the craft requires only 4.8 kilowatts to maintain level flight. This efficiency is comparable to the attempts a decade ago to design cars that could achieve 100 kilometers on three liters of fuel. So-called “three-liter cars” demonstrated great efficiency, but were usually small, light, and often cramped. An article in this blog noted even a 747 traveling at 500 mph achieved something like 100 passenger miles per gallon. Antares squeezes 100 kilometers out of every two liters of fuel, faster and more economical than the three-liter cars of the early 2010s.
AdvanTec claims to date, there are “no optimal drive components” available that meet General Aviation “special requirements” for efficiency and weight. Boosting the FES motor to 300 Volts and using a 1.2-meter (3.39 foot) propeller helps loft and speed the Antares.
A follow-up project, HEAR (Highly Efficient Electric Powertrain for Aviation Applications), is now in its concept phase. There’s even a chance the Wankel could be replaced with a hydrogen fuel cell. Larger craft up to 130 kW (174 hp.) could follow from this research.
Of course, “The not inconsiderable financial resources required for this must be raised through research funds and sponsors.”
AdvanTec includes VOCUS GmbH, which makes parts for Airbus Helicopters and for large cargo and passenger planes, including “essential” parts for doors.
For the E-ROP project, the company created 3D-printed parts for the battery modules and fairing for the under-wingtip wheels. They also created a one piece instrument binnacle through additive manufacturing. This is all part of another project, AMPHEA, or Additive Manufacturing for Plugin Hybrid Electrical Aircraft. AMPHEA aims to develop and integrate the first additively manufactured heat exchanger in an aircraft. The heat exchanger, above the Wankel engine, would be part of the fuselage structure, eliminating the weight of a separate system.
Stefan Gorkenant, CEO and head of marketing at AdvanTec and VOCUS GmbH adds a cautionary note. “We are pursuing this vision with a lot of passion, but we still have a long way to go in terms of development.”
Besides the physical elements designed for this much-modified Antares, the group is a work on the, “Optimization of a BMS (Battery Management System) for electric mobility systems.”
The team is also pushing reduced danger of thermal runaways in battery packs. Regardless of battery chemistry, there seem always to be that danger. Cell holders printed from Onyx FR are being tested to ensure they will not “Burn independently in the event of a single cell catching fire.” The group claims their battery packs already have twice the energy density of batteries typically installed in Antares sailplanes. Safety and light weight will make an advantageous package available. If that’s successful, it could be adapted to other larger and more powerful aircraft.
In a follow-up entry, we will look at what Klaus Ohlmann hopes to accomplish with his new mount. With over 60 world gliding records, Klaus has big plans.