How long is the engine operating time with fully charged batteries?
13 minutes at maximum power and maximum climb speed. A longer powered engine operating time is achieved at horizontal flight, the flight endurance depends on the aircraft speed. The largest distance (approximately 190 km / 97 nautical miles) is covered by alternatingly climbing at optimum climb settings and gliding at optimum glide angle.
My cellphone runs on Li-ion batteries. After two years of use, these batteries have
degraded strongly. Why is this not the case with the batteries used in the Antares?
Did you by any chance get that cellphone with a two year contract? There is a big difference between consumer electronics batteries and industrial grade automotive batteries.
The batteries are warmed up to reach the highest efficiency. How long does it take?
This is dependent on the battery temperature before you start heating. The batteries heat at a rate of approximately 1°C/min (1,8°F/min). For optimum performance the batteries are heated to between 20 and 30°C. However, power is available also at lower temperatures. The charger can provide energy for battery heating while the aircraft is on the ground. During the flight the batteries are kept at a constant temperature. This needs only a small amount of energy, as they are very well isolated.
Once I have used the whole climbing energy of the batteries, is it possible to extend
the motor and taxi back to the hangar?
Taxiing requires very little energy. There will, even after a “full discharge”, normally be enough energy left in the batteries to allow extending the motor and taxiing back to the hangar. The pilot should naturally make sure that the cell voltages remains within operating specs. The hydraulic system and the board instruments are connected to a secondary redundant battery. Even in the case of a total energy breakdown of the main batteries, the board instruments stay operative, and retraction of motor and landing gear remains possible.
Why has Antares been designed with a push configuration?
With the propeller in a pull configuration the Antares could achieve a further noise reduction. In this new configuration, however, the propeller disk would have to remain in the same position of the push configuration to guarantee a safety distance to the cockpit. with this arrangement, the motor supports and their hinge point would have to move backwards along the fuselage. As a result, the position of the retracted engine would also move further back and it would be impossible to achieve the optimum contraction ratio behind the cockpit.
Is it possible to use the propeller to recharge the batteries while descending?
In theory, the combination propeller, engine and power-electronics can run as a wind turbine. However, the propeller is highly inefficient in this mode, so it would not really pay off.
Is it possible to buy the ANTARES 20E as a pure glider, and upgrade it later to a
motorglider?
This is currently not possible. You might however want to take a look at the Antares 18S. It can easily be upgraded into an Antares 18T self-sustainer.
Is it possible to "refuel" the batteries with solar cells in-flight?
There are several arguments against this technology:
- The surface of the fuselage and the elevator is not sufficient to charge the batteries. In order to achieve the necessary energy production the wing surface would have to be covered, too.
- The surface quality of the solar cells is not as good as a polished glider surface. The actual gliding performance of the Antares cannot be achieved with a wing fully covered with solar cells.
- The cost of this technology is very high, as the manufacturing and finish cost of such wings have to be added to price of the solar cells.
- White gelcoat is utilized to reflect the maximum amount of solar energy while solar cells are designed to capture as much of it as possible. The low efficiency of solar cells (max 25-30%) means that a lot of energy is turned into heat. Making the composite structure of the wing capable of dealing with this heat is very expensive.
Can the Antares run on Fuel cells instead of on Batteries?
The Fuel cell is an interesting technology. Sadly, current fuel cell technology is not capable of delivering the high power required for takeoff and climb. One could imagine a system where batteries provide most of the power for take-off and climb while a fuel cell system slowly recharges the batteries during unpowered flight. However, assuming we maintain system weight, this would mean a reduction in number of batteries and thus a substantial reduction in instantly available altitude. It would also mean a dramatic increase in system price and complexity. As a result, we do not see the application of fuel cells in series aircraft in the near future.
However, we continue to monitor this technology closely.
Lithium Polymer cells are supposed to be so much better than Li-Ion. Why are you not
using them?
Sorry. So far we have not come across Lithium Polymer cells with better overall performance than the Li-Ion cells we are currently using. We are using VERY good cells ;-)
However, the Antares propulsion system has been designed for adaptability, and should a technological breakthrough take place, then it can easily be modified to accept new cell types. We have already once made such a change, going from NiMh to Li-Ion.