# Electric VTOL Configurations Comparison

^{*}

^{†}

## Abstract

**:**

## 1. Introduction

## 2. Materials and Methods

- -
- Vectored Thrust
- -
- Lift + Cruise
- -
- Wingless
- -
- Hoverbikes
- -
- eHelos

- -
- 7 km urban mission
- -
- 30 km extra-urban mission
- -
- 100 km long-distance mission

## 3. Results

#### 3.1. Wingless Multirotor Configuration

#### 3.2. Lift + Cruise Configuration

#### 3.3. Vectored Thrust

#### 3.4. Reference Mission Performance

- -
- 15 s of takeoff at hover power;
- -
- acceleration at $2\mathrm{m}/{\mathrm{s}}^{2}$ from zero forward speed to cruise speed at hover power;
- -
- cruise flight;
- -
- deceleration at $-2\mathrm{m}/{\mathrm{s}}^{2}$ from cruise speed to zero forward speed at hover power;
- -
- 15 s of landing at hover power.

## 4. Discussion

## 5. Conclusions

## Author Contributions

## Funding

## Conflicts of Interest

## References

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**Figure 4.**Kitty Hawk hoverbike [30].

**Figure 5.**Aquinea Volta [31].

**Figure 6.**E-Hang 184 specs and dimensions, from E-Hang website [15]. Dimensions in the top view are in millimeters.

**Figure 7.**Kitty Hawk Cora geometry [27].

**Figure 8.**Lilium Jet geometry [13].

**Table 1.**E-Hang 184 specifications from E-Hang website [15].

Maximum total power | 152 kW |

Number of motors | 8 |

Total battery energy | 14.4 kWh |

Propeller diameter | 1.6 m |

Net weight | 260 kg |

Total flight time | 25 min |

Rated payload weight | 100 kg |

Average flight speed | 100 km/h |

Geometry | ||

Propeller area | 2.01 ${\mathrm{m}}^{2}$ | Computed |

Total disk actuator area | 8.04 ${\mathrm{m}}^{2}$ | Computed |

Battery | ||

Energy density | 157 Wh/kg | Assumed [36] |

Specific power | 735 W/kg | Assumed [36] |

Max power | 67 kW | Computed |

Mass balance | ||

Battery mass | 92 kg | Computed |

Empty weight | 168 kg | Computed |

Payload weight | 100 kg | E-Hang data |

Hover performances | ||

Average power consumption | 34.6 kW | Computed |

Power required to hover | 47 kW | Computed |

Energy required for 1 min of hover | 0.79 kWh | Computed |

Total hover time | 20.5 min | Computed |

Disk loading | 440 N/${\mathrm{m}}^{2}$ | Computed |

**Table 3.**Kitty Hawk Cora specifications from Kitty Hawk’s website [2].

Wingspan | 11 m | Website data [2] |

Wing chord | 1 m | Estimated from Figure 7 |

Wing surface | 10 m^{2} | Website data [2] |

Number of lift fans | 12 | From Figure 7 |

Lift propeller diameter (external) | 1.3 m | Estimated from Figure 7 |

Lift propeller diameter (hub) | 0.5 m | Estimated from Figure 7 |

Cruise propeller diameter | 2 m | Estimated from Figure 7 |

Range | 100 km | Website data [2] |

Flight time (with 10 min reserve) | 19 min | Website data [2] |

Speed | 180 km/h | Website data [2] |

Passenger cargo capacity | 181 kg | Website data [27] |

Rear landing gear-tail angle | 15.9° | Estimated from Figure 7 |

Fuselage-wing angle | 12.4° | Estimated from Figure 7 |

Propeller area (external, single propeller) | 1.3 m^{2} | Computed |

Propeller area (internal, single propeller) | 0.2 m^{2} | Computed |

Circular crown area (single propeller) | 1.1 m^{2} | Computed |

Total disk actuator area | 13.6 m^{2} | Computed |

Total mass | 1224 kg | Data [27] |

Power required to hover | 228 kW | Computed |

Battery energy specific density | 157 Wh/kg | Assumed [36] |

Battery power density | 735 W/kg | Assumed [36] |

Minimum battery mass | 310 kg | Computed |

Battery mass | 400 kg | Assumed |

Total battery energy | 63 kWh | Computed |

Battery mass to total mass ratio | 33% | Computed |

Energy for 1 min of hover | 3.8 kWh | Computed |

Total hover time | 16.5 min | Computed |

Disk loading | 880 N/m^{2} | Computed |

Fuselage | ||

Length | 4.8 m | Estimated from Figure 7 |

Diameter | 1.5 m | Estimated from Figure 7 |

Wet surface | 13 m^{2} | Computed |

Horizontal tail | ||

Surface | 2 m^{2} | Estimated from Figure 7 |

Thickness to chord ratio | 0.12 | Assumed |

Chord | 0.75 m | Estimated from Figure 7 |

Vertical tail | ||

Sweep | 10° | Estimated from Figure 7 |

Thickness to chord ratio | 0.12 | Assumed |

Height | 1 m | Estimated from Figure 7 |

Chord | 0.75 m | Estimated from Figure 7 |

Wet surface | 1.5 m^{2} | Computed |

Number of vertical tails | 2 | From Figure 7 |

Pylons | ||

Length | 3.5 m | Estimated from Figure 7 |

Width | 0.16 m | Estimated from Figure 7 |

Height | 0.36 m | Estimated from Figure 7 |

Wet surface | 3.76 m^{2} | Computed |

Number of pylons | 6 | From Figure 7 |

Propellers | ||

Length | 1.3 m | Estimated from Figure 7 |

Diameter | 0.3 m | Estimated from Figure 7 |

Wet surface | 0.8 m^{2} | Computed |

Number | 12 | From Figure 7 |

Landing gear | ||

Tire width | 0.15 m | Estimated from Figure 7 |

Tire height | 0.3 m | Estimated from Figure 7 |

Surface | 0.045 m^{2} | Computed |

Fuselage width | 1.4 m | Estimated from Figure 8 |

Fuselage length | 3.6 m | Estimated from Figure 8 |

Wingspan | 6 m | Estimated from Figure 8 |

Root chord | 0.78 m | Estimated from Figure 8 |

Tip chord | 0.42 m | Estimated from Figure 8 |

Man lying on the tarmac | 1.52 m | Estimated from Figure 8 |

Suitcase | 0.46 m | Estimated from Figure 8 |

Fans diameter | 0.15 m | Estimated from Figure 8 |

Number of fans | 36 | From Figure 8 |

Total mass | 490 kg | Assumed |

Power required to hover | 187 kW | Computed |

Battery energy specific density | 157 Wh/kg | Assumed [36] |

Battery power density | 735 W/kg | Assumed [36] |

Battery mass | 240 kg | Computed |

Total battery energy | 38 kWh | Computed |

Battery mass to total mass ratio | 49% | Computed |

Energy for 1 min of hover | 3.12 kWh |

Total hover time | 12.1 min |

Disk loading | 7500 N/m^{2} |

E-Hang 184 | Kitty Hawk Cora | Lilium | |
---|---|---|---|

Cruise power | 34.6 kW | 63 kW | 28 kW |

Cruise speed | 100 km/h | 180 km/h | 252 km/h |

Takeoff and landing power | 42.1 kW | 228 kW | 187 kW |

Total battery energy | 14.4 kWh | 63 kWh | 38 kWh |

E-Hang 184 | Cora | Lilium | |
---|---|---|---|

Takeoff and landing time | 30 s | 30 s | 30 s |

Takeoff and landing energy | 0.35 kWh | 1.9 kWh | 1.6 kWh |

Acceleration/deceleration | 2 $\mathrm{m}/{\mathrm{s}}^{2}$ | 2 $\mathrm{m}/{\mathrm{s}}^{2}$ | 2 $\mathrm{m}/{\mathrm{s}}^{2}$ |

Acceleration time | 14 s | 25 s | 35 s |

Acceleration energy | 0.16 kWh | 1.58 kWh | 1.82 kWh |

Acceleration/deceleration distance | 193 m | 625 m | 1225 m |

Deceleration time | 14 s | 25 s | 35 s |

Deceleration energy | 0.16 kWh | 1.58 kWh | 1.82 kWh |

Total time for takeoff, landing, acceleration, and deceleration | 1 min | 1.3 min | 1.7 min |

Total energy for takeoff, landing, acceleration, and deceleration | 0.7 kWh | 5.1 kWh | 5.2 kWh |

E-Hang 184 | Kitty Hawk Cora | Lilium | |
---|---|---|---|

Cruise distance | 6.6 km | 5.8 km | 4.6 km |

Cruise time | 3.9 min | 2.0 min | 1.1 min |

Cruise energy | 2.3 kWh | 2.0 kWh | 0.5 kWh |

Total time | 4.9 min | 3.3 min | 2.8 min |

Total energy | 3.0 kWh | 7.1 kWh | 5.7 kWh |

E-Hang 184 | Kitty Hawk Cora | Lilium | |
---|---|---|---|

Cruise distance | 29.6 km | 28.8 km | 27.6 km |

Cruise time | 17.7 min | 9.6 min | 6.6 min |

Cruise energy | 10.2 kWh | 10.1 kWh | 3.1 kWh |

Total time | 18.7 min | 10.9 min | 8.2 min |

Total energy | 10.9 kWh | 15.2 kWh | 8.3 kWh |

E-Hang 184 | Kitty Hawk Cora | Lilium | |
---|---|---|---|

Cruise distance | - | 98.8 km | 97.6 km |

Cruise time | - | 33.0 min | 23.2 min |

Cruise energy | - | 34.6 kWh | 10.9 kWh |

Total time | - | 34.3 min | 24.9 min |

Total energy | - | 39.7 kWh | 16.1 kWh |

E-Hang 184 | Kitty Hawk Cora | Lilium | |
---|---|---|---|

Disk loading (N/m^{2}) | 440 | 880 | 7500 |

Total hover time (min) | 20.5 | 16.5 | 12.1 |

Cruise speed (km/h) | 100 | 180 | 252 |

Practical range (km) | 42 | 107 | 203 |

Flight time (min) | 25 | 36 | 48 |

E-Hang 184 | Kitty Hawk Cora | Lilium | |
---|---|---|---|

7 km urban mission time | 4.9 min | 3.3 min | 2.8 min |

7 km urban mission energy | 3.0 kWh | 7.1 kWh | 5.7 kWh |

30 km extra-urban mission time | 18.7 min | 10.9 min | 8.2 min |

30 km extra-urban mission energy | 10.9 kWh | 15.2 kWh | 8.3 kWh |

100 km long-range mission time | - | 34.3 min | 24.9 min |

100 km long-range mission energy | - | 39.7 kWh | 16.1 kWh |

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**MDPI and ACS Style**

Bacchini, A.; Cestino, E.
Electric VTOL Configurations Comparison. *Aerospace* **2019**, *6*, 26.
https://doi.org/10.3390/aerospace6030026

**AMA Style**

Bacchini A, Cestino E.
Electric VTOL Configurations Comparison. *Aerospace*. 2019; 6(3):26.
https://doi.org/10.3390/aerospace6030026

**Chicago/Turabian Style**

Bacchini, Alessandro, and Enrico Cestino.
2019. "Electric VTOL Configurations Comparison" *Aerospace* 6, no. 3: 26.
https://doi.org/10.3390/aerospace6030026