2
$\begingroup$

According to the specifications, this quad-copter offers a 90-minute flight time on a 14S-14000mah Li-ion battery.

The propellers being used have a 22-inch diameter and have 8-inch blades and the Maximum Take-off Mass is 8.

Is it possible for such a quadrotor to have a such a high endurance? If so, could you please explain how?

$\endgroup$
2
  • 5
    $\begingroup$ Probably better on Drones SE but just look at it from an energy perspective. How much energy does it take to fly 8kg around for ninety minutes? $\endgroup$
    – Jim
    Commented Sep 14, 2022 at 5:15
  • $\begingroup$ It only boasts the 90 minutes at empty weight, or 45 minutes at 7.9kg. But I agree, this isn't an aviation question and is more suited for a drone SE or a battery SE. $\endgroup$
    – Max
    Commented Sep 14, 2022 at 5:22

1 Answer 1

5
$\begingroup$

As usual, the simple momentum theory is our friend in these cases:

$P=\sqrt{\frac{T^3}{2 \rho A}}$

Considering that in hover each rotor lifts ¼ of the total weight $W$ and that we have 4 rotors, the needed power becomes:

$P=4\sqrt{\frac{(¼W)^3}{2 \rho A}}$

where:

  • $W=8\cdot9.81=78.5~\mathrm N$
  • $\rho=1.125~\mathrm{kg}/\mathrm m^3$
  • $A=\pi(22\cdot0.0254)^2=0.98~\mathrm m^2$

Substituting the values we get a total power of:

$P=234~\mathrm W$

According to the source, the electrical engines work at a voltage $V=50.4~\mathrm V$. The power of an electrical machine is $P= V\cdot I$, which translates into a current of:

$I=P/V=234/50.4=4.6~\mathrm A$

The battery has a capacity $C=14~\mathrm{Ah}$ and delivering that current it drains after a time of:

$C/I=14/4.6=3~\mathrm h$

This is obviously a maximum theoretical value that does not take into account many factors like:

  • electrical engines are not 100% efficient;
  • some electrical power is used by the onboard electronics;
  • batteries are normally not made deplete completely;
  • for manoeuvring, more thrust and therefore more power is needed than for hovering; but less power is needed in forward flight;
  • simple momentum theory underestimates the needed power of some 15% in hover; and at the typical Reynolds number of drones the efficiency is worse; I'd say that the underprediction might be some 25%.

Factoring in all these points, the given endurance might be plausible.

$\endgroup$
0

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.