Lately I've been interested in comparing the energy density of model rocket engines to lithium polymer batteries (attached to motors and propellers) for propelling things upwards.
To get a feel for this, I decided to compare an Estes C6-5 motor to a 3DR Iris + quadcopter.
Estes C6-5 has initial mass of 25.8g, and produces 10 N s total impulse. So, the "Impulse density" is about 10 N s / 25.8g = 0.38 N s g^-1.
3DR Iris+ weighs 1282g without battery. 3.5ah battery weighs 250g and will power hover for about 20 minutes (so about 10.5a draw). Thrust produced to hover on Earth is 9.8N kg^-1 * 1.532 kg = 14.7N. "Impulse density" is 14.7N * 1200s / 250g = 70.6 N s g^-1 .
So, according to my math here, the LiPo is about 0.38/70.6 = 186 times more energy dense than the model rocket engine.
Of course, the model rocket engine will lose 12.48g of propellant by the end of the flight so it will be effectively a little lighter, but that's not going to affect things by a factor of 100.
Does this seem right to you? Am I missing anything?