A usual explanation is the representation of some type of vegetation (in Christian culture a fig or something related is often mentioned but I've read about other plants, leaves and seeds in different cultures with different cultural connotations). The ass is probably a reverse interpretation somewhat like the heart… » 7/24/14 2:58pm Today 2:58pm

I did know. Well, the problem about high-energy, low-thrust propulsion isn't that they don't work in orbital transfer and extraorbital flight, trouble is they won't get off the ground. So you still need the thrust to take off and to leave the atmosphere, that's when low acceleration starts to work. » 7/20/14 11:59am Sunday 11:59am