Jean-Pierre Blanchard Lunardi flew from Moorfields to Ware on 15 September 1784. Blanchard's propulsion mechanisms – flapping wings and a windmill – again proved ineffective, but the balloon flew some 115 km from the military academy in Chelsea, landing in Sunbury and then taking off again to end in Romsey. Blanchard took a second flight on 30 November 1784, taking off with an American, Dr John Jeffries, from the Rhedarium behind Green Street Mayfair, London to Ingress in Kent. A third flight, again with Jeffries, was the first flight over the English Channel, taking about 2½ hours to travel from England to
Hot air balloon course) stated in the previous section. Liftoff would require a slightly greater temperature, depending on the desired rate of climb. In reality, the air contained in the envelope is not all the same temperature, as the accompanying thermal image shows, and so these calculations are based on averages. For typical atmospheric conditions (20 °C, 68 °F), a hot air balloon heated to (99 °C, 210 °F) requires about 3.91 m³ of envelope volume to lift 1 kilogram (62.5 ft³/lb). The precise amount of lift provided depends not only upon the internal temperature mentioned above, but the external temperature, altitude above