A balloon's only means of propulsion is the wind. Balloonists can change their course by changing altitude, and catching winds going different directions.
Straight gas balloons change altitude by dropping sand or or water to go up, or venting helium to go down. This is what provides the challenge and adventure of long distance ballooning.
The key is to find a meteorologist that can forecast the winds accurately, making sure the balloon stays on course to the goal.
Luc is undeniably the world’s premier meteorologist for long distance and duration balloon flights. His record is unparalleled in guiding balloons through complex weather patterns to a successful conclusion. He was the meteorologist for both Bertrand Piccard and Brian Jones on the first Around-The-World Roziere balloon flight, and Steve Fossett’s solo Around-The-World balloon flight. He has also provided the meteorological support for numerous Gordon Bennett winners. Proper weather forecasting is the key on our attempt, and Luc is the best in the world at it.
"The goal is to find a weather window that will move eastwards from East Asia to North America. Such a window must be found between two frontal systems associated with low pressures (depressions) which will move under the polar and/or the tropical jetstream(s) over the Northern Pacific. One of the main problems will be to fly the balloon not too fast or too slow between the bad weather features to avoid the turbulent and humid conditions associated with the fronts. If 7 to 12 knots are acceptable wind speeds during the take-off and the landing of the balloon, there are no limits when the balloon is at altitude and speeds of more than 100 knots could be reached under the jetstreams."