Can a hot air balloonist control the direction they will head, or are they totally at the mercy of the winds?
They can’t do it directly. They basically just can control the ups and downs. However, wind patterns are complex as you move up of down by even 100 feet so there is likely to be wind at a certain altitude that takes you roughly where you want to go.
You go up and down, but not side to side, or back in time.
When the winds are working properly at the balloon fiesta in Albuquerque, there’s something they call the Albuquerque Box. The launch field is down in the Rio Grande valley and a balloon can take off, hit the box and go one way (either north or south), change altitude and go the other way and possibly even land back on the launching field.
Oh, I should add that every morning during the fiesta several balloons are up before dawn testing the winds and reporting the information back to the ground control (they can also be seen from the ground, especially when they hit the burners.) The pilots then know what altitudes to head to depending on where they want to go.
I’m sort of a balloon pilot, so I guess I’m somewhat qualified to answer this. (I’m a student balloon pilot, and I’ll be finishing up my licence this winter, whenever the winds die down and the fields freeze up)
Box winds are quite rare. Albuquerque is a freak location. the closest I’ve seen to a box wind has been some evenings when the wind is pretty much calm (<1 knot) and the only wind is being provided by local cooling… And even then, we still ended up almost half a kilometer away, of course this was in a built up area, and if the launch site would have been 50 metres wider to the south, it could be done.
As far as steering goes, generally, you can get about +/- 5 degrees steerage in the evenings, and anywhere between 5 to sometimes even 90 degrees in the mornings. Mornings generally have better steerage, though mornings with no steerage aren’t uncommon. An evening with a significant amount of steerage is not as common.
I suppose one of these days, I’ll have to start an “Ask the Hot Air Balloonist” thread.
Albuquerque glider pilot, (fixed and flex wing) and sometimes balloon passenger reporting.
When the Albuquerque box is “working” the low level winde are generally southward, and the upper level winds are generally northward. In between is a layer that is fairly stationary.
The following two paragraphs should be considered as “well informed speculation”. It is based on a mental model that provides reliable predictions for local hang glider pilots, and the basis of protest from several local weathermen. Note that weathermen normally care about general weather patterns in a large region, and glider pilots care about detailed patterns in a small regiion (“micro meteoriolgy”):
The Albuquerque box is due to the massive westward facing Sandia crest, and it’sproximity to the Rio Grande Valley. You have a huge mass of granite that is in the shade in the early morning. This rock cools overnight, cooling the air that touches it. There is a downward/westward flow of this cool air in the morning, once the surrounding air becomes a bit warmer. When this flow hits the Rio Grande valley, and converges with the prevailing west (eastward flowing) winds, it turns southward. The shadeing effect of the crest allows this flow to NOT turn southward until it reaches the valley. Because the NorthEast heights are shaded, there is no convection to cause mixing. There is a inversion that isolates the catiabatic flow from the prevailing winds.
As a hang glider-pilot, I can personally atest to the fact that this flow starts just prior (~1/2 hr) to sunset. The low level downward flow from the Crest displaces air on the flats immediatlyhe west of the Crest, causing it to rise. This so called “glass off” results in a huge area of rising air that can make it difficult to get down in a hang-glider.
There is a small amount of incorrect information in a post above. The “dawn patrol” can’t really scout for a box. The box doesn’t “turn on” untill a half-hour or so after the sun rises over the crest. What seperates the two wind directions is a thermal inversion, and some solar heating of the ground is required to lift this shear layer enough that the catabatic flow from the crest can get under it.
Upper level winds, and temperatures can be measured by a raidosonde, so savey weathermen can predict a box prior to dawn fairly reliably.
Upper level winds are a combiniation of general westward flow, and a morning flow that exists to replace the cold air flowing off the mountain.
The “sometimes ballon passenger” part of my qualifications is due to my friendship with a Colorado based ballon pilot. According to him, box conditions are common in the morning in mountain valleys. What makes Albuquerque unique is the relativly open nature of the Rio Grande valley, and the the fact that it has a 5,000 foot high granite sun shade to the East.
Note that the Albuquerae box is not working every morning. The Balloon Fiesta is intentiionally scheduled in the late fall, because that is the season of highest probability.
Answering an implied question in the OP: Exactly where a balloon lands IS largly a matter of chance. Using the winds at varios levels. the pilot CAN exercise some degree of control, but if a favorable wind is not available at practical levels, the pilot must work with what he is given.
In modest winds, a balloon can settle in a fairly small area. Hgher winds require more area, but since the balloon is covering ground faster, suitable landing zones fall under the galloon at about the same rate. With a lot of fuel left the pilot can be fairly choosy about landing zones. As fuel is depleted the pilot will become less choosey.