by RegGuheert (Posted Tue, 06 Feb 2018 04:58:49 GMT+7)
- The Solar Impulse 2 was solar-powered which has a very low airspeed and did not have sufficient energy storage in the battery to fly through a 12-hour night at the equator at a constant altitude. So how did it manage to fly halfway across the Pacific Ocean, then? They did two things that made that flight possible: 1) They stored some of the energy needed for flying overnight as potential energy rather than in the batteries, and 2) They flew from West to East, thus shortening the duration of nighttime by about 25 minutes. Part of this shortening was the direct result of the tailwinds that occur when traveling in that direction and part of it was due to the direction of rotation of the Earth. While 1) could be done anywhere, 2) required flying about 65 degrees around the globe in the direction from West to East over five or more 24-hour days.
As such, flying "out and back over the ocean" likely would have simply been impossible because of these constraints. Imagine flying "out""over the ocean" in an easterly direction through an entire night. How would you get "back"? First of all, flying in a westerly direction is not even possible above a certain windspeed. And unless the windspeed is less than 1/3 of the airspeed of the Solar Impulse 2, then it will not be possible to get back to land before the next night. Perhaps very still conditions exist sometimes around the solstice in the equatorial Pacific or Atlantic, but it is likely rare given that is when the sun has the most impact on winds over the equator.
- Flying over land provides a strong incentive to abort while flying over water provides a strong incentive to press on. Sure, they possibly could have tried to fly for five days in an easterly direction over Asia, but, guess what?, they likely would have aborted as soon as there was the problem occurred. Why? Because it is so easy to do. And if that problem hadn't aborted the flight something else likely would have. There is nothing like the INABILITY to abort that keeps long-duration missions going.
- Finally, no amount of collecting flight data would have solved the biggest problem that they faced on that leg of the trip: the inability to predict the weather five days in advance. Only by having a plane with a higher windspeed could they have resolved that problem. That could push such a flight a decade or more into the future. Simply put, the weather is one risk which simply could not be retired for that leg of the flight.
In the end, they did the best thing they could have done: they pressed on and achieved what the the Solar Impulse 2 was designed to accomplish.
Sure, "data" could have been collected in that way, it just would not have been useful to improve the chances of a success over that leg of the flight. Here's why:GRA wrote:RegGuheert wrote:As far as collecting data goes, the data which was yet to be collected was the data which could ONLY be gathered on this leg of the mission. They needed to find out if the plane could store enough potential and battery energy to make it through the night over the Pacific, and to do this over and over again each day for five days. They also needed to find out if Pierre could manage to fly the plane for five days. The ONLY way to collect that data was to actually DO it. It turned out that Pierre WAS able to succeed even with an additional hurdle put in his way. OTOH, it also turned out that the thermal design of the batteries was insufficient for the purpose.
Data could just have easily been collected flying over land, or out and back over the ocean.
- The Solar Impulse 2 was solar-powered which has a very low airspeed and did not have sufficient energy storage in the battery to fly through a 12-hour night at the equator at a constant altitude. So how did it manage to fly halfway across the Pacific Ocean, then? They did two things that made that flight possible: 1) They stored some of the energy needed for flying overnight as potential energy rather than in the batteries, and 2) They flew from West to East, thus shortening the duration of nighttime by about 25 minutes. Part of this shortening was the direct result of the tailwinds that occur when traveling in that direction and part of it was due to the direction of rotation of the Earth. While 1) could be done anywhere, 2) required flying about 65 degrees around the globe in the direction from West to East over five or more 24-hour days.
As such, flying "out and back over the ocean" likely would have simply been impossible because of these constraints. Imagine flying "out""over the ocean" in an easterly direction through an entire night. How would you get "back"? First of all, flying in a westerly direction is not even possible above a certain windspeed. And unless the windspeed is less than 1/3 of the airspeed of the Solar Impulse 2, then it will not be possible to get back to land before the next night. Perhaps very still conditions exist sometimes around the solstice in the equatorial Pacific or Atlantic, but it is likely rare given that is when the sun has the most impact on winds over the equator.
- Flying over land provides a strong incentive to abort while flying over water provides a strong incentive to press on. Sure, they possibly could have tried to fly for five days in an easterly direction over Asia, but, guess what?, they likely would have aborted as soon as there was the problem occurred. Why? Because it is so easy to do. And if that problem hadn't aborted the flight something else likely would have. There is nothing like the INABILITY to abort that keeps long-duration missions going.
- Finally, no amount of collecting flight data would have solved the biggest problem that they faced on that leg of the trip: the inability to predict the weather five days in advance. Only by having a plane with a higher windspeed could they have resolved that problem. That could push such a flight a decade or more into the future. Simply put, the weather is one risk which simply could not be retired for that leg of the flight.
In the end, they did the best thing they could have done: they pressed on and achieved what the the Solar Impulse 2 was designed to accomplish.