Our aim is to fly at higher altitudes than Solar Impulse/SkyDweller, which keeps us above the turbulent winds and cloud cover of the troposphere, and makes long endurance flight more reliable/less weather dependent. Our platform is also a lot smaller than SkyDweller, which helps keep costs much lower and opens some interesting new opportunities - for example, deploying lots of aircraft in a mesh network.
The Solar Impulse/SkyDweller lineage is very inspiring - what an amazing way to demonstrate how much you can do with solar power!
In practice, considerable difficulty. Like you said LEO moves fast. You are talking 10 min in line of sight (LOS) depending on the orbit. So the handoff algorithms (and necessary network) are very challenging and cost prohibitive. I mention it in my earlier response but if you have a LEO network you need pretty substantial arrays to accommodate such a power load, and during “night” for whoever is using the network, you need transfer mechanisms to relay the data, using even more power during eclipse. This is a real challenge.
Lasercom has been demonstrated well on Earth but it still is a very nascent technology in the space domain. There are several challenges that lasercom faces.
First, in order to enable global communication you need a constellation and good constellation management. This requires fewer spacecraft if you are in GEO, but GEO spacecraft tend to be larger and more expensive.
Second, lasers draw a lot of power. Most is waste heat as far as the spacecraft is concerned, but this can become a problem if the duty cycle is high. High power means much larger arrays, and for a LEO constellation, serious eclipse challenges.
Finally and most importantly, pointing is a challenge. Maintaining pointing control in space is hard, and lasers require much greater accuracy as compared to RF. With RF, the lobes are relatively large and allow some play when it comes to downlink to ground. Lasers are unforgiving.
I’ve led several spacecraft missions with lasercom terminals, and every time it has made development markedly more challenging. I think it will be quite a while before it is mainstream, and certainly before it replaces fiber.
ISLs are active today, providing low-latency broadband to thousands, perhaps tens of thousands of Starlink's 1.7-ish million customers where there are no nearby ground stations. I'm not sure if that's "mainstream" but when major cruise lines and Alaskans are happy active customers, it feels like it's getting mainstream to me.
