OK I'll start.
There's a rhythm to it, if you watch closely. Its not like the flashes come evenly spaced - after the first blue flash, there's a minute of stillness, and then two more come rapidly, and then three more, then five, before it falls back to a slower pace.
Leon knew it would be another ten minutes before the payload reached its first unstable low orbit, but he'd never seen that stage. That would happen a continent away, and a mile high. Several miles below, for him.
A few other people also watched at port windows. More people rushed past, wearing their bright orange reflective work suits, helmets tucked under an arm or slung over shoulders. They made their daily pilgrimage to the zero gee welding gantry, hanging miles over the earth, while gabbing about some workplace drama, no doubt. "Yeah, but Clara said she saw him there," Leon heard someone say.
Sighing, he got up and grabbed his bag from the floor. He had ten minutes to get his butt in his seat on the transport outta here. He paused at a big clear LCD screen, which displayed arrival and departure times and flicked to the next set of times a little too fast for comfortable reading. But there - yep, gate 5, and a little less than ten minutes now.
He started to turn away, but then saw a big smile on the other side of the screen. Sophie? What's she doing here? She was coming around to this side of the display now.
"I hoped I'd catch you before you left." She was bouncing up and down.
"What are -"
She interrupted : "Change of plans. We need you out at the yard. You have visitors." She grinned in a highly suspicious way. But damn, she's infectious. Leon could help but smile, looking at her, although he had every reason not to be smiling now. And now she was grabbing his hand and pulling him down the walkway.
But at the gate - not gate 5 - she turned and told him that she had to get back to the office. And off she went. Leon entered, walked down the ramp, and took a seat. This was not a regular passenger shuttle. He had it all to himself.
"Lucky me," he thought. There's a view straight down to the earth. Below, he could see the area where he'd been watching those blue flashes. A large section of the ocean in that area was covered by what looked like patterned lilly pads. In their center was a city - if you can call such structures cities. Its a key part in the supply chain that he was involved in, producing methane gas from halotrophic algae. That methane is then used as an energy source for both ground based living and the production of rocket fuel. Not the fuel his current ride was using - this uses a fission spinner drive, which is more suited to space only flight - but the fuel for the thousands of tube rockets launching every day. Those more traditional rockets were still the most cost effective way to escape the atmosphere and the highest burden of gravity.
But those blue flashes weren't that. That was something new, and it was very interesting to Leon that the seasteads were leading in that technology, despite methane being their main export. The flashes would be much more visible from the ground. He was only seeing a scattering of the light off the atmosphere. They were high energy lasers zapping gigawatts into the underside of an upside down cup. A literal flying saucer. The popping is from the atmosphere under the cup suddenly expanding from the heat ; the space between the pops was for cooler air to refill the cavity, and then it gets zapped again. They're not sending humans up that way - that was cargo. And it must've been high priority cargo, too. Leon wondered...
(Alright, take it away, whatever strikes your fancy)