Flight report
Back on the ground. The whole climb as charts and numbers, what was simplified, and where the numbers come from. Return to the launch field.
Where the air is
The first 100 km, drawn to scale. Each numbered block holds the share of all the air, by weight, listed under it. Half of it is in the first block.
And the whole flight to scale: 10,000 km. The first 100 km is the dark sliver at the left.
The zig-zag
Temperature against height, from the 1976 standard atmosphere: the line the red pen drew. It turns three times, and each turn is the edge of a layer.
The colour of the sky
Worked out by the same sum that draws the picture, for the daytime Sun. Brightness is compared with the sky straight overhead at the ground.
Storms to scale
The storms of the Weather switch, as they are built for this flight. They differ a great deal in width and hardly at all in height: every one of them stops at the same lid.
Numbers on the way up
What is simplified
- The air is the 1976 US Standard Atmosphere, a yearly average for the middle latitudes. Real air changes with place, season and hour. The tables stop at 1,000 km, so the gauges do too.
- The sky counts light that scattered once. Real skylight has often bounced several times, which makes the true sky a little brighter and paler, most of all near the horizon and at dusk. Haze is one thin, clean layer.
- By day the exposure is fixed up to 40 km, so the darkening you see is real. Above that, once the sky is black, it is stopped down so the sunlit Earth is not washed out. The ground and clouds are also dimmed to balance a sky that, with single scattering, comes out darker than the real one. At dusk and at night it is opened up, as your eyes would do, and stars are drawn as soon as the sky is dark enough. In daylight the bright Earth would dazzle you and you would see few or none.
- The land is NASA's Blue Marble picture, blurred by being stretched. The clouds and the fine detail are made up. One flat cloud deck stands in for ordinary weather.
- The storms are built shapes, not simulations. Each has the size and height of a typical one and stands where one could: the thunderstorm, the supercell and the dust wall on the plains north of Roswell, the hurricane over the Gulf of Mexico. They are lit by the same sum as the sky, but they stand still, cast no shadow on the ground, and have no rain, hail or wind. The dust is a solid wall: the air around it stays clear. Nobody would launch a balloon next to any of them.
- The lights are three fixed Suns, not real dates or hours. Night is a strong-storm night like 10 May 2024, with the aurora ring pushed much further south than usual. Noctilucent clouds are placed further south than they normally form.
- Sprites and meteors are slowed down so you can see them, and they come far more often than in life. So does the lightning.
- The balloon is drawn at the size the gas law gives (it ignores the squeeze of the rubber), from 1.8 m at launch. The balloon and the rocket are drawn much nearer than their true distance would allow.
- The rocket is a story device. Real sounding rockets start from the ground, and none flies to 10,000 km. Its drawing does not turn with the view.
- The paper feed is not steady. The strip chart is stretched where there is more to say, so read heights off its ruled lines, not off distances. The read-out's thermosphere temperature is one average; the true value swings with the Sun from about 500 to 2,000 °C.
- "Breaths needed" compares density only. Above about 100 km the mix of gases changes too.