SA P C E VS E A R T H rest is heavier ions of elements such as nitrogen, carbon, neon, and so on. Along with the HF and SatNav issues already mentioned, this radiation (plus UV, which is nonionising) can present health concerns for folk flying at high latitudes. On average, a flight crew is thought to get a radiation dose of around 2.19mSv every year. London to New York, as an example, is considered to deliver around 0.51mSv per 100 block hours. These figures, however, are based on older research, from the 1990s. Now that we fly at higher altitudes, the doses are likely to be more: estimated at an average of 5mSv on more exposed routes. The recommended maximum radiation dose per year is 20mSv, averaged over five years. If you fly a lot of polar and high-latitude flights, your operator should, hopefully, be monitoring this. There are simple precautions you can take yourself. UV-protecting sunglasses are critical for pilots, for whom the rate of macular hole degeneration is high. A 2014 study of Korean pilots showed the prevalence to be almost double that of the general population. Sunscreen is also a good call. Flying for an hour at 30,000 feet can zap you with as much UV radiation as 20 minutes on a sunbed and this can be 85 per cent higher if youre flying over thick cloud layers where UV is getting reflected back at you for a second dosing. Our recommendation: if you dont want to get leathery, or worse, skin cancer, slap on that sunblock. At this point, its worth pausing to think about an Earth-based source of radiation to which commercial pilots are exposed. Airport scanners can hit you with a dose of non-ionising radiation approximately 100,000 times less than the average annual dose we pick up from natural background radiation the equivalent of about two minutes in-flight radiation exposure. However, this is around the 0.03-0.1mSv mark, and is similar to a medical X-ray machine, only way less powerful. Its not really a concern. And those bananas you eat on board? They contain around 0.5g of potassium, a very small amount of which is the naturally occurring radioactive isotope potassium-40. This emits ionising radiation, so every time you eat one youre gulping up the equivalent of 1,000th of a check X-ray. Again, its nothing to worry about. Out of this world At any given moment, there are around 9,000 aircraft circling Earth. Thats about 1.27 million people zooming about the skies. It is busy up there. Which is why the emergence of more space-based traffic is starting to cause conflict for us. The number of launches every year was fairly steady, and below 100, until 2018, when excuse the pun it rocketed. Currently, across the USA, there are around 20 licensed space ports, 14 managed through the FAA and often close to airports and airways. Globally, there were just less than 200 such facilities in 2023, the majority being medium-lift rockets. In 2018, the launch of SpaceXs Falcon Heavy resulted in the closure of 1,300 miles of airspace east of Florida, over the Atlantic, for three hours. Changes in routings led to massive cumulative delays and extra miles. The FAA estimated that, in 2018, around 1,400 flights were affected by spacecraft, resulting in an additional 70,000 miles flown. Space-traffic management is a real thing, and you can read some of the regulations applied to the North Atlantic region in NAT Doc 013 Operational Guidance for Commercial Space Operations. There is also work going on to improve launchwindow estimates and required airspace closures. Currently, the FAA closes much more airspace than it really needs to, and for much longer than it needs to, because launch windows can be so wide and there are limited ways to track inbound stuff, such as spent boosters and rocket stages, accurately. Around and inbound The path for debris heading inbound (falling back to Earth) tends to be input manually, and decisions are made by actual people. The impact it can cause is significant. The debris from Space Shuttle Columbia in 2003 littered across east Texas and into Louisiana; had it broken up earlier, it would have impacted Dallas, and to a much more severe degree. In 2022, the core stage of a Chinese Long March 5B rocket reentered the atmosphere uncontrolled, with a potential for impacting anywhere below the 41 latitude line. This resulted in NOTAMs from Spain, France and Corsica, closing chunks of their airspace and affecting 875 flights, with an aggregate ATFM delay of around 309 hours. On top of all this, orbital space is getting busier. While we dont fly up there, it can still have a fairly direct impact literally. In 2009, the 66 Iridium satellites were happily orbiting 48 THE LOG Spring 25 pp46-49 Space v Earth.indd 48 17/03/2025 14:26