The experiment will eject at least 800 g of copper particles. Hopefully more! The more particles the stronger back scatter of the radar signals and bigger chance of a successful experiment. But on the other hand, copper isn’t very healthy. It is toxic to both nature and humans in too high levels. So where will the particles fall down? Will there be a risk for the SCRAP team at the rocket launch pad at Esrange?
To know this we do what we do all the time. We guess. But not just any guess. We go to the books to find models that fits to our situation and do calculations. Sometimes there are so many models that it is hard to know which one to use. This is the case when calculating how fast small particles fall when the density of the atmosphere is ridiculously small.
So, will we use protective masks after launching the rocket to avoid the rain of copper particles? No, we will not. At 80 km where the atmosphere is very thin the particles will fall around 20 m/s (72 km/h), quite fast! BUT! As the density of the atmosphere increases at lower altitudes the velocity decreases. Near the ground the velocity will be 0,3 mm/s (0,0009 km/h). The last 1000 meter will take 1100 hours! 47 days! It might take several years before the particles touch the ground again!
So where will the particles land? We have no idea! We only know that the particles will travel a long way and spread out before they settle. Some may go to Japan, some may go to USA. Others might go to Brazil or Tajikistan. Maybe some of them will travel a few laps around the earth and then go back to Sweden.
How about the environmental issue? If copper can be toxic. Why spread it in the atmosphere? Well, actually mankind emits quite much copper already. For example, according to “TNO Built Environment and Geosciences, Environment, Health and Safety” in The Netherlands, the copper that is emitted only from cars that wear out the breaking disks is around 2400 ton every year only in Europe. Since we will use a very small amount compared to what is emitted every year the impact from our experiment will be very small and it is worth it to know more about how our atmosphere works.