QotW: Satellites in space

Phil Sansom has been getting stuck in to this question...

Pete - SpaceX has launched the first 60 of what is to be a mesh of some 12,000 satellites. Two questions: how will this completed mesh impact ground based optical and microwave astronomical observations, and secondly the ability of future space missions, manned and otherwise, to navigate through this cloud of objects?

Phil -  It’s rare to get no responses on the forum, but this is a complicated question. SpaceX’s 12,000 satellites is over double the number up there right now. For ground-based astronomy, UCL’s Ingo Waldmann says low-orbit satellites like this aren’t that big a deal.

Ingo - For most applications they are not a major concern as they will only impact small parts of the telescope’s view of the sky. And low-orbiting satellites are naturally fast-moving, so likely won’t contaminate more than one image. Most small satellites will not be visible to most observations as the light they reflect is small, and the effect on the observations is likely smaller than the variability due to the Earth’s variable atmosphere.

Phil - But looking through the satellite mesh is one thing - moving through it is another.

Ingo - Regarding navigating through this mesh of satellites, well, we have millions of high-velocity pieces of debris in low and intermediate orbits. Navigating around the most dangerous pieces is extremely difficult and risky. What’s important to bear in mind is that we know exactly where these satellites are, and that despite their numbers they remain very far apart. What will be interesting to see is how we will prevent what’s often referred to as the Kessler syndrome, a scenario where debris of one shattered satellite takes out other satellites in a gigantic domino effect across the sky.

Phil - Kind of scary - how do you avoid that? Holger Krag works on space debris at the European Space Agency, and he has got some tips.

Holger - They need to avoid break-ups, and that is done by depleting the tanks after the end of the mission. But they would also need to dispose the whole spacecraft into low orbits, such that they trigger a fast re-entry into the atmosphere and disappear from space. And if this is systematically done, even many spacecraft would not necessarily mean a big problem. Large constellation would have to implement this extremely strictly, and better than the past spaceflight did.

Phil - Thanks both. I also reached out to SpaceX for comment but no response, so we’ll have to wait and see. Next week’s question, meanwhile, is from Dan.

Dan - I watched a survival show where the host caught a skunk, cooked it, and ate it - but said it was awful. It got me wondering: are most animals edible? We hear about not eating wild mushrooms or puffer fish, but seems like almost everything is edible at some point. Does evolution play a role? And taking that to an extreme, what are the odds that dinosaurs were actually edible?