#ScienceFiction


OG toot by sundogplanets@mastodon.social

Some food for thought (and beautiful images of Mars), although I think the technical feasibility will make a big jump if SpaceX's Starship will successfully launch this year. Ultimately I agree that it makes little sense to send humans to space for research purposes. However, what might make sense is to do robotic resource extraction in the asteroid belt. Mars is kind of a natural stop on the way there AFAIK. If that turns out to be feasible, there will be probably some human piggy-backing on these robotic shuttles. I would guess we will see some elderly and relatively rich people drive this human exploration as some sort of extreme sport (due to low gravity it is doable by elderly persons) with no real expectation to come away unharmed (or necessarily return at all). But over time this will build up sufficient experience and infrastructure to make a Martian colony feasible and since the robotic shuttles going to the asteroid belt will be mostly empty on the way there, getting supplies to this Mars colony will be relatively cheap.

A neat (and presumably pretty old by the site design) article about how long satellites will last in Low Earth Orbits with varying eccentricity and perigees alongside satellites with different amounts of drag, alongside explaining the various forces that cause this orbital decay. It also highlights how setting the lower boundary of space at ~100 kms is, while not an entirely arbitrary decision with stuff like the Karman Line, where a plane would need to travel at orbital speed to achieve lift, is fairly deceptive for actual satellites, which according to the article won't last more than a few weeks below 250 kms. Wikipedia cites an estimate that Sputnik which orbited Earth at an orbit with a 215 km perigee and a 939 km apogee lasted 2 months in orbit. There are also charts of orbital decay for the ISS ([Graph 1](https://i.stack.imgur.com/0nNSt.png), [Graph 2](https://i.stack.imgur.com/f8p3G.png)) and of Tiangong-1 ([Graph 1, specific dates](https://ars.els-cdn.com/content/image/1-s2.0-S246889671930120X-gr4.jpg), [Graph 2, Apogee and Perigee](https://ars.els-cdn.com/content/image/1-s2.0-S246889671930120X-gr3.jpg)) >The following table provides a very rough guide to the lifetime of an object in a circular or near circular orbit at various altitudes. >| Satellite Altitude | Lifetime | >|:----|----:| >| 200 km | 1 day | >| 300 km | 1 month | >| 400 km | 1 year | >| 500 km | 10 years | >| 700 km | 100 years | >| 900 km | 1000 years |

Never gets old. - Here comes Jupiter! NASA's robotic spacecraft Juno is continuing on its highly-elongated orbits around our Solar System's largest planet. The featured video is from perijove 11 in early 2018, the eleventh time Juno has passed near Jupiter since it arrived in mid-2016.