The 89 kilotonne dumbbell

I finally got some time to read Pekka Janhunen's shielded dumbbell colony proposal. This is suggested for "L5", meaning Terra-Luna Trailing Libration Halo. (Janhunen said "point" but a halo is not a point.)

For two hundred inhabitants, which I take as a maximum, Janhunen proposes target mass 89000 tonnes (= megagrams), 89 gigagrams. This is over two hundred times / tenscore ISS at 419.7 Mg. Janhunen is hoping if LEO launch costs drop below ~ $300/kg. Falcon 9 is $3000 but Starship is looking at $30.

Mostly the worry is radiation and, in Earth's orbit on out, the worst radiation is cosmic. As we get nigh to the Sun I think solar takes a higher share, especially during flares.

Something like this dumbbell - or several such somethings - could also be at STL4 and STL5 because halo, and wider halo at that. Such would have to await a larger human presence off the Earth's well; we start close to home.

DEIMOS LIBRATION 6/26/22: My last para here is now its own post. PURPOSE 8/18-19/23: I've moved another para on what this thing is for, here: it's a shuttle. For asteroidal work, see Jensen.

UPDATES 8/19/23: Janhunen doesn't actually need the iron he's hoping for, if anhydrous glass will do it. For outside-shielding, aluminium might block radiation. And his greenhouse-between-weights is less-efficient than acetate in the dark although, it may be that he's simply run out of room. He might be able to grow these in any gravity.