Hydrogen for SVL2

Since everyone else is doin' it I am reading Lundin, R., Barabash, S., Futaana, Y., Sauvaud, J.-A., Fedorov, A., & Perez-de-Tejada, H. "Ion flow and momentum transfer in the Venus plasma environment", Icarus 215.2 (2011), 751-8. Their data are from the ASPERA-4 Ion Mass Analyzer (IMA) on Venus Express.

The orbiting probes, orbiting, couldn't touch L2 and didn't often rise above 20000 km altitude. But I do see a pattern. We need two charts for this.

To get the look of it side-on is the Dawn/Dusk meridian, along the plane of ecliptic. Above about 900 km, Venerean hydrogen ions (protons) lose out to those from the Sun. Above 4000 km, solar ions reach a standard. For speed, that's 200 km/s. Density also dips, until maybe 12000 km, after which it rises again and by 20000 km runs a range 1-5 cm^-3. By that orbit of course v_esc is like 1 km/s, so those ions ain't comin' back. We also get a chart for mass flux, following the density chart: 2E-15 kgm^-2s and at 20000 km, dropping to 1E-15. The side-on Induced Magnetosphere Boundary is slightly above a thousand km.

From SVL2 we're looking down at the Noon/Midnight axis which runs from the Sun. Velocity's about the same, at 20000 km. Here I'm most intrigued by the mass flux. Solar protons reach about 1.5E-15 kgm^-2s at 10000 km, before dropping to that 1E-15 range. IMB is in this backflow more like nine thousand km, and elsewhere I hear of a magnetotail 60000 km.

I see these 200 km/s speeds as streaming pretty directly back. There will be some scatter, but I do not think very much scatter, above the tail 60000 km.

E-15 kgm^-2s will be E-12 gm^-2s, and with a square net of a kilometer to a side that should be up to a millionth of a gram, per second. A good kilo-square statite in umbra 600000 km altitude should be hit by 86.4 milligrams of [200 km/s] solar proton per Earth day. At a 17.84 km radius, 86.4 grams. A kilo per fortnight.

Down here the longer something collects mass the more it comes under Venus' pull, so at some point I'll pull on my 1000 square kilometer of sheet for my kilo of hydrogen. My notion: funnel the hydrogen into a central nozzle and squirt it all on up, toward SVL2, which has its own net. I don't need superconductors, I should be beaming my energy from SVL2 halo.

Anyway this is enough to feed hydrogen to the station on its Ebrahimi-Alfvén, over a 146-day "season", with kilos to spare.

For peak oxygen we'll need a true orbit at a low km altitude. How we make up the 9 km/s delta-V to SVL2, I remain unsure. I still wonder if the teslas and ions down there give enough thrust to make that q-drive worth our while. Maybe firehose these ions on a tight beam upward.