The canals over Venus

Stationkeeping a SVL2 station takes propellant, on the order of (assuming hydrogen) a few kilograms a year. Meanwhile collecting solar hydrogen anywhere above 60000 km looked to require a net of 17.84 km radius. I don't just want hydrogen; I should be collecting other volatiles, particularly oxygen. I'd love to have an ice shield eventually. Let's irrigate the higher orbits.

At the lowest orbit, above the true atmosphere, there's an exosphere basically behaving like an ionic ocean. It's long been calculated that Venus is "losing water". In practice most oxygen ions stay below 5000 km even in Lundin et al.'s "Noon-Midnight" tail, circling back to the sunny side where, I suspect, they meet up with solar protons.

I propose satellite-pairs in this exosphere. One is ionised positive; one, negative. The positive cathode-sat will catch oxygen and expel hydrogen; the anode, the opposite. The sats orbit the equator so inclination relative to the sun will change per cycle, but never more than 10 degrees off, so that's not the focus of my station-keeping.

For maybe a sixth of that time, 30 degrees on either side of Venus' core-L2 axis, I want to funnel ions upward at escape velocity. Bit higher on the edges. Sure there's some integration function with a cosine for the total.

My focus is the Noon-Midnight charts. To do all their deeds, sats take solar energy, maybe beamed down from L2.

The O^-- ions (Lundin has this wrongly as O⁺) are already going at 4 km/s at 400 km altitude, meeting up with the escape velocity (there 9 km/s) at the 700s-800s km. At this band for oxygen ions, delta-V requirements are less altering speed and more focusing direction. These upper ions are, however, less numerically dense, at 80 ions "per cubic centimeter" (cm^-3). At 400 km they're 200 cm^-3. Just beam more energy down there.

The hydrogen sats are less vital but I'm happy being greedy. The protons are all faster than escape; my foremost aim is to redirect them, and hope I don't need to slow them. Density up to 2000 km is fairly constant at 10-10.5 cm^-3. The protons are slowest at ~10 km/s in the lower, 400s km tiers swiftly rising to 20 km/s at 1000 km. (The ions meet escape again at 4000 km, but there they're not dense enough to be worth the hassle.)

So 400 km is my sweet spot. By Kepler's third, sidereal period is Math.Sqrt(Math.Pow(6450,3.0) * 1.071087763975663E-14), for 77 minutes which is a very small part of even Venus' short year. Synodic, which is relative to SVL2 (that is, to the sun), won't be so much more. I can round that up to 80 minutes.

Either way by moving ions up, their funnel pushes itself down onto Venus over 1/6 = 13 of those minutes. So I must spend the next 67 minutes pushing that back up to orbit. Maybe with the Greason q-drive? The wrinkle down here is that the exosphere got ions of both charge, so Greason is a magnet for whatever I'm not pushing against. Oxygen is thickest so I expect the magnet's negative side facing down.

One option is to spend maybe 67 minutes scooping ions (much of it Dawn/Dusk), then shoot 'em all up with a standard ion drive (9 km/s won't need Alfvén but, yes, That Jerk will get a veto). This one will shift from being a cathode or an anode as needed. Another option is to rotate that magnetic drive and just kick whatever ions I come across. Could be I can use both. I will say: the former looks more efficient, the latter seems more simple. Although for the latter, I imagine I'll need to shake the wrong ions from my electrode after I've boosted the right ions.

One kilometer being 100,000 cm, every cubic km at 400 km altitude has 2E+17 ions of oxygen (3.32E-7 mol, 5.312 μg), and 1E+16 H⁺ (1.66E-9 mol which is grams). If my net is sweeping 6754 km for a sixth of orbital circumference, a square kilometer of that net should cover 6754 km³ of volume, thereabout: 35.9 mg and 0.0112 mg respectively. Ten times the width is a hundred times the area so volume of the tube it sweeps, every 80 minutes. Yaddayadda grams O^-- (and less-than-that grams H⁺) every Earth day does get a kilo of oxygen after a few weeks, much less than 146 days anyway. I consider my sanity, checked.

With angle and focus, I hope to pitch both oxygen and additional, slow-moving hydrogen to whatever nets can catch it. If the net catches both, they can use the reaction to make ice and also its own energy, which is not naturally had in umbra.

Ideally I'd have a cloud of ice in umbra which any satellite orbiting 530000 km on down can capture as needed. The remainder ions need to carry on up to L2. More realistically I expect I'll be feeding most of this oxygen to low-orbiting satellites which use it mainly for their own propellant needs, as they swing tethers around to boost shuttles up and down.