When I was looking at Venus floaters and airships six years ago, I was unaware that the professionals had already been at it. The most prominent 2000s-era pro was Geoff Landis; in 2004 he got Tony Colozza on the case.
As of then Colozza knew that at the 53-5 km tier, temperatures and air-pressures reach Earth life standards. At 55 km, 302.3 K = 29.3° C and we're well above the clouds. That pressure happens to be 0.5314 bar, so he's not really talking about humans. (Yeah I know, just use 40% O2 bro; let's hold off on all that today.) Colozza is pondering if unmanned aircraft can be kept in eternal daylight up there. The mission is for 50 days consecutive. Earth-sent probes.
I had trouble understanding Colozza's conclusion in part due, unfortunately, to typographic mistakes (see below). So I'll do my best.
The main body recommended the perma-airship for altitudes below 10 km. This is also not near the clouds. It is however hell down there. Moreover, much of the incoming light is blocked. Solar panels, in his day, degraded in high temperatures and pressures, and were only 20% efficient at peak. The paper also thought solar panels were skewed to absorb blue where, for silicon anyway, it's more the opposite.
The other option is a non-airship, more like a Reaper drone. That can fly 71-76 km, for 9-12 m wingspans. There the temperature is around 220 K which is -53° C (the paper lost the minus sign here). It can if needed dip down to lower altitudes as long as it returns. Perovskite is coming on-deck these days; this is rated for 350 K so 50+ km altitude, and could well lower the wingspan.
As far as the purpose of either, that would have to be for mapping the surface and/or surveying the atmosphere across latitudes. Radar for the drone; slow photography for the airship. (If we wanted aloft over a fixed position for 50 days, I'd tether a kite to Maxwell and power it by windmill. But this assumes a space-economy good for shipping dozens-kilometers of thick steel wire to Venus, which we might not yet have.)
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