However, this can be fixed by sterilising the air in the VRS' as they are generated, for instance by UVC LEDs. Is this possible? Even with air rapidly moving past the LEDs? We'd need to try experimentally.
If this begins to sound like requiring unfeasible amounts of power then it is worth remembering that actually, the sample corridor would maybe only need to work for a few seconds - after that the air samples would have been drawn in and be ready for analysis.
VRS is just one idea. Do you have others? Perhaps a "Self Sterilising Mortar Round" (SSMR) as described in my earlier post is better?
Let us not forget the obvious approach - a long pipe to stick out from the gondola. But how to make a Self Sterilising Pipe? (SSP). You can make flat packing or inflatable pipes (that's another blog!) to deploy during flight, but could you do this with the surface studded with UVC LEDs? Wouldn't this get really heavy and full of cabling? Maybe you could illuminate the pipe from the gondola with a very bright fixed UVC source - an LED or laser, sterilising it from a distance. But this might need to be very powerful... perhaps it doesn't have to be a UVC source at all? Coronal discharge is a potent sterilising agent as well (a company called Cerionx was trying this, as I recall). Could we build up a high electrical field on the pipe, just below that that would arc at high altitude? Is this a cool experiment in its own right?
We could perhaps try buying an "Air Bazooka" toy and seeing if the VRS' it generates can actually be sterilised by UVC LEDs. For instance, we could rig such a "Self Sterilising Air Bazooka" (SSAB - I feel like making acronymns tonight!) And then fire it continuously onto an agar plate with the LEDs turned either on or off. If you see a circle of fewer bacterial colonies where the VRS hit the dish, you'd know the air in the VRS was indeed sterile.
Do you think this would be worthwhile spending some of the NESTA cash on?
At the root of all of this are the questions: How far away from the gondola and the balloon do we need to sample? What are the winds at altitude? How turbulent? Do we need to measure this in flight?
Is there a fluid dynamics expert reading this? What is the safe distance beyond which any eddy bearing contamination from the balloon is unlikely to travel? Just how far from our balloon mothership do we need to go to sip pristine stratospheric air?