#### Life in the Stratosphere question

Larry

The papers we have  read from others who have attempted this  have all used air pumps to draw air over a filter.  I had purchased a computer fan rated to draw 120 CFM through the system.  Our system is constrained to 1/4 inch diameter tubing because of the diameter of the solenoid valves that seal the system until we get up there

So my compatriots are now thinking of a funnel vice a fan and orienting the flow vertically vice horizontally in the payload.

If my calculations are correct ( I need to double check them)  a funnel that was 4 inches at the wide end might produce in the  ball park of 120 CFM of stratospheric air dropping through the stratosphere.  Videos I have watched after PBC the payload seems to maintain a relatively straight orientation rocking back and forth some.

There might be some problems keeping the funnel sterile but other than that, is this idea worth putting some thought into?

Larry
KJ6PBS

L. Paul Verhage KD4STH

I feel the funnel idea would make better sense. A fan and funnel wouls both issues with sterility, so no difference there.

The funnel is passive and could be made larger, if necessary. Perhaps a sheet of Styrofoam could be placed over the funnel opening to keep it clean on the ground. Once the balloon is high enough, then it could be opened.

On Sun, Feb 28, 2021, 11:13 AM Larry <larry.phegley@...> wrote:
The papers we have  read from others who have attempted this  have all used air pumps to draw air over a filter.  I had purchased a computer fan rated to draw 120 CFM through the system.  Our system is constrained to 1/4 inch diameter tubing because of the diameter of the solenoid valves that seal the system until we get up there

So my compatriots are now thinking of a funnel vice a fan and orienting the flow vertically vice horizontally in the payload.

If my calculations are correct ( I need to double check them)  a funnel that was 4 inches at the wide end might produce in the  ball park of 120 CFM of stratospheric air dropping through the stratosphere.  Videos I have watched after PBC the payload seems to maintain a relatively straight orientation rocking back and forth some.

There might be some problems keeping the funnel sterile but other than that, is this idea worth putting some thought into?

Larry
KJ6PBS

Dan Bowen

Historically, fans haven't been good for sampling due to contamination and motor cooling problems with the high rpms needed.  Most programs settled on Venturi type air-ejectors to draw large volumes of the thin air through filters.  They used small bottles of compressed air or nitrogen to power the ejector pumps.

I posted a tweet a while back about one of the programs efforts here:

On Sun, Feb 28, 2021 at 20:14 Larry <larry.phegley@...> wrote:
The papers we have  read from others who have attempted this  have all used air pumps to draw air over a filter.  I had purchased a computer fan rated to draw 120 CFM through the system.  Our system is constrained to 1/4 inch diameter tubing because of the diameter of the solenoid valves that seal the system until we get up there

So my compatriots are now thinking of a funnel vice a fan and orienting the flow vertically vice horizontally in the payload.

If my calculations are correct ( I need to double check them)  a funnel that was 4 inches at the wide end might produce in the  ball park of 120 CFM of stratospheric air dropping through the stratosphere.  Videos I have watched after PBC the payload seems to maintain a relatively straight orientation rocking back and forth some.

There might be some problems keeping the funnel sterile but other than that, is this idea worth putting some thought into?

Larry
KJ6PBS

--
Thanks,
Dan

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