Making Sunsets in San Francisco

[Alan Robock ☮]

Dear All,

On Friday I attended an event by Making Sunsets in San Francisco.  This slide show illustrates my experience, http://climate.envsci.rutgers.edu/robock/talks/MakeSunsets.pptx   While there, Luke Iseman told me that they launched three balloons in Berkeley the day before and that they retrieved all of them using GPS tracking.   I just found out that this launch was part of a CBS Saturday Morning presentation on SRM, https://youtu.be/XmVsat8-Dso 

A 1992 US government report on this (Committee on Science Engineering and Public Policy, 1992: Geoengineering options, Appendix Q, in Policy Implications of Greenhouse Warming: Mitigation, Adaptation, and the Science Base, pp. 433 – 464, Natl. Acad. Press, Washington, D. C.), examining options for getting material to the stratosphere, said that if balloons were used, ‘‘The fall of collapsed balloons might be an annoying form of trash rain.’’  The film of the balloon popping in the CBS show showed that scraps of the balloon went flying, so that they did not retrieve all the parts of the balloon.  He also told me that the latex balloons they launched in SF were biodegradable, but I don't think they degrade fast enough to make them safe. 

Alan

Alan Robock, Distinguished Professor
   Editor, Reviews of Geophysics
   Chair, AGU College of Fellows
Department of Environmental Sciences      Phone: +1-848-932-5751
Rutgers University             E-mail: rob...@envsci.rutgers.edu
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[Andrew Lockley]

This trash problem is why SATAN used pumps/valves to evacuate the balloon. The limited flow rate available means that this method doesn't work unless they're set to ascend very slowly. Civil airspace rules preclude slow ascent in the UK, so the SATAN canopy burst similarly. A sacrificial carrier balloon can be used to launch SATAN, so that it can remain in position for several hours - but the lift canopy is itself a source of trash. 

The only potential way envisaged to have a fast rising and trash-free balloon is to use a canopy which is vented by means of a tie or clip that opens a very large hole - akin to the air dancer figures used to advertise businesses. This is because it's challenging to do this with a latex balloon - they rise fast, have low internal pressure, and are large in volume with a small hole. A custom made PU canopy can be used to make a lightweight air dancer tube - but it's expensive.

Finally, a totally different approach is to use a hot air balloon (rozière type), which simultaneously addresses the issue of lift gas leakage. This may be promising, but is complex and expensive to test. Heat loss from the envelope likely precludes the use of smaller balloons, making even early testing very expensive. 

SATAN, and similar designs, are therefore best used as intended - for small scale test deployment, carrying small sensor payloads. I don't see that Make Sunsets approach is appropriate for scaling deployment.

Andrew 

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