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In reading the documents google's Loon made available before shutting down (and saying that hydrogen airships were the way to go) [https://storage.googleapis.co

In reading the documents google's Loon made available before shutting down (and saying that hydrogen airships were the way to go) [https://storage.googleapis.com/x-prod.appspot.com/files/The%20Loon%20Library.pdf https://storage.googleapis.com/x-prod.appspot.com/files/The%...], the bottleneck on staying up longer was helium loss. Lots of things, mechanical failure etc, caused flights to end early. But the ultimate limit seems to be either helium loss or the impact of helium absorption on seals etc causing failure. Helium is a very small molecule, so very hard to keep confined. However, as they learned from experience, Loon was slowly increasing their upper limit on how long their balloons could stay up.

DoctorOetker 2y ago
Sure there will be leakage. Let's look at the composition vs height: https://en.wikipedia.org/wiki/Atmosphere_of_Earth#/media/File:Msis_atmospheric_composition_by_height.svg https://en.wikipedia.org/wiki/Atmosphere_of_Earth#/media/Fil... I understand helium will be sparse at low heights, but at each height there is a diversity of species, among which will be a lighter one. Could a balloon be oversized so that instead of using helium, at each height an 80% fill of the locally (that height) lightest gas could keep the balloon afloat. Oversized for this but also for the added weight for separating equipment for the wanted gas and associated panels to power it. I.e. what prevents a balloon from flying indefinitely? At least up until radiation damage of the balloon membrane... Have such attempts been made and what were the lessons?
- worldvoyageur 2y ago
  These guys [https://www.scientificballoonsolutions.com/news/ https://www.scientificballoonsolutions.com/news/], as of October 2018, claim the world record. [edit: the site linked says Alan Adamson but an upstream post mentions Lee Meadows. That thread also credits Bill Brown as a pioneer - https://www.stratoballooning.org/membership#!biz/id/5f4d7b97c79e8d2604025a39 https://www.stratoballooning.org/membership#!biz/id/5f4d7b97...] The world record balloon was launched on September 21, 2016, stayed up over 767 days, circled the world 35 times and traveled over 1.5 million kilometers. Their website, still from 2018, indicates they are working on even better designs.

DoctorOetker 2y ago

Sure there will be leakage. Let's look at the composition vs height: https://en.wikipedia.org/wiki/Atmosphere_of_Earth#/media/File:Msis_atmospheric_composition_by_height.svg https://en.wikipedia.org/wiki/Atmosphere_of_Earth#/media/Fil... I understand helium will be sparse at low heights, but at each height there is a diversity of species, among which will be a lighter one. Could a balloon be oversized so that instead of using helium, at each height an 80% fill of the locally (that height) lightest gas could keep the balloon afloat. Oversized for this but also for the added weight for separating equipment for the wanted gas and associated panels to power it. I.e. what prevents a balloon from flying indefinitely? At least up until radiation damage of the balloon membrane... Have such attempts been made and what were the lessons?

worldvoyageur 2y ago
These guys [https://www.scientificballoonsolutions.com/news/ https://www.scientificballoonsolutions.com/news/], as of October 2018, claim the world record. [edit: the site linked says Alan Adamson but an upstream post mentions Lee Meadows. That thread also credits Bill Brown as a pioneer - https://www.stratoballooning.org/membership#!biz/id/5f4d7b97c79e8d2604025a39 https://www.stratoballooning.org/membership#!biz/id/5f4d7b97...] The world record balloon was launched on September 21, 2016, stayed up over 767 days, circled the world 35 times and traveled over 1.5 million kilometers. Their website, still from 2018, indicates they are working on even better designs.