Large weather balloons don't have much over pressure relative to volume, so venting is a challenge. Valves and pumps add weight. Hydrogen has ground handling risks, due to flammability (Hindenberg), and any leaks risk buoyancy loss and the canopy descending loaded. The most extreme scenario is that an out of control failed balloon descends into an enclosed building through an open door, skylight, or Courtyard. In windy conditions, drift into a small industrial unit is perfectly possible, through the roller shutter doors - which could be automatically or accidentally closed behind, trapping the balloon and its flammable payload. This could allow a loaded canopy to leak out into a fully enclosed space, with ignition risks.
While such scenarios appear outlandish, with thousands or millions of launches, they become real risks. Andrew On Thu, 29 Dec 2022, 10:19 Stephen Salter, <[email protected]> wrote: > Hi > > I do not understand the bit about bursting. Control of a venting valve > protects the balloon and allows release at the chosen altitude. > > Helium is irreplaceable and needed for super cooling. Is there a reason > not to use hydrogen? > > Stephen > > > > *Emeritus Professor of Engineering Design* > > *School of Engineering* > > *University of Edinburgh* > > *Mayfield Road* > > *Edinburgh EH9 3DW* > > *Scotland* > > *0131 650 5704 or 0131 662 1180* > > *YouTube Jamie Taylor Power for Change* > > > > > > > > *From:* [email protected] <[email protected]> *On > Behalf Of *Daniele Visioni > *Sent:* 28 December 2022 23:51 > *To:* [email protected] > *Cc:* geoengineering <[email protected]> > *Subject:* Re: [geo] Make Sunsets: Clarifications! > > > > *This email was sent to you by someone outside the University.* > > You should only click on links or attachments if you are certain that the > email is genuine and the content is safe. > > Luke, > > I will keep finding this rather murky as long as you keep being so > hand-wavy about your numbers and then claiming you can offset a > “substantial amount of warming” in your homepage. > > > > Weather balloons have different bursting altitudes depending on 1) payload > 2) amount of helium used to inflate 3) material. > > You can find an example here with a calculator down below that lets you > calculate max bursting height based on inflation > > https://www.highaltitudescience.com/products/near-space-balloon-1200-g > > Which balloons did you use? > > How much did you inflate them? > > Did you check with the producer if the mix of SO₂ and He in the balloon > would affect their calculations, and if so how? > > The forcing we’re talking about changes depending on altitude of release > as well: at 19 it’s different than at 25 (and depending on your definition, > sometimes the tropopause is above 18km..), and above 29km sulfate aerosols > evaporate because temperatures are too high to form liquid aerosols. If the > balloon doesn’t burst at the right altitude, what would happen to the > oxidized S is not so simple - frankly I don’t know the answer off the top > of my head, there are a few factors that could influence this. Do you have > studies showing what would happen there based on lack of water vapor and > different temperature and OH levels? > > If you don’t - and you don’t have any tools to measure it yet - maybe you > should at least tone down the claims already present on your website? > > > > For some ranges of stratospheric releases of sulfate we have some numbers > for SAI we can be somewhat confident about - not just in term of the > forcing but in terms of downstream effects on the stratospheric composition > - but this may not be true for what you are proposing or claiming you are > doing. > > > > Lastly, in your Twitter account you claimed in a post 2 days ago that > there are “supporters and scientists who believe in you”. I would avoid > claiming you have the support of scientists if you don’t - or show proofs > if you do. As far as any scientist I know is concerned they don’t seem > particularly impressed - and your lack of clarity goes against any of the > calls for open and transparent research (not to mention inclusive decision > making) this community has asked in previous public statements. > > > > Daniele > > > > > > On 28 Dec 2022, at 18:09, Luke Iseman <[email protected]> wrote: > > > > Thanks Andrew, Olivier, Bala, and everyone else for diving in with > critiques here. I'm a cofounder of Make Sunsets and want to clarify a few > things: > > > > *Honesty: * > > We have no desire to mislead anyone. If we make a mistake (which we will), > we'll correct it. > > *Radiative Forcing:* > > I didn't make this "gram offsets a ton" number up. It comes from David > Keith's research: > > "a gram of aerosol in the stratosphere, delivered perhaps by high-flying > jets, could offset the warming effect of a ton of carbon dioxide, a factor > of 1 million to 1." > <https://keith.seas.harvard.edu/news/whats-right-temperature-earth> > > and, again: "Geoengineering’s leverage is very high—one gram of particles > in the stratosphere prevents the warming caused by a ton of carbon dioxide." > <https://longnow.org/seminars/02015/feb/17/patient-geoengineering/> > > By stating "offsetting the warming effect of 1 ton of carbon for 1 year," > I was trying to be more conservative than Professor Keith. I am correcting > "carbon" to read "carbon dioxide" on the cooling credit description right > now, and I'm adding a paragraph at the start of the post stating that > estimates vary, but a leading researcher cites a gram offsetting a ton. > > For the several hundred dollars of cooling credits we've already sold, > I'll be providing evidence to each purchaser that I've delivered at least 2 > grams per cooling credit. > > Olivier, or anyone else: I'd be happy to post something by you to our blog > explaining what you estimate the radiative forcing of 1g so2 released at > 20km altitude from in or near the tropics will be and why. I will include > language of your choosing explaining that you in no way endorse what we are > doing. > > I very much hope to get suggestions from this community on instrumentation > we should fly to improve the state of the science here. Again, I'm happy to > do this with disclaimers about how researchers we fly things for are not > endorsing our efforts. Or even without revealing who the researchers are: > we'll fly test instruments and provide data, no questions asked:) > > *Telemetry: * > > My first 2 flights had no telemetry: in April, this was still in > self-funded science project territory. After burning some sulfur and > capturing the resultant gas, I placed this in a balloon. I then added > helium, underinflating the balloon substantially, and let it go. There is > technically a slim possibility that neither of these balloons reached the > stratosphere, as I acknowledged to the Technology Review reporter. I will > add Spot trackers to my next flights. These cut out at 18km, so I'l be able > to confirm that I achieve at least this altitude. If (and this is a big if) > I'm able to recover the balloons, I'll have a lot more data from the flight > computer > <https://www.highaltitudescience.com/collections/electronics/products/eagle-flight-computer>. > I will eventually switch to Swarms > <https://www.sparkfun.com/products/19236?utm_campaign=May%206%2C%202022&utm_medium=email&_hsmi=212205037&_hsenc=p2ANqtz-9EyQOQ6C-9XuSOHa7CggOC8Pf2tEow_Fppo5pXgTHO8-7gV-aHrrYpnPcliws6Ju8j2PBAX3Tkog0oVpwk8XqWX2xo0w&utm_content=212206499&utm_source=hs_email>, > which should let me transmit more data regardless of balloon recovery. > > *Pricing: * > > Bala, you're totally right that this should be priced much lower. We're > trying to make enough with our early flights to stay in business until we > get meaningful traction with customers, and we plan to eventually drop > prices to $1 per ton or less. > > *Reuse: * > > We are not yet reusing balloons, and Andrew is correct that latex UV > degradation will limit our ability to do so with weather balloons. Given > that balloon cost is our main expense per gram, even a few uses per balloon > will dramatically improve the economics here. > > > > I expect to disagree with some of you, but I hope we can do so politely > and assuming good intentions. > > -- > You received this message because you are subscribed to the Google Groups > "geoengineering" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/geoengineering/550ec54e-4b36-4b6e-b4be-834229c870cen%40googlegroups.com > <https://groups.google.com/d/msgid/geoengineering/550ec54e-4b36-4b6e-b4be-834229c870cen%40googlegroups.com?utm_medium=email&utm_source=footer> > . > > -- > You received this message because you are subscribed to the Google Groups > "geoengineering" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/geoengineering/9942AB80-E648-4DCE-8E51-B7FC7EFF1352%40gmail.com > <https://groups.google.com/d/msgid/geoengineering/9942AB80-E648-4DCE-8E51-B7FC7EFF1352%40gmail.com?utm_medium=email&utm_source=footer> > . > The University of Edinburgh is a charitable body, registered in Scotland, > with registration number SC005336. Is e buidheann carthannais a th’ ann an > Oilthigh Dhùn Èideann, clàraichte an Alba, àireamh clàraidh SC005336. > > -- > You received this message because you are subscribed to the Google Groups > "geoengineering" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/geoengineering/AM8PR05MB80359D6D052CF2BA3940E360A7F39%40AM8PR05MB8035.eurprd05.prod.outlook.com > <https://groups.google.com/d/msgid/geoengineering/AM8PR05MB80359D6D052CF2BA3940E360A7F39%40AM8PR05MB8035.eurprd05.prod.outlook.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. 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