Stephen, I hope you can share your calculations or experimental data to show the performance of a valve vented balloon at realistic over pressure.
Risks for hot landings have to be multiplied by the number of flights - which would surely need to be in the millions to influence global climate to detectable levels. Balloons ending up in barns and workshops is a possibility. Andrew On Thu, 29 Dec 2022, 12:16 Stephen Salter, <[email protected]> wrote: > Andrew > > The survival rate for the Hindenburg was much higher than for aircraft > fuelled with kerosene because its lightness means it leaks upwards. Heavy > vapours like propane or butane are very much more dangerous if they sink > into cellars or bilges. The hydrogen flame has a very low emissivity. No > pump is needed. I can give you a valve design weighing less than one gram. > Think open prairie for launching. > > Stephen > > > > *From:* Andrew Lockley <[email protected]> > *Sent:* 29 December 2022 11:05 > *To:* Stephen Salter <[email protected]> > *Cc:* Luke Iseman <[email protected]>; 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. > > 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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