Wake / Gernot I have some questions on your paper. I thought it would be best to pose them in public, in the hope that others will be able to read any reply. I apologise in advance if there are elements of your paper I have not fully understood.
Citing Tilmes, you suggest a + 5 k altitude change would be beneficial , but suggest engines are a limiting factor . The BAE Systems Sabre engine is designed for high-altitude use. (David Keith was previously critical when I suggested the use of this system). If you have considered this engine type (or similar), why did you disregard it? Mid-air refueling is an established technology. Your paper does not discuss the idea of conveying fuel or payload in flight. The high-altitude aircraft you propose would be less fuel efficient and more expensive than conventional tankers. These factors imply that any element of the process that can be outsourced to tankers would represent a significant cost saving. Was there a reason why you did not consider a two stage approach? The TU Delft aircraft appears superficially similar to yours in design, save the use of custom engines. Why does your Design come out at such a dramatically lower cost? Your proposed costings are almost identical to the new aircraft design proposed by Mcclellan. Your paper does not give much detail on why your Design would be different , and what advantages it would have. Could you please elaborate on this? You plan a manned aircraft, but the reduced safety concerns of a drone mean that certification costs are potentially lower, particularly if the planes were flown from isolated, single purpose airports (where any crash would be unlikely to cause damage or injury). Did you analyse any such highly encapsulated operational model? On board conversion of sulphur is unlikely to allow very fine control over droplet size. Any outsize aerosols are both much heavier, and much less effective, than an ideal monodisperse spray. Did you consider the alternative of carrying sulphuric acid, so you could inject monodisperse aerosols? If so, what are the cost implications? You give very little detail on the engine modifications necessary. Could you please elaborate on their nature, and offer a breakdown of anticipated cost? As regards alternative technologies, I have some further questions: Your consideration of costs from SpaceX appears to be based on their space launch technology. This is inherently a low volume operation. SpaceX have also proposed a suborbital passenger service, which would have far higher flight volumes - and thus far lower marginal costs per launch. This appears not to have been included in your analysis. Have you done any side calculations , based on realistic cost assumptions for adapting SpaceX suborbital passenger rockets ? You suggest that airships are at too early a stage of development to be practical. Hybrid Air Systems already have a flying vehicle of the type required, albeit one not adapted to this specific job . Did you examine this firms technology? If so, what were your reasons for rejecting it? Maclellan's paper considered gun launch, but did not consider obvious opportunities for costs savings. These include: reusable shells; and converting the guns from specialised solid propellant bags, to natural gas / hydrogen fuel, with air as an oxidizer. Further , guns allow much higher altitudes than aircraft, which you advised is desirable for reasons of efficiency. Such modifications would imply a cost reduction of approaching one order. Is there a reason you have elected not to optimise gun designs, in your analysis? Finally, you make no reference to any electrical launch technology. A cursory look at hyperloop suggests that it can be modified to attain approximately the launch velocities required. Did you consider this, or similar electrical launch? If so, why did you reject it? I look forward to receiving any response you are able to send. Andrew On Sat, 24 Nov 2018, 14:35 Douglas MacMartin <dgm...@cornell.edu wrote: > For context, the “huge expense” you refer to below, for the first 15 years > of deployment, is about 1.5x the estimated cost of the Camp fire in > California last week. > > > > Or, 15 years of deployment (including development costs), are about 15% of > the costs in the US alone from the 2017 hurricane season. And certainly > far cheaper than actually solving the problem by pulling out the CO2. > > > > Lots of reasons to be concerned about SAI, but as far as costs are > concerned, the appropriate concern should be that it is too cheap, and that > cost won’t present enough of a barrier to deployment. > > > > (And as I’ve pointed out before, saying this doesn’t “solve” the climate > problem is like pointing out that air bags don’t “solve” the problem of > having car accidents, or a million other analogies. Of course it doesn’t. > No-one says it does. But it could reduce impacts and prevent lots of > climate damages. Until we are certain that the climate problem can be > “solved” by other means, it would be premature to dismiss something that > has the potential to limit damages.) > > > > *From:* geoengineering@googlegroups.com [mailto: > geoengineering@googlegroups.com] *On Behalf Of *Franz Dietrich Oeste > *Sent:* Saturday, November 24, 2018 6:49 AM > *To:* andrew.lock...@gmail.com; geoengineering@googlegroups.com > *Subject:* Re: [geo] Stratospheric aerosol injection tactics and costs in > the first 15 years of deployment - IOPscience > > > > Thanks to Wake Smith and Gernot Wagner for their work! Their paper may > open our eyes to the probable unsuitability of the climate influencing tool > Stratospheric Solar Radiation Management (SRM) or as named by the authors > Stratospheric Aerosol Injection (SAI): > > > > SRM shall act within the stratosphere 20 km above the ground. To gain a > temperature reduction of 0.30 K in 2047 it needs a yearly uplift to this > height of 1,5 million tons of sulfur. The sulfur shall be burned by new > kind of aircrafts in situ to gain gaseous SO2 (boiling point -10 °C) which > becomes transformed by oxidiation and hydration to about 6 million > tons aerosol made of a rather concentrated sulfuric acid - per year. This > aerosol shall spread around the globe and mirror parts of the sun radiation > back into the space. > > > > With the existing aircraft design sulfur lifting to these heights is > impossible. A new kind of aircraft needs to be developed to do the job. > This new aircraft should be able to lift a payload of 25 tons of liquid > sulfur to 20 km above the ground then keeping at this height and burn there > the sulfur load which emits with the flue gas as SO2. About 60 000 flights > per year are necessary to gain the global temperature reduction of 0,30 K. > > > > Thankfully this article discusses very clearly within chapter 6 that such > activities could not remain undetected. Their conclusion is that it would > be rather impossible that those activities remain undetected or might kept > as a secret. > > > > According to this low result of 0,30 K global temperature decrease gained > by this huge expense and 1,5 Million tons of sulfur burned in the > stratosphere the SRM method seems completely unsuitable to solve our > climate problem. Not only that the SRM method does not reduce any of the > increasing levels of the essential greenhouse gases CO2 and methane, it > surely increases the CO2 gas level. Any reduction of the sun radiation at > the surface decrease the assimilation by which plants transform CO2 into > organic C and oxygen. Further SRM would increase the methane level by > decreasing the UV radiation dependent hydroxyl radical level which acts as > a degradation tool to methane and further volatile organics because the sun > radiation decrease by SRM concerns particularly the UV fraction. > > > > It is my very hope that this article helps to reduce the hype about SRM. > > > > Franz D. Oeste > > > > > > > > ------ Originalnachricht ------ > > Von: "Andrew Lockley" <andrew.lock...@gmail.com> > > An: geoengineering@googlegroups.com > > Gesendet: 23.11.2018 16:36:27 > > Betreff: [geo] Stratospheric aerosol injection tactics and costs in the > first 15 years of deployment - IOPscience > > > > *http://iopscience.iop.org/article/10.1088/1748-9326/aae98d/meta* > <http://iopscience.iop.org/article/10.1088/1748-9326/aae98d/meta> > > > > Stratospheric aerosol injection tactics and costs in the first 15 years of > deployment > > Wake Smith1 and Gernot Wagner2 > > > > Published 23 November 2018 • © 2018 The Author(s). Published by IOP > Publishing Ltd > > Environmental Research Letters, Volume 13, Number 12 > > Download Article PDF DownloadArticle ePub > > Article has an altmetric score of 157 > > > > Abstract > > We review the capabilities and costs of various lofting methods intended > to deliver sulfates into the lower stratosphere. We lay out a future solar > geoengineering deployment scenario of halving the increase in anthropogenic > radiative forcing beginning 15 years hence, by deploying material to > altitudes as high as ~20 km. After surveying an exhaustive list of > potential deployment techniques, we settle upon an aircraft-based delivery > system. Unlike the one prior comprehensive study on the topic (McClellan et > al 2012 Environ. Res. Lett. 7 034019), we conclude that no existing > aircraft design—even with extensive modifications—can reasonably fulfill > this mission. However, we also conclude that developing a new, > purpose-built high-altitude tanker with substantial payload capabilities > would neither be technologically difficult nor prohibitively expensive. We > calculate early-year costs of ~$1500 ton−1 of material deployed, > resulting in average costs of ~$2.25 billion yr−1 over the first 15 years > of deployment. We further calculate the number of flights at ~4000 in year > one, linearly increasing by ~4000 yr−1. We conclude by arguing that, while > cheap, such an aircraft-based program would unlikely be a secret, given the > need for thousands of flights annually by airliner-sized aircraft operating > from an international array of bases. > > -- > 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 geoengineering+unsubscr...@googlegroups.com. > To post to this group, send email to geoengineering@googlegroups.com. > Visit this group at https://groups.google.com/group/geoengineering. > For more options, visit https://groups.google.com/d/optout. > > -- > 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 geoengineering+unsubscr...@googlegroups.com. > To post to this group, send email to geoengineering@googlegroups.com. > Visit this group at https://groups.google.com/group/geoengineering. > For more options, visit https://groups.google.com/d/optout. > -- 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 geoengineering+unsubscr...@googlegroups.com. To post to this group, send email to geoengineering@googlegroups.com. Visit this group at https://groups.google.com/group/geoengineering. For more options, visit https://groups.google.com/d/optout.
