Andrew
Answers to your questions about the our recent URL paper on stratospheric albedo modification delivery systems. Q: Isn't this just a reformatted version of the Aurora flight report? A: Essentially yes. The online supplemental information is the Aurora report, the paper is newly written but has relatively little view analysis. The paper puts the report in an archival peer-reviewed journal. We made minor improvements in response to review but nothing fundamental. We could have kept the report to ourselves until publication, but because our views about the importance of openness in this field we decide to release the entire report when it was completed following our internal peer-review. Q: it ignores gas guns (which are half the price in $/kg of solid-propellant guns) and contradicts SPICE balloon cost estimates. It works up aircraft way more than other tech, leading to unsurprisingly lower cost estimates of these technologies. Coming up with low prices for worked up tech seems a common thread in papers. A: This seems to me a very odd criticism of this paper. Unlike (to my knowledge) any other paper we examined all the different options in our scope using the same costing assumptions and industry-standard cost estimating relationships (CERs). I am not aware that the SPICE project has done anything similar. We did not come into it with any particular bias towards airplanes and in practice we spent a lot of time on hybrid airships and on the balloon with hose option because analysis there was relatively harder to do. If you discount the section on existing aircraft which seems fair since there are no alternative options that are as ready to go, the section on new aircraft is not substantially longer than the sections on hybrid airships or the hose option. Finally it seems like an odd criticism because in fact we found that the cost of hybrid airships, new aircraft, and the balloon with hose option were broadly comparable. gas guns (which are half the price in $/kg of solid-propellant guns) We did not spend significant time on gas guns because we talked to David Whelan, US National Academy member and senior scientist at Boeing, one of the world experts on this topic, and he advised us that gas guns would not be a significant advantage for the altitude range that is relevant here. Even if gas guns were half the price of solid propellant guns as you assert, and I do not know of a study that shows that to be true when you count capital and operating costs, the cost would still be absurdly high compared to the other options investigated (hybrid airships, the balloon with hose, or regular aircraft) and therefore all but irrelevant. David -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Andrew Lockley Sent: Thursday, August 30, 2012 5:52 PM To: geoengineering; David Keith Subject: [geo] Cost analysis of stratospheric albedo modification delivery systems (ERL) Open Access Poster's note: Isn't this just a reformatted version of the Aurora flight report? If so, it ignores gas guns (which are half the price in $/kg of solid-propellant guns) and contradicts SPICE balloon cost estimates. It works up aircraft way more than other tech, leading to unsurprisingly lower cost estimates of these technologies. Coming up with low prices for worked up tech seems a common thread in papers. This could be clarified by authors generally, I feel. http://iopscience.iop.org/1748-9326/7/3/034019 We perform engineering cost analyses of systems capable of delivering 1-5 million metric tonnes (Mt) of albedo modification material to altitudes of 18-30 km. The goal is to compare a range of delivery systems evaluated on a consistent cost basis. Cost estimates are developed with statistical cost estimating relationships based on historical costs of aerospace development programs and operations concepts using labor rates appropriate to the operations. We evaluate existing aircraft cost of acquisition and operations, perform in-depth new aircraft and airship design studies and cost analyses, and survey rockets, guns, and suspended gas and slurry pipes, comparing their costs to those of aircraft and airships. Annual costs for delivery systems based on new aircraft designs are estimated to be $1-3B to deliver 1 Mt to 20-30 km or $2-8B to deliver 5 Mt to the same altitude range. Costs for hybrid airships may be competitive, but their large surface area complicates operations in high altitude wind shear, and development costs are more uncertain than those for airplanes. Pipes suspended by floating platforms provide low recurring costs to pump a liquid or gas to altitudes as high as ~ 20 km, but the research, development, testing and evaluation costs of these systems are high and carry a large uncertainty; the pipe system's high operating pressures and tensile strength requirements bring the feasibility of this system into question. The costs for rockets and guns are significantly higher than those for other systems. We conclude that (a) the basic technological capability to deliver material to the stratosphere at million tonne per year rates exists today, (b) based on prior literature, a few million tonnes per year would be sufficient to alter radiative forcing by an amount roughly equivalent to the growth of anticipated greenhouse gas forcing over the next half century, and that (c) several different methods could possibly deliver this quantity for less than $8B per year. We do not address here the science of aerosols in the stratosphere, nor issues of risk, effectiveness or governance that will add to the costs of solar geoengineering. -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To post to this group, send email to [email protected]<mailto:[email protected]>. To unsubscribe from this group, send email to [email protected]<mailto:[email protected]>. For more options, visit this group at http://groups.google.com/group/geoengineering?hl=en. -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/geoengineering?hl=en.
