Re: [geo] Stratospheric aerosol injection tactics and costs in the first 15 years of deployment - IOPscience

[Andrew Lockley]

As far as I know, the cost cliffs at the limit of air-breathing engines
(with reasonable payloads). As discussed elsewhere on the thread, there are
a number high-ceiling techs: hybrid engines, reusable rockets, and guns.
All are likely to be more expensive/uncertain, medium term.



On Sun, 6 Jan 2019, 22:34 Douglas MacMartin  Haven’t read through all of this exchange carefully yet, but just a
> comment that, provided we have time (and research funding) between now and
> deployment, it would be good to understand the cost vs altitude trade
> moderately well, both on the deployment cost side, and on the climate
> side-effect side.
>
>
>
> If, for example, 23km is 10x more expensive than 22km, we ought to know
> that when doing climate model simulations.  Though, even if that were true,
> we should still consider simulations across a range of altitudes.
>
>
>
> Buried in all of this is that we’re doing research for a subject without
> knowing the timeline we need to meet for the outcomes of that research…
> what one might do deployment-wise if someone wanted to start deploying in
> 2025 might be very different if that year was 2040.  (And there’s a
> reasonable argument for being prepared for a range of possible answers to
> the timeframe question.)
>
>
>
> d
>
>
>
> *From:* geoengineering@googlegroups.com [mailto:
> geoengineering@googlegroups.com] *On Behalf Of *Andrew Lockley
> *Sent:* Sunday, January 06, 2019 5:26 PM
> *To:* Wake Smith 
> *Cc:* geoengineering 
> *Subject:* Re: [geo] Stratospheric aerosol injection tactics and costs in
> the first 15 years of deployment - IOPscience
>
>
>
> Wake
>
>
>
> Thanks for your detailed response.
>
>
>
> As regards hybrid engines, I can't comment on the costs or the airframe
> requirements - but I suspect it would be worth a look. One benefit is that
> it would allow the use of off-the-shelf engines, thus cutting dev costs.
> These are frontloaded and uncertain, as you point out. The GE/Pratt
> alternatives are also attractive for readiness reasons - but lack the
> attractive additional altitude.
>
>
>
> I would be cautious about specifying short flights. I have seen the new,
> unreleased TU Delft analysis on this, and I don't think that short flights
> are likely to be a universally agreed strategy among the teams working on
> this issue. That's based on the (English?) work on vapour condensation
> delivery. The key variable is that dropping acid is far more mass efficient
> than ambient condensation, due to monodisperse particle size distribution.
> It therefore (likely) reduces O3 loss and rain out pollution, too.
>
>
>
> I don't agree with your assessment of gun tech. Railguns are under active
> development by both the US and China (although these are unsuitable for
> Geoengineering). A more suitable technology is the gas gun. Quicklaunch and
> Utron (both now in the deadpool) have worked on this. Utron actually got a
> prototype working. The benefit of gas guns is that velocities aren't
> subject to any obvious technological limitation (even up to LEO), so
> injection can be as high as you like. This trades off against mass flux,
> due to the efficiencies discussed earlier. Faster splashdown would make
> shell recovery and refurbishment more difficult, though.
>
>
>
> As regards SpaceX, I think you're at risk of comparing apples with
> oranges. Their intention is to compete with airliners (including supersonic
> ones from eg Boom), so they're likely going to be 1-2 orders cheaper for
> suborbital than for space launch.
>
>
>
> Happy to discuss further, if you have more to add.
>
>
>
> Andrew
>
>
>
>
>
>
>
>
>
>
>
> On Sun, 6 Jan 2019, 21:23 Wake Smith 
> Dear Andrew (& group),
>
> Firstly, thank you for the thorough and thoughtful questions.  I am happy
> to dig in further on these details with knowledgeable correspondents.
> Secondly, I should note that I do NOT consider this paper to have been the
> final and definitive word on early deployment tactics, but rather simply
> (and hopefully) a forward step from the essential work done earlier by
> McClellan et al and others.  “McClellan” (as I will hereinafter refer to
> their paper) remains foundational and I started my explorations by meeting
> with both McClellan and Keith and picking up the ball where they laid it.
> I am comfortable with our paper insofar as it went, but I acknowledge there
> to be many yet still unanswered questions which I intend to address in
> subsequent undertakings.  Thirdly, I am speaking here only for myself,
> though Gernot will undoubtedly weigh in additionally as he sees fit.
>
> Starting with your “Tilmes +5k” question, I should note that our paper
> diverged from McClellan at the outset by choosing a specific mission and
> then considering platforms to fulfill that mission and only that mission.
> McClellan on the other hand considered deployment altitudes ranging from 18
> – 30 kms, targeting the lower part (18 – 25kms) of that range.  Table 2
> surveys an even wider range, 

RE: [geo] Stratospheric aerosol injection tactics and costs in the first 15 years of deployment - IOPscience

[Douglas MacMartin]

Haven’t read through all of this exchange carefully yet, but just a comment 
that, provided we have time (and research funding) between now and deployment, 
it would be good to understand the cost vs altitude trade moderately well, both 
on the deployment cost side, and on the climate side-effect side.

If, for example, 23km is 10x more expensive than 22km, we ought to know that 
when doing climate model simulations.  Though, even if that were true, we 
should still consider simulations across a range of altitudes.

Buried in all of this is that we’re doing research for a subject without 
knowing the timeline we need to meet for the outcomes of that research… what 
one might do deployment-wise if someone wanted to start deploying in 2025 might 
be very different if that year was 2040.  (And there’s a reasonable argument 
for being prepared for a range of possible answers to the timeframe question.)

d

From: geoengineering@googlegroups.com [mailto:geoengineering@googlegroups.com] 
On Behalf Of Andrew Lockley
Sent: Sunday, January 06, 2019 5:26 PM
To: Wake Smith 
Cc: geoengineering 
Subject: Re: [geo] Stratospheric aerosol injection tactics and costs in the 
first 15 years of deployment - IOPscience

Wake

Thanks for your detailed response.

As regards hybrid engines, I can't comment on the costs or the airframe 
requirements - but I suspect it would be worth a look. One benefit is that it 
would allow the use of off-the-shelf engines, thus cutting dev costs. These are 
frontloaded and uncertain, as you point out. The GE/Pratt alternatives are also 
attractive for readiness reasons - but lack the attractive additional altitude.

I would be cautious about specifying short flights. I have seen the new, 
unreleased TU Delft analysis on this, and I don't think that short flights are 
likely to be a universally agreed strategy among the teams working on this 
issue. That's based on the (English?) work on vapour condensation delivery. The 
key variable is that dropping acid is far more mass efficient than ambient 
condensation, due to monodisperse particle size distribution. It therefore 
(likely) reduces O3 loss and rain out pollution, too.

I don't agree with your assessment of gun tech. Railguns are under active 
development by both the US and China (although these are unsuitable for 
Geoengineering). A more suitable technology is the gas gun. Quicklaunch and 
Utron (both now in the deadpool) have worked on this. Utron actually got a 
prototype working. The benefit of gas guns is that velocities aren't subject to 
any obvious technological limitation (even up to LEO), so injection can be as 
high as you like. This trades off against mass flux, due to the efficiencies 
discussed earlier. Faster splashdown would make shell recovery and 
refurbishment more difficult, though.

As regards SpaceX, I think you're at risk of comparing apples with oranges. 
Their intention is to compete with airliners (including supersonic ones from eg 
Boom), so they're likely going to be 1-2 orders cheaper for suborbital than for 
space launch.

Happy to discuss further, if you have more to add.

Andrew





On Sun, 6 Jan 2019, 21:23 Wake Smith 
mailto:w...@crowsven.com> wrote:
Dear Andrew (& group),
Firstly, thank you for the thorough and thoughtful questions.  I am happy to 
dig in further on these details with knowledgeable correspondents.  Secondly, I 
should note that I do NOT consider this paper to have been the final and 
definitive word on early deployment tactics, but rather simply (and hopefully) 
a forward step from the essential work done earlier by McClellan et al and 
others.  “McClellan” (as I will hereinafter refer to their paper) remains 
foundational and I started my explorations by meeting with both McClellan and 
Keith and picking up the ball where they laid it.  I am comfortable with our 
paper insofar as it went, but I acknowledge there to be many yet still 
unanswered questions which I intend to address in subsequent undertakings.  
Thirdly, I am speaking here only for myself, though Gernot will undoubtedly 
weigh in additionally as he sees fit.
Starting with your “Tilmes +5k” question, I should note that our paper diverged 
from McClellan at the outset by choosing a specific mission and then 
considering platforms to fulfill that mission and only that mission.  McClellan 
on the other hand considered deployment altitudes ranging from 18 – 30 kms, 
targeting the lower part (18 – 25kms) of that range.  Table 2 surveys an even 
wider range, from  as low as 40kft (~12.2 km) up to 100 kft (~30 km).  So wide 
a spectrum of possible injection altitudes naturally leads to a wide variety of 
platforms suitable to address at least some of the part of that spectrum and 
contributed to an impression that there were many ways to “skin the cat” as it 
were.  More specifically, this implied that some sub-stratospheric altitudes 
were nonetheless acceptable for deployment even though the text of the paper 
called for 

Re: [geo] Stratospheric aerosol injection tactics and costs in the first 15 years of deployment - IOPscience

[Andrew Lockley]

Wake

Thanks for your detailed response.

As regards hybrid engines, I can't comment on the costs or the airframe
requirements - but I suspect it would be worth a look. One benefit is that
it would allow the use of off-the-shelf engines, thus cutting dev costs.
These are frontloaded and uncertain, as you point out. The GE/Pratt
alternatives are also attractive for readiness reasons - but lack the
attractive additional altitude.

I would be cautious about specifying short flights. I have seen the new,
unreleased TU Delft analysis on this, and I don't think that short flights
are likely to be a universally agreed strategy among the teams working on
this issue. That's based on the (English?) work on vapour condensation
delivery. The key variable is that dropping acid is far more mass efficient
than ambient condensation, due to monodisperse particle size distribution.
It therefore (likely) reduces O3 loss and rain out pollution, too.

I don't agree with your assessment of gun tech. Railguns are under active
development by both the US and China (although these are unsuitable for
Geoengineering). A more suitable technology is the gas gun. Quicklaunch and
Utron (both now in the deadpool) have worked on this. Utron actually got a
prototype working. The benefit of gas guns is that velocities aren't
subject to any obvious technological limitation (even up to LEO), so
injection can be as high as you like. This trades off against mass flux,
due to the efficiencies discussed earlier. Faster splashdown would make
shell recovery and refurbishment more difficult, though.

As regards SpaceX, I think you're at risk of comparing apples with oranges.
Their intention is to compete with airliners (including supersonic ones
from eg Boom), so they're likely going to be 1-2 orders cheaper for
suborbital than for space launch.

Happy to discuss further, if you have more to add.

Andrew






On Sun, 6 Jan 2019, 21:23 Wake Smith  Dear Andrew (& group),
>
> Firstly, thank you for the thorough and thoughtful questions.  I am happy
> to dig in further on these details with knowledgeable correspondents.
> Secondly, I should note that I do NOT consider this paper to have been the
> final and definitive word on early deployment tactics, but rather simply
> (and hopefully) a forward step from the essential work done earlier by
> McClellan et al and others.  “McClellan” (as I will hereinafter refer to
> their paper) remains foundational and I started my explorations by meeting
> with both McClellan and Keith and picking up the ball where they laid it.
> I am comfortable with our paper insofar as it went, but I acknowledge there
> to be many yet still unanswered questions which I intend to address in
> subsequent undertakings.  Thirdly, I am speaking here only for myself,
> though Gernot will undoubtedly weigh in additionally as he sees fit.
>
> Starting with your “Tilmes +5k” question, I should note that our paper
> diverged from McClellan at the outset by choosing a specific mission and
> then considering platforms to fulfill that mission and only that mission.
> McClellan on the other hand considered deployment altitudes ranging from 18
> – 30 kms, targeting the lower part (18 – 25kms) of that range.  Table 2
> surveys an even wider range, from  as low as 40kft (~12.2 km) up to 100 kft
> (~30 km).  So wide a spectrum of possible injection altitudes naturally
> leads to a wide variety of platforms suitable to address at least some of
> the part of that spectrum and contributed to an impression that there were
> many ways to “skin the cat” as it were.  More specifically, this implied
> that some sub-stratospheric altitudes were nonetheless acceptable for
> deployment even though the text of the paper called for injection above the
> tropopause.  From the standpoint of the grubby aviation guys simply trying
> to fly the mission, altitude is the critical parameter here, so more
> specificity was required in order to zero in on a platform choice.  We
> therefore chose to define a much more specific mission that always deployed
> well into the stratosphere, which in turn led us to a more specific
> platform recommendation.  The mission we chose was injections as high as
> 65k ft (~20km), and we sourced this mission requirement from
> MacMartin/Tilmes/Kravitz.  To be clear, this does not mean that all
> injections would necessarily achieve this altitude – one might choose lower
> on particular days and at higher latitudes – but the maximum injection
> altitude anywhere defines the altitude threshold for the platform design.
> So, why didn’t we consider the engine alternative you note?  Because it was
> not necessary to achieve the defined mission.
>
> The above of course begs the question as to whether we chose the right
> mission, or whether we should have instead chosen various alternative
> missions, such as the “+5k” alternative.  As regards the mission we chose,
> we had to start somewhere, and this seemed (and still does seem) like the
> 

Re: [geo] Stratospheric aerosol injection tactics and costs in the first 15 years of deployment - IOPscience

[Andrew Lockley]

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  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
> 

RE: [geo] Stratospheric aerosol injection tactics and costs in the first 15 years of deployment - IOPscience

[Douglas MacMartin]

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" 
mailto: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

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 

Re: [geo] Stratospheric aerosol injection tactics and costs in the first 15 years of deployment - IOPscience

[Franz Dietrich Oeste]

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" 
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

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.


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