To date, there has been an extremely small amount of research investigating the feasibility of retrofitting existing planes to deploy or test SAI at high latitudes and low altitudes (HiLLA). To solve this gap, the Reflective team has commissioned aerospace company AeroTEC to study the feasibility of aircraft retrofitting. We'll update this entry with a link to the summary of key findings when we publish them.
Metric
Time to achieve (acquire and modify) a fleet capable of delivering a ~1 Mt/year payload to 15 km is over 5 years from first large-scale funding.
Uncertainty
Given the AeroTEC study, the confidence in the ability to have a fleet capable of delivering on the metric with the appropriate level of funding is high. Even if the AeroTEC numbers are too liberal, something in the realm of a payload of 50 tons per aircraft up to 15km would still make the metric very achievable. That being said, we acknowledge that more research is needed here given the limited current literature on the topic.
Decision relevance
If the timeline were longer than that dictated in the metric, this would materially impact deployment timeline by ≤5 years, and therefore we classify the decision relevance as medium.
Further Information
In the scenario dependence section of our methodology, we assume that deployment would begin with modified existing aircraft at high latitudes and low altitudes (HiLLA). We believe this can be achieved with retrofitted, existing aircraft that are able to deploy at 15 km of altitude. There are multiple tradeoffs to consider here. The existing service ceiling of some business jets is already around 15 km, but the payload at lower altitudes is already small (~10 tons) and it is unclear how much more this would decrease at the top of the service ceiling. Typical commercial, widebody jets have a service ceiling of order 13km. AeroTEC found that a 747 could likely carry a payload significantly larger than that of a business jet to 15km, but these aircraft are no longer in production so procurement might be a limiting factor. Note that this uncertainty does not include retrofitting the interior of the aircraft for a SO2 release system.
Feasibility of a 747-400F retrofit
According to theAeroTEC study, an unmodified 747-400F would likely be able to carry 50 tons of material to 15 km. Re-winging this type of aircraft, a relatively straightforward process, would increase the payload to 80 tons. This also would come with the added benefit of reaching 16 km and increased SAI efficiency. The AeroTEC study found that the cost for this process for 10 planes would be a little less than $1 billion dollars, with better value expected with larger quantities Given that this was a single, preliminary study, there does exist some uncertainty. Additionally, there are two specific sources of uncertainty. As mentioned above, given that these aircraft are no longer in production, procurement may prove difficult. That being said, using an estimate of a 1Mt/year payload, only 6 aircraft would be required if they each carry 75 tons. Second, the AeroTEC study did not consider engine flame-out, which may reduce the ability to reach higher altitudes.
References
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