Heineken wrote:dissident, I carefully qualified in my post that the idea is crazy. I fully acknowledge that. Desperate times call for crazy stabs at solutions. The idea would be to find some way to inject massive amounts of fine dust high into the upper stratosphere, where the dwell time would be considerable. Maybe there's some way to do that. There are worse ways to waste our money.
People who know me know I am not a fan of giant geoengineering projects, but this is one that might be worth at least investigating.
HARP project technology would allow as much crud to be dumped high up as you want, not that I want anyone playing geoengineer.
Started in 1961, it was created largely due to lobbying from Gerald Bull, a controversial but highly successful ballistics engineer who went on to head the project. Bull had developed the high-speed gun technique while working on anti-ballistic missile (ABM) research at CARDE in the 1950s, shooting models of high-speed interceptor missiles from guns as opposed to building supersonic wind tunnels, which would be much more expensive. The ABM project eventually ended without delivering a working system, but Bull was convinced the rocket systems he had developed had potential and started looking for other ways to use the technology.
HARP was such a development. The U.S. was in the process of testing newer ICBM systems and required repeated tests of newer re-entry vehicles. Bull suggested that the program could be run for considerably less money if the test vehicles were lofted from a large gun, as opposed to using rockets. This would also allow the test program to be greatly sped up, as repeated firing was easy to arrange in comparison to setting up rockets. The key concept was the use of an oversized gun firing an undersized vehicle mounted in a sabot, allowing it to be fired with relatively high acceleration. Test electronics were potted in a mix of sand and epoxy, proving more than capable of withstanding the rigors of launch.
The project was based on a flight range of the Seawell Airport in Barbados, from which shells were fired eastward toward the Atlantic Ocean. Using an old U.S. Navy 16 inch (406 mm) 50 caliber gun (20 m), later extended to 100 caliber (40 m), the team was able to fire a 180 kilogram slug at 3600 meters per second, reaching an altitude of 180 kilometers. The program was cancelled shortly after this. The politics of the Vietnam War (then in its fifth year) and soured Canada/U.S. relations played their role in the project's cancellation. The project received just over 10 million dollars during its lifetime.
Bull's ultimate goal was to fire a payload into space from a gun, and many have suggested that the ballistics study was offered up simply to gain funding. While the speed was not nearly enough to reach orbit (just 32% of Earth's 11.2 km/s escape velocity), it was a major achievement at much lower cost than most ballistic missile programs.
Project HARP wiki
The whole point is, a ballistic launch device could place any dust type you want from Flour to Sodium high into the atmosphere with a simple bursting charge at the desired altitude. I think mankind is nuts to even consider geoengineering, but the technology to play these God games is old and well known. Even the Paris Gun of WW I fame had a high enough trajectory to do this in 1916.
Paris Gun
I can see it in my minds eye, potassium nitrate needed for fertilizer divberted to miles of artillery pieces firing day and night to put dust above 25 miles where it takes decades to settle back to the ground. Brilliant, isn't it?