[perihelions]

That's still much less than the aluminum from solid rockets, which have been ongoing since the 1970's. Per your own link,

> "In situ measurements showed evidence of a 1,000% increase in stratospheric aluminum levels from 1976 to 1984 (Zolensky et al., 1989), which was associated with the emission of hundreds of tons of such particles from solid rocket motors (SRM) during atmospheric ascent (Brady et al., 1994)"

If you follow Brady et al. (1994)[0], you'll read that every Space Shuttle launch (Table 1) deposited 112 tons of Al2O3 into the stratosphere (>15 km).

[0] https://apps.dtic.mil/sti/pdfs/ADA289852.pdf

This isn't a new phenomenon at all; in fact the peak alumina pollution from in the past (112 tons per STS launch) exceeds the worst-case future estimates from academic research (360 tons per year from satellite reentries).

(/meta Coincidentally, I once linked that exact Brady paper on HN, three years ago[1]. Actually, long before the current social media fad for being concerned about satellites. At the time I wrote, and this has truly aged well, "No one ever gave a shit").

[1] https://news.ycombinator.com/item?id=34812863

[schiffern]

As I understand it, the concern is not just AlO but specifically nanoparticles with high reaction surface area and long lofting lifespans.

The importance of this distinction is acknowledged in Brady et al (1994):

  >The exact chemical nature, as well as size distribution (and total surface area) of particles formed in rocket exhaust in the stratosphere is currently unknown. Preliminary experiments at Aerospace by L. R. Martin indicate that plausible particle compositions give highly variable rates of direct ozone destruction.

The 17 t/year and 360 t/year figures are specifically for AlO nanoparticles (formed by hypersonic ablation), whereas Brady et al gives numbers for all AlO particles, regardless of size.

Nice username btw.