I get asked this question every once in a while and I finally got some free time over Christmas break to try and track an answer down. I quickly found a NASA brochure online titled “International Space Station Utilization Statistics Expedition 0 – 44 December 1998 – September 2015” . Seemed like a good place to start and right on the first page I found this:
Easy peasy. “Total investigations from ISS Expeditions 0-44 is 2,060.” There. Finally, an answer I can give those who ask. But is an “investigation” the same as a payload? They give the definition of investigation in the paragraph above the table, but it’s kind of loose and doesn’t really say something is specifically a physical research payload or not.
NASA also maintains a website with a list of experiments by expedition (and a few other categories) and I thought of comparing the number of payloads on that site to the number above. After some Excel wrangling I came up with the following:
Example of raw data from NASA site. Pink cells indicate duplicate entry. Using these data, the total number of payloads (red circle) is 3, 818 since Expedition 0 in 2000. ...