Question: Who flew on more Space Shuttle missions, meteorologist Piers Sellers or chemical engineer Lodewijk van den Berg?
Sentence (from "STS-3xx"): Space Shuttle missions designated STS-3xx (officially called Launch On Need (LON) missions) were rescue missions which would have been mounted to rescue the crew of a Space Shuttle if their vehicle was damaged and deemed unable to make a successful reentry.
Relevant evidence: No