(21118) Hezimmermann = 1992 SB17 Helmut Zimmermann (b. 1926), director of Jena University Observatory from 1969 to 1978, worked on the interstellar radiation field and cloud collisions. He was the integrating figure in the new study course of astronomy for student teachers in Germany. The citation was prepared by W. Pfau.
A complete set of naming citations of the numbered minor planets is available in the Dictionary of Minor Planet Names, edited by Lutz Schmadel.