Only the weather as the cause of DP9's death does not fit with this statement by Ivanov:
„The true causes of the deaths were hidden from the people, and only a few knew these reasons: the former first secretary of the regional committee A.P. Kirilenko, the second secretary of the regional committee A.F. Eshtokin, the regional prosecutor N. I. Klimov and the author of these lines, who were investigating the case“
And the rocket theory does not correspond to these words of Ivanov:
„Someone needed to frighten or punish people, or show their strength, and they did this, killing three people“.
Conclusion:
So there was something to hide, but it wasn't rockets.