When I try dropping an Ion Cannon into the Rocket Silo cargo slot while rocket is still building (no launcher ready), a text pops up:
"There is no point sending Ion Cannon to orbit"

can you send anything other? like a fish?

Sorry just noticed your reply. I can send a satellite, I'll try sending a fish.

Update: I have no problems dropping a fish in the cargo slot of the rocket.

Unfortunately I have not found anything in the API on how to remove the filter
may by you can do also a bit research on forum, google etc.. pls

Okay.

Just an update: I can put fish into the rocket's cargo slot, but the rocket can't launch. At least, not automatically (did not try to press the launch button).

fixed

P.S.
Send the fish, it's an achievement ;-) if you don't have it yet

Yay, it works now! Thanks!!

Also got the achievement, thanks for that as well 😄