Aren't older TTL more resistant to radiation because of physically large chip structures? It could be that those chips were already space-tested or radiation-hardened.
yeah, I believe it should be something like that. Anyways I think the author created some anticipation of giving an explanation about the reason of all those chips and the conclusion was just something like "there are many ICs because it uses TTL and each TTL IC doesn't do much so you need many of them". Ok... but why does it use TTL? that's the interesting question, isn't it?