Stack Exchange network consists of 176 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.
Is this going to be similar to Astronomy & Astrophysics.
Proposal: Space Exploration
It seems to me that this SE is geared more towards space and space exploration as whole. Astronomy & Astrophysics are very specific fields, while they do share similar areas, this is a more generalized discussion about space and space travel.
They do appear to be similar, but I think that they are enough different that both will succeed. (Well, I am not sure that Space Exploration would succeed anyway, but only time will tell.)
SpaceX (this site, not that company) will take some time to succeed, if it ever comes to that...