The latter doesn't have any very recent news, so I was left wondering what exactly the submitter was expecting us to discuss... Though I would be up for discussing the 2nd part of their blog post on Rocket Design: http://copsub.com/how-to-design-a-space-rocket-step-23/
What prompted the change? HN prefers original sources, and stories consisting (nearly) entirely of pictures tend to be treated as lightweight. The site has worked this way for years.
We changed the link back in this case.