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Comment by twic | Hacker News Reader

I do wonder if there's a way to reuse engines without reusing whole rockets, that could wind up cheaper. Pop the engine out of the rocket with some small fuel tanks, spin round and do a retro burn, then ... somehow land. I have not worked out all the details.

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ULA calls this "SMART reuse" but has not yet successfully achieved it with their Vulcan rocket.

https://planetary.s3.amazonaws.com/web/assets/pictures/_2400...

In some ways this is simpler, but in others it is more complex since you need a way to catch the engines before they dunk in the salt water. A rocket booster that is already set up with avionics, engines, and fuel can guide and land itself without needing a precise helicopter catch etc.

I'm not sure how leaving the rest of the booster would make a propulsive landing easier. It seems like more complexity than just leaving some fuel in the tank, for less benefit. But ULA's Vulcan (which incidentally uses the same BE-4 engine as New Glenn) plans on using a helicopter to catch it's engines as they parachute down [1]

[1] https://www.planetary.org/space-images/smart

This concept is generally known as "Stage-and-a-half", and it was used on the Atlas rockets

As Diane Rehm once lamented on her radio show about two decades ago, as she was interviewing some cutting-edge engineer about his work, “why does it have to be so haaaard?!?”

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