Possibly of interest, the giant engines used in the Delta IV Heavy have 80% less part count than an SSME, but they were never intended to be human-rated: https://en.wikipedia.org/wiki/RS-68

Not that it has brought launch costs down much, considering how the ULA loves their juicy government contracts for billion dollar NSA/NRO satellite launches.

IIRC the Falcon 9 engine design is the opposite of an RS-68, which is the "one huge fucking engine" design philosophy, which is why a falcon9 has a cluster of many smaller engines and is tolerant of an individual engine failure during launch.

> IIRC the Falcon 9 engine design is the opposite of an RS-68, which is the "one huge fucking engine" design philosophy, which is why a falcon9 has a cluster of many smaller engines and is tolerant of an individual engine failure during launch.

Indeed! A Falcon 9 mission has lost an engine mid-flight, and the flight system adjusted the burn duration on the fly to compensate:

http://motherboard.vice.com/blog/spacex-s-non-fatal-failure

Also, every shuttle flight is human-rated. I would guess that SpaceX wouldn't use "refurbished" engines for manned flights, while they could cut down on the thoroughness of checks for lower value payloads.

That seems likely at first, but it'll be really exciting when that switches around and reused engines are the preferred choice for manned flights since they've been proven.

After all, you never put passengers on the very first flight of a new airliner. You test it out first, and then once it's demonstrated you start using it for real. We'll know that reusable rockets have really made it when the first flight of a new one is done as a test flight without risking any lives, and only afterwards is it put into normal use.

Plus for the orbiter refurb they had to check the entire heat shield, flight control systems, crew habitats, etc. etc. Easier when it's just the rocket + fuel tank.

Indeed. The heat shield in particular was extremely delicate and tended to get beaten up a lot coming back, so that was a huge amount of work to get ready for the next flight.

The entire spaceplane concept drastically complicated things. Capsule-based return systems are vastly simpler to operate, which is despite everything the Soyuz has been flying continuously this whole time.

Downside is you can't capture enemy satellites and return them to ground for study/reverse engineering.

This is how NASA got many billions of funding from the USAF for part of the space shuttle program - look through the list of flights in the 1980s where the payload was an unspecified national security satellite. The capability was promised and it was funded for it - but almost never used. The actual ability to grab a big thing and return it was hardly ever used, such as the LDEF mission. It doesn't help that a huge percentage of Soviet satellites that they might want to have grabbed would have been unreachable from a space shuttle launch site (IMINT satellites in 90 degree inclination polar orbits, satellites in molniya orbits, radar naval observation satellites in MEO orbits) all beyond the orbit/delta-V capabilities of a shuttle mission. And of course geostationary orbit where no human has ever gone.