pstarr wrote:You must believe it will be cheaper to retrieve a 1st-stage booster hundreds of miles offshore . . . than to simply let it drop into the ocean? NASA and John Glenn also had access to gyroscopes, accelerators, and GPS . . . and they beg to differ.
Actually in 1968 NASA had two competing system designs, one to return and reuse the first stage and one to build a glider capsule for the crew to ride in and reuse that capsule. After two years the Nixon Administration told them they had to pick one system because they would not get funding for both, and that they should try and get the USAF involved to pay part of the development costs. For those reasons NASA picked the reusable crew vehicle concept and then they had to more than quadruple its size to fit the USAF launch requirements from Vandenberg, California for polar spy satellite launch with landing after one orbit back at Edwards USAF base in California. The resulting Frankenstein creation became what we know as the STS aka Space Shuttle aka Space transport System that was never good for any of its stated roles and was never even launched from Vandenberg after USAF got permission to withdraw support post Challenger Disaster of January 1986.
If NASA had gone with the reusable first stage booster concept instead you would probably be arguing we had wasted the last 40 years because we didn't build the Space Shuttle instead. The physics are pretty simple, returning a first stage to the launch site as a 'fly back booster' is at least one order of magnitude easier than retrieving the capsule, which is the last stage and the portion that takes the greatest stress to return to Earth in reusable form.
It is also a blatant lie for anyone at NASA to say any part of the STS system was 'Reusable'. Not one part of that system was able to be put back into launch rotation without massive maintenance being done first. The SSME rockets were not even left on the orbiter for another flight, they were detached and completely disassembled and rebuilt while a different already refurbished set were installed on the vehicle they were detached from. In the same way every single one of the tens thousand tiles had to be individually inspected and any with the slightest flaw were painstakingly removed and replaced with a brand new custom made replacement tile. The manuvering engines had to be removed and refurbished as well as the attitude control rockets because they used highly corrosive fuels and oxidizers requiring not only a purge but a complete strip down and refurbishing after every flight.
In comparison SpaceX has designed a system with a flyback booster first stage, though in their case it is pure computer piloted instead of a human astronaut. They also chose the vertical take off and landing which is trickier than the vertical take off horizontal landing system, but pogo landing gear are much lighter and easier to deploy than wheeled landing gear so once DC-X proved it could be done in 1994 it is not a real surprise they adopted it for themselves in 2014. After all 20 years of improved computer power and material understanding makes the 'leap' to vertical pogo landing of a stage more of a small step than a great leap. SpaceX deliberately designed the engines for their launcher to use an ablative liner, meaning for any flight less than a max performance effort the rockets can simply get a fresh coat of liner material and in theory at least, be ready for the next flight. This is a far cry from the NASA SSME that had to be completely disassembled and rebuilt to exceedingly fine tolerances to work properly on a subsequent flight, and they didn't always do so even after a complete rebuilding. On more than one occasion an SSME failed to light causing a pad launch abort to take place.