This has been the most difficult of these specials to put together, chiefly because many of the really cool spacecraft proposals of the 1970s and earlier never got beyond a few drawings. Science fiction is filled with spacecraft and spaceships, but most of them work using magic science and technology. Serious attempts at either reaching orbit cheaply and easily or travelling further than Low Earth Orbit are few and far between. To date, only eight crewed spacecraft have ever reached orbit or beyond – Vostok, Voskhod, Soyuz, Mercury, Gemini, Apollo, Space Shuttle and Shenzhou. A further twelve are in development or have been proposed.
There have been numerous plans in the past to expand on existing space programmes, or start up new ones. Some were by the military, others were civilian, and some proposals came from aerospace manufacturers. Of the ten space craft below, only two have flown in orbit and another two ever left the ground. Most never made it off the drawing-board. At least one of them I suspect was never intended seriously, although if you look online you can find models of it. Only one is still flying, and two went on to found follow-up projects which are currently ongoing.
Apollo Command/Service Module
Orbital and cislunar spacecraft (USA)
crew 3
mass 30,332 kg
payload n/a
proposed 1961
status flew 15 crewed missions
Hyperion SSTO
Proposed Single-Stage-to-Orbit launch vehicle (USA)
crew unknown
mass 470,000 kg
payload 18,100 kg
proposed 1968
status study only
Soyuz
Orbital spacecraft (USSR/Russia)
crew 3
mass 7,150 kg
payload n/a
proposed 1963
status still flying
Boeing X-20 Dynasoar
Orbital spaceplane (USA)
crew 1
mass 5,165 kg
payload n/a
proposed 1957
status cancelled after mock-up was built
Mikoyan Spiral 50-50
Orbital spaceplane and launch aircraft (USSR)
crew 1
mass 115,000 kg
payload unknown
proposed 1960
status cancelled in 1978 after single subsonic test article built and flown
HOTOL
Proposed Single-Stage-to-Orbit launch vehicle (GB)
crew unmanned
mass 250,000 kg
payload 8,000 kg
proposed 1982
status government funding withdrawn in 1988, restarted privately as Skylon
Northrop HL-10
Lifting Body research aircraft (USA)
crew 1
mass 2,721 kg
payload n/a
proposed 1966
status flew 37 test flights but never reached higher than 26,726 m altitude
Project Aldebaran
Proposed Single-Stage-to-Orbit launch vehicle (USA)
crew unknown
mass 50,000,000 kg
payload 27,000,000 kg
proposed 1965
status appeared in the book Beyond Tomorrow by Dandridge Cole (1965, Amherst Press)
Project Daedalus
Interstellar probe (GB)
crew none
mass 1st stage 1,690,000 kg, 2nd stage 980,000,000 kg
payload 450,000,000 kg
proposed 1973
status a new study, Project Icarus, for a crewed version is currently underway
Project Orion
Proposed Nuclear-propelled Single-Stage-to-Orbit launch vehicle (USA)
crew unknown
mass 800,000 kg
payload 300,000 kg
proposed 1958
status study only
It Doesn't Have To Be Right... 
October 15, 2012 at 12:10 pm
Yeah, these are more the “what ifs” and “What might have beens”. Alas.