luke strawwalker
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Quite correct...
Antares is something of a kludge anyway... Russian engines (although they are quite high performance) on a liquid first stage with a solid propellant ATK second stage, and Cygnus is basically a disposable pressurized tin can for delivering stuff to ISS, designed to burn up on reentry into the atmosphere, not for recovery, unlike the SpaceX Dragon...
Basically Antares was the cheapest way possible for Orbital Sciences to get and fulfill a COTS contract for ISS resupply. It's very much a "one trick pony" and not really flexible or certainly not optimized at any rate for any other mission than delivering Cygnus to LEO. The solid propellant second stage is just about THE most inefficient way of delivering payload to orbit, but it has one benefit-- it's a "cheap and dirty" solution.
Think of it this way... SpaceX took the opportunity presented by the COTS competition and contracts to develop what is basically an updated version of the Saturn IB... (9 smallish first stage engines and single engine liquid upper stage, although of course Falcon 9 uses a kerosene powered upper stage, which is not anywhere near as efficient as the hydrogen powered upper stages used on Saturn I or IB, or Centaur hydrogen powered stages or the Delta Cryogenic Upper Stage... but even a kerosene powered upper stage is more efficient than a heavy, low ISP solid propellant upper stage). They also took the opportunity to develop a spacecraft that could not only serve as an unmanned cargo delivery module, but which could reenter and land, delivering cargo back down to Earth and even perhaps be reused.
Orbital, on the other hand, looked around for as much cheap "off the shelf" stuff they could get and cobble together into a COTS launch vehicle, hence the Russian engines (and IIRC large parts of the first stage are built in Europe and integrated in Russia) and the ATK solid propellant upper stage. Basically they chose to recreate the Jupiter or Juno launch vehicles from the late 50's-- converted Redstone or Thor liquid propellant first stages lofting cobbled together solid propellant upper stages capable of lofting the desired payloads, but not really flexible enough to grow into launching anything else in any other role... Inefficient, but "powerful enough" to get the job done... Similarly, they didn't develop a spacecraft that was adaptable to being "upgraded" into a manned spacecraft-- it's basically a recreation of the Progress freighter (only without the tanker capabilities for propellant transfer in orbit... just a pressurized can to deliver cargo... although Progress was basically a redesign of the Soyuz capsule, so it's actually a "derated derivative" of Soyuz). Upgrading the Cygnus into any sort of manned spacecraft would basically require essentially a complete redesign...
Antares and Cygnus are capable of fulfilling the COTS contract for which they were designed, and while it's possible they could be adapted or redesigned for other purposes, it's just as likely that once that contract is fulfilled, both will simply disappear and not "evolve" into any other kind of spacecraft or launch vehicle...
Later! OL JR
