The Antares rocket uses, or is about to use, NK-33 engines recovered from the N1 program. The reason these engines are so efficient is that they are closed loop

The Antares rocket uses, or is about to use, NK-33 engines recovered from the N1 program. The reason these engines are so efficient is that they are closed loop. But that doesn't mean they are overall cost efficient. Of course when you're going beyond orbit the calculations change. http://en.wikipedia.org/wiki/Staged_combustion_cycle_(rocket) http://en.wikipedia.org/wiki/Staged_combustion_cycle_(rocket... http://www.orbital.com/Antares/ http://www.orbital.com/Antares/