  The Flyback F-1 is a flyback version of the Saturn V's S-IC first stage. (Also included as a bonus: an ordinary, non-flyback S-IC stage).
  The Flyback F-1 can be used as a CVEL launcher, or can use an attach point to loft payloads not suitable for CVEL.
  The Flyback F-1 can also be used in parallel with the payload, rather than just carrying a passive payload. By employing the F-1 engines with the attached stage, the Flyback F-1 can act as a parallel-burn stage on core vehicles not designed for it.
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