QR:

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   The lower heating value for fuels.
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   Form:
   qR = QR( fuel )
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   ------
   Inputs
   ------
   fuel         (1,:)     Fuel string

   -------
   Outputs
   -------
   qR           (1,1)     Lower heating value (J/kg)

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Children:

Propulsion: Chemical/QRHydrocarbon
Propulsion: Chemical/QRHydrogen