31. Confusingly, both values are sometimes called specific impulse . 32. Xylitol and KNO 3 based rocket propellants are capable of a specific impulse of ~ 100 seconds. 33. The " specific impulse " is the most important metric for the efficiency of a rocket engine. 34. The Orion concept offered high thrust and high specific impulse , or propellant efficiency, at the same time. 35. It has a relatively high monopropellant specific impulse of 177 seconds ( 1.7 kN�s / kg ). 36. It was previously mentioned that the specific impulse could be as high as or higher than 3000 s. 37. These are best-possible specific impulse calculations. 38. Both provide very high specific impulse but relatively low thrust, compared to the more typical chemical reaction rockets. 39. The vacuum version, with a vacuum optimized nozzle shape, has a thrust of with a specific impulse of. 40. Liquid systems enable higher specific impulse than solids and hybrid rocket engines and can provide very high tankage efficiency.
