specific impulse


: the thrust produced per unit rate of consumption of the propellant that is usually expressed in pounds of thrust per pound of propellant used per second and that is a measure of the efficiency of a rocket engine

Examples of specific impulse in a Sentence

Recent Examples on the Web Chemical rockets in the 1960s had a specific impulse anywhere between 300 to 450 seconds. Amy Shira Teitel, Discover Magazine, 28 Mar. 2019 Thrust is measured in specific impulse. Amy Shira Teitel, Discover Magazine, 28 Mar. 2019 There were problems developing the science payload and the R-7 was proving to be less powerful with a lower specific impulse than anticipated. Amy Shira Teitel, Discover Magazine, 4 Oct. 2017 The higher the seconds of specific impulse the more economic and efficient the rocket. Amy Shira Teitel, Discover Magazine, 28 Mar. 2019 Dividing the impulse by the weight of the rocket gives the specific impulse. Rhett Allain, Wired, 25 Feb. 2022 Meanwhile, the Air Force will get data on measurements of specific impulse, or ISP, combustion stability, vibration and shock profiles, and range of inlet pressures and temperatures. Eric Berger, Ars Technica, 2 Sep. 2022 One way to describe the performance of a rocket is with the specific impulse. Rhett Allain, Wired, 25 Feb. 2022 This would be a monumental achievement given that the world-record specific impulse—held by NASA—is 542 seconds, and most operating orbital rockets have specific impulses around 300 seconds. Daniel Oberhaus, Ars Technica, 27 June 2020

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'specific impulse.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History

First Known Use

1947, in the meaning defined above

Time Traveler
The first known use of specific impulse was in 1947

Dictionary Entries Near specific impulse

Cite this Entry

“Specific impulse.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/specific%20impulse. Accessed 18 Jul. 2024.

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