A follow up to Why does the Star-5A have such a bad mass ratio? A comment left by @RussellBorogove says

...the Star-5A is extremely small, at 4.6kg. At that size, the usual observed scaling relationships for larger rockets don't apply -- in short, the proportional contribution of the metal casing to the total mass is much higher than it would be for a multi-ton motor.

Having a kick motor that small doesn't really make sense. While alone without any extra weight, this motor has about 1765 m/s of delta-v. With a 50 kg or 100 kg payload, delta-v is drastically reduced to 110 and 56 m/s, respectively. Even a 10 kg payload gives 436 m/s. This isn't very useful except for CubeSats which usually find a ride along with a larger rocket as a secondary payload. So what exactly is the point of very low mass kick stages?

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    $\begingroup$ There obviously is a purpose otherwise nobody would have spent the development money in the first place, so the question in the title is trivial and unnecessarily clickbaity. Would you mind rewording it to "What is the purpose …?" or something along those lines? $\endgroup$
    – TooTea
    Aug 9, 2022 at 12:54
  • $\begingroup$ @OrganicMarble Why delete your answer? It seems like you're correct $\endgroup$
    – WarpPrime
    Aug 9, 2022 at 16:22
  • $\begingroup$ @fasterthanlight I wanted to finish it, I was trying to find out what its application on a shuttle payload was, and I forgot to come back. It probably flew on one of the classified shuttle missions that year, since I could not confirm which payload. Thanks for the reminder. $\endgroup$ Aug 9, 2022 at 21:49

1 Answer 1


It and the other members of the family of Star 5 motors are used as stage separation motors, or for other applications where relatively low thrust and high reliability are required.

Reference: http://www.astronautix.com/s/star5.html

enter image description here

A look at Northrop Grumman's catalog will show you that it isn't their smallest motor, either.



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