I saw this report SOLID ROCKET MOTOR DESIGN L-CLASS, here as shown in FIGURE-8, they have charged the motor with grain segments with spacer rings in between. Can`t we charge the motor without any segments, I mean directly loading the whole grain in the motor casing?figure 8

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    $\begingroup$ The diagram is slightly confusing, apparently the four 100mm sections come to 600mm long. I suspect instead they are 150mm segments, which is the same size used in their test engine (which used two). preparing the propellant in smaller batches makes it easier to handle and cast, and reduces the damage caused by a mishap. $\endgroup$
    – user20636
    May 30, 2019 at 11:55
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    $\begingroup$ Too many questions for one post. Please separate your questions and post them separately. $\endgroup$ May 30, 2019 at 11:59
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    $\begingroup$ Yes, please break this into its component parts. Some of the questions, like how to measure thrust, are pretty easy to answer. $\endgroup$
    – Roger
    May 30, 2019 at 14:06
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    $\begingroup$ The edit looks good, the question is clearer. This question should not be closed now. $\endgroup$
    – uhoh
    May 31, 2019 at 0:45
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    $\begingroup$ Close vote retracted after edit. $\endgroup$ May 31, 2019 at 3:01

1 Answer 1


One of the functions of spacer rings in smaller rockets (I have no experience of large ones) is to control erosion of the lower segments during the burn. Effectively, they keep gases from upper segments in the center of the channel as they pass down the stack of segments, allowing all the segments to burn consistently and burn out at about the same time.

  • $\begingroup$ So, What is the material used for making spacer rings such that they doesn't affect the flow of hot gas inside the case? $\endgroup$ May 31, 2019 at 15:06
  • $\begingroup$ Can you please tell me what is the material used for spacer rings. Thanks in Advance. $\endgroup$ Jun 13, 2019 at 15:27
  • $\begingroup$ Dunno. On a Phoenix missile (long time ago) they felt heavier than aluminum, but maybe lighter than steel, and had a light ceramic coating that was annoyingly fragile. $\endgroup$ Jun 14, 2019 at 1:52

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