Multi Grain Different Bore Sizes

[rxckitralph]

Newbie question. Would this idea potentially work?? A 3 stage multi grain motor per say. The bottom most being larger bore for higher thrust slowing dissipating to a smaller bore hoping for a slower burn rate. Summed up, would the burn rate throughout each grain of propellant vary or will it all ignite at once??

 

[prfesser]

Questions involving motor making are generally relegated to the Research forum. See here for requirements to access the forum.

 

[Zeus-cat]

I used to have diagrams of different bore configurations that I got from Magnum Rockets years ago. Many interesting patterns such as 8 point or maybe 10 point star, semi-circular core, etc. The star patterns created very high initial thrust as so much grain was exposed at the start of the burn and then it tapered off to a more moderate thrust. I'll look for the diagrams, but it has been years since I have seen it.

 

[rxckitralph]

I used to have diagrams of different bore configurations that I got from Magnum Rockets years ago. Many interesting patterns such as 8 point or maybe 10 point star, semi-circular core, etc. The star patterns created very high initial thrust as so much grain was exposed at the start of the burn and then it tapered off to a more moderate thrust. I'll look for the diagrams, but it has been years since I have seen it.



I appreciate it!!

 

[Banzai88]

Nothing that you asked can't be answered by searching out the grain geometry of existing dual thrust motors on the RCS web site.

 

[boatgeek]

I believe that Loki also steps core diameters on some motors.

 

[rxckitralph]

Nothing that you asked can't be answered by searching out the grain geometry of existing dual thrust motors on the RCS web site.



"Dual thrust motors" those were the wo

 

[tim cubbedge]

I believe that Loki also steps core diameters on some motors.

That’s correct. All of the cocktail motors are step core.

 

[rocket_troy]

I developed and tested a core config like that in the late 90s to suppress erosive burning. 6 grain though, but produced a neutral profile that was almost indistinguishable from a standard BATES profile. Worked well on the test stand.

TP

 

[rxckitralph]

Thanks for the much needed info! i was thinking that the whole core would combust and somewhat burn at the same rate, instead of each individual grain.

 

[sharkbait]

Thanks for the much needed info! i was thinking that the whole core would combust and somewhat burn at the same rate, instead of each individual grain.

The grains burn from the inside (core) outwards and from the top down and bottom up at the same time, unless you inhibit one or both ends. If the formula of all the grains is the same, the burning rate is influenced by the amount of burning surface exposed

 

[shockie]

Newbie question. Would this idea potentially work?? A 3 stage multi grain motor per say. The bottom most being larger bore for higher thrust slowing dissipating to a smaller bore hoping for a slower burn rate. Summed up, would the burn rate throughout each grain of propellant vary or will it all ignite at once??

Kinda looks like an exaggerated Estes B3 core.(B16) or B14