Solid Propellant Grain

[Zold]

I have a question,
what are example of rocket used progressive,regressive and neutral propellant grains?
when the above 3 propellant will be used?

 

[mbeels]

Here are some examples, Aerotech F39, Cessaroni H143, and Quest D16:

 

[Winston]

I have a question,
what are example of rocket used progressive,regressive and neutral propellant grains?
when the above 3 propellant will be used?

From:

CHAPTER 12
SOLID PROPELLANT ROCKET MOTOR FUNDAMENTALS

https://wodeshu.gitee.io/roprop/text00015.html

 

[cbrarick]

most motors are set up neutral, consistent thrust throughout the burn
regressive is used for big kick off the pad.
progressive - generally not used, but long burn progressive motors may benefit altitude seekers.

All the patterns you see above aren't used by most motor makers

And the concept is wrong, although a core pattern may lend itself to the type of motor, the grain geometry is much, much more important.
I'm guilty of a sharp punch off the pad, so I enjoy a somewhat regressive motor...and all my grains are BATES. (second from top)
end burning is infrequently used for long burn motors....
I've seen star grains used for volume loading not burn characteristics. (rare, difficult to make)
the rest I've never seen, but please understand I'm not the expert here.

 

[rocket_troy]

I’d say most motors deliver a regressive profile. Regressive profiles are generally optimal for altitude as you often want the longest burn time possible to minimize peak velocity and max drag. Of course there can be exceptions to this, but generally, for a bog-standard single stage flight, regressive is optimal to both get you going fast enough at launch but to not over-speed towards the end of the burn.

Progressive profiles can seem advantageous for very highly volumetrically loaded motors that might inherently experience an erosive burning spike at start-up ie. the peak at the end can be designed to be relatively comparable to the spike at the start thereby keeping the chamber pressure somewhat more neutral overall, but closer analysis often produces sub-optimal models for progressive profiles.

End burners are infrequently used for HPR and up as they generally struggle to produce enough thrust ie. they’re fine for small motors but as you increase the motor length (which generally scales with size) you need to likewise up the burn rate of the propellant to maintain the same T:W

Star and Finocyl core geometries are generally implemented for their burn profile with the ultimate objective of increasing the volumetric loadings ie. they’re often implemented to enable case-bonding of the propellant thereby alleviate the requirement of the liner(s). Their geometry is generally tailored to provide a neutral(ish) or regressive profile with minimal sliver fraction at the end so the casing wall has minimal exposure to the chamber energy.