Wow...perhaps program it to feedback from an accelerometer with a moveable plug type nozzle? That would max performance over a much wider speed range.

A gate valve from the top over the eliptical opening would do the trick and the new low mass high power actuators being used in micro RPV's would do just the trick with a low drag valve.

Note I didn't repost the link to the California Rocketry magazine article on ramjets, because frankly it was bogus. Its only value was the math. Simpleton math at that. It was great for interest and circulation however. Ratings driving content.

Tech Jerry

OK.... yes that would be simpler to fabricate. Did a couple small 3" dia air augmented rockets a couple years ago to play with the concept on the cheap. Try stuffing a motor up inside a small tube like that was a PIA had to fab a couple tools to do it and install the retainer. Over time I core sampled both of them but learned a lot about augmented nozzle sizing in the process. Thinking about 6" dia 123mm type hardware augmented tube which will be much easier to load primary motor(s) up the arse. Single motors have such a short burn time I am looking at a cluster of long burn smokey sams with a large primary central boost motor with smaller dia motors clustered (expanded nozzle holes for rich burn) around it for air start and sustained burn time. By the time the second primary's air start it should be in the mach+ range providing good compression from the diffuser section for ignition of the unburnt gasses in the augmented tube. Looking at Lil Augie style 4" or 5" dia upper to 6" dia lower augmented tube to KISS. Need to aim shock at inlet lip around M1.4. Would have shock ramp ring attached around the upper airframe just ahead of the 6" dia inlet lip.

The Rc controlled inlet would work on a more exotic design like a ASLAM missile. Augmented opens up new realm in model rocket design potential. With the motors up near the CG/CP location fins can be smaller.

Chuck Rogers did a couple HPR articles years ago on augmented rocket designs. Can not find the issues or remember the years/month.

Not HPR it was California Rocketry Magazine July (p6) and October 1982 (p9-11) issues.

http://v-serv.com/crp/CRm/10-82/CRm.10-82.htm

http://v-serv.com/crp/CRm/7-82/CRm.7-82.htm

Wow--I'm glad to see this thread get picked up & added to--I've got some interesting reading & viewing to do...Thank You, All! This will be a real treat to delve into after my observation of the unicorn-inspired, forest-related holiday that humans call by various names...

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Attached a few pics of my central spike inlet augmented designs both 3" diameter and the larger 6" diameter. Both had diffuser sections which would not be required and just add drag for a simple fanno-flo based subsonic design. However the larger 6" dia model is a mach+ capable design with provision for insertion of an aluminum tube to support augmented combustion. I flew the diffuser in the small model to gain some data and feedback on diffuser design and inlet/combustion chamber/nozzle area ratio's. Center nose inlets tend to add to stability similar to a tube fin requiring even smaller fins.

The 3D central spike inlet diffuser design has some fabrication issues and I plan to try a single chin 2D inlet designs like on the F-16 in the future. Also the 2D design allows for easy redirecting of the boundary layer flow away from the inlet.

One advantage of ducted rocket designs is having the motors located near the CG/CP location which allow for reduced nose weight requirement. So there are pro's and cons to augmented designs some areas that add weight and drag others that reduce, same for thrust. Bottom-line a well designed ducted rocket can fly well with near the same performance as a standard model rocket design and have some cool added features.

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Happening at Lucerne of course.

Of course.... one of my favorite extreme rocket playgrounds.

A variable nozzle could be made with the same principal as a Chinese finger puzzle and the components some variant of CF and Kevlar. Nozzle throat diameter is far more critical than the particular shape of the convergent or divergent.

Seems the Ruskies have developed one for JetCat turbines:

http://www.youtube.com/watch?v=5Uhs8ZHIDgw

Pual Ivie designed and fabricated one for ducted fan jets back in the 1990's. Bob Fiorenza and BVM also flew a DF with one not sue if it was a Ivie design not sure what became of them.

Attached patient of Ivie design and cover page of instruction book.

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Paul Ivie Variable Nozzle.pdf (155.0 KB, 58 views)