I'm lazy, so if anyone has one, please post.

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I saw this beautiful girl on the bus, but she looked sad. I asked her what was wrong. She said, "Well, my analyst said I'm a nymphomaniac, but I only like Jewish cowboys... by the way, my name is Dianne." I said, "Hello, Dianne. My name is Bucky Goldstein." - Steven Wright

Never mind on the title request.

I already built this YEARS ago and just simmed it today after creating a "good enough" (i.e., not internally detailed perfectly) Rocksim model to approximate flight performance and safety.

Estes 29mm BP motor propelled models can be sluggish off the launch pad because of the slow rise of the thrust curve, so I added pods to the booster to give a decent departure velocity off of a 48" launch rod.

To keep it an FAA Class 1 Model Rocket - no more than 125g of propellant - the booster has a central E16-0 with a C11-3 and C11-5 in the pods (although it's simmed with plugged C11s), and an F15-8 in the sustainer. The pod parachutes eject at different times to hopefully avoid tangling.

The total empty mass and CG for both the sustainer and booster were measured individually and entered manually.

I haven't launched it yet and when I eventually do it will be on a huge launch field in the middle of nowhere at a much greater distance from launch control than required by safety guidelines. The rocket will be positioned on the pad so that an ignition of only one pod will arc the rocket perpendicular to the line from the pad to launch control.

Attached Thumbnails

 

Attached Files

Estes 9707 Majestic with custom 9752 booster with pods.rkt (65.5 KB, 22 views)

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I saw this beautiful girl on the bus, but she looked sad. I asked her what was wrong. She said, "Well, my analyst said I'm a nymphomaniac, but I only like Jewish cowboys... by the way, my name is Dianne." I said, "Hello, Dianne. My name is Bucky Goldstein." - Steven Wright

Seems like that should be enough thrust to get it going off the pad. I can attest that an F15-0 to F15-8 in one of those is not enough speed off a 5' rod. I flew one and it staged nearly horizontally. Never saw it again, though it was entertaining.

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Paul
If we weren't all crazy, we would go insane - Jimmy Buffett
NAR #87246 www.wooshrocketry.org

With those pods the sim says 38 fps off of a 4 ft rod which is close enough to the rule of thumb 40 fps.

I've flown that combo with an E16-0 (different booster with no pods) to F15-8 on a 4 ft rod, but luckily it was dead calm on launch day which I'd made a requirement to launch it. Went straight up and was very impressive.

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I saw this beautiful girl on the bus, but she looked sad. I asked her what was wrong. She said, "Well, my analyst said I'm a nymphomaniac, but I only like Jewish cowboys... by the way, my name is Dianne." I said, "Hello, Dianne. My name is Bucky Goldstein." - Steven Wright

I've seen anecdata (launch reports on the other forum) suggesting the Majestic may be marginally stable by itself. My hypothesis is that skinnying the fins up to make them more or less triangular gives away too much area compared to the fins on the Ascender, which AFAIK are the same as those on the booster. I bought a couple of those fin cans and some of the 2-inch tube before Estes closed it out that will be combined into single stage rockets when I get around to it.

The Rocksim file for the Majestic (without booster) which I believe I got from:

https://www.rocketreviews.com/rocks...x-majestic.html

shows an "overstable" 2.57 stability margin with an F15-6 loaded.

Attached is an image of the issue. Rule of thumb, if I recall correctly, for safe rod departure is 40 fps. Note where that velocity is obtained in the simulation with an Estes F15. The 29mm Estes BP motors have a very slow thrust buildup.

However, the launch details indicate "Velocity at launch guide departure: 31.7952 ft/s" for a 4 foot rod. That doesn't seem to match the graphed velocity versus altitude plot.

Attached Thumbnails

 

__________________
I saw this beautiful girl on the bus, but she looked sad. I asked her what was wrong. She said, "Well, my analyst said I'm a nymphomaniac, but I only like Jewish cowboys... by the way, my name is Dianne." I said, "Hello, Dianne. My name is Bucky Goldstein." - Steven Wright

Makes sense.

Not trying to make it a point of contention, but the number I remember seeming to be general consensus for safe departure speed is

15 m/sec
=49.2 ft/sec
=33.6 mph

I try to set up my sims to run 17 m/sec or faster off the rod.

32.8 ft/sec = 10 m/sec

Guess I'll be sticking to composites for my Estes tube 2-inch builds. And almost certainly making them shorter, lighter and a little less overstable to resist weathercocking.

Yep, through a search I've found 30 mph which converts to 45 fps, not found in the NAR or Tripoli safety codes (that I have on hand, anyway), but in a few cases like this one specified for high power flights at the Johnson Space Center:

Other requirements are that a rocket achieve at least 30 mph (45 fps) off the launch guide, and stability margins must be between .75 and 5.0 Calibers

Of course, the greatest factors in the safe departure velocity are crosswinds and stability factors which is why my two stage Majestic managed to go strait up in dead calm air.

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I saw this beautiful girl on the bus, but she looked sad. I asked her what was wrong. She said, "Well, my analyst said I'm a nymphomaniac, but I only like Jewish cowboys... by the way, my name is Dianne." I said, "Hello, Dianne. My name is Bucky Goldstein." - Steven Wright