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Home / Features / MIM104: Building a Direct Ducted CHAD-staged Patriot
MIM104: Building a Direct Ducted CHAD-staged Patriot Print E-mail PDF
Tech Tips Series by Dan Yaugo   
Sunday, June 12, 2011
Article Index
MIM104: Building a Direct Ducted CHAD-staged Patriot
1: The Engine Mount Construction
2: Air Duct Support Structure
3. Air Duct System Assembly
4. Mounting Recovery System
5. Air Frame Construction
6: Nose Cone Construction
7: Fin Construction and Mounting
8: Final Construction and Prep
9: Prep for Primer and Paint
10: Applying Primer and Paint
11: Finishing the MIM-104 Rocket

Welcome to the Rocketry Planet How-To Classroom!
ImageThe MIM-104 Patriot is a surface-to-air missile (SAM) system, the primary of its kind used by the United States Army and several allied nations. It is manufactured by the Raytheon Company of the United States.

The Patriot System replaced the Nike Hercules system as the U.S. Army's primary High to Medium Air Defense (HIMAD) system, and replaced the MIM-23 Hawk system as the U.S. Army's medium tactical air defense system. In addition to these roles, Patriot has been given the function of the U.S. Army's anti-ballistic missile (ABM) system, which is now Patriot's primary mission.

If you want more information about MIM Patriot missile click on the following link:

Estes came out with a model Patriot missile, which you can buy just about anywhere online and most hobby stores for around $16. This build is similar in some ways to the Estes version, but different in so many other ways.

This particular Patriot will fly on three 24mm black powder motors and exceed an altitude of around 2700 feet, compared to the standard Estes Patriot, which only flew on one 18mm (A-C) black powder motor and reached an maximum altitude of somewhere in the neighborhood of 600 feet. We will be using the direct staging method also known as C.H.A.D or CHeap And Dirty staging.

Figure 1 displays a technique we will cover in this build in the construction of an air duct system to allow the motors to "breathe or vent," which will also prevent the inside of the airframe from burning up and eliminate what is commonly called the "Krushnic Effect" see link below:

If you notice in Figures 2 and 3, you can see how the rocket motors are joined using cellophane tape and how they fit up into the airframe. The two booster motors are D12-0's and the upper main motor is an E9-8. As you ignite the motors they burn one by one and the flame of the ejection charge on the D12-0's ignite the motor on top. The flame is so hot that it easily melts away the tape and the spent motors drop out of the airframe and fall to the ground.

I built this design before using a three stage 18mm set up and had much success. I like this particular design because it eliminates the extra and materials needed to build booster stages and it cuts down on the weight of the rocket allowing it to fly higher. Also to watch each motor burn out and ignite one another is pretty spectacular. Figure 4 is a picture of the inside of the airframe with the E9-8 in place.

Figure 5 shows all the parts you will need to build this model rocket. I included two (red) BT-60 tube couplers that I had lying around, which are optional, but I may use one of them during this build. The only difference is that they are 1-1/2" in length whereas the plain ones are 2" in length. The parachute pictured is your standard Estes 24" plastic parachute. You can also use an 18" parachute, but it's a judgment call. I do a lot of launching at a dry lake bed, so the surface is harder than a grass field so I use the 24" parachute. Based on the Apogee RockSim file for this rocket the descent rate for a 24" plastic parachute is somewhere in the neighborhood 10.2782 ft/s or 7.0079 mph. The 18" parachute has a descent rate of 13.7043 ft/s or 9.3438 mph.

Another note: If you don't have Apogee's Rocksim, you can download a trial version from Apogee's website. Just go to and follow the instructions. This way you can run the simulations of this build and experiment and build many rockets on your own.

I purchased a full version awhile back and have been very satisfied with the software. You can design just about anything your imagination allows and it saves you time and money in the long run, by allowing you to build safe and flyable rockets. Well worth the investment!!

I would like to thank Tim Van Milligan, owner of Apogee Components, who offers a wide selection of rockets kits, rocket parts and instructional videos that make his website a cut above the rest! His service is exceptional, but it's the knowledge that you gain when you visit the site. From technical newsletters, how-to information, technical information and instructional videos you will be able to find it all at Apogee Components. In fact some of the build techniques that you see in this article, I gained from watching his advanced construction videos on his website. Mine may vary slightly, but not much. So if you get a chance visit his site.

I would also like to give a very special thanks to Darrell D. Mobley, Editor of Rocketry Planet, for recognizing the uniqueness of this rocket and asking me to write this article. I've decided to auction off this rocket and donate the proceeds to Rocketry Planet to help keep it alive and running.

Most online hobby stores carry the parts listed below.

Parts List:

  • Estes PNC - 60NA Nose Cone - (1)
  • BT-60 x 18" Body Tube - (2)
  • BT-50 (24mm) x 18" - (1)
  • Midwest Fin Stock 1/8" x 4" x 12" - (1)
  • Fiber Center Rings BT-50 to BT-60 - (2)
  • Center Ring / Engine Block BT-20 to BT-50 - (1)
  • BT-60 X 2" Tube Coupler - (2)
  • 100# Kevlar® Thread - 90"
  • 18" Mylar Parachute

In addition to the parts listed and pictured, you will need your basic tools and accessories. Most of the items listed below you should already have if you've been building rockets.

  • Hobby Knife
  • Circle Cutter
  • Estes Model Rocket Builders Marking Guide
  • Thin CA - Super Glue
  • Wood Glue
  • Sandpaper (220-600 Wet/Dry)
  • Epoxy (15 minute)
  • High Build Primer
  • Paint - White, Red and Yellow
  • Pencil
  • Masking Tape
  • Ruler
  • Nitrile Gloves
  • Paper Towels
  • Acetone

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