Rocketry Planet

In 2006, the Rump Aerospace Team successfully built and flew an all-composite, 3 inch, N-class (13,500 newton seconds), staged rocket (Loki M1882 to Ellis M1000), to over 46,600 feet MSL at the XPRS Launch held at Aeropac’s Black Rock launch site. Taking lessons learned from an almost flawless flight, our approach is to build on the successful attributes of the flight profile as well as the design and build of the vehicle.

Our approach is to build strong and light, maximizing the use of an all-composite airframe and high temperature laminating resins throughout airframe construction. Our design minimizes complexity in assembly and recovery and relies on proven techniques with which we have experience. This year’s Rumpty Dumpty project is essentially an up-scale of last year’s project with some substantial upgrades to aid in coping with the additional stresses resulting from the upgraded power plants which we are proposing to use.

In 2006, our experience indicated that constructing the electronics bay in the same manner as the airframe (using composite materials) resulted in an inordinately thick tube wall. The tube was built in this manner to assure the project stayed within budget (a mandrel for the coupler section would require custom machining). This restricted an already confined space and made mounting of the electronics overly challenging. While this construction method was sufficiently robust to endure the stress of an M-to-M flight, for convenience sake and additional strength, we have replaced the composite coupler tube with a section of T6061 T6 drawn aluminum tubing (0.125 inch wall thickness). This change increases the durability and robustness of the component while maximizing the space available to support our upgraded electronics suite.

The second issue discovered as a result of the 2006 flight, was the inability of the electronics suite used in the sustainer section to accurately report the apogee altitude by any other means than the output of a single, 2 axis, accelerometer. While we believe the data delivered by the Ozark Aerospace ARTS unit was accurate based on the “arrow straight” flight profile, the accepted wisdom is that accelerometer data based on anything less than 6 axes’ of measurement is highly susceptible to in-flight anomalies (coning, spin, and non-vertical trajectory). While the electronics operated flawlessly for sustainer ignition and recovery, they were not able to accurately record and report the barometric altitude beyond 46,663 feet AGL. This year’s electronics suite has been substantially enhanced to address this condition.

High Level Summary:

Detailed Design and Construction Notes:

Layers of carbon fiber and Kevlar were laid up around an aluminum mandrel to make the airframe tubing.

Lamination begins with the Kevlar layer going on.

Lamination continues with the carbon fiber layer.

And continues with yet another carbon fiber layer.

Because of the nature of the project, a composite expert was brought in.

A 5-to-1 conical nose cone mold was made from this male plug.

The fins were made using a plate glass "blank".

A "bias gauge" was used to maintain the orientation of the lamination layers.

This completed fin plate will make two fins.

After the fins were cut out of the plates, a special jig was used to apply the 10 degree bevel.

All six fins, beveled and ready to go.

Here is how the fins are oriented on the airframe.

Details of the initial fin mounting.

Another shot of initial fin mounting details.

Cotronics epoxy and Kevlar pulp make the fillets.

Another view of the fin fillets.

Fin templates help insure the fins go on straight.

Wrapped with peel-ply and a vacuum bag setup, the airframe-fin assembly is placed inside a specially built curing oven to bake.

Here's a close-up of the vacuum bag setup.

The final result of the vacuum bagging process.

T6061 T6 drawn aluminum electronics bay.

Close-up of surface mounted t-nut rail-guide mount.

Rail-guide mount after wrapping with carbon fiber.

2 inch square steel stock and standard triangular radio tower sections were used to make the launcher.

20 feet of radio tower will be fitted with 1515 aluminum rail.

The completed launcher makes a compact package.

Light and easy to move, but outfitted with a trailer hitch to move around easily with a four wheeler.

Mark Palmer tests the tower by applying a little weight while Art Upton tries to keep it from floating off.

Zach Palmer decides to test his luck climbing the tower, and dad's health insurance.

Airframe
The composite airframe sections were all laid up using a well proven method. Each airframe section was laid up using 5.7 oz grade certified, standard weave, carbon fiber cloth, and 5.0 oz Kevlar cloth over a 4.000 inch aluminum mandrel. Aeropoxy resin was used throughout the construction. While the use of carbon fiber ensures the airframe components have a sufficient level of strength and rigidity, Kevlar cloth is used is enhance durability and robustness while mitigating the brittleness inherent in an all carbon fiber construction.

All composite pieces were constructed according their purpose and identically cured using the following process:

• All airframe sections were laid up over a 4.000 inch OD aluminum mandrel.
• All airframe sections were wrapped with heat shrink tape to remove excess resin from the lay up.
• All airframe tubular sections were cured at 180 Fahrenheit for 1.5 hours. The airframe tubular sections were allowed to cool back to room temp, and then the heat tape was removed.
• The airframe tubular sections were then cooled to 55 degrees Fahrenheit to assure the release the aluminum mandrel, which was then removed.
• The airframe tubular sections were then allowed to “rest” for five days.
• The airframe tubular sections were then washed inside to remove all traces of mold release,
• The airframe tubular sections were then post cured in a ‘PID” controlled curing oven according to the following protocol:
  
  
  • Heated to 105 degrees Fahrenheit and allowed to set for eight hours
  • Slowly ramped up to 155 degrees Fahrenheit and held for five hours,
  • Slowly ramped up to 200 degrees Fahrenheit for five hours,
  • Slowly return to room temp.
• All the fins were also post cured using the same schedule.

The airframe consists of three sections of all composite airframe laid up as above. Each section was designed to accept different levels of stress; and the optimum strength/weight balance was struck for each section. The details of each section follow:

Nose Cone
The nose cone design, a 5-to-1, conical nose cone, 20 inches long was decided upon after initial simulations with the proposed motor combination indicated that this was fairly close to the optimal solution. We opted to build a two-piece “negative” mold and cast each 1/2 of the nose cone in it’s own mold, bringing the two halves together prior to full cure (while each section was still at the green/leather stage of cure).

The first step was to create a plug to serve as the model for a two section mold. This was accomplished by building up the shoulder and exterior surface of a standard sized 4-inch fiberglass nose cone (purchased from Performance Rocketry) using multiple layers of Aeropoxy mixed with West Systems Microlight Fairing compound. Once the appropriate diameter was achieved the plug was filled, sanded, primed painted and polished.

The mold was cast in two sections from the exterior of the plug and is constructed of gel-coated fiberglass to assure positive release of the finished nose cone. Each section was carefully constructed to assure positive, aligned and error free mating of the mold halves could be achieved.

The nose cone design/construction elements are as follows:

Inter-stage Coupler
In most two-stage designs, the inter-stage coupler itself is the weakest link in the “airframe chain”. It receives the highest stress and is usually, at best, only slightly more robust than the airframe around it. Our design has eliminated this potential failure point by using the standard, unmodified, CTI Pro98 motor case itself (sustainer motor) as the coupler. In order to accomplish this, the motor will be loaded into case with the retainer thrust ring placed at the upper end of the motor opposite of the nozzle. This configuration has been approved and endorsed by Mike Dennett of CTI.The integral motor thrust ring will rest against the internal phenolic insulation layer providing positive motor retention. An S-Glass spacer will be inserted into the top of the booster and rest against the integral Pro98 motor thrust ring. The sustainer electronics bay will seat against this spacer ring and will provide an integrated motor thrust ring. This spacer will be an all composite component made as follows:

Sustainer Electronics Bay
Based on the experience we gained during the design, build, pre-flight preparation and flight of last years “Black Jack” project, we opted to increase the robustness of the sustainer electronics bay due to the increased stress and the need to house additional electronics. In order to provide an acceptable strength to weight ratio for this component we opted to construct this section from a single piece of four inch OD section of T6061 drawn aluminum tube 14 inches in length. The fore and aft bulkheads, 1/2 inch in depth with a 1/8-inch lip are machined from solid aluminum billet stock and are secured to each other by three 16 inch lengths of 1/4-inch stainless steel all thread in a triangular pattern. Each bulkhead will have six holes spaced equidistant around the perimeter. These holes will be drilled and tapped to accept a 1/4-20 tapered head aircraft grade (Grade 10) bolt to provide a secure attachment point for the upper and lower airframe sections. Details are as follows:

Booster Electronics Bay
The electronics bay in the booster section will be based on last year’s successful “sliding bay” approach. The Bay will be of an all composite construction and will be sized so that it slides into the booster section of the airframe on top of the parachute and recovery harness. The base of the bay will sit against the internal phenolic liner. This internal bay will be ejected ahead of the parachute and recovery harness and will be tethered to the lower portion of the recovery harness. The electronics bay construction details are as follows:

Onboard Electronics
Based on the experience gained after last year’s flight we have opted to significantly upgrade the electronics suite and deployment systems in both the booster and sustainer for this project. Our decision is to move to a proven, robust, lightweight component for actuating booster and sustainer recovery and sustainer ignition.

The booster will contain an Ozark Aerospace ARTS board which has been certified by the manufacturer to accurately record altitudes below 34,000 feet MSL via the onboard barometric pressure sensor. During last years flight of the Black Jack, this component worked flawlessly for deployment above this altitude (estimated to be 51,000 AGL) based on the integrated accelerometer. However the booster section is not expected to exceed an apogee of 25,000 AGL (29,000 feet MSL). To provide back up a PerfectFlite Micro Timer 2, triggered via a break wire secured to the launch tower, will be set to fire a secondary deployment charge at 22 seconds after first movement is detected.The sustainer will contain two R-DAS Tiny altimeters with an additional igniter board and one 4-axis accelerometer board. This board was selected based on its multiple successes at deployment and recovery of extremely high speed and high altitude flights. To provide back up we will have redundant CO2 apogee deployment systems and a redundantly wired Defy Gravity Tether system.

Motor Retention
The booster motor will be positioned so the integral Pro98 motor thrust ring rests securely against the lower edge of the booster airframe. A length of 3/8-inch stainless steel all thread rod will be secured to the top bulkhead via the integrated threaded end cap using Loctite and two stainless steel nuts torqued down against the a end cap. The threaded rod will slide though an 1/8-inch think bulkhead made of laminated layers of carbon fiber cloth laid up at repetitive 30, 60 and 90 degree biases. A large, heavy-duty “fender” washer will be placed between the top side of the carbon fiber bulkhead and the bottom edge of the stainless steel nut which will torqued down to assure retention. This nut will be secured using a ratchet wrench and extension from the upper end of the Booster airframe. A second nut will be run down against the first to assure there is no movement during the flight and/or recovery of this section of the vehicle.

The sustainer motor will also be secured from the top end. In this case the motor will be loaded into the case with nozzle opposite the integrated Pro98 motor thrust ring. The motor will be inserted into the top of the sustainer airframe with the "bottom” of the retainer ring (usually the top of the ring when used in a standard configuration) resting against the internal insulation liner. A carbon fiber spacer will be inserted into the top of the booster and rest against the integral Pro98 motor thrust ring. The sustainer electronics bay will seat against this spacer ring and will provide an integrated motor thrust ring.

Final Assembly
Each stage of the project will be prepared independently and will be mated on the launch tower. There is no positive retention of the upper stage to the lower stage. The two stages will be friction fit at the pad using tape if necessary.

Launch Guides
Only the booster section will have launch guides. We will be using three standard rail buttons from Railbuttons.com. These will be placed as follows:

The launch buttons will be secured using the appropriate “t-nuts”. These nuts will be mounted to the airframe after the initial cure has take place. They will be surface mounted using Aeropoxy structural adhesive and will then be reinforced with three layers of 5.8 oz carbon fiber cloth laid over the existing pre-cured airframe and will be wrapped with heat shrink tape to assure proper bonding and aerodynamics of the airframe. The rationale for not installing the inserts during the initial tube construction is related to the metal tee nuts ability to hold heat and conduct heat during the curing process. We felt that pre-installing the nuts prior to the cure introduced an unnecessary variable into the cure process as they would likely heat and cool at different rates then the surrounding airframe section and would potentially introduce unnecessary failure points into the finished airframe.

Flight Profile Detail:

Launch Platform
Based on the extreme nature of this projects flight profile, the complexity of the pre-launch preparation and the need to be able to fly this project when the weather and wind conditions are ideal, we designed and built our own launch tower. This allows us to prepare and fly our rocket at our convenience and to assure that the preparation of our project is not impacted by the need to accommodate other flights and conversely assure that we are not negatively impacting the ability of the Aeropac club to launch other extreme projects. Furthermore this provides assurance that we have the appropriate launch platform, sufficiently robust, to flawlessly support the launch of our project.

This pad provides a minimum of 20 feet of 1515 rail (standard 1-1/2 inch rail) mounted to 20 feet of radio antenna tower. The radio tower was selected over TV antenna tower for its higher strength and rigidity. The tower’s frame and support legs are constructed of two inch square steel stock. The pad has three legs, 120 degrees apart from each other, which extend outwards 10 feet from the base of the tower. Each leg has an adjustable foot pad to adjust launch angle.

The pad is constructed of steel and consists of three legs, a central frame (with retractable wheels to facilitate placement on the playa), two ten-foot sections of tower, one 12-foot length of 1515 rail, one length of eight-foot 1515 rail, and two ten-foot sections of 1010 rail. The 12-foot section of 1515 rail is the base section and includes an integral blast deflector. This section bridges the tower mating point to provide additional rigidity. The 1010 rail sections are mounted directly to the side of the 1515 rail and bridges the mating point of the 1515 rail adding further rigidity and strength to area where the radio tower sections mate.

Once the vehicle is mounted to the rail, and the tower has been raised, four stabilizing guy wires will be used to secure the tower and provide final adjustments to the launch angle. In tests, the raised tower (minus the guy wire system) has supported 200 pounds of mass centered at the tower joint and is solid and stable.

Pre-Flight Conditions
In order to assure safe launch and recovery of the vehicle, we intend to wait for ideal weather conditions. In order to assure we fully understand the launch conditions and their effects on the flight and recovery profile we will:

• Obtain ground level conditions using a Krestel 2000 hand-held anemometer. The Krestel unit will provide wind speed (current, average and maximum wind gust data), temperatures and barometric pressure.
• Obtain wind speed and direction in 5-10 thousand foot increments to 100,000 MSL. This will be accomplished through the use of data available from the NOAA and will be obtained for us by a support crew in Michigan. This information will be accessed from the launch site via the use of a satellite phone unit.
• Use this data as input to generate a splash pattern using RockSim Pro.
• Compare this data against topographical maps provided through National Geographic mapping software based upon United States Geographical Service quadrant maps. The map and topo database will be updated each morning at the hotel to assure the map and topo data are up to date and accurate.
• NOT fly the vehicle if the splash pattern places the landing pattern in either an inhabited or overly remote area.
• NOT fly the vehicle if there are any anomalies with either the primary or back up electronic suites or tracking suites.
• NOT fly the vehicle if it sustains any structural or sever damage in transit or preparation.
• NOT fly the vehicle unless the Aeropac RSOs are satisfied with the flight and recovery profile.

Booster Ignition
Based on our previous experience we feel it is great importance for safety, stability and flight profile success, for the booster motor to come up to solidly up to pressure. However, we will once again use our standard ignition practice of using two standard igniters. To assure ignition we will abrade the core of the top three grains of the motor to assure there is fresh propellant face (and no mold release). Our rationale is to assure a solid ignition without adding the stress of an instant on (copper thermite-fueled) ignition. The thrust to weight ration of the N2500 is more than sufficient at approximately 10-to-1, to assure a safe, stress mitigated liftoff.

Booster Separation
Booster separation will be actuated 1.5 seconds after sustainer motor burnout using a PerfectFlite Micro Timer (activated via a break wire at liftoff) and will be accomplished using a proprietary Rump Aerospace CO2-driven dual-piston system.

Sequencing and Sustainer Ignition
Based on our previous experience flying multiple staged high power rocket flights, we feel it is of paramount importance for safety, stability and flight profile success, for the sustainer motor to come immediately and solidly up to full pressure/thrust. In order to assure this occurs, we will be using copper thermite for ignition. Our standard practice of igniting the Pro98 N2500 is as follows:

Booster Recovery
Booster recovery will be single event/apogee deployment and will be accomplished using the electronics suite previously described in this document. All deployment will be out of the top of the booster airframe. At apogee our vehicle will deploy a Halo Aerospace “Halo 25” parachute. Primary deployment will be accomplished through the use of a proprietary Rump Gas CO2 deployment system activated via the ARTS board at apogee. Black powder will be used for a back up charge and will be actuated by a PerfectFlite Micro Timer 2 at 22 seconds after launch.

Sustainer Recovery
Sustainer recovery will be dual event deployment using the electronics suite previously described in this document. All deployment will be out of the top of the sustainer airframe.

At apogee our vehicle will deploy a Halo Aerospace 14-inch drogue chute to stabilize the decent. Apogee deployment will be via 2 “Rump Gas” CO2 systems using redundant e-matches wired to separate R-Das Tiny altimeters. Each Rump Gas device will have two e-matches. The e-matches in each Rump Gas unit will be cross-wired so each unit will have an e-match wired to each of the two R-DAS Tiny altimeters assuring total redundancy.

The main parachute (Halo Aerospace “Halo 25” parachute) will be deployed at 2000 feet. Main deployment will be accomplished through the use of a Defy Gravity Tether system with redundant e-matches wired to separate R-Das Tiny altimeters.

Tracking

The BigRedBee frequencies will be set the day of the launch once frequency usage at the launch can be assessed to assure there is no overlap with other users. The Rocket Hunter frequencies will be established in a similar fashion. The Garmin unit consists of a Garmin 15 engine coupled to a MaxStream 9Xtend 1 watt 900 MHz dataradio set. This radio set is FCC certified and compliant for use in telemetry. The tracking teams will consist of a minimum of three licensed amateur radio operators. Further assistance with tracking has been pledged by Greg Clark of BigRedBee.

While we feel this offers a sufficient number of redundant tracking mechanisms, our primary source of tracking data will be the GPS telemetry data from the BigRedBee units. These units were selected for their proven reliability as well as their proven ability to transmit at distances well over 25 miles (line of sight).

We will be using a standard BigRedBee GPS unit in the booster. However, the sustainer will require a unit with a customized algorithm to overcome the limitations inherent in the GPS receiver which the BigRedBee unit uses. This limitation is pre-programmed into all commercially available GPS receivers. All commercially available GPS receivers are pre-programmed to stop recognizing their position if the unit records both a velocity in excess of 515 meters per second and an altitude of 18,000 meters.

Our current profile shows our velocity at 18,000 meters to be 545 meters per second. It is therefore imminent that we will loose satellite lock (and positional awareness/reporting) at approximately 33.75 seconds into the flight. The velocity of the sustainer will stay above 515 meters per second until 36.86 seconds into the flight. We have been working through Greg Clark to develop and use an algorithm that senses the approaching lock out and resets the unit after a pause sufficient to assure the velocity of the sustainer is under 515 MPS. With the current profile this will allow approximately 48 seconds for the unit to re-obtain satellite lock prior to apogee. Once we have received approval for our flight (and flight profile) we will have Greg load the algorithm loaded to the customized GPS unit.

GPS telemetry will be monitored through out the entire flight profile by multiple team members. Final recovery location can be plotted from the GPS coordinates on laptop computer running National Geographic’s topographical mapping software and can be printed on site if need be. Further tracking assistance will be sought through the StratoFox organization (http://www.stratofox.org/).

Kevlar® and Teflon® are registered trademarks of E.I. du Pont de Nemours and Company in the United States.
Pro98® is a registered trademark of Cesaroni Technology Incorporation in Canada.

Reader comments:

#1 Yeowzaaaaa!!! :eek:

Good luck. Sounds like it's gonna be awesome.

ultrasonicTim on 09-10-2007 09:24 PM

#2

I had the pleasure of seeing the finished, painted rocket at the JMRC launch this past weekend, and I will say the guys outdid themselves this time. Jim laid a perfect, glossy finish on the bird that almost makes it too nice to fly. The planning and detail work that went into this rocket was over the top.

Best of luck guys!

Fred Ziegler
Fade to Black Rocket Works
http://www.ftbrocketworks.com

porthos on 09-12-2007 06:38 PM

#3

Fred, I understand that launcher was some of your handiwork. Great job!

ddmobley on 09-12-2007 10:14 PM

#4

Quote:

Fred, I understand that launcher was some of your handiwork. Great job!

Thanks Darrell! Jim and Mark gave me a basic idea of what they wanted and I designed it to their specs. It's made to tear down and fit in Jim's small trailer, then to be pre-assembled at their prep spot and towed to the launch site with an ATV or other vehicle.

porthos on 09-14-2007 11:27 PM

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