Fisher Space Systems LLC

Viper Rocket Trike

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Updated Jan 2021
12-31-2021: I began this month by making a wooden template to hand layup the carbon fabric for the Mk I Viper. I found that by laying Saran Wrap on the wooden template it was easier to remove the carbon fabric panel from the template. I cut three wooden panels, made some PLA mold brackets to hold everything together, and inserted some supports and a 1" CPVC pipe. I wrapped some Saran Wrap around the mold and hand laid up the carbon fabric in two layers. The mold and carbon fabric fuselage is shown on the left.

 Next, I worked on the nose cone and forward strut. Originally, I tried to make the nose cone out of PLA. But, it look terrible and the mass was greater than 50 gm. I decided to go with a styrofoam nose cone. I cut a styrofoam block into a rough shape of a nose cone and then sanded down the edges until I reached a tapered shape resembling a nose cone. I glued some hinges on it and attached it to the forward strut. The forward strut is made of PLA and is secured to the fuselage by three small screws. When inserted into the fuselage, the propellant tank rest against the forward strut, pushing on the forward strut during take off. The forward strut and nose cone are shown on the left.

 Finally, after Christmas, I worked on the aft strut. The aft strut centers the rocket engine and supports the fin assembly. I made three fins using the thinnest wall setting on the 3D printer. I glued some K'Nex pieces to the fins to hold everything together. The aft strut and fin assemble are shown on the left.

 I made some plumbing modifications to the propellant tank, solenoid valve, check valve, injector, and rocket engine assembly. Before the modifications, the subsystem mass was ~ 930 gm. After the mods, the subsystem mass, shown on the left, is now ~ 575 gm, a savings of 355 gm.

 The forward and aft cockpit struts are next. The forward cockpit strut supports the fuselage as well as a micro servo motor to open the cover and deploy the paraglider . The aft cockpit strut also supports the fuselage and three micro servo motors for the fins. The cockpit itself houses the battery, receiver, and paraglider. The total flight system mass is an estimated 1,292 gm, well below the 1.5 kg class I requirement. The mass allotment is summarized in the table below. Read more in the December EOM report.


"Simplicity is the ultimate sophistication."
- Leonardo da Vinci
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Copyright (c) 2021 Jerry F Fisher
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Subsystem Mass (gm)
Prop Tank, valves, rocket engine with fuel  
 Forward strut and nose cone  42 
 Cockpit forward strut (includes servo motor)   40 (est.)
Cockpit (includes batt, receiver, & paraglider)  130 (est.) 
Cockpit aft strut (includes three servo motors)   70 (est.) 
 Aft strut and fins 70 
HTPE Oxidizer  75 
 Carbon Fabric Fuselage   290 
Total System       1,292 (est.)