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4.3.4.3 Structures

4.3.4.3 Structures

The launch vehicle for the 5 kg payload design is comprised of a three-stage rocket carried by a gondola and balloon. The gondola is mad of aluminum bars, 0.04 m thick.

Fig. 4.3.4.3.1 Gondola frame for rocket element of launch vehicle of a 5 kg payload.

(Sarah Shoemaker)

We mad the frame 5.133 m tall with a square base of sides 1.38 m long. The ring supports have a diameter of 1.8386 m. The mass of the gondola add up to 338.32 kg. The material properties and dimensions give the structure the ability to withstand the approximately 36 kPa of pressure it experiences during launch.

The first stage of our rocket is 10.6004 m in length and 1.8386 m in diameter. An engine, oxidizer tank, fuel tank, pressurant tank, inter-tank structure, and avionics equipment make up this first stage. All of our tanks are created from aluminum, but have different sizes and thicknesses. An inter-stage “skirt” connects the first and second stages of the rocket. It has a constant 10° slope from the lower stage to the upper stage. We also made this of aluminum and it is reinforced with aluminum support stringers and rings. Between the first and second stages is a 2.8965 m inter-stage structure. Its maximum diameter is that of the third stage 1.8386 m, and the minimum diameter is the diameter of the second stage 0.8172 m.

Only an engine, fuel tank, and avionics equipment make up the second stage of the rocket. This stage has a diameter of 0.8172 m and a length of 3.2709 m. The second stage fuel tank is also made from aluminum. The inter-stage structure connects the second and third stages of the rocket, having a constant slope of 10° and vertical length of 1.5380 m.

The third stage is 0.9046 m in length and is 0.2748 m in diameter. It is also composed of an engine, fuel tank, and avionics equipment. The fuel tank is constructed from aluminum. The 5 kg payload sits above the third stage and is protected by the nose cone. The nose cone is 0.3408 m in length and has a mass of 1.7927 kg.

The inert mass breakdowns of components and stages are summarized in the following table.

Table 4.3.4.3.1: Inert Mass Breakdown of Three-Stage Rocket, 5 kg Payload

Stage 1 / Stage 2 / Stage 3 / Totals / Units
Fuel Tank / 191.9896 / 85.5083 / 3.2442 / 280.7421 / kg
Ox Tank / 155.5405 / 0.0000 / 0.0000 / 155.5405 / kg
Pressure Tank / 35.7067 / 0.0000 / 0.0000 / 35.7067 / kg
Engine / 193.4741 / 75.7181 / 8.5610 / 277.7532 / kg
Pressure Addition / 166.3206 / 0.0000 / 0.0000 / 166.3206 / kg
Avionics / 3.9600 / 23.8200 / 3.9600 / 31.7400 / kg
Inter-tank / 0.0697 / 0.0000 / 0.0000 / 0.0697 / kg
Skirt/Nose Cone / 24.2454 / 5.2916 / 1.7927 / 31.3297 / kg
Total / 771.3066 / 190.3380 / 17.5579 / 979.2025 / kg

We have determined the total height of this rocket to be 14.7759 m. This value indicates the length from the end of the first stage nozzle to the tip of the nose cone. The following table shows the specifications of each part and each stage.

Table 4.3.4.3.2: Dimensions of the Three-Stage Rocket, 5 kg Payload

Stage 1 / Stage 2 / Stage 3 / Totals / Units
Nozzle Length / 2.5304 / 0.6122 / 0.1304 / 3.2730 / m
Engine Length / 0.6326 / 0.1531 / 0.0326 / 0.8183 / m
Fuel Tank Length / 1.8386 / 1.5798 / 0.5312 / 3.9496 / m
Fuel Tank Thickness / 0.0052 / 0.0067 / 0.0022 / n/a / m
Ox Tank Length / 1.8472 / 0.0000 / 0.0000 / 1.8472 / m
Ox Tank Thickness / 0.0052 / 0.0000 / 0.0000 / n/a / m
Inter-tank Thickness / 0.0020 / 0.0020 / 0.0020 / n/a / m
Press. Tank Diam. / 0.8552 / 0.0000 / 0.0000 / n/a / m
Press. Tank Thick. / 0.0056 / 0.0000 / 0.0000 / n/a / m
Nose Cone Length / 0.0000 / 0.0000 / 0.3408 / 0.3408 / m
Diameter / 1.8386 / 0.8172 / 0.2748 / n/a / m
Length of Stage / 10.6004 / 3.2709 / 0.9046 / 14.7759 / m

The connecting inter-stage skirts are designed to meet the requirements of the main parts of our launch vehicle. The skirts are reinforced with stringers and ring supports, detailed as follows.

Table 4.3.4.3.3: Details of the Inter-stage Structure, 5 kg Payload

Stage 1-2 / Stage 2-3 / Units
Vertical Length / 2.897 / 1.538 / m
Shell Thickness / 0.004 / 0.004 / m
Mass / 24.245 / 5.292 / kg
Slope Angle / 10.000 / 10.000 / deg
No. Stringers / 42 / 14 / --
Stringer Thickness / 0.005 / 0.003 / m
Stringer Depth / 0.020 / 0.020 / m
No. Ring Supports / 8 / 1 / --

The slope of 10º was chosen because the closer to vertical they are, the more weight they can withstand. However, they still must provide the transition between the two different diameters. Choosing this low-angled slope gave us more efficient stringers with less material needed for each stringer. Ultimately, this reduced the cost of the stringers. The inter-stage skirt between stages one and two requires a minimum load bearing of 72.530 kN. The inter-stage skirt between stages two and three calls for a minimum load bearing capability of 3.352 kN. The skirts are reinforced with stringers and ring supports, detailed as follows.

Author: Molly Kane