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A.5.2.3 Nose Cone
A.5.2.3.2 Materials Consideration for the Nose Cone
For the selection of the nose cone material we began with research into historically used materials in similar applications. The two most similar applications we have studied are the Vanguard rocket and the design for the Purdue Hybrid Launch Vehicle.1,2
The most widely used materials employed for such applications include aluminum, titanium, magnesium alloys, molybdenum, carbon-carbon composites, and hafnium diboride.3 Since our project is optimized with respect to cost, many of the ceramic and composite materials are eliminated from potential materials due to their extremely high manufacturing and raw material costs.4 Ablative materials are not considered for this design. From here we figure out which material is the least expensive that can still fulfill the requirements of the nose cone.
The tip of the nose cone must withstand the thermal and aerodynamic forces experienced when attaining orbit. Two relatively attainable and low cost materials, aluminum and titanium, are studied to determine their feasibility with the application.
Table A.5.2.3.2.1 Material Specifications of Aluminum Alloys3
Alloy / Tmelt (K) / ρ (g/cm^3) / σcomp (Mpa)2014 / 780.37 / 2.80 / 399.90
2024 / 774.82 / 2.77 / 399.90
2219 / 816.48 / -- / 386.11
6061 / 855.37 / 2.70 / 151.68
7075 / 749.82 / 2.80 / 275.79
2618 / 822.15 / 2.76 / 399.90
X7005 / 880.37 / 2.80 / 324.05
7049 / -- / 2.77 / 448.16
7175 / 749.82 / 2.80 / --
Averages / 801.01 / 2.77 / 348.19
The average melting temperatures of aluminum alloys is about 800 K. While inexpensive and widely available, this temperature does not reach the constraints for the thermal loading that will be seen by the nose cone while in is ascent to orbit.
Table A.5.2.3.2.2: Material Specifications of Titanium Alloys3
Alloy / Tmelt (K) / ρ (g/cm^3) / σcomp (Mpa)Ti / 1922.04 / 4.51 / 551.58
Ti-5Al-2.5Sn / 1810.93 / 4.46 / 758.42
Ti-6Al-4V / 1810.93 / 4.48 / 868.74
Ti-7Al-4Mo / 1922.04 / 4.37 / 1068.69
Ti-8Al-1Mo-IV / 1977.59 / 4.82 / 999.74
Ti-679 / 1977.59 / 4.70 / 999.74
Ti-8Mn / 1772.04 / -- / 827.37
Ti-6-2-4-6 / 1922.04 / 4.56 / 1103.16
Averages / 1889.40 / 4.56 / 897.18
Titanium alloys generally have a melting temperature around 1900 K. This value meets the requirements of the similar rockets’ nose cones.1,2 While we are unable to complete a thorough thermal analysis on our particular nose cone, we are able to design it from atmospheric conditions during flight.
Ultimately we come to the conclusion that titanium is the cheapest and most easily accessible material that could be considered for the nose cone of the rocket. This titanium material will provide the tip of the nose cone with extra thermal protection and the remainder of the nose cone is aluminum. This combination of metals allows us to reduce cost based on raw materials and manufacturing of those materials.
References
1Klemans, B., The Vanguard Satellite Launching Vehicle, The Martin Company, Engineering Report No. 11022, April 1960.
2Tsohas, J., Droppers, L.J., Heister, S.D., “Sounding Rocket Technology Demonstration for Small Satellite Launch Vehicle Project”, 4th Responsive Space Conference, 2006.
3Brady, G.S., Clauser, H.R., Materials Hand Book, 13th Edition, McGraw-Hill, Inc, 1991.
4Jastrzebski, Z.D., The Nature and Properties of Engineering Materials, Second Edition. John Wiley & Sons, Inc., 1977.
Author: Molly Kane