Midterm Report Questions and Responses

Midterm Report Questions and Responses

Team: Coeus
Date: Oct. 20 2008

1. Metrics – Shouldn’t there be more numbers?

Answer: Yes, but number were still TBD at time of presentation due to lack of cryogenic database.

1. How do you keep the atmospheric conditions you are assuming to be found on Titan constant long enough to successfully perform all necessary tests?

Answer: This has become the major portion of our project and we are currently in the process of designing a system to accomplish that task.

1. Slide 13 – The graph had a green line on it… What was that exactly?

Answer: The green line was payload weight (not mass) distribution.

1. (6) – How is “concise cryogenic database” a specification? – What Constitutes “Concise”?

Answer: Concise – def. - expressing much in few words

1. Wing deployment mechanism – any ideas?

Answer: The deployment details of this mechanism are beyond the current scope of our project.

1. Why did you choose the wing structure that you have?

Answer: The sample structure from the presentation was idealized and not a final model.

1. What calculation(s) are you specifically doing now to prepare for cryogenic material testing?

Answer: Heat transfer analysis through composites.

1. How are you going to use your cryogenic data [words lost due to cropping] design? – Material Selection?

Answer: Material properties over the massive temperature that our craft will operate in will limit the overall design. Such as skin thickness, rib spacing and placement, etc.

1. Are you focusing on cryogenics only or will there actually be an aircraft design?

Answer: The original plan was to fully design an aircraft. However, as we continued research this semester, we found that material properties were not available in the ranges we needed to consider for our design. Therefore our project is moving towards more of a material research project.

1. Where on Titan would you prefer to deploy aircraft?

Answer: In the air. Mission analysis is beyond the scope of this project. Anywhere between space and the surface of Titan.

1. If this isn’t going to Titan, where will airframes encounter cryogenic conditions?

Answer: Our research is applicable beyond aircraft frames. However, aerospace frames, such as those used to explore the dark side of the moon approach the cryogenic regime.

1. Stated project goals as cryo carbon/matrix project… still building project?

Answer: We are still doing a project. However, it has changed considerably from the original outset.

1. There aren’t many explanations for the assumptions they are making. (Thermal aspects, uniform temperature)

Answer: The validations of many assumptions were not included in the Mid-Term report due to time constraints. The time constraints of the testing and heat transfer coefficients allow us to approximate the temperature as uniform.

1. Is their airfoil and frame going to produce enough lift?

Answer: It’d better. Keep in mind that the gravity constant on Titan is approximately 1.4 m/s^2.

1. Are they over simplifying their parameters?

Answer: We hope not. Our uniform weight distribution is better than a point but still relatively simple to use in calculations and can be modified easily in the future.

1. You’ve done all these calculations for the wings, but what about the body and body/wing interfaces?

Answer: These calculations would have been the next step in our project. However, our new project focuses mostly on cryogenic research. We had decent volume and mass estimate for our payload and propulsion system therefore we could determine the volume of the body and had planned on using a blended wing-body aircraft.

1. Give background/basic info before giving specifics. More Pictures? Cryo only. No idea what’s happening…

Answer: No idea how to answer this.

1. Are you going to build a model or is the entire project experimentation and theoretical analysis?

Answer: The original plan was to build a deliverable model, however, we are now focusing our efforts entirely on cryogenic research.

1. Where did L/D ratio =12 stem from?

Answer: We have a “black box” engine that is limited in thrust and is based against competitive payload system mass. Thus we had a power maximum and weight limit and could use these to determine lift to drag.

1. What caused change in goal (more detail)

Answer: A combination of the lack of knowledge of material properties at cryogenic temperatures and the ease of aerodynamic calculations coupled with the aerodynamic similarities between Titan and earth led us to change our goals to focus more on material properties research. The lack of ability to test materials at cryogenic temperatures has led us to further adapt our project to creating a vessel to hold these low temperatures during testing.

1. Lot of work coming up… need a detailed schedule to allot necessary time.

Answer: We are in the process of designing a Gantt chart based on the changes in our project.

1. Will your wing be a semi-monocoque type structure?

Answer: This would most likely have been the case but we cannot be completely certain without knowing the material properties.

1. If you plan to complete 1 test by winter, how do you plan to meet all project objectives by end of SP 2009?

Answer: A Gantt chart has been developed and will be in our next presentation.

1. Which is more important when choosing fiber direction, strength or displacement due to CTE?

Answer: First priority will be strength. The structure must withstand the loads. Secondly, we will look at displacement. It is likely we will find the best choice is a woven cloth with fibers at 90 degrees to each other. This makes the strain due to CTE even and symmetric.

1. Why will aerodynamics on Titan be the same as Earth?

Answer: The principles of fluid mechanics hold regardless of what fluid you are immersed in. Certain aspects may be different (density, temperature, pressure, gamma, etc.) but the basic laws still apply. In addition, Titan’s atmospheric composition and the interaction of elevation, temperature, pressure, and density are similar to Earth’s.

1. What are your assumptions based on?

Answer: See question 15

1. How is the ambient density of Titan’s atmosphere going to affect propulsion?

Answer: The engine was designed by a graduate student at another university and is considered a “black box” in our scenario. The main scope of this project is cryogenic composite research for aerospace design.

1. How will the experimental results affect your design?

Answer: Strength properties determine skin thicknesses and spar cross-sectional areas.

1. Seems to be more of a case study on cryogenic carbon fiver rather than an aircraft design project. Where are fuselage and propulsion considerations?

Answer: That’s what the project has become. We are no longer focusing on aircraft design.

1. How did you calculate the wing loading requirement of 81 N/m^2.

Answer: We used Kutta-Joukowski and the elliptical lift distribution to determine how the lift total (equal to the weight) is spread about the wing. We then use Force/Area with the area being the cross-sectional area of a 2 celled wing cross-section.

1. How can you find forces expected at launch?

Answer: Dr. Flemming handed out a spreadsheet last semester in Aerospace Structures that listed g-forces experienced on launch vehicles. Also, online research including the Boeing website list these loads.

1. Have you made too many idealizations?

Answer: See question 15

1. Can the pod the aircraft is in inside the rocket be [cooled?] to reduce strength requirements?

Answer: It wouldn’t be worth it to add the necessary environmental control systems. The design of the craft will actually be fairly simple since the shape of the craft won’t change too drastically with temperature.

1. Discussed vacuum bagging composite parts, why not a compression mold?

Answer: Vacuum bagging is much more cost effective and designing a compression mold and/or buying or renting time on one wouldn’t be cost effective.

1. How will the craft pilot itself and perform its mission when it reaches Titan?

Answer: Controls and guidance systems are beyond the scope of this project. Titan is now our basic model and we are focusing on cryogenic composite research.

1. Address Re, similarity testing.

Answer: The Reynolds numbers came out to be non-outstanding. Similarity testing and aerodynamic analysis would be simple and not a novel idea. We decided to focus on cryogenic research of composites.

1. Propulsion?? – Seems too much emphasis on structures.

Answer: The engine was designed by a graduate student at another university and is considered a “black box” in our scenario. The main scope of this project is cryogenic composite research for aerospace design.

1. How much will the temperature affect the overall efficiency?

Answer: The engine design was done by a graduate student and has design the system to meet the specifications of our target flight conditions. Given this, we assume the engine to be a “black box” that simply produces the thrust we need. It is beyond the scope of this project.

1. They said test a series of materials, how many samples are considered in a series for their goal to be complete?

Answer: We’ll test 25 samples per type of test. 20 will be at cryogenic temperatures, 5 will be at room temperature as controls.