Landing Gear - Lamar 2/16/96 Progress Report

This report will cover the progress through the present date of the items started to date, as indicated on the schedule provided in the proposal. Following a discussion of the completion of these items, the intended progress by the next progress report will be discussed.

Completion Through 2/15
Schedule Item Resp. %comp
Research Energy Dissipation Systems DEC 50%
Obtain Bus Structure Model DLS 100%
Research Joints for Space Landing Gear Applications GV 25%
Learn Pro/Engineer DEC, DLS 5%
Determine Maximum Envelope for Landing Gear DLS 50%
Generate Initial Solid Model, Neglecting Joints DEC, DLS 0%
Design Joints GV 0%

Completion by Task

Research Energy Dissipation Systems (DEC)
Several papers from last semester on press fit washers, metal foam footpad, and yielding rods have been researched and several characteristic equations have been found to model the press fit washers. The press fit washer system has a Von Mises yielding criteria which can be used to represent this energy dissipation system in the dynamics package we will use. The normal force of the washers on the rod and the ideal washer friction will also be represented with equations found. The curve for the typical load vs. displacement found will also aid in dynamic modeling. Thus far, the main progress has been in finding the information needed to build a dynamic model.

Obtain Bus Structure Model (DLS) )
Ronnie Baccus of the A&M Structures Team was contacted on 2/1. The general configuration of the landing gear and other considerations were discussed, and bus structure dimensions were requested. On 2/7 partial bus structure dimensions were received which included only the dimensions detailing the attachment points of the landing gear. Ronnie Baccus was then contacted again on 2/7, and the purpose of the requested dimensions was discussed. Complete external bus structure dimensions are required to determine the usable envelope for the landing gear within the launch vehicle payload bay. On 2/13, the complete external bus structure dimensions requested were received.

Research Joints for Space Landing Gear Applications (GV) )
The design of the joints was studied and it was agreed upon that Ball joints are the most suitable to be used in the landing gear. This is because a ball and a socket type joint reduces the moments induced in the members. This joint gives a rigid connection and allows tension/compression forces in the members but does not allow torsion or moments. Mr. Jatinder Pannu, Doctoral student (Robotics), University of California at Davis was contacted for additional information in this regard and he is expected to give his views on this by the end of this week. Work has been started on getting information from Mechanical design books. Considerable difficulty was initially experienced in finding material that contains specific information on joints; however, several potential sources of information are currently being pursued.

A detailed study of the landing gear project materials from the previous semester helped in understanding the conceptual design of the landing gear structure and how it is going to fit inside the launch vehicle, i.e. the folded position of the landing gear frame.

Learn Pro/engineer (DEC, DLS) )
Due to delays in gaining access to Pro/Engineer, the beginning of this phase of the project has been delayed. DEC and DLS began learning Pro/Engineer on 2/12 with a trip to the Maritime Technology Center in Orange.

Determine Maximum Envelope for Landing Gear (DLS) )
Utilizing preliminary bus structure dimensions obtained at the end of last semester, a 2D AutoCad drawing was generated to begin determination of the usable envelope for the landing gear in the launch vehicle. Preliminary analysis of varying the leg dimensions in this drawing indicate that the constraints imposed by the bus structure and payload bay faring in the launch vehicle may not be a driving constraint. The optimum leg design may easily fit into the available space, which previously had been an issue of concern. Included in figure 1 is the AutoCad drawing used in the preliminary analysis.

Just before the writing of this report, the latest bus structure dimensions were received, which will allow the AutoCad drawing to be updated.

(Graphic was corrupted during trasmission) Figure 1: Dimensional Analysis Drawing

Generate Initial Solid Model (DEC, DLS) )
Due to the start delay in learning Pro/Engineer, the generation of the solid model has also been delayed.

Design Joints (GV) )
As the detailed study of the joints is not yet complete, the design of the joints has not yet started. The intent is to design the joints based on previous design. The team is planning to meet with the structures group from NASA to obtain more information on joint design. An approach using Solid Mechanics is by far the best way to design the joints at this juncture, since the modeling of such joints using tools such as FEA would comprise a project in itself. DLS has obtained a copy of the index of papers from the Aerospace Mechanisms Symposiums in electronic format that is expected to yield some good resources. Due to the fact that the index is in Excel 5.0 format, software upgrades have to be performed on two of the team members computers to be able to use it. Software upgrades are expected to be installed within a week.

Projected Completion by Next Progress Report (3/7)
Schedule Item Resp. %comp
Research Energy Dissipation Systems DEC 100%
Obtain Bus Structure Model DLS 100%
Research Joints for Space Landing Gear Applications GV 100%
Learn Pro/Engineer DEC, DLS 100%
Determine Maximum Envelope for Landing Gear DLS 100%
Generate Initial Solid Model, Neglecting Joints DEC, DLS 100%
Design Joints GV 85%

Projected Completion by 3/7 by Task

Research Energy Dissipation Systems (DEC) )
The yielding rod system will be researched further to determine how this system will react under dynamic loading, then modeled to determine the length and type of material. The company which manufactures the metal foam, Duocel, will be contacted to find out what type of information can be sent, such as performance characteristics, or the different types available. The address and telephone of Duocel was found via a web search of the companies name.
In parallel to determining the expected performance of the energy dissipation systems, the energy dissipation requirements as dictated by the system constraints (1 m/s horizontal, 2 m/s vertical, 450 Kg mass, maximum 7.5 g deceleration) will also be determined. Using the expected and the required performance parameters, performance specifications for the energy dissipation systems will be written. For initial modeling simplicity, these systems may be idealized to operate much like the actual systems (i.e. assume constant force loading during impact vs. actually very close to constant force for the press-fit-washer system). These coarse models should suffice to determine the configuration of the landing gear.

Research Joints for Space Landing Gear Applications (GV) )
The research of the joints for the landing gear frame is expected to be complete by the above mentioned date. A detailed study on various joints and their application or use for the problem at hand is to be completed. Special attention is to be focused on the use of ball joints as it is in the conceptual design. Dr. Valinsky (Assistant Professor, UC DAVIS) is expected to provide us enough material so as to start the design of the joints and to complete it to the extent mentioned above. In addition, a detailed inspection of the Aerospace Mechanism Symposium index of papers is expected to yield useful material.

Learn Pro/engineer (DEC) )
It is expected that by the next progress report DEC and DLS will have learned enough Pro/Engineer to facilitate development of the solids model of a landing gear leg.

Determine Maximum Envelope for Landing Gear (DLS) )
Following the reception of the latest external bus structure dimensions from A&M on 2/13, the 2D AutoCad drawing will be updated to reflect the changes. Dimensional analysis will then be performed again to determine the usable landing gear envelope between the bus structure and the faring.

A preliminary configuration within the usable envelope will then be defined for development into a solids model using Pro/Engineer.

Generate Initial Solid Model (DEC) )
Due to the delay in learning Pro/Engineer, development of the solid model will be running concurrent with the later half of learning Pro/Engineer. It is anticipated at this point that the initial solid model will be completed by the original proposed completion date.

Design Joints (GV) )
The design of the joints is proposed to be done using solid mechanics and strength of materials. A lot of help is anticipated from the structures group at NASA and materials obtained from similar projects in the past. The help from NASA is expected to complete this section. If not, then detailed search for the design of a similar component has to be dug out of previous projects.

Other (DLS, DEC, GV) )
During the latest contact with Ronnie Baccus at Texas A&M, a meeting between the Texas A&M Structures Group, the Lamar University Landing Gear Group, and the University of Texas Bus Structure System Integrator was discussed. This meeting was scheduled at Lamar following the overall meeting on 2/15.

Conclusion

The Landing Gear Team is slightly behind schedule particularly in the Pro/Engineer learning and modeling. The proposed solution is to move the start date of the learning phase of Pro/Engineer back to 2/12 but leave the modeling phase unchanged so that the two are running in parallel part of the time. Finding materials on ball joint design is also becoming quite an issue. Several resources still remain to be tapped, but meanwhile the research is falling behind schedule. For the most part, though, the Landing Gear Team is close to on schedule, and expects to progress nicely before the next progress report.