PAGE CONTENTS
Objectives
This project is devoted to the pre-development of Alphabus Central Tube (@CT), equipment which belongs to the structure subsystem of the Alphabus spacecraft. This pre-development consists in demonstrating through theoretical studies and samples manufacturing that the next spacecraft generation could benefit from new technological or industrial improvements, i.e.:
- Improved Launcher Junction Frame (LJF) design
- LJF to shell junction (without monolithic heel)
- Lay-up with laser projection
- Less stringent surface treatments on inserts
- Risk mitigation on shape defects after curing&
Challenges
The issues can be divided in design and manufacturing issues:
Main design issues
- choice of the fiber wrt stiffness and mass analyses
- prediction of deformations of the tube after curing
- LJF design evolutions to insure load transfer between LJF and shell (which impact the tube diameter)
- To lower cost, mass and lay-up time of the junction between LJF and shell
Main manufacturing issues
- Feasibility or not to use a less impregnated prepreg technique for M55J to lower porosity in laminates
- Study of an alternative curing process to lower porosity and have better aligned fiber in laminates
- Study of a new method for corner manufacturing
Plan
The expected project plan is built in 3 steps as follows:
Current Status
Phase 1 of this pre-development has been completed with the Technology Evaluation Review held beginning of 2005.
The main results of the Phase 1 studies are:
- A possibility to fix the cylinder shell to the Lower Junction Frame (LJF) with blind bolts is identified to reduce mass and optimize production time.
- The Launcher Junction Frame (LJF) design has been studied, in order to balance the stresses in the inner and outer skins of the sandwich cylinder.
- Shape prediction analyses have been performed to envisage tolerance compliance after cylinder curing.
- Specific layup designs have been identified for optimization of the composite shell geometric tolerances after curing.
- The interest for a method of hand lay-up in combination with laser projected positioning of pre-preg patches, has been investigated.
- The Central Tube preliminary design has been established with EAR / ITAR free materials and suppliers.
- A preliminary concept baseline and production philosophy has been defined. All necessary processes and procedures are established and validated.