demonstrated. The axial thrust oscillation could be simulated by 2 large asymmetric counter-rotating  masses near the center of gravity of the first stage. Demonstrating the ability to prevent re-contact after  initial separation is a critical part of any separation qualification program. If the thrust oscillation was to  slam the two stages back together after initial separation, impact loads would be transmitted to the sensitive avionics boxes on the aft skirt. Also, the structure of the aft skirt near the contact location could  fail locally and unpredictable separation dynamics would be present.  MAG Strut Qualification  Qualifying the strut separation system will be a rel atively quick, low cost pr ogram if a well-designed  development test program is completed before hand. The separation dynamics will be qualified by  analysis. The struts could be stru cturally qualified by analysis with the end fittings being considered  qualified by test assuming that the qualification strut was pressurize with fluid that would generate  sufficient force to subject the fitting to 1.4 times the limit load.  Since the strut is designed with a safety  factor of 2 for static pressure containments and a safety factor of 2.5 for dynamic pressure containment, the end fittings could be subjected to  the limit loads without subjecting the struts to pressures that would  yield the structure. The structure of the aft skirt and the interstage could be qualified by analysis. The  development test would provide the data to validate the analytical models for both the struts and the structure. If some design changes were made to the flight struts that were not reflected in the  development test articles, the qualification testing could be done using the same test set up used for  development testing.    Conclusion  

The MAG Struts are the ideal separation system for Ares I. No other separation system has the capability  to separate with 356 kN of residual thrust on the first stage. This capability increases the Ares I payload  lift capability significantly over a BDM separation system. Secondly, the MAG Strut system is mounted  internally minimizing aerodynamic drag.  Finally the MAG Strut system pushes the first stage and the  second stage apart increasing the momentum transfer between the stages.    The struts reduce the potential for ullage collapse in two ways. Separating with 356 kN of residual thrust  mitigates the potential for ullage collapse because the liquid hydrogen does not have the have the  tendency to climb the walls of the tank as is possible when operating at very low levels of acceleration.  The MAG Strut limits the amount of ac celeration the vehicle experience  to less than 2.5 g per second  decreasing the potential to agitate the liquid hydrogen.   The MAG Strut limits the amount of load applied to the aft skirt during assent to 68 kN while they have the  capability of stroking with a peak force 187 kN each. 

The MAG Struts produce superior nozzle clearance under all conditions including one strut out cases.  This means that the struts are inherently two-fault tolerant against pressure bleed down. The struts also greatly mitigate the effects of the SRB nozzle pointing accuracy and any other disturbances coming from  another source because of the matching of the mass properties of the two separated stages.   Although struts have not been used on a manned vehicle, the struts can be brought up in design maturity  in time to support later Ares I test la unches assuming that the developme nt test program is conducted  concurrently with other Ares I development programs. Doing the development program facilitates the inclusion of the struts at a later date in the Ares program. 

The authors of this paper would like to acknowledge the contributions of the following people: Acknowledgement 1: Young Kim of Marshall Space Flight Center for fly-out analysis  Acknowledgement 2: Mike Hannan of Marshall Space Flight Center for performance analysis  Acknowledgement 3: Mike Martin of Marshall Space Flight Center for gas flow and pressure analysis   Acknowledgement 4: Mike Perry of Marshall Space Flight Center for computer aided design integration      344