Rocksim simulations with multi-stage clustered rockets

[DaHabes]

OK, so I am designing a 2 stager with a five engine booster to a single engine sustainer. The booster will have parachute recovery via rear ejection of the MMT. The issue I have is that in the simulations if I have any of the outboard boosters with an ejection delay, the sim does not start the sustainer motor until the ejection charges fire (it coasts instead if lighting right after the center booster engine burns out). If I set all of the booster engines to zero delay or plugged, then the sim burns the two stages without any inter-stage delay. It seems like the program ought to know better. Anyone else run into this? I can estimate the delay required in the outboard engines based on the 2D flight profile, but it sure seems kludgey.

 

[heada]

From memory, you can set an ignition delay on the sustainer motor. Set the booster to all zero delays, the sustainer to 2 second ignition delay and rocksim should have the booster separate at booster motor burn out but sustainer ignite after coasting for 2 seconds.

 

[H. Craig Miller]

If you post the design file, someone may be able to provide you with specific insight.

 

[DaHabes]

From memory, you can set an ignition delay on the sustainer motor. Set the booster to all zero delays, the sustainer to 2 second ignition delay and rocksim should have the booster separate at booster motor burn out but sustainer ignite after coasting for 2 seconds.

Nope. The sustainer ignition delays that amount of time from booster burnout, not booster ignition. That is how it should be as you want that functionality for air starts (staged rockets often sim higher with some built in delay between the stages). If you set all booster delays to zero, the two stages ignite in sequence as they should (as displayed in the 2D flight profile). With any booster engine delay, sustainer ignition is delayed until ejection time at which point the booster is dropped. Flight altitude is seriously lower with any ejection delay on any booster engine as forward momentum approaches zero at sustainer ignition with any booster delay.

 

[mjennings]

Hmm I'll have to look into a 2 motor (18mm) cluster to single sustainer (13mm) design I have. Thought it worked right. What version of RS are you using?

 

[DaHabes]

10.2