How to get nested motor (and tailcone?) in RasAero 1.02?

[Adrian A]

The RASAero webpage says that 1.02 supports a nested motor, and it shows a nice view of this with the MESOS rocket:

but I haven't seen how to do this when I do my own modeling. Also, is it possible to model a sustainer with a tailcone nested inside a minimum-diameter booster?


Here is a typical configuration for me:



What I have been doing in the meantime is modeling the exposed motor as an extension to the sustainer airframe and shortening the booster by the same amount. Being able to include the tailcone would be nice.

 

[Chuck Rogers]

Adrian:

For having a nested upper stage, see "Adding a Booster Stage with a Nested Upper Stage" section in the RASAero II Users Manual on Pages 39-44. Which I'm sure of course you have looked at, but this is for others reading this thread, who have questions on how to do a nested upper stage in RASAero II. Basically the portion of the upper stage nested in the lower stage is a very slight boattail.

Of course, now you want to add a second boattail, the boattailed aft closure on the upper stage motor at the bottom of the upper stage. Unfortunately, in RASAero II you can't have two boattails in the region nested into the booster stage. So unfortunately, that final boattail at the bottom of the upper stage will have to be left out. But at least the friction drag of the surface of the nested portion will be included for the upper stage, but not included for the booster stage, which of course is one of the purposes of nesting from the modeling standpoint.


Charles E. (Chuck) Rogers
Rogers Aeroscience

 

[Adrian A]

Adrian:

For having a nested upper stage, see "Adding a Booster Stage with a Nested Upper Stage" section in the RASAero II Users Manual on Pages 39-44. Which I'm sure of course you have looked at, but this is for others reading this thread, who have questions on how to do a nested upper stage in RASAero II. Basically the portion of the upper stage nested in the lower stage is a very slight boattail.

Of course, now you want to add a second boattail, the boattailed aft closure on the upper stage motor at the bottom of the upper stage. Unfortunately, in RASAero II you can't have two boattails in the region nested into the booster stage. So unfortunately, that final boattail at the bottom of the upper stage will have to be left out. But at least the friction drag of the surface of the nested portion will be included for the upper stage, but not included for the booster stage, which of course is one of the purposes of nesting from the modeling standpoint.


Charles E. (Chuck) Rogers
Rogers Aeroscience

You give me credit I don't deserve. Sometimes when you use a tool for years, you forget it has a manual.

 

[Chuck Rogers]

You give me credit I don't deserve. Sometimes when you use a tool for years, you forget it has a manual.

Adrian:

Actually, you're an advanced User. For advanced Users like yourself, there are some additional things you can do to model the second (the bottom, the aft closure) boattail on the upper stage. It's basically two separate RASAero II runs; one to match the drag coefficient (CD) and performance (altitude, velocity), one to check the supersonic Center of Pressure (CP) of the upper stage. While the aft closure boattail is short, it is at the aft end of the upper stage, and it is well aft of the upper stage fins. Boattails are destabilizing, and supersonic CP is critical, so it may be important to look at.

Like I said, I have some ideas, so you can take a look at the material and let me know how you want to proceed.


Charles E. (Chuck) Rogers
Rogers Aeroscience