Rocksim HPR 2 stage question

How do you do a two stage correctly in Rocksim if the motors don't have a delay? I can't seem to figure out how to get the second one to light.

You have to trick RockSim into thinking that the motors have a delay. If you are going for a pure 2 stage, you set the delay on the 1st stage to 0 if you'll ignite the second stage at first stage burnout or you set the delay to whatever you have set your timer to. For example, if I'm staging an I357 to an H180 and I want the H180 to lite 1 second after the I357 burns out (what I have my timer set to) then I set the delay on the I357 to 1 second. If I have the flight computer set to ignite the H180 on the I357 burnout then I set the delay to 0.

Stay tuned for the next issue where we'll talk about ignition delays for air-starts in a HPR cluster.

-Aaron

Sounds good but I am looking at using K motors and the delays don't say zero, they say none. Is that the same thing?

Just highlight the "none" and put a number in there. It just means that the K motor comes as a plugged motor and has no delay but that doesn't mean you can't lie to RockSim.

-Aaron

I guess you could just lie to rocksim, who will it tell.

If you post the RockSim file as an attachment to a message on this forum, I am sure someone will look at it and let you know if it was done correctly.

I lie to and cheat the RockSim program all the time!

Bruce S. Levison, NAR #69055

Here is the rocksim file.

I believe you can control two events during staging.

1. When the two sections separate from each other (done by varying the "ejection delay" time for the booster motor).
2. When the sustainer motor lights (done by varying the "ignition delay" time for the sustainer.

The first time is useful if you want the stages to stay together until the rocket slows down below Mach. The total time from burnout to ignition is the sum of the two times.

Yep - that's how I've always simmed it. The motor delay determines time until separation of the stages, and the ignition delay determines time until the second stage motor lights measured from the separation.

Ian,

As you have it simmed, the booster separation occurs at motor burnout with its 18" parachute deploying one second after stage separation that occurs at burnout. You have the drogue parachute deploying at apogee and the main 60" deploying at 800'. The problem I see is that the two stage configuration is unstable with the motors installed; margin is only 0.4 calibers with the K and L combination using the RockSim equations for the stability estimation. You need to double the amount of nose weight to 10 pounds, see the attached RockSim file.

Bruce S. Levison,, NAR #69055

Thanks. It is definately more stable now. I just need to figure out the complexity of the booster stage if I were to go ahead and make this rocket 2 stages. I think I would make it without the booster stage first but compatible with a booster if I decided to make it.

heada said:

Just highlight the "none" and put a number in there. It just means that the K motor comes as a plugged motor and has no delay but that doesn't mean you can't lie to RockSim.

-Aaron

Click to expand...

I'm trying that but when I have a motor with "None" and "All" as options if I put "0" in and then try to launch it - Rocksim still complains. If I click out of that block anywhere the field reverts to "All" or "None" depending on what was there before I typed in "0".

I've uploaded an example. No it's not something I am trying to fly it was just a test of using the sample rockets in RockSIM and trying to put them into subassemblies. After doing so I started to try to figure out why I couldn't get the motors to work the way I expected...

View attachment silly-2-stage.rkt

uncle_vanya said:

I'm trying that but when I have a motor with "None" and "All" as options if I put "0" in and then try to launch it - Rocksim still complains. If I click out of that block anywhere the field reverts to "All" or "None" depending on what was there before I typed in "0".

Click to expand...

A 'feature' of this field is you have to hit enter after you put the number in. Otherwise it just reverts to the previous value.