2 stage altitude

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jbr

In Remembrance 2023
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5-1 thrust ratio for the starting motor
what is a great thrust ratio for the upper stage for highest altitude?
 
Actually, for a 2-stage 10:1 TTW is recommended. Reason is to ensure no wind cock off the rail and obtain enough velocity to maintain straight flight during coast until 2-stage motor ignites.

You really need to do sims to find motor combination and 2nd stage ignition delay for best altitude.

This also highly depends on how high. On the recent MESO flight to 293k feet, he ran a long burn in the booster to keep the speed (Mach 2.5) & Drag down while in the lower dense air. Booster burn-out at ~6500ft, coast to 32kft then light the shorter burning 2nd stage to push velocity over Mach 4 in the thinner air.

I've been doing 2-stage in Class 1 rocket. G74 off the pad then 1 sec delay and lit a D15 in 2nd stage. This is really to keep the altitude lower due to smaller East coast field.
 
ok let me refine this, it is not really a 2 stage
I can make a dual thrust motor with a butt thumper 1st propellant and then a slow propellant
or have the same propellant for the whole burn
it is almost like an airstart of the slow motor
 
Oh...that is not something I have looked at.
Again a sim is the best.

Are you going really high where air density and drag drops off?
Or lower where the air density is still fairly high.
In the later case a long slow burn to keep maximum velocity (Drag) lower is best.

And since it really is only one stage at least 5:1 TTW is good.
 
The K76 demo flight that I saw at BALLS seemed to work fine. That motor has a kick off the pad and then a very long very low thrust sustain. I'd make sure that the initial kick gets the rocket up to a speed high enough for the fins to really do their job, and then launch on a calm day.
 
Yes this is for the hampster dance, minimum diameter 54mm, just got my propellant testing done in the aluminum casing, now need to finish the parts for the single use no metal motors, build them and test. Design on the rocket puts it around 2.5 pounds so the motor can be up to 2.5 pounds.
 
Thinking about this further I think I know what to do
 
For optmal thrust you want your sustainer thrust to be about twice weight, but only after you boost up to the sustaining speed at maximum thrust, and assuming that you will coast to apogee.
 
I can't find the rocsim or openrocket can handle air starts, I may be looking at making engine files for sims combining the high thrust and low thrust
 
Open Rocket can definetly handle airstarts. Look at the configuration tab, and then select the ignition method that you desire.
 
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