AeroTech Open Thread

[3stoogesrocketry]

Did you mean "Bonneville" ?

Dave F.

Yes Dave. I'm not sure how or why my auto correct did that .

 

[Ez2cDave]

Yes Dave. I'm not sure how or why my auto correct did that .

I hate auto-correct . . . I like to call it "auto-guess" - LOL !

Dave F.

 

[Rocketjunkie]

Warp-9 + hot weather = BOOM. J1999 drag race at LDRS a few years back - IIRC - 10 of 12 catos.

 

[Nytrunner]

Warp-9 + hot weather = BOOM. J1999 drag race at LDRS a few years back - IIRC - 10 of 12 catos.

Is there a particular reason for this?

 

[H_Rocket]

Because there was a design flaw with that specific motor geometry. Aerotech pulled it back shortly thereafter and redesigned it as the J1799.

 

[Rocketjunkie]

Is there a particular reason for this?

Apparently there is a higher burn rate/temperature sensitivity of this propellant than most. Even before the J1999, it was a J2135, downgraded to the J1999 due to problems. Note there has been no problems with the 2 grain J1299.

 

[TimothyG]

What would the chances be of getting a -0 delay quest motor for staging to a traditional black powder motor? Has something like this ever been considered? It would be fun to do some18mm min dia two or three stage rockets starting with one of Aerotechs D 18mm motors staging to traditional black powder. I ask this not knowing what the grain geometry is like inside of their 18mm motors. If it's a slotted grain going to a delay element I could see how this might not work but if it's end burning configuration it could maybe work.

 

[Nytrunner]

Q-jets are slotted grains open to the delay element. Therein lies the issue of composite direct staging.

Standard practice is not to reduce a delay below 4 seconds with an open grain to prevent chamber pressure rupturing the delay element. Q-jets dont have lower than 4 second delays.

Academically, I wonder if the 4 second restriction is necessary on such small motors, but the proof is left as an exercise to the reader.

 

[dhbarr]

Q-jets are slotted grains open to the delay element. Therein lies the issue of composite direct staging.

Standard practice is not to reduce a delay below 4 seconds with an open grain to prevent chamber pressure rupturing the delay element. Q-jets dont have lower than 4 second delays.

Academically, I wonder if the 4 second restriction is necessary on such small motors, but the proof is left as an exercise to the reader.

End burner could be a -0, but I can confirm slot-29's definitely do fail sub -4.

There's supposed to be a method of finely counterdrilling to achieve ooen-grain -2's, but I haven't gotten that to work.

 

[BayouRat]

Bring back Thermalite.

 

[grouch]

Make it stop.

 

[Jacob Ritzke]

Do we have an update on the G8st-p?

 

[tfish]

Gary just posted this on FB...

For all those who have been asking, the G8 fiberglass casings have finally arrived, and we are in the process of making the first production batch.

 

[Jacob Ritzke]

Awesome!

 

[Nytrunner]

Oh man, 6.4 oz rocket for a 5:1 thr/wt......

 

[dhbarr]

Oh man, 6.4 oz rocket for a 5:1 thr/wt......

Buy an Aspire and throw away all the extra mass.

 

[TimothyG]

I'm definitely going to have to fly my estees orbiter on this.

 

[afadeev]

Oh man, 6.4 oz rocket for a 5:1 thr/wt......

5:1 is sooooo blase.
Don't be a slave to static ratios!


a

 

[Nytrunner]

5:1 is sooooo blase.
Don't be a slave to static ratios!


a

I'm only concerned with the thr/wt necessary to get it going fast enough without a 50' rail......

 

[afadeev]

I'm only concerned with the thr/wt necessary to get it going fast enough without a 50' rail......

Use case #1: sustainer
Use case #2: TVC mount

I will order a half dozen, once they hit the inventory stock.

a

 

[slothead]

Hey Charlie, when are you going to have the old style black hats back in stock? I would love to have one.

 

[beeblebrox]

Q-jets are slotted grains open to the delay element. Therein lies the issue of composite direct staging.

Standard practice is not to reduce a delay below 4 seconds with an open grain to prevent chamber pressure rupturing the delay element. Q-jets dont have lower than 4 second delays.

Academically, I wonder if the 4 second restriction is necessary on such small motors, but the proof is left as an exercise to the reader.

It's due to physics... 4 sec = about 1/8" of delay propellant...less than that is not strong enough to hold the pressure of the propellant chamber just moments prior to burnout. It would blow thru early and inconsistently if drilled deeper or a shorter piece of delay material cut's cut length. Another point, since electronics are not six figure income toys anymore, you could use a timer for upper stage ignition, I think eggtimer has something that can do that.

 

[Steve Shannon]

It's due to physics... 4 sec = about 1/8" of delay propellant...less than that is not strong enough to hold the pressure of the propellant chamber just moments prior to burnout. It would blow thru early and inconsistently if drilled deeper or a shorter piece of delay material cut's cut length. Another point, since electronics are not six figure income toys anymore, you could use a timer for upper stage ignition, I think eggtimer has something that can do that.

That’s true, but the official burn time ends when thrust (proportional to pressure) is at 5% of what it had been. Burn time varies, so in some rockets it could be a quarter second or more longer than the “official” burn time. Delay grains burn much faster than 1/32” per second while the motor is pressurized, maybe five times as fast, so it’s possible that a motor could be just winding down when that four second minimum expires.

 

[rharshberger]

It's due to physics... 4 sec = about 1/8" of delay propellant...less than that is not strong enough to hold the pressure of the propellant chamber just moments prior to burnout. It would blow thru early and inconsistently if drilled deeper or a shorter piece of delay material cut's cut length. Another point, since electronics are not six figure income toys anymore, you could use a timer for upper stage ignition, I think eggtimer has something that can do that.

Either a Eggtimer Quantum or a Eggtimer Proton is capable of igniting a second stage.

 

[Ez2cDave]

Looks like an interesting upper stage motor . . . Maybe an F50, as a booster !

 

[afadeev]

For all those who have been asking, the G8 fiberglass casings have finally arrived, and we are in the process of making the first production batch.

Great news, thanks for sharing.
Any word on G11's?

 

[Jacob Ritzke]

I think the casings of those were getting too hot so they woun't be available for a long time if at all.

 

[tfish]

They did test fire a......38mm DMS H26ST-P endburner static test, 245 N-sec., 9.5 second burn....today.

Tony

 

[TimothyG]

I was hoping it was 29mm. Either way it’ll be a fun motor.

 

[STXFlyer]

I was wondering if anyone has tried to cut down the propellant grain in an 18mm D24 rms reload to get something more like C performance out of it? Making a new grain adapter spacer seams easy enough. Any experiance with this out there?