I800 insanity

[watermelonman]

Anyone flying the I800 on relatively thin rockets? I have a larger rocket that loves the K2045, and the rocket in question has done quite well on I566 and I540, but I was shocked to see the I800 simulation showing so much more acceleration than even these other crazy flights.

 

[3stoogesrocketry]

Your total impulse is so much lower , you will not see the same speeds as the I540.

Eric

 

[COrocket]

What's a "thin" rocket? I'm assuming close to minimum diameter? If it has done well on an I540 then it should do fine since the I800 is less impulse. Normally it's speed that destroys rockets, not acceleration.

 

[watermelonman]

Right, the speed is a going to be a good deal lower but the acceleration number jumped out at me. I mean, I do not think I have seen anything else claim to be in the 3000s of ft/s/s before, and even the 2000s I see are on the lower end of that range. I half imagine the motor taking the mount straight through the epoxy and body upon ignition.

 

[Sooner Boomer]

The I800 is a real kick in the pants. Thrustcurve says the motor puts out 180 lbs (800N) of thrust for a half-second. I think the acceleration/jerk is going to severely stress just about any airframe this side of a greyhound bus.

 

[mpitfield]

Hmm looks like an interesting motor. I wouldn't rely on the motor eject though.

 

[COrocket]

...I half imagine the motor taking the mount straight through the epoxy and body upon ignition.

I've never seen any high power rocket fail in this manner. People have launched ordinary blue tube rockets on Aerotech I1299s. As long as the rocket doesn't have any non-traditional construction techniques, you will be just fine.

 

[bobkrech]

With a lightweight 12 oz. MD rocket similar to a shortened LOC Weasel, the CTI I800 can pull a fierce 136G or ~4,000 fpsps, and the AT I1299 can pull an outrageous 225G or about ~6,000 fpsps. Both flights would have a Max-V around 1,900 fps to 2,000 fps with an apogee ~9400' if the rocket holds together. The issue with either is the potential for column buckling, or in plain English, folding the airframe over.

Check out https://www.bpasa.com/NERRF.htm for NERRF 3 and the X-16 flight, a LOC Weasel on an I-540. It folded over at 1050 mph (~1540 fps) but the rocket was 42" long and column buckling depends somewhat on the L/D ratio.

Bob

 

[Viperfixr]

Flew my Lil'Dog DD on one at the last Tripoli Vegas Oktoberfest. Sounded like a cannon going off, then the echo--loved it! The 3lb FWFG Lil'Dog took it, no problem at all, as did the Stratologger and the Duracell 9V.

 

[CzTeacherMan]

TRF user "DJS" flew an I800 on a Wildman Interceptor Sport and Midwest Power. 54mm airframe, 38mm hole, small body rocket. Fantastic flight. Headsnap... As in the entire crowd watching got whiplash. Got it back NO problem whatsoever.
High impulse/Short burn motors aren't as huge a deal as you think. The moment the fuel burns out, the rocket is decelerating. The real punishment of airframes comes with high impulse/long burn motors... As the high impulse burn continues putting force on the rocket, pushing it faster and faster and faster, the stresses on the airframe continue to build. However, there's not a whole lot of motors in the 38mm range that can overstress a properly built fiberglass airframe.

 

[watermelonman]

TRF user "DJS" flew an I800 on a Wildman Interceptor Sport and Midwest Power. 54mm airframe, 38mm hole, small body rocket. Fantastic flight. Headsnap... As in the entire crowd watching got whiplash. Got it back NO problem whatsoever.
High impulse/Short burn motors aren't as huge a deal as you think. The moment the fuel burns out, the rocket is decelerating. The real punishment of airframes comes with high impulse/long burn motors... As the high impulse burn continues putting force on the rocket, pushing it faster and faster and faster, the stresses on the airframe continue to build. However, there's not a whole lot of motors in the 38mm range that can overstress a properly built fiberglass airframe.

Yes, if it was fiberglass I would probably let it rip. It was one of my first rockets, though, initially built with cardboard, wood, and Bob Smith 5m epoxy. I have since discovered that I enjoy abusing it, and gave it a single layer of 2oz fiberglass with West 105. It takes I540s and J290s all day, but the I800 makes me think twice about the internal bonds.

 

[dixontj93060]

I sheared fins on a PML Ariel with an I800. Poor flutter profile on those kits--definitely must reinforce that one. On yours couldn't say as you don't give any fin/airframe parameters to calculate flutter risk.

 

[watermelonman]

I sheared fins on a PML Ariel with an I800. Poor flutter profile on those kits--definitely must reinforce that one. On yours couldn't say as you don't give any fin/airframe parameters to calculate flutter risk.

Oh, it started life as a Nuke Pro Max, so the basic triangular fins. Is flutter more of a risk with increasing acceleration or velocity?

 

[bobkrech]

Oh, it started life as a Nuke Pro Max, so the basic triangular fins. Is flutter more of a risk with increasing acceleration or velocity?

Velocity. It's aero-elastic effect. See https://www.ewp.rpi.edu/hartford/us...ion docs from JMRC/Example_of_Fin_Flutter.pdf for the description. The physics is there too, but it may be more than you want to know.

Bob

 

[T34zac]

I the I800. There's cool motors, and there's REALLY cool motors. I've flown this motor four times. Three times in the rocket I got my L2 with, and once in a minimum diameter (and with what I know now, I'll be the first to admit) that was improperly built. It reached Mach 1 and 100Gs before falling apart, everything that was worth anything (motor casing, tracker, altimeter) came back without damage. Easily one of the most spectacular 'flights' I've ever seen.

My new 38mm minimum diameter sims to about 10,500' and 160Gs. I'm not sure I'm going to attempt that flight anytime soon.

But I'd love to put this into my Darkstar Jr. Definitely would be a fun flight to watch. Probably get some good whistle out of it too.

 

[g zilla]

I ve flown 3-4 flights on this motor. 1 was a night flight 4" rocket with 3200 + leds. The other 2 or 3 flights on 54mm fiberglass rocket. It hauls azz.

 

[3stoogesrocketry]

So after re reading your first post , why are you concerned about the I 800 if you have flown a K2045 in the airframe before ?

Eric

 

[markkoelsch]

So after re reading your first post , why are you concerned about the I 800 if you have flown a K2045 in the airframe before ?

Eric

He has not- it was a different rocket.

 

[djs]

Got it back NO problem whatsoever.

Well technically it was 2.25 miles away, and after following my tracker thru 3 farm fields and falling into a ditch, I did find it with no airframe damage, other than a loose rail button. I'll definitely fly that again at MWP14

 

[CzTeacherMan]

Well technically it was 2.25 miles away, and after following my tracker thru 3 farm fields and falling into a ditch, I did find it with no airframe damage, other than a loose rail button. I'll definitely fly that again at MWP14

This time with a Chute Release...

 

[watermelonman]

So after re reading your first post , why are you concerned about the I 800 if you have flown a K2045 in the airframe before ?

He has not- it was a different rocket.

Mark is correct. Sorry if that made the topic unclear, all I was trying to say was that I am fairly familiar with vmax motors. In fact I flew another K2045 again yesterday!
[video=vimeo;150595672]https://vimeo.com/150595672[/video]

That is Vimeo number 150595672 for those whose browsers disagree with the forum.