Titan IIIe flight report

I got my Titan IIIe off the ground at Bong this weekend. This was a scratch build based on the old Estes kit, modded for powered, pop off boosters and a 29mm core MMT

Decals and booster nose/tailcones courtesy Sandman. Core nose and transition via the large Estes TARC pack. Overly thick lexan fins.



First flight was on E9-4 + 2xC11-0

Slo-mo to apogee:
https://youtu.be/lPuRdJ1obcI

Only minor damage. Lost one of the 8 booster holding posts.

I'm interested in thoughts on the lapboard booster.

The starboard booster hung on too long. The shock cord burned through and the nosecone fell free. The chute was tied below the burn, so the booster came down gracefully. And I'm already planning on a bigger chute for the core.

I guess I have to respond to save face for TRF given the feedback you got over on YORF.

Maybe attach this to your prior thread on TRF so folks don't get lost on this new thread with the same rocket???

Great job, all three lit. I hate CATO's! But it is best to happen on your three motor cluster, and a bit late in the burn which was nice because it was off the pad and had some momentum to keep it moving up. Now tell they guys what good rocket science you have when your three motor cluster survives a CATO with a good flight and minimal damage on only two motors.

Prior threads cross referenced:

https://www.rocketryforum.com/showthread.php?t=127179

I've been looking at the vid frame by frame. I'm amazed the larboard booster didn't part the shock cord or zipper. The CATO -really- stretches it out. Then you can watch the body flip up past the nosecone and chute. The boosters have a light Kevlar line anchored to the motor mount, with a couple lengths of 1/8" sewing elastic tied to it.

Sorry if this was explained elsewhere, but how are the SRBs detaching after burn out? Do they hang on until their nose pops off, then that allows them to fall away? I was trying to figure out how to do that a while back for another project.

Charles_McG said:

I've been looking at the vid frame by frame. I'm amazed the larboard booster didn't part the shock cord or zipper. The CATO -really- stretches it out. Then you can watch the body flip up past the nosecone and chute. The boosters have a light Kevlar line anchored to the motor mount, with a couple lengths of 1/8" sewing elastic tied to it.

Click to expand...

Weird things happen with CATOS! Sometimes it is not so bad, other times you just have to cry it out.:cry:

Each SRB has 4 posts made of 1/16" dowel glued in launch lug sections. 2 forward-aft facing posts. 2 rear-forward facing posts. There are matching lugs on the core. The nosecone has a short section of body tube glued to it - the posts are mounted on that. A piece of coupler serves as the new 'shoulder'. The rear posts transfer the thrust of the SRB. The forward posts carry its weight, should it fail to light. The aim is to blow off the nosecone at burnout to free the SRB body to be pulled back off the rear posts by drag. I was hoping the beefy 24mm booster would supply enough force to pop the nosecones. On the one that didn't cato, it did - but the booster didn't separate and the core continued flying, dragging a chute behind.

I may be dense but I am not getting what happened. Were all three motors ignited on the ground? One of the motors failed, right, but which one? The center one? Was that what flew on ahead of the rocket?

In any case, sorry about your troubles. Why does it always seem to happen to the rockets you spend the most time making look good? One of the little mysteries of this hobby... :confused2:

The core had an E9-4. The SRBs had C11-0s. All three lit nicely. A few lengths off the rod, the larboard C11 CATOs and spits its fuel plug forward, blowing off the nosecone and separating the SRB early. The rest of the stack continues. The starboard SRB fails to separate cleanly. All the parts recovered and the only real damage is 1 missing SRB post.

Lift off looked really good (straight up) until the cato. I am amazed that it was stable for so much weight (3 motors) in the aft end in what I would assume to be a light model. I would assume that you used Q2G2 igniters in the cluster. In a way this is a real switch. I would have assumed that the E9 failed and the C11's were fine, rather than the reverse.

The bigger tail weight are the lexan fins. I had 1/8th handy (free) and they weigh a ton.

I did a lot of testing and modeling. First a mini version, the Rocksim.
Mostly documented here:
https://www.oldrocketforum.com/showthread.php?t=15092

There's 50-75g nose weight. I've forgotten just how much. Right about 1 cal.

And I used the black tipped Estes igniters.

After much watching of the video frame by frame, I've decided that the starboard SRB failed to separate because it hung up on the core's Estes 29mm retainer - even though I had ground down the ridges. As I rebuild, I'm going to shim out the mounts about 1/32".