Titan III C build Scale 1/54

[Raptor 2]

Lower booster support frames installed. Constructed from plastic model spruce. Glued on to tubes with you guessed it RC Modellers Canopy glue. Added conduit raceways to the solid boosters. Raceways made from Evergreen half round 2.5 mm plastic strips and secured to the boosters with 3M double sided tape. Less messy than using glue. Glued the plastic fins to the fin tubes with RC glue and painted the tubes black.

 

[Raptor 2]

Oops

 

[Cape Byron]

Just looked and my hobby tool supplier sells the Deluxe Materials canopy glue. I'll add some to my next order. Thanks for the tip!

 

[Scotty Dog]

Very nice.

 

[Raptor 2]

Very nice.

Thanks Scotty. I’m almost done. Just a few more details to add.

 

[Raptor 2]

Just looked and my hobby tool supplier sells the Deluxe Materials canopy glue. I'll add some to my next order. Thanks for the tip!

Your welcome. All the boosters and catalyst tubes are glued on using this stuff along with the fins.

 

[Raptor 2]

Have completed the final detailing by adding straps to the catalyst tubes, separation rockets to the lower ends of the boosters and UTC decals. Added horizontal structural rods to the upper end of the boosters to main frame.Still need to add on the 3/16” launch lugs And the shock cord to the interior. Will double check stability on OR and add weight to nose cone as required. Had to order lugs from Allrockets so not done yet. Intend on using a 27 or 30” chute depending on final weight.

 

[prfesser]

I'm curious: do the catalyst tanks feed into the SRBs? It looks like they do. Wondering what kind of catalyst is injected near the aft end of a solid booster, where combustion is already almost complete. It's a little strange.

Best -- Terry
PS: Love the project!!! I've always liked the Titans, especially the IIIC and the IV.

 

[Raptor 2]

I'm curious: do the catalyst tanks feed into the SRBs? It looks like they do. Wondering what kind of catalyst is injected near the aft end of a solid booster, where combustion is already almost complete. It's a little strange.

Best -- Terry
PS: Love the project!!! I've always liked the Titans, especially the IIIC and the IV.

You are correct. Nitrogen Tetroxcide is injected in the aft combustion chamber exhaust flow deflecting the exhaust flow and creating a torque in the opposite direction of the injected fluid. That’s a mouthful! Why? You would have to ask the engineers. It might just make the rocket start a slow roll.

 

[aerostadt]

Gimballing or vectoring a large solid rocket nozzle (or probably any solid rocket nozzle) is not easy. The old Minuteman had a split-line nozzle or I would call it sort of a ball and socket. (Actually, the MinuteMan first stage had 4 nozzles. Two each were locked diagonally and moved together. In this way they could vector the vehicle in any direction.) The Space Shuttle SRB's (or RSRM's ) used a flex bearing and could vector in any direction. The Nitrogen Tetroxide (N2O4) on the Titan III was injected into the divergent or supersonic section of the nozzle. The whole nozzle was fixed and could not move. Of course, N2O4 is very reactive and can easily decompose on its own. However, SRB's have a lot of unburned hydrogen in their exhaust (The free H2 lowers the exhaust molecular weight and increases the specific impulse when it is not burned.) I suspect some of the oxygen from the N2O4 burned with the H2. In any case the N2O4 injection in the divergent section was capable of producing oblique shock waves in the supersonic flow and changed the direction of the flow in effect vectoring a nozzle that was structurally fixed.

 

[Raptor 2]

Well said. You know your stuff!

 

[Raptor 2]

Finally worked up the nerve to launch the Titan. Weather was perfect, sunny, 8C, no wind. Weight without motor but including a 30" nylon parachute 352 grams, 12.42 oz. Engine Aerotech Composite E30-4
Initially took off straight but then the fin tube on one side rotated into the engine exhaust and slipped partly out of the solid booster tube resulting in a loss of stability and corkscrewing commenced. Luckily the chute came out before she landed and there was no damage to the model. Will have to secure the fin tube better and try again. At least she flew straight in the beginning proving she is stable if all remains the same.

 

[aerostadt]

Gorgeous lift-off on a beautiful day. The initial straight flight got enough altitude to off-set the late flight instability. It looks like an E30-4 is a good motor for this model.

 

[rkoenn]

A very cool build of one of my favorite rockets. I've seen a dozen of them liftoff from fairly close by at KSC/CCAFS and VAFB over my years with NASA and on my own road trips. The first was in the fall of 1971 when me and a couple of buddies drove over from our first quarter at FTU in Orlando to watch a military mission. I've also seen two blow up big time, one only 500' up while at VAFB around 1986 and then another around 2000 from CCAFS out over the Atlantic. Here's my shot from the press site for a Voyager launch.

 

[Raptor 2]

Thanks for the likes guys. The Titans are my favourites for looks. Working on fixing my rotating fin tube problem and have also started constructing a Titan III C MOL 1/54 scale. Will refly the Titan III C soon once the fin tubes are secured.

 

[Raptor 2]

Repaired the loose fin tube problem by drilling a 1/8” hole thru the bottom cylinder and the fin tube and inserting a plastic shaft of a small brush. This secures the fin tube from moving backwards out of the booster and from rotating around the long axis. Slightly miss aligned on one of them.... Also visible is the burn mark on the fin from the first launch attempt. Plastic pins are removable but are a tight pressure fit inside the booster.

 

[Raptor 2]

Flew it for a second time with the fin tubes secured. She flew straight again for the first 100 feet or so and then it lost stability again. Checked OR and the stability is near 2. I had oversized the fins when I scaled up the Estes BT 60 model to a BT 70. I increased the fin size a bit more then the calculation dictated for the scaling up. Maybe this is the problem. The Estes model did not show any weight being added to the nose cone area.
The rocket landed with chute open but busted a plastic fin on the gravel parking lot. So I am contemplating adding weight to the nose cone or decreasing the size of the fins back to what they should be. Decreasing the fin size would decrease the weight on the back end moving the CG forward. Less weight is always better. Will run scenarios on OR and see what happens to the stability number. my understanding there, is it should be between 1 and 2. It’s bad below 1 or above 2

 

[jqavins]

Is that really heavy fin material? I wouldn't think so. There are times when shrinking the fins moves the CG more than it does the CP, but I wouldn't think this is one of those times, as the fins really don't look oversized.

When the static margin is to large it means you'll get excessive weather cocking, not instability. What's too large is a matter of debate and opinion. Many people fly with margins over 2 and do not have problems.

What was the motor on the second flight? As heavy as this is you need a punchy one. The first flight's E30 is plenty punchy (in my mindsim, which is not the best) so if the second flight used the same then I doubt that's the issue.

 

[aerostadt]

I modified the Estes Titan IIIC to have an X-20 and clear plastic fins and flew it on a D12-3. It flew fairly well, but wobbled a little bit towards the end of the flight. I think my fin size was near yours, but, of course, I had forward fins. Clear plastic fins can break easily, especially, in my case clear plastic fins glued to clear plastic tubes.

 

[Raptor 2]

Is that really heavy fin material? I wouldn't think so. There are times when shrinking the fins moves the CG more than it does the CP, but I wouldn't think this is one of those times, as the fins really don't look oversized.

When the static margin is to large it means you'll get excessive weather cocking, not instability. What's too large is a matter of debate and opinion. Many people fly with margins over 2 and do not have problems.

What was the motor on the second flight? As heavy as this is you need a punchy one. The first flight's E30 is plenty punchy (in my mindsim, which is not the best) so if the second flight used the same then I doubt that's the issue.

Each fin weighs 8.16 grams for the set I flew with. The smaller fin would weigh 1.96 gr. less by taking 17 mm off the back edge. With the small fin in place stability is 1.64. Stability as I flew her was 1.98 Both flights were with E30-4 composite Total weight without the motor in place as she flew was 352.56 gr. 12.4 oz. She went end over end at about 100 ft or so up. Enough altitude to have the chute come out. Just watch a untuned video on OR where they said the stability should be between 2 and 3.

 

[Raptor 2]

I modified the Estes Titan IIIC to have an X-20 and clear plastic fins and flew it on a D12-3. It flew fairly well, but wobbled a little bit towards the end of the flight. I think my fin size was near yours, but, of course, I had forward fins. Clear plastic fins can break easily, especially, in my case clear plastic fins glued to clear plastic tubes.

Once you take scaling up to a BT 70 tube the fins look about the same size. Your fins appear to be a little further back relative to the booster nozzles then the one on mine. Clear plastic gets a bit brittle in colder weather also.

 

[Raptor 2]

Modified the main frame by cutting the top off 40mm below the nose cone. Constructed coupler with two centering rings and a BT 20 tube inserted to the underside of the top of the nose cone. Made another tube with a cap on top. This tube will be used a friction fit plug to hold the lead fishing weights in place at the top of the BT20 tube. The plug is removable so I can adjust the amount of lead weights in the nose cone. I’ll secure this to to the main frame with a small shock cord just in case it comes off when the ejection charge goes off. Will try 20 gm of weight on the next try. Can go up to 32 gm before my liftoff weight is greater than the motor can handle. Hopefully this cures the instability problem.

 

[Raptor 2]

Completed the modifications noted above which added 19.55 grams wt. and then added 20.29 grams of weight to the nose cone. Total weight less the motor an E30-4 came in at 392.40 grams. OR had stability at 2.35 caliber.
Wind 5 km / hr sunny +18 C. Angled the launch pad slightly so that the rocket wouldn’t end up on the highway as it may go unstable again. It’s had a bad track record so far.
Flight was successful and rocket appeared to hit the altitude called for in OR of 180 meters. Maybe a little less as it was launched at an angle. Flight was arrow straight with no weathervaning. Chutes out at apogee and a good landing with no damage. Will try a little less weight in the next flight.

 

[aerostadt]

Flight looks excellent!