D5 rockets

[gpoehlein]

You know, I got to thinking a couple days ago- Quest has had the D5-4 and D5-6 available for several years now, but they never produced a rocket designed specifically for that motor. They also brought out the motor tube and some centering rings, but still no rocket.

So my question is, has anyone here designed a rocket specifically for the D5? I'm thinking that a Quest 40mm body tube with matching nose cone (or reducer down to 30 or 25). Something that you could use N adapter in to fly on C6 or maybe B6 motors in an adapter. Basically, something about the size of a Big Bertha. In other words, something with a 20mm+ motor mount, not a 24 that is adapted down to the D5.

[Marc_G]

I love the D5 motors, but I tend to lose rockets on them due to having only a 500 foot radius around the pad for guaranteed recovery.

I had a bunch of them, actually still do. A great rocket for these on a larger field is a BT-50 downscale of the Blue Bird Zero, that I build specifically for this engine. I've built two of these, and lost them both. Eventually got the first one back (along with camera strapped to it) after 3 months in the trees. The second one is still AWOL (fortunately, no camera attached). The first was BT50 with the D5 motor mount glued in (I used tape wraps as centering rings), while the second was built as BT50 minimum diameter used with an adaptor for D5 engines.

BT55 version of Der Red Max also does well with this engine (mind the nose weight!), and Big Bertha has a fun ride too. Anything more massive may not be safe due to the low initial thrust off the pad. In still winds my full scale Der Big (green) Red Max has a good flight, but after about 7 mph winds, it weathercocks unsafely.

I'm considering a futuristic design using these in external pods. It would be rear-eject, off a central D5-6, (~10 seconds into flight, post-apogee) while the pods would be designed to pop off first using D5-4 engines. There don't seem to be D5-0 booster engines, though there are plugged D5-0s available. These are too weak to be traditional boosters, so no surprise there.

I have an adaptor made from one of the D5 motor tubes / thrust rings, with peeled out BT-20 to BT50 paper rings for centering. Actually, my adaptor is lost with the latest BBZ downscale, so I guess I need to make another one.

Since the bird needs to be lightish, it makes good sense to build for a D5 and then adapt down to B or C engines. I'd say a lightly-built Berta-esque bird would be a good choice. I tend to build heavy so I need to be careful with these...

Marc

[JPVegh]

Yeah I designed a D5 powered BT50 payloader to carry an Altimeter 2. Never built it and probably never will, it's one of many designs in my virtual open rocket fleet. It's a simple 3FNC with an OAL of 17 inches, OR shows it to go about 2200 feet.

OR Sims for Bertha sized rockets look a little scary with 36in launch rods. Probably best attempted on windless days. Perhaps why Quest hasn't released a kit?

[jbuscaglia]

While not built specifically for D5's, I've flown both a Semroc Goliath and an Estes Stormcaster on D5's, so I would expect that your proposed design would be OK. Both were flown in light winds. The Goliath was flown with a D5-P when they first came out. The "up" part was great. The altimeter ejection failed (operator error), so the "down" part wasn't so good. I used a D5-4 in the Stormcaster and it was perfect.

(Disclaimer: Your mileage may vary. Past results are not a guarantee of future performance. See your doctor for a flight lasting more than four hours.)

[Marc_G]

One more thing: A Goblin built to accommodate up to an E engine (so, accepts the 3.75" engines) does great adapted down to a D5.

[MarkII]

Rocket design for a D5?

Well, by now you should know what my my answer will be, Greg.

...for sure...


and probably also ....


The Quest D5 is very similar in performance to the FSI E5. So rockets designed for FSI's motor would be good choices to try on the Quest motor. I already know that the Orbit (first photo) goes great on it. Even too great, perhaps. (That's it lifting off on a D5-6. It was never seen again.)

[BEC]

I've done one purpose-designed rocket for the Quest D5s that has actually been built and flown once. It's a near minimum diameter rocket (based on Centuri/Semroc ST-8 tubing) just big enough for the motor, a streamer, and a $20 Adept ALTIM1 altimeter. Its sole purpose is to set club D impulse altitude records....

Its one outing from a sod farm in Pasco, WA in April reported an altitude of 2633 feet.

The other two I've flown on D5s have been a modded Quest Super Bird and Big Betty. Both turn in great flights if they don't tip off. If they do.....long slanting flights and a zipper.

I have Semroc Retro Repro of the FSI Oso that I'm considering making my next D5 rocket.

[Marc_G]

This thread has got me thinking to do a purpose-build for these engines. I've got plenty of engines (10 D5-4 and 7 D5-6). If I do the detaching booster thing, I can make it a pretty heavy bird, since it will have 3 engines.

Another, possibly interesting way to go would be have smallish side boosters with A10-0T in them, and a small central booster section also with an A10-0T. Stage from the mini engine to the D5-6 in the sustainer, and have small chutes/streamers in the side pods of the booster.

Or maybe a downscale of the Vagabond. 'Bond has been getting a lot of attention lately. A BT-55 version would be fabulous on D5 engines. My only problem is I don't think I own an appropriate nosecone for scale, but I could fake something pretty close from my parts bin. OK, done. I'm doing this!

Fun thread!

Marc

[JAL3]

Art Applewhite briefly offered a version of his Helix specifically designed for the D5. One is posted here: http://www.rocketryforum.com/showthr...462#post248462

It was withdrawn from public offering because the spinning rocket suffered burn through too often with the D5. That occasionally happens with other motors on that rocket but it was just about guaranteed on a D5.

[Marc_G]

I have a question, relevant to the thread but somewhat tangential...

I've heard of the "D5 burnthrough" often enough, but never experienced it myself. But why are some rocket designs more prone to it than others? I understand why some engines might burn through (thin casings not up to the sustained heat of the long-burning engine), but why would the rocket design matter? Is there some sort of design-specific cooling effet impacting the likelihood?

Marc

[JPVegh]

I have a question, relevant to the thread but somewhat tangential...

I've heard of the "D5 burnthrough" often enough, but never experienced it myself. But why are some rocket designs more prone to it than others? I understand why some engines might burn through (thin casings not up to the sustained heat of the long-burning engine), but why would the rocket design matter? Is there some sort of design-specific cooling effet impacting the likelihood?

Marc

In the case of the Helix it is a monocopter, the rotation of the rocket causes the burn to propagate outward causing burn through. As John has said this is more of an issue with the D5.

[Marc_G]

Thanks! I learn something every day. I wouldn't have thought that spinning at those kind of relatively low RPMs would make a difference, but apparently it does! I appreciate the info.

[JAL3]

I have a question, relevant to the thread but somewhat tangential...

I've heard of the "D5 burnthrough" often enough, but never experienced it myself. But why are some rocket designs more prone to it than others? I understand why some engines might burn through (thin casings not up to the sustained heat of the long-burning engine), but why would the rocket design matter? Is there some sort of design-specific cooling effet impacting the likelihood?

Marc

The Helix is a moncopter. It spins around like a propeller blade. Centrifugal force helps to burn through on the outside.

I can't speak for other designs.

==========

I wrote this a few hours ago but never hit enter. WHen I got home, I noticed and entered it but Jeff had already given the answer.

[MarkII]

I haven't seen any burn-through yet with my D5s, but this is something that has been reported on a few occasions with the Chinese-made Quest C6 motors, too. (I haven't see it with my own C6s yet, either.) The cause of it in the D5 is easy to diagnose; it's the long burn time, combined with somewhat thinner casings than those used by Estes. (Quest motor casings have always been thinner-walled in comparison to Estes motors; this was true of the German-made motors, too.) With the D5, the combustion chamber inside the casing has to support a burn lasting 4.6 seconds. Compare that to the burn time of 1.65 sec. in an Estes D12 (which also has a larger casing). The Chinese-production Quest C6 also has a significantly longer burn than the Estes C6 - 2.54 sec. vs 1.86 sec. Especially with black powder, longer burning motors are hotter burning motors. These longer times lead to more erosion of the interior of the Quest casings, which on rare occasions can continue until it almost perforates the exterior of the case.

The centrifugal forces produced by the rapid rotation of the monocopter produce atypical stresses on motor casings that they were not specifically engineered to handle. It concentrates more of combustion pressure onto one side of the casing interior, causing a hot spot. The casings of motors up through B impulse and the 24mm Estes C11 can handle the lateral pressure without any problem; their burn times are so brief that the exteriors of these motors don't show any evidence of hot spots. The problem has been reported with both Estes and Quest C6 and larger black powder motors.

[Marc_G]

This thread has got me thinking to do a purpose-build for these engines. ...

...maybe a downscale of the Vagabond. 'Bond has been getting a lot of attention lately. A BT-55 version would be fabulous on D5 engines. My only problem is I don't think I own an appropriate nosecone for scale, but I could fake something pretty close from my parts bin. OK, done. I'm doing this!

My BT55 Vagabond is coming together. I got decals from Excelsior. Used a printed-to-scale copy of the fin sheet to guide fin creation. Fins are on and sealed with thin CA. Later today will decide whether to go traditional baffle/shock cord or try out a zipperless design.

The motor mount will be a one of the D5 mounts, and I'll make an adaptor for 18 mm engines as well.

I'll make a thread for it, eventually.

[JStarStar]

It is kind of strange that Quest has not whipped up a couple of kits to accommodate the D5. Plenty of their existing models (Courier, Big Betty for starters) could be easily adapted; it's not like they would have to retool their whole product line.

All they would really have to do would be to take a couple of their existing models, provide an appropriate motor mount, rename it, give it new decals, and voila, you have a D5-capable rocket.

Although to really showcase the D5 to its best advantage, they probably would want to come up with a couple of high-performance minimum-diameter 3FNC designs using a 20mm tube (I suppose then we'd find out for sure about the overheating/glue-melting issue).

[dpower]

21mm FSI clones work great, and they leave room to wrap a bunch of masking tape around the motor to keep it from burning through the airframe. I do like these motors, they simply need thicker cases. And a longer delay.

[BEC]

And a longer delay.

Agreed. That said, I just ordered another handful of them during the Quest sale (which is on for a few more hours - until midnight Mountain time tonight)