Quote:
Originally Posted by closet astronaut
You sound like you have extensive experiance in launchable rockets. I have a question. My step mom's father and his boys did quite abit of rocketing years ago, they used to tell stories of a sat v they launched that used smaller engines and could make the rocket come off the pad slow like the real thing. Now in all the years of launching model rockest I've never duplicated this or seen or heard of anyone doing this. I'm wondering if this would even be possible, using a large rocket with mutiple engines say three or four, the only problem I can see would be getting all of them to lite at the exact same time. I think this would be the ultimate launch, lots of smoke and a slow steady lift off.
On you'r Atlas I noticed no stablizer fins, mybe because of the smaller size? Mine has stablizers that slide into the outer engine bells with the engine mounted in the center. The cause of the bad flight was that the engine pushed it's mount up into the main body and threw of the trajectory, it parcially melted the center engine bell. It hit the ground before the cone ejector detinated, there was some tube crushing also.
And yea this is the estes, it's three and a half diameter and about thirty six inches length from engine bell to tip of the LET.
Ok ..I went back and looked at you'r pics again, the flames are the stableizers, I thought at first they were just for a realizm effect. I like those much better than what came with the estes.
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Hi... try to answer some of your questions...
I have some experience launching rockets... I was in it from about 85 to about 91, dropped out of it for awhile, and started back up again about 6 years or so ago... pretty fun. I enjoy building as much if not more than flying, actually. I've picked up a lot of neat tricks from the Dr. Zooch Rockets kits, and the papermodeling techniques he uses inspired me to get interested in paper modeling too... LOTS of absolutely MIND BLOWING projects over here!
I'm not sure I know what Saturn V you're talking about. Basically, AFAIK, there have only been two basic sizes of Saturn V's produced in large numbers for any length of time... The Estes 1/100 scale Saturn V (with almost a 4 inch diameter main body tube) and the BT-60 "sport flier" version Estes produced a little later on (1.637 diameter, which works out to about 1/242 scale). It is this smaller version (BT-60 tube) that Dr. Zooch replicates and improved upon for his Saturn V kit. I have one and it's a nice kit, flies well, but only uses a single black powder Estes rocket motor. Now, in the 1/100 scale, Estes and Centuri both produced kits in this scale, and so did Cox IIRC. The only other "variants" of the Saturn V are the Apogee Components 1/70th scale (using high power rocket motors due to it's LARGE size) and the Quest Micro-maxx plastic version, made for 1/8A rocket motors (about 3-4 inches tall at most!)
The 1/100 Saturn V is a popular kit for clustering (installing multiple Estes black powder rocket motors ignited simultaneously at liftoff). There are even some commercially produced motor mounts designed for it, though making one yourself isn't particularly hard. The usual choices for motors typically use 13mm diameter or 18mm diameter A, B, or C class booster motors with a cental 24mm diameter "D" motor in the central motor tube that does most of the rocket propulsion, slightly augmented by the outer motors, and which also provides the time delay and ejection charge to deploy the parachutes. Of course it's ESSENTIAL that this motor is ignited (and of course highly desirable that they all ignite) and this factor has been greatly simplified by the release of the Quest Q2G2 low-current rocket ignitors, which are a quantum leap above the older Estes style nichrome and pyrogen ignitors that require between 1 and 2 amps to ignite... the Q2G2's only require about 150 milliamps to ignite! Plus they have extended multistrand insulated wire leads that make wiring them together into parallel circuit clusters for igniting multiple motors a snap!
The MAIN issue with "slow steady liftoffs" is that model rockets, unlike their larger NASA bretheren, are stabilized passively by aerodynamic means... without sufficient airspeed, the fins do not generate enough force to keep the rocket travelling vertically upward. IOW, it 'keels over" and hits the ground. A typical thrust/weight ratio for a model rocket is in the 5:1 range, at a minimum, whereas of course NASA rockets are typically in the thrust/weight at liftoff range of about 1.1:1 or so... so naturally the NASA rockets lift off MUCH slower...
This can be partially overcome by using LONG launch rods or rails to allow the rocket more time to accelerate while guided by the rod, until it's gained sufficient airspeed by the time it flies off the end of the launch rod to ensure aerodynamic stability.
If you're really interested, there's TONS of good information on all this over on
The Rocketry Forum ,
Ye Olde Rocket Forum - powered by vBulletin , or
Rocketry Planet which I'm sure could better answer your question than I, in greater detail...
That's a shame about your Atlas... That's the nice things about the forums-- lots of tips/n/tricks that can make the difference between having problems like you mentioned and having a successful flight. And, of course when something DOES happen, tips on repairing it...
You say the engine slid forward under thrust?? Was it a failure of the centering rings or the motor retaining hook??? This could easily have been prevented with a motor block, in the event it was a hook failure... Dr. Zooch has instituted "beefing up" procedures in all his instructions to strengthen the motor mounts to prevent such problems. Tube damage on an uncommon size tube (Estes didn't use that size tube on any other rocket that I know of, with the possible exception of the "Big Daddy" kit, which could be used for parts if it IS the same tube size!) Of course there are ways of MAKING a repair tube... the easiest being to get a BT-101 tube (4 inch tube from the Estes Saturn V, available from Semroc Astronautics company in North Carolina, offering their own wide selection of rocket kits and parts BTW). The 4 inch tube can have a "slice" taken out of it vertically along the long axis of the tube of sufficient width to reduce the tube diameter (circumference) to the size of the Atlas tube... this "slice" or strip can then be easily used for a "glue tab" and used to rejoin the two edges of the tube so they're flush with one another... This is the easiest method of obtaining "irregular sizes" of paper tubes.
The augmentation fins you mentioned were used on several Estes kits, most notably the Atlas, Space Shuttle, and Titan IV. Of course none of the REAL rockets (prototypes) had fins, requiring the use of augmentation fins installed in the boosters to create aerodynamic stability. Dr. Zooch's early kits used similar looking augment fins, but soon folks started painting them with a 'fade' paint job (sorta like mine on the Atlas above) and so he started experimenting with changing the shape and size of the fins to appear more like "flames" coming out the back of the rocket... once flight testing proved the concept, he patented it and sells them in his kits as "Flame Fins"... a novel approach to creating aerodynamic stability on rockets whose prototypes had active guidance and therefore no or undersize fins, while using readily available rocket materials (paper tubes and balsa wood) using standard adhesives (yellow wood glue and white glue). The other commonly used method is clear plastic fins-- some kits come with pre-cast plastic fin units that install in/over the rocket to provide clear fins, and many scratchbuilders use CD jewel case covers or lexan from the lumberyard cut to make clear fins... I've been tinkering with the idea of using slide-in fin units like the Dr. Zooch flame fins, only utilizing a clear plastic tube with clear lexan fins glued to it... so they're not as noticeable in flight... but I havne't tried it yet...
Later and thanks for your interest! OL JR