UPDATE: Estes is now making them again - I have some due to arrive shortly! Yea!!!!!
The Beta Iris is special in my fleet because until recently it was the only two-stage rocket I ever built and flew. The theory behind the two-stage is that the rocket can go about twice as far and then some on the same amount of propellant or "rocket fuel". After half of the propellant is burned up, the lower motor and its extra fins drop off, allowing the second stage to take over.
The lower or booster stage takes some of the fins with it, reducing both the weight and drag of the fins and body. The second (and now lighter) stage can then continue accelerating beyond the speed of the first stage to achive even greater speeds than if the entire rocket remained as one piece.
I think the small size of this rocket combined with its high-altitude capabilities is better off with a bright Mylar streamer instead of the 10" parachute. This makes it easier to spot in the air and on the ground, and reduces drifting in the wind.
This rocket was recently given my Iris modification, which extends the body tube about 5 inches above the streamer/parachute bay, and allows for a payload with an altimeter to measure altitudes. (Iris is named after the Greek god of the rainbow. She is a messenger of the gods, linking the gods with humanity.)
The A-power booster and A-power sustainer really lift this Beta high, over 700 feet on just two A's! I'd say that's pretty good proof that multi-stage rockets are more efficient with propellant, as the same mass of propellant made into a single B-motor would have topped-out at about 500 feet. (A "B" motor has twice the energy of an "A" motor, and so on through the alphabet, so that if there was a "Z" motor, it would be incredibly powerful.)
After a bad wreck, I had to re-restore this rocket for more flying, since I didn't have any other rocket to use the little booster motors. Here is the Beta rebuilt, a little longer body tube, and a slightly smaller payload. The black stripes mark the payload section on the top and the added body tube below that.
After a repeat bad wreck, I'm rebuilding it again. This time I had to trim a little off the body tubes, so now she's a bit shorter and lighter.
What's great about this kit is you can fly a two stage very economically, since T motors are cheaper than standard sizes. This rocket has flown higher than the Revel Casino Towers in Atlantic City, and the Met-Life Tower in NY, and could very easily fly over the St. Louis Gateway Arch.
SPECIFICATIONS
Series Number: 5
Number of Stages: 2
Stock Length: 16.375"
Iris Payload Addition Length: 3.5"
Total Modified Length: 19.875"
Diameter: 0.736"
Fin Span: 4"
Upper Stage Weight: 16.9 grams
Booster Stage Weight: 4.95 grams
Empty Weight, Both Stages and Iris Payload: 25.9 grams
Liftoff Weight Range: 46.3 - 48.6 grams
Motor Diameter (both): 13 mmm
Motor Length (both): 45 mm
Motor Retention Method: Friction Fit
Payload Interior Length: 3.3"
Payload Interior Diameter: 0.71"
Payload Volume: 1.306 cubic inches
Recovery Method: 48" Mylar Streamer
Alternate Recovery Method: 10" Plastic Parachute
Typical Descent Rate (Streamer): 15 mph
Recovery Protection Method: Wadding
Shock Cord Mount: Kevlar
Shock Cord Elastic Length: 15"
Nosecone Material: Balsa Wood
Fin Material: Balsa Wood
Altimeter Capable: Yes
Number of Fins: 3 + 3 on booster
Launch Lug Size: 1/8"
Kit Brand: Estes
Completion: about 1976
FLIGHT LOGS
(Estimated about 6 flights on this rocket back in the 1970's)
2011, July 2: Indiantown Gap, Light wind
A10-0T booster, A3-4T sustainer: First test with an altimeter payload. Luckily, I caught an earlier mistake when I put the sustainer motor in backwards! Good staging, good flight, but due to a launch delay (lunch), battery died before flight. I now top-off the recharge between flights. Altitude is an estimated 700 feet, based on other flights.
2011, July 3: Indiantown Gap, Light wind
A10-0T booster, A3-4T sustainer: Beautiful flight, sailed out of sight for a long while. Good staging, perfect flight. I was amazed at the altitude reading for such a little 13mm rocket! It read 714 feet.
2011, August 7: Halifax, Light wind
A10-0T booster, 1/2A3-4T sustainer: Perfect flight and recovery. Apogee's 4' shiny red Mylar streamer is good for this model. Since I am usually busy tracking the small booster stage, I need an easy to spot rocket in the air or on the ground. The streamer doesn't drift very far with these high flights, so I can count on it landing nearby and not get lost. The altimeter recorded an apogee of 437 feet.
2012, May 6: Penn Manor, light wind
This photo below shows the beta just milliseconds before impact in the soft, wet ground, burying itself deep in the muddy soil, where the balsa nose cone soaked up a lot of water, swelled and distorted. It was buried so tight that it took a pair of pliers and a screwdriver/crowbar to remove it.
The payload bay was torn and split wide-open, only the padding kept the structure contained and the altimeter protected. The booster and 2nd stage appeared fine for the most part, however I cracked a booster fin trying to remove the engine casings. Post-flight inspection of the engines showed a normally burned booster, intact scotch tape holding the two motors together, and the engine orientation was correct and the motor mount tubes true and sound. The nozzle of the 2nd stage motor was sooted from the "ejection" of the first stage booster.
I concluded that it was just dumb luck that none or not enough of the burning propellant from the first stage made its way into the 2nd stage motor nozzle. Neither of the two motors was old, having just been purchased in the last year and stored in dry air at moderate temperatures in sealed plastic cases. Go figure.
What would happen if I put a little piece of that dark-brown ignitor squibb into the 2nd stage nozzle - would that catch more easily and flare up to start a more reliable ignition?
2012, June 30: Indiantown Gap, Erratic winds
A10-0T booster, 1/2A3-4T sustainer: After the last disaster flight of this rocket I repaired the payload tube and booster fin. I have come to expected many kinds of trouble with rocketry, but never expected the 2nd stage to not ignite. Even so, I’ve had three other successful 2-stage flights with another rocket last month.
So getting back on the horse, I was itching to get some numbers on this, but the winds limited me to a 1/2A powered sustainer. Since re-built, the new payload tube is ½ inch shorter, and the nose cone was re-finished. The old steel wire shock cord attachment was changed to a lighter Kevlar loop glued to the inside of the body tube. Overall I saved about 2 grams.
Staging went very well this time, total burn time was 1 second. Its flight path was quite straight. It reached a very high peak acceleration of 23 Gs or more, the overall average was 5.1 Gs, allowing this rocket to reach 112 mph. It coasted for 4.7 seconds before deployment at 425 feet, still going up. 3/10 seconds later it reached an apogee of 432 feet, three feet short of its record, but helped by the 7/10thsecond “bonus” delay. Although this delay isn’t quite long enough for the speed of the Beta, it was close enough, and there really is no other motor choice available in this size.
Below is a picture of the Beta flying on its second stage, after dropping the booster.
A good streamer let it fall at 15 mph and the flight was over in 24.9 seconds. The first stage landed at the launch pad, the second stage landed only about 120 feet away. The booster motor was about 1/3 out the rear of the rocket – almost was ejected. The recovery opening of the body tube, weakened from the previous wreck and reinforced with some paper, was partly ripped outwards by the Mylar streamer ejecting (lucky it didn’t get caught in there). Now the tube opening needs some serious re-construction to fly again.
I repaired the Beta by replacing the weak top of the tube with a longer and stronger tube, adding a couple of inches to the length. I also replaced again the shock cord mount, this time a small loop of Kevlar glued directly to the tube interior. The Beta Iris now stands almost 20 inches tall. She is now ready for some record setting two stage flights again, and I hope to see just how fast she can go.
2012, August 11: Halifax, 6-10mph winds, some gusting
A10-0T booster, A3-4T sustainer: This flight was to be a re-do flight so I could finally collect some meaningful numbers on the A3 as an upper stage. The rocket, previously destroyed by a failure to ignite the second stage, was rebuilt and ready to try the A3 sustainer motor again. Two A-size motors is the maximum that can fit into this tiny Estes "Mini-Brute" design.
The duration of the flight was only 7.5 seconds. It impacted the ground fairly close to spectators with the club and drove itself deep into the ground. The payload section tried to push itself into the main body tube, splitting and flaring it a bit. The altimeter compressed its lower padding and drove itself into the once slightly too small coupler used for the bulkhead. The nosecone drove itself three-quarters into the payload tube, splitting the tube open. Because the top rim of the payload tube was hardened with CA glue, the payload tube acted as a curved knife and shaved the finish and a thin layer of balsa off of the nosecone for three quarters of its length. That’s just what I saw as I pulled it from the ground. Disappointed, I didn’t bother to do a detailed inspection of the wreckage. Having just repaired this rocket, I was not excited to have to do it again.
Here we see the nosecone driven firmly into the body tube.
As it pressed into the body tube, the tube acted as a razor knife and peeled a thin layer of balsa and paint from the nosecone.
Fortunately, the energy of the impact was mostly absorbed by the nosecone, leaving the body tubes only slightly damaged.
Again I had no idea why the upper stage A3 didn’t light. I did verify that the two motors were oriented correctly and taped together well. It was then I realized that before the flight when I pulled the A3 motor out of the bin, I grabbed the one motor that had a bit of masking tape on it. At that moment I thought “This should save me some time, it’s got a bit of tape on it already!”
What I should have thought at that moment was “Oh, No! The tape on this motor must mean it is the A3 motor that didn’t light the last time and destroyed the rocket! That’s why the tape is on it already!”
That single moment that passed without much thought is what destroyed this classic old rocket from the 1970’s. ...That and a defective upper-stage motor given two chances to destroy a rocket.
The old, beaten-up launch lugs were severed and removed. The area under the lugs were then sanded to remove old glue and paint so new glue would adhere well.
Part of the motivation to do this was to add new lugs that would help reinforce a weak area of the body tube just above the fins.
New launch lugs were glued into place and being held in good alignment by a short length of 1/8" steel rod. I like this method because oozing wood glue does not adhere too well to steel so it is easy to remove.
The Beta Iris was repaired yet again and ready for flying. Both the main body tube and the payload tube were cut down a slight bit to remove the crushed areas. It lost about ¾ inches in length but gained a couple of tenths of a gram of mass. The paint was re-touched, but the scars still show.
2012, November 4: Penn Manor, 14mph winds, steady
A10-0T booster, A3-4T sustainer: This is the third attempt to get data on the A-to-A powered two stage
flight. The strong winds may have caused a launch abort, but I knew this rocket can accelerate quickly and
avoid the winds. Still, it was very windy and there was a degree of risk.
The launch was good and at about 200 feet the second stage lit (thank God, I wasn’t about to repair it a
fourth time!). Because of the strong wind, the staging was at about a 20 degree angle into the wind, which
certainly affected the altitude. The second stage continued upwind quickly at about 30 degrees from
vertical so that the apogee was probably about 200-300 feet upwind, across the road and into the upwind
field.
The maximum speed was measured at 124 mph, and the 1.1 second burn produced an average acceleration of 5.1 Gs, with a peak of 17.6 Gs (presumably from the first stage). It coasted for 5.2 seconds which was a long delay for the A3-4 sustainer, but that allowed it to continue climbing, with the ejection at 451 feet,
still climbing, it reached an apogee of 515 feet.
At the apogee the fully deployed Mylar streamer took over and then the Beta descended back to the ground at a soft, 13 mph. Finally I have some flight data for the 2-stage Beta Iris!
During the descent it drifted a lot, but that caused it to return to the launch area about 50 feet from the
launch pad. The booster was recovered about 50 feet downwind. Total flight time was 28.1 seconds.
This was a good flight, and although the shock cord and leader of the streamer twisted together it was not
enough to keep the streamer from unrolling and being effective.
Post flight inspection showed the payload tube was split along the spiral from the bulkhead and up about ½
inch. I’m not sure why it was damaged because it landed slowly and in grass. It will be an easy fix
though, and another scar on this battle-tested rocket.
2012, November 23: Penn Manor, very light wind
It was a beautiful clear morning with very little wind, but quite chilly. This was my chance to try again for 700+ feet, though I knew that was not likely in the colder, denser air.
She lit up and climbed towards the sky with a slight angle, with a peak acceleration of 17.3 Gs. Staging occurred without trouble. With the rocket 13 grams lighter and with less fin area, the second stage brought her to a speed of 132 mph, the fastest speed recorded for this rocket. Average acceleration was 5.6 Gs for the 1.1 second burn, also the highest recorded. I don’t know why the Altimeter 2 always records a 1.1 burn time when the two motors are spec’d at 0.8 and 0.6 seconds for a total of 1.4 seconds. I can only assume it doesn’t detect the fading thrust just before burnout.
The Beta Iris then descended at 13 mph, landing after a 39.7 second flight. This was the longest duration flight ever recorded for this rocket. It landed softly in the tall grass and got a bit wet from the heavy dew. It was a very successful flight.
A10-0T booster, A3-4T sustainer: I sent the Beta up on another flight to get three data points for the A10/A3 motor combination. The rocket lit and again recorded a burn time of 1.1 seconds. It appeared visibly slower on the first stage, as though it was struggling a bit from the weight. Still, it recorded a peak acceleration of 18.5 Gs which was the highest recorded, and averaged 5.2 Gs for the entire burn time. I do know from previous flights the booster only averages about 2 Gs, so the high average is a result of the 2nd stage.
This time the speed at burnout was 122 mph, ten less than previously. At 571 feet the ejection fired, and 2/10 seconds later the rocket reached its apogee of 594 feet. It was apparently going more vertical than the previous flight though, as it climbed an additional 23 feet in the 2/10 seconds. The ejection delay was quite long at 5.4 seconds.
Sometime shortly after ejection and too high to be seen, the swivel-clip holding the streamer to the Kevlar loop failed and opened up, so the rocket fell unseen with only the shock cord drag to slow it down. At 600 feet up, all of us observers only saw the bright red Mylar streamer descending much slower than expected. The streamer drifted into the next field never to be seen again.
Here we see the booster stage tumbling back to the launch area. This part was easy to find!
After a long and laborious 20 minute search, the rocket was located about 250 feet upwind in the grass sans streamer.
The only damage appeared to be a heavy dent in the leading edge of the fin, about the width of the body tube. It appears that the recoil of the extra-long shock cord slammed the payload tube against the fin, since there was nothing in the grass to cause this type of damage. So now this rocket is back in the repair shop for the fourth time, and will emerge some day with yet another scar.
The Beta Iris has been fixed up and touched-up and is ready for flights again. I will be flying this with the usual A10 booster, but only expect to use the 1/2A3 upper motor, so I have installed a small 10" parachute instead of the streamer. Altitudes should remain under 400 feet, so I don't have to worry about this rocket getting lost with the small parachute.
2013, March 10: Penn Manor, 5-15 mph winds, 63 degrees, 18%RH
A10-0T booster, 1/2A3-4T sustainer: This model got a new 7.5” parachute to replace the lost Mylar streamer and is now a few grams lighter. The booster motor lit well and the rocket accelerated quickly, at 20.4 Gs, and averaged 4.7 Gs for the total flight. Ignition of the second stage and booster separation usually occurs at about 50 feet, but this flight appeared to stage much higher. The booster then tumbled down about 150 feet away. After the second stage burnout, it coasted up for another 4.9 seconds after reaching a top speed of 108 mph, thanks to a long delay time. At 425 feet the ejection fired, stopping the rocket 1/10 seconds later and four feet higher. For this motor combination, this was the lowest and slowest flight I’ve recorded.The new parachute opened well and the model descended safely at 6 mph, landing far downwind about 500 feet. Both the other observer and I lost sight of it, and it was only spotted on the ground thanks to the bright orange plastic I used for the parachute. This was a very successful flight which lasted for 49.5 seconds – an all-time record duration for this model. It did suffer another nasty recoil "bite" in the leading edge of one of the fins.
2013, July 14: Penn Manor, 3 mph winds, 84 degrees, 63%RH
A10-0T booster, 1/2A3-4T sustainer: A great morning for flying, though it was quite warm and humid. This was the final test flight of the Beta Iris with a 1/2A
sustainer. The booster lit without delay and the rocket took off quickly and straight up.
Staging went well and appeared to be at about 200 feet.
The sustainer continued straight up, with a peak acceleration of 19.8 Gs, while the average for the flight was 4.7 Gs. The rocket reached a top speed of 106 mph, the slowest for this rocket.
Ejection occurred only 1/10 second early at 426 feet, but the rocket continued up an additional 14 feet in the next 7/10 seconds to apogee at 440 feet. This was the highest recorded altitude with a 1/2 A sustainer.
The little 8” chute opened well and the rocket returned at 8 mph to a soft, grass
landing one or two hundred feet downwind. The booster had already fallen, and the
booster’s casing blew out of the lower stage. Overall it was an excellent flight.
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