Interceptor Iris

The Interceptor: This rocket kit is the new release of the Estes Interceptor. It flies on 18mm B and C motors. I edited the above picture to simulate this flying over the Pacific Ocean in outer space.

This kit was modified with an ejection-gas baffle and Kevlar shock cord mount, and an Iris Altimeter Payload Section.

Here is a different angle view. After 6 months, it's finally ready. Construction went well, but painting using bargain-price Home Depot paint resulted in "orange peel" finish, which had to be sanded off - TWICE, and re-applied.

The paint then reacted with the primer (SAME BRAND!!) and crinkled and cracked the finish.

Re-sanded again and then used the expensive but acceptable Testors paint for $5 per 3 oz can. Clear-coat, decals, then 3 more clear-coats and finally it's done.

With the generous glue, extra paint and the added electronics bay, she weighs in at 164.5 grams (5.6 oz.) and is 3.2" longer than stock.

I'll plan to use the shorter ejection motors than recommended, just in case it's a little too heavy.

Typically for me, this model only passed a string-stability test after I added 17 grams of nose-weight on the base of the nosecone. (Am I doing them wrong??) We'll see how well she flies, but she sure is a pretty gal!

We DID see how she flies, and it wasn't pretty. This model is grossly overweight.

The baffle (10 grams?), payload section (19 grams), and the heavy nose-weight (17 grams) makes this too much for even a C6-3 motor.

I'm going to send this up on a D10 just to see how well she can fly. Then I'm going to have to take out that nose-weight and see if it's stable enough for flight, I expect it to fly better that way.

If it does not and it is destroyed, at least I'll have that one good D-flight to remember.

I won't want to fly this on a regular basis using the $10 apogee motors though, so instead I hatched a plan to add two small A10-3T boosters on the back, for a total impulse with a C6 motor of 26.

The parts for the "solid-rocket-boosters" were obtained from two Estes 220 Swift rockets.

I'm waiting to see how well it will fly without the nose-weight before proceeding with this plan.

It would be my first cluster rocket project.

SPECIFICATIONS

Series Number: 21
Number of Stages: 1
Stock Length: 26"
Payload Addition Length: 3.188"
Tip-to-Tail Length: 29.188"
Diameter: 1.325"
Wing Span: 7.5"
Rudder Height: 3.375"
Basic Empty Weight: 146.7 grams
Payload Section Addition Weight: 12.1 grams
Swift Booster Addition Weight:  7.7 grams
Liftoff Weight Range: 175.8 - 182.8 grams
Motor Diameter: 18mm, 2X 13mm
Motor Length: 70mm, 2x45mm
Motor Mount Method: Clip, 2X friction fit
Payload Interior Length: 2.4"
Payload Interior Diameter: 1.28"
Payload Volume: 3.08 cubic inches
Altimeter Capable: Yes
Recovery: 18" Nylon parachute
Typical Descent Speed: 9.5 mph
Recovery Protection Method: Baffle & Wadding
Shock Cord Mount: Kevlar
Noseweight: Washers & Screw, 8.3 grams
Fin Material: Balsa Wood
Unusual Features: 2X Swift 13mm booster pods, Wingtip Pods, Rudder Antennas, Ventral Strakes, Molded Tailcone
Launch Lug Size: 1/8"
Paint: Testors Model Paint
Kit Brand: Estes
Completed: Nov 5, 2011

FLIGHT LOG

2011, November 6: Penn Manor, Breezy wind

C6-3: I was (emphasis on past-tense) proud of this rocket when I brought it out to the flight line. It was lookin' sharp! It took off kind of slow, weather-cocked a lot in the strong breeze to 90 degrees or so, and seemed to have a late delay.

It was a long 3 seconds at maybe 200 feet. It appeared to come down OK and was not damaged at all, except that I found ALL 6 shroud lines ripped from the parachute plastic. Need to go nylon on this model.

Shortly thereafter, Scott B.'s Interceptor flew well in the wind on the same C6-3 motor. On top of all that, the altimeter data came out totally in error. It read 6 feet, 39mph, said it only burned for 1 second (a C6 burns for 1.86 seconds). It did say the peak acceleration was 3.2 G's and averaged only 1.7 Gs - that may have been correct. The rest of the data was missing, but I do know the whole mess was over in 10 seconds.

This was the first of 4 out of 7 flights with bad altimeter data; I suspect the thing was pre-triggered in the breeze while sitting on the launch pad.
UPDATE: After corresponding with Jolly Logic (maker of Altimeter 2), it turns out that the model '2 is not triggered by pressure like the '1 is. It senses acceleration - and I'm sure I knocked the rocket around some and triggered it before launch - that explains the bad data I've been getting. Stay tuned for some valid data on upcoming flights!

2012, May 26: Indiantown Gap, 5 mph wind

D10-7:  Because of the extremely overweight condition of this model, the first-ever flight was quite disappointing. I expected to make good this time and prove this model could fly well by using a very powerful Apogee D10-5 composite motor.

Since I knew I built it very well I expected this model could handle the extremely powerful ejection charge of the Apogee motor. My launch sheet showed that I expected it might fly to over 700 feet – purely a guess.
This composite motor lit well and quickly with a copperhead ignitor.  Very quickly a six-inch long orange stream of fire lifted this model off the pad with a loud roar and an acceleration of 8Gs.  The motor burned for 1.3 seconds with a steadily declining thrust, reducing the average acceleration down to 4.7 Gs.  As the motor pushed all 198 grams (7 oz.) straight up into the air it reached a speed of 135 mph before coasting for the next 5.7 seconds.

The ejection charge was a bit late – luckily – as the rocket was still ascending. The parachute ejected at 684 feet, stopping the rocket at an apogee of 689 feet in the next 2/10ths of a second.  The parachute opened cleanly and the rocket then descended at 9 mph. The flight was over after 57.5 seconds when it landed far across the road into the next field in very tall grass where it was recovered without a scratch.

No scratches, but there was a three or four inch hole in the nylon parachute, burned clean open from the powerful ejection, even though it was through a baffle and a thin layer of wadding to keep soot off of the nylon.

So I proved this model can fly well, next I intend to remove some of the 17 grams of nose weight and see if it will do any better with a C6-3 motor in very light winds.

2012, June 10: Halifax, near calm

C6-3: I lightened this model by about 15 grams by taking out the nylon parachute andusing a lightweight plastic parachute, saving 6 grams, and by removing about 9 grams of nose weight. It was a very calm afternoon so I wanted to see if this model can fly economically with a C6 motor and remain stable with less nose weight.

Peak acceleration was 4.6Gs, good enough to get it off the launch rail cleanly and going up. The motor burned for 2.1 seconds and averaged 1.2 Gs for the burn.  Top speed was only 52 mph. It did turn into the wind about 30 degrees or more.

Again the ejection delay was too short – only 2.7 seconds – and the parachute started to deploy at only 147 feet. 7/10 seconds later, after climbing an additional 15 feet it reached its apogee of 158 feet.  The parachute deployed well and the rocket came back at 10 mph for a soft touchdown after a 13.6 second flight. Because of the curving trajectory it landed far, about 250 feet from the launch pad.

I am not so impressed with the Interceptor’s performance on the C6-3,I don’t believe removing the extra 8.3 grams of nose weight will give me much better performance.  Instead I am going to move ahead with my plans to attach two 13mm A10 boosters to this rocket for a 3-engine cluster, sort of like a JATO assist.  That will certainly make this model something unique!

Above we see the replacement parachute, a much lighter plastic material was used to replace the burned-up Nylon parachute.

Before adding JATO though, I’m going to fly it again with the last powerful D10-5 motor I have, and one more time with a C6 motor without any nose weight at all.  If I can’t get 200 feet out of this bird, JATO it is.

2013, June 30: Fort Indiantown Gap, light winds.

D10-5:  I wanted one more high performance flight for the Interceptor.  This was my 200th flight as a BAR, so I loaded it with the Apogee (Aerotech) D10-5 composite propellant motor. With less nose weight, I expected even better speed and altitude performance, and I got it.

I had to remove the label to get the motor to fit.  Again the copperhead igniter worked well, and the motor lit up with a roar.  This time it accelerated off the pad with 9 Gs of acceleration, and averaged 5.2 Gs for the 1.3 second burn.  This was record high acceleration for the Interceptor, and it also hit a record speed of 149 mph, travelling straight up.  It then coasted in a gentle arc for the 6.4 seconds to reach an apogee of 761 feet, also a record.

Often the Altimeter 2 does not detect ejection for unknown reasons, and again this time it did not, but it appeared to eject close to apogee, though a little lower at 747 feet. I don’t know if that was before or after apogee.  The parachute popped, opened up, and the rocket descended at 8mph for a total flight duration of 1 minute and 6.6 seconds, a record duration for this model, and a record-low descent speed.

Those binder reinforcement rings are just not strong enough!

This was an Estes kit. I use Vinyl (Electrical) Tape.

Outwardly the flight appeared to be good, but there were problems, a bunch of them actually. One of the thin shroud strings ripped thru the light translucent Estes plastic and the reinforcement ring, making the canopy lopsided. A second shroud line was caught and wrapped around the shock cord’s knot. There was no evidence of burning on the parachute.  The combined asymmetry caused rapid rotation of the parachute, and the shock cord (with no swivel) was very severely twisted in knots by the time it hit earth again.

How in the h@!! does this happen? What really goes on up there?

There was still enough parachute to protect the rocket, since it fell at only 8 mph.  It landed softly in the grass.  Post-flight inspection revealed the upper body tube was crushed in the last ¼ inch or so.  It seems to have been caused by the shock cord recoil, since it landed softly on the rear of the rocket.

Another body tube bites the dust. It seems no amount of shock cord length can prevent this!

The hollow cardboard bulkhead is 2 inches in length, one inch covered by the payload tube, and one inch covered by the body tube. After landing, only about ¼ to ½ inch was exposed, the rest of the bulkhead having been pushed into the payload.I don’t understand how that could have happened except for an extremely powerful ejection that forced it upwards into the payload tube. Perhaps it was pushed in when the shock cord snapped back and the bulkhead struck the tube opening.

More evidence of the powerful ejection was on the Altimeter Two.  The circuit board assembly, including the display and control button, was forced down into the plastic case, or the case was forced up past the circuit board.  I’ve seen this before on a hard landing, but never from an ejection.

Notice the button is now offset from the case.

Also notice the circuit board is extended beyond the supporting plastic behind it.

That must have been some strong ejection force.

Note also that although it took a lickin', it is still tickin'.

I have seen these Apogee motors seem to have very intense ejections, so this seems to be expected damage. Even though it has an ejection baffle, I learned to use wadding anyways.  While the D10 composite motors are impressive and fun, they are expensive and seem to cause too much ejection problems for these smaller rockets.  I could get more power from either a black powder E, or a cluster of Cs which are certainly cheaper.  I will not fly this rocket on the D10’s anymore to prevent more damage. Instead, I will go ahead with my plans to add two small “JATO” booster rockets made from a pair of A10-3T motors.  Before I do that though, I want to fly one or two more experimental flights but this time removing all the 8 grams of nose weight, and see if the regular C6-3 can fly this well enough.

So my 200th flight appeared to be jinxed. I scrubbed the mission two months ago because flight #199 ended with my Big Bertha in a tree 60 feet up. The next month was cancelled because of high winds (20 gusting to 35).  This flight went off today, but there were just so many things going wrong for it that it was lucky I got it back at all!


2013, August 31: Fort Indiantown Gap, 5 mph winds, 86 degrees.

C6-3: I have removed all noseweights from this model, making it over 8 grams lighter. Now I'll see if it can fly well with a C6, though previous flights with noseweights were very disappointing. I am also using a lightweight 19 inch parachute.

The motor started burning, accelerating this model at 5.2 Gs off the rod. That was the best so far. As the motor burned for 1.9 seconds, it averaged 1.2 Gs, as normal. This time it reached 49 mph (slightly less), but it continued its vertical ascent.

Take a close look. At first, it may appear that the whole rocket exploded,

but it is just ejecting the "dog barf" or fire-resistant wood pulp (made for home insulation).

Here I used it to protect the parachute from the hot ejection gasses.

Since the rocket is still travelling forward at a high velocity,

it quickly flies through the cloud of wood pulp.

Here you can see the nose cone and payload section out in front.

The nose cone is pulling the packed parachute out with it.

 Now that the parachute is free and taking on the air flow, it begins to open up.

After coasting for 2.3 seconds it hit 155 feet when the ejection fired. It still continued up another 25 feet to reach an apogee of 180 feet - a new record for C6 power! It was unfortunate that the delay was terribly short.

The big 19 inch 'chute opened up and the rocket returned at 6 mph for a soft grass landing...right by my tailgate! The extra long shock cord was wrapped around the wing pod, so the body came down sideways. I didn't even have to carry it back to prep it for another flight!  Very successful test flight.

It might look like it landed on the car roof, but the long lens is playing a trick on your eye. It landed safely between the ample space between my tailgate (upper right corner) and the car behind it!

C6-3: I wanted to test fly this again, just to prove the last successful flight was not a fluke. Again it had the noseweight removed (only added to pass a string-stability test).

After a good ignition, the Interceptor Iris left the pad accelerating at 4.9Gs. It burned for 2 seconds, averaging 1.2 Gs of boost. It reached a top speed of 53 mph (record for a C6 motor), and coasted upwards for another 2.3 seconds. This time it took a turn for about 20 degrees, then 30 or so, but continued up.

The ejection fired at a quick 2.3 seconds while at 163 feet, stopping the climb 1/10 second later at 168 feet, a very respectable altitude for such a heavy, draggy rocket. It then descended at a slightly faster 7 mph to land about 80 feet downwind, after a flight time of 18.1 seconds.

Unfortunately this time it missed the several acres of soft grass and found a spot of hard dirt, heavily cracking one of the wing pods on bounced landing. It can be fixed, but will never look as pretty. The performance is acceptable with a C6 motor, but not too impressive.

Since this is going into the shop, I will install the twin 13mm A10 booster motors on this ship, to give it impressive takeoff performance. This will be my first parallel cluster motor rocket.

Here is a sneak peek at a booster pod being constructed. I call them Swift boosters, because I basically stole the parts from a pair of Estes Swift rockets.

 Now I have the two boosters primed and after a good sanding, they should be ready for white paint. I'm finishing them now because it would be very difficult to do that with them attached to the Interceptor which is already finished and decal-ed.

Meanwhile, I am repairing the flight damage to the main rocket. Both of the wing pods suffered some

cracking damage from a hard landing on the rocks.  I put as much plastic cement in the pods as I could and held them together with rubber bands.  Apparently, my original gluing using three kinds of glue was so good that the weak point was the plastic pods themselves. I imagine this isn't the last time I'll be gluing them.

The Swift booster pods are ready for attachment to the main rocket body. To do this I have to perform some surgery on the main body tube to attach them to the motor mount area. I reluctantly have to cut some holes in a perfectly good rocket.

...time passes...

Three years later, and the Interceptor Iris is out of the shop and ready for flying again.  It is now named the Interceptor Swift Iris, a long name for sure.  I've already documented the construction of the Swift boosters, but let me go into a bit more detail.  I've photographed the hell out of this while doing it.

Below we see the important parts of the change. This shows one booster, but of course there will be two of them, one on each side, so that there will be a balanced thrust for flying.  The motor nozzles will be as close to center as possible in case one doesn't light, but that is a known risk with clustered rockets.  I'm hoping I will not see a misfire, but if so, I am hoping the thrust from the center C motor will reduce the effect of an off center thrust.

I'm hoping the rudders and strakes underneath is enough to counter the effect of a misfired booster.  I would have placed the boosters top & bottom, so the larger wing surface would act as a more capable rudder, but the launch lugs were on the bottom and I didn't want to move them.  Also - quite frankly - it would look a bit odd, even though it's the smart thing to do aerodynamically.  So side boosters were decided, and I'll take the calculated risk.

There is a tiny little BT-5 tube (13mm inside diameter) and a matching nose cone taken from the Swift.  To this I added a 13mm plywood disk and a wood stick to act as the thrust bearing member.  I don't know what wood type the stick it is but it is much harder than balsa.  Poplar maybe?

Note that the nose cone's inside flange is notched to the shape of the wood stick.  That is to fit the stick in it as shown below.  The front-back dimension of the stick is about 3/8", so that in the direction of the motor thrust it is very stiff.  The thrust of the booster motors will press on this stick and the stick will be attached to the Interceptor.  The nose cone was glued first with hot glue. It may not be very strong but it will not need to bear the load of the thrust from the motor. I had to align them as well as I could by eye, since a misalignment here would cause the whole motor tube to appear misaligned.  The sticks were intentionally made much longer so that I would have an easy way to hold and clamp them.  They will be cut to size after finishing and before attaching to the Interceptor.

After gluing the two thrust sticks to the nose cones, I wood glued the 13 mm wood disks to the back face of these assemblies.  The picture below shows one glued and one about to be glued.  The purpose of the disk is to act as the motor block that the booster motors press against, and also to take the brunt of the ejection and cause the smaller booster motors to eject out the rear.

When those were dry, I attached the two motor tubes.  The tubes were also notched out so the stick would protrude through.  The 13mm motors will stick out the back a bit, but that was on purpose so that the heat of the exhaust will not be impinging on the plastic tail cone of the rocket.

 All glued, I waited again for it to dry.  Then I applied a coat of primer as shown below and another...followed by white paint. Glad I made the sticks long enough to hold these while finishing.

Now the two booster pods are ready for installation.  Next comes the scary part, which is possibly why it took me three years to complete this.  (I spent a lot of effort trying to make this a really well-made kit, so cutting a hole in the sides and ruining the decals was not something I naturally wanted to do. I had to convince myself that it will fly much better with this change, which of course motivates me to do this, this isn't a hangar queen or a shelf decoration, but a workin' man's flying rocket.)

I measured once, twice, may be three times, then cut the holes in the sides using a new, sharp X-acto blade.  No going back now. If you want an omlet, you got to break some eggs.  The plan is to insert the thrust sticks in to make contact with the motor tube.  I can only hope I got enough glue in there because I couldn't see it.  All the glue might just run around in there and make excess weight without doing its job.

 Now I had to measure again and cut the sticks to length, feeling for just the right point where it contacts the motor tube. I sanded and test-fit these pieces until it felt just right, then made the cuts with a X-acto saw blade.

 Below we see a test fit of the two boosters.  Looks workable, but the pix clearly shows that the shade of white paint isn't a good match.  Testor's on the original, Rustoleum on the boosters. Oops, my bad.

 Here's a look at the two boosters from the sides. My next challenge is to get these aligned and keep them there while being glued into place.

Before the gluing can be done, I need to remove the paint.  Now I think I know why this rocket flew so poorly, weight.  There was a lot of primer and paint to get through.  I sanded out the glue area from the two booster pods.

 And sanded down to bare cardboard the glue areas in the rear of the rocket.  Worst case, if the wood sticks don't hold very tight, at least the body tubes will remain attached to the rocket.

 That was the left side.

And this is the right side.

When I thought about it, if the motors were mounted with a bit of twist (aimed a bit in opposite directions) then when boosted the rocket will probably spin rapidly.  I'd rather have them misaligned in the same direction.

I made a jig that I hope would keep all three motors aligned.  I supported the rocket vertically, and glued two 13mm spent motors to a piece of plywood.  These were inserted into the boosters (which were not glued yet) to get the spacing just right, and then I tweaked the alignment before the glue dried.  After dried and verified with a caliper, I could use the jig to make sure that both boosters were at least pointing in the right direction.  If they were canted a bit inwards or outwards, that would be acceptable, but I didn't them canted in different directions.

Above we see the gluing done to the jig with the rocket supported vertically and verified with a carpenters angle.  This was mostly to get the motor spacing right for the jig.  Before it dried completely, the rocket was removed and the spent motor casings aligned by hand.

Now comes the actual gluing!  The first one was glued and held tight with rubber bands.  A casing was inserted to prevent the rubber bands from crushing the tube.  I aligned this first booster by hand and used a steel rule to eyeball it to be in the same direction of the fins.  I applied glue liberally, and had to clean up the ensuing mess with paper towels.

The next day, with the first pod dry, I glued the second one in pretty much the same way.  But before it had a chance to set, I inserted the jig into each pod so the second pod (on the top) was aligned with the first one glued the day before. Both appeared to point in the same direction when eyeballed with a steel rule flat to the fin/wings.

I can only hope the alignment, and the glue is good enough.
The next day I removed the jig and started applying glue fillets.

I cover up the ugly with a paint brush and some Testor's paint.

 Here's a view from the front. Since the wings have a negative dihedral and angle down a bit on this kit, the pod noses are noticeably higher on the fuselage.  Compared with the rest of the rocket's design, these look a bit too plain.

 Here is a more head on view.

 And here is the tail view.

 To help with the plain-ness of the Swift boosters, I added some decals that seem to fit the style.  These extra decals actually came from a Quest Tomahawk SLCM kit.  They were just the right size and just the right color!

 If it weren't for the white mis-match, I'd think this was part of the design.

Here's the view of the other side.

If this thing actually flies well, I may just re-visit the decals and add some more, but maybe this is enough.

And the parting shots show the completed upgrade to a cluster rocket. This then, is the...

Interceptor Swift Iris.

This rocket now tips the scales at 146.7 grams (including the added Iris payload section, but no motor, altimeter or parachute.)   I expected this upgrade to add a lot more but glad it didn't.

Next decent flying weekend, she's going up!

2018, October 7: Penn Manor West Field, 5 mph winds, 85 degrees.


C6-3 & 2x A10-3T: I finally got out to fly after two years and a month! I wasn’t sure at first whether I’d remember all the little things I do to make a successful flight, so I hesitated and just practiced my photography on others rockets. Eventually I found the courage to try this flight.


My inspiration came from my remembering my Interceptor Swift Iris experiment – my first attempt at a cluster flight using two additional A10 motors with a C6 motor. Necessary because of the 147.5 grams this beast weighs. (over 5 oz., not including the motor weights.)  It’s been five years and more since this rocket took to the air because it has been in the shop for damage repair and a major addition of the solid rocket boosters.


















Lesson one I learned is that it is difficult to get three sets of clips on the ignitors without creating a short. Somehow I prevailed.  The button was pushed, and all three motors fired off simultaneously, though I had no way of knowing it at the time.

The Interceptor Swift Iris leaped off the pad with a peak acceleration of 9.9 Gs, the highest of any motor choice for this bird, including a composite D10 motor. It launched almost perfectly straight up, and a second later the two A10 boosters gave out and started releasing their tracking smoke.  After another second the main C6 motor also ceased thrusting. Burn time was recorded as 1.9 seconds. This combined for an average thrust of 1.8 Gs,   Shortly after that the first and then the second A10 ejected as planned, hopefully adding a bit more thrust to the rocket.

The aircraft reached a top speed of 78 mph. That was much better than any single C6 did, but not nearly as fast as a single D10 flight.  The coast to apogee was 3.4 seconds, where it reached an altitude of 352 feet. That was about double what a single C6 could do, and the straight trajectory made for a much better flight with very little affect from the winds (which were fairly light though).  I predicted 330 feet for this flight, based mostly on a gut feel since I have no data to draw upon for a cluster flight.  As it was, I was only off by 22 feet!

First puff with the ejection of the first A10 booster motor, which can be seen upon close examination.

For reasons I can’t explain, the C6 fired its ejection charge very early, with an actual delay of only 1.7 seconds…3.3 seconds less than expected.  Because of that, the ejection was recorded at 293 feet, so it had excess drag for the last 59 feet of its ascent. Could it have passed 400 feet with a good delay?

Second puff from the second motor casing, a fraction of a second later.

Still it was successful, and the heavy duty 19 inch Nylon parachute took the punishment, opened clean, and allowed the rocket to descend at a comfortable 7 mph.  After a 31.8 second flight, it touched down without damage in the soft grass about 250 feet downwind.  Only upon recovery did I get confirmation that all three motors lit.  I had completed my first cluster motor flight, with complete success.  I hope to have a few more.

Another happy ending.

2018, Nov 4: Penn Manor Field, 7 mph winds, 57 degrees F




C6-5, 2X(A10-3T):  This flight was both my second flight with the Swift Boosters, and my second cluster flight ever.  It didn’t start well, but flew well, but in the end it was not well.




While loading the swift A10 motors, I first noticed that the one motor slid in loose, but tight on the other booster.  What I discovered is a spiral split up a portion of the body tube.  Obviously the ejection from the first flight over pressurized the booster tube and split it open.  I didn’t notice at the time.  Oh well, I made sure to tape it higher up on the motor so the casing fit tight in the tube.  Maybe that was a mistake in hindsight.  Maybe I should have just scrubbed the flight.

The Interceptor Swift Iris is poised for a flight test mission.  The C6 motor and the two A10 boosters are loaded and connected to their igniters.  The data collection altimeter is armed.

But I didn’t.  I loaded it up, and again found it a hassle to connect all the wires. Again I had all three motors firing.  The interceptor flew off with an acceleration of 9.7 Gs, slightly less than last time.
The burn time was 2.1 seconds, slightly more than last time. (And curiously the longest burn ever for this rocket with any flight.) That gave me a lower average acceleration of only 1.5 Gs, and pushed it to a top speed of 71 mph, also slower than last time.

The Interceptor lifts off into a clear blue sky for its second test flight with all three motors burning.

I had an identical 3.4 second coast time, and again the altimeter sensed an ejection time much quicker than expected for the C6-5 motor. Reading 1.8 seconds, I think it might be detecting the swift booster’s ejections.  However it measured it, it still gained 41 feet after ejection at 319 feet, to come to a peak of 360 feet. 360 feet was better than last time and certainly satisfactory! Still the apogee-to-ejection time measured -1.6 seconds, so I’ll have to think some of what actually happened. The video may help me sort it out.

The telltale puffs of smoke show the rapid succession of booster separation at the end of the delay times.  The larger C6 motor is still pouring out tracking smoke before the main ejection deploys the parachute.

I got a good parachute, and a descent at 9 mph to land in somewhat muddy soil about 100 feet downwind.  Flight time was a satisfactory 26.8 seconds.

A view shortly after the parachute fills with air after ejection at 319 feet.

In the end it was not a good flight, because I discovered although all motors burned, now both booster tubes are split heavily!  Not only does it look ugly, it can’t fly with boosters until I get that fixed, and that looks like a very difficult project.  I figured out in the first millisecond after seeing the split that I should have added vent holes to prevent over pressurization.  Rocketry is nothing if not a learning process.

This sequence taken during the ejection at about 5 frames per second show the details of the deployment that usually can't be seen. In the first image, with the rocket body traveling at a fast speed, the parachute just begins to fill with air and slow down, allowing the interceptor to pass by the parachute and payload/nose cone.  Also visible is a length of recovery wadding hung on the wing. In the second frame, the shock cord pulls the body of the rocket 180 degrees around as it begins to slow the craft.  The wadding breaks free.  In the third frame, the rubber shock cord is stretched to its maximum, and the strip of wadding momentarily hangs on the cord as it begins to recoil (seen in the fourth frame). In the fifth frame, the shock cord has retracted and set the wadding free again.  All the while extra smoke from ejection pours out of the body from both ends.  In the last frame, taken a full second later, the body has now settled down, the wadding drifted away, and the rocket dangles beneath the parachute as it all returns at 9 mph.

Left pod damage

Above and below, we see the damage with both booster pods being split at the spiral seams.  I haven't yet figured out how I am going to fix this, but I don't believe it will be an easy repair job.  Those pods are glued and filleted very well, and attached to the nosecone, a plywood thrust pad, and a hardwood stick that goes thru the main body into the motor mount.  The idea was for them *not* to come off easily.

Right pod damage

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