KosRox Apollo Pad Abort Test Capsule

KosRox - Apollo Pad Abort Test Capsule {Plan}

Contributed by David Fergus

Manufacturer: KosRox
Rating
(Contributed - by Dave Fergus)

Rocket PicBrief:
This model rocket is a 1/26.5 scale rocket of the Apollo pad-abort test rocket. It was used to test the Launch Escape System(LES). The LES consisted of a four- nozzle rocket motor set atop a supporting tower with a dummy Apollo capsule. It was designed to lift the capsule away from an exploding Saturn 5 booster. The kit model has a 5.8" base diameter, is 18" tall, has an 18mm motor tube, and uses streamer recovery. It weighs 2.8oz. without an engine, and 3.4oz with a B4-2. It is available for $15 plus shipping from KosRox.

Construction:
The quality of this kit is outstanding! All parts were of high quality, precision cut, and easily identified from the parts list and pictures. The packaging was a heavy plastic bag. All parts were present and none were broken. There were nine paper shrouds precision cut to the correct inner and outer diameter, with markings as appropriate. The nozzle shrouds even had the correct curves for installing at the correct angle after curling and gluing. The tower kit came in a separate little plastic bag that included all of the laser cut struts. The nose cones are balsa, and the bulkheads are cardboard. The launch lug is heavy duty, which is necessary due to the kit design.

Note from KosRox: KosRox does not supply decals. Tago Papa or Jimz are better sources.

The instructions are on 11 sheets with a picture accompanying all 39 assembly steps. The instructions were logical, well written, and included good tips for easier construction, such as clamping shroud seams with spare balsa strips and clothespins while the glue sets. The pictures that accompanied every step were clear, and were very helpful in clarifying the written guidance. The kit maker included "heads-up" where he anticipated possible errors by the modeler.

I puzzled over the instruction to spray mat sealer on the inside of the printed capsule shroud. I did not know what to use, and finally guessed on Krylon clear sealer (my decal sealer of choice). A caution here would be to not touch the shroud while it is drying, which I did and smudged the black printing on the capsule. The pattern is printed on an ink-jet printer and easily smudges. Step 21 has the " V" struts glued with a 1/4" inset. Shade this to the high side, or the circular structure ring will not meet tips of the "V"'s.

Rocket PicStep 33 on the shockcord attachment is confusing and needs better instruction. The intent of putting a loop in the Kevlar® shock cord is to use the motor tube as the anchor the shock cord pulls against. Only after the motor tube is inserted through the top bulkhead, the loop in the shockcord, and then the bottom bulkhead; should the shockcord be pulled taut through the small hole in the bulkhead, and glued. Because I did this out of order, my shockcord loops around the motor tube, but has useless slack inside the bulkhead. All of the shockcord strain is felt by the upper bulkhead on my model.

Finishing:
For finishing, Elmer's F&F filled in the grooves on the BT-50 tower tube, smoothed the capsule and tower nose cones, and the shroud folds. The roll pattern was done by using black electrician's tape. It makes a lot straighter lines than trying to mask and paint. I rate this a 4.5 for construction due to the few minor nits mentioned above.

Construction Rating: 4 out of 5

Flight/Recovery:
Care must be taken when packing the crepe streamer so that it will deploy upon ejection. When asked about prototyping the recovery system to include 3 tiny chutes, the kit designer leaned against it. He had tried a chute and they did not deploy consistently due to inward slope of the body cavity. On one of his early designs with only one shroud instead of two, the model was light enough for tumble recovery, but durability demanded double shrouds which leads to streamer or chute for the added weight.

Because of the large 'cone' area of this rocket, it does not build up a very large velocity. At motor burnout, it decelerates very rapidly. The kit recommends a B6-4 for first flight, but I would use a B4-2, especially if you use several coats of white paint on the tower assembly.

Rocket PicRocket Pic

Another big caution is to make sure the launch rod is clean as a whistle, and maybe even lubricated with baby powder. This rocket could stick on the rod due to the large moment arm between the motor and the top tip of the launch lug. The launch lug needs to be long to go through the whole body of the capsule, but also has to be offset from the motor tube to clear the tower assembly.

The motor is retained by tape friction rather than a hook, which would detract from the appearance. I rate this a 4.0 due to the inherent design difficulties of launch and recovery.

Flight Rating: 4 out of 5

Summary:
Overall: I rate this kit a 4.5 due to the uniqueness of the prototype, care in the design and appearance, value for the $15 price, durability, and the new skills it taught me.

Overall Rating: 4 out of 5

Q&A with Damian Kostron of KosRox:

1. How did you paint the roll pattern on the upper body tube?
The roll pattern on my model ended up being black electrical tape. I painted the jet rocket and applied a couple strips of black tape. Yeah, that is cheating, but it works.

2. I really puzzled over what you meant by mat sealer. I ended up using some Krylon clear (the same thing I use to seal and cover decals), and it worked for it's intended purpose to keep the epoxy from leaching through to mar the finish of the printed shroud; and except for touching it while wet, would have been perfect.
'mat sealer' - any clear spray paint type of product that will provide protection from moisture.

3. I was intrigued by your photos of some sort of glue applicator out of my experience. I used Elmers Carpenters Wood Glue for external use, unless you specifically called out for CA or epoxy. It has the property of not running and a small amount holds parts together while you orient them, and is sandable. The downside is that it shrinks. I used it to anchor the wood dowels to the strut parts, and then backed it up with CA.
The applicator is a nifty oiling bottle originally used for applying small amounts of oil in tight areas. The 'needle' of the bottle is very large (in comparison to a hypodermic needle) and allows me to use Elmers wood glue (construction glue) in it. Although, frequent cleanings are necessary.

4. I messed up and touched the large shroud while it was still damp from the sealer that I sprayed on the inside. I have a few smudges of the black print into the white areas. Any suggestions as to how to touch up?
Smudges...bummer. I used an Ink-Jet printer for the printed shrouds. The ink is water soluble (I expect that there are a few other things that will dissolve the ink as well). A clear over coat (like the 'mat sealer' or your Krylon clear coat) is to protect the shroud from smudging. The only thing I could think of to fix yours it to use a little white touch up paint on the smudge itself.

5. One other item of feedback is the shock cord attachment to the main capsule. I did not do it quite right, upon reflection, in that after the engine tube was affixed would have been the time to pull the cord and loop tight and then glue where it goes through the bulkhead hole. I am afraid that my loop is still loose and the anchor is the bulkhead itself. Your description of how to do this was a little bit of a puzzle. Should I reinforce the bulkhead somehow with cross bracing?
The shock cord is supposed to loop around the main engine tube. It will be impossible to do this, once this tube is glued in place. Yes, it does provide for an interesting puzzle during construction (and a little dexterity). This 'loop around the engine tube' is to provide strength to the shock cord. If your shock cord has a knot that does not allow it to pull through the upper bulk-head (but does not loop around the engine tube). I would suggest a reinforcement consisting of a penny sized piece of card stock with a small hole in it's center (just big enough for the shock cord). Then epoxyed into place (effectively reinforcing the main bulk-head, keeping your knot from pulling through).

6. I am nervous about the strength of the upper shroud. Have you had shock cord damage of that shroud? Is there a way to reinforce the inside of that shroud? Any other hints on avoiding damage during recovery other than lubricating the launch rod? I am nervous about the shockcord/streamer arrangement. The upper portion seems awfully close to the main capsule... I am inclined to bring them down in two pieces with two small chutes. A chute on the main capsule would be closer to the prototype, wouldn't it?
This is a complicated series of question(s), with many possible answers. Let me start by telling you about my 'boiler plate' models. I built three of them. One was built with single layer shrouds (both on the nose section and the main capsule) with parachute recovery. The second one was built with double layer shrouds (both top and bottom) and streamer recovery. The third was double layer bottom and single layer top with tumble recovery (no parachute or streamer) and no shock cord attaching the pieces together. I built these models in stages based on the outcome of the previous model (I intended on flying them until they broke). On the first model several things happened that caused a redesign of the rocket. The single layer main capsule was always getting very damaged (the single layer card stock just wasn't strong enough). Also, I could not keep the parachute from becoming 'char-broiled' (I think this has something to do with the inside shape of the parachute/streamer packing area). The second model fared a lot better with very little damage to the main capsule. However, I found that the rocket tended to be a bit on the heavy side. The third model is the one I continue to fly today. It is tumble recovery and sustains very little damage on recovery (if I fly it on a nice grassy field). I elected to provide (in the kit) a way of making the second model, as it was much more durable. However, this is where a streamer becomes necessary as the model is heavier (something was needed to slow the decent rate). If you are inclined to fly it 'prototypically', then you should have three parachutes on the main capsule (and provide whatever protective recovery means you want to the tower). Although, I think you will find it very difficult (maybe impossible) to pack three parachutes into the rocket and to get them to reliably deploy. Recovering the capsule and tower separately would eliminate the chance of damage (due to parts 'snapping' back at each other). However, when you pack the recovery devices (parachutes/streamers/what ever you use), make sure the upper device is packed underneath the lower. This will help insure that the lower device is 'pulled' out. (I have had cases where the lower parachute would not come out of the tight packing area of the main capsule). To reinforce the upper shock cord mount, just make sure there is ample glue saturating the cord and that it has at least 1 inch or more of the cord imbedded in the glue. Make sure the glue doesn't interfere with the balsa nose cone and it's fit to the main engine tube. If you fly it in two separate pieces, there will be very little stress on the upper shock cord mount. Because of the large 'cone' area of this rocket, it does not build up a very large velocity. At motor burnout, it decelerates very rapidly and will be traveling very slow at ejection (always use a short motor delay because of this). The double layer of shroud cardstock was my way of reinforcing the shrouds. The upper shroud is unique in that it is the support for the tower. With the single layer upper shroud, I would see damage if I tried streamer or parachute recovery (both pieces together). But, it would only sustain minor scuffs if recovered as separate units. Regardless of what recovery method is used, try to have the tower section fall horizontally (I know, it is difficult to determine this with out first flying it, and then it may be too late). I have found that if the upper and lower pieces are recovered separately using streamer recovery, and that if the tower is too nose heavy, that the tower will fall nose first and will actually accelerate towards the ground.

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