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The Nescorna Rocketworks construction blog has moved, to http://blog.NescornaRocketworks.com.

Plans and Details

I ordered some Apollo plans, scale drawings with color schemes, produced by David Weeks (RealSpace Models). 1:48 scale, Block I and Block II, including (some of) the details on the EVA rails. Along with a couple of other diagrams and mission photos (in hand now), I'll have enough details, I think, to model Apollo 15 pretty accurately.

Next steps: finish the LES, decide which spirals to fill in the tubes and fill those, check for defects and gaps in the wraps (plastic and paper), prime, and paint. Oh, and attach the various jellybean parts to the different stages.

Apollo 15 Details

As I get closer to finishing building the Saturn V's structural components and beginning the finishing, it's time to think some more about Apollo 15's details.

Apollo 15, 16, and 17 included a space walk for the Command Module Pilot during the trip back from the moon. (This wasn't just to give the CMP one of the cool things on the mission, a sort of consolation prize for minding the store while his buddies cavorted on the moon. There was some film to retrieve from some additional cameras in the SM. Remember, 1970, no digital cameras with wires to remote memory.) To assist the CMP on the journey from the CM to the SM, a set of rails and foot holds was added.

The rails on the CM leading from the hatch to the SM are covered by the BPC (boost protective cover, in place until the launch escape system is jettisoned), so those are not visible during launch. The rails along the top and sides of the SIM bay (Scientific Instrument Module), though, are visible on the pad and during launch.

Questions, then: how big, how long, how many, and just where?

To Fill and Sand?

The end of construction is in sight! I might even wrap up this evening, completing the LES and building the RCS nozzles (gotta love NASA's plethora of TLAs, eh?).

Soon, I'll need to decide whether to fill the spirals in the body tubes or not, or maybe to fill just some (e.g., the S-IVB). Sure, it will look nicer, assuming I have the patience to do a good job. My biggest concern is that I might damage one of this crazy vacu-formed wraps, or even the paper wrap on the LM shroud. As it is, I have just a little repair work on the wraps yet, including patching a gap in one of the wraps (it was about 2mm too short, and, even though the joint is beneath one of the tunnel covers, the tunnel cover extends only part way up the wrap).

LM Shroud Done

We're building the stack from the bottom up. Most recently, I've completed the LM shroud transition, atop the S-IVB. Next up will be applying the SM wrap.

The rocket is starting to look like a Saturn V! There's a long way to go yet, but with the CM atop the SM tube, even without the wrap, the silhouette is sure familiar (though still missing the LES atop the CM).

No serious problems, though, since that misaligned S-IVB wrap.

Mis-aligned Wrap!

Oops.

I mis-understood one of the alignment instructions. It was plenty clear: I merely blew it.

The S-IVB has two wraps to model the ribs, one on the forward end of the stage, one on the aft end. There's a tunnel cover that stretches between them (overlapping each). So, the alignment mistake—about 20° off, rotated around the body tube—is more than just cosmetic, since there are flat spots in the wrap where the tunnel covers attach.

What to do?

I thought about just cutting the wrap where the tunnel cover needs to go, perhaps using the cut piece as a graft over the molded-in flat spot. I considered cutting the body tube in half, making a stage coupler, and rotating the two pieces to align the wraps correctly. I briefly gave thought to ripping off the wrap and replacing it with a new one.

I decided to try to remove the wrap and reapply it.

Some parts of the wrap came off the body tube very easily, but some were extremely difficult to remove. Where the CyA didn't wick very far under the wrap, it came off easily.

I used a hobby knife, very gingerly, to pry the wrap up, occasionally using CyA debonder to try to dissolve the CyA. (I'd tested it on some wrap scraps.) In a few spots, I had to cut a layer of the body tube away in order to lift the wrap off. There's one bad tear, a nick, and a couple of very small cuts, but the wrap came off in a reusable condition!

It's now back on the tube, properly aligned. Rather than wicking CyA again, I used canopy cement: I didn't want to take a chance on the wrap dissolving or cracking more from the CyA, so I just applied a thin layer of canopy cement to the edges of the wrap, laid it up, and taped it to the tube. Back in business!

Are the Wraps Just Old?

I applied the S-IVB transition wrap this evening. It cracked.

There was a little stress on the wrap, tangentially, in order to keep it tight. The CyA created a few cracks in the forward (small) edge. (Side note: I probably should have just glued this wrap down to the paper transition with canopy glue. I'm using that on the edge joint and on the aft [large] edge: I didn't want to take another chance with this wrap.)

I wonder if these wraps are just a little old. Does the chemistry of the wrap change slightly with age, making them more susceptible to developing these small cracks? I bought the kit about ten years ago.

Of Rings and Sealing Wax

Well, no sealing wax: just sealing thin CyA.

The large tube (S-IC, Interstage, S-II) is done, except for touch-up, masking, and painting. It's on to the S-IVB now. First step is to build the transition between the S-II and the S-IVB (big tube and third stage). This requires building a centering ring-couple set between the small S-IVB tube and the large tube that comprises the S-IC and S-II.

Ideally, this is pretty easy: two centering rings, and a coupler constructed earlier (one of the first steps) by slightly sectioning a small piece of tube that's the same size as the large tube so that it just fits inside the large tube. I made this coupler just a little too big, so out came the sanding block and, since I took off all the outer layers (the ones that coat the cardboard fibers to keep them from fraying), the thin CyA to reseal the coupler. Then, more sanding, since the thin CyA causes the outer fibers of the cardboard to swell, and the surface gets rough.

Just about done, though. Then, it's on to attaching the wrap that gives me the most cause for concern: the third stage wrap, that overlays the transition's taper.

Specialized Techniques, Ullage Rocket Scars

Building the Apogee Saturn V requires all these specialized techniques that I've not used before. Letting CyA wick to seal the edges of the thin plastic wraps, feathering epoxy clay to smooth over joints that don't meet quite perfectly, and who-knows what else in the offing.

I had to come up with one of my own (the two above are in the instructional videos that come with the kit): drizzle a little canopy cement and let it wick—sometimes help it wick—under an edge of a plastic wrap. I used this technique to seal the edges of the scars from the ullage rockets that I removed in order to model Apollo 15 more closely.

The frustrating part is that just about when I get comfortable and competent with one of these techniques, I'm done using it on the rocket!

Fin Fairing Wraps, and Manufacturing Tolerances

Finally: the fin fairing wraps are attached! Unfortunately, some of the manufacturing tolerances are a bit loose. None of the wraps seemed to extend quite as far as I'd expected. It's just a bit of extra craftsmanship to get things looking reasonably good, but it would be nice if the parts were made to better tolerances. (The same issue applies to some of the large tube wraps: they're too short!)

STB-1

I'm working to determine the limits of indirect staging (sometimes known as gap staging): how far apart can the booster and sustainer motors be, and still get reasonably reliable ignition? I built STB-1 (Staging Test Bed #1), pushing the first stage out to about 40 cm, staging an Estes D12 to a B4. The first flight worked perfectly, though there was some interesting tip-off shortly after launch and an odd sort of corkscrew in the flight path.

The second flight wasn't nearly as successful: the sustainer failed to light.

The booster motor mount tube has four vent holes, roughly 3mm diameter, about 4cm or so from the top. These vent into the airframe, with vent holes drilled into the middle and after centering rings (BT-60 airframe). I'd thought that, perhaps, the failure's cause was clogged vent holes in the middle centering ring. Post-flight dissection showed that not to be the case.

The sustainer's motor mount had been dislodged and shoved well forward in the airframe. I couldn't tell if this happened on impact or during staging—I would guess on impact, though. There was a small hole in the forward centering ring, though, to provide clearance for the sustainer's engine retaining hook; after the second flight, it looked to me as though that hole had grown. It's possible that the stages are too far apart for reliable ignition, and it's possible that the hole in the forward centering ring allowed enough pressure to vent forward that the stages separted before sustainer ignition. (That forward centering ring is too far forward: it should not be impinging on the sustainer's engine hook.)

Perhaps more testing to come.

Peeling Warps

After all that work to get the wraps down well, it's time to peel up a few small sections. Some of them are at the gaps between edges of a wrap, and in some of these I didn't go nuts trying to get those edges down, knowing that a tunnel cover would run over that. But, in some cases, it seems that the CyA wicked much further under the wrap than I'd have liked, especially at the forward end of the first stage tunnel cover.

It's painful.

It would have helped, I think, if we'd had some written instructions to browse: it's very difficult to browse quickly through the video instructions. A few more specific hints in the sections on attaching the wraps (e.g., "avoid getting glue under this-and-such part of that-and-such wrap, because you might want to remove that part of the wrap when attaching the tunnel covers") would really have helped, I think.

Time for Tunnels

Time, finally, to get the tunnel covers shaped, smoothed, primed, and glued. And the launch lugs. And, and, and. I'm glad to be back working with something other than those wraps!

Krystal: Success!

Success!

Krsytal flew well! Twice, to ensure it wasn't a fluke. All four engines lit both times: three in the booster, one in the sustainer. Booster pods deployed their chutes just fine.

Cliff asked me to write an article for the'Clips.

Krystal Ready to Fly

I finished Krystal yesterday evening, attaching the pair of 30cm chutes to the booster pods' shock cords. In retrospect, I should have gone with BT-50 pods, to allow for at least a nylon chute and a heat shield, maybe even 45cm chutes.

Tomorrow's the big day, then: first flight. I'm hoping to get some good photos and maybe a slow motion video (if Cliff's at the launch). Watch this space and the Rocket Works Web site!

Minor Snag: Nose Cone Interference

A minor snag on Krystal, at least slightly anticipated. The pod nose cones interfere slightly with the booster main body tube. I thought this might happen: I probably should have just built a shim onto the pod in the design. I caught this flaw during test fit, before gluing the pods to the booster, so it's easy to add the shim: cut a couple of thin strips of 1/32" balsa (one for each pod), paint the edges flat black to match the pod. Shouldn't be a big problem, just a minor delay.

Krystal Update

I mentioned this rocket called Krystal that I'm building, in Display Nozzles and Other Distractions and The Joys of Tools. For details on the rocket, see its section on the Rocketworks Web site.

Painting is now almost complete. The final color scheme has a red body, gold fins with a few red highlights, black pod body, gold nose cones and transition, and white vent fairings. The only bit left is to paint the fairings.

Assembly remaining: attach the pods, parachutes, and parachute protectors.

I discovered what would have been a big mistake last night while painting. I'd not yet glued the sustainer motor mount into the body tube! The fit is pretty tight, so it didn't simply fall out, nor did the rocket slide around while painting (I use a stick inside the motor mount tube to hold the rocket). I'll correct the oversight this weekend, I expect.

Epoxy and Wrap Edges

It worked!

I was very nervous about securing the few remaining edges and corners of the main tube wrap, given my experience with melting CyA when the plastic is under any stress (radial or tangential). Last night, I tried 60 second epoxy to secure a few of the errant edges: seems to work very, very well. Plan now is to finish those up, then get the tunnels sized, shaped, and sealed, and move on to whatever's next.

Display Nozzles and Other Distractions

I've been working on the display nozzles. That might seem like it wouldn't take much time: just glue them together, assemble the base (to which you attach the nozzles, which is then inserted in the bottom of the rocket), and paint. Well, the base was a bit snug inside the bottom of the rocket, so it was time to sand it down. I then wanted to ensure the base didn't fray, so I applied a light coating of thin CyA, which, as expected, required a bit more sanding. I've finally masked off the nozzle attach posts and sockets, and once the weather clears I'll prime and paint.

I'm also distracted by an interesting scratch-built two-stage rocket, unrelated to the Saturn, that's required some engaging engineering solutions. (See the October 18 entry, The Joys of Tools for one example, and there've been numerous others.) That rocket, called Krystal, is now mostly assembled and in primer. It needs some sanding of the primer (especially the booster fins and the interstage transition, which will be tricky—for which reasons you'll have to await a future posting), then painting. Painting won't be trivial: dark red body (booster and sustainer), gold fins and interstage, white interstage vent fairings and nose cones, gold pods.