3/4 Mercury Redstone

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TRF,

Our goal is to complete construction on 31 January. That is just two weeks from now. A lot to do in short time.

Progress is made on the booster (tail unit). First we fabricated a frame for both assembly and shipping. It is made from 1-inch steel tubing and locking castors. Note the booster is 120 inches length and 117 inches span. It weighs about 220 pounds. We think the frame is a good investment given the booster’s scale.

The assembly frame is pictured below. Note second photo where we added A-braces on either end along with some corner braces. The fame is quite stiff.

Servo boxes are built up including internal X-braces. Those appear strong and tough. Still we may fill those with 3 pound density foam. There is a lot of momentum in a near 300 pound booster landing 15 feet per-second.

Rudder boxes are also built. Those will be foam filled pieces considered sacrificial “bumpers” to an off center booster landing.

This coming weekend is devoted to skinning the booster. Will be our most challenging piece.

Feckless Counsel

Booster frame looking aft.jpg

Booster frame looking forward.jpg

Booster frame side view.jpg

Booster loading to trailer.jpg

Booster assembly frame.jpg

Rudder boxes.jpg
 
Wow, the fins are impressive. What is the thickness?

I just might have to make a road trip!

From the Ether...
 
John & John,

Altitude is lowered to 1km or 3,300 feet. That keeps us in the field with apogee deployment. Hoping for a gentle pull on top.

Djs,

"Short" cord means about 3 feet. Really is a “riser” just long enough for shroud lines to clear the canister.

Les,

So good to hear from you. I recall we bought the X-Celerator kit same Black Friday sale. Had a good time collaborating across our builds. I believe, old man, that year was 2010?

Fred,

You are TAP for this bird. Anything you want to see, bend or yank better get up to the shop now. We are closing it up and off to paint next two weeks.

Tim,

Fins at their thickest are 6-inches. That is right where fins meet their rudder guards.
 
As large as that is, you might consider an FX pipe conduit near launch time to simulate LOX venting.

330q-13[1].jpg

Greg
 
A cool idea from a visual standpoint, but I imagine the team will already be facing as many complications as they can handle.
 
I hope this flight is nominal so the ecstatic celebrations can begin. My inexperience says to try and set her down as slow as possible (stupidhead here says use a big chute) to protect that rear end for future flight endeavors. Kurt
 
Careful, cryogenic temps make many materials brittle...

Plus large temperature changes can destroy glue joints when dissimilar materials are joined; if the thermal expansion of the materials is different, you could start popping joints. The skin could come off the frame, or crack.

Make sure any dry ice is well insulated and separated from anything structural. While it would be cool to have special effects, it's not worth it if they compromise the whole project...
 
Fred,

You are TAP for this bird. Anything you want to see, bend or yank better get up to the shop now. We are closing it up and off to paint next two weeks..

I have been following along and we have talked. I am good with it. If you are working this next weekend, I might be able to make Saturday, just to eyeball and cheer you and your team on... So, don't slow down for me... You have my phone and email...
 
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TRF,

This weekend was another 20 hour marathon session. Applying skin to the booster is, as we suspected, the most difficult phase of construction. Using templates we cut fiberglass for the leading edges, body and fin valleys. Our decision was to apply fiberglass in that same order. In retrospect it may have been cosmetically better to go leading edge, then fin valley and then body.

Rudders are filled with US Composites 3 pound density expanding foam. Advertised expansion is 20:1. Each rudder is 19 liters. We used 1 liter of mixed material and have the result illustrated below. Next is saw off the excess and apply the final skin.

We have made escape tower rocket nozzles using scraps of fiberglass skin and plywood templates. We will probably also fill those with expanding foam.

Feckless Counsel

Fiberglass cone.jpg

Cutting fiberglass patterns.jpg

Foamed rudder.jpg

Booster skin overhead.jpg
 
TRF,

Booster is now completely skinned. That application was the most tedious and time consuming phase of the project. Several mistakes had to be reworked but overall we are happy with the outcome.

Capsule is well underway with about 80% of its surface skinned. We expect to finish capsule this weekend along with a few remaining tower parts

Then we have long list of punch out items. None of those tasks are extensive but there are a lot. Hope is we ship out to paint and decoration 26 February.

Looks like we are on track for an early April launch.

Feckless Counsel

Booster and rudder.jpg

Booster skin in progress.jpg

Booster with dude.jpg

Capsule with skin panel.jpg
 
Mike Walsh,

Thank you for your reply. Yes, we will ground test. Hopefully we will have time to post some video. Will let you know.

TRF,

May I please update those still interested in this project?

All major rocket components are complete except the escape tower. Electronics enclosures not yet installed. Tower components and enclosures are in process as printed Nylon SLS parts. We hope to have those this week but it’s hard to rush free.

We have been weighing parts and measuring CG. As pictured blow we are hanging parts to weigh and to locate CG. Airframe tubing is straight forward. Things like booster and capsule have been more difficult. For those awkward shapes we weighed each end, forward and aft. Then we calculated the ratio of end weights to total weight. That gave us CG from either end. We compared those measurement with computer simulation to good correlation.

Now we are stacking and pinning each section to another. Pinning is achieved through fiberglass tubes and dowels. The dowels of one section fit the tubes of another. That is cross-pinned with a hinged clevis and tensioning spring. The pin and pinning window are pictured below. Windows will be covered by patches held with Velcro.

We hope to ship out for paint and decoration end of the month. Then we can focus on propulsion and a launch tower.

Feckless Counsel

Booster CG.jpg

Pinned segments.jpg

Hinged clevis with spring.jpg

Capsule CG.jpg

Aerobatic stacking & pinning.jpg

Airframe weigh and CG measurement.jpg
 
TRF,

May I please update those still interested in this project?

I tend not to post in build threads too often as to avoid cluttering the threads and I have absolutely no useful knowledge to contribute to a project of the scale, but wanted to let you know I am very glad you are posting the build process and challenges for those of us who will not get to have our own giant scale model builds so we can live vicariously though your efforts. A seriously amazing rocket so far and I look forward to seeing the footage of the launch when it occurs.
 
TRF,

Received Nylon electronics boxes from selective laser sintering. These parts are of outstanding quality. They are accurate, tight tolerance and tough. There are no supports as the process is powder embedded. This material will not soften in the sun like PLA.

The most complex box fits the antenna fairing. That box is illustrated below. Flanges remain below the skin. Note several “adhesive keying holes” on the flange. Screw mounted door is proud of flanges and just flush with skin. The door supports a single breather hole that sits between two Shurter-style switches.

Inside the box are screw bosses for two independent deployment systems. One is an Adept22, a switch and a 9V battery. Other is an RRC3, a switch and a 9V battery. Recall that system was tested page 5 of this web log.

Feckless Counsel

Fairing box C.jpg

Fairing box B.jpg

Fairing box A.jpg
 
That's gonna be one gorgeous AV bay! Looks like things are looking good for a potential 4/7 launch!
 
You mention calculating the CG.. where is the CP at for this rocket? Did you do a full size cardboard cutout? :)
 
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