Mercury Little Joe I

[MaxQ]

I had drawn up a sketch plan for a Mercury Little Joe with a cluster motor combinination.
This will be a light weight construction - along the lines of the Little Big Joe II Apollo project last year.

Once I found a suitable mandrel - the correct dimension for 1/12th scale (the hard part) I rolled a body tube with poster board to start this off and subsequently found a nice chrome finish poster board to skin it...
So, here's a progress report on the build.

 

[MaxQ]

With a wax paper layer protecting the mandrel, I spray mounted the exterior skin and laid it over the previously cured paper body tube.

The mandrel is larger (in length) than needed, no problem there.

 

[MaxQ]

Easy to pull the new double skinned tube, but I have to be careful handling it...it is thin walled and that nice surface needs to be protected.

 

[MaxQ]

Started the capsule which will be sized to fit a transition on top of the body tube/airframe.

The central load bearing part is a 38mm motor mount tube.
Turning cones is a trial and error thing, even when using nifty shroud calculators online.

Thinking ahead, I added a lot of internal balsa wood reinforcement to back up the paper poster board cone, which, since it won't be seen - I didn't mind getting a little sloppy with the cuts and glue...

 

[MaxQ]

The capsule/cone will be a replica of an early boiler plate Mercury capsule and will have a lot of vertical ribbing on the exterior.
The tough part will be rolling a good transition shroud for the capsule to mate to the airframe.
Again, I'm using a motor mount tube as the load bearing part internally.
The exterior of this thing needs to have a precisely radial cut shroud that will wrap around.

And it will need to match the capsule base and body tube dimensions precisely.
The dimension change of the transition on this version of the rocket is very subtle.

Given the foam board building materials, this will need some trial and error adjustment, these aren''t exactly high tech materials.

Again, I'm not "engineering" this thing like other fine builds here, this is a "low cost", "quick and dirty" build for amateurs like me.

I ran several calculations on the transition/shroud using online tools.

After several failures when trial fitting the results to the capsule and airframe, I tossed them and made an oversized copy on mylar sheet...
I wrapped the new mylar version around the transition base parts and then made trim marks to cut the thing down.
Sometimes you just got to say "Sxxxx It", and use the best measuring device, a trained eyeball......
This gave me something I could use....FINALLY.

 

[MaxQ]

trial fit....so far, looks ok.

 

[MaxQ]

Once I got the capsule foam core "floor board" trimmed "in-round" as accurately as I could, and the transtion properly sized...I cut a chrome skin for the transition/shroud too.
Spray mount carefully to avoid overspray of the nasty stuff on that fine chrome finish, and applied to the posterboard shroud.

 

[MaxQ]

Assembling airframe components is next.

Need to take some more pictures....

 

[MaxQ]

The transition works.

And the exterior finish of this airframe and transition looks real nice....
If I can keep it clean during the build, I won't have to worry about priming and painting a decent silver/aluminum finish.

 

[MaxQ]

The next "build items" will include :

- escape tower
- escape rocket motor and nozzles
- internal thru the wall fin structure and fin skins
- cluster motor mount assembly and recovery harness points
- capsule exterior details

See 'ya later

 

[MaxQ]

The capsule will need the forward nose cone section, the little conical cap on the front that attaches to the inside of the escape tower, and the reinforced ribs that are around the capsule exterior.

I turned the little cone with a sheet of mylar. I'll fiberglass that after test fitting and trimming.

Plastic strip was cut and cemented to the capsule exterior wall with liquid cement.

 

[MaxQ]

The tower will be made from wooden dowels of various sizes..they are a little larger in diameter than the actual "true scale" dimensions indicated, - but the dowel selection was limited...and I figured erring on the side of a slightly larger size couldn't hurt for strength...

I made a jig for the tower after dimensioning the three vertical parts from a scale plastic scale model kit.
Taking critical dimensions from a kit and transferring them sure makes this build go much quicker than figuring out the assembly from a few photos and elevations....

I sketched the triangular cross section and the base ring for the tower, and took a dimension midway inside the tower and set up the dowels and started tack gluing it together.
The diagonal braces were then cut and glued in while the tower was on the jig.

 

[MaxQ]

The best part of a "scratchbuild" is when you pause, and take a look at the assembled pieces...around the time it starts to look like something.

 

[Pantherjon]

Looks awesome!

 

[JoeG]

Looks great! Lots of good info too.

Any time I try to build a tower it seems to lean a little.

 

[Micromeister]

That's some beautiful work MaxQ. Great job.

 

[MaxQ]

Thanks Guys!

Can't wait to see how this will look with paint on it...some flourescent Orange on chrome will be cool.

 

[MaxQ]

Looks great! Lots of good info too.

Any time I try to build a tower it seems to lean a little.

Towers, yeah.
This one has a slight lean as well, which I will deal with.

Wood dowels have warps...I went thru two dozen at the LHS and pulled four that were fairly straight.
But uneven ends and a slight bevel on a cut will result in a lean...

I have a ring I am making for the base of the tower which I'll need to apply shims under one side and true it up.

I am on "hold" for a collection of 24mm, 29mm and 38mm MMT's...but I'll be trying to keep the build thread going...

I will probably have four 24mm's, four 29mm's and a central 38mm.
I know the central 38mm is not true to scale...there was no central motor on the full size Little Joe I.

But my philosophy on clusters, and particularly airstarts, and mixing BP with composites, is to have a central motor that will fly the rocket by itself (if the outboards don't light) and all the outborads for fun, when they do.

I'll be putting a timer behind a hatch with a pull pin...this to deal with problems I experienced with airstarts on my Apollo Little Joe II.

 

[billspad]

Towers, yeah.
This one has a slight lean as well, which I will deal with.

Mercury towers had a little bit of a lean to them so the tower would move away from the flight path of the capsule when it was jettisoned.

 

[bsexton]

What is it with you and "Joe" rockets?

Seriously, looks like another great project and once again you are proving bigger rockets don't have to be heavy rockets.

 

[Meatball 1]

Lookin' good once again, Jim.

 

[MaxQ]

What is it with you and "Joe" rockets?

Seriously, looks like another great project and once again you are proving bigger rockets don't have to be heavy rockets.

Well, the light weight makes it more affordable to fly.
Smaller motors...slower takeoff speed.


And a slow moving "scale model" rocket just, looks more realistic.
To me anyway.

After this "Joe" I may not know what to do...I've run out of "Joes"....

 

[MaxQ]

Mercury towers had a little bit of a lean to them so the tower would move away from the flight path of the capsule when it was jettisoned.

Maybe I should leave the lean - in, then?

Any idea how much deviation from true 90 degree vertical we're talking?

(Or are you jivin me?)

 

[GuyNoir]

Or are you jivin me?)

I suspect Bill doesn't know how to jive.. . .:roll:

 

[billspad]

Maybe I should leave the lean - in, then?

Any idea how much deviation from true 90 degree vertical we're talking?

(Or are you jivin me?)

I do know how to jive but I'm not.

I've got a bunch of drawings and a file cabinet draw full of Mercury Little Joe stuff. I started collecting it so I could build one and ended up with so much detail that I've never had the time to do it right. Ten years ago I took a drawing I got from NASA and had it scanned and converted to a vector drawing so I could clean it up in AutoCad. While doing that I "fixed" the tower to make it straight. I later learned that was a mistake. I can't remember the number but it's small. On some of the earlier flights they just shimmed where the motor attached to the tower enough so the centerline of the thrust was offset an inch where it passed through the center of gravity.

I think I attached a .pdf of the cleaned up drawing.

Here's a trivia question for you. There are a couple Marman clamps on the capsule and tower. The biggest one holds the capsule to the booster. Who invented the Marman clamp? Googling is not allowed.

View attachment cap.pdf

 

[rocketguy101]

After this "Joe" I may not know what to do...

Little Joe III ? Not quite as interesting...

 

[g_boxwood]

Max, that's a cool project and I do agree with you about the finish: the chrome/bright orange pattern will simply look amazing!

Nice work on the capsule detailing, prior to commit myself to the Apollo LES I wondered wether to model a Mercury or an Apollo capsule, maybe the Merc will be next!

Keep it coming!

 

[MaxQ]

Here's a trivia question for you. There are a couple Marman clamps on the capsule and tower. The biggest one holds the capsule to the booster. Who invented the Marman clamp? Googling is not allowed.

Mr. Marman?

Dunno...but whoever did made their marx in the history of industrial design.

 

[MaxQ]

Max, that's a cool project and I do agree with you about the finish: the chrome/bright orange pattern will simply look amazing!

Nice work on the capsule detailing, prior to commit myself to the Apollo LES I wondered wether to model a Mercury or an Apollo capsule, maybe the Merc will be next!

Keep it coming!

Thanks , been enjoying your project.
I'm in awe of your technical skills.

 

[billspad]

Mr. Marman?

Dunno...but whoever did made their marx in the history of indstrial design.

Did you peek or did you know?