2/3 Scale Astrobee D build

[krislhull]

As several on here who know me, I have a strong interest in sounding rockets. My L2 was flight was on a MAC Performance 4" ARCAS, I have a scratch built 4" Aerobee 150 built using MAC canvas phenolic airframes, my in progress L3 build is a highly modified LOC 5.5" Sandhawk, and I have several other smaller scale builds of various sounding rockets. Back in summer 2020, I was itching to build another high power rocket, and having always liked the Astrobee D, I decided to contact Mike at MAC Performance about the possibility of putting together a one time kit of a 2/3 scale Astrobee D with a 75mm mount. I will say that he delivered with the usual excellent results! The only thing I am still missing for the build is a proper 5:1 ogive nosecone, but I will obtain one soon. And who knows, maybe we will see this as a MAC offering in the future?



All components laid out, with a 75/6400 case for reference

The recovery harness is yet another custom masterpiece from Teddy at OneBadhawk, drogue will be a a 16" Top Flight X form, and the main will be a 7ft Rocketman.
Electronics will most likely be a Eggtimer Quantum and a Stratologger CF with a MissileWorks RTx tracker.

And now, let the fun and games of the build begin! This will be a long build, due in part to my job, which keeps me on the road for 20 days a month, so I will only have a few days here and there in my 10 days off to work on it. I am currently planning on attending my first high power launch in 4 years this September, and I am hoping that this will be completed in time for that launch!

 

[krislhull]

First up, is securing the Y harness to the upper centering ring. Due to the 1/2 inch wide centering ring, I had to file down the parts of the hardware that overhung the edges. Some elbow grease and a little work with a file and my Dremel, I had the fit needed. There's not much room, but it will work just perfectly!






Alpha added for scale...

Due to the nature of the Y harness, a 75/6400 case is probably the largest that I will be able to fit in this rocket. Since the 75/7680 case is over 5 inches longer, I am not sure how well it will fit. I do not own one, so it really isnt an issue at the moment.

 

[krislhull]

Slow and steady progress has been made over the past week.

So far, the upper and middle centering rings have been secured to the motor mount and the whole assembly has been installed and expoxied in place in the booster airframe section.




The fins were then installed one at a time over the course of about 10-12 hours, with each fin being installed using the double butter method. Firs, however, each fin was thoroughly sanded along the root edge and tang for a proper bond.





Finally, this morning I started on the fillets. I used a piece of 1" PVC pipe dipped in gentian violet (a method I used on my L3 build) and drug it along the fin edge to mark out placement lines for masking tape for the fillets. A bunch of Rocketpoxy was then mixed up and used to make the fillets, using the 1" PVC piece as a tool to smooth the epoxy out. I currently have two sets completed, and I will hopefully get the final two completed by tomorrow, just in time for me to leave on my next 20 day work rotation.




I will post more when I get back from this work trip!

 

[krislhull]

Now that I am back home for my 10 days off, I have checked off a few more items on the Astrobee project. First up, last night I locked in the upper section of the forward centering ring with US Composites 150 epoxy. I then injected some epoxy onto the top of the middle centering ring through a hole I had previously drilled.

Today, I sealed in the top of the fins and the aft side of the middle centering ring by pouring epoxy in between the fins. I also sealed in the aft side of the forward centering ring by again injecting some epoxy.





I then decided to tackle the thrust plate. The MAC Performance aluminum thrust plates are a work of art, and it was a shame to ruin it by drilling out the 12 holes needed to mount the motor mount. I hit a major snag, though, on the first hole when my tap snapped off. I tried multiple things to get the broken tap out, but I am out of options with what I have on hand. I went ahead and tapped the remaining 11 holes successfully, and then test fit the Aeropack on it.







At the moment, I am torn between just leaving it as is, or trying some more to remove the broken tap. I am more than confident that the remaining 11 screws will be more than enough to hold the retainer on with a motor, and if I do go that route, I will cut the shank of the remaining screw and JB Weld it in place for cosmetic reasons.

 

[krislhull]

Not a whole lot of progress has been made on the Astrobee during my 10 days at home this month… as seen in the above posting, the internal fillets in the centering rings was completed, and the thrust plate has been drilled and tapped to accept the Aeropack retainer.

Today I installed the blind nut for the forward rail button attachment point, and also installed the coupler on top of the booster section. I received a new nosecone from Composites Warehouse today as well. The cone that MAC included with the kit is a Wildman 4:1 ogive, which while it is a quality filament wound nosecone, it is the wrong length and profile for an Astrobee D. Curtis at CW had the proper 5:1 ogive cone in stock, and I jumped on it earlier this week.





I also took a photo of the completed booster section with my just completed, but not yet painted, scratch built 1/6th scale Astrobee D. Looking forward to seeing the two of them fully painted and decalled up side by side!



Other than that, nothing has been completed, and it’s time to head back to work for my next 20 day rotation tomorrow.

 

[Sandy H.]

I'm sure there is crazy overkill on those screws, so missing one would be a non-issue. True, I've never flown 75mm, but those screws are just to keep the case in, not to take the thrust of the rocket. My 4" rockets use 2 #6 screws more often than not. My 5.5" rocket used either 2 or 3, can't remember.

I agree with the idea of putting in a fake screw head, just for aesthetics. Back in the day, I thought you could buy plastic fake screw heads, but not sure if that was a fever dream or something commonly available. With 3D printing, I'm sure you could get what you wanted.

Awesome rocket!

Sandy.

 

[krislhull]

I'm sure there is crazy overkill on those screws, so missing one would be a non-issue. True, I've never flown 75mm, but those screws are just to keep the case in, not to take the thrust of the rocket. My 4" rockets use 2 #6 screws more often than not. My 5.5" rocket used either 2 or 3, can't remember.

I agree with the idea of putting in a fake screw head, just for aesthetics. Back in the day, I thought you could buy plastic fake screw heads, but not sure if that was a fever dream or something commonly available. With 3D printing, I'm sure you could get what you wanted.

Awesome rocket!

Sandy.

It will retain the motor just fine with one screw missing... To me it was not worth spending $48 on a new one (after shipping). If this was for my L3, I certainly would probably be replacing it, but the remaining 11 screws will be WAY more than enough to do the trick.

 

[krislhull]

finally got around to spending a little more time on this project over the past couple of days. I started off by epoxying the switch band in place on the AV bay. And to my dismay, when I went out to take a look at it the next morning, it had slid down approx 1/16 of an inch in places, and left a very noticeable gab when I placed the airframe tube against it. And this is after I carefully measured it into place, used one of the airframes as a guide, AND taped it as well.... Oh well,



The solution was to apply bondo to either side of the switch band, wrap the airframe ends in wax paper, then bring them together to fill the gaps. About 30 minutes later, I pulled everything apart, and had two nicely filled gaps, with just a little sanding required. That brings me to this morning, where I marked out the locations for the mounting screws that will hold the upper and lower airframe sections to the AV bay, and then drilled four holes for 6-32 screws. I then enlarged the holes in the AV bay and installed PEM nuts. I then used a trick for indexing the parts that I saw on here. I am sorry to whomever it is that showed this trick in their build thread, but I cannot remember who it was! I just know that I saw it about 4 years ago... I drilled a 3/32 hole in the middle of the gap between the upper airframe and the switchband, and inserted a dowel, then cut it flush. Thin CA was then applied to the inside of the bay to lock it in place. I know have a upper airframe section that can only be installed one way. I repeated the process with the lower airframe, and used two dowels instead of one.


The holes in the airframe sections for the screws were countersunk as well, so that there will be no protruding fastener heads other than shear pins and the rail guides when completed. I then moved onto the nosecone. Since I will be using a GPS tracker in this bird, I am building a nose AV bay as wel, and as such, I am wanting the nosecone coupler to be removable, so I drilled holes and installed 4 PEM nuts into the coupler as well. I still need to countersink the exterior of the nosecone, as well as cover all PEM nuts I installed today in epoxy to lock them in, but that will have to wait until I am home next month.

 

[krislhull]

I barely worked on the Astrobee during this stretch at home. I did complete the nosecone tracker bay, however. The bay is built into the coupler, and it is fully removable from the nosecone with 4 screws. The tracker will be placed inside with bubble wrap taking up the excess space inside.





At this point All that is basically left is to paint the rocket and install the avionics. I will take care of the altimeter sled and wiring next month when I am home, and hopefully be able to paint it at the same time, weather permitting.

I think it is time to order some decals from Stickershock now!

 

[krislhull]

Came home from my work rotation to some great weather, so I was able to put the first coat of primer on the Astrobee D yesterday. Then today, my altimeter sled from Additive Aerospace arrived. The Missile Works RRC3 Extreme and Eggtimer Quantum were installed, and the switched wires up and installed. Holes were then drilled in the switch band for access to the arming screws, as well as an extra one for altimeter bay venting. I still need to install the wire terminals and charge wells on the able bay lids, and then the electronics bay will be complete.

I’m hoping to get the second primer coat and white top coat on before I head back to work next week, and then let the white dry thoroughly before applying the other colors on top and to the fins. I have decided to paint this to resemble round ADD015 that was flown from Wallops., as that one had the most colorful scheme of any Astrobee D that I have seen yet.

 

[waltr]

Good progress and looking forward to seeing the final paint and decals.

 

[krislhull]

The light at the end of the tunnel is getting very bright now!

over the past several days I have painted the Astrobee in the markings of round ADD 015, with a few modifications.
In the photo below, you can see that ADD 015 appears to lack the payload section below the nosecone, and above the silver strip that is the fly away launch lug. I have chosen to add the payload section as it appears on rounds ADD 009 and 010 to mine. I also do not have decals for 015, so I will be making a theoretical ADD 019.





Once all the paint was completed, I installed the thrustplate with attached Aeropack retainer with JB Weld.

The decals from Stickershock have arrived, and will be installed after ejection testing is completed, and then the final clear coat will be applied.

I had to add a separate battery tray below the Additive Aerospace altimeter sled, as the 800mah lipos i purchased are too big for the sled's built in battery holders. A few strips of plywood, some epoxy, and I had a new battery sled built. I also finished wiring up the altimeters and installed the terminals and charge wells on the bulkheads.

Finally, I had to get a shot of the Astrobee with my just completed Aerotech Astrobee D. These will look good together!

 

[waltr]

They both look good.
when is the first flights?

 

[krislhull]

They both look good.
when is the first flights?

I am hoping to fly it at Tri Cities Rocketeer's Sod Blaster launch over labor day weekend in Pasco Wa.

 

[krislhull]

Arrived home from my latest work rotation on Saturday to a package from Buddy Michaelson with my 8ft chute and a deployment bag. Today, I got everything set up, and went ahead and performed the ejection tests successfully.



Next up is to give this bird the Stickershock treatment, then clearcoat everything!
.

 

[krislhull]

Applied the decals from Stickershock today. Now all that is left is to clear coat the entire rocket and this build is DONE! Final weight comes in right at 13.6 pounds without a motor, and I was withing 2 ounces of my estimated weight.... not too bad!


Family portrait... scratch built 1/6 scale low power Astrobee D, Aerotech 43% scale Astrobee D, and finally my 2/3 scale Astrobee D

 

[JackC]

I am hoping to fly it at Tri Cities Rocketeer's Sod Blaster launch over labor day weekend in Pasco Wa.

Do you ever fly with OROC?

 

[krislhull]

Do you ever fly with OROC?

I do not. I have been wanting to get to Brothers for some time now, but just haven’t made it yet. At this time, any launch I can get to is a miracle, due to my job. The dates for Sod Blaster work out perfect for me to take a couple of vacation days and attend. It will be my first HPR event in nearly 4 years. Heck, my L3 project is completed and ready to go... has been since spring 2019,

 

[JackC]

I do not. I have been wanting to get to Brothers for some time now, but just haven’t made it yet. At this time, any launch I can get to is a miracle, due to my job. The dates for Sod Blaster work out perfect for me to take a couple of vacation days and attend. It will be my first HPR event in nearly 4 years. Heck, my L3 project is completed and ready to go... has been since spring 2019,

My son and I will try to make Sodblaster on the Sunday before Labor Day. I hope to see you there!

 

[krislhull]

My son and I will try to make Sodblaster on the Sunday before Labor Day. I hope to see you there!

Ill be there for the whole event, so you will probably see me! I'm hoping to get some fire under my L3 project for a shakedown flight on that Friday, and then if one of my TAPs is in attendance, and the predicted altitudes check out with reality, hopefully maybe get my L3 in on Sunday... will have to wait and see if the stars align for that one. Either way, I am hoping to fly the Astrobee a few times at least... Still trying to decide on a motor for its maiden flight

 

[krislhull]

The Astrobee got some fire under it’s fine today! It flew a flawless boost and descent under a K695 to about 3800ft(I can’t remember the exact number). However, it took some damage on landing. The rocket had to miss the nice, soft sod, and land on the hard and compact soil just outside the irrigation circle. There is some cracking on the aft once or so of the fillet on on fin. It will be easily repairable, but the rocket won’t fly again until I can make the repair at home.

 

[krislhull]

Now that I am back home, I was able to download the altimeter data from the RRC3, and perform a postmortem into a few issues that I had on the maiden flight of this rocket. As seen in the above post, the rocket appears to have landed on the tip of one of the fins, cracking the aft couple of inches of the fillet on one side. I was able to take a small flat head screw driver and use it to pop off the damaged area of fillet to reveal the phenolic structure underneath.



While I do not see any signs of cracking or separation along the fin mating surface at the root, I do see what could be a crack in the canvas phenolic fin that extends about .5" out from the root. Flexing the fin at the tip does not cause the defect to expand at all, so I am thinking that I might paint some US Composites laminating epoxy over the surface and let it fully cure, then reapply the fillet with Rocketpoxy. That should provide a fairly robust repair, and be relatively easy to accomplish.

The second issue I had was with the RRC3 primary altimeter. The day after I flew it, I was accessing the altimeter bay to read the RRC3 data with the LCD screen, and I noticed that the primary main ejection charge had not fired, and the Eggtimer Quantum backup altimeter is all that saved this rocket from certain death. When I tried to view the data with the LCD, the altimeter was telling me that there was no data stored. Upon getting home and using the mDACs software to run a diagnostic and download the data, I was able to get a full flight profile for the flight. I have no idea why the altimeter didnt fire the main, maybe it was a bad e-match. I have no clue. I will do some ground testing and see what results I get.

Either way, I am very happy with how well this rocket flew. It was a gorgeous straight boost on a K695R, with the RRC3 reporting a apogee of 3,841 ft, and the Quantum reporting 3,889ft.

 

[Hobie1dog]

nice project, Thanks for all the pictures.