SpaceX Falcon Heavy Build 4.0 (1:65 Scale, BT-70 tubes) - a work in progress...

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In the meantime I intended to install the fins tonight, with an new way to avoid glue or a soldering iron to hold them in place. But I got distracted by an idea to redesign the 9 core motor mount. The current motor mount is fragile, takes 4 hours to print, requires a lot of post print clean up, and the tedious and sloppy installation of motor retainer clips.

The new design takes 90 minutes to print in two parts instead of one. So modifications can be done twice as fast and damage to one part means I can still reuse the other part. It weighs about the same but has about 1/3 the number of primitives in the CAD drawing, also making it much easier to modify. Tonight with two test prints, I got as much progress on the new design as a week and 6 test prints with the old design.

The old design. Engine block in red. Note the thin plastic defining the E vs A10 motor boundaries.


The old design could fly with any number of motors since each motor mount was self contained. The new design uses the E (or D) motor to hold the A10 motors in place.


New design: the core is hollow, the A10 motors are moved directly against the E motor and the space gained is used to make a stronger perimeter.


The new design removes the step of welding the retainer clips in place. In fact, the motors are packed so tight, the A10 retainer clips are not even needed. Note: I did add holes and tabs to hold A10 retainer clips, which I need to remove.


The old design had the the E motor stop built in, which was redundant to the BT-50 to BT20 adaptor that I use. And the E motor retainer clip didn't fit without bending the end straight and bending back again. In the above photo on the right, the end of the E motor clip was broken so I taped it into place.

All of that work is eliminated with the new design.

The new design is printed in two parts that snap together so tight I don't think they will need glue or welding.

The top part:

and bottom part:


Here you can see the new design test fit on the right booster compared to the old design on the other two cores:

I need to fix the new design so the motors extend a bit further out but you can see how much cleaner the mount works and how much thicker the mount is on the outer diameter. I also need to reduce the diameter of the motor mount so it fits into the booster without sanding (another chore I hope to eliminate on my next build).

Tomorrow, I'll get back to the fins that fit into the slots in the core landing legs.

 

[jmasterj]

So it appears I have a high power rocket that I cannot use for a Level 1 certification and cannot fly without the Level 1. Or, I can scale back the number of motors until I'm below the 125g limit. Or build another rocket for the Level 1 cert & then fly the Falcon Heavy after that...

Correct.

 

[Switch]

Correct.

OK, so I'm also going to build a rocket that can qualify for a NAR Level 1 certification. I'm not ready to start another project from scratch, so I ordered a Zephyr from Apogee Rockets. I've been planning to do a SpaceX Starship on a 4" body tube design, so I'll gain 2x on the experience.

 

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Tomorrow, I'll get back to the fins that fit into the slots in the core landing legs.

So today is the tomorrow of yesterday and as promised I did work on the fins.

I'm using 1/32" polycarbonate, which I used on my 1:95 scale SpaceX models. My 1:65 scale Falcon 9 Crew Dragon has flown stably with this gauge plastic for the fins, but it feels flimsy & I may change to 1/16th polycarbonate later. I don't like heavy fins on a hinged landing leg mount. So I'm going to stick with 1/32" for now. I do think I can make the landing legs thicker along the slot & that will make the fins less flimsy. That is also something I plan to fix on the next build that I've started.

On my Falcon 9 Crew Dragon, I used a soldering iron to melt the polycarbonate plastic fin into the landing leg.


I really tried to minimize the damage to both but it really isn't much different than using glue, which I'm trying to avoid. What I don't like about welds and glue is they fuse parts so that if one part fails, both parts need to be redone.

Here's the finished fin:


I originally planned a "snap-in" fin that had notches at both ends. But I found the screw that secures the landing leg to the telescoping tube interfered. I could fix that by shortening the fin slot in the landing leg but that would require 12 hours to reprint all 4 landing legs. Time will tell if what I did instead is better, but I drilled a hole for the screw instead (top in above photo) and did a much more robust notch on the bottom.

Once I had my prototype working, I made four more copies. I've learned to always keep the prototype to make additional parts (and as a spare part).


I cannot reveal my source for the polycarbonate plastic due to a confidentially agreement.

Here is the inside of the landing leg where the screw that holds the eyelet for the telescoping tube also holds the top of the fin. I may decide to use the 3D pen to add some PET plastic on the inside of the landing leg to make the fin fit tighter. But it is not a high priority.



Here's the finished install:




Still on the to do list
1: Finish motor tubes for recovery.
2: Upper thrust strut booster mounts
3: LH2 and LOX lines
4: Launch lugs
5: cluster ignition configuration*
6: Other stuff (like build a Level 1 qualifying rocket)

* I'm working on the cluster ignition on the thread I started for the 9 cluster Falcon 9 Crew Dragon

 

[Switch]

Still on the to do list
1: Finish motor tubes for recovery.
2: Upper thrust strut booster mounts
3: LH2 and LOX lines
4: Launch lugs
5: cluster ignition configuration*
6: Other stuff (like build a Level 1 qualifying rocket)

* I'm working on the cluster ignition on the thread I started for the 9 cluster Falcon 9 Crew Dragon

Today I finished the thrust struts. Which just required carefully drilling out the mounts in 0.1mm increments until the fit properly. I need to find an alternative to the black rubber band that retracts the thrust struts.


Mostly, today I wanted to finish the recovery.

This is the top of the core motor mount. Note that I'm taking care to tie knots that can be easily untied.


Also, I really need to stop using electrical tape. It is already coming undone. Any how, this string is used to attached the elastic band for the 36" parachute.

I'm using these to attach the chute to the band but also as an aid to retention and release of the chute:


And of course Kevlar™ string (super glue is for the ends of the cut Kevlar™


This loop is to tie the the chute to the swivel.


Nylon parachute:



I'm not sure I like this solution & I may go back and change the attachment.

This isn't the best shot, but the swivel is in a slot on the centering ring putting tension on the elastic band:


The elastic band, in turn holds the chute around the motor tube using 3D printer retainer rings. The retainer rings keep the chute from moving during launch so I can keep it as close to the top as possible. They also keep the chutes from fouling on the inside of the rocket body tube during ejection.


The rings have a slit so they pull free when the motor tube ejects after BECO or MECO.


Here's the completed booster motor mount. The top string goes though a hole in the magnet mount.

Here you can also see the swivel in the slot on the centering ring. The swivel will be attached to a string that is fixed to the outside at the top of the booster (or core), so that swivel is pulled off the centering ring during motor ejection, it will release the chute and the booster (or core) will then land legs first.

I still need to add the string that goes to the outside.

In the meantime, I also worked on the fuel lines:


Also, I got tired of looking at all of those brown motors and came up with solution of painting the motors black and using a silver sharpie to draw the bell nozzles.

I also painted the bottom of the motor mount black (I should have printed it in black in the 1st place).




Fuel lines installed & motors painted.




Painting the motors is a bit of a hack but I hadn't planned to do anything about them. So I'll count it as a WIN!

Still on the to do list
1: Finish motor tubes for recovery (attach to outside of boosters and core)
2: Launch lugs
3: cluster ignition configuration
4: Other stuff

 

[Switch]

Last night I started work on the Zephyr kit from Apogee and learned how insane the shipping costs are for H motors. $60 bucks to ship a $50 motor to launch a $100 rocket.

2: Launch lugs. I ordered 1" rail lugs from Apogee Rockets
3: Cluster ignition configuration. I have a proof of concept circuit worked out and parts ordered. More details are posted on my cluster launch thread.
4: other stuff

Ahh, other stuff...

SpaceX CEO, Elon Musk likes to refer to the launch complex as "Stage zero" and in one interview he commented that rockets are much easier to build (and less expensive) than the launch complex itself. And so my Falcon Heavy project turns a corner when I realize that this rocket is not going to launch successfully if I try to hang it on a 1/4" launch rod by it's lower launch lug & try to ignite 27 motors with "a clip whip from hell".

So I started thinking about how I would actually rig this rocket on the launch pad. I know from experience with my 1:90 scale Falcon Heavy and Delta IV, that cluster rockets are much more difficult to mount on a lunch rod and ignite than single core rockets. They are simply heavier and the weakest angle of the booster mount is when you hold the rocket parallel to the ground by the core with the boosters hanging sideways. Hell, even transporting these rockets is difficult. I need a way to transport this Falcon Heavy to a launch site, then get it on a lunch rod in once piece with all of the igniters connected and with continuity on all 27 motors. After my successes with the 9 cluster Falcon 9 Crew Dragon, I thought, "OK, I just need to strap three of these cores together like I did with the smaller scale version". NOT SO. This is more than 3X more difficult!

So starting with Problem 1 Transportation: I need a way to transport the Falcon Heavy that protects the fins (which take up quite a bit of space) and other delicate parts. I'm trying to minimize on site assembly cause I know what it is like to lose a spill a box of eyeglass screws in the sand (hint have the kids collect them with a magnet and learn that some of the sand is magnetic). Problem 1 is related to the first part of Problem 2, which is getting the rocket on the launch rod in one piece. Both need a common solution...

So what I'm thinking is to design a strong back.


On my first attempt at a strong back, I'm not going to worry about scale or appearance. I just want something to hold the rocket securely in a box for transport and then be able to get it on a launch rod in one piece with minimal disruption to motors and igniters.

To hold the motors and bottom of the rocket, I created a clamp with three rings:

Here it is on the Prusa i3 MK3 printer. I designed this as one piece and then "cut" it into two parts with a solid rectangle in the FreeCAD software. Then I realized I could still print it as one piece!



I designed the lower clamp to hold the motors (rather than the rocket itself) for several reasons:
1: I don't want the motors to fall out when I move the rocket to the pad
2: I don't want the motor tube to fall out when I go over rough roads in my truck.
3: The lower section of the body tubes has a horribly complex shape with hinges for the landing legs and booster mounts which are also fragile.
4: I can keep the profile of the lower mount inside the launch rod



and viewed from the side.


Also, a note about the paper skin detail at the bottom of the core and boosters; I have the skins that I plan to apply below the landing leg hinges. But I'm waiting until I'm done handling the rocket so much since it tends to take a lot of abuse before I apply them.

My printer is buzzing away on the upper strong arm mount...

 

[jmasterj]

Last night I started work on the Zephyr kit from Apogee and learned how insane the shipping costs are for H motors. $60 bucks to ship a $50 motor to launch a $100 rocket.

If you have any interest in launching it multiple times, get a 38mm to 29mm adapter, an Aerotech 29/180 or 29/240 motor, and the USPS-shippable H motor of choice for those cases. From somewhere besides Apogee (Wildman, BuyRocketMotors.com, etc.). It'll cost you a bit more than that $110 outlay, but you'll be able to buy $30ish no HAZ motors for that case over and over again.

 

[bad_idea]

After my successes with the 9 cluster Falcon 9 Crew Dragon, I thought, "OK, I just need to strap three of these cores together like I did with the smaller scale version". NOT SO. This is more than 3X more difficult!

That you have thought this through and realized this is a sure sign you will conquer the difficulty though!

Two more things to think about:

1. Since this will be a HPR, the RSO at a launch will not want you to insert the igniters until you're on the pad and pointing up. So as you design Stage 0, think about how you're going to insert 27 igniters on the pad.
2. I would highly recommend planning to launch on a 10-10 rail and not a rod, whether you're incorporating the rail into your strongback or not. Any club launch should have a 10-10 rail available.

 

[boatgeek]

Last night I started work on the Zephyr kit from Apogee and learned how insane the shipping costs are for H motors. $60 bucks to ship a $50 motor to launch a $100 rocket.

Is there a vendor at your launch site? Then you just have to pay for the motor and not the shipping or hazmat. Also, buying several motors at once really helps because the shipping and hazmat charges stay roughly the same and are amortized over many motors. That's my excuse for buying a dozen or two at a time, anyway!

 

[jmasterj]

Is there a vendor at your launch site? Then you just have to pay for the motor and not the shipping or hazmat. Also, buying several motors at once really helps because the shipping and hazmat charges stay roughly the same and are amortized over many motors. That's my excuse for buying a dozen or two at a time, anyway!

Can't buy a bunch of HPR before you have a cert, though. That's what I do now that I've gotten my certs, though!

 

[Switch]

I'm hoping to pick up a motor from Bay Area Rocketry today. Mike has this awesome trailer with everything you could possibly need.

Yesterday I completed the lunch lugs


I took advantage of the lug to anchor the recovery chute for the second stage::


I also completed the strong back:

The photo above was taken before I realized I should reverse the direction of the bolts to make it easier to remove from the rocket on the launch rail.

This is with the bolts reversed; I'm using 1" nuts to make it easier to tighten and release by hand.

I still need to figure out how to support the weight of the rocket on the launch rail and attach the igniters.

 

[boatgeek]

When you get to the launch, you might check with the RSO to see if they will let you install the A motor igniters in the prep area and the big ones at the pad. That would save a bunch of time and they might go for it. There’s valid reasons why they might not too, but it’s worth a try.

 

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Here's the base I added to support the rocket on the pad and hold the screw binding posts.


I took a piece of steel plate bent it at a right angle and cut a circle out for the core motors. Each igniter will have its own circuit back to a relay. The circuit boards shown above ill be soldered to on half of one of a computer motherboard cable. I took one of these and cut it in half. Then I started soldering...



This way I will have an easy way to connect the rocket to the relays.

The relay build is on the thread I started when I was trying to figure out how to launch my 9 cluster Falcon 9.

 

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Today I was getting things ready for next week's launch when I realized I had loaded the boosters with E12-0 motors & realized they should have been D12-0 so they separate before MECO. That's when I realized I needed a pre-flight checklist.

Adapted from
https://www.rocketryforum.com/threads/pre-flight-checklists.43756/

Falcon Heavy Pre-Flight Checklist

1st stage
Make sure motor mount is secured with no loose parts.
Verify that all motors are new and not used
Verify continuity of igniters
Verify igniter plugs are properly sized
Confirm seating of thrust strut arms to boosters.
Tug on both ends of the shock cord or recovery harness. It should be firmly attached.
Examine recovery device. Shroud lines should be of equal length, firmly attached and not tangled.
Parachute or streamer must be firmly attached to recovery harness, nose cone and/or body tube.
Make sure fins are present and aligned properly.
Try to wiggle fins to make sure fillets do not have any cracks and fins are securely attached.
Make sure launch lugs are properly aligned and securely attached to rocket.
Make sure body tube is not kinked or warped.
Recovery system should be folded loosely.
Install recovery system into rocket.
Examine shock cord or recovery harness. There should be no dry rot, no frayed or burnt fibers.
Make sure shear pins, if used, are installed and properly sized for rocket size and charge size.
Make sure a properly sized motor for the rocket has been selected.
Install and secure motor in rocket.


2nd stage
Verify that all motors are new and not used
Check flip out fins & replace rubber bands
Make sure flameproof wadding is installed (Make sure baffles are clear of obstruction).
Make sure shear pins, if used, are installed and properly sized for rocket size and charge size.
Recovery system should be folded loosely.
Install recovery system into rocket.
Make sure a properly sized motor for the rocket has been selected.
Install and secure motor in rocket.



Recovery
Check screw eye or plastic loop on nose cone. It should be securely attached. Confirm parachute connections
Check eyebolts and/or quicklinks if present. They should be securely attached.
Inspect parachute for rips or tears
Landing legs deploy freely when released from magnetic shear pins


Launch rails
Are not lose

Toolbox
Spare rubber bands
Spare igniters
Spare motors
Spare fins
Spare machine screws


At the pad
Verify continuity
Secure rocket on launch rod (or rail) above blast deflector plate.

This is a work in progress.


Launch in less than 6 days

 

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SpaceX Falcon Heavy 1:65 scale test flight #1

Date: Aug 21, 2022
Location: Artesia Dry Lake, NV
Launch Status: FAIL (CATO)



Failure analysis: failure of right booster center D9 motor ignition.

 

[bguffer]

failure of D9 motor ignition or failure of D12 motor ignition?

 

[Switch]

failure of D9 motor ignition or failure of D12 motor ignition?

Typo D12 thanks for catching that.

 

[Sandy H.]

How much damage? Looked good for the first bit. Hopefully next flight is perfect!

Sandy.

 

[Switch]

How much damage? Looked good for the first bit. Hopefully next flight is perfect!

Sandy.

Most of the damage was to my pride. The Falcon Heavy suffered some broken parts. The bottom section of all three cores need to be replaced.





Some of the shields for the landing legs popped off.


Tabs on flip out fins on the second stage broke


It could have been worse. Thanks to my design of using the paper skins to hold everything together, I am able to replace the broken sections.

I'm working on the repairs now with the spring launch calendar in view.

 

[Switch]

I should have mentioned that the launch controller I used for this flight worked pretty well.

Each motor igniter was powered by a separate relay.




This was my "clip whip from hell" solution.



The launch controller worked with the club equipment just fine and I had continuity on every motor igniter prior to launch using the LEDs that I arranged geometrically on the launch controller box. Also, I modified the Strong Back to use a 3 foot section of 1" square launch rail, so I could more easily mount the rocket on the pad.

 

[hobie1dog]

thanks for all the pictures and the video

 

[burkefj]

Man that's a lot of complexity but I'm enjoying watching it come together.