Falcon 9 Crew Dragon Build 2.0 (1:65 Scale BT-70)

[Switch]

Here is my latest build of the Space X Crew Dragon that flew Bob Behnken and Doug Hurley to the International Space Station (ISS) on May 30, 2020. This was the first launch of United States astronauts to the ISS from a US launch vehicle since the Space Shuttle program was retired 11 years ago. You can view the historic SpaceX launch here:


As with my previous builds, the goals of this project are ambitious:

1. A 9 cluster, two stage model of the Falcon 9 Crew Dragon
   1. The 9 cluster 1st stage uses a relay box which you can check out here
   2. I plan to use the same rear ejection technique for first stage recovery and second stage ignition as I have used before
2. Working landing legs that extend for (an attempt at) upright recovery of the 1st stage
   1. This is triggered by rear ejection as on my previous Falcon9.
3. Printable “skins” for added scale rocket detail
   1. On my most recent Falcon Heavy project, a significant amount of effort was spent on painting and wet sanding. This project uses printed paper “skins” instead of painted parts
   2. The skins are adapted from AMX Paper Scale Models.
4. Snap-in parts and add-on parts to integrate with the “skins” for the finished project
   1. To simplify the application of printable skins, parts that extend from the rocket body tube are printed separately and snap into holes that are pre cut into the body tube parts.
5. No glue™, so parts can be replaced as needed
   1. Tube parts are fabricated to fit together using friction or, as mentioned below, parts are designed to snap into place. Also as mentioned below, paper adhesive “skins” are used to wrap the body tube parts to hold them together
   2. OK, I'm still using glue in a few places.
6. Hidden “flip out” fins for the second stage based on Tim's design at Apogee Rockets
7. Magnetic shear pins for core motor retention, landing leg release, and capsule retention/release
8. Movable grid fins
9. Separate recovery of the Crew Dragon capsule
10. 1:65 scale so BT-70 tubes can be used for the rocket body.
    1. My first Falcon 9 Dragon was done with BT-60 tubes at 1:90 scale, too small or more than one modle rocket motor.
    2. BT-70 tubes allow for a 9 cluster model Falcon 9 rocket
    3. So this scale makes a 3 core, 27 cluster model Falcon Heavy possible.

The 3D printing was done on a Prusa i3 MK3s 3D printer and all of the designs were created using FreeCAD software.

Here's the finished build (Height: 102 cm/ 40"):



The rocket has nine engines (just like the real Falcon 9):

That's 8 A10-OT engines surrounding a center E12-0.

Here's the CAD drawing of the motor mount:

Here is more information about my attempts to do a 9 cluster rocket.

The fins are integrated into the landing legs:


The landing legs flip out when the 1st stage motor ejects during reverse recovery. Here you can see the magnetic sheer pins at end of the landing legs. In the upright position, each magnet is paired with a magnet in the motor core, so when the core ejects, the legs are released. This also holds the core motor in place prior to launch.
When the motor core is ejected, the recovery chute deploys and it is attached to the top of the 1st stage for (an attempt at) upright landing:

In my previous 1:90 scale Falcon 9, I had to use aluminum tubes for the landing leg supports. Here, the telescoping tubes are 3D printed, which greatly simplified the work for the landing legs.

The grid fins extend (but are not activated during landing - coming soon!):




Note: this is the part of this build that is totally new!

Instead of printing the top of the 1st stage with grid fin mounts, LOX & LH2 Fuel lines as one piece, each part is printed separately. The top of the 1st stage has holes for the grid fin mounts, and LOX & LH2 Fuel lines (plus hidden round holes hidden by the grid finds for the ejection exhaust). The grid fin mounts, and LOX & LH2 Fuel lines are printed with tabs that fit into these holes. The AMX paper rocket skins are applied over this 3D printed part and the adjoining BT-70 tube and also cover these holes. This makes application of the skins very simple since there are no parts protruding from the 3D printed tube. The skins also function as the "glue" that holds the 3D printed parts to the BT-70 tubes. After the skins are applied, the holes need to be cut through the paper skin to allow the parts to snap into place.


Here's the outside of the top LOX Line housing:


On the inside you can see the tab that allows it to snap into the first stage section above:


This is the grid fin mount that snaps into the square holes in the first stage shown above.


Here's the grid fin the snaps over the grid fin mount shown above:


The second stage features flip out fins:


The Crew Dragon capsule is recovered separately from the 2nd stage:


It's held to the 2nd stage with small magnets:


It can be opened for the astronauts or other payloads. Small magnets attach the two parts together.








Some parts, such as the camera on a lower section of the LOX fuel line are glued on to the outside of the paper skins:



And here is my 2nd failed launch attempt


That's 6 of the A10-OT engines igniting without the center E12-0 Engine and hence the belly flop. Note that the aerodynamics are sound as the rocket attempts to right itself as it falls...

That hard landing broke two of the landing legs, but more important was a fracture in the main engine assembly.

That's all fixed now and I'm looking forward to the next SARG launch event to see that happens next!

 

[Sandy H.]

Here is my latest build of the Space X Crew Dragon that flew Bob Behnken and Doug Hurley to the International Space Station (ISS) on May 30, 2020. This was the first launch of United States astronauts to the ISS from a US launch vehicle since the Space Shuttle program was retired 11 years ago. You can view the historic SpaceX launch here. My first Falcon 9 Dragon was done with BT-60 tubes at 1:90 scale.

As with my previous builds the goals of this project are ambitious:

1. A 9 cluster, two stage model of the Falcon 9 Crew Dragon
   1. The 9 cluster engine uses a relay box which you can check out here
   2. I plan to use the same rear ejection technique for first stage recovery and second stage ignition as I have used before.
2. Working landing legs that extend for (an attempt at) upright recovery of the 1st stage
   1. This is triggered by rear ejection as on my previous Falcon9.
3. Printable “skins” for added scale rocket detail
   1. On my most recent Falcon Heavy project, a significant amount of effort was spent on painting and wet sanding. This project uses printed paper “skins” instead of painted parts
   2. The skins are adapted from AMX Paper Scale Models.
4. Snap-in parts and add-on parts to integrate with the “skins” for the finished project
   1. To simplify the application of printable skins, parts that extend from the rocket body tube are printed separately and snap into holes that are pre cut into the body tube parts.
5. No glue™, so parts can be replaced as needed
   1. Tube parts are fabricated to fit together using friction or, as mentioned below, parts are designed to snap into place. Also as mentioned below, paper adhesive “skins” are used to wrap the body tube parts to hold them together
   2. OK, I'm still using glue in a few places.
6. Hidden “flip out” fins for the second stage based on Tim's design at Apogee Rockets
7. Magnetic shear pins for core motor retention, landing leg release, and capsule retention/release
8. Movable grid fins
9. Separate recovery of the Crew Dragon capsule
10. 1:65th Scale so BT-70 tubes can be used for the rocket body.

Here's the finished build (Height: 102 cm/ 40"):

The rocket has nine engines (just like the real Falcon 9):

Here's the CAD d drawing of the motor mount:

Here is more information about my attempts to do a 9 cluster rocket.

The fins are integrated into the landing legs:

The landing legs flip out when the 1st stage motor ejects during reverse recovery. And the recovery chute is attached to the top of the 1st stage for (an attempt at) upright landing:

In my previous 1:90 scale Falcon 9, I had to use aluminum tubes for the landing leg supports. Here, the telescoping tubes are 3D printed, which greatly simplified the work for the landing legs.

The grid fins extend (but are not activated during landing - coming soon!):

Note: this is the part of this build that is totally new!

The top of the 1st stage has holes for the Grid Fin mounts, and LOX & LH2 Fuel lines (plus hidden round holes hidden by the grid finds for the ejection exhaust). The AMX paper rocket skins are applied over the tube and cover these holes. The skins also function as the "glue" that holds the 3D printed parts to the BT-70 tubes. After the skins are applied, the holes need to be cut through the paper skin to allow the parts to snap into place.

Here's the outside of the top LOX Line housing:

On the inside you can see the tab that allows it to snap into the first stage section above:

This is the grid fin mount that snaps into the square holes in the first stage shown above.

Here's the grid fin the snaps over the grid fin mount shown above:

The second stage features flip out fins:

The Crew Dragon capsule is recovered separately from the 2nd stage:

It's held to the 2nd stage with small magnets:

It can be opened for the astronauts or other payloads. Small magnets attach the two parts together.

Some parts, such as the camera on a lower section of the LOX fuel line are glued on to the outside of the paper skins:

And here is my 2nd failed launch attempt


That's 6 of the A10-OT engines igniting without the center E12-0 Engines and hence the belly flop.

That hard landing broke two of the landing legs, but more important was a fracture in the main engine assembly.

That's all fixed now and I'm looking forward to the next SARG launch event to see that happens next.

Umm. Wow. I'm going to have to look for your previous build, as I don't recall seeing it and this one is amazing.

I hope your next launch is successful and you figure out how to get it signed by the astronauts, as your build is obviously showing great effort to model a pivotal experience in space travel and I bet they would like it.

Awesome!

Sandy.

 

[manixFan]

Wow, very cool build! Lots of great synthesis getting it all to come together. I couldn’t watch the rest of the video, too painful to see such a neat model take a hard landing.

I hope you get a good way figured out on getting all the motors lit, it will be a show stopper for sure. Maybe a flash pan if you can protect the plastic parts.

Keep us posted!

Tony

 

[Sooner Boomer]

That's a hoot! Too bad I only have one LIKE!

 

[Switch]

Well, here it is on the pad at Gibson Ranch Regional Park



The launch was a partial success: all 9 motors in the 1st stage ignited, the second stage motor ignited, 1st stage recovery worked, the capsule recovery worked, but the 2nd stage flip out fins and recovery failed.


The failure of the flip out fins was because the force of the 1st stage ejection charge pushed the motor assembly up into the 2nd stage body tube. I had this problem on my first Falcon 9 and thought I had resolved it by adding a ring that was the outside diameter of the body tube. But in this case, I had already printed and assembled the 2nd stage motor & flip out fin assembly, so the ring was printed and glued on separately. Well, the glue failed. Fortunately, I only need to reprint that one part, and it will be ready to fly again.

I don't know why the chute did not eject, perhaps it was not packed carefully enough.


Special thanks to SARG for making this flight possible!

 

[Switch]

On March 4th I had another chance to fly the Falcon 9. This launch was hosted by LUNAR at their beautiful Snow Ranch site.

I didn't realize my launch was up so I almost missed it entirely. I didn't see it go up, but I certainly saw it come down, nose down. And at first I thought "boy I feel bad for that guy" then I noticed the my capsule floating by...

So yeah, it didn't go well. The things that worked were the 9 cluster ignition, ignition of the second stage, and deployment of the Crew Dracon capsule.

The rear ejection worked partially. The string that runs from the motor tube to the top of the 1st stage on the outside was loose and slid under the motor at take off and burned in half. So the motor tube shot out and left the 1st stage without a parachute. I've redesigned the external recovery line attachment to the booster to prevent this from occurring again.

Second stage recovery also failed tragically with the ejection charge burning the parachute string. Lesson learned: use more wadding & a thicker string for the parachute.

The 1stage came down ballistically destroying the BT-70 tube at the top of the 1stage. I think it worked like a crumple zone in a car & prevented more damage. The stress of the crash also tore the paper skin at the coupler between the first two BT-70 tubes, so that skin needed to be replaced as well.

The second stage, benefitting from achieving a greater altitude was completely totaled except for the Crew Dragon trunk module, which is plastic. The flip out fin/motor mount was also ruined but the fins survived.

I thought I had pictures of the wreckage but I can't find them.

I've been busy on other projects so just tonight turned to the task to repairing the Falcon 9. Tonight my efforts to avoid using glue really paid off. I was able to snap off the grid fin mounts, and remove the adhesive paper skins with a heat gun. All of the BT-70 tubes easily slid off the press-fit couplers.

Here is the top of the 1st stage before I had removed the skin with the NASA logo. The very top BT-70 was in shreds & here the replacement is being fitted.


In the bottom of this photo, you can see the shear in the skin at the location of the 1st coupler. You can also see the compression stress in the skin just above the NASA logo where the 2nd BT-70 tube joins the 3D printed section with the holes for the grid fin mounts.

Parts disassembled:


Time to print more skins:

and apply carefully from the middle to the edges on both sides:


Skin applied:


Rebuilt 2nd stage flip out fins and BT-70 tube:



The repairs took about an hour but I only needed to replace 2 BT-70 tubes, the 2nd stage flip out fin/motor mount, and apply new skins.

This rocket is starting to look like it has flown a couple of times.

 

[Switch]

Here is the Falcon 9 at Artesia Dry Lake on 05/21/23


close up of clip whip:



Shortly after ignition, it suffered a catastrophic failure of the E12-0 motor:





Here is my breakdown of events:
about 1/3 of a second into the launch there is an audible pop and ejection of the E12-0 motor nozzle:

The explosion forced the motor tube upward, releasing the landing legs. You can see they have started to extend in the photo above.

The explosion also severed the 9 motor cluster mount from the motor tube at the top of the E12-0 motor. Ejecting 9 motor cluster mount and motors from the rocket:

The landing legs extend completely - with their fins now lowered into the flames of the explosion.

The A10 motors continue to fire so the 9 motor cluster mount (left arrow) continues upward and was recovered behind the parking area. The explosion forced the motor tube upwards into the 2nd stage motor/flip out fin assembly, causing the 2nd stage to separate (lower right arrow) without ignition of the 2nd stage.

Fortunately, the Crew Dragon Launch Escape System was activated (upper right arrow).


And the Crew Dragon recovery worked!


So while the Falcon 9 first stage was completely destroyed, no lives were lost and a terrible tragedy was avoided.



Special thanks to Wayne, Ron, and Jennifer from Rocketry Organization of Northern Nevada for making this launch possible.

 

[waltr]

Oh NO.
The first photo is of a great looking rocket and the clear fins are invisible.

Then the CATO.....I do not fly BP E's due to the number I have seen CATO.
Good photo sequence highlighting the event.
Nice the Crew escape system worked.

 

[Switch]

Oh NO.
The first photo is of a great looking rocket and the clear fins are invisible.

Then the CATO.....I do not fly BP E's due to the number I have seen CATO.
Good photo sequence highlighting the event.
Nice the Crew escape system worked.

Wayne said the same thing about BP E motors and his daughter (Jennifer) suggested using an F motor instead. I forget what make she suggested. But that it could be fitted to my E motor mounts. I need to add that to my "lessons learned" list.

 

[Switch]

So here's the post mortem on the E12-0 disaster:

The nine motor cluster mount broke about 3cm from the motor stop of the E12-0. Those holes I added to reduce weight also reduce strength and I'm going to remove them, but I don't think it would have made much of a difference.

This motor mount can in fact be reused. I just need to print a longer transition from the E12-0 motor to the BT-20 tube that carries the ejection charged to the second stage.

Also, on a positive note: all 9 motors ignited. But you can see how the E12-0 completely blew out.


And the plugs in the tops of the A10-0T motors held.


This is the BT-20 tube above the 9 motor cluster mount. That's the shock cord for recovery and the shattered centering ring for the shear magnets that hold the landing legs in place.


Here I've stretched the motor tube back out so you can see the amount of compression it absorbed.


The centering ring for the shear magnets that retain the landing legs was shattered. So it is no wonder that the landing legs deployed.


For comparison, this is what it used to look like:


Meanwhile, the 2nd stage did not ignite and suffered no damage.


But the 1st stage was damaged extensively. The lower 3D printed section melted, the BT-70 tube crumpled, and the landing legs and fins dropped into the fireball emanating from the bottom of the rocket.


But the LOX and LH2 lines, landing leg telescoping tubes, and metal screws and magnets all survived.

The interstage section was also undamaged & although a few pieces popped out, they were recovered on site.


The recovery chute had some minor pock marks but is reusable.


in part saved by the retainer tubes I've been developing:


The motor tube top centering ring was also destroyed


As were two of the landing legs:


I've already made some improvements in the landing legs to strengthen the weak point where the screw mount is located. I've also improved the way the fins mount in the landing legs. So I reprinted all 4.

That's it for now. Time to rebuild...

 

[waltr]

Good luck with the re-build and better next launch.

 

[BigMacDaddy]

This is an amazing journey of design and persistence. I am curious about why you do not used plugged engines for the A10s (i.e., the ones made for Estes race cars).

FWIW - I designed a 3D printed cluster mount that might be appealing / interesting to you. You obviously have the design skills to do this type of thing (or something better) yourself but maybe that design will inspire a different / easier design for your motor retainers. I have not tested this with a fully loaded cluster but think that the 3D printed parts in ABS will hold up. This picture just shows the loaded canister but below I have exploded the cluster and shown the mounting parts.

.

The idea is to do a quarter turn twist to lock cluster canister that can be fully loaded up outside the rocket. This requires that the top portion of cluster mount can also rotate so I use a thrust ring mounted inside the airframe and a large block across the whole top of the cluster. In the picture below the yellow parts are mounted to the airframe (or in my case were printed into the shell of a Little Joe II). I designed this to use the central 18mm engine for ejection so the mini engines are isolated from the top section of the airframe (I expected to use plugged engines but left the holes in the top in case someone wanted to use A10-0 and just load 3 instead of 6 so the other holes could exhaust the burn through. This also uses canted motors w/ an 18mm central motor but you could do the same with a 24mm in center and straight mini engines.

 

[Switch]

This is an amazing journey of design and persistence. I am curious about why you do not used plugged engines for the A10s (i.e., the ones made for Estes race cars).

FWIW - I designed a 3D printed cluster mount that might be appealing / interesting to you. You obviously have the design skills to do this type of thing (or something better) yourself but maybe that design will inspire a different / easier design for your motor retainers. I have not tested this with a fully loaded cluster but think that the 3D printed parts in ABS will hold up. This picture just shows the loaded canister but below I have exploded the cluster and shown the mounting parts.

View attachment 523842.

The idea is to do a quarter turn twist to lock cluster canister that can be fully loaded up outside the rocket. This requires that the top portion of cluster mount can also rotate so I use a thrust ring mounted inside the airframe and a large block across the whole top of the cluster. In the picture below the yellow parts are mounted to the airframe (or in my case were printed into the shell of a Little Joe II). I designed this to use the central 18mm engine for ejection so the mini engines are isolated from the top section of the airframe (I expected to use plugged engines but left the holes in the top in case someone wanted to use A10-0 and just load 3 instead of 6 so the other holes could exhaust the burn through. This also uses canted motors w/ an 18mm central motor but you could do the same with a 24mm in center and straight mini engines.

View attachment 523843

I really like your design & the idea of a locking mechanism. I only used the A10-0T because that is what I could source at the time. I've love to model the nozzles like you have, but I think they would melt unless the end of the A10 motor was flush with the bottom of the nozzle. So maybe the twist/lock could create side compression to hold the motors in place.

As for my Falcon 9, I've redesigned and reinforced all of the parts that broke and it is ready to be put back together. I'm hoping to launch again at ROCKONN in July. The 1:65 scale Falcon Heavy is also ready to fly, so it should be an interesting day.

 

[BigMacDaddy]

I really like your design & the idea of a locking mechanism. I only used the A10-0T because that is what I could source at the time. I've love to model the nozzles like you have, but I think they would melt unless the end of the A10 motor was flush with the bottom of the nozzle. So maybe the twist/lock could create side compression to hold the motors in place.

As for my Falcon 9, I've redesigned and reinforced all of the parts that broke and it is ready to be put back together. I'm hoping to launch again at ROCKONN in July. The 1:65 scale Falcon Heavy is also ready to fly, so it should be an interesting day.

Thanks - I have printed a bunch of engine retainers from ABS and have not had issues with melting (although I have not tested with clusters).

Best example of the impact of mini engine is on my X-3 Stiletto where engine was directly against a partial ABS tube. Did not really melt but did definitely blacken.



I also have used ABS to print D to E adapters that take the brunt of the ejection charge for a D12 engine. Also no real melting.



Both of those results are after a single launch so TIFWIW.

 

[Alan15578]

So, no emergency crew escape system?

 

[Switch]

Sounds like I need to switch to ABS!

 

[Switch]

Repairs almost complete:
Countdown

 

[Switch]

Repairs almost complete:
Countdown
View attachment 532467

Well, here I am again. Another launch with mixed results. And another chance to recycle parts from another totaled Falcon 9. It is going to take me a few days to process the wreckage but this is a SpaceX project. So it's all about learning from failure...
again and again...

Falcon 9 flight on YouTube ouTube

Preliminary thoughts:
1: I'm really proud of that lift off. The flight is straight and powerful. All 9 motors ignited. I've had no issues with 9 cluster ignition in the last 4 launches. So I consider that problem solved.
2: There is a bit of a spin as the rocket ascends and I think that led to the fins (which are secured only by friction, snapped into the landing legs) to shear off from the side ways force. This was the first time I have experimented with not gluing the fins in place. I think the real problem is the thickness of the fin plastic which always felt flimsy. I think I'm on the right track with the snap-in design, but just need to tighten the fit and maybe use a thicker gauge plastic.
3: The long, slow descent before the 2nd stage ignites. Well, that is me fitting the E12 retainer clip with an E12-6 motor and never taking it out again and using the E12-0 that I should have used. Yeah, that's operator error. And not the first time I've had issues with installing the wrong motor. Probably the most embarrassing thing about this flight. But by complete luck, we get to see the 2nd stage events up close, which would not had been possible with the E12-0 motor that I should have used.
4: But we can see that the second stage ignition worked! But damn what a hot mess. I've never seen it so up close. And yeah, it would have been better if the 2ns stage ignition occurred 6 seconds earlier. Before apogee.
5: But then there is the complete failure of the reverse recovery ejection of the motor tube. I'm not sure what happened here. I never intended the motor to slowly burn for 6 seconds before the ejection charge. My previous builds of this rocket have required lots of tuning of the fitment of the motor tube within the rocket body, to eliminate sticking points. I don't think that 6 second ejection charge delay helped any of that. I think my next build needs to have better clearance for motor tube ejection and 2nd stage release. Everything is fitting to tight and takes considerable time to sand and file so that pieces slide freely.

Such are my thoughts a day after my last failed attempt a flying the Falcon 9. I didn't even try to fly my Falcon Heavy, since there were so many problems revealed with the Falcon 9 flight. Also the day was running late and it was getting damned hot out there on the Nevada Dessert floor. My Apogee Zephyr flew like a champ with an H130 Aerotech motor. So my Level 1 cert wasn't a fluke and I at least got to put my 2nd high power flight into my log book...

As before, a special thanks to Wayne, Ron, Jennifer from RockONN
for making this failure possible.

 

[Switch]

Tonight I did a post mortem on the failure of the fins. We saw in the last launch that they came out several seconds after ignition.

I recovered three fins. Each deferred slightly as was experimenting with the design of the tabs that secured them to the landing legs.


In the photo above, only the bottom fin stayed attached. so I was on the right track (mostly)

But what they all had in common was a tapered fit. The front is well inside the landing leg but the rear is barley inserted. Bench testing showed that the fin would pry out from the rear under side loads.

Here is the best fin fitment from the last launch. Notice how the fin is fully inserted on the left but barely inserted on the right. The fitment is tapered, making it easy to pry out from the bottom of the landing leg (right).


My solution is to redesign the fin flange. Rather than a flimsy hook at the front and passive friction at the rear, I made the entire flange deeper.


In the above photo: the top is the new design and the bottom is the old design.


Now the entire flange is fully inserted into the landing leg slot instead of being tapered.


Now I can tac-weld the fin into place with a soldering iron or use super glue or hot glue or rely on friction. My inclination is to stick with friction as when I side load the fin is no longer pry's out from the back.

 

[Hobie1dog]

Thanks for all the photos

 

[Switch]

Last Saturday was the first opportunity to fly the Falcon 9's again.
Unfortunately my efforts to improve fin attachment and first stage reverse recovery were inadequate and several problems persisted in the latest flight. Fins detached and the motor tube did not completely eject from the first stage. I've concluded that their is not enough pressure from the ejection charge to force the entire motor tube (which is almost the length of the first stage) to eject. Accordingly, I'm working on a redesign of the first stage motor tube.



I did not bring my own battery and relay box to the club launch and learned that the club configuration did not deliver enough amperage to light all 9 igniters. So I improvised with some quick fuse the the A10-OT motors.

That worked remarkably well with only one A10 motor not igniting. Note in the photo above. The reason that motor did not ignite is that the fuse fell out.









Fortunately for Bob and Doug, the Crew Dragon emergency ejection sequence worked.

 

[CoolRockets]

Here is my latest build of the Space X Crew Dragon that flew Bob Behnken and Doug Hurley to the International Space Station (ISS) on May 30, 2020. This was the first launch of United States astronauts to the ISS from a US launch vehicle since the Space Shuttle program was retired 11 years ago. You can view the historic SpaceX launch here:


As with my previous builds, the goals of this project are ambitious:

1. A 9 cluster, two stage model of the Falcon 9 Crew Dragon
   1. The 9 cluster 1st stage uses a relay box which you can check out here
   2. I plan to use the same rear ejection technique for first stage recovery and second stage ignition as I have used before
2. Working landing legs that extend for (an attempt at) upright recovery of the 1st stage
   1. This is triggered by rear ejection as on my previous Falcon9.
3. Printable “skins” for added scale rocket detail
   1. On my most recent Falcon Heavy project, a significant amount of effort was spent on painting and wet sanding. This project uses printed paper “skins” instead of painted parts
   2. The skins are adapted from AMX Paper Scale Models.
4. Snap-in parts and add-on parts to integrate with the “skins” for the finished project
   1. To simplify the application of printable skins, parts that extend from the rocket body tube are printed separately and snap into holes that are pre cut into the body tube parts.
5. No glue™, so parts can be replaced as needed
   1. Tube parts are fabricated to fit together using friction or, as mentioned below, parts are designed to snap into place. Also as mentioned below, paper adhesive “skins” are used to wrap the body tube parts to hold them together
   2. OK, I'm still using glue in a few places.
6. Hidden “flip out” fins for the second stage based on Tim's design at Apogee Rockets
7. Magnetic shear pins for core motor retention, landing leg release, and capsule retention/release
8. Movable grid fins
9. Separate recovery of the Crew Dragon capsule
10. 1:65 scale so BT-70 tubes can be used for the rocket body.
    1. My first Falcon 9 Dragon was done with BT-60 tubes at 1:90 scale, too small or more than one modle rocket motor.
    2. BT-70 tubes allow for a 9 cluster model Falcon 9 rocket
    3. So this scale makes a 3 core, 27 cluster model Falcon Heavy possible.

The 3D printing was done on a Prusa i3 MK3s 3D printer and all of the designs were created using FreeCAD software.

Here's the finished build (Height: 102 cm/ 40"):
View attachment 555283


The rocket has nine engines (just like the real Falcon 9):
View attachment 555284
That's 8 A10-OT engines surrounding a center E12-0.

Here's the CAD drawing of the motor mount:
View attachment 555285
Here is more information about my attempts to do a 9 cluster rocket.

The fins are integrated into the landing legs:
View attachment 555286

The landing legs flip out when the 1st stage motor ejects during reverse recovery. Here you can see the magnetic sheer pins at end of the landing legs. In the upright position, each magnet is paired with a magnet in the motor core, so when the core ejects, the legs are released. This also holds the core motor in place prior to launch.
When the motor core is ejected, the recovery chute deploys and it is attached to the top of the 1st stage for (an attempt at) upright landing:
View attachment 555287
In my previous 1:90 scale Falcon 9, I had to use aluminum tubes for the landing leg supports. Here, the telescoping tubes are 3D printed, which greatly simplified the work for the landing legs.

The grid fins extend (but are not activated during landing - coming soon!):
View attachment 555288



Note: this is the part of this build that is totally new!

Instead of printing the top of the 1st stage with grid fin mounts, LOX & LH2 Fuel lines as one piece, each part is printed separately. The top of the 1st stage has holes for the grid fin mounts, and LOX & LH2 Fuel lines (plus hidden round holes hidden by the grid finds for the ejection exhaust). The grid fin mounts, and LOX & LH2 Fuel lines are printed with tabs that fit into these holes. The AMX paper rocket skins are applied over this 3D printed part and the adjoining BT-70 tube and also cover these holes. This makes application of the skins very simple since there are no parts protruding from the 3D printed tube. The skins also function as the "glue" that holds the 3D printed parts to the BT-70 tubes. After the skins are applied, the holes need to be cut through the paper skin to allow the parts to snap into place.
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Here's the outside of the top LOX Line housing:
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On the inside you can see the tab that allows it to snap into the first stage section above:
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This is the grid fin mount that snaps into the square holes in the first stage shown above.
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Here's the grid fin the snaps over the grid fin mount shown above:
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The second stage features flip out fins:
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The Crew Dragon capsule is recovered separately from the 2nd stage:
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It's held to the 2nd stage with small magnets:
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It can be opened for the astronauts or other payloads. Small magnets attach the two parts together.
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Some parts, such as the camera on a lower section of the LOX fuel line are glued on to the outside of the paper skins:
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And here is my 2nd failed launch attempt


That's 6 of the A10-OT engines igniting without the center E12-0 Engine and hence the belly flop. Note that the aerodynamics are sound as the rocket attempts to right itself as it falls...

That hard landing broke two of the landing legs, but more important was a fracture in the main engine assembly.

That's all fixed now and I'm looking forward to the next SARG launch event to see that happens next!

This gets the CoolRockets stamp of approval

 

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A second flight of my other Falcon 9 reproduced the same successes and failures of the first flight, but second stage ignition also failed leading to a total loss of the Crew Dragon trunk which shattered on impact while the rest of the second stage can be reused.



All 9 motors ignited with an improved fuse configuration. I think I may adopt this technique on my Falcon Heavy...

 

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Well, if a picture is worth a thousand words, here are 13,000 words...

 

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We got another chance to fly the Falcon 9 last week. With mixed but exciting results. All thee flights confirmed that using a single igniter with a network of quick fuse reliably ignited all 9 motors in the cluster. This significantly simplifies first stage ignition because only on igniter is required instead of nine. Second stage ignition was successful in all flights and static tests! Even when the BT20 motor tube was drastically reduced in length.


The solution to reliable 9 cluster ignition was the use of quick fuse between the 8 motors surrounding the E12-0 core.


One problem from previous launches has been unreliable ejection of the 1st stage motor core for recovery. The problem appeared to be the top centering ring of the motor which needed to travel about 56cm to fully eject from the 1st stage body tube. I test three solutions to this problem; all of which involved shortening the length of motor tube that needed to be ejected:
1: Shorten the length of the BT-20 motor tube by 2/3 and eliminate the top centering ring.
2: Keep the full length of the BT-20 tube as before, but split into two pieces: one 45.7cm part permanently mounted to carry the ejection gas up the center of the rocket to the 2nd stage and the other part ejecting with the motor.
3: Shorten the the BT-20 motor tube to just the length required to secure the landing legs with magnetic sheer pins. Same as option two without the extra BT-20 tube.

Option 1 also note the addition of the 3D printed sleeve between the motor assembly and the magnetic sheer pin ring. This area was prone to bending on previous test flights and the tape tended to peel a layer of paper off the cardboard tube when serviced.


Option 2 and 3



Each of the Falcon 9 rockets I flew that day had one of these configurations. But I started with a static test of option 3, since that appeared to be the least likely to work:

SpaceX Falcon 9 Crew Dragon 1:65 Scale: Static Test #1


Although the test stand tipped over, the test was successful since the objective was to ignite the 2nd stage using the new (shorter) 1st stage motor design.

Here's what worked and what didn't on the next three flights:

SpaceX Falcon 9 Crew Dragon 1:65 Scale: Flight #10


A failure of the magnetic sheer pins to secure the landing legs in flight led to premature landing leg deployment. The fins show evidence of exposure to the 1st stage exhaust and prevented the motor from ejecting properly. I believe the cause of the premature landing leg deployment deployment was the undersized centering ring used for the magnetic sheer pins on the motor mount. This may have caused the magnets on the centering ring to pull away from the landing leg and reduce the force of that magnets. On flights #11 and #12, I taped the landing legs in place to prevent this from happening.


Although the 2nd stage motor ignited, the flip out fin section unexpectedly separated from the body tube due to insufficient friction between the two parts. This was a known problem but the first time the flip out fin part completely separated. I now realize this is a feature and not a bug and I'm planning to use this for parachute recovery.


Ejection of the recovery chute from the top part of the 2nd stage failed because most of the force of the ejection charge ejected the flip out fins instead. Going forward I will only put the Crew Dragon recovery chute in the 2nd stage trunk module and put the 2nd stage recovery chute in the main body tube and use reverse recovery as mentioned above.


The Crew Dragon Capsule ejected properly:



SpaceX Falcon 9 Crew Dragon 1:65 Scale: Flight #11


After a successful ignition of all 9 motors in the first stage, the second stage ignites, and the Crew Drago ejects. The the parachute recovery of both the first and second stages work. The only flaw in this flight was a tail fin that separated before MECO. While my goal is to have a replaceable fins, I used super glue to secure the fins to the landing legs for these test flights. But it appears that I forgot to glue one fin.

SpaceX Falcon 9 Crew Dragon 1:65 Scale: Flight #12


After a successful ignition of all 9 motors in the first stage, the second stage ignites, and the Crew Dragon ejects but the parachute recovery of both the first and second stage failed.

The magnetic shear pins for the Crew Dragon capsule are in a ring at the top of the Trunk. That ring interferes with ejection of the two 12" parachutes in the trunk. As mentioned above, I think the fix for the second stage recovery is to move the chute to the main body tube and use reverse recovery of the flip out fin module.



As best that I can tell, the failure to eject the motor from the 1st stage was because the chute got trapped between the centering ring that holds the magnetic sheer pins that secure the landing legs. That centering ring was intentionally designed to be 2mm smaller than the BT-70 tube to assure that it did not catch on the coupler between the cardboard tube and the 3D printed part.

Another variation in the design of the 1st stage was tested using these flights. To address my concerns about the coupler between the 3D printed bottom part and the cardboard BT-70 tube, I lengthened the height of the 3D printed part. The shortest part was from previous flights. A new longer part completely contains the centering rings of the motor tube but still requires gluing on the Landing Leg Shrouds. In both of these designs one 18" BT-70 tube is not long enough to achieve the scale height of the Falcon 9 so an additional section of BT-70 tube is added at the top of the 1st stage with a coupler. Then I realized that if I make the bottom 3D section long enough to included the Landing Leg Shrouds, I only need the one 18" BT-70 tube to achieve the correct 1st stage length.



Test Flight #10 also tested using a BT-70 for the entire 1st stage.



So with these lessons learned I am rebuilding these Falcon 9s for another trip out to Nevada. A surprising amount of the parts from these test flights were salvageable, mostly I just needed to replace the bottom sections on the 1st stage and some burned up fins. Oh, and completely rebuild a flip out fin module.

Changes for the next test flights include:
1: Larger centering ring for the landing leg sheer pins part.
2: New longer bottom 3D section.
3: Improve 1st stage recovery packing (somehow).
4: Relocated 2nd stage recovery chute to main body chamber & use reverse recovery for the flip out fin module.
5: New launch rail tripod that uses 1.25" PVC pipe fittings (8' launch rail not shown)


6: And maybe launch the Falcon Heavy too.

 

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It finally worked!

This is the 22nd flight of my scratch built SpaceX Falcon 9 Crew Dragon Build. This launch was at the ROCKONN club launch on 10/21/2023 http://www.rockonn.org/team.html.

This flight was a complete success. All 9 motors in the first stage and the single motor in the second stage all ignited. Recovery of the first stage motor, first stage body, second stage body, and Crew Dragon all worked!






I had four more flights that day and they all failed with issues in the 2nd stage due to a recent change I had made to the way I housed the recovery chutes. And I had some parachute chords break on 1st stage recovery. But everything else in the first stage worked on all of those flights. So I'm really optimistic about being able to reuse this Falcon 9 Crew Dragon for multiple missions to the ISS.

And a special thanks to Wayne, Ron, Jennifer from RockONN
for making this success possible!

 

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Congrats! From the beginning, you've dreamed big. Delighted it's all come together for you.

 

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Fun times at the LUNAR launch today.




Fins (almost) invisible:


Flip out fins in action:



Here the 2nd stage has ignited and recovery of the 1st stage worked.


This is a static test of a refined 2nd stage recovery that still needs some work. The Crew Dragon ejected but not the2nd stage recovery chute. In this case the A8-3 retainer clip failed causing the motor to eject

 

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I got two more opportunities to fly the Falcon 9s last weekend:

Location: Brigantino Park
Hollister, CA
Club: LUNAR

The 1st launch worked perfectly: all motors ignited with successful recovery of 1st and second stages. That was also the 1st time I tried a C6 motor & it was really nice to see how far the 2nd stage can fly!

The 2nd launch was as if the ejection charge did not happen (but later inspection showed the center E12-0 motor burned all the way through). The 2nd stage ejected but did not ignite and came down nose first while the 1st stage came down exactly backwards. Neither first or second stage was damaged in any way. Who needs recovery, go figure... Also 8 of 9 motors ignited in the 1st stage. I'm wondering if that is a piece of fuse flying off to the left in the photo below. Next launch, I'm going to use quick-dip to secure the ends of the fuses in the A10-PT motors.

 

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Date: 03/09/2023
Location: Snow Ranch
Event: LUNAR Club Launch
Photo credits: Rob Heil

Two more flights of the Falcon 9 Crew Dragon. The 1st was an attempt to change the recovery of the 1st stage to one 24" parachute instead of two 18" chutes. The reverse recovery failed but the rocket was not damaged. The second flight was a complete success. Both flights had all 9 motors ignite in the 1st stage and successful 2nd stage ignition.




Crew Dragon Capsule recovery.