ULA Parker Solar Probe BT-70

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I've started working on a new build at 1/88th scale of the ULA Delta IV that launched the Parker Solar Probe on August 12th, 2018. You can watch the Parker Solar Probe launch here. The Parker Solar Probe is now the fastest human made object ever. This will be a three cluster three stage model rocket.

Here are a couple of cool videos related to this project:




As with my last project the goals of this build are ambitious:

1: 1/88th Scale so BT-70 tubes can be used for the body
2: A working thee cluster rocket with booster separation
3: Hidden fins for the second sage based on Tim's design at Apogee Rockets
4: A working third stage for the Parker Solar Probe
5: No glue, so parts can be replace as needed.

I'm going to use a modified version of my Falcon Heavy to create the Delta IV using the same magnetic booster attachment/separation and rear ejection recovery I've used before. For the second stage, I'm going to use the flip out fins I developed for my F9 project. I've never done three stages before, so I don't know what that is going to look like.

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

At first I thought I would be working with BT-60 Tubes as I've done before, but my initial calculations suggest that a BT-70 tube body would be closer to 1/88th scale for the Delta IV & comparable to the SpaceX models I've been building. In short, the Delta IV has a wider body than the Falcon 9 for the same height.

The first problem I've run into is a lack of dimensions for the Delta IV Heavy. From Wikipedia and other sources, I have body tubes about 16.8 feet in diameter and a total rocket height of 236 feet. But no breakdown of sections (unlike a wealth of information for the Falcon 9).

So where can I find reliable measurements of the Delta IV Heavy?

 

[NOLA_BAR]

I've started working on a new build at 1/88th scale of the ULA Delta IV that launched the Parker Solar Probe on August 12th, 2018. You can watch the Parker Solar Probe launch here. The Parker Solar Probe is now the fastest human made object ever. This will be a three cluster three stage model rocket.

As with my last project the goals of this build are ambitious:

1: 1/88th Scale so BT-70 tubes can be used for the body
2: A working thee cluster rocket with booster separation
3: Hidden fins for the second sage based on Tim's design at Apogee Rockets
4: A working third stage for the Parker Solar Probe
5: No glue, so parts can be replace as needed.

I'm going to use a modified version of my Falcon Heavy to create the Delta IV using the same magnetic booster attachment/separation and rear ejection recovery I've used before. For the second stage, I'm going to use the flip out fins I developed for my F9 project. I've never done three stages before, so I don't know what that is going to look like.

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

At first I thought I would be working with BT-60 Tubes as I've done before, but my initial calculations suggest that a BT-70 tube body would be closer to 1/88th scale for the Delta IV & comparable to the SpaceX models I've been building. In short, the Delta IV has a wider body than the Falcon 9 for the same height.

The first problem I've run into is a lack of dimensions for the Delta IV Heavy. From Wikipedia and other sources, I have body tubes about 16.8 feet in diameter and a total rocket height of 236 feet. But no breakdown of sections (unlike a wealth of information for the Falcon 9).

So where can I find reliable measurements of the Delta IV Heavy?

Check AXM space models website for his cardstock Delta IV. Might be of help in getting the dimensions you need.

 

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Here's my update on this build. I've got the design of the first stage core and strap-on booster mostly complete.

This is the bottom section of the core with fin slots and booster mounts. The core bottom motor mount is also shown with its centering ring and BT-20 tube. The Delta IV engine and nozzle will be attached to the centering ring and ejected during reverse recovery. The booster mounts which protrude from each side, will have 4x6mm magnets to hold the boosters in place.


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The core bottom motor centering ring has two magnet mounts which serve only to hold the motor in place before launch. Otherwise it could slide backwards out of the core body tube while sitting on the launch pad.



This is the bottom section of one of the boosters. On the right is the exterior booster mount which is non-functional but designed to match the Delta IV Heavy booster mount. Inside, you can see the lower motor centering. Like the core, the engine and nozzle are attached to this centering ring and ejected during reverse recovery.


The centering ring has holes for two magnets in the side. Like my Falcon Heavy the lower magnet secures the booster to the core. The upper magnet passes past the corresponding magnet in the core during reverse recovery. This pushes the booster away from the core because the pole is reversed on the upper magnet.


I made this poster to explain how the booster separation works

Here is the design of the upper booster mount with the centering ring on the booster. Like the bottom booster mount, small magnets secure the booster to the core. But here there is no need for a second magnet to push the booster away. This is because there is a hole in the side of booster where it attaches to the core. So when the centering ring is pushed down by the ejection charge, the hole is revealed and pressure from the ejection charge will push the booster away from the core. This is pneumatic booster separation.

The thrust struts are secured firmly to the booster but slide easily from the core during booster separation.



This shows the upper booster centering ring with its single magnet mount.


With these designs complete, my next task was to print to test how things fit together. After several mistakes, I finally got parts that fit pretty well.

 

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Here are some photos of the most recent iteration of parts I've printed.

Here is the lower section of the booster with the booster mount. You can see a small hole admits the magnet from the core booster mount. This provides an extra strong connection and extra magnetic repulsion during separation.


Here is the corresponding booster mount on the core. The magnet protrudes so that if fits into the hole in the booster show above. Fins slots are also visible.


Here the core and one booster are attached. You can see how the non-functional scale booster mounts conceal the functional (non-scale) magnetic mount. You will also notice a small hole in the core for the launch lug.


Here is the upper centering ring of the booster motor with its lone magnet.


Here is a close up of the upper booster mount on the core. Like the lower mount, the magnet protrudes into a hole in the booster mount for an extra strong connection.


Here you can see the upper booster attached to the core. You will also noticed a small hole in the core for the launch lug.


So that's all for now. Happy New Year!

 

[ebruce1361]

OOOH! This is very intriguing! I had an idea a while back to more or less do this same thing, but with BT60 tubes because I have plenty on hand. My idea for booster separation was a bit more clunky, using tiny electromagnetic actuators to open latches on the tops of the boosters, but I like the magnet idea better. Anything to make a complex rocket less likely to malfunction! The other main difference is mine was designed as a single stage cluster that just had a longer burning motor in the core stage that made the center keep going a second or two longer after the boosters detached. (See also Oranous, the rocket in my profile picture that behaves the same way)

Here's my thread where I was trying to find ideally shaped nose cones for the Delta IV Heavy, prior to me getting into 3D printing where I could just make my own.

 

[ebruce1361]

Also, I just read up on the details of the booster separation mechanism for your Falcon Heavy. That is one elegant design!

 

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I decided to redesign the flip out fins rather then modify the design used for the Falcon 9. Here is the second stage motor mount with centering rings. The "fins" here are just to hold the rubber band.


This drawing shows the flip out fins in the retracted position.


And here is the printed version with the fins extended.


Also, ebruce1361, thanks for the link on your Delta IV build. I'm using the same nose cones (from RTiknor on thingiverse https://www.thingiverse.com/thing:3673105.

 

[ebruce1361]

I might just have to steal that folding fin design! That is really cool! I'm not seeing where you have any kind of stop on the centering rings to keep the fins from swinging too far. Is it just a bump that the fin hits and keeps it from going further? Also, do you have a method of locking the fins open once deployed? I can imagine that with a squirrely crosswind, there's a risk of folding one or more fins back against the rubber band tension, and that could screw up the drag dynamics in the tail and throw the rocket off course. It probably wouldn't be too big of a concern, considering most if not all of us have flown a rocket with straight but misaligned fins, and that's pretty much what would happen if one of those collapsed. I just like the thought of a positive retention system like a latch that engages when the fins are open or maybe a detent mechanism.

 

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The hidden fins for the second stage are based on Tim's design at Apogee Rockets.

Here are some close ups that may help. You can see on the right, when the flip-out fin is folded back, there is a lever arm beyond the fin hinge that overlaps the stationary fin. That overlap stops the flip-out fin in the extended position. There is no mechanism to hold them in the extended position but the rubber bands are pretty tight. And as you can see, there is room to add additional rubber bands if needed.



Here is a close up of the extended fin. You can see how it overlaps compared to the photo above.


Note also the presence of two rubber bands on each fin. This lack of redundancy was a problem on my F9 project .


Oh and here is a link that compares the Delta IV Heavy to the Falcon Heavy. They are about the same height but differ substantially in girth. This is why I think BT-70 tubes makes sense for the Delta IV vs BT-60 tubes for the Falcon Heavy.

 

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I just finished the first draft of the reverse recovery motor mount.

This shows the engine nozzle with the motor tube and retainer clip.


And here is the same part viewed from the top.


This will be printed in four sections.

The centering ring and nozzle.


The engine exterior fuselage.


And the motor mount tube and BT-20 tube which will be inserted down the center of the above parts.


Here is the complete motor tube. A BT-20 tube is used to carry the ejection charge to the 2nd stage. You can also see the upper centering ring in this view.


The strap on booster motor tubes have a very similar design with the only difference being the magnet mount in the upper centering ring.

 

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Here's my latest update. All major parts are complete! I settled on the following resource for scale height: https://www.sky-brokers.com/uploads...8b1cd7d/ULA-Delta-IV-Heavy-Launch-Vehicle.pdf

Here's the Delta IV:


I still need to do fins, launch lugs. paint, and decals.


This is how it looks next to the Falcon Heavy. I think the scale worked pretty good.



There is still a lot to do but it is nice to see it come together.

 

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Today I got the fins done. There are still a few more details to work on but at this point it's ready to fly.


and close up:



Here's the parts list:

 

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This week I worked on the external appearance.





For this part of the project, I am extremely grateful to Alfonso X Moreno at AMX Space Scale Models. He has an awesome 1:96 paper model of the Parker Solar Probe Delta IV Heavy that you can print and build (but not fly). So I reached out to Alfonso and he generously agreed to provide a set of skins for this model at what we determined is about 1:90 scale. Note I incorrectly stated 1:88 scale several times above.

We also determined that the source I was using for measurements is not correct and so now I'm using ULA's documents
https://www.ulalaunch.com/docs/default-source/rockets/delta-iv-heavy-cutaway.pdf
and
https://www.ulalaunch.com/docs/default-source/rockets/delta-iv-user's-guide.pdf

Which I should have done from the beginning.

So the version you see above has had the core boosters shortened by 2", The interstage shortened by 1/4" and the 2nd stage lengthened by 1" since my last post. These changes were needed to fit Alfonso's skins.

The photos above are just printed on paper and taped in place to work out the problem areas like the lower booster mounts and thrust struts. I plan to use either water slide transfer paper or sticker paper for the final build.

The use of these color printed skins allows this model to have a level of detail that I never would have been able to attain with my meager skills.

Here's some close ups, you can see I still have a lot of work to clean this up.




Here you can see one of the thrust struts needs more sanding.

 

[ebruce1361]

Even though it's just printed paper wraps, the colors and the logos really bring out the proper look. Fantastic work!

 

[Huxter]

Excellent work on everyone's part. Truly inspirational. Thanks for posting

 

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Thank you. Alfonso's skins really took this project a step beyond what I had aimed for. I just need to fly this bird & all of the local clubs are shut down due to COVID-19. I've got a trip to Death Valley planned for spring break, so we will see what happens.

 

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So I finally got to light this candle and it wasn't pretty.



The pneumatic separation does not work with the fixed thrust strut arms. The rear ejection of the motor tubes is hindered by the transition of the 3D printed parts and BT-70 tubes; which means more feathering of that transition or narrower motor mount tubes. The parachutes need a drastically better method of securement so they don't snag on the internal tube transitions. It's basically a big mess as you can see...

On the positive side, I got three cluster ignition and at least booster recovery worked somewhat on one side.