Falcon Heavy! BT60-based with separating boosters

[Cabernut]

It's about time for another scratch build. This time I'm going to try and build a model of the Falcon Heavy. I put together a model of one in OR as a test case for debugging a while back. Out of curiosity, I measured the dimensions of a Falcon 9 booster and lo and behold, it's nearly an exact scale of a stock 18" BT60 tube! I modified the .ork file to reflect actual building materials available and made a plan.

For the fairing section, BT70 is pretty close to scale and Discount Rocketry has the perfect BT70 1:1 rounded ogive nose cone, along with the perfect BT60 to BT70 transition, that somehow looks exactly like the one in the Falcon 9 kit that SpaceX sells on their site.

The side booster nose cones are supposed to also be 1:1 ogive, but I couldn't find any without turning my own, which I'm not set up to do right now. Instead, I'm using the PNC-60L "Big Bertha" cone since it's close enough and available.

Fins will be 0.093" Lexan. Motors will be 3x 24mm "E". Probably will try 2x C11s in the boosters with a D12 in the core for the maiden flight.

 

[dhbarr]

Woo!

 

[K'Tesh]

This is going to be FUN!!! I wanna watch this!!! op:

 

[snrkl]

Watching with interest!! :^)

I have been thinking about doing one of these for a while, but my experience to date with drop boosters has been less than ideal...

Two questions:

1) Can you please post the ORK file? and
2) what method are you planning for the booster attachment / drop mechanism?

 

[Charles_McG]

Fins will be 0.093" Lexan. Motors will be 3x 24mm "E". Probably will try 2x C11s in the boosters with a D12 in the core for the maiden flight.

Cabernut - looks awesome. How I wish OR had this ability when I built my Titan IIIe! (Same scale and tubing, by the way.) And I've flown similar motors - C11+E9+C11. It looks like you've got thinner Lexan that I could lay my hands on. My thick fins took a ton of noseweight to counter.

SO! Have you given thought to your flight profile? When do you plan for booster separation? And how? During Core burn, during coast, or near apogee? Nose-blow, or something internal? I wanted to do the separation during core burn. And did it (C11-0 with a little loose black powder on top) - but then realized that flight profile, when paired with nose-blow separation, leads to high speed recovery deployment that has turned out to be hard on the boosters.

Looking forward to seeing your solutions.

 

[neil_w]

op:

 

[rocketguy101]

Bonus points if you deploy the legs and land the boosters! This looks very interesting and I will be following too...I did not realize OR could handle side pods now, very cool!

 

[Cabernut]

I can post the .ork file late tonight, however it only works with one of the recent developer versions(17.11-rc2 or 18.01-rc3) and may need to be re-done when the next release is finally out to the public.

As for the booster separation mechanism, I'm going to try it with the same simple method as in Apogee's kit. Nose cone hook that releases on ejection.

As for the issue of booster separation and deployment at high speed, I'll have to check the sim plot for approx speed at that point and see what I can get away with. Last time I did separating boosters, they were built stout and had streamers. I would like them to come down on chutes this time if they can.

 

[eugenefl]

I can post the .ork file late tonight, however it only works with one of the recent developer versions(17.11-rc2 or 18.01-rc3) and may need to be re-done when the next release is finally out to the public.

As for the booster separation mechanism, I'm going to try it with the same simple method as in Apogee's kit. Nose cone hook that releases on ejection.

As for the issue of booster separation and deployment at high speed, I'll have to check the sim plot for approx speed at that point and see what I can get away with. Last time I did separating boosters, they were built stout and had streamers. I would like them to come down on chutes this time if they can.

Ahh...I couldn't figure out parallel boosters in OR. Nice to see it's a feature that's coming in a future release. Anyhow, I too started a build about a week ago. Custom turned parts (via makeshift lathe) using shipping tubes. I'll start another thread as to not detract and cross pollinate build threads. The sizes chosen were based around...wait for it...a 1:64th scale Hot Wheels Tesla Roadster. (The model is roughly a 1:68th scale build.)

 

[Cabernut]

...a 1:64th scale Hot Wheels Tesla Roadster. (The model is roughly a 1:68th scale build.)

That's awesome! I'll be following along.


Here is the .ork file - the one with the most accurate scale dimensions that I've made at 1:88 scale.
Note: It can be loaded in OR 15.03 however the boosters will disappear so it would go back to a regular Falcon 9 and the fin count will default to 3.

View attachment SpaceX Falcon Heavy - separating.ork

 

[Cabernut]

So after looking at the sim plots in more detail, with two C11-0s and a D12-5 in the core, the boosters would be separating at about 221 mph. That could totally shred the 12" chutes I had in mind.

Should I keep it simple, tried and true and just use streamers? Or is there another way to simply delay chute opening until closer to the boosters apogee? Roll it up in a long cord?

 

[Charles_McG]

The suggestion I received over on YORF was to use a small sliding ring on the chute lines. The ring limits how far the chute can open, until it slides down toward the shock cord.

The other suggestion was not to use plastic chutes, and to use long shock cords.

I haven't tried it yet.

 

[LithosphereRocketry]

So after looking at the sim plots in more detail, with two C11-0s and a D12-5 in the core, the boosters would be separating at about 221 mph. That could totally shred the 12" chutes I had in mind.

Should I keep it simple, tried and true and just use streamers? Or is there another way to simply delay chute opening until closer to the boosters apogee? Roll it up in a long cord?

What I did with my parallel stager is to have the boosters just hold on by their own thrust at liftoff and propped them up on the pad. Certainly not ideal but it worked- you could probably implement some kind of burn string if you want more secure mounting.

Sent from my LGL44VL using Tapatalk

 

[eugenefl]

So after looking at the sim plots in more detail, with two C11-0s and a D12-5 in the core, the boosters would be separating at about 221 mph. That could totally shred the 12" chutes I had in mind.

Should I keep it simple, tried and true and just use streamers? Or is there another way to simply delay chute opening until closer to the boosters apogee? Roll it up in a long cord?

I'd go the extra long shock cord route if you want some additional insurance against a chute shredding. The weight on those side boosters will be so light and without any passive guidance or boost will go unstable and into a tumble as soon as it separates from the main booster. That velocity will drop almost immediately on its own at ejection. In my last side booster project, the chute didn't completely unfurl and inflate until the booster was already on its way down. (It slowed that quickly!) This rocket was built circa 2003 and was a center 3" dia shipping tube with BT60 side boosters that had 18" plastic Estes chutes. This flight used a G80T center and E30T side boosters. It employed the "Ray Dunakin" parallel staging mounts. https://www.raydunakin.com/Site/Staging.html#7

 

[Charles_McG]

What I did with my parallel stager is to have the boosters just hold on by their own thrust at liftoff and propped them up on the pad.

So was the 'booster motor lights after the rest of the stack has left the pad' failure mode left uncontrolled?

 

[Charles_McG]

Thought of another option - 2xJLCR in the boosters. I'm sure John Beans would be happy to sell you 2-3 for this project

If the fins on mine were lighter, I'd have gone streamer. I just built too darn heavy. And ended up with 50-75g extra noseweight - I can't recall closer at the moment.

It looks like I had a lot of suggestions to use chutes with spill holes, too.

Man, I'm getting inspired. I had a Delta 4 Heavy on the wish build list. Might have to do a FH instead. BT70 to T344 is 1/62 +/- 3/60th. BT80 to BT100 is right about 1/55. I figured out how to do a smoother booster release for my 1/100 shuttle.

Titan IIIe threads:
https://www.rocketryforum.com/showt...d-separation-during-powered-flight-Titan-IIIe
https://www.rocketryforum.com/showthread.php?128446-Titan-IIIe-flight-report (with CATO video link)
https://www.rocketryforum.com/showthread.php?127179-Titan-IIIE (whinging about stability worries)

 

[Cabernut]

Cutting the fins tonight... man this is taking forever to cut 3/32" Lexan with a break-off blade knife. I have a fine-toothed hacksaw but that cuts kind of rough.

I really should have got a dremel for this kind of stuff...

 

[Charles_McG]

I used a table saw.

 

[LithosphereRocketry]

So was the 'booster motor lights after the rest of the stack has left the pad' failure mode left uncontrolled?

Pretty much- that's why it wasn't ideal.

However, smaller motors do tend to light faster, so the failure mode is less of an issue- still something to consider though. Not sure there's really an ideal solution either way- I just did it the way I'd seen in the past... This was built maybe a month before Apogee came out with their strap-on booster kits.

 

[cbrarick]

so if you're doing scale, you'll be flying late fourth quarter 2019?

cool project, can't wait to see it finished

 

[burkefj]

If you are doing straight edges you can score then bend over an edge and it will snap cleanly. Even 1/16 is overkill for this size model.

 

[Cabernut]

Here are the six of the rough-cut fins. Two more to go but that shouldn't take long now that I've done a few. Using the hacksaw is fastest but leaves a really rough cut. Otherwise a couple of them I cut by scoring and breaking along straight lines. I had to cut 50x on each side to break it so one fin is enough to make your hand hurt. They weigh in at 59g for 6 of them, so 10g a piece. Not light but not too heavy either.




I was going to do traditional TTW fin tabs, but the difficulty in cutting made me think otherwise. I decided it would be better anyway to make the fin tab full length along the root and just cut slots for the centering rings. I'll need to drill holes to make epoxy rivets as well. That appears to be the best, or only, way to secure polycarbonate fins to cardboard tubes.




Next I have to knock out two more of these fins for a total of 8 before sanding the edges down and making them exactly uniform in shape.

I also found a good FH logo that I'll place on the fairing.

 

[Nytrunner]

Going to pull a Qquake22 and pin them together to do all at once?

 

[Cabernut]

Going to pull a Qquake22 and pin them together to do all at once?

That's a good idea. I do have some wood dowels that would work...

 

[BABAR]

So after looking at the sim plots in more detail, with two C11-0s and a D12-5 in the core, the boosters would be separating at about 221 mph. That could totally shred the 12" chutes I had in mind.

Should I keep it simple, tried and true and just use streamers? Or is there another way to simply delay chute opening until closer to the boosters apogee? Roll it up in a long cord?

Something unique about your boosters. For each booster as a separate unit, the fins are asymmetrically placed. Pop the nose cones attached to streamers with no attachment to booster. Nose cones drop under streamer (use a long skinny one so easy to see). Boosters will fall horizontal with fins toward the sky.

Disadvantage: you have 5 things to track (Sustainer, two nose cones, 2 boosters. Could put a small streamer in each booster, mainly to help you find it)
How high is separation? How many bushes around the anticipated drop sight?

See T-bolt

https://www.rocketryforum.com/showt...(think-C-141)-Kevlar-Failure&highlight=t-bolt

https://www.rocketryforum.com/showt...(think-C-141)-Kevlar-Failure&highlight=t-bolt

 

[kuririn]

Have you tried an oscillating tool and blade for cutting Lexan/plastic? Much easier than a Dremel or hacksaw, and the low end models are very affordable. Before I bought the tool I tried the score/snap method with mixed results. It is also great for cutting plywood fins, as well as home improvement projects.

 

[LithosphereRocketry]

Something unique about your boosters. For each booster as a separate unit, the fins are asymmetrically placed. Pop the nose cones attached to streamers with no attachment to booster. Nose cones drop under streamer (use a long skinny one so easy to see). Boosters will fall horizontal with fins toward the sky.

Disadvantage: you have 5 things to track (Sustainer, two nose cones, 2 boosters. Could put a small streamer in each booster, mainly to help you find it)
How high is separation? How many bushes around the anticipated drop sight?

See T-bolt

https://www.rocketryforum.com/showt...(think-C-141)-Kevlar-Failure&highlight=t-bolt

https://www.rocketryforum.com/showt...(think-C-141)-Kevlar-Failure&highlight=t-bolt

Any reason not to leave the noses on shock cords? I would think they would act like mini-streamers and improve the descent speed as well as being easier to find.

 

[Cabernut]

It's been a busy week, but not too busy for motor mounts!

Three 4-inch "E-sized" motor mounts, each with two thicker black fiber CRs and one white Estes CR on the fore end. Engine hooks and blocks will be used for convenience ans I'm not expecting to use anything more than BP motors.





All set with those. Next, the plan is to square up the 8 fins to make sure they are nice and equally sized. Then drill holes in the roots for epoxy rivets, and slots to fit over the CRs. After that, cutting slots in the body tubes and crafting the booster attachment/release mechanisms.

 

[Cabernut]

Have you tried an oscillating tool and blade for cutting Lexan/plastic? Much easier than a Dremel or hacksaw, and the low end models are very affordable. Before I bought the tool I tried the score/snap method with mixed results. It is also great for cutting plywood fins, as well as home improvement projects.

I have one, a cordless Black & Decker, but one of the lithium ion cells went bad and won't charge now. Would have worked great with a fine toothed blade. It went bad after about 5 years of light occasional use.

 

[burkefj]

Consider notching the crs partially and fin root partially then you also have some mechanical lock between the two instead of just glue joint.