Razorback - From the TV Series "The Expanse"

[lakeroadster]

A fella by the name of Seth Kallen Deitch posted a photo of "The Razorback" over on the Facebook Model Rocket Fanatics site. He was wondering if this would be a stable rocket.

Initially I thought no due to the cut-out sections on the side, which would allow air flow that would negate the base drag.

But then I thought the rocket could be built with Lexan covers that would fill in those cut-out sections, thus base drag would be in full effect.

This has the potential to be a really nice scale rocket, with some challenging techniques employed to make it look real. Its design lends itself to be a good rear eject spool design.

The rocket is three sided and conical.

The Open Rocket simulation is made using a conical reducer, but I used some tricks that @neil_w taught me to make it appear like there are cut-outs in the body.

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[SecondRow]

A member of our club scratch built a Razorback for 13 mm. I’ve seen it fly once and it was stable. Here’s a pic I took when he brought it to a club meeting. It was mostly finished at the time — he later printed up decals.

Good luck on your build.

 

[Daddyisabar]

It should be stable with the internal fiddly bits and nose weight and power.

 

[BABAR]

Didn’t Gary Byrum design something from Star Trek Original Series alien ship that looked a bit like this?

 

[Bill S]

Maybe you are thinking of the Tholian ships?

 

[lakeroadster]

Didn’t Gary Byrum design something from Star Trek Original Series alien ship that looked a bit like this?

Maybe you are thinking of the Tholian ships?

Way Cool .... Gary's thread is a great read and Art Applewhite also got into the mix.

https://www.rocketryforum.com/threads/tholian-web-spinner.136249/​

Reviewing the thread it doesn't appear Gary ever got this to fly stable, and Art Applewhite's cardstock version contributions seems to have run into a dead end.

Based on my experience building the Cygnus Probe Ship I think the tail cones are the issue with the Tholian Web Spinner's instability. The tail cones negate enough base drag that the rocket just isn't stable. It would have been interesting to "lop off" the tail cone and see if that helped the stability. Maybe have a section that is removable for flight, but can be installed for display.

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I'm 1st going to make carboard mock up of the Razorback, and give it a spin test. If that goes well, I'll know I can proceed with some margin of confidence that the finished model can be built to be stable.

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[Daddyisabar]

Put that single motor up high! Blast that Krushnic!

Drag Greebles rule!

Lordy forbid a three canted (tractor?) motor design with a kite tail streamer simulating a Tholian energy web strand. That would be sick.

 

[lakeroadster]

Put that single motor up high! Blast that Krushnic!

Drag Greebles rule!

Lordy forbid a three canted (tractor?) motor design with a kite tail streamer simulating a Tholian energy web strand. That would be sick.

The single motor mounted up high would likely change "the look" of the rocket.

That Supercharged Destrier-4 High-Velocity Epstein Drive is the most striking part of the rocket. But perhaps a cluster of 3 canted motors could be used.... food for thought.

 

[BABAR]

Hmmm, yup, take out the innards and this is basically a cross between an “Up Cup” (tip of the hat to @hcmbanjo or @jadebox , I theeeenk) and the King Tut.

However, concur the “innards” are kind of critical to the cosmetic look, so @Daddyisabar ‘s tractor motor forward doesn’t fit @lakeroadster ‘s vision.

Maaaaaybeeeee we can play a trick on Uncle Krushnic.

A while back there was a great design unfortunately aptly named “Suicide King”

https://www.rocketryforum.com/threads/open-body-missile-build-for-my-level-2.24733/
Lots of originality in the build, including gold leaf, but what grabbed me was the title concept, an open body. Can the Razorback have some sort of vents that will allow a moderately recessed motor to avoid Krushnic effect, and still have room for a streamer for recovery? The design itself is very draggy especially in ANY orientation other than ballistic (even then, it certainly isn’t an altitude hunter), a small streamer or even Nose Blow might destabilize it at ejection for reasonable tumble recovery

 

[lakeroadster]

Hmmm, yup, take out the innards and this is basically a cross between an “Up Cup” (tip of the hat to @hcmbanjo or @jadebox , I theeeenk) and the King Tut.

However, concur the “innards” are kind of critical to the cosmetic look, so @Daddyisabar ‘s tractor motor forward doesn’t fit @lakeroadster ‘s vision.

Maaaaaybeeeee we can play a trick on Uncle Krushnic.

A while back there was a great design unfortunately aptly named “Suicide King”

https://www.rocketryforum.com/threads/open-body-missile-build-for-my-level-2.24733/
Lots of originality in the build, including gold leaf, but what grabbed me was the title concept, an open body. Can the Razorback have some sort of vents that will allow a moderately recessed motor to avoid Krushnic effect, and still have room for a streamer for recovery? The design itself is very draggy especially in ANY orientation other than ballistic (even then, it certainly isn’t an altitude hunter), a small streamer or even Nose Blow might destabilize it at ejection for reasonable tumble recovery

At this point I think we're putting the cart in front of the horse. My preliminary Open Rocket simulation shows this rocket needs nothing more complicated than just a single motor at the base of the faux center drive.

I'll learn a lot from the mockup and swing test.

But I'm going to create a CAD model 1st.. to make the mock-up reflect the outer contours of the actual Razorback, so it will be aero-correct.

 

[lakeroadster]

Revised 05-11-2023: Now using plywood for the body.

Here's the drawing set for the Razorback foamboard body.

The body is a combination of a 3 sided pyramidal cone and a spherical cone.

Keep in mind there will be a nose cone attached to the front of this foamboard which will add a couple inches to the overall length

Once I cut and form this I'm hoping to use it for a swing test:

• Without the cut-out sections to simulate the finished rocket with Lexan side panels
• With the cut-out sections to simulate the finished rocket without Lexan side panels.

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[lakeroadster]

Revised 05-11-2023: Now using plywood for the body.

Worked some more on the CAD Model. Here are some screen shots.

You can see the (3) basswood stiffeners that glue inside the foamboard and the spiders on the outside of the BT-300 recovery bay. All this gets wood glued together.

The nose cone looks complicated, but it'll start out as a round pine nose cone turned on my lathe. Then I'll layout the triangular shape, drill the (3) holes and then sand the triangular shape on my desk top belt sander. At least that's the plan.

The rocket is going to end up pretty heavy... I keep updating the Open Rocket simulation to match the CAD model. Apogee is currently about 750 feet on a F52 motor.

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[Hobie1dog]

Worked some more on the CAD Model. Here are some screen shots.

You can see the (3) basswood stiffeners that glue inside the foamboard and the spiders on the outside of the BT-300 recovery bay. All this gets wood glued together.

The nose cone looks complicated, but it'll start out as a round pine nose cone turned on my lathe. Then I'll layout the triangular shape, drill the (3) holes and then sand the triangular shape on my desk top belt sander. At least that's the plan.

The rocket is going to end up pretty heavy... I keep updating the Open Rocket simulation to match the CAD model. Apogee is currently about 750 feet on a F52 motor.

View attachment 578528View attachment 578531View attachment 578529View attachment 578530View attachment 578532​

I think you'll always hold the title "TRF's Most Gifted Builder"

 

[lakeroadster]

I think you'll always hold the title "TRF's Most Gifted Builder"

You are too kind... as I see it, I'm a hack.

Folks like @neil_w , @Daddyisabar , @Dotini , @BABAR , @Cape Byron , @bad_idea and a plethora of others here build more elegant rockets than I do. And the feedback and ideas I get from other TRF members, such as yourself, is a big part of all my builds.

Pushing the boundaries of mindsim, as well as alternate building techniques, is what lights my powder.

 

[neil_w]

There are many, *many* truly excellent builders on this forum, including @lakeroadster. No one has a monopoly on it. Different folks have different strengths, but overall there are just a lot of great builds around here. I am amazed and impressed all the time at the great stuff I see from folks. It's inspirational, and one of the best things about following this forum.

But there is one title I would give to @lakeroadster, uncontested and without question: best CAD drawings. Always worth following just for the amazing eye candy!

 

[bad_idea]

You are too kind... as I see it, I'm a hack.

Folks like @neil_w , @Daddyisabar , @Dotini , @BABAR , @Cape Byron , @bad_idea and a plethora of others here build more elegant rockets than I do. And the feedback and ideas I get from other TRF members, such as yourself, is a big part of all my builds.

Pushing the boundaries of mindsim, as well as alternate building techniques, is what lights my powder.

Thank you, but I think you have me confused with someone else. My rockets are pretty horrific. Yours are amazing!

 

[Cape Byron]

Folks like @neil_w , @Daddyisabar , @Dotini , @BABAR , @Cape Byron , @bad_idea and a plethora of others here build more elegant rockets than I do. And the feedback and ideas I get from other TRF members, such as yourself, is a big part of all my builds.

Amazed to find myself mentioned in such august company. Surely that’s a mistake.

 

[lakeroadster]

Amazed to find myself mentioned in such august company. Surely that’s a mistake.

It's not a mistake, and you don't need to call me Shirley.

 

[BABAR]

Amazed to find myself mentioned in such august company. Surely that’s a mistake.

I was thinking the same, you beat me to it.

 

[Cape Byron]

I was thinking the same, you beat me to it.

You, my oddroc friend, are far more deserving in that list than me. Believe it.

 

[BABAR]

You, my oddroc friend, are far more deserving in that list than me. Believe it.

via this forum

the whole is greater than the sum of its parts.

As the Good Book says

let us consider how we may spur one another on


We have people like @Peartree and @cwbullet and many other moderators to thank for that as well.

 

[lakeroadster]

A couple more screen shots of progress on the CAD model.

The "Epstein Drive" looks more complicated than it is. Basically a nozzle turned on the lathe... some poplar dowels... and a flat support plate which I may get laser cut out of some light plywood.

Time to make detail drawings.

Who's a good source for getting some components laser cut?

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[lakeroadster]

Void... See Post # 81

Drawing Package - Post 1 of 2

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[lakeroadster]

Void... See post # 81

Drawing Package - Post 2 of 2

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[neil_w]

Curious: how long does it take you to create a set of drawings like that?

 

[lakeroadster]

Curious: how long does it take you to create a set of drawings like that?

I started this morning about 10:00 am and finished at about 3:00 pm.

When I started making the drawings, I had already completed the models. The more rockets I build, the bigger my part file collection gets. So it gets a little easier with each build.

 

[lakeroadster]

Revised the drawing set to Rev 04: To include the lower thrusters.... and..... a Launch Lug.

See posts 23 and 24.

 

[Bill S]

This is going to be way cool if you can pull it off.

 

[lakeroadster]

Updated the Open Rocket simulation based on the weights calculated by the CAD models. All those pretty Epstein drive parts and the thrusters make this a portly flier. And of course those parts behind the CG means I needed to add nose weight to bring the stability back to 1 caliber.

But we're still good using G motors, such as G77-4 or G40-4 or perhaps the mother of all MPR's, the venerable G80.

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[lakeroadster]

Forgot to post up the screen shot of the finished Razorback CAD model using Inventor's Starfield background.

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