Dual deployment in a BT20 (18mm) min diameter rocket

[cwbullet]

Thanks!

Yes. I'll save some details for an announcement when it's closer to going on sale.


12 grams, including the bulkheads, battery, charges, etc, basically what is in my hand in the first photo, minus the BP.

Woohoo.

 

[Blast it Tom!]

My feelings too, Tom. I'm a lowly L0 that made the longest burning "M"oonburner of 54 seconds. That's me next to it in my profile picture. The paper is on the RCS site. In 1978 at NARAM 20, I gave Vern two 18x70mm composite motors. Vern was interested in a higher performance 18x70mm motor. His jaw hit the floor, not only that they were "F" motors, but the propellant had an Isp of 239. These 18x70 & 80mm motors were a real kick if you had a fiberglass rocket that could go supersonic within 50ft off the launch rod. Model rocketry was not ready for an 18mm "F" motor in 1978.

So... you have enough technical chops to design a long-burning moon core, but you never did the L1-2-3 thing? Interesting! And you hit F impulse (at least 40 Ns, right?) In an 18 x70 mm package? For Pete's sake, that's what it's all about in the end, right? The biggest punch out of the smallest, lightest package. Wow... I know I'd have been ready for it!

 

[Spacedog49Krell]

So... you have enough technical chops to design a long-burning moon core, but you never did the L1-2-3 thing? Interesting! And you hit F impulse (at least 40 Ns, right?) In an 18 x70 mm package? For Pete's sake, that's what it's all about in the end, right? The biggest punch out of the smallest, lightest package. Wow... I know I'd have been ready for it!

Yes, the test motors to impress Vern were baby "F" at 40 - 40.5 N*s. If I could have worked out a deal with Vern, I would have downgraded them to an "E".

Working with Bill Wood on the Moonburner, he gave me his equations so I could build a test motor for him. When you work with people that have unique ideas, some of them rubs off on you. A few years ago, I found that Bill could not find his original equations, so I sent him copies of the equations he gave me in his old handwriting.

Talking about old times, I'm sitting at my desk working on my 18mm 900Hz flight computer. Wishing I still had a few of those 18mm baby "F" motors for testing this new flight computer. Adrian offers the 500Hz Blue Raven at a good price. He has now found interest in a DD altimeter for the LPR community. We have only scratched the surface on many of the technical issues of our hobby. There is more to be learned as we develop the technical hardware to see it.

 

[0011001100]

Congrats Adrian, but yes you are correct in that it has been done before:
https://www.rocketryforum.com/threads/smallest-dual-deploy-rocket.168679/

This rocket was meant to become a test mule for small 18mm motors but I got distracted with making faster propellant and then life happened.



Just look at that cute nozzle!

 

[kjhambrick]

Thanks for the link, @0011001100 !

Beautiful !

I love the idea of using the e-match plastic ends to hold the tiny ejection charges !!

Not to 'dimish' your accomplishment but one 'tiny' difference is that Adrian's rocket was an 18mm min diameter airframe

I would love to see @Rocketjunkie's reaction to the idea of an accelerometer that can ride in an 18mm coupler

-- kjh

$  echo 'scale = 4 ; d1 = 18 ; d2 = 24 ; pi = 3.1415926 ; r1 = d1 / 2 ; r2 = d2 / 2 ; a1 = r1 * r1 * pi ; a2 = r2 * r2 * pi ; a1 ; a2 ; 100 * ( a2 - a1 ) / a2 ;' |bc -l

x-sectional area( 18 mm ) = 254.4690 mm^2
x-sectional area( 24 mm ) = 452.3893 mm^2

percent diff( 24 -vs- 18 mm ) = 43.7500 % less x-sectional area

 

[0011001100]

Thanks for the link, @0011001100 !

Beautiful !

Not to 'dimish' your accomplishment but one 'tiny' difference is that Adrian's rocket was an 18mm min diameter airframe

-- kjh

Yep I missed that part. I did design the bay to fit in 18mm though but choose to use a kit I had in the build pile.

 

[kjhambrick]

@0011001100 --

I had never seen your thread -- there is no denying that your rocket is amazing !

Now I need one of Adrian's accelerometers and then I will need to take some 18mm grain casting lessons from @Rocketjunkie and I'll be all set

-- kjh

 

[Rocketjunkie]

I've been making 18 mm motors in C-F sizes. The longest is 12" long and comes out as a 80 N-s F23-10. I developed them during the COVID lock-down. I have a long thread on them in the research forum if you have access. ( https://www.rocketryforum.com/threads/18-mm-motors.158722/ ) (Also 24 mm motors in E-G sizes.) None require a waiver.

These are 18 mm 11" F20-10s (70 N-s) and an E13.

 

[Rocketjunkie]

Today I flew my first 18mm minimum diameter dual deployment rocket. I doubt I'm the first to have done this, but I don't know of any currently-available altimeters that could make this possible.

The Altus Metrum Tele Mini fits a BT-20 and is dual deploy with RDF tracking. Expensive for the whole setup and you need a HAM tech license. It will fit a BT-20 coupler if you sand off the corners of the terminal block.
10" of propellant F23-10 "fire and forget rockets". (10" of propellant, 80 N-s 2 middle ones.)

 

[Spacedog49Krell]

Thanks for the link, @0011001100 !

Beautiful !

I love the idea of using the e-match plastic ends to hold the tiny ejection charges !!

Not to 'dimish' your accomplishment but one 'tiny' difference is that Adrian's rocket was an 18mm min diameter airframe

I would love to see @Rocketjunkie's reaction to the idea of an accelerometer that can ride in an 18mm coupler

-- kjh

$  echo 'scale = 4 ; d1 = 18 ; d2 = 24 ; pi = 3.1415926 ; r1 = d1 / 2 ; r2 = d2 / 2 ; a1 = r1 * r1 * pi ; a2 = r2 * r2 * pi ; a1 ; a2 ; 100 * ( a2 - a1 ) / a2 ;' |bc -l

x-sectional area( 18 mm ) = 254.4690 mm^2
x-sectional area( 24 mm ) = 452.3893 mm^2

percent diff( 24 -vs- 18 mm ) = 43.7500 % less x-sectional area

My thoughts, too. My flight computer easily fits in the 24mm BT-50 tube. The 18mm BT-20 is making it a challenge. I'm modifying the castellated edge connectors to provide clearance. If I make a mother board it will utilize the castellated connectors on the modules.

 

[kjhambrick]

Thanks for the new word for myt vocab, @Spacedog49Krell !

I had to look up 'castillated connectors'

Here is one juicy article: Embedded Computing Design > HOME > TECHNOLOGY > ANALOG & POWER > PCBS & COMPONENTS > How to Design Castellated PCBs for Board-to-Board Attachment'

Definitely promising for shoe-horning a tiny modular device into a very limited volume !

-- kjh

 

[kjhambrick]

I've been making 18 mm motors in C-F sizes. The longest is 12" long and comes out as a 80 N-s F23-10. I developed them during the COVID lock-down. I have a long thread on them in the research forum if you have access. ( https://www.rocketryforum.com/threads/18-mm-motors.158722/ ) (Also 24 mm motors in E-G sizes.) None require a waiver.

These are 18 mm 11" F20-10s (70 N-s) and an E13.
View attachment 651820

Thanks for the pics and the video @Rocketjunkie !

I've already spent way too much time watching your static test and flight videos

One Q: is the running engine to distract your neighbors or do you need a generator to lite those motors ? ( )

The Altus Metrum Tele Mini fits a BT-20 and is dual deploy with RDF tracking. Expensive for the whole setup and you need a HAM tech license. It will fit a BT-20 coupler if you sand off the corners of the terminal block.

Yes, I've been thinking there has to be something smaller than those 'huge' green terminal blocks that would still allow for a quick, secure electrical connection but I've not found anything yet ...

Thanks again for the video and the pics !

-- kjh

 

[MidOH]

Solder tabs. Or solder posts.

We're not children, we can hardwire to a board. And could since 4th grade.

Iirc, somebody said you can desolder those green blocks easy enough, and direct solder wires in their place.

 

[kjhambrick]

Solder tabs. Or solder posts.

We're not children, we can hardwire to a board. And could since 4th grade.

Iirc, somebody said you can desolder those green blocks easy enough, and direct solder wires in their place.

Yes but It is hard to power a soldering iron at my prep table out at a launch site

Sorry, I was talking about connecting my e-matches to the terminal blocks on most avionics boards ...

-- kjh

 

[MidOH]

My field iron works fine. Plugs right into the trucks inverter.

Pretty sure I can solder my ignitor to a tab quicker than those tiny screws.

It's a viable option were overlooking. But then again, it might attract the schmucks with loud generators. I hate those guys.

 

[pugachu]

.
The future tilt is an estimate of what the tilt will be 3 seconds from now, based on the horizontal and vertical velocity. It's used for staging safety checking, though this isn't intended to be a staging altimeter.

Soo... If you do decide to include the staging feature, I would be very interested...

But the smallest low current e-matches that i've found won't fit into the nozzle of an 18mm RMS motor.

The AT D13 has a 0.077" throat, while the D2.3 has a 0.073" throat...

So I've ordered some 1/32" thick double clad FR4 to make tiny e-matches from...