Night Launch Odd Roc Build Thread

[dixontj93060]

Actually got quite a bit done today. Most of the sub-assemblies were fit together. Just a few snapshots... First the main booster connected to the body from the bottom with eight well nuts; second the interface centering ring placed and installed--this is critical to get right as you need to secure the chute bay which is done with the four #8 studs and then cross-brackets at 45 and 225 degrees hold the CR in place with a 1/4-20 bolt which will double as the main body connection for the shock cord. The last two pictures are the LED sub-assemblies. Given that I'm foaming the fin can into the main body it will be nearly impossible to maintain any electronics on the booster. One of my priorities in any build is to be able to repair if any mishaps occur so I decided to build two "sleeves" that hold the 36 main body LED's. These sleeves slip down over the booster tube from the fore end making everything accessible from the nosecone area. Finally the mounting for the 9 LED's on the outside of the head/chute section (no changes here--one more triple LED array not shown but is on the back of the 4" tube).

[Micromeister]

Wow!
He's a LOT bigger then I thought!

[dixontj93060]

No posts for a few days... Besides completing a few work deadlines, I have been wrestling with the toughest issue in this build... I am fine with everything from the eyelids down (if aliens have eyelids), but have real issues with anything above that, i.e., the nosecone and fitting 2lbs of weight up there. I could have posted some intermediate pictures, but it just would have been confusing and a waste of your/my time. Suffice it to say, there is far less room in the upper cranium area than I expected, and extending an attachment down into the chute tube is out of the question--I'll be doing all I can to get the Nomex protector and an 68" chute into that area. In any case, after trying four options, I believe I have found a method to get my 2lbs of weight into what is 3 vertical inches (like Red Bull says, think "wings"). More later...

[dixontj93060]

Had a bit of a "blow out" when foaming. Not to be unexpected although that Frog tape seemed very secure. Oh well, I'll just have to be careful carving so as to not scratch the Lexan fins.

[Grimracer]

well of course.. aliens ooze off white...!

Looking good Tim.. Hope to make it to mwp to see it in action.

Grim

[dixontj93060]

well of course.. aliens ooze off white...!

Looking good Tim.. Hope to make it to mwp to see it in action.

Grim

Mike,

Actually got it all trimmed up and shot the foam with a coat of Key Lime green which is a fairly good match--more pics soon.

-Tim

[dixontj93060]

Well I haven't had much time to work on any rockets, let alone this one. Cut up an oak tree and split it today and installed half a floor in one of my rental houses, but just to bring this thread up to date...

We now have "alien green" foam. If you look close it is a bit rough, but from 10 feet, it blends right in. Second the inside of the nosecone (inside top of head) is ready to install the lead "muffin pan" weights--2 lbs will be sitting on the opposing brackets in the second picture. Next wiring assemblies are installed internal to the main body area and Velcro cross straps are located in the "cheek area" to hold the battery packs. Finally putting on "war paint"-like alien green reflectors for visibility during recovery just in case the lights are lost for some reason.

[Grimracer]

anymore progress you can share Tim?

So far so good!

Grimracer

[dixontj93060]

anymore progress you can share Tim?

So far so good!

Grimracer

Well, two steps forward, one back... I snapped the interface CR when I was tightening it down so I had to cut a new one. Given it's position/importance I bumped to up to a higher quality, thicker (1/2") plywood. Now I have to get longer studs. Still planning to fly it at MWP though so more pics will be forthcoming.

[dixontj93060]

I did make one change to the design regarding the nose weight. As was pointed out so subtly earlier in the thread, nose weight is fairly important in this design. I made provisions to put 2 lbs. in the nosecone (top of cranium) but after putting it together I felt uncomfortable with that heavy of a nosecone and getting it ejected effectively. So instead I took half the weight and mounted it at the bottom of the parachute bay.

[dixontj93060]

OK, wiring is pretty much complete now. I do have on order a small 11.1V LiPo from Tower Hobbies to run 6 more LEDs in the nosecone area. I decided to add these as it looks funny with the very top of the head being dark compared to the body and rest of the head. I will mount the battery and LEDs when I get them and will wait on an "in the dark" picture until then. In the meantime as you can see the larger 11.1V battery is mounted inside on one "cheek" and the two LED controllers are on the other side. In the center is the loaded parachute compartment. Under the parachute are the two lead "muffin" weights I had to reposition from the nosecone and they are mounted against the bottom CR of the parachute compartment.

Although I am almost done, there are lingering "pains in the butt" that I am dealing with:

1. One of the 3-position LED arrays in the head went south on me. I popped it open and found the positive wire had broken. I resoldered it, but am still only getting 1 of the 3 LEDs to light. Unfortunately this LED array was pointing forward on the right cheek. I am going to cut the wires and remount the back LED array in its place to get the light balance I want.
2. Nosecone alignment. This is a real pain. After cutting the top of the head the molded plastic "relaxed" on both the nosecone bowl and the top of the head area so now I'm not getting perfect alignment all around the perimeter. I am testing a few of the automotive clips that are used to attach bumpers, fairings and such. Hopefully they will work, but I'm open to other ideas (gap is approaches a 1/4" in one spot).
3. I just don't have enough room in the parachute tube to get the shock cord, 68" parachute and a Nomex blanket in there. I am considering adding some type of baffle to the top of the main booster tube to protect from the ejection charge. Alternatively I just stuff the top of the main booster tube with dog barf, but it will be a pain to get in there because I have a 1/4-20 cross bolt as a mechanism to hold the interface CR in place and attach the shock cord. Needless to say, the jury is still out here on which direction I will go.

[dixontj93060]

OK, attacking each issue one at a time and getting final items completed...

1. The steel mesh makeshift baffle looks like it will work.
2. Used automotive body tabs to help align top-of-head nosecone. Not perfect and really not completely happy with it, but it is better than it was before. Since time is running out, I'm going to have to go with it.
3. Although held together with four bolts, I added epoxy reinforcement to the top of the nosecone assembly to remove any final wiggle.

Remaining items:

1. Rewire/swap the right side and rear LED array's in the head.
2. Ground test? Although this is motor deploy, with the weight of the nosecone assembly, I'm concerned. I will try to ground test a standard 38/720 case & ejection well. Hopefully I'll get this done Sunday night.

On the final point above, according to calculations 1g of BP will give me 15psi at the end of the booster tube and I believe a standard 38mm ejection well holds 1.5g which would be 25psi. All good; but then I have the step from 2.5" diameter to the 3.9" diameter of the parachute compartment--what happens then? I'm pushing on more area/a bigger piston so do I get a positive effect? Or, because the overall volume increases at the end of the chamber is the effect negative? Inquiring minds want to know.

[ECayemberg]

Tim, get back to painting!

Regarding ejection gas pressure. I don't know, the larger the diameter, the less psi required to move the surface, but then again the 4" tube provides more volume. I'd say wrap a couple wraps of 1"+ masking tape around the outside of the well (knurled part), add 3 grams BP total, tape it up, and it'll deploy! Blow it out or blow it up!

Now get back to painting!

-Eric-

[dixontj93060]

Now get back to painting!

Ya, well, kinda wish I could... Client dinner tonight and I'm in my 24 hour dry period. Next round of painting tomorrow morning at 7am.

[SMR]

On the final point above, according to calculations 1g of BP will give me 15psi at the end of the booster tube and I believe a standard 38mm ejection well holds 1.5g which would be 25psi. All good; but then I have the step from 2.5" diameter to the 3.9" diameter of the parachute compartment--what happens then? I'm pushing on more area/a bigger piston so do I get a positive effect? Or, because the overall volume increases at the end of the chamber is the effect negative? Inquiring minds want to know.

You're making great progress, Tim. Look forward to seeing her (him?) next week.

To speculate on your BP question... a little of both. Pushing on a bigger area with the SAME pressure does give more force. But you will loose a bit of pressure in the step to a bigger tube, since the expanding gas effectively diffuses a little in the larger volume. Might be pretty close to a wash, though. Stepping to a larger diameter tube is really not any different from just having a longer tube of the same diameter... just more volume for the gas to fill.

[dixontj93060]

Kinda what it it going to look like on the pad before the J340M ignites into a shower of sparks!!!


http://www.youtube.com/watch?v=7KzWfyim_7k

[GDJ]

I love this!

[dixontj93060]

I love this!

Thanks.

No pics or video, but this afternoon's ground test went great. Nice ejection of nosecone and parachute. Steel mesh protected well. Standard 38mm motor charge worked just fine.

[SMR]

Kinda what it it going to look like on the pad before the J340M ignites into a shower of sparks!!!


http://www.youtube.com/watch?v=7KzWfyim_7k

Wow, looking awesome. Weather forecast not bad, either. T minus 6 days.

(And you're right. Those clear fins really are tough to see at night! )

[Grimracer]

you are a sik man.,.. I LOVE IT..

Hope to see it fly and I have to tell you about the "UFO vewing" I had back in the early 80s.. (not kidding my wife can verify).. it was COOL!

Anyway.. Looking fantastic.. can not wait to see it fly!

Grimracer

[dixontj93060]

you are a sik man.,.. I LOVE IT..

Thanks Mike.

One last, but important thing... Rail buttons top and bottom. Top was put on with a well nut in the back of the head. Bottom was initially drilled into the base CR, but I didn't feel comfortable with the 1/4" thickness so I put a 1" L-bracket wrapped around the bottom CR and up the back (between the heels) with another well nut attachment.

[dixontj93060]

Flew last night at the MWP night launch. Delay was cored to six seconds but should've been even shorter. Got to about 800 to 900 feet. Late, but effective deployment. The Little Green Man was recovered fully intact with zero damage. Overall very pleased. (Videos were taken, but don't know if they will come out in the dark--I'll take a look when I get unpacked on Monday.)

[dixontj93060]

OK, super crappy video of the Little Green Man. But my friend couldn't really focus and/or see what was happening out on the range through the viewfinder in pitch black. You don't even really see the bright blinking green which I was happy with, but you do see the "comet trail."


http://www.youtube.com/watch?v=oehvIIrfSQ4

Goals for next year:

1. Get rid of iffy motor deploy and add an enclosed altimeter bay integrated with the back hatch.
2. Fly on an EX motor made for the Kosdon 38/1116 case (29+" long)

[dixontj93060]

Goals for next year:

1. Get rid of iffy motor deploy and add an enclosed altimeter bay integrated with the back hatch.
2. Fly on an EX motor made for the Kosdon 38/1116 case (29+" long)

OK, it is "next year" and coming up at the end of March is Thunderstruck '12 with it's inaugural night launch. And with that hoopla, I want to knock off #1 above. Motor deploy in the Little Green Man is tough as you are taking a J340M fourteen second delay and coring it down to four to six seconds--not recommended by Aerotech and, thus very iffy. So I wanted to add an altimeter to the design, but given the drag of it's dumpy body and it's typical flight profile with the J340M, it was questionable whether I would pull enough gees in a flight to only ~1000 feet to reliably trigger an alt. So searching for other alternatives I was glad to see this item, the µMAD, the go on sale. I received it yesterday and did a bit of "ground testing" today in the office. Nice little device from Wooshtronics.


http://www.youtube.com/watch?v=PWENZPjq3yY

[ECayemberg]

Tim,

I thought that the T-struck night launch is for FAA "Class 1" rockets...ie under 3.3 lbs and 125g of propellant?

I hope I'm wrong; I like the big stuff at night and look forward to another lil' green man flight!

-Eric-

[dixontj93060]

I thought that the T-struck night launch is for FAA "Class 1" rockets...ie under 3.3 lbs and 125g of propellant?

Oh, bummer... I didn't see that... Seems so un-Thunderstruck-like!

HMMM... I don't think I have a night launch rocket that will fly on less than an H-motor?!?

Oh, well, I guess I'm a leg up on MWP11.

[ECayemberg]

Oh, bummer... I didn't see that... Seems so un-Thunderstruck-like!

HMMM... I don't think I have a night launch rocket that will fly on less than an H-motor?!?

Oh, well, I guess I'm a leg up on MWP11.

Bummer; I was hoping I was wrong! Either way, the magnetic apogee sensor is interesting...will watch to see how it works out. I recall Transolve releasing a magnetic sensor for deployment years back...not sure if they still make it or if it caught on?

I don't really have any dedicated "class 1" night flyers either. Nothing wrong with getting ready for MWP10!

-Eric-

[dixontj93060]

Nothing wrong with getting ready for MWP10!

Yes, woops, MWP10.

[daveyfire]

Oh, bummer... I didn't see that... Seems so un-Thunderstruck-like!

Yep. We've twisted arms, cried, begged, groveled, and other such verbs to the FAA in Chicago, but they will not (and claim they have never) issued a launch waiver after dark. It's frustrating to show them the paperwork from other night launches -- especially ones in their own airspace -- and still have them claim they don't happen.

Yay bureaucracy!

[dixontj93060]

It's frustrating to show them the paperwork from other night launches -- especially ones in their own airspace -- and still have them claim they don't happen.

Night launch? NIGHT LAUNCH? Who said night launch?; just a bunch of us sitting around this field warming ourselves at the bonfire (started by, uhhh, ammonium perchlorate)

What happens at Thunderstruck, stays at Thunderstruck...

Who's the LCO for the night launch anyway?@?!