Level 2 project: "Long Tom" LOC Cruiser -> stretched Tomahawk CM

[Nytrunner]

In the meantime, eagerly awaiting the reveal of the painted model. I fully expect to see it festooned with DRM decals.

DRM?

 

[Wallace]

Lol, that's just a high pressure region at the end of the nose. If you look at the legend, you'll see that area is all over 15.2 psi. Since atmospheric is 14.7, it's really not too high at all really.

If I was being paid for any of this analysis, I'd set Red to be a danger threshold, but then the whole rocket would be dark blue and boring. Since this is for my own entertainment, I set the rainbow chart so it looks good, and that's about it. Maybe I'll tweak it so it doesn't look like my nose is in danger of being crushed.

Now that you've pointed it out AND I actually took the time to look at the legend it isn't that bad at all. Also get the point about all the cool colors/vortices but that bubble and column of air shown "stacking" up ahead of the nose would be much less pronounced on say a 5 to 1 ogive? I've seen past posts where you've done cfd analysis and don't recall that rather strange artifact? Outstanding job by the way, I still type with two fingers and grab the nearest kid when I have a problem with my phone

 

[neil_w]

DRM?

Jokes are ruined when you need to explain them.

I should probably retire that one. Carry on.

 

[Nytrunner]

Jokes are ruined when you need to explain them.

I should probably retire that one. Carry on.

Im quite familiar with der Red Max, I just couldn't imagine that's what you were referring to in the context of a Tomahawk.

I probably had too much paint fumes and epoxy to grasp the disjoint humor at the time lol

 

[Nytrunner]

Now that you've pointed it out AND I actually took the time to look at the legend it isn't that bad at all. Also get the point about all the cool colors/vortices but that bubble and column of air shown "stacking" up ahead of the nose would be much less pronounced on say a 5 to 1 ogive? I've seen past posts where you've done cfd analysis and don't recall that rather strange artifact? Outstanding job by the way, I still type with two fingers and grab the nearest kid when I have a problem with my phone

Glad you find my meddlings of interest.

I'm actually a tad perplexed at that extended air deceleration ahead of the nose. I'd agree you probably won't find that on an ogive or Haak series cone.

The superellipse is supposed to be the optimal shape for subsonic flow, but I won't try and say that this hand laid nose is a perfect superellipse. I may risk melting my processors to do a higher mach simulation and see if I can develop that wierd spike into a detached oblique shock (which I expect with this blunt nose)

Maybe I'll post the results from my 1250 '/s case later. The pressure distribution is a bit more interesting and no shock bubble sits over my vent holes, so the only thing holding back the Loki M1387 is wing flutter

 

[Nytrunner]

Made a couple 1/2lb weight discs for the nose. Just poured 30minute epoxy and lead shot until it hit 8oz.

And here's the post processing on 1250 ft/s.

Cut plot and streamlines chart velocity. Yellow is ~1250 (simulated rocket velocity)
Surface plot is pressure distribution green is ~atmospheric pressure.

Big velocity and pressure differential at the nose and fins as expected for transonic
The odd low speed spike is gone, and the oblique shock is forming at the nose. Need to go faster for it to get more defined.
'Interestingly enough, the wings aren't in as strong a region of mach shenanigans as the primary fins



For kicks, I created a temperature palate. Not as high confidence in this one though, because my surface roughness is an assumption that's unlikely to be borne out in real life.



I tried to do a 3d isosurface plot, but my laptop objected audibly and it looked horrible. Instead of clean isovelocity bubbles, the case volume looked like swiss cheese. Future note! transonic isosurface plots look nasty

 

[Wallace]

Assuming the nose weights are going to be quick change for larger motors?

 

[Nytrunner]

Assuming the nose weights are going to be quick change for larger motors?

Truth

The discs are ~3/4" thick and I have ~5" of extra length in the nose tube (See Nose post on page 1)
Although larger motors just get longer and don't move the CG as far back as you'd think. This 16oz is conservative for a 93% K. I don't predict needing more than a pound additional to fit bigger ones.

 

[Wallace]

Very cool, always try to plan for contingencies but no matter how hard I try something ends up haunting me in the end...

 

[Nytrunner]

Couple overlooked details before the big reveal.

I mentioned the section keying slots, but never showed them, so here they are.

Nose key


Payload key


And booster key. Also.showing the 1515 railbuttons. I never got around to documenting the process of drilling for and inserting their brass inserts, but here they are anyway.

 

[Nytrunner]

Finally, it is done!

I now have a rocket that can't fit out the door vertically. (In one piece at least)




I'm still kinda proud of the boattail. That was the trickiest part of the whole thing.


Well, that's the build! I've learned a lot in the process and ended up with a behemoth I can lift in one hand that's theoretically capable of eating some Big motors.

Next time you'll see Long Tom, it'll be on the pad at NARAM.

Thanks for watching!
~A

 

[Nytrunner]

For the last 3 months, my free evenings (when I don't have outside plans) have been taken over by getting this thing ready in time for NARAM

With Long Tom complete now, I don't actually know what to do. Maybe I'll see a movie, or jump in the pool, or....I dunno, clean my bathtub.

 

[neil_w]

Spiffy! Paint came out great. Is the black and white grid on the bottom based on something in particular? I don't recall seeing a design like that before.

I this it looks especially good in the last picture, viewed from the rear.

 

[Nytrunner]

Thanks!


Edit: nevermind, I guess I never had that photo in this thread.
It's a test round in flight with what appears to be outlined warhead panels. I liked the look and felt it broke up the aesthetics

 

[neil_w]

Interesting picture!

TBH I like yours better.

 

[boatgeek]

That looks great! Good luck on your flight.

 

[Nytrunner]

That looks great! Good luck on your flight.

Thanks BG!

Last things I need to do are pack and get my car checked prior to the trip

 

[Nytrunner]

Mini update!

Surprise 10 hr day at the office Thursday when I planned to come iny late and leave early before the 19 hr drive to Pueblo.
Ended up having to arrive early for a customer meeting and a meeting ran long at the end of the day.

19 hr drive in 23 hours. Up a bit late last night prepping Long Tom, up to get out on the range by 9.

Couple things Ill talk tomorrow (or Monday)
-I am still not L2 certified
-Long Tom did actually fly and put in a fantastic performance.
-I have data to sift through to discover where an extra 700ft altitude came from

 

[Wallace]

C'mon! Why no Cert? Did you break the waiver? Congrats on the successful flight!

 

[Nytrunner]

No waiver breaking fortunately, although the altitude is....interesting.
Real reason I'm not certified is that I should have reviewed the L2 test a bit more. I missed a couple extra procedural questions, so I've got some study to do. My focus the last couple months has totally been on preparing the rocket and deployment, so the test became an afterthought. I was disappointed, but it brought to light some stuff that would be good to get deeper into the memory, so I treat it as a learning experience.

Then, as I was packing up and resigning myself to flying smaller rockets that day, the other fellow HARA member that attended NARAM walked up and asked how things went. I shared the bad news and that I'd be flying my other rockets. He said "Well, there will be other chances to take the test. You also drove all the way here to fly this rocket, so would you want to finish prepping it and fly it under my certification?" Directly following that, the L3 gentleman who had inspected Long Tom and discussed the test with me walked up and said "You've got some review to do, but I believe you know what you need to work on and you've built a good rocket. You won't be certified, but do you still want to fly it today?". Of course I wanted to fly it.

I hook up the shock cords, button up the ebay, and Club member and L3 both help me get it out to the tall pad and ready to go. Other than passing the test, I couldn't have asked for a better day. (Heck, another L2 candidate had a motor blowout after passing his test) Got tons of great advice, plenty of compliments on the rocket, and a great video (vv). This is a great hobby!
If you think about it, my L2 rocket now has a 90%K flight test under its belt



Some highlights:
:05 Liftoff Silhouette outlines the wings perfectly
:08-:12 Fin flutter modes! The wiggle makes me cringe, but they stayed on!
:55 Payload and drogue make an appearance. Best I can tell, the payload hangs under the drogue fine, but the wings on the booster made it do whatever it wanted.
1:50 Great view of the shadow touchdown




Prime and backup altimeters are within 9' of each other. 6980 and 6971 respectively for the RRC3 and Stratologger.
Recall from earlier in the thread, I was expecting a tad over a mile on the K750. Getting the flight data back, I started fiddling with OR to see what happened.
I had set my finish to regular paint because I've got mask lines and vinyl striping all over. Also double checked my environmentals for Pueblo's launch site.
Still wasn't much more than a mile. So I change my fins from rounded airfoil and bump the finish to smooth paint. No dice.
Eventually, I set the whole thing to Polished (lol) and it still won't go over 6200'. Nothing I can do to that sim file (with accurate final weight and measurements) can account for the ~800 extra feet that the altimeters are reporting. Maybe it's something to do with the nosecone profile being aerodynamically better than OR's? Go figure.

 

[neil_w]

Heck of a good flight. Too bad about the test, but you’ll get it next time, and the rocket is good to go.

 

[Nytrunner]

Heck of a good flight. Too bad about the test, but you’ll get it next time, and the rocket is good to go.

Thanks Neil! It'll happen eventually. I've just got to do it at our club meetings, then be ready to fly again when our field opens up!

**I updated the post with video highlight timestamps.

 

[MikeyDSlagle]

Dude! Failed the test? I can't really say anything that you haven't told yourself. So much time went into the trainer fleet and logging your build I thought for sure you had it in the bag. I studied A LOT for my test. But you know what to do now.

TRA has two separate tests, if you fail one you can take the other and hope for a better score...I think.

Some of my rockets won't hit altitude no matter what I do. I have come to within a few feet and been off by a few hundred. I pretty much just use sims for stability and rough estimates on altitude.

 

[Wallace]

It's actually pretty simple to fail the test. Your best bet is to take it before your actual flight date so you can focus. I failed, way to many distractions,launches,people asking questions...NAR makes you wait 30 days to re-test. If you join Tripoli you can take it the same day. Slightly different test though, so unless you've studied both...Why we need to know there's actually a CAR.???

 

[Wallace]

Nice flight btw!!!

 

[Nytrunner]

That was my plan. I requested to take the test at the last two club meetings, but they were....misplaced? No need to go further into that lol

Yeah, but have you overshot by a 1/4 mile Mike?

 

[A-N-D-R-E-W]

Looks beautiful on the pad! And great flight!

Now you HAVE to fly it again, sounds like a good deal to me!

 

[Tim51]

Sorry to hear about the L2 cert but congrats on what was clearly an excellent flight. As others have said, you'll get it next time.

 

[Steve Shannon]

No waiver breaking fortunately, although the altitude is....interesting.
Real reason I'm not certified is that I should have reviewed the L2 test a bit more. I missed a couple extra procedural questions, so I've got some study to do. My focus the last couple months has totally been on preparing the rocket and deployment, so the test became an afterthought. I was disappointed, but it brought to light some stuff that would be good to get deeper into the memory, so I treat it as a learning experience.

Then, as I was packing up and resigning myself to flying smaller rockets that day, the other fellow HARA member that attended NARAM walked up and asked how things went. I shared the bad news and that I'd be flying my other rockets. He said "Well, there will be other chances to take the test. You also drove all the way here to fly this rocket, so would you want to finish prepping it and fly it under my certification?" Directly following that, the L3 gentleman who had inspected Long Tom and discussed the test with me walked up and said "You've got some review to do, but I believe you know what you need to work on and you've built a good rocket. You won't be certified, but do you still want to fly it today?". Of course I wanted to fly it.

I hook up the shock cords, button up the ebay, and Club member and L3 both help me get it out to the tall pad and ready to go. Other than passing the test, I couldn't have asked for a better day. (Heck, another L2 candidate had a motor blowout after passing his test) Got tons of great advice, plenty of compliments on the rocket, and a great video (vv). This is a great hobby!
If you think about it, my L2 rocket now has a 90%K flight test under its belt



Some highlights:
:05 Liftoff Silhouette outlines the wings perfectly
:08-:12 Fin flutter modes! The wiggle makes me cringe, but they stayed on!
:55 Payload and drogue make an appearance. Best I can tell, the payload hangs under the drogue fine, but the wings on the booster made it do whatever it wanted.
1:50 Great view of the shadow touchdown


View attachment 359063 View attachment 359064

Prime and backup altimeters are within 9' of each other. 6980 and 6971 respectively for the RRC3 and Stratologger.
Recall from earlier in the thread, I was expecting a tad over a mile on the K750. Getting the flight data back, I started fiddling with OR to see what happened.
I had set my finish to regular paint because I've got mask lines and vinyl striping all over. Also double checked my environmentals for Pueblo's launch site.
Still wasn't much more than a mile. So I change my fins from rounded airfoil and bump the finish to smooth paint. No dice.
Eventually, I set the whole thing to Polished (lol) and it still won't go over 6200'. Nothing I can do to that sim file (with accurate final weight and measurements) can account for the ~800 extra feet that the altimeters are reporting. Maybe it's something to do with the nosecone profile being aerodynamically better than OR's? Go figure.

Have you overridden the Coefficient of Drag? Make everything else match what you believe they really are (including actual barometric pressure and elevation of launch site), then change the Cd until you get the same altitude you flew.

 

[Nytrunner]

Have you overridden the Coefficient of Drag? Make everything else match what you believe they really are (including actual barometric pressure and elevation of launch site), then change the Cd until you get the same altitude you flew.

I wasn't aware OR had a Cd override! I thought surface finish was the only method we had currently.

On which panel is it located?