So, maybe I'll try a three-stager

[JimJarvis50]

Hi Jim,
An excellent 'pre-christmas', eh?

Is that a carbon upper section or black fiberglass? That is, how are you handling radios? Also will this have your vertical autopilot & spincan [is that the finished spincan?] fitted or something different?

br/
Tony

Half of the black section is metal. It's just painted. The other half is a fiberglass nose cone, which has a straight section that will hold the altimeter bay. The radios will consist of Kate 2, which is .................(I should let Vern introduce her).

This rocket doesn't have the right flight profile for stabilization. The booster speed is up to Mach 2, and the rocket doesn't integrate with the stabilization module. So, we're not using it for this flight. The fins are a fin can but not a spin can.

Jim

 

[RGClark]

So, I had a box show up at the house yesterday, and there was a rocket inside. Woohoo! This came from Jerry McKinley, and it will be our Balls project for this year. This will be the sustainer, and it will sit on top of a 90% P motor. It will be fun. Now, it will be my turn in the barrel, to convert this fine rocket into a two-stage sustainer.

Since it will go around Mach 5, we need an ablative. The obvious choice, it seems to me, is the Firex RX-2376, which is the same stuff that the Princeton group is using. One benefit of it is that it essentially sublimates instead of leaving a char. All I have to do is to figure out how to apply it. The guy at Firex says you basically have to trowel it on as best you can, and then sand it smooth. I think the idea would be to apply maybe a 50 mil coat (in two applications) and then sand down to 30-40 mils. I have no idea how to trowel something on to a nose cone, or fins for that matter. I suppose I could pay someone a grand to apply it professionally ..... or not.

Jim

View attachment 381844 View attachment 381845 View attachment 381846 View attachment 381847

A 90%-P motor. Quite impressive. You must have built it yourself. How high do you expect your two-stager to go?

Bob Clark

 

[JimJarvis50]

A 90%-P motor. Quite impressive. You must have built it yourself. How high do you expect your two-stager to go?

Bob Clark

I had nothing to do with the building of either rocket (I don't do aluminum as a rule). The 4" sustainer was built by Jerry McKinley, and the motor for that will be something like a 43% O. The 6" booster was built by Ray Kinsel and Jim Long, and that's the 91% P. Stu is making the motors, Vern is making Kate, and I'm just going to try to make it all work together. Although the simulation is quite a bit higher, I would be happy if we cracked 300K.

Jim

 

[RGClark]

Best of luck on the launch. I was referring to that these are not off-the-shelf motors. Are you doing anything special to insure ignition of the second stage at high altitude?

Bob Clark

 

[JimJarvis50]

Best of luck on the launch. I was referring to that these are not off-the-shelf motors. Are you doing anything special to insure ignition of the second stage at high altitude?

Bob Clark

The video link shows what I have tried to date. This approach doesn't seem to work with BKNO3-viton, so something different will be necessary if we want to add that material to the mix.

Jim

 

[verticallimits.nl]

Hi Jim,

Please find this link just as reference / another resource of a minimum diameter, aluminium, N to N two stage rocket including some info on our approach of HEI. https://www.verticallimits.nl/?page_id=3985

It succesfully flew last week.



VL

This approach doesn't seem to work with BKNO3-viton, so something different will be necessary if we want to add that material to the mix.

Jim

 

[dhbarr]

And in that configuration 15km or so was achieved?

 

[WFWalby]

And in that configuration 15km or so was achieved?

From the altimeter readings it looks to me like it went 21700m (21.7 km). Unless you are referring to a different post.
William

 

[dhbarr]

From the altimeter readings it looks to me like it went 21700m (21.7 km). Unless you are referring to a different post.
William

Ah, I only read the webpage thanks for the video tip.

 

[plugger]

Hi Jim,

Firstly, as per usual thanks for sharing the details for your upcoming Balls project. You're certainly cranking it up a notch! As for your questions, I'm far from an expert in any of this stuff but I'd like to share a few comments.

Question 1 - If I was going to touch Mach 5 I'd definitely want some type of TPS, both on the nose as well as the fin edges. I've done a few flights in the Mach 2ish range on rockets painted with rattle cans and those areas see the most Mach rash/heating from those flights. Also TonyL's comments regarding leading edge temperatures seem logical. A few weeks ago Skylon's precooler passed a test that was in the news. In those articles they quoted leading edge temperatures of the SR-71 doing Mach 3.3 at 80k ft AGL to be approximately 420 deg C. So, uh, yea; your flight will be toasty!
Question 2 - for a drogue if I were you I'd consider an over engineered cruciform chute (relatively simple) or the drogue design Curt vD has been using in his recent staging flights. Off the top of my head I can't recall specifically the name of that chute design but from his work they do seem to work quite well. Failing those maybe consider a ballute?
Question 3 - In short, NO IDEA!

Just a few other comments. First, I'm glad to see that your sustainer fincan welds are clean and travel the entire length of the join between the fins and tube. IMHO this makes sense from both an aerodynamic perspective as well as a survivability perspective. I think a lot of people that fly bolt on fincans and are shocked when their actual apogee falls quite short from the simmed apo. I expect most of this is due to the drag from the bolts not being accounted for within the simulation software as that's not easily modeled in OR. The fact that your welds are effectively fillets from an aerodynamic perspective is a good thing. Further, at Mach 5 I would be worried that the initial fincan photo you posted would suffer a RUD due to the slight cantilevering of the fin root at the leading edge. That's just a guess as the length of the cantilever is quite short but I do think that at Mach 5 they'd fold like paper. I've seen Nic Lottering fold up a cantilevered fincan on a M class MD rocket at much lower speeds comparatively, granted the cantilever was much longer. Still, at Mach 5 why risk it?

Finally, Kate 2? I expect that will include Vern's wireless staging board? So will you use Kate 2 for staging instead of your usual EasyMega?

As per usual, good luck!

Andrew

 

[JimJarvis50]

Question 1 - If I was going to touch Mach 5 I'd definitely want some type of TPS...

Question 2 - for a drogue...

I'm glad to see that your sustainer fincan welds are clean and travel the entire length of the join between the fins and tube...

Kate 2? I expect that will include Vern's wireless staging board? So will you use Kate 2 for staging instead of your usual EasyMega?

At the moment, I am leaning towards using the Firex RS-2376. I am having some trouble figuring out how to apply it. The data sheet says it can be applied using standard, suction-type spray equipment. But the rep says you can't spray it - it's more like you have to trowel it on. Hmm. I'd like to have a better idea about this before I spring for it.

One difference between this rocket and other similar flights is that the rocket will break in half in a conventional, dual-deploy mode, rather than being an out the top configuration. As a result of that, some people doubt that a drogue would even be needed to reach a reasonable speed at the main deployment altitude. My current thought is to use a small drogue, something like a ProX 12".

What you are looking at in the photo are the cosmetic epoxy fillets. The welding is similar to the picture I posted previously. I'm not a welder, but it is my belief that welding the entire fin is not recommended due to the effect of heat on the metal strength. This fin design consists of alternating weld and fin tabs, and the fin thickness is 0.2" (pretty thick for metal I think). Given that peak speed is at 40K or thereabout, it would surprise me if anything happens to the fins.

I wouldn't refer to Kate 2 as a wireless staging board, but the current plan is for Kate to control and report on the entire flight. I haven't yet determined if any Kate functions will be backed up with other electronics. The flight could be 100% Kate, 100% other, or some mix. Vern can introduce the details of Kate 2 when he is ready. In the short term, we are planning an all-up two stage test of the system, hopefully in the next month.

Jim

PS - TonyL, the attached pic shows the resistors we discussed. Two 47K resistors to the igniter terminals and the air frame. This is what you were suggesting?

 

[TonyL]

Hi Jim,
Yes [those are some bigguns], should be more than enough.

Regarding welding strength, skip welding or continuous welding has the same effect on strength, both weaken the aluminum [if it is heat treated] plus the filler usually is a different strength [lower] than the base material if it is 6061. There is no free lunch when it comes to welding 6061. The motivation for skip welding is more likely to be thermal distortion. All that said, should be fine as long as everything is straight and stays straight

br/

Tony

 

[JimJarvis50]

Hi Jim,
Yes [those are some bigguns], should be more than enough.

I decided to spring for the extra $0.05 just in case there are 2W sparks.

OK, now it is time to make some decisions. One thing that I often do on two stagers and other rockets is to build with a larger span than I need, and then trim the span to some optimum when all weights are known. We have gotten to that point, so, it's time to (maybe) trim the fins. This rocket is unusual because of the long motor and because the electronics are in the nose cone. Consequently, it is over-stable. The air frame diameter is 4.0" and the fin can diameter is 4.3". The stability margins at various conditions, calculated using the 4.3" fin can diameter, are shown in the attached table.

One goal of the process is to keep the stability above 2.0 calibers at the maximum speed. It looks like the fin span could be reduced from the current 4.5" to around 3.75", and still be above the 2.0 value. This would offer the advantage of less mechanical stress on the fins. On the other hand, the span would be slightly lower than the air frame diameter and the fin can diameter. Thoughts on this?

Jim

 

[TonyL]

Mostly you get to decide...
I would [and will] run my Cp calcs a couple ways: Rasaero's, Rocksim Barrowman, and Rocksim's version [or whoever else you like] and think about who I believe more. Over stable hurts in the jet stream, so I agree that a lot extra over 2.0 is undesirable.

You would not be the first to have fins shorter than the body diameter.

 

[plugger]

What you are looking at in the photo are the cosmetic epoxy fillets. The welding is similar to the picture I posted previously. I'm not a welder, but it is my belief that welding the entire fin is not recommended due to the effect of heat on the metal strength. This fin design consists of alternating weld and fin tabs, and the fin thickness is 0.2" (pretty thick for metal I think). Given that peak speed is at 40K or thereabout, it would surprise me if anything happens to the fins.

All good, that was going to be my recommendation anyway (applying epoxy fillets) when you posted the first fincan pic. And I agree, I'd be surprised if anything happened to the fins.

I wouldn't refer to Kate 2 as a wireless staging board, but the current plan is for Kate to control and report on the entire flight. I haven't yet determined if any Kate functions will be backed up with other electronics. The flight could be 100% Kate, 100% other, or some mix. Vern can introduce the details of Kate 2 when he is ready. In the short term, we are planning an all-up two stage test of the system, hopefully in the next month.

Sorry, when you mentioned you'd be using Kate 2 in your sustainer I just assumed you'd pair it with the Mx140 Staging Controller that Vern has as if you're using Kate for flight events you'd need to leverage that as well for events given Kate is just a telemetry board with no pyro outputs. Specifically this unit.

https://www.multitronix.com/deployment.html

That said given I don't know a thing about Vern's Kate 2 unit I'm unsure if that functionality will be incorporated into the new unit or if it also requires a break out board to provide that functionality. Regardless I'd be curious to see someone use that Mx140 Staging Controller in a two stage 100k' + flight.

 

[VernK]

Sorry, when you mentioned you'd be using Kate 2 in your sustainer I just assumed you'd pair it with the Mx140 Staging Controller....

That said given I don't know a thing about Vern's Kate 2 unit I'm unsure if that functionality will be incorporated into the new unit or if it also requires a break out board to provide that functionality.

Kate 2.0 is a new design that is not quite ready for public release. However, just to provide a little clarification it does not require the Mx140 staging controller. That functionality is essentially built-in by adding an optional piggy back pyro board that provides all the deployment and staging capability. Kate 2.0 also features a GPS with unlimited altitude capability. It will deliver GPS altitude readings all the way to space. More details will be released in the coming months. Jim has one of the first prototypes but there are others too that are assisting with beta testing.

 

[plugger]

Kate 2.0 is a new design that is not quite ready for public release. However, just to provide a little clarification it does not require the Mx140 staging controller. That functionality is essentially built-in by adding an optional piggy back pyro board that provides all the deployment and staging capability. Kate 2.0 also features a GPS with unlimited altitude capability. It will deliver GPS altitude readings all the way to space. More details will be released in the coming months. Jim has one of the first prototypes but there are others too that are assisting with beta testing.

That's EXCELLENT news Vern! I've always wanted one of your units ever since I met you at Balls 23 (iirc) and you were showing Kate v1 off at the time. A number of the guys I fly with down here are sporting Lisa boards and safe to say they're a killer solution. I really look forward to learning more about Kate 2.0 although I can't imagine an unlimited altitude GPS capability comes cheap! Still it's great to know that you'll be catering to the 50km + crowd, determining apogee above that level currently is a bit of a doozy.

 

[plugger]

Jim, back to question 1, have you considered cork?

https://amorimcorkcomposites.com/en-us/materials-applications/aerospace/

 

[JimJarvis50]

That's EXCELLENT news Vern! I've always wanted one of your units ever since I met you at Balls 23 (iirc) and you were showing Kate v1 off at the time. A number of the guys I fly with down here are sporting Lisa boards and safe to say they're a killer solution. I really look forward to learning more about Kate 2.0 although I can't imagine an unlimited altitude GPS capability comes cheap! Still it's great to know that you'll be catering to the 50km + crowd, determining apogee above that level currently is a bit of a doozy.

Speaking of Kate 2, I was able to do a beta test with the unit this past weekend. Kate controlled the separation charge, the sustainer ignition. and the apogee and main charges. Tilt inhibition, as well as the apogee and main deployments, were controlled via gps. Pretty impressive I'd say. I think Kate will be at the helm at Balls.

My flight wasn't all that spectacular - just a J to a G to demonstrate Kate 2 and to get some experience operating the unit. Here's a video of the flight.

Jim

 

[OverTheTop]

Can Kate cope with multiple constraints to trigger the sustainer ignition? For my O-M flight I used a TeleMega and tied two of the deployment channels together (wired OR) to the HEI. One channel was set to trigger a timer on an event and if the tilt was less than 20deg then ignite the motor. The other channel was set to ignite the motor at a tilt of greater than 15deg, but less than 20deg. Both had additional minimum altitude lockouts set as well. Having the two methods of initiating the sustainer allowed it to deal with a) a really straight launch with no tilt, and b) a not-so-straight launch with a gravity turn happening. Both allowed me to launch the sustainer before my chosen 20deg verticality limit was exceeded. Does Kate have that capability? Just curious.

 

[VernK]

Can Kate cope with multiple constraints to trigger the sustainer ignition? For my O-M flight I used a TeleMega and tied two of the deployment channels together (wired OR) to the HEI. One channel was set to trigger a timer on an event and if the tilt was less than 20deg then ignite the motor. The other channel was set to ignite the motor at a tilt of greater than 15deg, but less than 20deg. Both had additional minimum altitude lockouts set as well. Having the two methods of initiating the sustainer allowed it to deal with a) a really straight launch with no tilt, and b) a not-so-straight launch with a gravity turn happening. Both allowed me to launch the sustainer before my chosen 20deg verticality limit was exceeded. Does Kate have that capability? Just curious.

Kate 2 will probably not handle that specific scenario. There is certainly no capability to set a sustainer ignition criteria for "tilt greater than a specified value".

The Kate 2 staging criteria has been kept fairly simple and compact in order to be able to display the criteria on the receiver's screen. This also makes it easy for a user to change the criteria just before launch if conditions warrant without needing to connect it to a computer.

The staging criteria boils down to this:

Arm staging when these conditions are met.
1. TIME > LIFTOFF + xx.x seconds
2. TIME < LIFTOFF + xx.x seconds
3. BOOSTER ACCEL > xx G's
4. BOOSTER VEL > xxxx feet/sec at xx.x seconds
5. BOOSTER ALT > xxxxx feet/sec at xx.x seconds

Fire sustainer motor when these conditions are met
1. TIME > BURNOUT + xx.x seconds
2. TIME < BURNOUT + xx.x seconds
3. TILT < xx degrees for xx.x seconds
4. xxxx < VELOCITY < xxxx feet/sec
5. xxxxx < ALTITUDE < xxxxx feet

Any criteria that is not needed can be set to something that essentially makes it a non-constraint.

I don't want to derail Jim's thread here. If more questions arise about Kate 2 then we should probably start a different thread.

 

[JimJarvis50]

So, the SpacePort Cup event is over, and while I'm recovering from it (it will take a couple of weeks), it is time to return focus to the Balls flight. It will be a large P motor to mid O motor two stager, projected to exceed 300K (it could happen). With the successful test flight of Kate 2, I have modified the nose cone ebay to provide a luxury home for Kate. Kate will control the entire flight, including staging and gps tilt inhibition. A few pics of the mounting are attached.

Jim
[/ATTACH]

 

[JimJarvis50]

I have also mostly completed the interstage coupler. Very low tech, but it will do the job. The design and a few construction pics are attached.

The electronics sled will be for the stage separation charge (with the timer I got from Eric C.).

Jim

 

[Wallace]

Jim; Is that Aeropoxy Light filler forming the transition?

 

[JimJarvis50]

Jim; Is that Aeropoxy Light filler forming the transition?

It was Aeropoxy laminating epoxy with West 410 filler. It makes a solid that is a lot like wood. One thing that is nice about it is that even when a lot of filler is added, the mixture still pours. Works well for what I was doing.

Jim

 

[Wallace]

It was Aeropoxy laminating epoxy with West 410 filler. It makes a solid that is a lot like wood. One thing that is nice about it is that even when a lot of filler is added, the mixture still pours. Works well for what I was doing.

Jim

Hope Ya don't mind me borrowing that idea on occasion. Was wondering how you could've possibly done that so neatly with sticks to everything in sight Aeropoxy light. I know it works because you've done it successfully, but it just has that look about it that makes me think temperature related expansion between those 2 would be a problem..

 

[RGClark]

So, the SpacePort Cup event is over, and while I'm recovering from it (it will take a couple of weeks), it is time to return focus to the Balls flight. It will be a large P motor to mid O motor two stager, projected to exceed 300K (it could happen).
...

Jim

When is the Balls flight scheduled?

Bob Clark

 

[JimJarvis50]

When is the Balls flight scheduled?

Bob Clark

It will be September 20-22 this year.

Jim

 

[JimJarvis50]

So, the interstage coupler is now complete. Yes, I know.... If you had told me a few years ago that I would be painting rockets to match aluminum tubes, I would not have believed it. Such is the current state of affairs.

The forward closure with the head end ignition is also complete. Yes, I know.... If you had told me a couple of years ago that I would be using head end ignition, I would have at least been a little surprised. No choice on this one (with a flying motor case).

This head end system has the 47K resistors for ESD recommended by TonyL, and there is a shunt (as shown in the pics). Since Kate 2 will have an electronic shunt, this one will probably be opened just before raising the rocket.

I still have a few modifications to make to the part of the head end closure that goes into the motor. I may cut a well into the epoxy there to hold some magnelite pyrogen. However, I also have a batch of BKNO3-viton pellets. I need to use about 9 grams of pellets (20 or so of them) and I need to figure out how to hold them axially in position so that the closure can be screwed into the top of the motor case.

Jim

 

[VernK]

I have also mostly completed the interstage coupler. Very low tech, but it will do the job. The design and a few construction pics are attached.
View attachment 387140

Jim,
What part of your interstage coupler supports the weight of the sustainer during booster acceleration? Is the sustainer tail cone simply resting on that green colored plate that is just above the separation charge in your drawing? Or is there a feature on the airframe of the sustainer that rests on the top lip of the interstage coupler?
Vern