Blackhawk 29 aka 2nd Stage Sustainer Build "and More"

Had this almost ready to fly on Sunday at MWPX with the complex booster and interstage coupler / sustainer initiator all prep'd. Then I moved to the "simpler" sustainer av-bay and low and behold, I had left the av-sled back in my workshop. Given the tight quarters in the bay I didn't feel comfortable jury-rigging something there at the field. I guess it just wasn't meant to be (as I also left my black anodized button screws for the bay also so it didn't look as totally cool as it could have). So I "stood down" and will try to make it up to Lafayette, IN on November 17th for its maiden flight.

Darn. I was really looking forward to the flight report. Best of luck for the 17th.
Jim

JRL303 said:

Darn. I was really looking forward to the flight report. Best of luck for the 17th.
Jim

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Well, as things go Nov. 17th didn't work (family obligations) and neither did Dec. 8th (weather) so the new date is Sunday, Jan. 13th (since the world did not end today).

Actually kinda sad... There it sits in my office against the bookshelf fully prep'd (with the exception of tracker and packing the sustainer chute which will be done last minute/at launch).

Finally this rocket was flown at Thunderstruck 4 on Friday. First comment is, "Here's to LiPo batteries! " as I literally pulled the rocket from the wall in my office inserted the tracker at the field and packed the sustainer main chute then turned on the electronics on the pad and flew it. The rocket had been prep'd six months before. Charge on the LiPo's were still intact and worked fine.

Now to more important stuff--as ones have pointed out, the real test here was the interstage coupler and it's overall stability. Happy to say the "up part" of this flight worked great. The booster was an I161W which lit immediately. Steady 15mph winds forced weathercocking on the way up, but the sustainer/booster joint worked great with the sustainer being lit from the interstage coupler Raven once the velocity fell below 100fps and the F52T took over and sent the sustainer off to the northeast. If you have followed the thread, the interstage coupler was custom made and Kevlar-lined and utilized the 29mm Slimline retainer and three shear pins to hold the sustainer in place. The idea was once the sustainer motor lit, shear pins gave way and off the sustainer went. I expected that there may be significant damage to the interstage coupler, this did not happen. The white high-temp paint was soiled only slightly, not burnt and the internal cavity of the interstage coupler looks almost as new.



Interesting flight graph from the sustainer is shown below--clear that the Raven settings in the booster worked fine as the sustainer motor hit once the rocket slowed sufficiently.



Now the down part, which didn't work so great... First, the booster recovered without damage, but clearly the charge on the forward-positioned drogue was too big as it also broke the shear pins on the booster main. The main came out while the booster was still moving at a fast clip (~100fps) and the main lost half it's shroud lines and the whole thing fluttered down about 300 feet from the pad. On the sustainer, although cannot be confirmed (as the above graph could be either could either represent a flat spin of the uppers section or a drogueless descent), it looks like the drogue charge was also too big as the Kevlar shock cord was snapped about 3" down from the harness loop on the aft end of the av-bay (the other possibility is that in descent the whole rocket was spinning and friction sheared the Kevlar, but hard to imagine this scenario). In any case the lower fin/airframe assembly on the sustainer gave way and after hours of searching, was never found. All other parts were recovered as shown in the pile below and, with a rebuild of the lower section of the Blackhawk 29, could be flying again (this time with a bigger motor combo).

I have to ask... did you ground-test everything? There's no mention of that in the thread.

CarVac said:

I have to ask... did you ground-test everything? There's no mention of that in the thread.

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Yes, I did. 1g BP in the sustainer for both main and drogue. 1.5g for booster main, 0.3g for booster drogue. The tough thing on the booster was that there was a huge difference in performance with just a bit more/less BP--drop it a 1/10 and no separation, up a 1/10 and you blow the assembly 20 feet out. To adjust for the variability, I upped the three shear pins on the booster main to 4-40 screws from the original 2-56 size.

I also plan on letting the pressure of the the second stage eject the booster, glad to hear that it works. If you watch the slow motion of motor start ups there is a significant about of pressure build up, that its entirely possible that the booster is long separated form the sustainer before full thrust is achieved.


TA

Tim,

I think I saw the lower section of your Blackhawk 29 when I was out recovering the Purdue USLI rocket. Unfortunately, I wasn't thinking and I didn't pick it up. From how I saw it, it looked to be completely undamaged. I could give you a description of where it is, and even help you look for it if you would like.

Brian, great. PM me with the location... Will you be at next weekend's launch? /Tim

BsSmith said:

Tim,

I think I saw the lower section of your Blackhawk 29 when I was out recovering the Purdue USLI rocket. Unfortunately, I wasn't thinking and I didn't pick it up. From how I saw it, it looked to be completely undamaged. I could give you a description of where it is, and even help you look for it if you would like.

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I hope this partnership works out - would be great to see the original lower section recovered and flown again!

mrwalsh85 said:

I hope this partnership works out - would be great to see the original lower section recovered and flown again!

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Talking with Brian... Right now from his description of the sustainer fin can location, it looks like the fin can must have descended with the rest of the rocket for most of the duration of the flight descent. Given the weight of the fin can with the motor case, it just couldn't be as far south as Brian describes unless it was under chute for some time. This then leads to some type of late shear or abrasion event versus a break right at the drogue charge event.

I once had a 54mm rocket fail to deploy anything and spin in about a mile from the pad. If your fin can pinwheeled, it could have traveled quite the distance...

patelldp said:

I once had a 54mm rocket fail to deploy anything and spin in about a mile from the pad. If your fin can pinwheeled, it could have traveled quite the distance...

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I doubt five miles. Given its trajectory and direction when the sustainer lit, it should have been far to the Northeast near the gun range. 15mph winds; even 30 at higher elevations, would not have put it a mile south of the launch site in the 2 to 3 minutes it would have taken to descend.

Found!! Although a mile plus SE of where Brian thought (all those plowed corn fields look the same ), his relative location of where it was in the field was spot on (which is half the battle).

I remember that flight Dan , Pine Planes correct ?

dixontj93060 said:

Found!! Although a mile plus SE of where Brian thought (all those plowed corn fields look the same ), his relative location of where it was in the field was spot on (which is half the battle).

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Interesting, I must have been thinking of the wrong fence line, but now that you say that I can see where it was. I'm happy to see that you found it, though!

BsSmith said:

Interesting, I must have been thinking of the wrong fence line, but now that you say that I can see where it was. I'm happy to see that you found it, though!

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No worries--thanks for the help!!

3stoogesrocketry said:

I remember that flight Dan , Pine Planes correct ?

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Funny you say that, I have done it twice over the years...

I was referring to my Crank 54 on a K700 two Red Glares ago. Thought for sure the main deployed at apogee, tracked it to the ground and thought because of distance and time elapsed it was under chute. Not the case!

dixontj93060 said:

... it looks like the fin can must have descended with the rest of the rocket for most of the duration of the flight descent.

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Glad you found the rocket. Now, time for the bigger motors!

Your comment reminds me of a funny story (at least it's funny now). I did a two-stage flight at Wayside a few years back. Not a bad flight, and I had the last gps fix when the main came out.

https://www.youtube.com/watch?v=BJuTn107lD8&list=UUPYKDbTKomB6yq_kcD0syLg&index=14

As we headed out for recovery, we picked up the RF tracker signal, which took us right to the rocket. When we arrived, there was no fin can. Crap! I just couldn't believe I had failed to attach the link, particularly when I distinctly remembered having done so during the prep. Anyway, we tried to calculate the apogee position to get an estimate of the location where the fin can would have fallen, and I walked for miles trying to find it. No joy.

About 6 months later, I got a call from a farmer in Wayside. He had found the fin can! I asked him where he found it, and the answer made no sense - it was nowhere near the estimated apogee position. As we talked more, I finally realized the fin can was exactly under the last gps position, perhaps a few hundred feet from where the "chuted" section landed. If we had just walked to those coordinates and looked down....

There was no link on the harness loop on the upper section, so I just assumed I had not connected it, and that the separation was at apogee and not at the point where the main came out. Funny thing is, there was no link on the U-bolt on the fin section either. To this day, I don't know how it happened.

Jim

JimJarvis50 said:

Glad you found the rocket. Now, time for the bigger motors!

Your comment reminds me of a funny story (at least it's funny now). I did a two-stage flight at Wayside a few years back. Not a bad flight, and I had the last gps fix when the main came out.

https://www.youtube.com/watch?v=BJuTn107lD8&list=UUPYKDbTKomB6yq_kcD0syLg&index=14

As we headed out for recovery, we picked up the RF tracker signal, which took us right to the rocket. When we arrived, there was no fin can. Crap! I just couldn't believe I had failed to attach the link, particularly when I distinctly remembered having done so during the prep. Anyway, we tried to calculate the apogee position to get an estimate of the location where the fin can would have fallen, and I walked for miles trying to find it. No joy.

About 6 months later, I got a call from a farmer in Wayside. He had found the fin can! I asked him where he found it, and the answer made no sense - it was nowhere near the estimated apogee position. As we talked more, I finally realized the fin can was exactly under the last gps position, perhaps a few hundred feet from where the "chuted" section landed. If we had just walked to those coordinates and looked down....

There was no link on the harness loop on the upper section, so I just assumed I had not connected it, and that the separation was at apogee and not at the point where the main came out. Funny thing is, there was no link on the U-bolt on the fin section either. To this day, I don't know how it happened.

Jim

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Jim,

On two occasions, my Competitor 5 has undone a quick link on my drogue shock cord, both times at the altimeter bay connection. The first time I showed up at the rocket and noticed it and thought "there's no freaking way I just hooked the quicklink and left it open." A couple of flights later, the booster actually fluttered in because of this, and again the quick was open, still on the shock cord. Reviewing the Raven data, you can tell where the booster drops.

On both occasions, the shock cord was about 1/3 of its stretched length because of the twisting done to it. Also, you can see indications on the u-bolt and quick link that spinning has caused the nut on the quick link to slap the u-bolt. Every time one hex point hits the u-bolt, it turns it slightly and eventually opens it.

I think that this could be what happened to you, assuming a quick link was actually installed.

Raven data attached.

View attachment Competitor5_M2800_11_17_12.FIPa

JimJarvis50 said:

Glad you found the rocket. Now, time for the bigger motors!

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Jim, you are right. The right motor combo will easily do 15Kft. BTW, thanks for the help is setting up the Raven ignition sequence.

patelldp said:

Jim,

On two occasions, my Competitor 5 has undone a quick link on my drogue shock cord, both times at the altimeter bay connection. The first time I showed up at the rocket and noticed it and thought "there's no freaking way I just hooked the quicklink and left it open." A couple of flights later, the booster actually fluttered in because of this, and again the quick was open, still on the shock cord. Reviewing the Raven data, you can tell where the booster drops.

On both occasions, the shock cord was about 1/3 of its stretched length because of the twisting done to it. Also, you can see indications on the u-bolt and quick link that spinning has caused the nut on the quick link to slap the u-bolt. Every time one hex point hits the u-bolt, it turns it slightly and eventually opens it.

I think that this could be what happened to you, assuming a quick link was actually installed.

Raven data attached.

Click to expand...

Well, something like that could have happened. I tend not to tighten my quick links very tight on the assumption that it's not likely they could open by themselves. Maybe not a good assumption. Since the rocket was exactly below the last gps, it's pretty much a certainty that the main deployment is what caused it to separate. I thought that perhaps the link broke, but there was no sign of stress on the harness. Oh well.

Jim