Named for the '89 Derby and Preakness winner. In many ways large, experimental rocket projects can be analogized to horse racing; endless amounts of work, preparation, and money (and a little bit of luck; animal illness/injury in racing, logistics and weather in rocketry) laid out on the line for one shot at a dream being recognized. And so, another Black Rock stream of consciousness story enters the abyss if for no other reason than having a digital diary to look back on later.
Story
Upon returning from the very successful Aeronaut trip, where Verrukt (3" N motor project with a 20:1 L : D motor built from start to finish in one day) was flown to 33,000' and ~M3.4 and fully recovered 10 minutes later, I figured I could hang my hat on that for the year. That lasted about a day; the day after my return, A5tro An0n and I were at the gym and I was sharing stories from Aeronaut when he started talking about making a push for Balls for our long-conceptualized composite cased vehicle targeting 100k'. While we ultimately decided that getting that together would require more bandwidth than life would afford either one of us over the next six weeks, the wheels were in motion for the Balls trip (clearly, the concept of another Black Rock trip isn't a very hard sell around here). Verrukt was optimized for speed, not altitude, due simply to the geometry of the motor; but, having an absurdly efficient mass fraction was a big part of the project's differentiation from the countless "hobby-style" min dia projects I've flown over the years, each topping out in the mid-M2 range and in the 30-40k' range. Building off of this trend in the right direction, both Mat and I will focus on mass fraction for Balls; he will slide an all composite fincan over an N5800 with no upper airframe (just a nosecone) and go for L3 in style, and I will build a semi-optimized 4" rocket centered around a long-ish 98mm motor we flew in New Mexico in March (in the rocket that was subsequently found by a Redditor), with the goal of not purchasing a single part and only using tubing and composite scraps laying around the shop, and tailor the motor for altitude this time, not speed. The timeline isn't quite as tight as Aeronaut, thank God; but we hustled to get our >50k' apps in before the deadline, and now it's time to get busy working in swim lanes to each get our projects ready. Game on.
Project
Last we checked on this case, it was flying in A5tro An0n's rocket to 33k' and M2.5 in New Mexico in March:
[YOUTUBE][video=youtube;inKtC9BnFiw]https://www.youtube.com/watch?v=inKtC9BnFiw[/video][/YOUTUBE]
A couple of notes on that project. First, I designed the motor to be super-conservative since the rocket was super heavy and non-optimized anyway. It was 78% solids with pretty large cores. It burned just fine, but it's time to dial it up a notch. That motor was 59" long with 54" of propellant; during a last-minute on-field switch from tower to rail buttons, a small (1/8") divot was drilled about 1/32" in to the top of the case inadvertently; I knew it would be fine because the last motor was running a pretty low pressure and the divot wasn't nearly as deep as the snap ring groove above it. I'm going to crank up the motor a good bit for Balls, so I'll get the top 2" or so machined off and a new groove installed; leaving me with a case between 56-57" and 51-52" of propellant. So, roughly a 13:1 L : D ratio; not nearly the 20:1 of the Aeronaut motor, but still longer than most hobby cases.
The right way to do this project is to do a 1/8" DOM case with pinned closures, but that requires a bunch of non-standard parts and a new case; we already have this case and though it's 3/16 wall and not close to optimized, this is a concession we're going to make since I not only have the case, but parts to fit it.
The motor will be 84% solids this time, on the higher end of what I usually run (82-83) but not crazy by any means; with proper processing it should still border on pourable. I'll dial up the Aluminum and add some Oxamide and tighten the cores just a pinch from the previous iteration, but not too much because the mass flux of this motor will be higher just because of the grains' chemistry, so we'll still go pretty conservative on the cores to keep the numbers right where we want them.
The rocket will be based on a scrap length of 1/8" thick carbon tube Mat tried to sell on here and ultimately received no interest; we'll be sure to make the tube feel wanted. Fincan tube will be 14" with G10-core fins vacuum bagged onto it with hi-temp epoxy; this will then be coated in an ablative Mat has been working on. This one won't be going as fast as the Aeronaut project, but since we're going for altitude now, we care about delam, so ablative is key.
An aluminum transition ring will slide over this, followed by roughly 3 feet of bare case. Then will be the typical upper airframe bolted into the forward closure with the av bay and dual deploy out of the nosecone. A change from the Verrukt design will be a second transition ring under the upper airframe.
Electronics will be a Stratologger, a Multitronix "Kate" unit, and a Telemetrum.
RasAero and Openrocket agree on 75k' at right around Mach 4; I think both are optimistic. If I crack 60, I'll be happy for an effort that cost me very little and provides an excuse to get back out to BR for the second time this year, especially since the previous iteration of this motor yielded 33k'. Manny will be making the trip with us, which was a last minute change and should make for good times all around.
I can't provide a lot of pictures just due to time constraints, but I can provide a good story, follow along if you wish. Look forward to seeing everyone out there-
Steve Heller
Story
Upon returning from the very successful Aeronaut trip, where Verrukt (3" N motor project with a 20:1 L : D motor built from start to finish in one day) was flown to 33,000' and ~M3.4 and fully recovered 10 minutes later, I figured I could hang my hat on that for the year. That lasted about a day; the day after my return, A5tro An0n and I were at the gym and I was sharing stories from Aeronaut when he started talking about making a push for Balls for our long-conceptualized composite cased vehicle targeting 100k'. While we ultimately decided that getting that together would require more bandwidth than life would afford either one of us over the next six weeks, the wheels were in motion for the Balls trip (clearly, the concept of another Black Rock trip isn't a very hard sell around here). Verrukt was optimized for speed, not altitude, due simply to the geometry of the motor; but, having an absurdly efficient mass fraction was a big part of the project's differentiation from the countless "hobby-style" min dia projects I've flown over the years, each topping out in the mid-M2 range and in the 30-40k' range. Building off of this trend in the right direction, both Mat and I will focus on mass fraction for Balls; he will slide an all composite fincan over an N5800 with no upper airframe (just a nosecone) and go for L3 in style, and I will build a semi-optimized 4" rocket centered around a long-ish 98mm motor we flew in New Mexico in March (in the rocket that was subsequently found by a Redditor), with the goal of not purchasing a single part and only using tubing and composite scraps laying around the shop, and tailor the motor for altitude this time, not speed. The timeline isn't quite as tight as Aeronaut, thank God; but we hustled to get our >50k' apps in before the deadline, and now it's time to get busy working in swim lanes to each get our projects ready. Game on.
Project
Last we checked on this case, it was flying in A5tro An0n's rocket to 33k' and M2.5 in New Mexico in March:
[YOUTUBE][video=youtube;inKtC9BnFiw]https://www.youtube.com/watch?v=inKtC9BnFiw[/video][/YOUTUBE]
A couple of notes on that project. First, I designed the motor to be super-conservative since the rocket was super heavy and non-optimized anyway. It was 78% solids with pretty large cores. It burned just fine, but it's time to dial it up a notch. That motor was 59" long with 54" of propellant; during a last-minute on-field switch from tower to rail buttons, a small (1/8") divot was drilled about 1/32" in to the top of the case inadvertently; I knew it would be fine because the last motor was running a pretty low pressure and the divot wasn't nearly as deep as the snap ring groove above it. I'm going to crank up the motor a good bit for Balls, so I'll get the top 2" or so machined off and a new groove installed; leaving me with a case between 56-57" and 51-52" of propellant. So, roughly a 13:1 L : D ratio; not nearly the 20:1 of the Aeronaut motor, but still longer than most hobby cases.
The right way to do this project is to do a 1/8" DOM case with pinned closures, but that requires a bunch of non-standard parts and a new case; we already have this case and though it's 3/16 wall and not close to optimized, this is a concession we're going to make since I not only have the case, but parts to fit it.
The motor will be 84% solids this time, on the higher end of what I usually run (82-83) but not crazy by any means; with proper processing it should still border on pourable. I'll dial up the Aluminum and add some Oxamide and tighten the cores just a pinch from the previous iteration, but not too much because the mass flux of this motor will be higher just because of the grains' chemistry, so we'll still go pretty conservative on the cores to keep the numbers right where we want them.
The rocket will be based on a scrap length of 1/8" thick carbon tube Mat tried to sell on here and ultimately received no interest; we'll be sure to make the tube feel wanted. Fincan tube will be 14" with G10-core fins vacuum bagged onto it with hi-temp epoxy; this will then be coated in an ablative Mat has been working on. This one won't be going as fast as the Aeronaut project, but since we're going for altitude now, we care about delam, so ablative is key.
An aluminum transition ring will slide over this, followed by roughly 3 feet of bare case. Then will be the typical upper airframe bolted into the forward closure with the av bay and dual deploy out of the nosecone. A change from the Verrukt design will be a second transition ring under the upper airframe.
Electronics will be a Stratologger, a Multitronix "Kate" unit, and a Telemetrum.
RasAero and Openrocket agree on 75k' at right around Mach 4; I think both are optimistic. If I crack 60, I'll be happy for an effort that cost me very little and provides an excuse to get back out to BR for the second time this year, especially since the previous iteration of this motor yielded 33k'. Manny will be making the trip with us, which was a last minute change and should make for good times all around.
I can't provide a lot of pictures just due to time constraints, but I can provide a good story, follow along if you wish. Look forward to seeing everyone out there-
Steve Heller
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