LiquidFyre ABM

After the destruction of his Mean Machine my dad and I started discussing what we should build next. We have a been mulling over a design for years for a ridiculously large rocket with a fin span of over 8ft and is like nothing anyone has ever flown. But we have ruled that out as we would need to recruit a team to accomplish it. (PM me if your in the Chicago area and might be interested in that.) So the next idea that came to mind is a scale Sprint ABM (anti-ballistic missile). Given his business Python Rocketry he is in a unique position to make a really large Sprint missile probably with a diameter around 18" and a length of 9ft. I decided this sounded like a fun and unique project and the conversation quickly turned to how to get a Sprint like flight profile. The real Sprint missile launches from a tube and then lights it's motor and accelerates at 100 Gs to mach 10. Obviously mach 10 isn't possible, but 50-100 Gs might be. So we started contemplating a 60 lb rocket with a cluster of of Vmax or Warp 9 motor when someone at MMWP suggesting they know someone looking to sell an O25,000... Clustered with 4-6 75mm motors and you could get 60+ Gs to mach 2.3 or better. Unfortunately if we build that rocket we will only be able to fly it a couple of times at a limited number of fields unless we tone it down a lot.

That got me thinking that it might be fun to build a smaller Sprint-like rocket that could be flown at our local QCRS launches. Of course it would still need to be a completely ridiculous and be able to teleport off the pad. So I came up with the design that I am currently calling the LiquidFyre ABM. I quickly drew up the rocket in SolidWorks and built a simulation in Rocksim. The rocket basically amounts to stuffing one 54mm 4 grain and 6 38mm 4 grain motors into a 8 inch 5:1 conical nose cone. With a creative implementation of a launch lug, 3 small fins some camera shrouds (3 with cameras) to pull the the CP back, and a custom nose tip and tungsten shot for weight and the design is complete. Unloaded the rocket will weigh between 9.5 and 11 pounds depending on the amount of removable nose weight.

The sims indicate that the rocket can be made stable with any combination of engines, and with all of the engines lit on the ground it should be able to achieve 90+ Gs of acceleration. If I light a pair of lower thrust 38mm motors on the pad and quickly air-start the higher thrust cluster at .8 seconds I can get a very sprint-like flight profile with 8-9 Gs to 250 ft followed by 75 Gs till burnout.

Since some of the features in my design can't be put into Rocksim and since the stability margin is a bit tight (at least till I loose some propellant) I decided I need some real world testing. So I have 3d printed a 1/3 scale model that I can fly on a D21-T motor at a local park to do some testing. I will use nose weight to adjust the CG starting with a more conservative margin and trimming it back until I see some signs of instability. At that point I should have a pretty good idea of where the CG on the 8" rocket should be and how much nose weight will be needed to get there.

Mini Midwest Power shall be a must attend next year.

Would you mind sharing the dimensions and maybe even a basic CAD model?

I will do my best to have it built by then. Though I've yet to fly a high power cluster so even if it's finished I may be flying a single motor test flight to verify the stability at MMWP. Another wrench that might get into things is that Vmax propellant isn't currently available. Adjusting the sims to use a center warp-9 J1999N and 6 I1299Ns increases the acceleration of the pad according to Rocksim to approximately 146 Gs...

Cone shapes are stable in the sim but they have very little righting force especially at low speed.
Motors do not thrust straight and clusters don't light even.

During the Sprint's development a test vehicle called Squirt was built, which had a short cylindrical booster section with larger, more conventional fins. That might prove a more stable design to build for a first cluster launched from a conventional rail (..?)

Ravenex said:

Since some of the features in my design can't be put into Rocksim and since the stability margin is a bit tight (at least till I loose some propellant) I decided I need some real world testing. So I have 3d printed a 1/3 scale model that I can fly on a D21-T motor at a local park to do some testing. I will use nose weight to adjust the CG starting with a more conservative margin and trimming it back until I see some signs of instability.

Click to expand...

I remember reading somewhere that pyramid shaped rockets should have their CG about 2/3 of the way up the body. That seems like a lot as they should drag stabilize, but maybe necessary here too?

Also, if you're concerned about the thrust on warp9 motors, you could also look into the Super Thunder motors from AT, which still have a pretty good kick.

Oh you want teleport off pad? Okay those stupid hot 38/480 Aerotech I1299N-P loads did that for a two pound min diameter 38mm-29mm multistage back in university days... You know it’s only WARP9 Textron Defense Industrius Orbital Pegasus Fincan fuel that has a K class thrust curve in one third of a second burn time. Keep it under two pounds of rocket per warp motor. Should get you that high G teleport effect. We had 160G flight and it lost GPS lock for good. Beware thin wall structural components tend to implode at such high G loadings. You have been warned.

It might be fun to cover the front end in LEDs to make it glow in flight like the sprint did as it’s shell got white hot.