Two-stage P to O Space Shot attempt at BALLS 30

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Andrej

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This September at BALLS 30 me (Andrej Vrbec) and my friend Denis Banovic flew a two stage project. Since we are from Europe we packed all the rocket parts, tools and supplies in a big box and sent it across the ocean with cargo freight. We arrived in Reno one week before BALLS and rented a garage there. In the next three days we processed more than 180lbs of propellant and casted four motors- two boosters and two sustainers. Booster motor is a P motor, is 150mm in diameter and has 30kg (66lbs) of propellant. Sustainer motor is an O motor, is 100mm in diameter and has 11kg (24lbs) of propellant. All the motors are case bonded, monolithic grain type. Booster motor has a six-point star geometry and a faster burning propellant, while the sustainer is a simple core burner with a slow burning propellant. Thermal insulation/inhibitor was spin-cast in the casing a few hours before propellant was poured in. Since the flame zone gets in touch with the casing wall only at the very end, the casing insulation is relatively thin- 1mm for the booster and 0,5mm for the sustainer. Propellant was designed so that it can be processed on the field, with as little equipment as possible. Ridgid paddle mixer from Home Depot equiped with a custom made mixing paddle was used for mayority of mixing. After curative was added the propellant was mixed in a compact vacuum mixer that I built myself. The same Ridgid mixer was also used to turn the spin casting setup for thermal insulation. Off course having a propellant that is pourable and easy to work with, also means it can't have very high solids loading. That took some toll on the Isp, but in the end it worked out pretty good. Booster propellant had 80% solids loading and the sustainer 78%. My biggest concern was that AP that we bought in the US will have different particle size distribution than my regular AP, which could have a big impact on viscosity of uncured propellant. I prepared buckets (ingredients in each bucket were already pre-weighed for each batch) of propellant premix which contained everything except the AP and the curative. The only thing we had to do was empty the bucket in the mixer, add the AP, mix, add the curative, vacuum mix and pour. AP that we got was very good quality, but it had slighty higher fraction of fine particles which resulted in somewhat thicker propellant slurry that I was used too. I corrected for that by using somewhat higher processing temperature. After the motors were poured, they were cured for three days. Cores were cut out of styrofoam on a hot wire CNC machine. When the propellant was cured, cores were simply dissolved with a mixture of acetone and xylene. After a week of hard work in Reno we finally moved to Black Rock. One thing that was one of my main concerns was the launch pad. We didn't ship our launch pad because of the weight and the shipping was already expensive enough without it. To the rescue came Tony Alcocer who kindly borrowed us his launch pad and basically saved us, as we couldn't fly our project without the pad. The pad was very sturdy and worked perfectly for our rocket. Since the rocket weighed about 180lbs we decided to fly from Unistrut rail. I got the dimensions for Unistrut launch lugs from Aerocon website and I turned them from Delrin, hoping they will fit on a rail I have never seen before. Luckily the fit was perfect and as you can see in the video, the launch lugs got partially melted during flight from the air friction. We built two identical rockets. Most of the rocket is made from various aluminum alloys except the nosecone which houses the electronics and is made from fiberglass. Nose tip is machined from a phenolic composite and the same material is also used in the nozzles. One interesting feature is the interstage. It's of conical design and the cone that is bolted to the booster fits perfectly in the sustainer nozzle. Great care was taken when machining, making sure that the angle of the interstage cone is exactly the same as the sustainer nozzle divergent angle. Beauty of this design is that when the booster is pushing hard the connection between stages is very rigid and strong, but once the stages start to drag separate only slight movement is enough to break the stages apart.
First flight was on saturday. Basically everything worked as planned (motors worked, stage separation worked, high altitude ignition worked, rocket was stable for the entire flight, structurally it was strong enough to survive Mach 5 flight) except the telemetry. We got the telemetry for 4 minutes and then it stoped working. Based on data from telemetry flight went like this:

- Booster burned out and separated at an altitude of 3,5km and Mach 2,4
- Sustainer then coasted for 11 seconds and reached an altitude of 10km
- Sustainer motor ignited and burned out at an altitude of 20,5km and Mach 4,9
- Apogee charge was fired after 163 seconds
- After 4 minutes of flight telemetry was lost

We were using Telemega with an added RF amplifier, Raven 4 and a Featherweight tracker, plus a GoPro camera.
Second flight was almost identical except that the electronics ignited the sustainer at the booster burnout, without any delay. Why that happened is a mystery as both units were programmed at the same time and were double checked, so that the programming was identical on both. Because the sustainer fired without any delay the maximum speed was even higher, toping at Mach 5,4. Despite this the sustainer flew straight and true, but again telemetry from Telemega was lost a few minutes into the flight. After several minutes we got a data point from Featherweight tracker which showed that sustainer is 2km above ground and 26km away in the mountains east of Gerlach. We got there after some interesting off-roading and searched the area extensively but didn't find it.
All in all this was quite an adventure. I think we came very close in pursuit of our dream to fly to space. Based on time of flight to apogee, data we got from telemetry and comparing that to simulations I'm certain that at least the first one flew to space (over 100km). However we don't have the video or high resolution data from the flight computers. So the only option now is to work harder and try again.



Karman-2.jpg
 
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Wow! Great work. Great photo's in the video. Super impressed you were able to literally pour and fly. Metalwork looks top notch too.

For your next attempt, you might want to look into multitronix electronics which are engineered more for this flight profile. (https://www.multitronix.com/). I have no financial relationship with the company, just a satisfied customer.
 
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Allright, that's the report I've been waiting for :bravo: :goodjob: are you going with a different brand of telemetry the next time?
 
Beautiful project! Happy to see almost everything went well. Losing some ancilliary features of the flight doesn't detract from the overall success! Congratulations, and I hope you will share future flights.
 
How did you machine the interstage? For perfect nozzle matching, did you have to make test pieces?
 
Serious commitment to do a project like this, not to mention from overseas! Thanks for the report and video. You must have had a pretty progressive burn on that sustainer motor!
 
I think that this was one of the most impressive projects I've ever seen. Launching two complete space shot attempts in a single weekend is just crazy. And the rockets weren't absurd either. Projects like CSXT or the USCRPL rockets are impressive, but would cost too much for an amateur to attempt to replicate. I really hope you try again next year with a better telemetry package.
 
Pretty inspiring! I keep thinking the logistics of getting from Maine to Black Rock someday are challenging, I can’t imagine coming from across the pond!
 
You must have had a pretty progressive burn on that sustainer motor!
Not really. This motor takes advantage of the erosive burning. Since L/D ratio is pretty high, there is erosive burning at the beggining when chamber pressure would be low otherwise, but with erosive burning you get quasi constant thrust profile.
 
What kind of paint or coating did you use on the black parts of the rocket?
It's nothing special, just a high temperature paint. The nosecone epoxy/fiberglass composite is thick enough so that part of it can ablate away and it's still thick enough to carry the aerodynamic loads.
 
What a fantastic project !
You are an inspiration for all of us who dream of launching into space.
 
HTPB as opposed to PBAN I guess judging by curing times and no mention of a curing oven? Or was it PBAN? Just ask'in.
Man these folks are truly sick coming from Europe to mix here.:p Had to have some base support from somebody local I expect! Most I ever was involved in was a 25kg mix that was divied up into an N and many more motors of smaller size for various club members. We packed as opposed to pouring because that was how we were taught. Nothing against pouring but we had no one to train us in that technique personally.
Ummmm, it was a big mother mixer we did the 25kg in one batch. A lot of guys packing after the curative was mixed in. Did several mixes at that capacity and could make a bunch of motors at one time.
Only thing I can add is maybe a 2 meter Ham band APRS tracker might have helped in the sustainer as long as it didn't interfere with the onboard deployment electronics. Been there with interference and had glitches with my deployment altimeter devices with high Rf fields!😭
Actually a 70cm APRS Ham band tracker might have sufficed though it looks like there was room for a 2 meter tracker antenna. Redundant trackers if possible and room allows is a prudent idea.
The more Rf power in a tracker the better on the playa as with the rocket on the ground, the salt flats suck up Rf like a sponge and the ground footprint of a tracker of any kind suffers as a result. Can make recovery more difficult if the rocket touched down a lot farther away from the last known position. That is likely with a rocket such as this.
A higher powered Rf tracker with mainly SMT and low profile components would be ideal for a project like this plus making sure the batteries stay connected under high G loads and the electronics don't self destruct under G due to component mass.
I'm impressed and kudos to the guys!! :clapping:
Kurt Savegnago
 
I was there, one of many people in the spectator area watching. Seeing the booster burn out, then seeing the sustainer ignite many thousands of feet higher, was one of the most impressive rocketry spectacles I've ever seen. All with a gorgeous cobalt blue sky as a backdrop!
Over the years I've perfected my technique of shipping rockets and supplies ahead to the launch vicinity, in hard-sided golf club bag cases made by SKB. In the case of BALLS 30, shipping one SKB case weighing about 55 pounds roundtrip from Detroit to Reno and back via UPS cost about $370. But my shipping adventures pale in comparison to what these guys do! Andrej, if you're inclined to share, I'd be curious to know what the roundtrip cost of shipping your Big Box from Europe to Black Rock and back was.
It's only a matter of time until someone stumbles across the sustainer. I trust your contact data was included on the rocket.
Robert Schultz
TRA #05116, L2
 
Using the fit of the cone to nozzle as your interstage coupler was a stroke of genius! Did you have any mechanical connection between the booster and sustainer other than the matched cone/nozzle? Did you need to blue the pieces to get a solid fit?
 
We were using Telemega with an added RF amplifier, Raven 4 and a Featherweight tracker, plus a GoPro camera.
Second flight was almost identical except that the electronics ignited the sustainer at the booster burnout, without any delay. Why that happened is a mystery as both units were programmed at the same time and were double checked, so that the programming was identical on both. Because the sustainer fired without any delay the maximum speed was even higher, toping at Mach 5,4. Despite this the sustainer flew straight and true, but again telemetry from Telemega was lost a few minutes into the flight. After several minutes we got a data point from Featherweight tracker which showed that sustainer is 2km above ground and 26km away in the mountains east of Gerlach. We got there after some interesting off-roading and searched the area extensively but didn't find it.
There is a chance that another rocket carrying a Featherweight Tracker at altitude may have picked up a lost rocket packet from yours after landing. It sounds like your last packet may have been just before the line of sight from your ground station was obstructed by the mountains. Other rockets flying later could have had an unobstructed view. On my 2 flights at BALLS I picked up landed locations for 4 “lost” rockets, with rocketIDs of Huet-Rkt02, SEvesO2430, Alex Trkr, and SN53. What was your rocket ID? If Featherweight users who were there open up the Featherweight Inferface Program and check under More/Found, they might have the coordinates.
 
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There is a chance that another rocket carrying a Featherweight Tracker at altitude may have picked up a lost rocket packet from yours after landing. It sounds like your last packet may have been just before the line of sight from your ground station was obstructed by the mountains. Other rockets flying later could have had an unobstructed view. On my 2 flights at BALLS I picked up landed locations for 4 “lost” rockets, with rocketIDs of Huet-Rkt02, SEvesO2430, Alex Trkr, and SN53. What was your rocket ID? If Featherweight users who were there open up the Featherweight Inferface Program and check under More/Found, they might have the coordinates.
I'm SN53 and have "Reed LoRa 483d 20:23:42" in my found file. Coordinates: 40.8853578-119.0994615
William
 
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