“Risky Business” - Minimum Diameter mach 2 attempt

[James Owen]

My next HPR project is ambitious, to say the least.

There are a few aspects to the project:
A) send a scratch built rocket over mach 2 on an L1 motor
B) use a completely homegrown avionics + tracking system (I’m working on the necessary FCC stuff)
C) get it all back in one piece.

Current design is a minimum diameter 38mm rocket using a 2ft section of wildman G12-1.5 airframe+ wildman 1.5” nose cone, with airfoiled “bass-glass” fins (CNC cut and sanded to airfoil basswood, “painted” with wood glue, generous fillets, 2-4 layers of 6oz fiberglass). I plan to use home made fly away rail guides.
Deployment of the parachute will be done without any pyrotechnic charges because I was born too darn late and only have jr. L1 (but I have several flights’ worth of HPR experience, including 1 supersonic flight, and I plan to gain a lot more experience by the time this project is going up). Exactly how ejection will be done is undecided, I have a few ideas I’m going to test and see which works best.

Early openrocket “sketch” simulates 10,700’ and mach 2.2 on an I600 redline (one of my favorite motors, I’ve flown one of them so far but hope to fly many more because they’re awesome). First test flight to validate all the systems would be on an H100.

Recovery via a 24” top flight parachute and JLCR, located with a GPS tracker that will be thoroughly tested before being put on the “Risky Business”. Got a nice long Kevlar shock cord from GLR mounted on GLR’s 38mm shock cord hard point.
Avionics are kept mostly in the nose cone, meaning they have to be as small as possible. Going to order some custom PCBs and get lots of soldering practice…

Anyway, let me know what you guys think of this.
Happy rocket-ing!

 

[Handeman]

Sounds like a fun project. If you can keep the rocket under 18 oz. and have a 14K ft. waiver to play in, you should be able to hit that Mach 2 goal.

Good Luck

 

[James Owen]

Current Openrocket design - just updated it to match the latest details I have about the rocket. mach 2.17, just over 11,000ft. allowing for a 10% margin of error, that puts expected top speed between Mach 1.953 and 2.387. if I get my avionics readout a top speed of mach 1.95, i'll probably just call it good because that is darn close to mach 2. if it were left to random chance, this range makes it so its more likely to go over mach 2 than under, which I think is acceptable.
2.14 cal stability
1,671 mph
11,157 ft
94.8 G

 

[Seatechnerd83]

I'd suggest giving those fins a little bit more sweep... mach physics is weird, and if you give them a bit more sweep the cross section of the airframe will reduce more gradually allowing for, well, better aerodynamics, also I personally don't have any experience with RAS Aero, but I've heard simulating low-margin high-speed flights is alot better/more reliable with RAS.

 

[James Owen]

I'd suggest giving those fins a little bit more sweep... mach physics is weird, and if you give them a bit more sweep the cross section of the airframe will reduce more gradually allowing for, well, better aerodynamics, also I personally don't have any experience with RAS Aero, but I've heard simulating low-margin high-speed flights is alot better/more reliable with RAS.

Thanks for your advice! I’ll try to sweep the fins more without sacrificing stability or weight. I’ve used RASAero before, but for some reason didn’t think of that yet for this rocket. I’ll get that set up and put the results here.

 

[Art Upton]

I'd suggest giving those fins a little bit more sweep... mach physics is weird, and if you give them a bit more sweep the cross section of the airframe will reduce more gradually allowing for, well, better aerodynamics, also I personally don't have any experience with RAS Aero, but I've heard simulating low-margin high-speed flights is alot better/more reliable with RAS.

Back in the day for that I did use RAS Aero paid version. Worked well. I have forgotten everything I learned with it now Hi Hi

 

[diyaerospace]

use a completely homegrown avionics + tracking system (I’m working on the necessary FCC stuff)

Just make sure to turn them on this time

 

[James Owen]

Just make sure to turn them on this time

I’ll think about it…

 

[Hobie1dog]

post up some build pics for us and of the electronics too.

 

[James Owen]

post up some build pics for us and of the electronics too.

Will do. Ive got some of the parts and have some more ordered. I’ll keep you guys posted on the progress.

 

[bjphoenix]

What special provisions do you need for the heat of Mach 2? Will it melt fiberglass nose cones, G10 fins, etc.?

Also have you compared what you could do with 29mm motors? I know there are H motors available and Apogee lists an I motor.

 

[James Owen]

What special provisions do you need for the heat of Mach 2? Will it melt fiberglass nose cones, G10 fins, etc.?

Also have you compared what you could do with 29mm motors? I know there are H motors available and Apogee lists an I motor.

I’m going to give the whole thing a coat of paint that is supposedly designed for temperatures up to 600F, which should be plenty. We’ll see how it handles high temperatures with very fast relative wind too. This should help insulate the rocket a bit. I’m not worried about the parts themselves melting, more about protecting the parachute and electronics.

I’ve looked into the I205 as a potential motor, but it’s a baby I and and the results ended up being better with the 38mm I’s of higher thrust and impulse.

 

[Handeman]

After 14 years of reading the Mach threads on TRF, I don't think bare fiberglass is going to deteriorate enough on a quick flight to Mach 2 to really make a difference in the integrity of the rocket. It might not make a second flight to that speed, but it should be good for the first one.

Then again, that's just what I heard here. You can take that for what it's worth!

 

[diyaerospace]

Curious to see what sensors you use, not many accelerometers can accurately measure over 95G.
And barometers get messed up during transonic/supersonic flight.

Good Luck!

 

[Art Upton]

After 14 years of reading the Mach threads on TRF, I don't think bare fiberglass is going to deteriorate enough on a quick flight to Mach 2 to really make a difference in the integrity of the rocket. It might not make a second flight to that speed, but it should be good for the first one.

Then again, that's just what I heard here. You can take that for what it's worth!

I have had LOC 38mm Kraft tubing go Mach 1.7 on a J570; but the failure of the batteries to fire the ematch resulted in a Willie E Coyote dirt mushroom cloud on the Playa deck while the cardboard tube was driven into the playa and pushed the motor case up out the back of the rocket.

An associate I knew was filming it and said it was going to fold like a cheap $2 suitcase, but as it went up to apogee he said, WOW it did not fold.

I asked Sue who was tracking it in her Binos if she still had a fix on the rocket; she said yes but it's coming down as fast as it went up. Then the Dirt Mushroom cloud was seen.

Long story short, don't trust even 2 A23 to fire an ematch even if that is all you could find to use as a battery on the last EX day at XPRS; my tiny 357 pack I had built for some reason shorted out and drained on the trip.

Yes I was that FAT back then , not now.

PPS: that is standard yellow Krylon of the old formula back then on the body tube, not that there was much to analyze after the facts.

[And I was skinny all my life till about 2001 after I had quit smoking in December 1999]



Note , ACME Fin Can just put on LOC Tube and standard nose cone.

 

[James Owen]

Curious to see what sensors you use, not many accelerometers can accurately measure over 95G.
And barometers get messed up during transonic/supersonic flight.

Good Luck!

velocity and altitude data will be measured mostly via GPS, but a barometer should be able to measure the apogee (but it just wont be able to measure data all the way up). I don't know if i'll bother with accelerometers in a 95G flight.

 

[Seatechnerd83]

velocity and altitude data will be measured mostly via GPS, but a barometer should be able to measure the apogee (but it just wont be able to measure data all the way up). I don't know if i'll bother with accelerometers in a 95G flight.

Remember, GPS lockout occurs at like mach 1... so if you're going to mach 2... you're gonna have to anticipate GPS lockout.

 

[James Owen]

Remember, GPS lockout occurs at like mach 1... so if you're going to mach 2... you're gonna have to anticipate GPS lockout.

i actually didn't know this. based on a few quick google searches, all GPS devices lock at 1200mph to prevent them from being used in weapons. being that this rocket goes close to 1700mph means it would lose data entirely for a chunk of powered flight. that's an issue as I'd like to confirm the performance of my rocket. does anyone have ideas for other ways to measure the speed then?

edit: based on a few more searches, there are some companies which produce GPS modules that only lock out if they exceed 1200mph AND go above an altitude ceiling, usually 60k ft. I'm obviously not going anywhere close to that, so I might just have to find a brand that sells these and get one of those (that will likely be much more expensive though)

 

[diyaerospace]

I would say to buy a high gee accelerometer.
https://www.adafruit.com/product/5374This device measures up to +-200 gee. It drifts significantly though.

 

[Velocity Aerospace]

All this is significantly more important for me than I thought. I was following along just for fun, but sometime in the future, I want to do a Mach 1 flight, and all this discussion is really helping me understand just what I'll be getting into

 

[Handeman]

All this is significantly more important for me than I thought. I was following along just for fun, but sometime in the future, I want to do a Mach 1 flight, and all this discussion is really helping me understand just what I'll be getting into

Don't get too worried about Mach 1 flights. They really aren't that hard when you have 54mm large K and small L motors available for 3" and 4" rockets. They will even stay under most of the east coast waivers.

I eventually end up putting the biggest motor that will fit in each of my rockets. That usually ends up with a Mach1+ flight. I've never built a rocket just for Mach 1, but I've had a number of them just because I went for the "big" motor.

With that said, when you put constraints on the rockets and flights and still want to bust Mach or Mach 2, that is where the fun can begin.

 

[diyaerospace]

Interested in how you approach the telemetry system.

 

[James Owen]

Interested in how you approach the telemetry system.

On board code compacts the avionics data into a “packet” which is sent over a long range radio module about every half second or so. this packet includes the current altitude and speed, the peak altitude and speed so far, and the GPS lat/lon (if available). Exactly which module I’ll use for radio transmission is still undecided but I think I’ll order something soon.

 

[diyaerospace]

On board code compacts the avionics data into a “packet” which is sent over a long range radio module about every half second or so. this packet includes the current altitude and speed, the peak altitude and speed so far, and the GPS lat/lon (if available). Exactly which module I’ll use for radio transmission is still undecided but I think I’ll order something soon.

I am more interested in which radio modules you use. Generally you can buy cheap LoRa modules from Ebay. Although from my experience these devices are not very reliable. Someone with more experience in this field can give a better opinion.

Walter

 

[James Owen]

I am more interested in which radio modules you use. Generally you can buy cheap LoRa modules from Ebay. Although from my experience these devices are not very reliable. Someone with more experience in this field can give a better opinion.

Walter

I wasn’t planning on using any cheap eBay parts for this rocket. The avionics for this rocket will end up being the most expensive part, as it only cost me about $85 to get the nose cone, body tube, parachute, shock cord, and shock cord mount.

 

[Art Upton]

Look for LoRa modules from the reputable maker suppliers like Spark Fun or Ada Fruit. Avoid Ebay auction site.
You don't want a failure in that area.

 

[Seatechnerd83]

On board code compacts the avionics data into a “packet” which is sent over a long range radio module about every half second or so. this packet includes the current altitude and speed, the peak altitude and speed so far, and the GPS lat/lon (if available). Exactly which module I’ll use for radio transmission is still undecided but I think I’ll order something soon.

for telemetry, especially with high performance rockets, youre gonna want to constrict your packet size as much as possible, because losing telemetry is how you lose a flight, if your onboard antenna is very suboptimal to the ground youre gonna want the smallest packet size in hopes of getting one through, or you could code modes into your telemetry where, depending on connection strength, you switch between fat packets and skinny packets (Lat/long, current speed and maybe Alt. for the skinny packets, to determine A. where the rocket is, and B. if the recovery device has deployed.)

 

[James Owen]

for telemetry, especially with high performance rockets, youre gonna want to constrict your packet size as much as possible, because losing telemetry is how you lose a flight, if your onboard antenna is very suboptimal to the ground youre gonna want the smallest packet size in hopes of getting one through, or you could code modes into your telemetry where, depending on connection strength, you switch between fat packets and skinny packets (Lat/long, current speed and maybe Alt. for the skinny packets, to determine A. where the rocket is, and B. if the recovery device has deployed.)

Thanks for the advice. I like the idea of having alternating packets. Maybe I’ll have half the packets give nothing but GPS lat/lon and speed (like you said, this tells me where the rocket is and wether or not the chute is out), and the other half of the packets would contain the rest of the flight data (altitude, peak altitude and peak velocity so far, etc).

Also, while I’m on the forum thread, here’s an update on the progress:
I have started ordering parts for the avionics stack. Looks like it’ll be in the neighborhood of $100-150 for the bare minimum stuff (a pair of $25 LoRa transceivers, $25 accelerometer, $30 GPS module, the necessary antennae. I already have a few microcontrollers and barometers.) but for the sake of adding redundancy and reliability I may spend upwards of $200 on the avionics/telemetry system alone.

Recovery system parts have all arrived now and I did some dry fit testing of each of the parts together. Once I have a little more spending money I’ll order the rest of the parts for the rocket itself (wildman nose cone and body tube is all that’s left) and the rocket should start coming together fairly quickly.

First test flight may be able to happen this fall with some good luck, I already have an H169 (29mm motor) laying around so I might use a 29-38 adapter and do the test flight on this motor.

Not much to show in pictures right now but there should be soon.

 

[Seatechnerd83]

Thanks for the advice. I like the idea of having alternating packets. Maybe I’ll have half the packets give nothing but GPS lat/lon and speed (like you said, this tells me where the rocket is and wether or not the chute is out), and the other half of the packets would contain the rest of the flight data (altitude, peak altitude and peak velocity so far, etc).

Also, while I’m on the forum thread, here’s an update on the progress:
I have started ordering parts for the avionics stack. Looks like it’ll be in the neighborhood of $100-150 for the bare minimum stuff (a pair of $25 LoRa transceivers, $25 accelerometer, $30 GPS module, the necessary antennae. I already have a few microcontrollers and barometers.) but for the sake of adding redundancy and reliability I may spend upwards of $200 on the avionics/telemetry system alone.

Recovery system parts have all arrived now and I did some dry fit testing of each of the parts together. Once I have a little more spending money I’ll order the rest of the parts for the rocket itself (wildman nose cone and body tube is all that’s left) and the rocket should start coming together fairly quickly.

First test flight may be able to happen this fall with some good luck, I already have an H169 (29mm motor) laying around so I might use a 29-38 adapter and do the test flight on this motor.

Not much to show in pictures right now but there should be soon.

good luck with 38mm, 29mm is hell, 38mm has some room to work with. Currently doing a motor deploy mach buster "for fun" rocket with scrap 38mm tube and a GPS tracker. GLHF

 

[diyaerospace]

a pair of $25 LoRa transceivers, $25 accelerometer, $30 GPS module, the necessary antennae

Can you share what specific sensors are you using?