Double Negative 2020: A Black Rock High Altitude Project

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OverTheTop

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If you are using a TeleMega you can parallel up multiple output channels to trigger on different parameters. I used this method for my HEI. One channel was set to trigger on a timer after booster burnout, the other channel was set to trigger if the tilt got to a set tilt (15deg I think). So a straight flight would trigger on timer, and a tilting flight would trigger on tilt. Whichever comes first wins. The tilted flight would not achieve as much altitude but staging could still be executed safely. Both of those channels had lockouts to prevent ignition if tilt exceeded a wider trip level.

On another note, the TeleMega has four additional output channels. If you don't use them for outputs you can use them as analog inputs for monitoring all sorts of other things. Power supplies on the other altimeters is what I used them for. I have also used them to log analog servo voltages on my Vertical Trajectory System, allowing an all-in-one logging system.
 

Cameron Anderson

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Absolutely post the final parameters that you end up using - I don't use the tele-series, but I use a Raven.
 

JimJarvis50

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I typically use a timer for apogee deployment. If you are off a little, it doesn't matter, and with a timer, something will ignite the apogee charges for sure. I think it is important to have a timer "hail Mary" even if you are planning on something else to actually do apogee.

I also use barometric apogee if the altitude is below 90K feet. This is in case a motor doesn't light or there is some other problem. The raven and telemega will read higher than that (see the attached pics for examples to 118K and 175K). Both of these flights were via timer, and you can see that it did pretty well. Note the effect of the tumbling on the EasyMega graph that started around 140K.

The EasyMega program that I used for the three stage flight to 175K is also attached. There are some things there that won't apply to you, but the programming for staging has a few things you might note, and there is the programming for the 90K baro backup.

You may be fairly limited on the Raven unless you have the high altitude firmware (although I have to say I'm not sure what the capabilities are of the current model).

Jim

Raven data.jpg
Third stage pic 081118.jpg
MEGA altitude.jpg
 

AndrewW

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I typically use a timer for apogee deployment. If you are off a little, it doesn't matter, and with a timer, something will ignite the apogee charges for sure. I think it is important to have a timer "hail Mary" even if you are planning on something else to actually do apogee.

I also use barometric apogee if the altitude is below 90K feet. This is in case a motor doesn't light or there is some other problem. The raven and telemega will read higher than that (see the attached pics for examples to 118K and 175K). Both of these flights were via timer, and you can see that it did pretty well. Note the effect of the tumbling on the EasyMega graph that started around 140K.

The EasyMega program that I used for the three stage flight to 175K is also attached. There are some things there that won't apply to you, but the programming for staging has a few things you might note, and there is the programming for the 90K baro backup.

You may be fairly limited on the Raven unless you have the high altitude firmware (although I have to say I'm not sure what the capabilities are of the current model).

Jim

Thanks for the very thorough and informative reply Jim!

That gave me a much better feel for what works and definitely answered a few questions. I am currently working on the settings now and will post ehm here when I get them done. Any feedback would be greatly appreciated.

I think the Raven should be able to be set up in a similar manner. I am going to reach out to Adrian but I believe the high altitude firmware was actually just a bug in earlier versions if the altimeter went above 65,000' Something about a sign error in the code if I recall correctly. I will post those settings as well.

Andrew
KD2RPB
 

AndrewW

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If you are using a TeleMega you can parallel up multiple output channels to trigger on different parameters. I used this method for my HEI. One channel was set to trigger on a timer after booster burnout, the other channel was set to trigger if the tilt got to a set tilt (15deg I think). So a straight flight would trigger on timer, and a tilting flight would trigger on tilt. Whichever comes first wins. The tilted flight would not achieve as much altitude but staging could still be executed safely. Both of those channels had lockouts to prevent ignition if tilt exceeded a wider trip level
On another note, the TeleMega has four additional output channels. If you don't use them for outputs you can use them as analog inputs for monitoring all sorts of other things. Power supplies on the other altimeters is what I used them for. I have also used them to log analog servo voltages on my Vertical Trajectory System, allowing an all-in-one logging system.
These are some great ideas. I am not sure if I will have any channels free or additional sensors on board but I will definitely keep it in mind for future flights.

Thanks again,
Andrew
 

JimJarvis50

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Thanks for the very thorough and informative reply Jim!

That gave me a much better feel for what works and definitely answered a few questions. I am currently working on the settings now and will post ehm here when I get them done. Any feedback would be greatly appreciated.

I think the Raven should be able to be set up in a similar manner. I am going to reach out to Adrian but I believe the high altitude firmware was actually just a bug in earlier versions if the altimeter went above 65,000' Something about a sign error in the code if I recall correctly. I will post those settings as well.

Andrew
KD2RPB
Sure. Post a screen shot of your program and we can review it.

The high altitude firmware is something that is installed custom so that Ravens can operate at higher altitudes and for longer times. I am not sure of the specifics just now, but for example, if you want the timer function to operate for more than 30 seconds or so (say, 100 seconds), you need the high altitude firmware. Same if you want to have deployment functions happen over 30K or so. I have a Raven that has the firmware installed, but my info on the limitations is approximate and the situation with them could have changed over the last few years. But, don't assume your Raven will do it's thing at high altitude - check it out.

The Raven "bug" has a special place in my heart. I had a flight in 2011 where I was the first to encounter it. At 66K or so, the rocket thought it was underground. The permissives to fire all of the charges - all of them - occurred at around 98K or so, while the rocket was still going well above Mach 1. Things went bad after that, but the nosecone went verifyably above 100K - woohoo! Adrian found the sign error and to his credit immediately posted about it. He felt bad for sure, and so did I, as the bug cost me the Carmack prize (probably). Stuff happens. But, the high altitude firmware and the Raven bug are not the same.

Jim
 

AndrewW

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The Raven "bug" has a special place in my heart. I had a flight in 2011 where I was the first to encounter it. At 66K or so, the rocket thought it was underground. The permissives to fire all of the charges - all of them - occurred at around 98K or so, while the rocket was still going well above Mach 1. Things went bad after that, but the nosecone went verifyably above 100K - woohoo! Adrian found the sign error and to his credit immediately posted about it. He felt bad for sure, and so did I, as the bug cost me the Carmack prize (probably). Stuff happens. But, the high altitude firmware and the Raven bug are not the same.
I recall reading about that both in the LDRS book as well as on this forum. That must have been heart breaking.

Your post is quite is quite timely as I am going through the Raven right at this moment and I am definitely seeing some limitations regarding the timer functions and high altitude operation. Thanks for the info on the special firmware I will get in touch with Adrian and try to get the specifics.
 

cerving

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How long is it going to take you to get to 90K?
 

AndrewW

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How long is it going to take you to get to 90K?
I don't have the sim in front of me at the moment but I think it was about 45 seconds to 100k' and 100 seconds to apogee. So approximately 40-42 seconds.
 

JimJarvis50

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I recall reading about that both in the LDRS book as well as on this forum. That must have been heart breaking.
It was not a happy moment when we got to the landing spot and all that was there was a nose cone. We walked 10 miles, tried to find the rocket from a plane. No dice. But the truly heartbreaking thing was that it was my first rocket where Tony didn't recover the pieces. It's still out there, waiting for him, and I have no doubt that someday he will find it.

Jim
 

OverTheTop

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These are some great ideas. I am not sure if I will have any channels free or additional sensors on board but I will definitely keep it in mind for future flights.
You will find it very reassuring to know what the supplies on your other altimeters are at before launch. I run the TeleMega in the nosecone and Ravens in the main AV bay. A pluggable wire connects them during flight, The advantage of this is I also get a signal confirming nosecone deployment :).
 

AndrewW

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It was not a happy moment when we got to the landing spot and all that was there was a nose cone. We walked 10 miles, tried to find the rocket from a plane. No dice. But the truly heartbreaking thing was that it was my first rocket where Tony didn't recover the pieces. It's still out there, waiting for him, and I have no doubt that someday he will find it.

Jim
I am sure someone will someday.

It is something I truly find fascinating about rocketry. We spend enormous sums of money, spend ridiculous amounts of time and pour our hearts and souls into some of these projects only to subject them to such an extreme test with a high probability of failure. But that is why I love it. The ability to overcome problems and hopefully someday succeed in reaching an objective is what keeps me going and motivates me to set higher and higher goals.
 

tfish

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Jim..it's just a matter of time..

If I didn't get butterflies and get all nervous prior to my flights...I wouldn't be doing it.

I've had some great adventures looking for rockets with my kids, Jim Jarvis, Curt von Delius and a few other folks that have been mostly fun.

Tony
 

Tim51

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I am sure someone will someday.

It is something I truly find fascinating about rocketry. We spend enormous sums of money, spend ridiculous amounts of time and pour our hearts and souls into some of these projects only to subject them to such an extreme test with a high probability of failure. But that is why I love it.
There's a theory by a very famous psychologist that particular impulse starts when we're very, very young 😊:
Thanks for the inspiring thread.
 

JimJarvis50

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I am currently working on the settings now and will post ehm here when I get them done. Any feedback would be greatly appreciated.

Andrew
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I suggest that when you post your program, that you also post the flight plan (i.e., a graph that shows velocity and altitude versus time for the flight you want to have).

Jim
 

AndrewW

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I suggest that when you post your program, that you also post the flight plan (i.e., a graph that shows velocity and altitude versus time for the flight you want to have).

Jim
I definitely will.

Now that I am done fabricating most of the significant components I have started to go back through the sims in OR and RasAero to fine tune all of the mass and CG values. This is part of the reason why I left the fins for last as I plan on sizing them to trim stability as needed.

I am waiting to hear back from Adrian regarding the Raven and high altitude operation. I did find a possible way to use the max TVal time in combination with the Delay after other conditions are met to give me the approximately 100 seconds I need for apogee timer deployment. But I will wait to get his input to see if this is viable or not.

Andrew
 

JimJarvis50

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I definitely will.

Now that I am done fabricating most of the significant components I have started to go back through the sims in OR and RasAero to fine tune all of the mass and CG values. This is part of the reason why I left the fins for last as I plan on sizing them to trim stability as needed.

I am waiting to hear back from Adrian regarding the Raven and high altitude operation. I did find a possible way to use the max TVal time in combination with the Delay after other conditions are met to give me the approximately 100 seconds I need for apogee timer deployment. But I will wait to get his input to see if this is viable or not.

Andrew
I often suggest to people to trim their fins after they know the actual weights. I have some odd-looking fins, but it gets you to the right spot in the end.

Adrian will probably suggest using barometric deployment plus a delay. He can tell you roughly how early barometric deployment will be, so that you know what the delay should be, but it is sort of a guess since it involves both altitude and velocity. It's not a bad approach when you work through the scenarios.

Jim
 

mikec

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Adrian will probably suggest using barometric deployment plus a delay.
Barometric or accelerometer? I'd have said accelerometer, above 100k the pressure sensor is just producing noise, I thought.

Air's so thin at these altitudes that an early or late apogee deploy shouldn't matter that much.
 

Cameron Anderson

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Barometric or accelerometer? I'd have said accelerometer, above 100k the pressure sensor is just producing noise, I thought.

Air's so thin at these altitudes that an early or late apogee deploy shouldn't matter that much.
I think the issue is the timer doesn't have enough range if it's started at launch to time all the way to apogee and control an event. By using the baro sensor to trigger the timer at say, 60,000 feet on ascent, where there is still good pressure fidelity, you can then use the timer, and use it more accurately, to time the flight to apogee and not exceed it's range since it's starting from a later point in flight.
 

JimJarvis50

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Barometric or accelerometer? I'd have said accelerometer, above 100k the pressure sensor is just producing noise, I thought.

Air's so thin at these altitudes that an early or late apogee deploy shouldn't matter that much.
Adrian would suggest barometric apogee plus a delay. The theory is that barometric apogee will be early because there is a declining difference in successive barometric readings, and at some point, the difference is small enough that the altimeter detects apogee even though the rocket is still going up. Hence, you add a delay of some number of seconds. Conceptually, I don't see this as all that much different than using a timer from launch. So, I never used this method. I believe the use of this method still relies on having the high altitude firmware since the point where barometric deployment would be "early" is still well above the 32K Raven limit.

See the graphs I posted earlier regarding the pressure sensor readings at high altitude. They are not all that bad; however, that doesn't mean that they can be used for barometric detection because of the rate of change issue.

I think the issue is the timer doesn't have enough range if it's started at launch to time all the way to apogee and control an event. By using the baro sensor to trigger the timer at say, 60,000 feet on ascent, where there is still good pressure fidelity, you can then use the timer, and use it more accurately, to time the flight to apogee and not exceed it's range since it's starting from a later point in flight.
I don't think that barometric plus timer will work without the high altitude firmware, but it depends on the flight. I believe the max altitude for a trigger is about 32K and the timer is listed as max at 51 seconds. So, if you want to trigger at 32K and apogee is at less than 51 seconds later, this could work (but it seems like a workaround to me).

Jim
 

mikec

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I think the barometer filtering might have been different for the high-altitude firmware.

FWIW, a Raven setting I tried to use on a 100K+ flight with the regular firmware was

1st/apogee: velocity < 400 fps, pressure increasing, height above pad < AGL1 32000
3rd: after burnout of motor 2, velocity < 0, delay 10 seconds
(10 seconds was 2 second delay to keep from firing at same time as a Telemega plus 8 seconds of slop for accelerometer error.)

and then those channels were strapped together. Chan 1 was intended to fire if the second stage didn't ignite, chan 3 if it did.

We had a first-stage CATO and but this did fire at apogee (and then things went further downhill and we ended up digging it out of the playa for the rest of afternoon; Raven was trashed so I don't have the flight data.)
 

AndrewW

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Great Discussion on the altimeters guys! Thanks for all the input so far.

While I am waiting for a response from Featherweight I figured I would go over some more aspects of the build. So one of the team members came over yesterday and we decided to tackle the some of the work on the fins. Covid-19 has definitely added to the list of challenges on this project and this is the first time any of us have gotten together physically since march. We did our best to maintain social distance and wear face coverings when needed.

So about the fins. The original design called for G-11 FG but over time we changed our minds and upgraded to CF especially for the Sustainer which will likely spend a bit of time above M3. So Fin flutter was a concern for those fins. As far as the booster goes it will not be going significantly above M 1.3 so flutter is not as much of a concern but the advantage of CF here came from taking some weight out of the back end to aid in moving the CG forward a little bit. We decided on Dragon Plate as a vendor and ordered their Quasi Isotropic Pre Preg plate for the sustainer fins with peel ply texture on both sides and their 0-90 economy plate for the booster fins again with peel ply texture on both sides.

We cut the fins using a diamond blade wet saw which worked extremely well as long as you ran the water. We then trued up the edges with a belt sander. Finally we beveled the leading and trailing edges on a router table with a carbide burr. This is the first time I have used this method and after some practice and a little fine tuning I must say I am impressed. I know I got the idea from this forum but I unfortunately cannot remember from who. So if you are the first person to come up with this idea and posted it here I thank you. One other thing that aided in making nice consistent bevels was the addition on an aluminum angle straight edge and a little bit of soap as a lubricant. Additionally the vacuum not only helped in removal of dust but it also helped pull the fin tight against the fence.

Thanks,
Andrew
KD2RBP

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AndrewW

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One other thing to mention is that we made the fins a 1/4" and 1/2" greater in span on the sustainer and booster respectively to allow for some fine tuning of the CP if needed after everything is together. This will be done with a jig and a milling attachment on a lathe.

One issue we have not settled on yet is leading edge treatment. We are planning on doing a CF tip to tip layup on these and have been kicking back and forth ideas regarding what to use to protect the leading edge. I had originally decided on using a SS cuff but they are proving to be difficult to manufacture at least the way I am doing it. We have also discussed using Cotronics and/or a cork ablative coating. Any input on this would be great.

Here are the fins minus the tabs that need to be milled out where they will interface with the slots in the airframe.

Thanks,
Andrew
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Chad

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i love projects like this!

take a look at this build thread i linked below, it's a 4" to 3" 2 stage that flew to 145k feet. The thread is a great reference and covers things from tip-to-tip carbon fiber reinforcement to motor selection to electronics config/placement and more.

 

cerving

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You can use baro to start the timer, maybe around 50K, once it's running then the baro is out of the picture so it doesn't matter that you aren't going to get any resolution out of the pressure sensor after maybe 70K.
 
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