New F-Impulse Record!!.........sort of/almost/not quite/maybe...........actually not.

[stealth6]

Well that didn't go quite as planned.

So, I've been keeping quiet about a project I've been working on for a long time. And that is to set a new F-impulse altitude record. I've had this in the works since last summer. My reasons for keeping quiet are many, but one of them was Steve Boetto's own project to do the same. I had been watching his thread, and my own projections/sims were showing quite a bit more altitude that he was going for (and ultimately achieved). I didn't want to rain on his parade, as his own project and results were impressive. He ultimately grabbed the TRA record at 5407', which is very cool.

So. I got the bug to try this last spring, and started by blowing through all kinds of designs/ideas/sims and such. As time went on, I kept refining it over and over until my sims started to show some pretty impressive possibilities. Then I started building. I kept refining, and refining, eeking out a few more feet of (simmed) altitude here and there. By the late fall I was essentially ready to fly. But then came trying to be at a suitable club launch to make the attempt, and I kept missing my chance. All the while, I continued to refine, tweak, sim, ground test, flight test, etc. and I kept gaining a few more (simmed) feet along the way. I was using both RockSim and RASAero, and once the rocket was built I was able to get super accurate sim files, at least in terms of measurements and such. Eventually I was getting reasonably consistent sims from the two programs, enough so that I was pretty confident in them.

My motor(s) of choice were a CTI F30-W (longburn) which gave the best results on the sims, but I was a bit leary of the offset core, and a CTI F51-CL which came pretty close. The worst sim, all things considered was 6999' and the best on was over 7300' - at the launch site altitude I was going for. These were all good enough to easily set a new record for both Tripoli (my first choice) and NAR (which I decided to submit for as well).

So today was flight day.

Annnnnnnnnnnnnnnd.......as mentioned above, it did not go as well as planned. Had PERFECT weather and conditions, so that was good. Prep and assembly (which were very tricky) went fine. My custom built launch tower went up no problem. Ignition was fine, and the flight up looked excellent. I used a sparkle streamer, and was able to get visual lock at apogee (with binoculars), and follow it all the way to the ground.

Or so I thought. Once I went to retrieve it, my radio tracking was acting odd. It seemed the closer I got to where I "saw" it land, the weaker my beacon got, and in fact lost it altogether. After some time walking around, I headed back towards the flight line. Halfway back the radio signal returned and I started tracking. It didn't make sense as it kept pointing me in the direction of the launch pads and/or the flight line. Hmmmm.....did someone pick up the rocket? Was someone else using their own tracker and happened to match my frequency? And then it hit me......I bet the streamer actually detached from the rocket and THAT is what I "saw" landing. Sure enough, I tracked via radio only and found the rocket in minutes pretty close to the launch pads....with no streamer attached.

So I brought it back to the van, and attempted to download the flight report. When I got the real bad news ....... the altimeter glitched and did not record the flight. Well, it did record, but it said that I flew to a maximum altitude of 43 feet. Not good.

So. No record for me this time. It sure looked like it could have flown to 7000' but I'll never know. Will have to make another attempt, which likely won't happen till midsummer at best, more likely late fall. In the meantime, I'll tweak and refine more and more I'm sure. And if I fly at higher launch ground level (like Hartsel Colorado), I may be able to shoot for as much as 8000'.

Oh well. Still was a good day on the launch field.....saw a few TRF folk including Aksrockets, Kenstarr, 75Grandville, Aerostadt. Plenty of great flights, and perfect weather. There are worse ways to spend the day.

I'll post bits about the rocket itself in another post.

ssix

 

[stealth6]

Ok, some bits about the "flight vehicle":

Here's some pics:



What you are seeing......

The fincan is all carbon fiber. I used a Soller Composites sleeve for the airframe (single thickness...VERY thin). The fins are five layers....two unidirectional perpendicular to the root, and three plain weave. This is a 24mm minimum diameter so not TTW of course.

The nose cone started out as a fiberglass 5:1 Von Karmann from Carolina Composites. I added a couple inches of (carbon) airframe to the shoulder, and glued in a new shoulder (made from CA soaked paperboard), in order to give enough room for my radio antenna, and to bring the airframe break farther back from the tip.

You know how RockSim has one surface choice as "polished"? Did you ever wonder how that was different than "gloss"? Well this is polished. I spent a lot of time hand polishing for an ultra smooth surface.

I filed the rear closure (CTI 24mm case) such that it is both smoother transition from the airframe edge, eliminates (most of) the knurling, and provides a small bit of "tailcone". The motor is friction fit.

The nose cone base has a short wooden plug (held in by counter-sunk screws) that the ejection wire run directly through. The altimeter is held in place simply by the terminal block/wires. It's small and light enough that this works. Also, the inside of that nosecone is such that this thing ain't going nowhere once it's all closed up.

Harness loops are kevlar cord epoxied in place (to the charge well on the motor for the aft end).

Recovery is by my own custom sparkle mylar and ripstop nylon streamer.

The altimeter is an AltusMetrum Telemini V1, which also provides RDF tracking. All in a VERY tiny and lightweight unit. LiPo battery of course.
I also had room to stuff in the guts of an Altimeter3 in there (which in practice failed to work).

One other item in that nosecone is a piece of taped up rubber. I actually made the rocket too light (for optimum mass) and had to ADD weight! This was the heaviest material I could find that wouldn't mask the antenna signal. It's also easy to cut exactly to size for the perfect mass.

Lots more details if you care for them, but it's late and I'm going to sleep.
I'll post more later perhaps.

ssix

 

[stealth6]

Oh, and Steve B. (n27sb), now that my secret is out.........

Your record is safe for now, but I'm gunning for it! I'm most definitely going to keep trying on this, and if things do eventually "go as planned", 5407' ain't going to hold. It will be a while until I can make another attempt, so I hope in the meantime you are also making plans and refining your game. Let's see where we both can push this thing.

ssix

 

[aerostadt]

Sorry to hear about the problems, Stealth. I remember you saying that the tracker was leading you back to the flight line and announcing with the LCO microphone if anyone had a beeper with a similar frequency. It is amazing that the electronics were telling you the truth all the time. You now know that your tracker works good and you are using it correctly. I assume that you made the long road trip from the southern Utah to make this flight. There was a fair amount of pent-up launch fever today with a lot of flights.

 

[Ted Cochran]

Good luck on your next attempts. Rules for setting NAR records are here:
https://www.nar.org/contest-flying/...ited-states-model-rocket-performance-records/

 

[stealth6]

Ted, I'm assuming that my altimeter would NOT qualify for a NAR flight, yes?

Reasoning is that the Telemini V1 unit itself does not display data (via LED, beeper, or screen), but rather has to be read via a radio link to the TeleBT or TeleDongle which in turns hooks up to a computer or Bluetooth device.

It's too bad because for performance optimization, it really is the only altimeter that will work in this rocket.

Hence the reason for me to submit to TRA instead of NAR.

ssix

 

[tim cubbedge]

Sorry to hear about your altimeter issues. What does it weigh without the motor? Good luck on next attempt! I have passed this on to Steve B. I think he has another record attempt on his calender but the weather hasn't been too favorable for flying such a light rocket!

 

[mikec]

I'm assuming that my altimeter would NOT qualify for a NAR flight, yes?

NAR records have to be set using an approved altimeter, see the rightmost column at https://www.nar.org/contest-flying/...appendix/altimeters-approved-for-contest-use/

Neither the Telemini nor the Altimeter-3 appear on this list at present.

 

[markkoelsch]

That NAR list seems a bit out of date. Many new altimeters are not there- why?

 

[mikec]

That NAR list seems a bit out of date. Many new altimeters are not there- why?

IMHO, a nebulous process for approval, lack of clear responsibility for who does the testing, skepticism from the old school theodolite tracking camp, and some ongoing controversy/misunderstanding about the technical details of how altimeters work.

Also keep in mind that NAR only provides for records through G impulse, so if you want an HPR record, TRA is your only option.

 

[terryg]

That NAR list seems a bit out of date. Many new altimeters are not there- why?

+1 Many altimeters on the list are not even made anymore. The Stratologger CF is the current model and the Stratologger is not available.

 

[jsdemar]

NAR records must be set at a NAR sanctioned contest meet or records trial.
The approved altimeters are a fairly small subset of all altimeters, due to (1) needing to report without downloading to a computer, (2) <2% accuracy to the standard US atmosphere model, (3) the manufacturer has to be in production (readily available to everyone, similar to the NAR contest rule for motor availability).

TRA records rules allow any commercial altimeter for <30Kft flights, and approved GPS units for >=30Kft flights.
https://www.tripoli.org/Records/Rules

The commercial motor can't be modified. The machining of the CTI closure would probably disqualify the record.

 

[manixFan]

...I filed the rear closure (CTI 24mm case) such that it is both smoother transition from the airframe edge, eliminates (most of) the knurling, and provides a small bit of "tailcone". ..

While I'm doing the same thing for a 38mm sustainer vehicle, I agree with John that this would invalidate your flight for a record attempt. Starts that whole 'slippery slope' thing as to what counts as a modification of the motor. While TRA is a lot less 'pink book lawyerly' than NAR, there still are rules. I don't think anyone would have an issue with the recovery harness being glued directly to the motor, but hard to say. Someone could make a case that it is a modification. I don't see that as the same as machining the closure.

Nice build overall though, I like a lot of what you did.


Tony

 

[kenstarr]

Super glad you got your rocket and altimeter back! I must have tracked that streamer for 10 minutes! Better luck next time. It was great you could come up to the launch. Weather couldn't have been any better.
-Ken

 

[n27sb]

Nice rocket, glad you had a nice day for your attempt. As you found out there are many Demons out there on High. I still plan on launching mine again on a good day.
Good luck on your next attempt.

 

[John Beans]

Did you add venting for your electronics?

 

[Gus]

IMHO, a nebulous process for approval, lack of clear responsibility for who does the testing, skepticism from the old school theodolite tracking camp, and some ongoing controversy/misunderstanding about the technical details of how altimeters work.

Also keep in mind that NAR only provides for records through G impulse, so if you want an HPR record, TRA is your only option.

The NAR contest board chair is responsible for testing altimeters so if there's something you'd like to see tested and added to the list, just send a request.

As for "ongoing controversy/misunderstanding about the technical details of how altimeters work," nothing could be further from the truth. Those of us who repeatedly and frequently fly altimeter altitude in U.S. and international competition understand VERY clearly the limitations of altimeters. U.S. expertise, the same that guides the NAR policies, is considered the world leader in making altimeter altitude contests as reliable as possible.

The F.A.I., which arbitrates all international aeronautical records, takes the issue of contest altimeters VERY seriously. They just completed a year-long review of the subject but have yet to publish new rules. Suffice to say, the F.A.I. Spacemodeling Altimeter Altitude rules are FAR more restrictive than any U.S. rules and currently only one altimeter meets those rules. F.A.I. contest rules require all altimeters to be tested and certified prior to each contest and the ambient temperature is programmed into each altimeter prior to each individual contest flight. Altimeters are zeroed and read by contest staff, not the flier. Virtually all of the F.A.I. rules were created with the guidance of the U.S. Indeed, two years ago at the European Championships there was a question of faulty altimeter data and the contest judges asked the U.S. team members (who were just there flying for practice) to help decide because we are seen as real experts in the field.

As for U.S. records, be aware that NAR rules for altimeter records are more stringent than those for altimeter contests. Altimeter records must be attempted at an approved contest and recording altimeters from the NAR approved list must be used. Altimeters used for contests need not be recording altimeters. The NAR rules were created to strike a balance between accuracy and ease of use. The idea was to promote more altitude contests by using altimeters instead of optical tracking. But there was also the realization that records should require a higher level of verification so recording altimeters are required.

Of note, the latest NAR postal altitude contest (where contestants flew wherever they lived and mailed in their results) adjusted each contestant's final altimeter reading based upon launch site altitude.

Overall, the NAR has put a ton of time and effort into creating fair standards for the use of altimeters in contests. As someone who routinely flies these contests, with some of the best altitude fliers in the world, I am VERY impressed with what the NAR has done. And my hat is off to people like Trip Barber and others who volunteer huge amounts of time to keep up with technology changes and adjusting policies accordingly.

Steve

 

[markkoelsch]

NAR records must be set at a NAR sanctioned contest meet or records trial.
The approved altimeters are a fairly small subset of all altimeters, due to (1) needing to report without downloading to a computer, (2) <2% accuracy to the standard US atmosphere model, (3) the manufacturer has to be in production (readily available to everyone, similar to the NAR contest rule for motor availability).

TRA records rules allow any commercial altimeter for <30Kft flights, and approved GPS units for >=30Kft flights.
https://www.tripoli.org/Records/Rules

The commercial motor can't be modified. The machining of the CTI closure would probably disqualify the record.

John, let's take Missileworks for example. They certainly are in production, but the two models listed have been out of production for quite some time. The RRC2 rev d has to be 12-14 years old and has not been made or available in quite a long time. It is easy to get a RRC2+ though.

 

[mikec]

As for "ongoing controversy/misunderstanding about the technical details of how altimeters work," nothing could be further from the truth.

There has been a lively debate on Contestroc for several months about the current set of proposed rule changes regarding altimeter use that would seem to contradict this.
https://groups.yahoo.com/neo/groups/contestRoc/info

 

[Bat-mite]

So frustrating! My condolences.

 

[Gus]

There has been a lively debate on Contestroc for several months about the current set of proposed rule changes regarding altimeter use that would seem to contradict this.
https://groups.yahoo.com/neo/groups/contestRoc/info

Oh my goodness, the ContestRoc discussion is a prime example of why the U.S. leads the world in the understanding and improvement of altimeters for model rocketry. The discussion you linked to is way beyond the understanding of 98% of the people on this forum or who, even routinely, fly altimeters. Fortunately we have incredibly bright people like the two in that discussion to create and guide our policies.

In the words of Dan Wolf (a member of the contest board),

"What I believe we want is "as good as is reasonably achievable". The membership asked for altimeters to be used for NAR contests. The NAR BoT asked the NAR CB to make it so. So it isn't a question of whether or not altimeters are good enough. The question is what is the best way to implement it. We will implement it (already have). Field data so far suggests no major issues. The 2 NARAMs that have used it, it worked okay. Was it perfect? No. But neither is tracking or we wouldn't have had NARAM 25 with Al Nienast's impossibly high Eggloft Altitude flight or similar Trip Barber flight at NARAM 30. There are probably more eamples of that than we care to admit. We do the best we could with optical tracking and accepted these tracking anomolies. What other options do we have? Most contestants accept that. Yet we seem to want to hold altimeter altitude to a significantly higher standard.

So, I don't think it is a black and white issue of whether or not altimeters are good enough. All the data we have collected so far, through numerous R&D reports, contest data, and sport flying, indicates that the performance level is as good or better than optical tracking. If anyone really had concerns, why haven't they submited an RCP to have altimeter altitude removed from the rules? I don't see a ground swell of support for staying with optical tracking. In fact, the masses seem to be leaning the other way."

I don't mean to hijack this thread, but felt obligated to correct the incorrect impression that somehow we, in the U.S., don't really understand what we are doing when it comes to model rocketry altimeters. We are really, really good at this, which is why we have so many manufacturers of everything from simple altitude reporters, recording altimeters, incredibly complex deployment altimeters with real-time broadcasting, as well as altimeter-based chute-release products, etc. This is something we in the U.S. rocketry community should be very proud of, and that the NAR deserves a lot of credit for helping nurture.

Steve

 

[jsdemar]

I don't mean to hijack this thread, but felt obligated to correct the incorrect impression that somehow we, in the U.S., don't really understand what we are doing when it comes to model rocketry altimeters. We are really, really good at this, which is why we have so many manufacturers of everything from simple altitude reporters, recording altimeters, incredibly complex deployment altimeters with real-time broadcasting, as well as altimeter-based chute-release products, etc. This is something we in the U.S. rocketry community should be very proud of, and that the NAR deserves a lot of credit for helping nurture.

Yes, a lot has been done to find a compromise to allow baro altimeters to be used in NAR contests. But, the NAR has been selective in accepting the input of people who have expertise in the field. Both the Physics of the atmosphere under real conditions, and the practical limitations of how they're designed and used, have a wide combined error margin. The current rules tweaking is in the noise and not worth the added burden. Considering that altimeters were supposed to make it easier than optical tracking, we don't want to add extra equipment and calibration steps. Might as well set up trackers, saving flyers a lot of money and headache.

 

[stealth6]

Did you add venting for your electronics?

Yep, venting happened, and was up to spec.

The problem was a bit of "operator error". As can be seen in the photos, I pulled the altimeter/screen/battery out of it's case and stuffed that into the nosecone. This was a tricky operation, and in ground testing I found that the switch (which was now exposed of course) could be bumped which would turn the unit off. I fidgeted with it many times to get my stuffing method "just right" to avoid this, but it was still not 100 percent reliable. And sure enough, on launch day it seemed as if I somehow screwed it up a bit and the unit got shut off. I'll need to refine my methodology a bit further.

That said, I also did have some issues with Bluetooth connectivity at times (during all the initial ground testing leading up to launch day). I found that sometimes it had to "search" for quite a long time to connect, and occasionally refused to connect at all unless I powered it all down and started from scratch. I thought at first that it might have to do with being inside the nosecone, which shouldn't be a problem but it was one possibility to explore. However, I found that the problem occurred with the unit in the cone, out of the cone, in or out of the case, if the "receiver" (which in this case was a Motorola MotoG Android device) was close or far away, etc. In short, there didn't seem to be any particular pattern or rhyme/reason for the difficult connection - it just found it hard to accomplish sometimes. I did have some problems along this line just before going out to the launch pad as well.

But the MAIN problem seems to be my fault......ie, inadvertently switching the dang thing off!

I likely won't be using this on future record attempts. No fault of it's own, but neither NAR nor Tripoli will recognize it for actual record attempts so it's really just along for the ride and not serving any "mission critical" function. It will most certainly fly in many rockets otherwise, as it's a great little unit that does it's job well (as did my now sadly lost Altimeter2).

ssix

 

[stealth6]

Nice rocket, glad you had a nice day for your attempt. As you found out there are many Demons out there on High. I still plan on launching mine again on a good day.
Good luck on your next attempt.

And I don't even need those demons.....I'm perfectly capable of screwing up all by myself without their interference!

Can't wait to see what tweaks you've been making, and where in the sky they take you next. Please post and report.

And best of luck to you on your next attempt as well (but please leave me some room up there, at least until I can get a successful flight in). Let's see together where we can push things to.

ssix

 

[stealth6]

Nice rocket, glad you had a nice day for your attempt. As you found out there are many Demons out there on High. I still plan on launching mine again on a good day.
Good luck on your next attempt.

If you care to, it might be interesting for us to exchange "launch conditions" - altitude of ground level, temperature, humidity, cloud cover, etc. on the days of our actual successful flights. That might give us some info such that we could compare things on something of a "level playing field". Meaning we could each extrapolate the results of our own actual altitudes compared to our sims, then rerun those sims with "the other guys conditions", and get something along the lines of an actual comparison of the two rocket's results. This might be a way that we could, in a virtual sense, launch on the same day and place.

Of course I need an actual successful flight first! But it still might be interesting.

ssix

 

[n27sb]

You may have shed your streamer Because of an early deployment. Did you use motor eject? In every case I found that a delay of up to 15 seconds is needed. I use the Easymini because of its size and features. The Eggfinder GPS is a bit heavy compared to other tracking options but it is bullet proof. My rocket could be lighter if I made changes to those choices but there are many ways for a flight to come up short. Construction, Flight prep, Launch conditions, Launch, Flight and recovery all have to go perfect for a record flight. I think my flight was probably about 80% of those conditions. Let's also remember that there is also a variation in performance from engine to engine. Keep up the good work and you will get there.