NARCON solves a mystery!

NAR's annual convention, NARCON, started on Friday afternoon and finished just a couple of hours ago. As usual, it was great - lots of informative and entertaining talks, good keynotes, socialization, and news from rocket vendors. But this year was special - COVID had eliminated the possibility of an in person NARCON, so the conference went virtual. This may have initially been met with trepidation, but the meeting was absolutely superb - not one iota decrease in quality - and best of all, a record 500+ people attended (as opposed to 100-150 for an in person NARCON). Not only was the attendance 4 times greater, but the virtual format had the advantage of eliminating one great problem experienced by past NARCON attendees. There are 3 parallel tracks, and you often had to make agonizing choices between two interesting talks held at the same time. This year, the conference vendor was making videos of the presentations available to attendees as soon as they were over, so you could go back at your leisure (up to a month from now) and catch up on the talks you missed. How cool is that!

Part of Saturday's NARCON schedule

So, what were the highlights? Well, I loved the manufacturing forum announcing the forthcoming goodies and the two keynote talks (on Osiris-Rex and commercial spaceflight). There were excellent video tours of LOC Precision, Kennedy Space Center, and the rocket capital of the world, Estes Industries. Among the talks, there was an outstanding video presentation by James Duffy on kit bashing common kits into works of art, some great tips on making and using decals by Randy Gilbert, and how to use and care for common rocket altimeters by Bernard Cawley. Because of the packed schedule I missed several good presentations, and I will be looking at those over the coming days. 

Alphas in WWII fighter livery (Click to enlarge).

Estes Explorer Aquarius with tanks painted to resemble freight cars (Click to enlarge).

And let's not forget Ed LaCroix's proposed logo for this year's NARCON...

Bernard's talk on altimeters solved a long standing mystery that has had me puzzled over several years. My altimeters often reported a sharp dip in altitude at ejection, indicating that the compartment with the altimeter was getting pressurized by the ejection charge. I figured it may have been due to too large vent holes in the payload section (altimeters need to sense the outside air to work properly, and vent holes are the easiest way to accomplish this). So I made my vent holes smaller, but the dip remained, showing up in flight after flight. I had resigned myself to living with it, but in his talk Bernard pointed out something that was so obvious I was kicking myself for not thinking of it.

Balsa is a very porous wood.

I use balsa couplers at the rear of my payload sections to connect them to the rest of the rocket, and so the ejection gases were flowing through the balsa into the compartment, spiking the pressure. The vent holes quickly allow the pressure to drop, but not before the altimeter records the spike as a sharp decrease in altitude. Simple, and you fix it by sealing the balsa - easiest way is to coat the coupler in wood glue. That will block the ejection gases. So I will soon start sealing the balsa couplers on my rocket payload sections, starting with the RX-16.

NARCONs are good - even old dogs like me learn a thing or two.

What to do when OpenRocket no longer works...

Some of you may know that I switched from Windows/PCs to MacOS/Macs several years ago - I got tired of all the issues with drivers, the "blue screens of death", the endless stream of updates, and the relentless virus/malware attacks. However, this change came with costs - the first being that Macs are very expensive compared to the equivalent PC in terms of horsepower. There is also less software available, especially in the engineering area, and you pretty much sell your soul to Apple. Microsoft only wants to own your computer's operating system - Apple takes the whole shooting match, hardware and OS. But I will say that things work very well the vast majority of the time - practically no system crashes, and the software that is available works smoothly and has a "better polish" than the Windows equivalent. I have had no problems with software from the Apple App Store; it's only the stuff one downloads that causes the fits.

Which brings me to OpenRocket...

On all my past Macs (including my MacBook Air laptop), OpenRocket has worked flawlessly; it even worked fine on my new Mac until yesterday, when I upgraded the operating system from Catalina (10.15) to Big Sur (11.1). I did the usual reinstall of Java you have to do when you perform such an upgrade, checked to make sure the Java was working, and then fired up OpenRocket as a test. That's when I saw this:

Well, crap.

I spent the next couple hours googling and trying things with permissions and stuff - nothing worked. My frustration mounted, and I began to understand the feelings of TARC newbies who struggle to get OpenRocket working on their computers. I had often shrugged off their issues by telling them their Java installs were not right, and that if Java was working, there would be no problems with OpenRocket. Well, darn it, my Java was working and the stupid program would not run! I can tell you, I will be much more sympathetic in the future.

For a few minutes, I thought OpenRocket's performances on the screen of my shiny new Mac were a thing of the past, and that I would have to run it on my laptop (which I am not going to upgrade to Big Sur anytime soon!). Then my searching revealed this page, in which someone had posted links to OpenRocket run times and executables compiled for different operating systems. I downloaded the MacOS version, and voila! OpenRocket once again graced the screen of my Mac!

Big sigh of relief.

However, this whole experience once again drove home the fact that major updates to our computer operating systems, driven by security and technology advances, are just as, if not more, frequent than software updates. This is especially true for hobby programs like OpenRocket, which hasn't been updated since 2015, and also for altimeter drivers/codes like those from PerfectFlite. Keeping these legacy codes running often involves hacks or bypassing OS security features, and eventually things reach a point where even that is not enough. Catalina did that to me, as 32 bit codes no longer work. Unlike Microsoft, which provided a fair amount of backwards compatibility, Apple simply forced developers to upgrade their programs to 64 bits. So now I have to find a Windows box to download data from my Perfectflite PNUT. This is the major reason I have largely switched to Bluetooth altimeters like the FlightSketch, as small vendors like PerfectFlite focus on the Windows platform, which is over 90% of the market. Macs are an afterthought, if there is a thought.

I understand that we can expect a new version of OpenRocket sometime in the foreseeable future, which would make me quite happy. It's a great program and needs to be maintained/upgraded.

Back to designing rockets...