Model Rocketry Thread

[danielrowell]

Hey guys! With so many of the members interested in physics and things that go BOOM!, I thought I'd start a thread on model rocketry.

Due to the sensitivity of this topic, I talked it over with the moderators, and this is what PCGUY said:

I don't mind people posting about using premade rockets, as long as they are in NO WAY used or linked with spud cannons in ANY way. As far as modifying premade rocket engines, or making your own, sorry that falls too much into the pyrotechnics category which opens up a whole new set of laws, laws which have no place being mixed with spud cannons.

That said, I'll jump-start this thread with a high-altitude "F" impulse rocket I designed using Apogee's amazing Rocksim software. It's a minimum-diameter style rocket with a projected altitude of 7,958 feet. The fins have been optimized to achieve the highest altitude possible, and I was planning on loading the ejection bay with red powdered paint so that I could measure its ejection altitude. This rocket is also capable of safely breaking the sound barrier if a higher-thrust motor and different fins are added.



My 30 day trial of Rocksim ran out before I could lengthen the body tube to increase the marginal stability.

Thoughts, questions, comments, or new ideas are welcome.

[D_Hall]

LOL...

Just as a point of interest, I wrote the original 6 DOF routines for Rocksim Pro.

[danielrowell]

Very cool! Out of curiosity, what's a DOF routine?

Rocksim is great software, by the way. It's especially neat that a fellow spudder was involved in the creation of it.

Sorry to steal your pic from hypervelocity advanced cannon, JSR, I just couldn't resist.

[danielrowell]

(After doing some research and finding this webpage)

WOW! Let me get this straight. By writing the Degree Of Freedom (up/down, yaw, roll, etc.) routines, you effectively wrote most of the Rocksim Pro software? Now I know why you started that thread about you loving your job...

Based on your expertise, is there anything I could do to my rocket to make it reach a higher altitude? Actually, do you think my rocket would even be capable of an altitude that great? I just looked at the NAR records, and the highest flight of an "F" power competition rocket is only 5,711 feet.

[D_Hall]

I didn't write the simplified routines used in the basic Rocksim package. Since you've found the Apogee website you'll notice that it states that Rocksim Pro is basically Rocksim combined with the routines from the SPLASH simulation package. I wrote the SPLASH simulation package. I did it primarily to prove that I could and once done I kinda lost interest in customer support. So, Tim at Apogee bought the source code from me and turned it over to the guy who writes Rocksim. Thus, Rocksim Pro was born and SPLASH was discontinued.

All that stated... No, I didn't write most of the Rocksim software. I only wrote the 6 DOF routines used in Rocksim Pro. If you've not used Rocksim Pro (or SPLASH) you haven't used anything I wrote.

As for altitude records for F class motors and such: Off the top of my head I have no idea. I've never really dealt with motors that small. However, an awful lot of reasonably intelligent folks have gone after that and similar records. If that's the NAR record, I'd imagine it's pretty damned tough to beat it under their rules (the NAR/TRA rules are pretty damned restricitve).


Oh, and that software had nothing to do with my job.

[danielrowell]

To D_Hall:

Sorry to seem so over-the-top enthusiastic and assumptive in my last post. I didn't have much to go on and, obviously, I really enjoy model rocketry.

As to the SPLASH software, I fully understand that it isn't part of the basic Rocksim that I used, but Rocksim Pro. Even though SPLASH has been discontinued, I still think that being able to write something of that magnitude is quite an accomplishment.

As to the altitude records, I am a bit puzzled. The last record involving "F" power motors was set in 1981, long before the current motors in that power were available, I'm sure. The record list was last updated very recently, by the way. What I find strange is that Apogee's Aspire kit is supposed to be able to fly slightly higher than the current record, though completely pre-made kits can't be used in competition, of course. Still though, you'd think somebody would be able to break that record in thirty years... My guess is that most of the competitors ignored the lower power f motors and went with the "G" motors, since the record for the G power-class was set much more recently.

As to the rules, I've read them all and unless the NAR safety crew disproves of my rocket for some reason, it passes the test.

And to finish up my post with a bang, here's an absolutely awesome video of an amateur high-power rocket hitting an altitude of 121,000 feet in an attempt to claim the Carmack Prize. Enjoy.
[youtube][/youtube]

[jrrdw]

That was awsome!

[Gun Freak]

Wow that was incredible, thanks for posting.

[mattyzip77]

dam, that was serious!!! unreal!!

[pneumaticcannons]

wow that video is crazy! thanks for sharing i have a crayon rocket laying around in the states. Luckily I have one bit of footage somewhere on my channel

[D_Hall]

Sorry to seem so over-the-top enthusiastic and assumptive in my last post. I didn't have much to go on and, obviously, I really enjoy model rocketry.

As to the SPLASH software, I fully understand that it isn't part of the basic Rocksim that I used, but Rocksim Pro.

Oh, no worries. I just thought there was a misunderstanding.

But if you're that into rocketry, you'll really cream your jeans when I tell you what my job actually is... I run China Lake's Skytop facility. Well, I do a few other things as well, but Skytop is my primary responsibility.

As to the altitude records, I am a bit puzzled. The last record involving "F" power motors was set in 1981, long before the current motors in that power were available, I'm sure.

You say that like F impulse motors of today are any better than F impulse motors of 30 years ago. They aren't. F impulse is F impulse. By definition. Even if the manufacturers were to come up with a much more powerful propellant, they would use a lot less of it to make an F impulse motor.

Further, it turns out that in the HPR world many (most?) propellant formulations are not driven by "power" but instead cost and theatrical considerations. By "theatrical" what I mean is "looks friggin' cool." The most blatant example of the "theatrical" propellants are the so-called "Smoky Sam" line of motors by (IIRC) Aerotech. That propellant is TERRIBLE when it comes to performance. It was designed to do two things. (1) Make a lot of fire, and (2) make a lot of smoke. Still, it looks cool so they sell a lot of it.

Still though, you'd think somebody would be able to break that record in thirty years...

First, there's a very big difference between a vendor claiming an altitude and an altitude record that's confirmed using more rigorous standards. Still, you bring up a very good point with the "30 year" comment, but I'll offer up a different explanation. Mind you, my explanation is a guess as well, but here's where I'll put my money: The reason it hasn't been broken is that the motors of 30 years ago are no longer available. It's entirely possible that 30 years ago there were motors sold that were designed with a more optimal thrust/time curve than those of today. But those motors were harder to manufacture so the powers that be stopped making them in favor for the cheaper motors with less optimal thrust/time curves.

And to finish up my post with a bang, here's an absolutely awesome video of an amateur high-power rocket hitting an altitude of 121,000 feet in an attempt to claim the Carmack Prize. Enjoy.

Yup, great video. It's a damned shame they were unable to get any usable GPS data (lost lock almost immediately). Still, they learned a lot.