I went supersonic!

[cjl]

Well, as many of you know (and I'm sure many others guessed based on my avatar), I am fairly heavily into high power rocketry, and have been flying rather large rockets for some time.

However, until today, they have all been subsonic. Today, I finally got a rocket supersonic without breaking or losing it :D

The rocket was a 1.6 inch diameter, 44 inch long rocket that weighed 479 grams. The motor was an Aerotech I600R, which is also 1.6 inches in diameter, is 13 inches long, and weighs 617 grams loaded (323.7g of propellant). It has a total impulse of around 640 Ns. Here are a few graphs taken from the altimeter that was onboard to record the flight (they're large images, but small files - only about 40kb each):

First, the acceleration graph

The sudden drop in deceleration around 3.6 seconds is because it is dropping subsonic, creating a dramatic reduction in drag. Also, the huge spike at about 22 seconds is the shock of the deployment of the parachute:
http://i27.photobucket.com/albums/c183/chris_lapanse/Accelerationgraph.png

Next, a graph of velocity:
http://i27.photobucket.com/albums/c183/chris_lapanse/Velocitygraph.png

The next two are both altitude graphs, but were obtained slightly differently. The first is an integrated altitude graph, which was obtained by taking the second integral of the measured acceleration values - it is more accurate throughout the mach region, but may be slightly less accurate for peak altitude, as it cannot account for a slightly nonvertical flight:

http://i27.photobucket.com/albums/c183/chris_lapanse/Integratedaltgraph.png

Finally, the barometric altitude graph. This one isn't perfectly calibrated yet (the altimeter is an experimental one), but should be fairly close. In addition, I think it's pretty neat to see the effects that the mach transitions had on the reading - look at the inconsistencies around 0.4 seconds (when it first entered mach) and then later at about 3.6 seconds, when it was slowing from supersonic to subsonic again. Kind of neat to see:

http://i27.photobucket.com/albums/c183/chris_lapanse/Baroaltgraph.png

Now, if anyone is still reading, the pretty pictures (these ones are clickable thumbnails because the filesize is MUCH larger):

Here is the rocket right at ignition:
http://s27.photobucket.com/albums/c183/chris_lapanse/th_RG1S3362crop.jpg (http://i27.photobucket.com/albums/c183/chris_lapanse/RG1S3362crop.jpg)

And here it is screaming off on its way to mach 1.6 and over 3000 meters:
(it's already doing about 60m/s in this picture)

http://s27.photobucket.com/albums/c183/chris_lapanse/th_RG1S3363crop.jpg (http://i27.photobucket.com/albums/c183/chris_lapanse/RG1S3363crop.jpg)

If and when I get better calibration data for the barometric sensor, I'll post the updated numbers, and I also have a picture of me with the rocket somewhere around here. I'll get those up sometime tomorrow. I'm absolutely thrilled though - I've been wanting to do this for several years now, and have destroyed a couple rockets and lost a couple more trying to achieve it :)

[mugaliens]

Congratulations and welcome to the club!

Never done it in a rocket, just with my backside strapped to an ACES II...

[snarkophilus]

That is fantastic! Congratulations!

What's with the inflection point at the low end of the integrated altitude graph? The velocity looks pretty linear in that region. Are the velocity and acceleration graphs perhaps from different instrumentation?

[Tobin Dax]

That is fantastic! Congratulations!

What's with the inflection point at the low end of the integrated altitude graph? The velocity looks pretty linear in that region. Are the velocity and acceleration graphs perhaps from different instrumentation?
As a quick response at 4am, the inflection point seems to correspond with the discontinuity in the acceleration at about 2 sec., when it goes from decreasing to increasing. At a second look, this is also where the velocity function is discontinuous, so the inflection point is supposed to be there. I think it's where the engine cut out (but the 4am disclaimer applies to this statement-I'm tired and possibly wrong).

As a side note, it would be nice if the time axes were aligned in these images. I didn't want to work that hard to compare the plots. :)

Edit: That's great, cjl. Congratulations.

[Maksutov]

Fantastic, cjl!

:clap: :clap: :clap:

Man, I wish back when I was launching model rockets with Enerjet and FSI motors we had such instrumentation available.

But the experience remains the same and obviously just as fulfilling, if not more.

Congratulations!

Look out, Mach 2!

[The_Radiation_Specialist]

that's awesome...

congrats :)

[cjl]

Thanks :)

Here's a better graph, with all on a single one. This should help show how they line up more accurately. It also takes into account some calibration differences with the altimeter that help the graphs agree with each other much better:

http://i27.photobucket.com/albums/c183/chris_lapanse/overall-metric.png

As for the inflection point, it should be there, as the curve of the altitude graph should face upwards during acceleration (and motor burn), which takes roughly 1.2 seconds, and then should face downwards during deceleration after burnout.



EDIT: the altitude readings are in meters

[Tobin Dax]

As for the inflection point, it should be there, as the curve of the altitude graph should face upwards during acceleration (and motor burn), which takes roughly 1.2 seconds, and then should face downwards during deceleration after burnout.
[Yay, I was right! I was too tired to be more than 90% sure. :)]

Thanks for the multiple plot, though your altitude doesn't have units given anywhere. :whistle:
However, I'm having a much harder time accurately finding the inflection point in the altimeter data now. :shifty: :D

[snarkophilus]

As a quick response at 4am, the inflection point seems to correspond with the discontinuity in the acceleration at about 2 sec., when it goes from decreasing to increasing.
Ah, I see... I did not notice that the axes were not aligned. Makes sense. And thanks for the pretty new graph, cjl.

[davidlpf]

good work cjl.

[cjl]

[Yay, I was right! I was too tired to be more than 90% sure. :)]

Thanks for the multiple plot, though your altitude doesn't have units given anywhere. :whistle:
However, I'm having a much harder time accurately finding the inflection point in the altimeter data now. :shifty: :D

Ahh crud - that's what I get for posting in a hurry...

It's in meters btw...

[Tobin Dax]

Ahh crud - that's what I get for posting in a hurry...

It's in meters btw...
I figured that based on everything else. I was hoping that the smiley gave away that I was messing around a bit. I really do appreciate that plot, I just don't want to pack for my move. :)

[farmerjumperdon]

Way cool. I never went beyond the Estes kits back in my days. But they were fun to assemble and build (back when there was no plastic and nothing was pre-built).

[cjl]

I definitely think that the pre-built stuff isn't very good - but some of the actual kits still made by estes (and some other companies like fliskits) are quite fun to build and fly too - not to mention easier to find after landing :)

[m1omg]

congrats, good work :)!

[Argos]

Well you seem to be doing better than the Brazilian Space program. :)

Congrats.

[Damien Evans]

For your next goal, you must emulate Australias crowning achievement in rocketry: one sattelite in LEO!

Oh, you want to take smaller steps, oh, right, carry on then...

Anyhoo, congratulations!

[antoniseb]

Congrats. I used to do HPR, but never went supersonic. I had plans to, but dropped the sport before that rocket was built.

[Mister Earl]

I love rocketry. I had a shoddy little prebuilt plastic junker back when I was a kid. None since then... budget doesn't allow it. Maybe I'll try to fabricate my own, and use an exotic fuel Mythbusters style. I wonder how well beeswax would work. Or roofing tar.

[Trebuchet]

You're not going to try the salami?

[Mister Earl]

Nah. If the Mythbusters couldn't get it to go after two tries, then I probably wouldn't get it to work after twenty. I'd like to figure out a way of cheaply making nice little hybrid rockets. Altitude doesn't have to be spectacular. Something small, the size of a 1-liter bottle, or something. Made from cheap materials, so when I inevitably break it, it can be repaired/replaced without undo financial drain. That's the kind of setup I'm looking for.

[Mister Earl]

OOOH.... or maybe something really exotic. Like a tiny, working model of the treibflugel. Now THAT would be an eyecatcher!
http://en.wikipedia.org/wiki/Focke-Wulf_Fw_Triebflugel

[mugaliens]

I definitely think that the pre-built stuff isn't very good - but some of the actual kits still made by estes (and some other companies like fliskits) are quite fun to build and fly too - not to mention easier to find after landing :)

In high school, I found a very lightweight plastic tube of the same internal diameter as the D engine's external diameter, glued three double-edged razor blades as fins at a rakish angle, replaced the chute with a very small streamer (just enough to counter the rocket's nose-first plunge to Earth), shaped the nosecone in a long slender V, coated the nosecone with monokote, then let her fly.

I figured the razor blades would have a lot less drag than thick balsa wood fins (true, especially since they penetrated the body and were glued on the inside), the plastic body would have less air friction than the cardboard tube (also true) and better strength (true), etc.

In five seconds it reach an altitude of just over a mile, as measured by triangulation (observer stationed 1 mile away). The average velocity was 722 mph, which means that it's possible it broke the sound barrier at some point during it's ascent, for the sound barrier that day was about 758 mph at liftoff elevation. More than likely, though, it came close, but no cigar.

The breeze was mild (less than 5 mph), but it still landed about 700 feet distance despite a near vertical ascent and a descent rate of about 15 fps.

[Josh]

clj, Do you have a video of the launch by any chance?

[cjl]

None yet - I'll ask around at the next club launch.

Just got final calibration data from Adrian (the designer of the altimeter used), and the final calibrated altitude measurement is 3642 meters (11950 feet), with an accuracy of about +- 5 meters.

[mugaliens]

Woah - that's some pretty precise accuracy!

[cjl]

Yep - he has a fairly high resolution sensor, and that combined with extensive calibration and weather reports from the day of the flight can allow for quite accurate measurements :)

The sensor actually is about 2 meters per count, but there are a few other uncertainties that push that out to plus or minus 5 meters. Certainly a lot better than the eyeball altimeter that I've been using for so many of my rockets for a long time :D