The Aestus rocket really came about for a simple purpose, to fly the HR5 hybrid engine in a rocket for my first ever hybrid flight. I wanted something quick, easy and cheap, that would break 10,000' but stay subsonic. While the Aestus was cheap to build, it wasn't as quick or easy as I initially thought, or hoped. A secondary mission for the Aestus came about later. A few of us are working on a telemetry system, and I thought the Aestus might be a good place to test a GPS in flight.
I had a few people inform me that my engine design was fine on the ground, but wouldn't fly. Of course I felt I had covered all my bases, but I still had to fly the engine to prove the design. I had some second thoughts on my flight avionics late in game, I was beta testing a new flight computer, since the documentation wasn't yet complete, and I wasn't completely sure of all the functions. I decided on Thursday before the launch to add a timer for backup apogee and run the beta unit as a record only unit. So I used a Missile Works RRC2X for apogee and main, with a timer as a backup for apogee.
Saturday, November 3rd 2007:
The forecast had been calling for great weather on launch day all week. Even the day before, the forecast for Saturday looked great, upper 50's, plenty of clear skies and light wind. Saturday morning looked good, but conditions deteriorated as the day progressed. By launch time, the skies were covered in high, thin clouds, the temperature was in the mid 40's and the wind was sustained 15 to 20 mph and gusting higher. I had the pleasure of meeting, and having the help of two of our forum members, Paul arrived the night prior to launch, and Ben arrived on launch morning. John and Joel arrived Saturday morning to complete the launch team. Steve M., our newest team member lives next to the launch area, and coordinated the land used for the launch site. Steve also played a huge role later...
Many thanks to Paul for sharing his still pictures below:
Ben and I set up the trailer as Joel unwinds pyro circuit wires.
John works on setting up the LCO trailer with the blast shield.
I set up the remote control fill valve as Ben watches.
This is my idea of a joke, not too many people got it. I guess I wouldn't make it in the comedy business.
The Aestus is prepped and about ready to be pointed skyward.
With the rocket upright and leveled, we start packing up the tools for launch.
A last test of continuity on the pyro circuits. You can see a few spectators arriving.
Time to turn on the camera and arm the electronics.
Everything ready, we clear the area and start filling the oxidizer tank. No Ethan, that's not the grim reaper standing next to the launch rail! That's our N2O bottle wrapped up in a sleeping bag with jugs of warm water to keep the N2O pressure up.It took about 4 minutes to fill the flight tank, the fill valve was closed, the line cutter cut the fill line. Then I lit the pre-heater grain, at smoke I started a 5 second count down. 5,4,3,2,1 and...
Ignition of the HR5 engine!
The Aestus moves up the rail.
Nice boost off the rail.
Now we see some weathercocking.
Once the speed picked up, the rocket straightened out some and flew a straight, albeit angled trajectory.
Here's a moment after ignition from the onboard camera.
Shortly after lift off.
Here's shot from just under the thin clouds.
Here's about the last frame before the rocket landed.
Click Here for a video from the onboard camera.
Click Here for a video of the launch from several camera angles and a few stills.
Click Here for a video Steve made, it has another camera angle, nice sound track and some stills.
Click Here for the same video Steve posted to YouTube.
Paul and Ben were set up as a "rapid recovery team" with the RDF receiver as I watched post launch GPS data on my computer. Paul and Ben tracked the beacon signal for about 1.5 miles to the south, then reported a lost signal. My GPS data was discouraging, it appeared I lost the GPS transmitter at apogee. Concerned about a possible apogee non-event, I called Paul and Ben back to the launch site. After I heard they had a signal for over 2 minutes, I was a little less concerned. At least the rocket had deployed something at apogee...
Paul and Ben went back out to search, and I looked at the GPS data I had. The horizontal velocity of the rocket was reported as some 258 mph when the signal was lost. The GPS never did get an altitude lock after it lifted off. Now I was somewhat concerned about the deployment speed of over 250 mph. That's pretty fast for rocket of that size and construction.
Joel, John, Michelle and I joined the search in my Blazer, I had the computer with the GPS receiver hoping a signal might be reacquired. I had really hoped we'd have a GPS lock on the landing site, and we'd drive right up to it. Alas, that wasn't the case. We searched for several hours without any luck. Paul had to head home, so Ben joined us in the Blazer. I decided to head home and look at upper level wind data, since I had the apogee location from the GPS, perhaps I could plot the landing site. We went back out that evening with the new estimated landing path, but again we found nothing.
The next morning John and I went out again, and walked the fence lines in the middle of a couple of sections. We pretty much decided it was futile on foot, and decided to go home and hire a pilot to continue the search. On the way home we stopped at Steve's house to give him the news. He said he'd continue the search that afternoon on his dirt bike, and start asking neighbors if they'd seen anything.
John and I went home and started calling pilots. Later that afternoon, before we'd even set up a plane, Steve called and said he'd located the rocket, although it was in pretty tough shape. The nose cone and main body were found almost a mile apart. Steve's hard work had really paid off, one of the neighbors had said they had seen something white in a field, and sure enough it was the nose cone. Another neighbor saw the main body of the rocket in a field next to the road, and had picked it up and taken it to a relatives house. If that wasn't enough, Steve also told me he had located the Prelude rocket lost last year! A farmer found it in his field during spring field work, and brought it home and propped it in a corner of his machine shed.
When John and I arrived at Steve's we assessed the damage and tried to figure out what happened. The Aestus had zippered the upper body tube all the way to electronics module in one spot, and about half way down in another spot. The main chute was out, had a number of shroud lines torn out and was a tangled mess. The lower portion of the body tube was broken, with only the engine holding the fin can to the rest of the rocket. The nose cone was in pretty good shape, odd since the drogue wasn't with the nose. My guess is the drogue brought the nose cone down on a few strands of the shock cord, then the tubular nylon gave out in the wind on the ground.
The good news is the damage was mainly limited to the body tube. Both altimeters are fine, the timer is fine, the GPS, MaxStream transmitter and homing beacon in the nose cone are all fine. The engine seems fine too, there was one bent pipe fitting between the engine and the oxidizer tank, but everything else seems perfect.
The cause of the problems resulted from two things. First was the speed of the rocket at apogee, the ground wind led to weathercocking. which caused more of a parabolic flight path than desired. While the rocket may have held up to the drogue deploying at that speed, it couldn't handle the main coming out at apogee. In watching the onboard video, you can clearing see the main come out right at apogee charge going off. The video also shows us that both 10 gram deployment charges went off at the same time. Which likely aided in ejecting the main chute at apogee. Data from the video gave me the average descent rate, the main body came down at about 109 fps (74 mph). The rocket just wasn't built to take that hard of a landing.
So several factors contributed to the less than nominal recovery.
Easy enough to fix. A deployment bag with a Velcro closure would help I'm sure. A single apogee charge, or the second charge delayed. Launch in lower winds and/or increase the thrust to weight ratio.
Here's a shot of the main chute shortly after apogee.
Here is the engine, nozzle, electronics bay, nose cone and the dusty old Prelude home at last.
Here is the body tube. The two sections to the right I cut apart to make removing the electronics bay easier. Notice the long zipper!
Here is the oxidizer tank in great condition.
The main chute had about 1/3 of the edge hem and shroud lines ripped off.
This is the upper fuel grain with the thermal cap. As you can see it handled the extra oxidizer load just fine. This flight used about 10 pounds more N2O than the highest load static test.
The lower asphalt grain was "just" enough, as it had just started to burn through. The casing looks fine though, so I suspect most of the crack you see there wasn't exposed to much heat.
Here's a map from the GPS data showing the launch site, apogee location, and landing sites for the main body and the nose cone. The homing beacon was still transmitting when I picked it up at Steve's house.
Here's a screen capture showing the altimeter data. Apogee was at 15,700' on one unit, and 15,5??' on the other.
Assuming a 27 pound N2O load, a burned fuel weight of 4.8 pounds and a Cd of .55, the calculated Isp was 192.
I've always used the this criteria as a minimum to determine if a flight was successful. "If the payload is
returned intact and flight performs its required function, the flight was a success." So going by that criteria,
the flight was successful. The engine was proved in flight, the GPS tracking system was flight tested, I returned
the electronics payload including flight video. I won't call it a flawless flight, but certainly a success.
I have a feeling I'll repair the Aestus, if nothing else just as a memento of my first hybrid flight. I doubt I'll fly it again though. Since the basics have now been proven in flight, I'll move on to the next project. I'm working out details on a 6" diameter "P" hybrid. I'll probably start engine construction this winter, static tests this summer and a flight next fall.