It's 3 weeks from launch date, construction and ground testing for the Defiance-H is done. Now that the rocket is ready, I can do the final calculations on center of gravity and descent rate. I assembled the fuel grain in the combustion chamber, did an over all weighing of the rocket, then balanced the rocket on a roller to determine the center of gravity.
Here are the specs and predicted specs:
Over All Length: 192.25"
Nose to CG: 120.125"
Nose to Barrowman CP: 153.43"
Stability Margin: 33.305"
Weight no N2O w/Fuel: 73.4 lb.
Fuel Grain Weight: 9.6 lb.
Fuel Use: 6.17 lb.
Burn Out Weight: 67.23 lb.
N2O Load: 35 lb.
Lift Off Weight: 108.4 lb.
Descent Rate Under 4' Drogue: 79.07 fps
Descent Rate Under 4' Drogue & 10' Main: 29.36 fps
Initial Thrust: ~875 lbf
Thrust to Weight Ratio: 8.07:1
Time to Apogee: 39.6 sec.
Apogee: 25,000'
Time Under Drogue: 303.5 sec. (5.06 min.)
Time Under Main: 34.06 sec.
Total Descent Time: 5 min. 37.5 sec.
Altimeter Setup:
RMCS
Pyro 1 Apogee no delay
Pyro 2 Apogee 1 second delay
Pyro 3 at 1,000'
LED enabled, sample rate 50 Hz.
RRC2X
Mach Delay 25 seconds
Main at 1,000'
Apogee Charge: 10 grams 3F black powder
PIRM2 Main Charge: .6 grams 3F black powder (1" straw measure)
Altimeter power supply: 3) Energizer Max 9 volt batteries. 2 in parallel for main power, 1 for RMCS pyro power. All tested 9.4 volts or higher, 6.4 amps or higher. Batteries zip tied and hot glued at base.
Launch Valve PIRM2 Charge: .35 grams Red Dot (1" straw measure)
Line Cutter Charge: .35 grams Red Dot
Pre heater Grain: 22 grams APCP
I'm one week out from launch day, I had to restrain myself from performing final prep work on the rocket until now. As you can see from the data above, the altimeters are loaded and ready to fly. I also drilled the N2O vent hole in the tank today, I decided to go with a .032" vent hole to keep chilling and loss in the tank to a minimum. I also picked up a second N2O tank this week, and purchased more plumbing to allow me to connect the two tanks in parallel. The dual tanks should help to keep the N2O temperature/pressure up. In the past I've had a single N2O supply tank ice up while filling a run tank. The dual tanks should reduce the amount of N2O drawn from a single tank, which means less liquid turning to vapor and less chilling.
The waiver has arrived as well. The bad news is that my FAA contact told me I probably wouldn't be able to fly from this location again. Apparently there is a jet path over this site at 18,000'. I'm not sure how far I'll have to move, if it's just a few miles, that shouldn't be a big deal, but if it's more than that, I may be looking at Alton again. Alton isn't ideal either since it falls in the take off/landing path of the Sioux City airport. Finding a suitable launch site is really a PITA, unless you know someone, it's hard to just drive up to a persons home and get them to let you launch rockets...
I decided to test a slightly larger pre heater grain for this engine. I've been using about 10 to 15 grams of APCP, but with a larger engine I may need a bit more to ensure good ignition. I used a pre cast grain for a small 29 mm motor, cut the inhibitor layer off and drilled a 3/16" hole down the middle. The hole down the center is for the wood dowel that holds the grain in place in the combustion chamber.
Click Here for a short video of the burn.
Here's a vid cap several seconds into the burn.
The burn looked pretty good, a nice symmetrical ball of flame and sparks. It looks like I'll have about 17 seconds from ignition until the propellant starts falling off the dowel. I did only use one igniter on this test, where I use two (one on each side of the grain) on a flight. That brings up a good point, I have quite a number of pyro events that all must happen for a launch to be successful, so I double up on igniters on the pre heater grain, and double e-matches on both the line cutter and the main valve PIRM2. That makes for 11 e-matches/igniters for the 5 pyro events of the launch and flight. (2) Line cutter, (2) pre heater, (2) main valve, (3) apogee and (2) main.
Sometimes I wonder if I think too much about what could go wrong... Probably not though! In this case I worried about the nose cone bulkhead tearing off the nose cone itself. For some insurance I ran some 9/16" tubular nylon under the "U" bolt on the inside of the nose cone bulkhead, then ran it through the telemetry bulkhead. To make sure the telemetry module stayed together, I ran some steel cable through the bulkhead and around the mounting board in two places. Now if the nose cone snaps at the end of the shock cord with too much force and breaks the bulkhead mount, the fiberglass nose cone will fly off but the telemetry package will stay attached to the shock cord.
Here's the other side of the telemetry board.
It may be overkill, but you can see I have 3 tie wraps on each set of batteries. I also used hot glue to help retain the battery packs. While hot glue isn't super strong. What it is, is flexible. It grips the mounting board with amazing strength yet should provide some shock protection for the battery packs. It's hard to see in the picture, but the GPS output connector simply slides into a slot on the top/back of the GPS. I routed out a slot in the board for the connector to reset into, that should go a long way to retaining it. I also used hot glue to glue the connector to the GPS for added strength. The GPS really can't go anywhere, since it's wedged in between the lower bulkhead and the batteries, and when inserted into the 3" tube it presses against the tube wall as well.
I did one last test with the telemetry unit all wired up and ready to fly. As expected it all worked fine, batteries are all fresh and should give me some 10 to 12 hours of transmit time.
Launch Day:
I had set up the launch trailer for the Defiance-H the day before, so Saturday morning was spent setting up the launch control equipment and the launch control tent. The waiver opened at noon, with pretty much everything set up shortly after 11:00, John and I did a little more prep on the Defiance-H, then we would have to wait until 2:00 for the high altitude portion of the waiver to open.
John poses with the assembled rocket shortly before it was raised to the launch position. Most of these better quality pictures are courtesy of Steve M.
Steve, John and I raise the tower after final prep work on the rocket.
John and I level and "lock down" the tower to the proper angle.
Here you can see the fill line where it enters the rocket on the left, and the engine N2O valve on the right. The orange part is the "ejectable valve arm".
Here you can see the rocket with all pyro events hooked up to the wireless launch control system.
I arm the recovery system.
Steve snapped this shot just before we left the area to start the launch sequence.
The moment is finally here! The wireless launch control system worked great, we went through the process of starting the fill. Once John reported a white plume of N2O vapor from the vent hole I closed the fill valve, fired the line cutting device, then ignited the pre-heater grain. Once we detected good smoke, I gave Ben the go ahead for the count down. 5,4,3,2,1 and ignition!
Here is the moment of ignition. The engine lit so quickly you can see the flash from the PIRM2 in the same video frame as the first flame from the nozzle.
As the rocket starts up the rail, you can see the N2O valve arm being ejected. Photo courtesy Jay Griebel.
A couple of video frames later the valve arm clears the rail and drops about 5' from the pad. To this point everything was working perfectly.
This is another picture from Jay. The rocket is just out of frame, but you can see the flame and a few mach diamonds. About mid tower level you can see the white plastic washer used between the rocket body and the ejectable valve extension, which you can see really isn't even on it's downward path yet and the rocket is well off the rail.
Here's a shot from Paul's video as the Defiance leaves the rail. We had a lot of new spectators at this launch, I have to admit the reaction was somewhat comical to me. They started out pretty quite right after the launch, then the chatter level really went up. I think surprised and a little shocked at the launch would best describe their reaction.
I was expecting some weather cocking from the strong breeze, but the Defiance-H left the rail and flew almost as straight as an arrow.
Here's about the last frame where you can still see the rocket. The polyester resin/HDPE fuel grain burns pretty clean so there wasn't much of a smoke trail to follow. The very bright flame did make tracking easy for the spectators though, as many people were able to watch the ascent for a good 13 seconds until the engine burned out.
I'm tracking the rocket with the beacon receiver.
Here's the blast hole the engine created.
Click Here for the final edited version of the launch. 10.7 MB in Xvid codec. If you don't have xvid you really need to install it, it's a very high quality video for a given file size. Here's the Xvid codec for Windows.
Click Here for a short edited video of the launch. 3.23 MB .wmv
Click Here for a higher quality video of the lift off and boost from Paul's camera. 22.8 MB .mpg
Click Here for a static camera shot of the launch from Paul's analog camera, also a longer clip of the LCO tent and people watching the launch.
I'll be getting more video and pictures from other sources, I'll try to post them as I get them.
After the rocket was out of sight, I went to my car where I had the GPS Telemetry receiver set up. The GPS had
lost 3D lock as soon as the rocket launched, but I was still getting a good ground track on its position. Then
at apogee I lost the signal. I picked up the homing beacon and tracked the beacon transmitter from the ground.
After a couple of minutes I was confident the rocket was under drogue chute, and gave John the beacon receiver
to continue tracking while I took another look at the GPS telemetry. I never did get another lock on the telemetry.
John tracked the beacon for a good 4 or 5 minutes until the signal was lost over the horizon.
John and I went out for a quick search in my car while the others brought the hybrid GSE to the closer pad for a later hybrid flight. The quick search didn't locate the rocket, so we returned to the launch site to continue with other launches. When the waiver closed at 4:00, Steve volunteered to do his thing and go out and try to find the Defiance-H. Once we had things taken care of at the launch site, Joel and Michele went out in one car, and John and I back out in my car for more searching. Just as John and I were leaving the launch site, I got a call on my cell phone that Steve had found the rocket! You have to hand it to Steve, he's got a nose for finding rockets...
We all converged on the location Steve gave us. About 1/2 mile before we got to where Steve was parked, we sighted the main parachute blown against a fence in the middle of a field. It was a long way into the field, but that big orange chute was sure easy to see!
This is the way we found the Defiance-H. After a minute to assess the situation, I noticed the nose cone wasn't with the rocket. Honestly, that wasn't a huge surprise to me, more on that later. What did surprise me was the drag trail the rocket had left in the ground. It was pretty windy at that point, but I really didn't think it would drag the rocket like it did. I laid my ear next to an ambient pressure port to read out the altitude beeps... 23,474' Ground level is about 1,350', so that makes the altitude 24,824' MSL, or 176' below my waiver. That's cutting it pretty close!
Joel, John and Michele pose for a picture while Steve follows the drag trail to the actual landing location of the rocket. It turns out the wind drug the rocket nearly 1/3 of mile before being stopped by the fence. I rather assumed the main chute would be torn up in the fence, but oddly enough it's in great condition.
You can see the trail the rocket left in the ground as it was being dragged by the main chute. For some reason it left that S shaped curve back and forth the entire way.
We knocked out as much dirt as we could to lighten the load, and Joel and I carried the rocket back to the road. After we broke the rocket down, we started discussing the missing nose cone. Now, I had sort of expected this. The extra weight of the telemetry system in the nose was going to mean more stress at deployment. That's why I added that tubular nylon lanyard to retain the electronics module if the nose broke free. I also used a little hotter black powder I think. This was a fresh can of 3F, where in the past I'd been testing with an older can of 2F. I knew there was a chance of this happening before the flight, but I opted for a "sure recovery" over the possibility of losing the nose cone. I had considered using a separate chute on the nose cone, and I think I might just go that way on future flights.
After we talked about it a while, John had sort of a revelation. He brought up the point that if we'd lost the nose cone at apogee, why did we track it with the beacon transmitter for over 4 minutes. He was right, there should be no way it would take that long for the nose cone to free fall from apogee. So I broke out the beacon receiver, and sure enough I picked up the signal! So we did a bit of a grid search and found the nose cone about 1 mile up wind of the rocket landing site. Another "oddly enough", the nose cone was in near perfect condition, and had landed point down.
The only explanation I can come up with is that the nose cone stayed with the rocket until the main chute deployed, the extra little shock of the main deploying broke it loose and dropped it from around 1,000' AGL. Regardless of what happened we recovered everything in pretty good condition. The fin can took a bad beating from being drug so far. The two fins that were dragging in the dirt are worn down and both are bent. It looks to me like thermal soaking softened up the epoxy in the fin can, that was also something I had assumed would happen.
When we returned home I attempted to download the data from the recording altimeter, for some reason the software is reporting the number of data samples and the peak altitude, but won't download the data. I'm not sure what's up with that. This altimeter was on board the Aestus, and went through a tough recovery there. It is also a beta unit, so it might just be a glitch in the code. I'll send the altimeter back to the builders and see if they can pull out the data. We should have our own flight computer/telemetry system working in time for my next flight.
Once back at my home, the crew (John, Joel, Michele, Steve and I) broiled up some good Iowa steaks and took a much deserved break and had a good meal.
In summary, I was elated with the flight results. All the systems I was testing for my next project worked great. I also had my suspicions about a couple of other things confirmed. I'll move to aluminum fins to prevent the thermal soaking from the nozzle damaging the fin can, and I'll move to separation at apogee style recovery. Down range distance from the launch site to landing site was almost exactly 3 miles.
Here are a few more details on the engine:
N2O tank 1: Starting weight 196 pounds, ending weight 175 pounds
N2O tank 1: 21 pounds used
N2O tank 2: Starting weight 183 pounds, ending weight 164 pounds
N2O tank 2: 19 pounds used
Total N2O used: 40 pounds
The N2O usage looks about right, we used just one tank on a small N2O flight attempt later, that would account for the 2 pounds difference between the tanks. That puts me at about 38 pounds used for the Defiance-H, assuming the flight tank held about 33 pounds at the pressure/temperature we had at launch, that leaves me with about 5 pounds used for venting during the fill process.
Here's the combustion chamber after I removed the injector bulkhead and the nozzle. Notice the beat up fin can in the back.
This is looking at the injector end of the casing.
The fuel grain has been removed. There was no burn through any where on the EPDM thermal liner. This is looking at the nozzle end where the cardboard tube/EPDM liner went into a step in the nozzle. Even the cardboard tube held up fine.
This is a closer look at the nozzle end of the fuel grain.
An interesting discovery was I only consumed 2.6 pounds of fuel on this burn, about half what I expected. That would seem to be the primary reason for the short flame noticed at launch, the mixture was very fuel lean and combustion was very complete. My theory for the low fuel consumption is that the injector ring remained the same as in my previous burns, but the port diameter was increased. That meant the N2O was injected farther away from the fuel grain surface, giving me a slower regression rate. I'm still trying to decide if that's good or bad. It's good in the fact that I can do a longer burn, using more N2O in a given casing diameter. It's bad in that the Isp will drop about 12.5 seconds running at a 92/8 oxidizer to fuel ratio. The fuel grain started out at 9.6 pounds and ended at 7.0 pounds.
Here's a detail shot of the fin can. You can clearly see the heat damage caused by the heat soaking from the nozzle. The worn leading edges are from the rocket dragging in the ground.
Here's the aluminum part of the nozzle retainer, it's been cleaned up but you can still see epoxy residue stuck to the edge where the fin can touched. You can also see the inside of the injector plate. When I removed the injector plate I was surprised to find two of the six stainless steel cap head bolts had heat damage at the very end of the heads. That's another sign of the circulation I've seen on all these large hybrid burns. The bolts weren't in risk of failing, it was just interesting to see the very end of them melted.
This is a picture of the recovery system, all in ready to use again condition.
And the Defiance once again back on the wall.
It's been three days since the launch, I ordered materials today to start a 16,000 lbf total impulse "P" class hybrid...
Update June 20, 2008:
Mike B. was kind enough to send the flight data from the RMCS flight computer after they corrected the code problem.
Here's a screen cap from the computer application.
Here's a zoom on the data from ignition to apogee.
Click Here for the RMCS native file.
Looking at the data in general, you see a lot of noise in the accelerometer data. While hybrids are notorious for that, this data is both noisy and odd. Notice even before apogee the velocity goes deeply negative, then at the end of the flight the altitude goes -136 feet. Obviously the accelerometer had a hard time with this flight, it's possible the sensor sustained some damage in the Aestus flight as well. Other than seeing when events took place, I think we have to pretty much throw out the accelerometer data. Looking at the barometric data, the peak velocity was around 1,574 fps or mach 1.42, pretty close to what was expected.
Descent rate under the drogue at about 1,500' was 82 fps. Landing speed under the main at about 500' was 32 fps. Both of those numbers are very close to predicted at about 3 fps faster. The reported altitude is about 1,000' lower than the Missile Works altimeter, but they are still within about 4%. I should note too, the RCMS raw data reported a higher apogee than the software did... Despite some odd data, it would seem the unit fired all events when it should have. The green lines on the screen captures indicate pyro events, you can see each event occurred on the first green bar from the accelerometer data. That means all the primary e-matches and charges worked and the backups weren't needed.
If you look at the barometric data (blue line) you can see a little bump at about 7,000', then another at about 12,000'. That's very typical of what I've seen on all my flights that break mach. That put the rocket above mach for about 5 seconds.
Here's a screen cap of what GPS data there was.
There wasn't much GPS data, click here for the GPS file in .gpx format.