Part 3, 20 August, 2007
By Mark Uitendaal and Leon Krancher
- Quick and Dirty, part 1, 7 April, 2007
- Quick and Dirty, part 2, 16 April, 2007
- NLD25 launch, 1 June, 2007
Disclaimer: all liability waved! The contents of this page is presented for informational purposes only. Do not try to recreate any experiments presented in this page. The NAVRO and the author of this article cannot assume responsibility for any use readers make of this information. In The Netherlands it is forbidden by law to own this type of propellant if you do not have an exemption of the "Wet Explosieven Civiel Gebruik" (WECG).
The flight of the Quick and Dirty.
After constructing the rocket it was now time to fly the Quick and Dirty. The whole week prior to the launch there was a little bit of excitement. The motors where prepped and ready, the electronic canister was programmed and the parachute was folded. In the last week prior to launch we decided to fly with the PaDS and the R-DAS. This was done because a backup-timer wouldn't fit the job after all. The rocket was shipped to the launch site ASK 't Harde near Oldebroek on Thursday.
The rocket was checked by NAVRO officials for stability and safety on Thursday in the afternoon. After a thorough inspection the rocket was declared fit for flight. After the inspection we went to the preparation area. In this building the rocket is assembled and prepped for flight. Also all pyrotechnical components, like the igniter, motor and charges of the parachute system must be placed in this building. Since the Quick and Dirty flies with dedicated motors, very few motor preparations had to be done in order to be flight ready.
After the rocket was completely ready for the next day, we went to the bar in order to get a nice evening with lots of friends and cheap beer. Due to a lack of sleeping facilities on the military base, we slept in a Scouting-building a few kilometres from the base. This was organized last minute by NAVRO, many thanks for it!
Whole week the weather forecast for the launch day looked bad. But when we awakened on the Friday, the sun was shining and the wind was calm. This would be a great day to fly rockets! After a quick drive to the military base we went straight to the preparation building. A lot had to be done in the hours before the launch. Since the schedule was very crowded that day, the launch window was short and we only got one shot or else we would be shifted to the end of the day, with potential more wind!
So a lot was done and finally the rocket was ready. At about eight 'o clock in the morning the location transmitter was switched on and the electronics bay was sealed.
The parachute bay was closed and sealed with a nylon. The two rocket motors were inserted into the rocket and the two stages were connected. A new feature of this rocket was that the two stages were also connected by a nylon shear bolt, this in order to maintain a stiffer connection.
At about a quarter past nine the rocket was transported to the launch platform. The launch would be at ten 'o clock, so now the long waiting could begin. Due to time limitations there was no static display of the rockets for the public, so no photo shoot this time.
At about a quarter to ten they announced to us that the rocket could be placed in the launch rail, so we went down to the launch pad. After a quick inspection the rocket was placed in the rail. But then there was a problem. The retaining bolt for the launch rail was missing and was probably in the van, almost 350 meters away! Damn, the rocket, almost 12 kilo's, was getting heavier by the minute and we were looking for a bolt which would arrive at least 5 minutes later. It was time for a new and innovative solution: duct tape!
Now the rocket was hanging in the rail, it was time to insert the booster motor igniter. The rocket was ready to be armed. The arming plugs were inserted and the audio beacon was activated. Since the rocket was rather tall, the arming procedure was done by climbing on the launch tower itself! At last, the shunt clamp, which short circuits the upper stage igniter against premature ignition, was disconnected.
The rocket was now connected to the central ignition wire by Peter Heeren, the pyro-technician of the NAVRO. The rocket was now ready for launch!
After platform evacuation, we all retreated to the command post. The countdown was set, now it was time to wait.
After the ignition signal I pushed the button and the rocket reacted with a small puff of smoke. Within half a second, the smoke puff grew, and the rocket rose almost with a perfect straight line upwards. After four seconds, the second stage kicked in. This was only noticed due to the thickening of the smoke trial. The smoke generator did his job, giving approximately 12 seconds of smoke. The arc can be seen clearly in the pictures and the video.
The rocket was now descending. Since the weather forecast for this day wasn't very good, we simulated several flight options at home. In this way we could listen to the location beacon and know if the parachute was fully deployed, or that the rocket would impact into the ground ballistic. If the upper stage would land ballistic, the radio transmitter would be destroyed after 42 seconds.
So we hold in our breath and waited while the rocket plunged down to earth. It would reach a velocity of over 95 m/s and would then deploy its parachute! After the magic 42 seconds the transmitter was still working! This means the rocket was still in one piece!
After two minutes the transmitter signal died out. This was probably because the line of sight was lost.
So we went searching in the field, of course under close supervision by the military. After several hours of searching the homing signal was thought to be heard several times, but since other signals on the same frequency were significantly louder, a good position fix was impossible.
During our search in the field we found the ballistic booster section of the rocket. This part was supposed to go ballistic and it was a bit of a miracle that we found it back again.
Damn! A perfect flight but we have lost the rocket, because of a bad receiver which wasn't selective enough! Also the whole homing system wasn't working up to standard, so we will have to investigate a better homing system. Now the only thing we could do was keep our fingers crossed and hope it will be found by the military. Also, if the rocket would have been cracked at the landing and a very heavy rainstorm would cross the field, it is probable that the delicate flight computer will be ruined.
After a few days we received a call from NAVRO. The military had found the rocket! It was also in reasonably good shape! Only the coupler was damaged because of the zipper-effect of the high velocity opening! Fortunately fellow NAVRO-member René Hofsteden was near the artillery base so he could pick the rocket up and transport it to our region of the country. Many thanks!
When I received the rocket, the electronic compartment looked in excellent shape, only some paint was missing. The audio beacon had gone silent, but after fiddling with the switch, some minute sound was coming out of it again. The flight computers were in proper shape, and nothing had come off. Only, which was odd, the switch to activate the 433 MHz. transmitter was in the off position! Probably this had something to do with the shock load on impact. It's odd because I thought I heard the transmitter for two minutes. This is another reason why we should audio-tape the whole event in the future.
Now the interesting part of the story. After downloading the flight data from the flight computers we were astonished. The upper stage clocked an altitude of 2304 meters! That's amazing and probably a record!
But how is this possible since our simulation and the simulation of NAVRO did predict an altitude of only 1800 meters. This can only caused by two reasons:
- The motors produced way more impulse than required
- The drag of the rocket was less than anticipated
If the motors produced way more thrust, the rocket would gain a much higher burnout velocity. The burnout velocity of the rocket was only slightly higher than predicted.
If the drag was significantly reduced, the rocket would reach a somewhat higher burnout velocity, but it would coast to much higher altitudes. After some trial and error with our simulation, we could get the same results with a significantly lower Cd. The Cd would be in the range of 0.42 instead of the usual 0.75. That is a dramatic improvement, which could be credited to:
- The nosecone and the shoulder of the rocket were extremely smooth. This is the place where the boundary layer is still pretty laminar and attached to the body. After this the boundary layer will turn turbulent.
- The attachment bolts of the different compartments were countersunk into the rocket fuselage, a reduction in frontal area and Cd.
- The rocket was emitting smoke in its coast phase, this fills the wake of the coasting rocket, therefore reducing the drag of the rocket.
Further testing should be done in order to confirm these findings.
In all, a lot is learned from this project! This project style will be the blueprint for our following projects, since spare time will be a valuable and a scarce thing. Also the building style will be remembered for future projects. Of course, the rocket will not be fit for flight again.
All in all, this was a nice project with a lot of lessons learned. Surely a welcome relief after the Spectre IIb project which spun out of control (quite literally in flight trajectory terms and also in project management terms).
Many thanks to all the people who helped us at the launch day: Nick Appelman and Fred van Arkel for the photographs and Thiemo van Engelen for his quick PaDS software debugging.