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Cirrus One Launch Report


Preparations

Saturday, 31 March, 2001 - Although work on the rocket had proceeded until late the previous night, I managed to complete the Cirrus One rocket before departure to the aRocket 1 launch event, being held in New Mexico the first week in April. For transit, the rocket was disassembled and packed in a specially built lightweight wooden box, together with the equipment needed for re-assembly and support of the launch. Some of the supplies had been shipped beforehand, such as the casting equipment and dried dextrose.
After a re-routed flight due to the Comair pilots strike, I arrived in Albuquerque, N.M. late in the afternoon. I then rented a car, and began the one-hour drive to my motel in Socorro.

Sunday 1 April - Friday 6 April - Preparation of the propellant took place on Sunday, and actual casting of the segments for the Kappa-DX motor took place on Monday. Brian Kosko and Ray Calkins kindly provided me with an ample supply of potassium nitrate, as well as providing the facilities for preparing and casting the propellant.

The rocket was re-assembled the following day, with installation of the altimeter and transmitter module, and packing of the streamer and parachute. Each component was carefully weighed. The motor weight was 5.61 lbs. (2.55 kg.) which included 3.22 lbs. (1.46 kg.) of propellant. The total (pre-launch) weight of the rocket was 12.5 lbs. (5.67 kg.).The rocket was prepped for a Wednesday launch. However, high winds ruled out any chance for a launch that day. In fact, the next two days had similar high winds, as well as rain showers. As I was scheduled to fly back to Toronto Sunday morning, it was decided to attempt a launch very early Saturday morning, just after sunrise, when winds are typically calm. Thursday and Friday were then "tourist" days for me.


Launch

Saturday, 7 April, 2001 - I arose just before dawn, quickly got dressed, loaded the rocket and support equipment into the car, then began the 40 minute drive from Socorro to the desert launch site (stopping along the way at McDonalds to pick up a large cup of coffee). I was the first one to arrive at the site. The weather was perfect, clear blue skies, no wind. The dew on the sagebrush was frozen, so the temperature had dipped quite low during the night. However, the sun was warm, so it felt quite comfortable. I proceeded to assemble and set up the rocket on the launch pad. Also, I set up the videocamera a few hundred feet from the launcher, and located the FRS receiver and tape recorder 0.4 miles (650 m.) away. I also took some photos while waiting for the others to arrive. Carl Blood arrived shortly after, and took photos of me posing with the Cirrus One rocket.

With the aid of a comprehensive checklist, I went step-by-step carefully prepping the rocket for flight, powering up the altimeter, setting DIP switches, armed the Streamer Ejection System (SES) and Parachute Ejection System (PES). Then the FRS transmitter was powered up and tested to confirm operation. The hatches were then installed over the access ports, and finally, the igniter was connected to the launch electrical system (after confirming the safety "shunted" condition).

We then took our respective places to observe the launch. I was located several hundred feet away, in order to photograph the launch effectively, and to obtain reasonable reception of the transmitter signal. Photographs were to be taken with my 35mm Pentax, using a 50mm lens and film auto-advance that allowed shooting at a rate of two frames per second.

Ray then gave the countdown, and made ignition contact at zero. About a second later, a puff of smoke appeared at the base of the rocket. Immediately after, Cirrus One roared off the launch pad, accompanied with a very loud sound from the powerful motor, and veered slightly after leaving the launch rail (doubtless due to the short 8 foot length and flexibility of the 1/2 inch rod). The motor burned for the anticipated two seconds, then the rocket coasted skyward at very high velocity, judging by the shrill sound. However, some seconds later a "pop" sound was heard, and an observer noticed the streamer had ejected and apparently torn off. Also spotted was a "silvery" object glinting in the sun, but this was most certainly the frangible cover of the SES ejection port, which was comprised of a section of aluminum tape. Several seconds later another "pop" sound was heard, apparently the parachute ejection charge firing. I heard through the receiver the "beeping" of the altimeter coded altitude output. The rocket had climbed out of sight by this point in time. About half a minute later, the rocket was spotted descending in a "ballistic" manner, without any deployed recovery device. The sound made by the descending rocket resembled that of a fighter jet passing overhead. I clearly tracked the rocket descending, in a stable nosedown attitude, and saw it strike the earth roughly one-half to one kilometre distant. The sound of impact was slight, suggesting that the rocket had struck fairly soft ground. Despite an intensive search, the rocket could not be found. It was likely buried down to its fins, and sagebrush and patches of tall grass made for a tedious search effort. It is well worth noting that the rocket could have been found readily and certainly had a simple Landing Locator device been employed to mark the location of impact.


      

      
Launch photos (click on image for enlarged view)

Post-flight Analysis

The altimeter functioned exactly as it was designed to, firing the SES and PES in sequence, followed by the audio coded output of the sensed altitude. The reason for the premature firing of the recovery devices was certainly not a fault with the altimeter, but rather, due to an incorrect design of the altimeter compartment. Due to time constraints with designing and building the rocket, this was not investigated with sufficient care. The altimeter compartment should have been sealed, with a number of properly sized static ports to ensure that the pressure sensed by the barometric transducer was that of the ambient pressure surrounding the rocket at any point during the ascent (details). The actual compartment did not have these ports, and was open to the base of the rocket, in hindsight, a flawed design. In fact, Ray Calkins, displaying his keen insight, pointed out his concern to me with regard to the compartment design. The good news is that this problem is easily rectified for future flights.

The FRS transmitter seemed to work well. I picked up the signal clearly with the receiver I had clipped to my belt. The second receiver located more distant (mounted adjacent to a tape recorder), however, did not fare as well. Examination of the audio tape revealed a broken signal with a great deal of "static". It was possible to distinguish certain sounds within the rocket, however. The motor firing and "whistling" sounds of ascent were quite clear, as were the "beeps" of the altimeter coded output, which appeared to indicate 1700 feet (520 m.) altitude when the altimeter was prematurely triggered.

Viewing of the videotape of the launch allowed the timing of various events to be obtained:

  • Liftoff: 0.00 seconds
  • SES "pop" sound: 6.0 seconds
  • PES "pop" sound: 12.1 seconds
  • Impact with ground: 52.5 seconds.
Bearing in mind that these times are excerpted from the videocamera recording, which was situated a few hundred feet from the launch pad. The actual times between events would have been less, due to the time duration required for the distant sounds to reach the videocamera microphone. Considering that the velocity of sound may be taken as 1140 ft/sec (347 m/sec), and that impact of the rocket was about 1500 feet (460 m.) away, the actual total flight time can be taken as 52.5 - (1500 /1140) = 51.2 seconds.

Interestingly, the actual flight time was identical to that projected at the beginning of the project by the SOAR altitude simulation program (for a ballistic flight) for the targeted altitude of 10,000 feet   (soar720.txt). However, the actual empty mass of the rocket was lower than that projected (9.1 lb. actual vs 9.7 lb. projected), and the propellant mass slightly less (1457 g. actual vs 1500g. projected). As well, the "tug" due to the streamer drag force before tearing off would have tended to reduce the peak altitude. This can be accounted for in the simulation by applying a "negative" thrust for a brief duration at the 5 second mark of flight. The magnitude of the required "tug" force can be determined (iteratively) by applying an arbitrary force, running (and re-running, as necessary) the simulation until the predicted flight time matches that actually measured. This analysis was performed, and the predicted peak altitude of the actual flight matched the target, being 10,139 feet (3091m.)  (soar721.txt).

Although the PES ejection charge fired (based on the second "pop" sound), the parachute likely did not deploy, and remained within the rocket. This is not a surprise, considering the high speed of the rocket at the time, and the substantial dynamic pressure acting on the nosecone. In all likelihood, the nosecone also remained in place, displacing only enough to vent the ejection charge gases.

Despite the partial success of the flight, the highlights are notable:

  • The actual peak altitude was undoubtedly close to that targeted.
  • The Kappa-DX motor performed perfectly, on this, its maiden flight.
  • The rocket vehicle was structurally sound and stable. The augmentation of stability by slight "spin" induced by unsymmetrical airfoils, seemed to work as intended. Despite the initial slight veering due to the short launch rod, the rocket climbed very straight, as is evident from the launch photos.
  • The altimeter functioned well, effectively firing the two-stage recovery charges.
  • The streamer ejection system evidently worked well, despite the high velocity at deployment.
  • The FRS transmitter functioned reasonably well, although its range was less than expected.

Update -- March 20, 2003, Cirrus One Recovered !

On Saturday, March 15, 2003, nearly two years after Cirrus One soared skyward over the New Mexico dessert, and subsequently was lost (seemingly forever), rocketeer Denzil Burnam made an unexpected discovery of the wreckage of a rocket...later identified as the remains of the Cirrus One rocket. Here is the message, and one of the photos, that he sent to me...

"This Saturday, after strolling 1.1 miles at 357 degrees from the Antelope Flats launch site east of San Antonio (NM) to retrieve a wayward rocket we headed back towards the range head. About 100 feet west-south-west we came upon a finely crafted motor casing encrusted in dry mud with an unbelieveable nozzle inside. We also retrieved a few airframe fragments nearby but I failed to think about the nose cone until we were well away from the area. I'll have to look again sometime. As we were walking back I remembered Dave Johnson telling us that the rocket had landed due north but after a lengthy search hadn't been found. The parts just had to wait in the sun for about two years to get back in the shade."


recovered wreckage

Last updated

Last updated  March 20, 2003


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