By Dave Nordling, President, Reaction Research Society
The society had a small work event at the Mojave Test Area on August 4th, 2022. The purpose was limited to starting the build of a new launch pad foundation for Bill Claybaugh’s upcoming large solid motor powered vehciles. The summer heat and tough soil limited progress but it was useful to gauge what the next steps should be. Launch is scheduled for mid-October.
Joe Dominguez (right) and Bill Claybaugh (left) examine the levelness of the form work.
Many thanks to Rushd Julfiker and Joe Dominguez for volunteering their support to Bill on that day. A new diflucan and larger launch pad is designed to support Bill’s larger adjustable launch rail system which will be useful to the larger sizes of future rocket projects at the RRS. New developments will be reported in order xanax the near future.
EDITOR’S NOTE: This article may be revised or expanded at a later date. As part of the second of three reports on this topic, this is a brief paper on the increased propellant density available from using IDP with some mention of the importance of post-mixing shaking (vibration) and vacuum-based degassing.
Two changes were made to the propellant for the 6-inch flight vehicle, as compared to the previous static test motor: one chemical, the other process-related. These two changes resulted in an increase in the flight motor’s solid propellant grain density.
The previous static test motor propellant used DOA (Di-Octyl Adipate) as the plasticizer. For this mixture, we substituted IDP (Iso-Decyl Pelargonate) on a 1:1 basis. This change in plasticizer resulted in a noticeably less viscous mixture whereas previously the mix had been a “thick and sandy” wet solid that did not slump. This new mixture while also still “thick and sandy” was noticeably given to slumping when moved from the mixer to bowls for compacting into the motor.
Previously, the propellant had been put under a vacuum for ten minutes between final mixing and the beginning of packing the wet propellant into the motor. This process had no noticeable effect on density compared to the previous mixes which did not use vacuum degassing.
For this mix, vacuum was limited to five minutes but was applied at the same time as the mixing bowl and contents were strapped to a shaker table that vibrated the wet propellant mix both vertically and in one horizontal plane. When the vacuum cover was removed from the bowl, the mix showed obvious signs of degassing, including both numerous surface “craters” as well as an about one-half inch gap between the propellant mix and the walls of the mixing bowl.
Electric powered shaker table for degassing batches of solud propellant mixtures
Upon completion of packing the propellant into the motor it became clear that density had been increased. The total propellant load was expected to be just over 51 lbm. but was clearly higher because we had much less surplus propellant mix left after casting than expected.
Weighing of the motor following curing and post-processing confirmed the suspicion of the previous afternoon that the net propellant mass was 54.2 lbm for a density of 0.0593 pounds-mass (lbm) per cubic inch, an about 5% gain over the previous 0.0564 lbm / cu. inch.
We thus concluded that while applying vacuum after mixing but before casting has little effect on density; vacuum with shaking does result in some degassing of the propellant mix when combined with using IDP for reduced viscosity. We also note that propellant density remains about 3% below the theoretical 0.061 lbm / cu. inch that could be realized when mixing under vacuum rather than only applying vacuum and shaking after mixing. Given the very high cost of vacuum mixing equipment and the impracticality of using such equipment in the field, there is a relatively small gain that could be achieved compared to using the present method. We conclude that post-mixing processing under vacuum with shaking is a lower cost alternative that provides some gain compared to open-air propellant mixing without (https://conciergedentalgroup.com/order-phentermine-37-5-online/) degassing.
View of the finished propellant grain from the head-end.View of the propellant grain from the aft-end showing the four-finocyl grain design.
In a remarkable demonstration of persistence and luck, RRS President Osvaldo Tarditti was able to find the spent booster rocket. A few photos were captured of the recovered rocket.
Bill Claybaugh’s recovered spent booster casing brought back to the Mojave Test Area (MTA)Closeup on the bulkhead shoved into the aluminum case of the booster from the impact.The fins look great and the nozzle was recovered.
Based on the impact location, it was possible to reconstruct a possible flight trajectory by assuming the motor performed as designed and further assuming the front of the vehicle was a flat plate and that the mass did not include the mass of the payload. We know from video, telemetry, and recovery of the payload that the payload separated from the booster about one second into the flight.
The recovery location on the map shows a northeast trajectory as confirmed by launch footage.
This analysis suggests a burnout velocity of about 1550 feet/second with a peak altitude of about 21,200 feet given the known range of about 14,300 feet. This analysis gives a flight time of about 74.5 seconds and an impact velocity of about 820 feet/second.
Given the observation that the vehicle stopped in about 2 inches (based on the depth of the depression in the hardpan) before falling on its side; we can estimate the impact deceleration. Given an average velocity during impact of about 410 feet/second because the final velocity is zero and it took only 0.167 feet to come to rest, it follows that the impact occurred over 0.000407 seconds. This, in turn, indicates an average deceleration of about 31,250 g’s.
The reason for the vehicle turning to the Northeast starting at about 0.20 seconds into the flight remains unclear. There is no evidence either in video or in images of the recovered hardware of any hot gas leak nor of any transient thrust vector anomaly. The wind was less than 5 miles per hour and from the Northwest; if it had caused a turn, we would expect it to be toward the Northwest, not the Northeast as observed. The only plausible theory at this time is that part of the belly-band became embedded between the nose of a fin and the rocket body causing the turn via differential drag and then fell away from the vehicle, causing the resumption of normal flight. Once the recovered hardware is available for inspection, we will test each fin nose to see if a gap exists that might have caught the 0.020-inch thick belly-band.
The recovered payload segment was examined after it was found just north of the launch site.
It also remains unclear as to why the payload separated about 1 second after launch. The recovered payload showed that both initiators had fired (by design, if one fires the other is ignited; thus, only one signal is required to fire both) but did not show any evidence of having been “swaged” or otherwise subject to being forced off the rocket by aerodynamic or other forces. Neither does the matching front end of the rocket show any evidence for the payload having been forced off. We thus conclude that one of the flight computers ordered the firing of the initiators.
The bellybands being fit checked in the launch rail.Recovered bellybands have evidence of tearing from what is likely fin impact.
However, the main flight computer stopped working just after 0.80 seconds into the flight for an unknown reason after recovery it was still connected to its battery, which showed the expected 3.87 volts. Further, the limited data recovered from that computer shows that it did not initiate separation of the payload: the firing circuit shows continuity throughout the period that the computer was operating and separately records that no signal was sent by that computer.
Still image of the rocket just after launch making the unexpected hard turn.
This points to the backup flight computer. That hardware is currently at the manufacture for repair, after which we hope to extract continuity data with regard to its firing status. Hopefully, once that and other data is available from the backup computer we will be able to establish when it ordered the separation of the payload, and why.
Recovered payload with the main and backup computer.
A second update to this firing report is expected. The booster has been packaged up for a more detailed inspection.
