Fisher Space Systems LLC

Viper Rocket Trike

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Updated Dec 2023
01-31-2023: My objective for 2022 was to launch a class I rocket glider (the Mk I Viper). However, after a few launch attempts, I realized I didn't have enough thrust to exit the rail guide at the required velocity for aerodynamic control. I needed more thrust. As such, I spent the rest of the year working on scaling parameters to decrease ignition time and increase thrust. I've narrowed the scaling parameters down to three; initial surface flux, length to diameter ratio, and initial throat diameter. Also, I've upgraded my rocket engine test stand with reinforced concrete walls and a steel test frame on one of the walls. Read 2022 EOY Report

01-31-2023: This month, I collected all of my data and entered it into a spreadsheet. After two years of scattered data, I saw a trend in the rocket engine testing. I've settled on a rocket engine using a nozzle throat diameter is 6.0 mm and the rocket engine thrust is ~ 22 N. Over the next several months, I plan to test this design for consistency of time to ignition and thrust. Jan EOM Report

02-28-2023: This month, I did three test using the same scaling parameters. Although, the performance results are not as consistent as I'd like, the initial thrust is ~ 20 N at ignition and climbs to ~ 25 N toward the end of the burn. Twenty Newtons at ignition may be enough for aerodynamic control of the rocket glider as it leaves the rail guide. As such, it is my intention to launch the Mk I Viper next month. Feb EOM Report

03-31-2023: This month, I worked on the MkI Viper rocket glider. I broke the glider into three sections; a forward section, a mid section, and an aft section. I moved the servos from the mid section to the aft section and connected them directly to the fins. This shifted the center of mass of the rocket glider aft. To compensate, I moved the battery pack to the forward section. Next month, I'll finish the forward and rear cowlings and work on the paraglider. Mar EOM Report

04-30-2023: This month, I continued my work on the Mk I Viper. The total mass of the Mk I Viper including the propellants is now ~ 1.456 kg which gives me a mass margin of only 44 gm. I attached the paraglider to the fuselage. The wing loading is ~ 0.8 gm/cm2. Next month, I'll tweak the design and hopefully, do some drop testing. Apr 2023 EOM Report

05-31-2023: This month, I continued working on the drop tower and spent some time on marketing. I decided to use a 15 foot stepladder with an adapter at the top. Also, this month, I attended the National Space Society, 2023 International Space Development Conference in Frisco, Texas. I designed and printed out business cards and transferred the Fisher Space Systems logo and name to several polo shirts. The ISDC was interesting but not the venue for Fisher Space Systems at this time. A future market may exist for corporate spacecraft to reach a space industry for a few days to make the billion dollar decisions and then return home. May 2023 EOM Report

06-30-2023: This month, after several weather delays, I finally got to drop the rocket glider. Unfortunately, the tail section of the glider hit the safety straps, flipped, and crash landed. The impact bent the frame. As such, the rocket glider is no longer usable. That's okay because I've exceeded my mass limit anyway. So, it's back to redesign and a new frame. Also, I have to extend my launch tower adapter so that I don't hit the safety straps next time. Jun 2023 EOM Report

07-31-2023: This month, I used a lightweight generic soda stream bottle as the propellant/pressure tank for the Mk I Viper. The bottle failed the test at 40 psig. However, I found that Soda StreamŽ has a 500 ml bottle. It's mass is 26 gm lighter than the 1L bottle. Starting at 140 psig in both bottles, the calculated pressure difference is about 8 psig (~123 psig vs ~131 psig) at the end of the run. So, I'll have to test to see the effect on performance.

08-31-2023: This month, I repeated the test on February 23rd but used a 500 ml Soda StreamŽ bottle as the Pressure/Propellant Tank (PPT) versus the 1000 mL PPT. The objective was to test the performance of the rocket engine to see if there was a noticeable difference. All other parameters where the same as the 02/23 test. Time to ignition was 0.4 sec and burn time was 6.0 sec. I surmise that the short ignition time was due to the fuel core being stored in a dry bag for six months.

  Also, this month, I used the ignition surface flux scaling parameter (0.2 gm/cm2/sec) to designed a new 6-point star fuel core. The 6-point star configuration increased the surface area over the 5-point design. As such, the new fuel core can be made ~ 1.5 cm shorter than the 5-point design. The decrease in fuel core length will result in a mass savings for the overall flight system. Ignition occurred in 0.6 sec and burn time was 5.8 sec. The initial test results show a slight increase in performance over the 5-point design.

  Finally, I used an endoscope to take pictures of the PLA/KMnO4 fuel core after a test. The recession of the PLA/KMnO4 fuel core seems to be evenly distributed along the length of the fuel core. This implies that, if designed properly, most of the fuel core can be consumed in the burn. Aug 2023 EOM Report

09-30-2023: This month, I ran some test to study the ignition time of the PLA/KMnO4 fuel core after weeks of storage in a dry bag. There were three test, the first was stored in dry bag for ~ 6 months, the second for 24 days, and the third for 31 days. All other parameters were the same. Ignition times varied from 0.4 sec to 0.6 sec. The shorter the ignition time the longer the burn time for a given amount of propellant. The total propellant mass was ~ 115 gm, just under the FAA regulation for a class I rocket. As such, the procedure is to store PLA/KMnO4 hybrid fuel cores in a dry bag for a minimum of two weeks and as long as four weeks.

  Once again, the endoscope shows a nice even burn of the fuel core. The injector evenly distributes the spray around the fuel core. The cone angle of the spray is clearly visible and there is an even burn distribution. Sep EOM Report

10-31-2023: This month, I ran two tests without the check valve. As expected, there was an increase in both the chamber pressure and the thrust. Ignition time was about 0.3 sec and burn time was about 6.0 sec for each run. The graph shows an average chamber pressure of ~ 107 psia. The initial thrust was ~ 22 N and increases to ~ 28 N at the end of the run with an average thrust at ~ 25 N. Oct EOM Report

11-30-2023: This month, in an effort to get maximum thrust with minimum hardware, I ran two tests without the check valve and with a 7.5 mm nozzle throat diameter. The HTPE tank pressure was 140 psig. The first test streamed PLA out the nozzle and the second test blew up. Calculations show that the ignition surface flux (ISF) was ~ 0.3 gm/cm2/sec as compared to ~ 0.2 gm/cm2/sec on previous test using the check valve. Last month, the two successful test without the check valve was with the same ISF of ~ 0.3 gm/cm2/sec but with a nozzle throat diameter of 6.0 mm. I surmise that the smaller throat diameter slowed the flow rate enough for ignition to occur while the larger throat diameter did not. After careful consideration, I have decided to add the check valve back into the plumbing. Nov EOM Report.

12-31-2023: This month, I had three test with a 7.5 mm nozzle throat diameter. I added the check valve back into the plumbing. Bottom line, it didn't work. I will go back to a 6.0 mm nozzle throat diameter for the Mk I Viper. Also, this month, I added a color analyzer to my diagnostics to help determine the optimum starting concentration for infusion of KMnO4 into the PLA.
"Simplicity is the ultimate sophistication."
- Leonardo da Vinci
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Copyright (c) 2021 Jerry F Fisher
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