Markus Bindhammer has performed additional research on the mannitol-based eutectic propellant including ignition of the propellant in the hot molten phase, strand burn testing (at ambient conditions), flash freezing of the propellant, as well as density/volumetric calculations. The results of Markus's research continue to be highly interesting: Eutectic Sugar Propellant Research Part IV
Markus continues to show his generous support for SS2S (and sugar propellant development in general) by providing a grant of $5000 USD to fund research of the eutectic propellant formulations. Deemed "ResearchSShot", the goals of these endeavors are foreseen to include:
a) Evaluating safety risks of liquid eutectic oxidizer/sugar alcohol propellants, minimizing safety risks as much as possible
b) Evaluating and comparing performance characteristics between the standard KNSB and KN-NaN-SB or MT (mannitol) propellant
c) Evaluating if complete forward/aft grain can be produced at once (no segments) with eutectic propellant/oven method in regard of exSShot dimension
d) Building 'small' rocket (MSS or smaller) with eutectic oxidizer/sugar alcohol propellant
Rick Maschek has continued dissection and cleaning of the DSS BP rocket motor components. The nozzle was determined to be in excellent condition and fully re-usable.
An analysis was performed which indicated a possible reason for the much greater degree of erosion of the nozzle ablative liner that was seen, in comparison with MSS. The propellant mass flux was calculated for both DSS BP and the MSS motors. The "mass flux" is the combustion product mass flow-rate per unit area of the grain core. It was determined to average over 5x greater than MSS during the first second of burn. It is clear that some development work is high on the agenda to modify the ablator for much greater resistance to erosion.
Hans has completed a draft report dealing with the pairing of pyro devices and flight controllers for DoubleSShot. Each of the flight controllers have their own characteristics, and the pyro devices should be controlled by the most suitable flight controller for the task. Additionally, the report deals with the nature of the recovery process. The recovery strategy has a deep impact on the chute deployment criteria, which in turn affects which flight controller will be most suitable for deployment of each chute (drogue & main).
The propellant was heated up to 170°C till it was completely liquified, then ignited with a sparkler. It showed that one spark was enough to ignite the propellant. The propellant deflagrated in a split of a second.
The high burn rate of the liquid propellant and the low viscosity makes a liquid eutectic oxidizer/sugar alcohol based rocket engine feasible. In its simplest form the rocket engine could look like following sketch:
Highlights of recent developments on the DoubleSShot project
Markus Bindhammer has provided two follow-up reports detailing his latest experiments with eutectic formulations. Mixtures of potassium nitrate, sodium nitrate and mannitol were studied as was potassium nitrate, sodium nitrate and sorbitol. The mannitol formulation was found to be non-hygroscopic at the humidity levels considered. These eutectic formulations are of particular interest due to the low viscosity of the melted product, which allows for simplified casting:
Rick Maschek has begun the process of cleaning, photographing, measuring and careful examination of the various recovered DSS BP motor components. Rick’s examination and measurements of the aft casing indicate that:
1) Rupture due to over-pressurization with initial failure occurring at the casing forward end. The casing ripped into several pieces.
2) Suffered permanent radial deformation due to high pressure (est. > 2000 psi).
This coming weekend, Rick will similarly examine the Forward Casing and Midbulkhead, currently in storage at the FAR site. Rick removed the nozzle from the aft section of the motor in order to examine its condition and that of the ablative liner. After removing the liner and giving it a scrubbing, the "star" shape of the burn pattern is striking.
Surprising is the degree of ablation, considering the burn time was only 1 second. The ablative liner on the MiniSShot nozzles consistently survived the 3-4 second burns very well, with much less erosion. The formulation was modified slightly for the DSS BP motor:
This small change would seemingly not account for the greater erosion, however, some testing will be needed to resolve this inconsistency. It is possible that the anomalous behavior of the motor could have played a role.
Alberto Gassol has begun updating the Showcase pages of the SS2S website and has added a DSS gallery page.
Hans reports that he has basically completed the investigation of when to release the drogue chute, with the follow-up task being to pair the pyros with the suitable avionics devices.
Rick Maschek has started to construct a dedicated "ignition controller" box for SS2S usage. This box will be specifically tailored to ignite dual-phase motors, having two pyro channels and two additional channels for triggering other events such as high-speed video cameras. Emphasis will be placed on high reliability. In the past, we've always relied on "borrowed" hardware to ignite our motors.
Highlights of recent developments on the eXSShot project
Markus Bindhammer has generously fulfilled his commitment to further endorse the SS2S program with a donation of $10,000 USD for funding in support of the eXSShot project. Rick Maschek reports that the funds have arrived into the SS2S bank account. Back in November of last year, Markus rocketed the DoubleSShot project forward at an accelerated pace with a $10,000 donation. This latest exciting development means that we can breathe a little easier knowing that once DSS wraps up to a successful conclusion, we will be on solid financial ground to keep the pace going unabated. A mere "thank you" to Markus would seem to be such an understatement.
Eutectic KNO3-NaNO3-Mannitol propellant was made with the same method described here. Mannitol has the lowest solubility in water from all sugar alcohols, therefore it is very less hygroscopic. The cured propellant has a density like ceramic. It deflagrates similar fast as using sorbitol but whitout bright white flame and a lot of white smoke is generated.
Cured propellant chunks:
As the state of matter of the propellant during manufacturing is liquid, carbon fiber, cellulose fiber etc. could be inserted to reinforce the propellant.
The following report was compiled based on input from Paul Avery, Rick Maschek, Chris King and Thomas Dittman:
Rick Maschek and Paul Avery arrived at the FAR test site Friday evening. The skies were overcast with the threat of rain. The forecast was similar for Saturday. As they were unable to access supplies that were locked in one of the storage lockers, work was deferred to the next day. Assembly of the propellant grains began Saturday morning. Rick reported that assembly of the 12 grains into two “unigrains” went well. Meanwhile Paul worked on assembly of the motor, while Chris King and Tom Dittman (who arrived early Saturday morning) set up the measuring equipment and calibrated the pressure sensors, with Paul’s help. Paul reported that assembly of the motor went well but took a lot longer than anticipated. There was only one significant glitch – an interference of the head of the Deluge Plug with the top of the propellant stack. This was resolved by local removal of some propellant. At around 5:30PM, the assembled motor was moved to the Large Horizontal Test Stand followed by final positioning and mounting. By the time this was completed, the weather had worsened. Storm cells with lightning approached, and for safety, the team retreated to shelters as rain began to fall. Rain continued, and the team waited for a break in the weather. The precipitation was a
mixed blessing, Rick later stated, as the wet ground minimized risk of brushfire in case of motor CATO. After about 2 hours, the break came, and the team quickly set about hooking up igniters and activating data recording. It was fully dark by this time and spotlights were used to illuminate the test site. The crew and all others present retreated to safety inside the concrete bunkers. At about 7:50PM, the “T minus 10 seconds” countdown commenced and at "zero" the motor was seen to fire up. Thrust buildup was slower than expected, but after about a second, the motor appeared to be at full thrust. Due to the darkness, a flame was clearly visible. The motor continued to burn well for another second or so when suddenly a violent CATO occurred. The aft chamber separated at the Midbulkhead and departed the test stand. A large fireball erupted from burning propellant, and pieces of burning propellant were seen to burn for several seconds. The firing crew decided to stay put in the bunkers for ½ hour as a precaution, since it was unclear whether propellant was present in the forward chamber or not. As well, rain once again started to fall, quickly extinguishing any fragments of burning propellant. Approaching the remains of the motor in the test stand, it was clear that the forward motor casing, which still had the Midbulkhead attached, was devoid of propellant and as such was not a potential hazard. After gathering the instrumentation, the team retired for the night.
The following day, Rick and Tom examined, photographed and collected various parts. The test stand suffered significant damage to the carriage and bracketry for retaining the motor. The Forward Bulkhead was damaged, having forcibly impacted the thrust plate. All sensors were damaged. Rick reported that the forward motor casing was “ballooned” noticeably, and oddly, was completely “clean” inside, devoid of any traces of propellant or casting tube material. The aft casing was recovered but was badly damaged at the forward end, having separated into several pieces. The nozzle appeared to be undamaged. Rick also reported a vast “debris field” of unburnt propellant chunks and fragments. The sizeable pieces were collected and the smaller pieces buried out of safety concern.
Chris was successful in recovering data from the load cells and pressure sensors. Both load cells appeared to provide a good trace. One pressure sensor (that believed to be for the aft chamber) recorded a slight pressure rise then dropped to zero well before the anomalous event. It would appear to have gotten blocked with combustion product residue (to be confirmed later). The other pressure sensor read zero until the anomalous event broke its electrical leads. It is believe the sensor leads may have gotten wet from the rain and as such malfunctioned.
Video of test firing:
A huge "thank you" goes out to the DSS ground crew members Paul Avery, Rick Maschek, Chris King and Thomas Dittman for the incredible effort they put into this static firing event, pouring their hearts and souls into making everything come together. This is the kind of rare dedication that will ensure victory in achieving our goal of reaching Space on the understated power (!) of sugar.
The Sugar Shot team owes a debt of gratitude to Ted Rothaupt (FAR secretary & Pyrotechnic Operator) and John Newman (Pyrotechnic Operator) for staying around so late Saturday night to oversee our project. FAR’s support is invaluable, providing such a rare and capable facility. SS2S will be donating $400 to FAR to help cover expenses incurred by our team and to show our support for such an outstanding facility. The SS2S team encourages our supporters to likewise make a donation.
Markus Bindhammer has been performing interesting experiments with novel propellant formulations, the latest being a eutectic mixture of KNO3 and NaNO3, with sorbitol. Markus found that the resulting formulation burns vigorously, and possesses a number of potentially useful traits. Markus’s report has been posted on our Documentation page.
Craig Peterson has completed construction of a vacuum chamber that will be used for component and assembled avionics testing of the DSS payload. The vacuum is intended to simulate the reduced air pressure at 33 km altitude (=1% that of ground level). The vacuum chamber, measuring 6” (150mm) ID and 40” (1000mm) long, also features an airtight 24-pin connector to allow interfacing of the test article to externally mounted equipment.
Jacob Ferriera reports that he has received the software disc sent by SolidWorks loaded with donated CAD based drawing and analysis tools. In return, Dassault Systèmes SolidWorks Corporation has been added to our Sponsor page.
The Documentation page has been updated with three DSS BP technical documents.
Put 5.4g KNO3 and 4.6g NaNO3 into a beaker (Borosilicate glass!)
Mix the two substances
Put the beaker with mixture on laboratory heating plate with temperature sensor and thermostat, insert temperature sensor into salt mixture
Pre-set the temperature to 220ºC
Heat till 220ºC are reached and salt mixture is liquefied (the theoretical melting point of the eutectic mixture is 218ºC but my mixture was already completely liquefied at 180ºC, maybe due to some impurities)
Add slowly 5.4g sorbitol, stir with glass rod till the sorbitol is molten and ‘dissolved’ completely in the salt bath.
Pour the solution on a coated baking paper. Be careful, it has a viscosity nearly like water!
Let it cool down for 10 minutes
Ignite the mixture with a butane torch. The mixture is very difficult to ignite due to its high heat of fusion (nearly like thermite)
Heated on lab hot plate with temperature sensor till a temperature of 130 °C was reached
0.5g candle wax added for impregnation (hygroscopy). Interestingly the wax dissolves completely in the molten salt bath, but a wax with a melting point of 110-120 °C would be better.
Slowly 6g sorbitol to molten salt bath added, stirred till sorbitol was completely molten and dissolved
Poured on a coated baking paper, strand formed (latex gloves!)
0.5g resin and 0.5g hardener (5min epoxy) dissolved in 5ml isopropyl alcohol
3.5 fine powdered KClO3 added and stirred till it was a homogenous paste
0.5 fine powdered sulfur added, stirred again (mixture must be always wet!). Strong sulfur smell occurred. Epoxy, KClO3 and sulfur mixture precipitated after 2min from left isopropyl alcohol. Sulfur seems to react with the curing agent and accelerates hardening process.Yellow coloring of mixture due to sulfur disappeared during curing process.
Separated from remaining isopropyl alcohol, strand formed, 3h cured
The plan is currently a GO for this weekend’s static firing of the DSS Boilerplate motor at the FAR test site in the Mojave Desert. As one of the final key preparations, Paul Avery successfully cast the “full” Delay Plug (recasting the “burnt” plug) and subsequently bonded it into place in the Midbulkhead. Two spare pyrogen igniters have been fabricated. Rick Maschek reports that he has procured the materials for constructing two motor Transport Cradles. The plan for this weekend is as follows. Rick and Paul plan to arrive at the site on Friday. Assembly of the grain segments will then take place, which involves bonding of the twelve segments into two “grain assemblies”. Following assembly, the grains will then be transported inside their respective motor casings to an assembly station where the motor will be partly assembled, then transported for overnight storage indoors. Chris King and Tom Dittman will arrive early Saturday morning and proceed to set up the instrumentation for recording thrust and chamber pressure. Concurrently, the motor sections will be transported to the Large Horizontal Test Stand, where final motor assembly will take place. The water deluge system will then be set up and pressurized. Due to the large number of events taking place at FAR this weekend, it is not certain as to when the actual firing will occur, presumably some time Saturday afternoon or evening.
Photo of Midbulkhead with Delay Plug installed (prior to application of edge inhibitor). The "channel" is to facilitate gas flow to the pressure sensor:
Two new guidance documents have been prepared for the upcoming static test firing of the DSS BP motor:
Sabalith® is a salt mixture of 65% KNO3 and 35% LiNO3. The mixture is normally used for salt bath curing in open or closed circulations, e.g. in LCM installations for the vulcanization of rubber. The melting point of the Eutectic system is approx. 130°C (266°F). This could make it interesting for propellant applications, e.g. producing a very homogenous solution of molten sugar/sabalith.
Upon thermal decomposition, LiNO3 gives lithium oxide, nitrogen dioxide, and oxygen:
4 LiNO3 → 2 Li2O + 4 NO2 + O2
Other group I nitrates decompose differently, forming nitrite salt and oxygen:
2 KNO3 → 2 KNO2 + O2
A first experiment using the molten salt mixture as a solvent for the fuel (sucrose) was performed as following:
- 6.5g KNO3 and 3.5g LiNO3 mixed in a beaker
- 20min in the baking oven at 160°C under air circulation mode
- 5g fine powdered sucrose added after salt mixture got liquid, stirred till it got a homogenous white paste
- Poured on a coated baking paper, cooled down to room temperature
Eutectic system mixture of 6.5g KNO3, 3.5g LiNO3 and 5g sucrose:
Combustion of the propellant probe:
With this method solid and castable black powder could be made. Just liquefy KNO3/ LiNO3 and add sulfur (melting point 115.21°C, 239.38°F) and charcoal powder. Instead of sucrose sorbitol will be used for next experiments, as the melting point of waterfree sorbitol is 110–112°C, which leads to a blend of oxidizer and fuel. The biggest drawback is the hygroscopy of LiNO3. This could be avoided by coating the propellant surface after casting with cellulose nitrate lacquer.
Update 2011-9-7
First try to produce cast able black powder by the Eutectic system method:
Used ratio: 6.5g KNO3/3.5g LiNO3/2.2g C, 1.4g S
KNO3/LiNO3 mixture starts to liquify:
Molten sulfur swimming on the KNO3/LiNO3 mixture like oil on water:
First casted batch of black powder:
Combustion test. A lot of molten Li2O remains. I will look into possibility to elute LiNO3 after casting with methanol or ethanol.
An old German chemistry book says, if you use a mixture of 54.54 parts KNO3, 18.18 parts NaNO3 and 27.27 parts LiNO3 the melting point drops to 120°C (248°F). This mixture ratio is preferable as it keeps the LiNO3 amount small.
1g phenolphthalein dissolved in 50ml methanol, 7.5g KClO3 and 1.5g hexamine dissolved in 50ml boiling water dest. Solutions mixed and methanol/water vaporized at 115°C in an evaporating dish. Milled again to fine powder with mortar and pestle.
