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2011-11-28

Sugar Shot Weekly Activity Report: November 14-27, 2011‏

Paul Avery and Rick Maschek performed the third round of development testing of Paul's pyrogen units for the upcoming DSS BPS motor test. The firings looked good, delivering the required "mass flux" within the design burn time. The units are being tested at ambient conditions, and will have a shorter burn once enclosed in a motor.
Serge Pipko performed the first "hot batch" ignition testing of the experimental eutectic propellant on November 27th. The resulting deflagration was impressive, and provides important insight into the need for special precautions when preparing larger batches of this formulation. Serge's preliminary report and video: http://serge77.rocketworkshop.net/knnnsb_ign/knnnsb_ign.htm
During a recent visit to California, Richard Nakka had a "long overdue" opportunity to meet with some long-serving members of SS2S. Rick Maschek and Paul Avery met up with Richard in Hemet, had lunch together, discussed rocketry and SS2S in-depth, and enjoyed a "show & tell" of SS2S rocket hardware.
After a tasty lunch at Coco's restaurant (left to right, Rick, Paul & Richard):
Rick's wife Barbara (left) and Richard's wife Pauline, at Coco's:
Posing next to the DSS BPS rocket motor casing:

2011-11-21

More eutectic KNO3/NaNO3/Mannitol propellant static test firings

My good friend Rick Maschek performed some more static test firings with eutectic KNO3NaNO3/Mannitol propellant (PSNM):
 

2011-11-06

Sugar Shot to Space KNO3/NaNO3/Mannitol propellant test

First Motor test of eutectic KNO3 / NaNO3 / Mannitol propellant by Rick Maschek. 182 grams of propellant in a five Bates grain arrangement. Test conducted at the FAR site, Mojave Desert California, USA on Nov 5, 2011 in support of the Sugar Shot to Space project.


Second static test firing will be done with a 390g motor, then 1kg. A first flight with a 1kg motor is scheduled for November 19th.

2011-11-01

Reaction of vanillin with ascorbic acid

5g vanillin were heated in a 100ml beaker to 130°C, then 1g ascorbic acid dissolved. The mixture turned dark green after stirring it for several minutes. The reaction product is a soft, clear and elastic compound:

Reaction could be used to prove the existence of ascorbic acid or vanillin if color change arises not from impurities like nickel or chrome.

About an hour later the compound suddenly started to crystallize:
To avoid any contamination with metal ions, 5g vanillin and 1g ascorbic acid were placed into a fresh cleaned beaker without support of spoon or spatula. The mixture was then heated to 130°C. The temperatur sensor, which has a stainless steel jacket, was precautionary placed outside the beaker. The mixture was stirred with a fresh cleaned glass rod. The solution turned green after stirring it for 5 minutes and the ascorbic acid was completely dissolved in the vanillin.
To determinate if vanillin itself would turn green after heating it to 130°C for several minutes, the experiment was repeated without adding ascorbic acid. The vanillin turned slightly yellow after 10 minutes heating but not green. An idea is that the green color  occurs not caused by a chemical reaction but rather by a special crystal configuration of vanillin and ascorbic acid. Example: anhydrous copper (II) sulfate crystals are grey -white, but if they containing water, the appearance is blue.
If pure vanillin get heated to 130°C for 20 minutes, the color change to yellow-orange. After cool down vanillin crystallize out immediately and scalelike. If ascorbic acid is added to pre-heated vanillin, the color changes not to green and the solubility of ascorbic acid is decreased. However, after cool down a soft, clear and elastic compound was found too.


Update November 12, 2011: Uploaded an extended article (in German) about this topic on scribd.com

Update November 19, 2011: Uploaded an edited version of the article here.

2011-10-30

Reaction of sorbitol and ascorbic acid

Newer experiments show that sorbitol and ascorbic acid split at a temperature above 140 °C  probably into  following aldehydes:

- Benzaldehyde
- Cuminaldehyde
- Formic acid

2011-10-20

Benzaldehyde from sorbitol and ascorbic acid?

During my experiments with molten mixtures of ascorbic acid and sorbitol I found - if the mixture was heated to a certain temperature range - that a liquid condensed on the cooler parts of the glas which had a strong and sweet odor of bitter almond.
The experiment was then repeated with a distillation apparatus as shown below. The result after heating the mixture for 10 minutes at 140°C was a tar like residue and a yellowish liquid distillate. The distillate had a strong odor of  bitter almond, the residue a caraway odor.

It could be also possible that salicylaldehyde or furfural has been synthesized as it has a bitter almond odor too.
Unfortunately the Fehling test was negative for the distillate as it is not sensitive enough for such small amounts.

2011-10-18

Sugar Shot Weekly Activity Report: October 10-16, 2011‏

Highlights of recent developments on the MiniSShot project

Flint Hapirat has completed a draft of the Launch Report for MSS-2, and has submitted the draft to Richard for review.

Highlights of recent developments on the DoubleSShot project

Richard Nakka and Blair Nakka have completed machining the Forward Bulkhead for the new DSS BPS motor.
The large 1.25" (3.2 cm) hole is for a frangible burst disc to prevent overpressurizing the cavity between the Forward Bulkhead and the Delay Plug in case of significant blow-by.
 
Paul Avery has completed the design of a new and more powerful pyrogen unit for the DSS BPS motor. Paul reports that he has decided on a size, and has:
1. ordered delrin mandrel stock
2. rolled several casting tubes
3. machined an aluminum base and top cap for a casting stand
 
This past Sunday, an avionics telecon was held to report progress and determine upcoming actions. Participants in the telecon were Chris King, Rick Maschek, Matt Campbell, Hans Olaf Toft, Mattias Lampe, Craig Peterson and Richard Nakka. Chris reported that he has completed a draft of the revised DSS Avionics Requirements document, which was submitted to Richard for review. Chris also completed a draft of a test plan for "high altitude" testing of batteries that will tentatively be used for the DSS flight. The testing will be done by Craig utilizing the vacuum chamber that he recently built.Rick provided good input on potential video cameras for the flight, such as the USB "spy camera" model.

Mattias reported excellent progress on the ring antennas that he has prototyped. The first image shows the PCB with the antennas laid out. The third image shows the prototype ring antennas cut out. Mattias plans to conduct testing of the antennas in the near future, including an assessment of any interference with the GPS antenna that will be mounted forward of the ring antennas in the nose cone.The next avionics telecon will be on Sunday, Nov.6th.

Marc Davis has once again volunteered to produce CAD drawings of the DSS BPS motor parts. Marc has completed the casing drawing which was forwarded to Randy Dormans. Randy has procured the 6" (15cm) steel tubing for the casing and reports that "all hole locations are indexed and I am currently in the process of drilling to them to the final diameter (three passes each).  The casing should be finished by this weekend."

Marco Torriani reports that the prototype DSS "test fins" have been mounted on a 400 mm four-layer fibreglass tube which he recently fabricated.  Marco has bonded the fins' "foot" and laid carbon fibre over the aluminum foot to reinforce the attachment point. Marco also reports that he has performed an empirical load test on the fibreglass tube, loading 140 lbs (64 kg) with "no problem" Once the epoxy will be fully cured Marco will do a similar (ad hoc) testing of the fins with 100 (45 kg) lbs "just to make sure" before the fin/tube assembly is shipped to Bert Kimpe for official structural load testing.

2011-10-13

Sugar Shot Weekly Activity Report: October 3-9, 2011‏

Richard Nakka and Blair Nakka have begun machining the Forward Bulkhead for the new DSS BPS motor.
 
Paul Avery has begun designing a new and more powerful pyrogen unit for the DSS BPS motor. The new unit is roughly double the size of that used for the DSS BP motor to ensure a rapid start-up.
 
Markus Bindhammer has performed additional research into eutectic propellant formulations. The latest experiment deals with the production of Golden Powder, which refers to a mixture consisting of potassium nitrate as an oxidizer with ascorbic acid as a fuel: Eutectic Sugar Propellant Research Part V

Based on feedback, Hans has updated the report Flight Controller and Trajectory Map.This document deals with the pairing of pyro devices and flight controllers for the DoubleSShot flight, andadditionally deals with the nature of the recovery process.

2011-10-04

Eutectic KNO3-NaNO3-sugar alcohol as an explosive‏

According to Captain Bertrand R. Brinley's 1960 book, Rocket Manual for Amateurs, chapter 3, page  96-97, increases the power of an explosive as the cube of the weight. "Two ounces of an explosive is 8 times as powerful as one ounce. Three ounces is 27 times as powerful. Five ounces is 125 times as powerful."
We have seen how 3g 170°C hot liquid  eutectic KNO3-NaNO3-Mannitol deflagrates. If this rule of thumb is true, 1kg liquid  eutectic KNO3-NaNO3-Mannitol would be around 3333 = 36926037 as powerful as 3g. Difficult to imagine, but if it is even much less, hot liquid  eutectic KNO3-NaNO3-sugar alcohol could be considered (and used) as an explosive. Solid eutectic KNO3-NaNO3-sugar alcohol is cheap, very easy to manufacture and safe to handle.
Liquid  eutectic KNO3-NaNO3-sugar alcohol could be cast in an according heat- and pressure-proof container. The container would then be closed after the eutectic KNO3-NaNO3-sugar alcohol is hardened and encased with a heat up charge (end burner configuration). While the heat up charge burns away it would heat and liquefy the eutectic KNO3-NaNO3-sugar alcohol inside the container. It would need to be determined, which effect the pressure increase in the container has on the melting point of the KNO3-NaNO3-sugar alcohol. However, the pressure increase will increase the burn rate further.
Ignition of the liquid KNO3-NaNO3-sugar alcohol can be finally done by an electric match or reaching the auto ignition temperature of the sugar alcohol by the heat up charge.

 
Fig. 1

Fig. 2

Fig. 3

2011-10-03

Sugar Shot Weekly Activity Report: September 26-October 2, 2011‏

Highlights of recent developments on the DoubleSShot project

The design is currently underway for a replacement static test motor. This motor, deemed DSS BPS (Boiler Plate Single-phase), will be essentially identical to the BP motor recently test fired. Except that it will be a single burn motor. This will allow us to test the design concept of the star grain, gather performance data, and to verify the behavior of the Delay Plug. The investigation into the BP anomaly has pointed to a breech of the Midbulkhead as a probably cause. Hot gases in the aft chamber pressure port channel (drilled into the Midbulkhead) likely caused a fracture of the Midbulkhead ablative liner, allowing the hot exhaust flow into the forward chamber, thereby igniting the grain (specifics of the likely cause of the anomaly will be detailed in a Test Report to be published in the future). The new motor will be fitted with the Midbulkhead at the forward end, with the Delay Plug cast into place. A "forward bulkhead" will be added to seal off the chamber forward of the Midbulkhead, fitted with a pressure sensor to detect any possible breech of the Midbulkhead seal.

Rick has completed his examination of the DSS BP motor's parts and has determined that the nozzle and Midbulkhead are in good condition and will be used for the new motor. The Midbulkhead ablative liner was found to be completely missing.View of Midbulkhead:

View of the interior wall of Midbulkhead:
 (photos courtesy Rick Maschek)

Rick has completed measurements of the circumference of the "ballooned" forward casing. It is clear that the forward casing experienced particularly high pressures (>2000 psi) which severely strained the metal. The permanent strain was significantly more than the aft casing, as is seen in the following table and graph:
Randy Dormans has kindly agreed to drill the precision located nozzle and bulkhead attachment holes (75 total)  in the motor casing. Randy reports that he has obtained a length of the 6" schedule 10 pipe for the motor casing and will start work on this task very soon. Randy had similarly procured and prepared both motor casings for the DSS BP motor.
 
Craig Peterson has kindly agreed to once again machine the custom modified cap screws for the nozzle and bulkhead attachments (75 plus spares).
 
Paul Avery has agreed to work on repairing or replacing the static test stand for the new motor. Paul has also taken on the task of developing a new, more powerful pyrogen unit for igniting the motor. 
 
Alberto has updated the documentation page of the SS2S website with the four reports written by Markus Bindhammer on eutectic sugar propellant research. 

2011-09-26

Sugar Shot Weekly Activity Report: September 19-25, 2011‏

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).

2011-09-23

Combustion behavior of liquid eutectic KNO3-NaNO3-Mannitol propellant

Experiment setup:

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:


2011-09-21

Sugar Shot Weekly Activity Report: September 12-18, 2011‏

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:
Eutectic sugar propellant research Part II
Eutectic sugar propellant research Part III

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.

2011-09-16

Eutectic KNO3-NaNO3-Mannitol‏ propellant

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. 


2011-09-14

Sugar Shot Weekly Activity Report: September 5-11, 2011‏


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.
 

2011-09-13

Eutectic KNO3-NaNO3-Sorbitol propellant

Preparation: 

  • 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)





2011-09-10

KNO3-LiNO3-Sorbitol-Eutectic propellant

Preparation:

  • 6.5g KNO3 and 3.5g LiNO3 mixed in a beaker
  • 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!) 

Hot plate with temperture sensor and thermostat:
 
Strand burn test:

KClO3-Sulfur-Epoxy composite propellant

Preparation:
  • 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 

Strand burn rate 15mm/s at STP:

Some more burn tests: