3D printed metal rocket engine contest Update

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I’d like to share how the 3D printed metal rocket engine contest is going:

The deadline was moved back to June 30th. The objective is to design an open source 3D printed (in metal) regenerativly cooled rocket engine for use on a nanosatellite launch vehicle (1-10kg payload). 3D printing in metal is an available technology and it has been demonstrated with regenerativly cooled rocket engines before. I’m submitting the design on a second stage LOX/Propane engine with around 800 lb of thrust. (It will be a sea level version for testing.)

I don’t mean to disparage the competition but as far as designing goes our team is pretty much stomping on them. I can say that because before you even look at any calculations for the engine just from a basic configuration standpoint all the other teams are non-starters in their current form. Although some show potential and I commend their effort. For example to make an engine like this you are going to need injectors, regenerative cooling channels, and film cooling, but we are the only team with all three. Only about 4 teams even have injectors designed at all, and only one other team looks like it could work. One team has what is supposed to be a pintle, but from the looks of it they’ve never seen one before. One team has oxidizer inlets but no fuel inlets. Only 2 other teams even have regenerative cooling channels, and we are the only team so far that has film cooling. We’re also the only team so far to mention how we will deal with some of the practical aspects of even just a static test, like LOX valves, flow metering and how to get a hold of cryogenic propellants. I’m no Wernher von Braun but these guys have a lot of catching up to do.
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However this advantage does not assure us we will win for two reasons. First, the design is oddly only worth 40% of the overall evaluation the other parts are 40% collaboration and 20% business plan. So we even if our competition has lousy rockets engines they could win simply by blathering to one another more and writing a convincing business plan. The second reason, which incidentally makes the first more troubling, is that while the judges have technical backgrounds they have no rocketry background that I am aware of, so I don’t know if they would know a good rocket engine if they saw one. One judge is known for having built an IEC fusor in high school. Another is an artist, a biologist, and a “space researcher” whatever that means. The third is the guy who designed the Segway (not the later CEO of the Segway company who fell to his death when he rode off a cliff on a Segway.) Although he has some legitimate engineering background (I mean other than the Segway) he is also the co-inventor of a pneumatic swat team cannon. That’s not a cannon used by swat team members to shoot at things, it’s a cannon that shoots swat team members out of it and onto roof tops, over walls, and to any other hard to reach place that you would like to have a swat team. I don’t know if he will recognize ‘realistic’ and ‘practical’ when he sees it. Maybe I should have gone with a rocket catapult to orbit instead.

This makes our job more difficult and winning uncertain. This means that in our design notes we also need to explain and justify a lot more than if we had judges that we knew were familiar with what it takes to make a liquid propellant rocket engine. We can’t simply state how much propellant we plan use for film cooling. We also need to let them know that if you don’t use film cooling at all you can expect a destructive engine failure. That way they are less likely to overlook our competitor’s flaws.
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I’m confident about our design, and I’m sure our business plan will be good as well, but I could use some help on the collaboration part. Just some back and forth comments on the collaboration site they want us to use should go a long way. Even if you know nothing about rockets the conversation would be beneficial and it would be appreciated.

The prize for winning is 5,000 dollars plus they will print the winning engine for free. For our current configuration at the vendor they intend to use that’s about another $5000 worth of 3D printing. If we win we plan to spend the money on things we would need for a static tests of the engine like a load cell, some tanks, helium, LOX ect. I think that if we won we might be able to have it ready for static testing at the October launch. If there is money left over we’ll put it towards a launch vehicle. (I intend to develop a scalable process that we could use to make pressure vessels from scratch.)

Win or lose, I want to turn some of the worked we’ve done on this into some RRS News articles, should we reboot the RRS News. I’ve done some programming for this that there may be some interest in sharing. I’m working on a program that sizes a launch vehicle based on payload, and another one that will give the basic chamber and nozzle configuration and do a basic thermal analysis. I also hope to work on a program that will analyze the rockets ascent trajectory. If you then take those 3 programs and put it all into an optimization scheme, like the evolutionary optimization program I wrote in college for turbopump design, you would have a launch vehicle design optimizer that can be used to help find the smallest and lowest cost launch vehicle configuration that could reasonably be pulled off. Neat huh!
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-Richard Garcia

May 10th 2013 Meeting Report

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At the meeting we mostly discussed the results of April 27th launch. Regarding safety we discussed the USC launch in particular. Our the pyrotechnic operator for the launch Jim Gross mentioned that the UCS guys did better about reducing the number of people around the loading station. However he also expressed that they could still be more organized in their efforts on launch day. (For example they were speed drying epoxy with a blow dryer prior to launch) Although we are aware that this is a college project and the added constraints, particularly with time, that come along with that. He also noted that he was not made aware of the flight computers safety feature to not ignite the second stage depending on the flight trajectory and felt that this was important information for the pyrotechnic operator to be made aware of. A suggestion was made that some sort of prelaunch presentation or review of the flight software would be very beneficial.

Regarding launches in general it was expressed that we want to be more diligent about having people who are launching fill out a flight data sheets with information like max altitude and the range of the recovery area. This was apparently something we were more diligent about in the past but we have lapsed on its enforcement. I made the suggestion that if we implement this again we should also make as simple guide as possible showing how to calculate those numbers for anyone new to the process.

We also discussed the possibility of having a special meeting in September but the details aren’t set. The USC guys would like to host a meeting at their Lab on the USC campus, so they can show us all the neat stuff they have going on there and how they’ve been building their rockets. That promises to be interesting so don’t miss it.

I also had the opportunity to show everyone my tilt sensor. After seeing Osvoldo’s magnetic apogee detector and hearing about a mercury based tilt sensor for parachute deployment I decided I needed to make something like that for my rocket. It’s just a simple tilt sensor hooked up to an Arduino microcontroller. The Arduino is programmed to check that the device has been armed, and count how long the sensor has been activated. That way any jostling won’t set it off. Only when it’s held on, as when it will when the rocket reaches apogee and leans over, will the parachute be deployed. Based on feedback that I got I will run it in a test configuration first (launched on a rocket but not controlling deployment) to see how it behaves and how long if at all the deceleration phase, after burnout and before apogee, will set off the switch. Based on the results I may need to adjust the programming and have it ignore the first activation caused by deceleration, or I may have to abandon the idea entirely.

Eric Claypool showed up and he gave me a hard copy of the files of the media that are currently on the RRS website.[the previous site] We discussed what to do next with the website; the First thing to do is install WordPress on the server. Once that happens I can start working on a live version of the new site under a different address. Once we’re satisfied we then just switch the address. Eric also brought his LOX/Alcohol rocket engine for us to take a look at.

Next Meeting: June 14th Gardena Recreational Center, 1670 West 162nd Street Gardena, CA
Next Launch/Static test has been set for October 5th at the MTA

Regarding the next launch, I don’t know what anyone else is working on for it but here is what I hope to have ready. Sucrose/potassium nitrate motor static test and flight test with additional testing of an Arduino based flight computer, and a static test of my peroxide/gasoline engine. I also hope to do some testing for a hydrogen peroxide based quasi-hypergolic ignition system (where the heat from the decomposition of the peroxide ignites the propellants.) I haven’t done any detailed design yet but I’ve found a reasonable vendor for 30% peroxide and a lab glassware vacuum distilling kit on ebay, so I may be cooking up some peroxide at some point soon. If you need some let me know, but I don’t plan to make a lot.

 

-Richard Garcia

April 27th 2013 Firing report

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The launch was very well attended and we got some good video. The launched got started right after the tallest dust devil I’ve seen in person was kicking up dirt over at FAR but thankfully kept its distance from us. I didn’t feel like cleaning sand out of my camera again.

We had two beta launches and both parachute recovery systems failed. Neither of the rockets were recovered. Osvoldo’s rocket’s parachute ripped on deployment. Frank’s rocket had the instrument section separated shortly after takeoff. Larry had a static test of a class composite motor. It was buried in the ground aka “poor man’s vertical test stand” which was good since it exploded upon ignition. The nozzle was recovered and did not show signs of erosion. Chris had two sucrose/potassium nitrate motor static tests. He was testing two different configurations. The first one fired for about 13 seconds, but the nozzle was ejected part way through. One of the things he was testing was nozzle material and construction methods, it was found that that particular bonding agent being used as a nozzle was not strong enough for nozzle retention however it appeared to work satisfactorily as an ablative. The second test happened latter in the evening and I, unfortunately, was unable to film it but thankfully Frank filmed it with his phone. The second motors grain cracked and ejected some of the propellant and it finished burning on the ground.

The USC team had a large 2 stage rocket named the “Texas Two Step” painted like one of those red white and blue rocket popsicles. One of the goals of the test was to use the same launch tower they intend to use on their suborbital launch. After working on it all day and after some delays (they had missed some parts and had to send people to go and get them) they finally launch just before the sun went over the mountain. Sun down, incidentally, was the cut off for scrubbing the launch for the day, so they made it at the last minute. The 2nd stage did not ignite but was recovered from its GPS signal. The first stage was not recovered. The powered portion of the first stage flight deviated significantly from vertical and it is not clear yet whether the second stage did not ignite due to a mechanical malfunction or a safety feature that would prevent the second stage from igniting if it was too far from vertical in order to keep the rocket’s possible landing zone within a certain range. They may update us further during the next meeting. (They were not at the meeting on May 10th 2013)

My peroxide/gasoline rocket was unfortunately not ready to fire since I wound up scraping some of my parts. It should be ready by the next launch. I gave a shot at making a sucrose/potassium nitrate motor but unfortunately my boring bar broke at the last minute leaving the nozzle with a .050″ or so step in it. I’ve got some replacement boring bars (although I’ll need to make a special mount for my lathe) and the motor should be ready for the next launch.

Dave Crisalli was at the launch and I had the opportunity to talk with him. He agreed to let me scan the RRS newsletters that he has. So now I just need to get a hold of them to do the actual scanning. (A a note on building up a digital library: I finally got an alumni membership at my college, so now I can check out books from the library again. So anything they have I can get a scan of. They also happen to have a lot of the journals from the American Rocket Society which later merged with the Institute of the Aerospace Sciences to become the AIAA (American Institute of Aeronautics and Astronautics). I browsed a volume they had one day. It had a neat article on the ground handling hardware for the Viking missile. I hope to digitize those too some day.) He also mentioned having some intention to use some of the old logs of wood out there to set aside some space for parking and camping. Sounds like a good thing to have a work party for. I don’t know about you, but dragging around logs of wood out in the middle of desert sounds like good fun to me. I don’t know what kind of time line he was thinking of but I’d be glad to help.

Particularly interesting at the launch was the presence of a National Geographic film crew. They were filming for a new show called “Meltdown” which will be a new show on precious metals. How that premise got them at the MTA goes something like this. Some rocket engines are made from precious metals i.e. copper. It’s used because of its high thermal conductivity on regenerativly cooled rocket engines. For example, the Space Shuttle and Falcon9 engines both use a pretty big chunk of copper. I suspect that someone somewhere has made an engine using silver in place of copper since it has even better thermal conductivity than copper but I know of no particular examples. Apparently they couldn’t find anyone with an engine made with copper who would do the show, so they came out to film the RRS instead. If I had known about this far enough in advance I might have been able to make one just for the show since I basically have blue prints for one. I would have been happy to at least give it a try anyway. (for those interested, this I what I was referring to: http://www.cientificosaficionados.com/libros/cohetes.pdf if anyone wants to give it a try I’d be glad to help if I can) I have no idea what kind of tone show will have or how much time will be spent on the RRS nor do I know when exactly the show will air (possibly in the summer sometime) nor with what certainty it will be aired at all. I know what some of you may be thinking: considering how often the media treats anyone doing anything interesting with science or engineering as dangerous goofballs and not gentlemen heroes like Jules Verne might have them portrayed, there is always a concern when dealing with the media about what light we may be portrayed in. But Frank was on top of that and he was working with them and they had an agreement to keep everything positive and professional, which I think will be the case. At the May 10th meeting Frank gave some examples of the good working relationship we had with them and making sure we’re ok with the way we’ll be shown. Even if the coverage isn’t perfectly what we want I still think the publicity will probably be a good thing.

 

Over all I think the launch went really well, and I can’t wait till the next one.

 

-Richard Garcia