Engine testing | Hybrid engine discussion | Forum

This is coming from the comment on reddit seen here. I think it's best to continue this discussion in this forum.

There are some major question I would like answered with this testing:

1) One is that I want to verify CFD simulations to real world simulations. This will be a huge help for the actual rocket.

2) Another thing I want to test is how well phenolic insulation works. Are you capable of getting this? I really don't know much about it, other than that other rockets have been using it to prevent melting.

3) One more thing that I think would be excellent to test is the idea of having 6061 T6 Aluminium combustion chamber with some sort of plastic aeroshell. You can see the assembly in this picture.

I have used a small test stand for small rockets in University. I think we can apply the same ideas for this larger stand to measure thrust. I'll look through my old material to determine how it was done.

When I say phenolics, I really don't know much about it. I have only read that other rockets have been using them. I don't even know how it's applied. I've been trying to read more about them, though. The only information I am able to find, really, is that some of the insulations can resist about 200C of heat.

Can you explain more of what you know? How is it applied? How much do they cost? Are we capable of applying it to the inside of the combustion chamber and nozzle?

biollante said:

I think we need to form a check list of required projects and drawings that need to be created in order to start testing.  Coinciding with this, we need to have a materials list so that we can begin to seek out material donation and acquisition.  I'm positive there are people in this project that have access to or can donate materials and construction time to this endeavor, we just need to reach out to them.

It would be nice to create the test rig in CAD. I'll start to work on this when I can. I am not exactly sure how it would be, so this will be a good community effort. Once we have the test stand modeled up, we will of course then have a bill of material. We'll then know what's needed and where it goes.

Also, when you say checklist, do you mean something like this? 

On the topic of the checklist, I am fairly confident we have decided that for the combustion chamber and for the oxidizer tank that we will use 6061 T6 Aluminium. Luke, can you verify? Also, could you add the green check mark to to the list for these items?

in another thread, I discussed some of the issues that belong in this one. The most interesting thing to come out of it is that aluminum tube and HDPE cylenders are readilly avaliable in pretty much exactly the size we might want for a static testig rocket.

Regaurding the mass model calculations that are being refferenced here and elsewhere: Where did the chamber pressure figure come from?

Another thing: does anyone have any questions pertaining to rocket or test stand design that they want me to ask the Project Meteor guys when I next get a chance? I suspect their experience may be valuable, since they have done all of this before.

As I write this, I am in front of Project Meteor's main room. No one is available at present, but there are a whole bunch of the fancy posters that tend to adorn university walls presenting the results of research projects. Here's what I have learned:

Project Meteor uses N2O and HTPB plastic. One iteration of their design uses a steel combustion chamber with 1/2 " wall thickness, a titanium injector plate and a graphite nozzle, post-combustion and pre-combustion chamber. The oxidizer tank is a composite.

The fuel grain is 4.98 inches in diameter with a 1 inch circular port. The chamber has an inner diameter of 5 inches. They have tried both 9 inch and 18 inch combustion chambers. Regression rate is consistently around .037 to .025 in / s. lsp in the neighborhood of 200 to 300 seconds. Mass flow was around .16 kg/s. The nozzle and injector were designed using CFD. The nozzle was designed with a .22 kg/s mass flow and 441.36 psi chamber pressure in mind.

Three distinct test stands seem to have been used. There are nice CAD models for the more recent of the two. The posters don't go  into to much detail, but they apear to have just used strain gauges. It is worth noting that one of the test stands is vertical.

There is even more information here, but I have other obligations to attend to at the moment. I'll try to get in touch with a project member or faculty adviser to ask more questions at the first opportunity. I hope this helps.

brmj said:

There is even more information here, but I have other obligations to attend to at the moment. I'll try to get in touch with a project member or faculty adviser to ask more questions at the first opportunity. I hope this helps.

This was really good information. Thank you. I wonder why they went with a steel combustion chamber. According to what I have seen, using 6061 T6 aluminium would be about 1/4th the weight of steel. Perhaps this is something you could ask if/when you see them. It also appears that they went with a larger safety factor than I thought of (I chose 2). 

A composite oxidizer tank is also quite interesting. Was it some sort of fibers with epoxy? This is something we can keep in mind, although, I think it goes against our principles, since we would prefer to keep things as simple as possible.

Thanks for looking into this.

Post edited 2:18 pm – October 20, 2010 by biollante

I was thinking more along the lines of having the engine itself move and use rollers as guides, and use a load cell as the measuring device.

http://www.aeroconsystems.com/…..s_pics.htm

Check this out for examples of what I'm talking about, I'll be on a later tonight so hopefully we can get a discussion going.

Edit – link

I do have some experience with load cells, they're pretty straight forward.  The load cells that I have only go up to 34 pounds and they're off of scales. Load cells on ebay and other places are reasonably priced depending on the load range that were in need of, we could always salvage one out of an electronic scale of some kind, but that could have its drawbacks.  This is where a bill of materials may come in handy so we can search for donations of equipment, some one has got to have a handfull of load cells sitting in a basement.

As for the oxidizer tank, we could place it with an elbow and hosing from the tank to the combustion chamber and have the load cell sitting against the elbow.

Also, how many pounds thrust are we talking for the first test engine, this is going to determine the load cell needed.

Here's an idea of what my university's Thrust Stand looked like http://my.fit.edu/~dkirk/Thrus…..index.html if you want to see good design.

They spent a few years developing it. (keep in mind the load cells they are using are in the 10's of thousands of dollars each…)

An IRC chat tommorow at 1pm EST works for me, we should all do some research before hand and develop an idea of where they feel the process should head towards.