Monthly Archives: September 2014

OpenFoam vs Fluent

So I am taking a look today at the various CFD options. I’ve looked around to see who is using what software. Basically it would seem to me the people doing real engineering and actually building things are using a variety of solutions. Some of which I have never heard of. I just assumed everyone was using ANSYS but it would seem not.

Copenhagen Suborbital – Solid Works / Open Foam

XCOR Aerospace – http://www.metacomptech.com/

Space X – Ansys

JPL – Whole bunch of things including ANSYS.

Also it would seem my ideas about hypersonic combined flow system. Precooling. Non direct coupled impellers. Piston pumps. Pretty much all of it is right on the bleeding edge where I should be. Rather satisfying to contemplate these ideas and to then realize this work is actually being done.

Also taking a good look at the X15 engine.

X15 Engine

Thoughts on the F-1 vs the F1B

Some general observations about the new F1B engine vs the Apollo era F-1 engine.

1. Ditching the Turbo pump after flow injection makes for a simpler engine but it also shows to much academia not enough intuition. Those Apollo guys made a big deal of turbo pump through flow injection to the primary chamber for a reason. Anybody who has ever built anything fast can tell you why.

2. Ditching the radial tube arrangement due to manufacturing complexity assumes you were going to manufacture a radially arrayed tube structure the same way the Apollo engineers did. This does not have to be the case. It is a brilliant design that gets the maximum flow for the minimum mass. Do the simple math for the tube area vs a double chamber layer design + supporting internal baffles. It is good to note the Redstone engines and the V2 were all part of a long history of double wall design. They abandoned it for a REASON. I can think of at least 3 different ways to manufacture that original Apollo chamber design that are economical and low in manual assembly / labor.

3. Your still building your grand parents rocket engine. While I understand that aerospace is typically conservative WTF for. We are so far beyond this standard rocket combination and we need to move on. The next generation of engines will clearly be hybrid rocket jet compounds with some ambient air breathing facility and this engine isn’t it …..

4. After a bit of study it is really quite exciting to realize that you don’t need to be either JPL or a large research institute to build a decent engine any more. All you need is to be half competent prepared to acknowledge the reality of risk and to push the boundaries.

Thrust Chambers And All That

engine_tube

This is my second pass at a thrust chamber. By building it from tubes like the F-1 series engines I was greatly able to reduce the 3D printing costs. Also I halved the size. Few issues to resolve with hole sizes that are to small for the SLS process to handle. Also I not sure how the final exit portion of the engine bell will be joined and it has no supporting bracket points on the top mount. I think for trial runs it will just flow direct from an oxygen bottle and kerosene driven by a standard high flow fuel pump …

Sabre Cycle

Sabre_Prop

General sketches suggesting how to contemplate the Sabre cycle principle. Basically this is all about Turbo Pumps and Compressors. How do you combine a high flow rocket engine with a low flow ambient compressor. You can start to contemplate complete cast blocks with the rocket chamber portion at one end. Will be drawing one of these in the entirety shortly. Least anyone thinks I just wanted to copy some tired old F-1 design. We are well beyond that now but …. physically have to begin somewhere ….

Really all the problems … are production problems … should completely not at all think about these problems like our grand parents .. this complex … . multi component carrying .. .bolted together .. masterfully welded … kaboodle .. .. So the F1B is down to less than 200 parts .. or so they claim ….

It is still a motor from the 60’s …

Turbo Pump

This is an Apollo Turbopump impeller. It is about 2 feet long from end to end and weighs a lot. This is a very, very, very precise piece of equipment. Either from F1 or J-2 engines, but it is impressive, regardless. The partial paperwork that came with this explains that it is as perfectly balanced as was humanly possible back in the 1960’s. Remember, this was before CNC milling, when metal things like this had to be jigged and run by hand. Precision was really, unbelievably hard back then, and yet they made this. Actually, many of these. Impellers for pumping LOX or Kerosene or Liquid hydrogen, which was capable of spinning at 28,000 (Yes, twenty-eight THOUSAND) RPM. This is the finest example of precision engineering and milling I have ever seen.

turbopump

These are some pictures of the original Redstone engine.

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Thrust Chambers

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naa-75-110

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Been studying the A-6 / A-7 Redstone engines. Recalled that Motat has one stripped down on display. Can clearly see the quality of the welds.

Thinking a lot about 3D printers and SLS technology in general. Have so many ideas right now about how this technology should evolve. Hard to write them all down clearly.

Here is a quick picture of the Redstone chamber I have Modeled in Solidworks. Sadly to 3D print it is still going to cost about 1200 dollars.

Chamber

To get ahead with all these projects really need to solve the 3D printing problem in a proper easy non Academia cheap kind of way.