Paper Study or Bending Metal?

This was an amusing exchange that I think never really got the kind of widespread attention it deserved. Please note, I have much respect for both of these gentlemen, and think they both have their own interesting approaches to hard problems. However, those approaches are clearly at opposite ends of a spectrum and heated exchanges like this one are the result of pitting them together. My favourite quote is:

              "anyone with a job could make lifestyle choices that would allow them to put a thousand dollars a month into a project of their choice"

                                                                     - John Carmack


Enjoy :)



From: Bryan Bishop
Date: Fri, March 7, 2008
Subject: An open hypersonic scramjet project

I have taken a break from synthetic biology and have turned to scramjets as an interesting way of making it into orbit. I have been working with OpenFOAM, blender, gmsh, paraview, and all sorts of other interesting programs and PDEs/Navier-Stokes (particularly the Brenner equations for hypersonic modeling) to make it all happen.

However, as a newbie, I would like to collect information on how this is all supposed to work. It is my understanding that I create the meshes, and then create files describing properties, materials, simulation circumstances, and write the program that solves the equation or at least sets up the equation to be solved. Does anybody have SRGULL or know what was so special about it? Brenner just recently came up with these equations, so Zane Pinckney must have been doing something pretty interesting back in the 1960s to have written such an accurate program. I have his email address and would like to correspond with him (he did the NASA X-43A Mach 10 research) but unfortunately emailing him out of the blue is not respectful and perhaps somebody on this list knows him and would be willing to set me up?

My plan is to use tungsten for the exhaust pipes. It's not a superalloy, but it is close enough, and at $250 USD / 1000 kg, it looks like I can afford it. The metal working can be done in my garage, just need to make a CNC machine, lathe, nothing too intense as far as I can tell. The carbon-carbon sealing is worrying me, however, does anybody have some thoughts?

Since I do not have access to a B52 or Pegasus rocket to launch any scramjet, I have been considering integrating Steve's pistonless lox engine into the scramjet to get it high enough into orbit to do free fall and accelerate to Mach 4 so that the scramjet can actually activate and take it up the rest of the way. Obtaining lox might be easy enough, or alternatively I have been discussing with John Wilke the possibility of DIY lox production (since he's considering doing it in orbit, you see).

Thoughts? Comments? Anybody willing to set up a model of the X-43 for me? I might have a buddy from the high school draw it up in AutoCAD.

There's an image archive from NASA:
http://www.dfrc.nasa.gov/Gallery/Photo/X-43A/index.html

And I have set up some notes on my wiki:
http://heybryan.org/mediawiki/index.php/Scramjet

Bryan Bishop
http://heybryan.org/


From: John Carmack
Date: Sat, March 8, 2008

<WARNING: opinionated semi-rant ahead>

All of the programs you are investigating aren't going to make a bit of difference. In fact, they will distract you from any possibility of making something work. Things look easy on a computer, but the design task there bears little resemblance to the task of making something fly. You may also be under the mistaken belief that you can just give your CAD model to a shop and have them build it for you.

About once a year someone gets the idea that an "open" project will somehow make challenging things happen, because, well, just look at open source software! There is definitely a value to open transfer of information, which is what aRocket is all about. However, there isn't going to be an OSS like explosion of people experimenting and improving things.

Even doing aerospace on the ultra-cheap route takes more money than most people are willing to spend. Not more money than most people could afford -- just about anyone with a job could make lifestyle choices that would allow them to put a thousand dollars a month into a project of their choice, which could "get you in the game" at some level. However, playing with CAD programs and simulation codes and discussing things online is so much cheaper, and it sort of feels like you are working.

You have picked a project that has no chance whatsoever of ever reaching a point of any physical results. That isn't to say that nothing could ever come of it -- a striking paper study might impress an aerospace company that is in the business of selling paper studies to the government, but it won't ever fly.

Individuals have done some good work when they have chosen appropriate goals. A couple examples:

Richard Nakka:
http://www.nakka-rocketry.net/

Robert Watzlavick:
http://watzlavick.com/robert/rocket

We could use a thousand more people like that.

If you have been successful in life, you have the resources to choose a more ambitious goal, like the lunar lander challenge teams or low end New Space companies:

Paul Breed and son:
http://unreasonablerocket.blogspot.com/

Me and the Armadillo Aerospace crew:
http://www.armadilloaerospace.com

If you have really hit it big, you can aim right for orbit like Elon Musk. Note that your chosen project is far more challenging than what any of the middle tier groups have chosen to undertake, and could be argued to be more difficult than the projects that the billionaire crowd have undertaken. Considering that none of us at any level have been nailing our objectives right on target, your chances are, well, zero.

My advice:

Learn how to work a lathe and a welder. Get certified to fly high power rockets. Find a couple more local people to spread the required skills over. Save up some money. Pick a project that looks so easy that you think you can do it in a month. What's a rocket engine? A couple tanks, a couple valves, and a drilled injector, right? If you stick with it long enough to make it work (a couple years...), you won't be thinking about scramjets any more.

A little bit of blue-sky engineering talk is amusing once in a while, but since you talked about the price of tungsten and putting CNC machine tools in your garage, I am assuming that you have some interest in actually building something. If you start down a pragmatic path, you are in the right place to get lots of information and advice to help you along.

John Carmack


And that's what I call popcorn.


QuantumG
<< back to my home page