Carmack's Throatless Rocket Engine

Baldrson writes "John Carmack is working a potentially disruptive technology: A throatless rocket engine. Its made from plain aluminum pipes with few machined fittings. Carmack says: "The great thing about these engines is that it only takes me two nights to machine the parts, so we can test two engines a week if necessary." It scales too: "If this line of tube engine development works out, we can make a 5,000 lbf engine with very little more effort than the test engine." This is what makes disruptive technology development work: Cheap, fast turnaround on on redesign producing technologies that scale. If this works, the NASCAR guys may really start entering space competitions like the X-Cup."

Comments

Re:Obscure unit

[Cecil]

lbf is "pounds of force", not pound-feet, which would be typically be shown as lb-ft or lb*ft.

And yes, we are that backwards and stubborn. Jet and rocket engines are usually measured in pounds of thrust, not in newtons. Although they are the same class of unit (measures of force).

Ok, I read the article thanks to Rhoon's posting

[johnny cashed]

And I think he needs to hire a good machinist. And get some CNC equipment. It sounds as though Carmack is a rank amateur when in comes to machining and fabrication. Here is a choice quote:

"I used to have issues with wandering drill bits during injector drilling, but now I am spotting everything with a larger diameter carbide spotting drill, and manually applying cutting fluid to every hole as the mill runs. The 1/32" holes in the last engine came out perfectly straight."

As a kid using my father's drill press, I know all about walking (or wandering as he says) drill bits. 1/32" is a very small hole. As a machinist, I can say to him "duh". Anyone who has done any precision machining would know this (and I do have experiece in this area). But is sounds as though Carmack is reinventing the wheel over and over again.