icekatze wrote:hi hi
Like I said, they upgraded the turbo pump to have a higher flow rate, something that was within the design's capabilities, though never utilized in testing. Regenerative cooling is certainly nothing new (late 1800s, early 1900s), you put tubes around the engine bell and pump propellant through it, that's hardly a revolutionary design change.
This is like saying that the Fastrak is a minor revision of the Apollo DPS. On top of that, even if you went with feature set over actual physical design (and you should almost always go with actual physical design), the current Merlins wouldn't be Fastraks (or as far as I can see, any other pintle-injector design) because none of the others had regenerative cooling. This is not a minor change, given that it means the rocket engine is not designed to engage in auto-canibalism.
If your NASA friend thinks that the Fastrak and Merlin are the same engine just because they both use a pintle injector, then they certainly don't belong in the actual launcher branch of NASA due to having a personality unsuited to the job. That kind of obsesively-invative outlook really only belongs in experimental science, not applied science, since applied is about doing things, instead of preparing for doing things.
icekatze wrote:Not to mention the fact that the Merlin gets its excellent thrust to weight ratio at the expense of specific impulse.
As long as it can achieve orbital insertion of the payload, this is perfectly reasonable. You'll never get good Isp from a chemical rocket because pure chemical rockets just can't achieve the enery / mass ratios needed, so you're better off focusing on ion engines & such as soon as you get your orbital characteristics to a state that allows them to achieve the job. I won't say that higher Isp chemical rockets are inherently bad, but if that cuts into your reusability quotient (just as an example), then you need to ditch the extra Isp, because the rockets currently cost much more than the fuel, so if you cut rocket costs by half (which a single reuse of a lower stage probably won't quite achieve) then you might get around 40% cost reductions. Fuel, meanwhile, commonly costs ~10%. Thus, reusability is more important than Isp while your reuses are few (or none), because each reuse makes more of an impact.
icekatze wrote:Space X is a fine company, and I've been trying to give them credit where it is due this entire time, but I don't think they are the second coming of space Jesus. If and when they manage to prove that they have a reliable, reusable launch system that reduces costs, then I will happily give them credit for that as well.
Funny, because it reads more like you've been trying to downplay their achievements as inconsequential. SpaceX does research, and no matter how close it formerly was to Fastrak the Merlin currently isn't one.
Now, more interestingly, does anyone know what the wording for the mission-to-Mars earmark was? NPR made me wonder if NASA is supposed to do a cycler (I really want an automated Moon base to build habitat hulls for 4+ year Mars orbiters, but there's no way that could get off the ground as fast as conventional sourcing).