Raptor - 2 interesting thoughts

[fl1034]

I just saw this (pic 1 and 2 below), someone did a pretty good labeling of Raptor's various component just from a concept 3d model. And whoever did the labeling seemed unable to find where the gimbal is. Well, I think Elon Musk might have adopted a similar structure as the Russians did on their RD-170 (pic 3, 4, 5 and 6). This is an external gimbal, unlike the ball-face gimbal that's used on the SSME (pic 7), because this one has a large flexible duct going through it. The Raptor's fuel/oxidizer interface looks really a lot like the F-1's (pic 8 ), a flat plate, and I think the Raptor's LOX inlet also goes through a similar external gimbal.

Which also makes me think the 3d model in pic 2 is all there is to the Raptor, and there is no "remote booster pump" as suggested in the label. Well, then where is the booster pump? I think I got that figured out as well. The answer is you can copy what's been used in another Russian engine, RD-0120, the LH2/LOX one that powered the core stage of the Energia rocket (pic 9). The LOX booster pump on this thing has a fancy coaxial 2-shaft design (pic 10 and 11), the crux is basically if two stages can rotate at different speeds, the second pr HP stage can rotate much higher than the first or LP stage, thereby making what would otherwise be a very large single shaft pump much lighter and smaller. I think that's what Elon did with his Raptor, by having both coaxial 2-shaft main LOX and LCH4 pumps, he can do away with a booster stage and just let the LP stage rotate at say 5,000 rpm and the HP stage at 30,000 rpm. This configuration can boost the pressure well past 400 bar at the HP discharge, and don't forget FFSC design doesn't really need much of sealing at all. With all these weight saving, we will very likely see a T/W ratio north of 100.

(The last pic is an engineering cross-section drawing of the (external gimbal + warm oxidizer rich preburner discharge manifold flexible joint) combo.)

[rakaydos]

I just saw this (pic 1 and 2 below), someone did a pretty good labeling of Raptor's various component just from a concept 3d model. And whoever did the labeling seemed unable to find where the gimbal is.

Second picture, far right, "Actuator Hydraulics."

[speedevil]

I just saw this (pic 1 and 2 below), someone did a pretty good labeling of Raptor's various component just from a concept 3d model. And whoever did the labeling seemed unable to find where the gimbal is.

Second picture, far right, "Actuator Hydraulics."

And the vague line pointed to the back of the engine with 'gimbal here' , obscured by it there will be a duplicate of this, of course.

[livingjw]

- There was no engine gimbal on the CAD picture. I was indicating where it would go. We have now seen the gimbal on the actual engine.

- I suspect that the Raptor LOX and CH4 pumps are similar to the Vulcan pumps. The Raptor LOX pump might need an axial stage just aft of the inducer similar to the Vulcan's hydrogen pump.

John

[fl1034]

- There was no engine gimbal on the CAD picture. I was indicating where it would go. We have now seen the gimbal on the actual engine.

- I suspect that the Raptor LOX and CH4 pumps are similar to the Vulcan pumps. The Raptor LOX pump might need an axial stage just aft to the inducer similar to the Vulcan's hydrogen pump.

John

So... I still guesstimated the first one right

[fl1034]

- There was no engine gimbal on the CAD picture. I was indicating where it would go. We have now seen the gimbal on the actual engine.

- I suspect that the Raptor LOX and CH4 pumps are similar to the Vulcan pumps. The Raptor LOX pump might need an axial stage just aft to the inducer similar to the Vulcan's hydrogen pump.

John

The pump you showed seemed to be going as fast as it could for the inducer and first stage but still slow for the last two centrifugal stages.