zeke01 - 12/11/2007 7:20 AMGreat! Now can someone explain those ghostly blue 'diamonds' in the J2 and SSME exhausts? Thanks!
zeke01 - 12/11/2007 4:09 PMSo the blue color is from the excess hydrogen being burnt in the exhaust flow, which fits with the hydrogen emission spectrum above.Exceeelent. My mind is at ease once more.Thanks.
Citabria - 15/11/2007 12:31 PMThat's right. The gas generator exhaust is much cooler (and fuel-rich) than mainstage exhaust and so it is routed through those large tapered ducts you see surrounding the F-1 nozzle where it exits and cools the inside of the nozzle extension. The effect is even more apparent in films of Saturn 1 launches, because the outer 4 H-1 engines have those ducts and the inner 4 do not. You can see the darker exhaust from the outer engines but the inner engines show less or none of the darker band.BTW, the Titan II hypergolic exhaust did not glow as much as RP-1, so the Mach diamonds were more visible.
Jim - 15/11/2007 2:28 PMQuoteCitabria - 15/11/2007 12:31 PMThat's right. The gas generator exhaust is much cooler (and fuel-rich) than mainstage exhaust and so it is routed through those large tapered ducts you see surrounding the F-1 nozzle where it exits and cools the inside of the nozzle extension. The effect is even more apparent in films of Saturn 1 launches, because the outer 4 H-1 engines have those ducts and the inner 4 do not. You can see the darker exhaust from the outer engines but the inner engines show less or none of the darker band.BTW, the Titan II hypergolic exhaust did not glow as much as RP-1, so the Mach diamonds were more visible.The gas generator exhaust gas becomes bright when it mixes with enough O2 to ignite
the outer 4 H-1 engines have those ducts and the inner 4 do not. You can see the darker exhaust from the outer engines but the inner engines show less or none of the darker band.
For the four fixed center engines, the fuel-rich exhaust gases were piped to the edge of the booster skirt and dumped overboard into a region of high-velocity air flow. In the later vehicles, the exhaust gases were dumped exactly into the “anterstar” created by the four fixed engines. The gimbaled outboard engines required a different approach. The turbopump was fixed to the gimbaled engines; therefore, an overboard duct for them would have required a flexible coupling that could withstand the high temperature of the turbine exhaust gases. Instead, MSFC devised outboard engine attachments called aspirators, which forced the turbine exhaust into hoods on the stub fins as shown in figure 12.
Quote from: Citabria on 11/15/2007 04:31 pmthe outer 4 H-1 engines have those ducts and the inner 4 do not. You can see the darker exhaust from the outer engines but the inner engines show less or none of the darker band.Does anyone have any reference about this ? I'd like to know more about these tapered duct difference between the central and the outer H-1 engines, but the only source I have found so far on internet is... this post by Citabria. In addition, I would have thought the central engines had more thermal constraints and needed more this cooling system than the outer engines.A good source of information dealing with exhaust gases for the Saturn I/IB that I have found so far is this one: https://fr.scribd.com/document/47291629/Review-of-Our-National-Heritage-of-Launch-Vehicles-Using-Aerodynamic-Surfaces-and-Current-Use-of-These-by-Other-Nations , page 21 of the PDF, noted page 15 on screen. One can read:QuoteFor the four fixed center engines, the fuel-rich exhaust gases were piped to the edge of the booster skirt and dumped overboard into a region of high-velocity air flow. In the later vehicles, the exhaust gases were dumped exactly into the “anterstar” created by the four fixed engines. The gimbaled outboard engines required a different approach. The turbopump was fixed to the gimbaled engines; therefore, an overboard duct for them would have required a flexible coupling that could withstand the high temperature of the turbine exhaust gases. Instead, MSFC devised outboard engine attachments called aspirators, which forced the turbine exhaust into hoods on the stub fins as shown in figure 12.But I see no mention that for the 4 central engines, part of the exhaust was reinjected inside the nozzle.
Thanks for the link, so Citabria was wrong, and for the outboard engines the exhaust was reinjected into the chamber.
Copper?