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  #31  
Old 05-25-2022, 07:41 PM
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I was kinda scratching my head too about the infrared camera view and not visible light color. Plenty of daylight for it, but for whatever reason they stayed with the infrared feed all the way down. Didn’t help hearing the NASA commentator ladies talk about the pretty red, whit and blue canopies. Oh well. Down safe...that was key I guess. But yes, still some wrinkles to iron out on those thrusters.

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  #32  
Old 05-26-2022, 06:16 AM
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Quote:
Originally Posted by Bill
Thanks for that. Twitter is the least bad of the social media companies to watch it on. At least until recently when they began to engage in the instagram fetish of popping up an airbag which cannot be dismissed.

For future viewing, this is the link to the post before it becomes difficult to find in the future:

https://twitter.com/ulalaunch/statu...084831254171652

Interesting watching the ice melt off of the booster.

I never realized that the nozzles of the RL-10 were that close together.


Bill


Yes - they are super close together. It's a tight fit coming out of the inter-stage adapter!
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  #33  
Old 05-26-2022, 11:07 AM
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Quote:
Originally Posted by Bill
I never realized that the nozzles of the RL-10 were that close together.

It makes sense though. The biggest reason to separate them more, I think, would be if they were on a first stage, there could be overheating issues. In vacuum, that is not an issue.

I even wonder if the two use a parallelogram linkage in the yaw axis to assure they stay the same distance apart.

If one engine shut down early, and "stuck" where it was, the offset thrustline would cause the good engine to yaw outwards to get the thrustline thru the CG, so no engine collision issues.

But if one shut down, I do not know if there is any roll control capability. It would need to be significant roll control too, due to fuel sloshing problems in a "tilted" tank (tilted relative to the off-center thrust vector).

In the video, shortly after ignition, you could see the two engines "scissoring" a bit to make roll corrections till it settled down.
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Last edited by georgegassaway : 05-26-2022 at 06:46 PM.
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  #34  
Old 05-26-2022, 01:55 PM
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Here is a still of the (as I call them) "Nice Pretty Chutes" that we did not get to see (well, we did not see the colors) in the live coverage of the landing yesterday due to the constant infrared video feed NASA used for the landing coverage.
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  #35  
Old 05-26-2022, 03:37 PM
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Yeah, they kept switching over to infrared. I mean, ????

I thought the coverage at the start was good, but as it deteriorated I got so ticked off I turned off the channel with 2 minutes to go to touchdown.

Grrrrr.
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  #36  
Old 05-27-2022, 08:20 AM
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OFT-2 Starliner landing (slow parts sped up)
May 25, 2022

https://www.youtube.com/watch?v=gPFS8Bp643o

On the ground:

https://newsatcl-pctr.c.yimg.jp/t/a...-000-2-view.jpg
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  #37  
Old 05-27-2022, 08:48 AM
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From the link just provided, infrared was much higher resolution than the visible wavelength footage.
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  #38  
Old 05-27-2022, 09:46 AM
frognbuff frognbuff is offline
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Quote:
Originally Posted by georgegassaway
It makes sense though. The biggest reason to separate them more, I think, would be if they were on a first stage, there could be overheating issues. In vacuum, that is not an issue.

I even wonder if the two use a parallelogram linkage in the yaw axis to assure they stay the same distance apart.

If one engine shut down early, and "stuck" where it was, the offset thrustline would cause the good engine to yaw outwards to get the thrustline thru the CG, so no engine collision issues.

But if one shut down, I do not know if there is any roll control capability. It would need to be significant roll control too, due to fuel sloshing problems in a "tilted" tank (tilted relative to the off-center thrust vector).

In the video, shortly after ignition, you could see the two engines "scissoring" a bit to make roll corrections till it settled down.


Actually, base heating remains a real concern. The engines still radiate quite a bit of heat.

The spacing was driven by the gimbal angles. Fortunately, they don't gimbal that far, and no, there is no physical linkage between the two. If they were somehow commanded to gimbal towards one another, they won't hit. The other big driver is the diameter of Centaur, which drives the diameter of the interstage. It's an incredibly tight fit. They engines simply cannot be further apart. On Centaur V, the engines ARE much further apart. This is because they have the room (partly) but also because they are then able to use larger nozzle extensions. Not the deployable extension you see on Delta IV, but a big extension is planned to get that all-important large, vacuum expansion ratio.

If one engine shut down, roll control could only be provided by RCS thrusters (as it is on every single engine Centaur mission). If this happened on a Starliner mission, I believe it would result in an abort by Starliner.

On every mission (single and dual), the engines always "wiggle" a bit at ignition. Some of that is driven by ignition transient, some is driven by the guidance system finding the "true" engine null position (zero pitch, zero yaw) versus the calculated null position. Engines are made by humans, so there are usually very minor differences.
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