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Just now, Minmus Taster said:

Anyone notice weird plumes that looked almost like they were coming out of the rockets sides? it's probably just me but I can't help but wonder if it was an actual issue.

Where?

Not the visible exhaust moving up into the low pressure area at the bottom of the rocket, right? That's entirely normal.

Spoiler

Apollo_11_Saturn_V_in_flight_pillars.jpg

 

 

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8 minutes ago, Minmus Taster said:

Anyone notice weird plumes that looked almost like they were coming out of the rockets sides? it's probably just me but I can't help but wonder if it was an actual issue.

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s4wipSL.png

 

The engine exhaust climbs up the side under the landing legs because the pressure is low there. It's just a quirk of fast-moving air.

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7 hours ago, tater said:

Where?

Not the visible exhaust moving up into the low pressure area at the bottom of the rocket, right? That's entirely normal.

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Apollo_11_Saturn_V_in_flight_pillars.jpg

 

 

Is that some kind of 'drag' feature?  The low pressure area drawing exhaust upwards is new to me

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7 hours ago, JoeSchmuckatelli said:

Is that some kind of 'drag' feature?  The low pressure area drawing exhaust upwards is new to me

You always get a low pressure region on the back of a vehicle moving through the air that is not tapered perfectly (wings try to avoid this for example). Like the flat back of a car. As the rocket exhaust pressure equals, then exceeds the ambient air pressure as the vehicle climbs into lower pressure regions, we see the plume expand perpendicular to the rocket.

Quick google search:

4-Figure4-1.png

Since the bottom is at lower pressure, and inside the boundary flow, the flow in the lee is turbulent as well (like the leaves/junk at the front of a pickup truck bed flying around but staying in the bed near the back of the cab), some of the flame gets sucked in among the engines.

If you look at the bell shown at the right at high altitude, the plume boundary ends up exceeding the diameter of the vehicle as we see in launches. Multiple vehicle diameters higher up. The flow boundary layer along the vehicle as it moves through the air is roughly along the body, but the plume boundary forms a bow shock that connects to the rocket body at the engines, and the boundary layer of flow along the vehicle as a whole ends up going along the bow shock, you end up with plume-induced flow separation.

Best quick google image I could find:

Plume-Induced-Flow-Separation-PIFS.png

 

The areas of re circulation shown above near the back pull flame along the side of the vehicle. The one we see so markedly on Saturn V is the "BL Separation Shock" BL is "boundary layer."

Another cool pic of Saturn V plume induced flow separation :

Spoiler

wBO5F.jpg

Look how sooty stage 1 gets. Not sure which way is actually up in this pic, might be flipped, but angle of attack makes it slightly asymmetrical.

 

Edited by tater
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1 hour ago, tater said:

The one we see so markedly on Saturn V is the "BL Separation Shock" BL is "boundary layer

That is some crazy squash!   Thanks for sharing 

 

(I knew about drag with cars, and I knew from KSP about drag on rockets... What I never anticipated was that hot gas could 'climb up' the rocket) 

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Elon was on some podcast called Full Send. Host(s) are... not what I would wish, lol. Listened a little in the car, one interesting tidbit. They asked him what Starship cost, and he said the marginal cost of a launch right now was $50M-$100M, so every BOOM they are likely to have in coming months will be expensive.

 

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51 minutes ago, tater said:

Elon was on some podcast called Full Send. Host(s) are... not what I would wish, lol. Listened a little in the car, one interesting tidbit. They asked him what Starship cost, and he said the marginal cost of a launch right now was $50M-$100M, so every BOOM they are likely to have in coming months will be expensive.

 

Honestly, that's kind of what I figured. That they would want to keep it around the same cost of a Falcon 9/Heavy to immediately start incentivizing customers moving to Starship instead. But below that, like  a few tens of millions lower than a Falcon 9 wouldn't be good for recouping some of their costs as it moves from a developmental to an operational vehicle (if those kinds of costs are even potentially feasible for them in the near future). Did they talk about the cost of Raptor?

Edited by Spaceception
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On 8/1/2022 at 9:37 PM, Beccab said:

 

Weird info, the fence angles inward to stop alligators climbing the fence as they do with straight ones. 
Leaned this at an guided tour at KSC some years ago, lots of alligators there saw one in an pound outside pad 39 B and its rules that you have to drive cars, you can not jog or bike. 
On the other hand you get some very scary security guards for free. 

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9 minutes ago, magnemoe said:

Weird info, the fence angles inward to stop alligators climbing the fence as they do with straight ones. 
Leaned this at an guided tour at KSC some years ago, lots of alligators there saw one in an pound outside pad 39 B and its rules that you have to drive cars, you can not jog or bike. 
On the other hand you get some very scary security guards for free. 

Saw those on a tour a few years ago.  Flame trenches look like an alligator ossuary. 

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7 minutes ago, tater said:

No, this was just cost of blowing up Starship/Super Heavy

Explains the desire to try to catch SH on the first launch. Maybe they’ll think about trying to land SS on Kwaj too…

That said, cheaper to sacrifice the booster than to lose the booster and GSE too…

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