Reentry Heating and Engine Bells

[TeeGee]

Hey everyone.

I was glossing over shuttle columbia disaster and noticed that the largest debris recovered was a window pane and front landing gear. What confused me was the lack of RS-25 engines. The SSME engines burn hotter than reentry during launch yet they don't melt. I know the propellant flows through the engine bell ribs before entering the injectors to COOL the rocket down, but I am a little shocked to hear that rocket engines don't survive reentry.

I guess my question is, what is the upper limit of heat tolerance that rocket engines can endure when they are NOT cooled by flowing cryogenic propellant?

Secondly, why don't the RCS thrusters melt during reentry as well? They are directly exposed to reentry heating, moreso than the 3 SSME engines, but I don't think they are destroyed on reentry.

Also, what is the upper limit of thermal protection that fuel TANKS can endure? How hot can it get before those are destroyed as well?

The reason I am asking is because I have been editing DRE values for KSP to be more realistic, basically handicapping the kerbal thermal protection system to be more like OUR thermal protection systems when we reenter at REAL LIFE speeds. I know the mod comes with a different shockwave value that directly does this, but I think altering the max temp values on the parts is more realistic.

[peadar1987]

I doubt it was the reentry heat that destroyed them, I'd say it's more likely that the spacecraft breaking up just pounded them with debris. In that sort of situation, it's more luck than anything else what gets smashed to pieces and what gets thrown clear relatively intact.

[Moar Boosters]

I think they're pretty fragile regarding physical damage. Once the lighter parts near the front of the space-craft broke apart, the engines would probably have enough momentum to plough through the rest of the spacecraft and would have been broken up.

[TeeGee]

So you think that is was destroyed via aerodynamic stress or parts of the rest of the shuttle slamming into them? How about the F1 engines on apollo, or the rest of the expeneded stages on the apollo rocket? Did those engines get destroyed as well or did they actually make it back to the ground (obviously not intact)?

[cantab]

One of the F-1 engines from Apollo 11 was recovered from the bottom of the sea. So yes those ones at least could survive landing.

http://en.wikipedia.org/wiki/F-1_%28rocket_engine%29#Locations_of_F-1_engines

[SargeRho]

Keep in mind that the engines are actively cooled while they burn. If the cooling stops, they melt rather quickly.

[kujuman]

So you think that is was destroyed via aerodynamic stress or parts of the rest of the shuttle slamming into them? How about the F1 engines on apollo, or the rest of the expeneded stages on the apollo rocket? Did those engines get destroyed as well or did they actually make it back to the ground (obviously not intact)?

Re: the F1s

http://www.bezosexpeditions.com/updates.html

[TeeGee]

Actually I was just reading that ALL the engines (except the SIVB -- slammed into the moon or put into solar orbit) made it back to earth but were destroyed on impact with the ground/ocean. I ASSUME the SSME engines had the same fate... they prob survived reentry but slammed into the ground and were destroyed.

[peadar1987]

I wouldn't think aerodynamic stresses would destroy the engines, dynamic pressures caused by moving through the air are probably going to be less than the pressures caused by the rocket exhaust when they're running. Just good old fashioned impact would be my best guess.

[TeeGee]

I wouldn't think aerodynamic stresses would destroy the engines, dynamic pressures caused by moving through the air are probably going to be less than the pressures caused by the rocket exhaust when they're running. Just good old fashioned impact would be my best guess.

Yup. I think so as well.

How about the fuel tanks on ascent stages of rockets? What is their rated thermal protection system? I know the external tank was designed to explode after the insulator foam burned away during reentry (one of the reasons fuel was LEFT in the tank at separation). This was to ensure that any pieces that made it through reentry were small.

[MajorThomas]

I wouldn't think aerodynamic stresses would destroy the engines, dynamic pressures caused by moving through the air are probably going to be less than the pressures caused by the rocket exhaust when they're running. Just good old fashioned impact would be my best guess.

Re. the F1s on S1, I think stage 1 came down nose first (big fins at the base) and in one piece, so the engines would be largely intact up to the moment of impact, at which point they probably got badly damaged, ripping free of the base, smashing through the airframe, etc.

S2 may well have broke up during re-entry as this was at a higher speed and at a higher altitude, no fins, etc. The engines may have been damaged by hypersonic flows of atmospheric air coming from various directions not encountered during functional flight. What survived breakup would have been smashed as the engines, possibly separate from the stage after break up, hit the ocean spread out over a wide area of the ocean.

I've heard the latter kind of damage as being common during the Columbia break up. The hypersonic shock waves and high compression heating ripped the "soft" orbiter to pieces during the high speed, high-altitude re-entry. There were even (morbid) reports of terrible cutting and burning damage done to the crew because of the shock waves and heat. Few (if any) of us had ever died that way before.

[Dkmdlb]

There were even (morbid) reports of terrible cutting and burning damage done to the crew because of the shock waves and heat. Few (if any) of us had ever died that way before.

Can confirm. If you go looking the information is there, but I don't recommend it.

[PlonioFludrasco]

According to that photo, the main engines survived the explosion:

[TeeGee]

According to that photo, the main engines survived the explosion:

http://blog.chron.com/sciguy/files/legacy/archives/apachecolumbiadebris.jpg

Yeah I was just looking at that. Tragic story.

[PlonioFludrasco]

Can confirm. If you go looking the information is there, but I don't recommend it.

Can you PM a link??

Thanks!