Reentry techniques

[Linguofreak]

Erm... I must have confused it with something else. It would indeed make more sense for me to mean aluminum.



Actually that guy grabbed the tile by the side opposing to the one that was heated up, and that's why he didn't get his hand burned. Because, as I said, the tiles transmit the heat inside themselves very slowly - it takes less time for heat to radiate away than it takes it to reach the other side of the tile.

And no, if you're holding something in your hands, heat isn't transferred by just radiation. At that point most of the heat is transferred by conduction - basically tile's atoms, "vibrating" at higher "frequencies", start banging the atoms of your hand until they start to "vibrate" (heat up) as well.

You're right about conduction being the primary method of heat flow in this case, but the TPS tiles don't tranfer heat to other objects well, even by conduction. It is possible to hold even the hot part of a tile without burning yourself.

 

[Urwumpe]

You're right about conduction being the primary method of heat flow in this case, but the TPS tiles don't tranfer heat to other objects well, even by conduction. It is possible to hold even the hot part of a tile without burning yourself.

Now, that is a hot myth. Actually, the Shuttle has bags with special protection fabrics on-board, so astronauts can escape over the overhead windows without getting burning.

 

[V8Li]

I've just seen a TV rep on Columbia and it turns out the Shuttle heats up to 3000 deg C, not 1500 deg which was my first claim. Also, it broke apart at mach 19 (or 16?) at a hight altitude. Now, the internal structure was damaged from the heat so maybe it was not at that point when it decelerates at 10m/s^2. Do you guys know if the 10m/s^2 is the maximum deceleration and when exactly occurs in flight (speed and altitude)?

 

[Urwumpe]

The shuttle does not heat to 3000 deg C. That is TV nonsense.

Read the CAIB report, if you want accurate data about the heating, it explains it far better.

The Shuttle usually attempts to fly at constant 10 m/s² (32 fps²) during nominal reentry to bleed off energy. This takes place for a much longer time.

The maximum acceleration during hot reentry is usually at 15 m/s², but I can't tell you accurately when it happens. The maximum Gs in general take place during the final approach to the runway, and can be up to 2 Gs (19 m/s²).

 

[V8Li]

The shuttle does not heat to 3000 deg C. That is TV nonsense.

You're probably right, I never herd of that value before... I guess you can't trust anyone these days

The maximum Gs in general take place during the final approach to the runway, and can be up to 2 Gs (19 m/s²).

AFAIK that's during the final alignment with the runway, while turning, not when decelerating.

 

[Woo482]

can't tell you accurately when it happens. The maximum Gs in general take place during the final approach to the runway, and can be up to 2 Gs (19 m/s²).

2Gs ? thats it its not alot is it ?

 

[Linguofreak]

Now, that is a hot myth. Actually, the Shuttle has bags with special protection fabrics on-board, so astronauts can escape over the overhead windows without getting burning.

From: http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts_sys.html#sts-hrsi

"For example, an HRSI tile taken from a 2,300 F oven can be immersed in cold water without damage. Surface heat dissipates so quickly that an uncoated tile can be held by its edges with an ungloved hand seconds after removal from the oven while its interior still glows red."

OK, so it's just dissapation of surface heat. In other words, there is no "hot side" of the tile for more than a few seconds after your heat source is removed.

 

[ijuin]

I think he might have heard three thousand degrees Fahrenheit, and mistaken it for Celsius.

 

[Urwumpe]

2Gs ? thats it its not alot is it ?

Yes. There is also an abort with 3.5 G deceleration (Gander Hi-Energy TAL), which is above the design limit of 3.0G. The Shuttle will not break because of the forces, but it will age faster as usual.