Tilted Forum Project Discussion Community  

Go Back   Tilted Forum Project Discussion Community > The Academy > Tilted Knowledge and How-To


 
 
LinkBack Thread Tools
Old 03-04-2011, 10:35 AM   #1 (permalink)
Banned
 
Zeraph's Avatar
 
Location: The Cosmos
At what point does air moving fast enough cause things to combust?

Like a meteor hitting the atmosphere? Several thousand miles per hour or so? It'd work in reverse too right? If we somehow had a jet engine that could make a stream of air fast enough it could melt rock, right?
Zeraph is offline  
Old 03-04-2011, 01:52 PM   #2 (permalink)
Invisible
 
yournamehere's Avatar
 
Location: tentative, at best
I don't know at exactly what speed range most things are combustible - it would vary greatly depending on air density and the heat-dissipating characteristics of your object. I know the SR-71 Blackbird required the leading edges of its surfaces to be made of titanium - everything else melted. Its cruising speed is +/- 2,100 MPH. So the melting "speed" of most rocks would be somewhere south of that.

But your wind generator already exists. The LENS-X wind tunnel operated by Cal-span University at Buffalo Research Center can generate wind speeds up to 25,000 MPH - that's about 8,000 MPH faster than the Space Shuttle's re-entry speed.
__________________
If you want to avoid 95% of internet spelling errors:
"If your ridiculous pants are too loose, you're definitely going to lose them. Tell your two loser friends over there that they're going to lose theirs, too."
It won't hurt your fashion sense, either.

Last edited by yournamehere; 03-04-2011 at 02:06 PM..
yournamehere is offline  
Old 03-04-2011, 02:12 PM   #3 (permalink)
Banned
 
Zeraph's Avatar
 
Location: The Cosmos
Quote:
Originally Posted by yournamehere View Post

But your wind generator already exists. The LENS-X wind tunnel operated by Cal-span University at Buffalo Research Center can generate wind speeds up to 25,000 MPH - that's about 8,000 MPH faster than the Space Shuttle's re-entry speed.
WOW

If it was moving that fast wouldn't basically be a giant flame?

Last edited by Zeraph; 03-04-2011 at 02:15 PM..
Zeraph is offline  
Old 03-04-2011, 04:02 PM   #4 (permalink)
Junkie
 
Hektore's Avatar
 
Location: Greater Harrisburg Area
What generates the heat is not the speed of the air, but the friction of the air moving against an object. Same principle as rubbing your hands together, only with air. So as long as the walls of the wind tunnel whatever happens to be in it are sufficiently low in friction then, no it won't generate a fireball.

As far as your original question though, yes you could melt a rock with air if you got the air moving fast enough and the rock was rough enough.
__________________
The advantage law is the best law in rugby, because it lets you ignore all the others for the good of the game.
Hektore is offline  
Old 03-04-2011, 04:08 PM   #5 (permalink)
Invisible
 
yournamehere's Avatar
 
Location: tentative, at best
Here's a little info on how it works, from discovery.com (from Jan 2008):
Code:
While the Space Shuttle might be up for the highest bidder, engineers at NASA are
working hard on the next generation manned spacecraft, the Orion.
Part of that work involves testing scaled down models in the world's largest wind tunnel in Buffalo, N.Y.,
which was recently upgraded to achieve air speeds up
to Mach 30, or about 30 times the speed of sound.

"We just got it up and running and started its research life," said
Michael Holden, vice president of hypersonics at Cubrc. "The original wind tunnel was developed by NASA, 
but we have built it much bigger and can get
much more information with our new tunnel."

It takes a "one-two punch," as Holden puts it, to create wind speeds
of 30,000 miles an hour in the 100-foot-plus long, eight-foot wide tunnel.

First, helium or hydrogen gas is compressed to 3,000 pounds per square inch (psi)
and 1,000 degrees Fahrenheit, which breaks a seal. The shock wave created by
the influx of hot gas raises the the pressure inside a second chamber to over
20,000 psi, which breaks a second diaphragm, and releases the compressed air
into the expansion chamber, where it flows over the model craft in the chamber.

The wind tunnel doesn't operate for long. At its most powerful state, the tunnel "blows wind,"
 as Holden says, for only two milliseconds. It's not much time,
but its enough to simulate 60 feet of airflow. Any longer and the facility would literally melt down; those speeds
create temperatures hotter than the sun. . . 
__________________
If you want to avoid 95% of internet spelling errors:
"If your ridiculous pants are too loose, you're definitely going to lose them. Tell your two loser friends over there that they're going to lose theirs, too."
It won't hurt your fashion sense, either.
yournamehere is offline  
Old 03-04-2011, 04:21 PM   #6 (permalink)
Sober
 
GreyWolf's Avatar
 
Location: Eastern Canada
Quote:
Originally Posted by Hektore View Post
What generates the heat is not the speed of the air, but the friction of the air moving against an object. Same principle as rubbing your hands together, only with air. So as long as the walls of the wind tunnel whatever happens to be in it are sufficiently low in friction then, no it won't generate a fireball.

As far as your original question though, yes you could melt a rock with air if you got the air moving fast enough and the rock was rough enough.
Moving air (i.e. wind) can actually heat itself through the friction of the air molecules themselves. However, not everything will combust (in general on earth , oxidise). At the speeds generated by the Lens-X wind tunnel, the air itself will become hot enough to ionise relatively quickly, resulting in a plasma. This does not happen within the air tunnel itself (I believe) due to the short bursts of the actual wind blasts. On the other hand, there is a plasma created around objects entering the earth's atmosphere (such as meteors and space shuttles). This is part of what causes the "radio blackou" on re-entry.

As well, as mentioned above, the SR-71 flew so fast that it would expand by about 12" - 18" just from the friction of the air. As a result, they never came up with any seals that could totally contain the fuel within the plane. Fueled in a hangar, they would have to put pans under it to catch the dripping fuel. Once in the air, they would fly at speed until the expansion compressed the seal sufficiently to block the leakage, then re-fuel in air, then fly the missions.
__________________
The secret to great marksmanship is deciding what the target was AFTER you've shot.
GreyWolf is offline  
Old 03-04-2011, 05:28 PM   #7 (permalink)
Banned
 
Zeraph's Avatar
 
Location: The Cosmos
err ya, the first part of what grey wolf said. About the air friction heating itself.
Zeraph is offline  
Old 03-05-2011, 11:21 AM   #8 (permalink)
Banned
 
Zeraph's Avatar
 
Location: The Cosmos
Also, why does plasma cause a radio blackout?

Am I the only one sick enough to wonder what would happen to a human in that insane wind tunnel...?
Zeraph is offline  
Old 03-06-2011, 12:09 PM   #9 (permalink)
Invisible
 
yournamehere's Avatar
 
Location: tentative, at best
Quote:
Originally Posted by Zeraph View Post
. . . Am I the only one sick enough to wonder what would happen to a human in that insane wind tunnel...?
The same thing that would happen if you were standing on the surface of the sun; minus the intense gravity and radiation, of course. But you'd be vaporized, just the same. Oh - and you'd lose cell phone reception.
__________________
If you want to avoid 95% of internet spelling errors:
"If your ridiculous pants are too loose, you're definitely going to lose them. Tell your two loser friends over there that they're going to lose theirs, too."
It won't hurt your fashion sense, either.
yournamehere is offline  
Old 03-06-2011, 01:37 PM   #10 (permalink)
Sober
 
GreyWolf's Avatar
 
Location: Eastern Canada
A plasma is a state of matter where the material has all become ionised. The ionised material is radio opaque in much the same way that water or earth is, only more so. The electrically charged plasma ions interfer with radio waves extremely effectively. Think of the the problems with radio reception in the far north during a strong aurora, caused by the flow of charged (ionised) particles from the sun streaming into the magnetic poles. The ionisation field around a re-entering space ship is orders of magnitude worse.
__________________
The secret to great marksmanship is deciding what the target was AFTER you've shot.
GreyWolf is offline  
Old 03-06-2011, 06:12 PM   #11 (permalink)
Banned
 
Zeraph's Avatar
 
Location: The Cosmos
Quote:
Originally Posted by yournamehere View Post
The same thing that would happen if you were standing on the surface of the sun; minus the intense gravity and radiation, of course. But you'd be vaporized, just the same. Oh - and you'd lose cell phone reception.
But would you go into flames briefly? Would you see the skeleton just before it vaporizes? Would you just poof? I've always been curious since movies have done similar things (with radiation/heat not air speed).
Zeraph is offline  
Old 03-22-2011, 05:38 PM   #12 (permalink)
Oh dear God he breeded
 
Seer666's Avatar
 
Location: Arizona
Given the set up on that tunnel, I don't thinkk that a person in it would burst into flames. They would, however, be exploded all over the back wall when the pressure wave hit them. Barring DNA tests, I don't think there would be enough left intact to even tell if it was human, let alone who it was.
__________________
Bad spellers of the world untie!!!

I am the one you warned me of

I seem to have misplaced the bullet with your name on it, but I have a whole box addressed to occupant.
Seer666 is offline  
 

Tags
air, combust, fast, moving, point, things


Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -8. The time now is 03:28 AM.

Tilted Forum Project

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
© 2002-2012 Tilted Forum Project

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360