Confuscius
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Space Shuttle Reentry Speed

Mon Jun 23, 2008 8:52 pm



Is this true? Sounds a wee bit fast.
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Blackprojects
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RE: Space Shuttle Reentry Speed

Mon Jun 23, 2008 9:04 pm

Maximum Shuttle re-entry speed is MACH 25 above which Mach Numbers becombes Pointless as you are going so fast its Ludicrouse Speed!

But 18 times the Speed of Light Methinks a Gremlin got into the CNN studios.

 Wow!  old 
 
art
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RE: Space Shuttle Reentry Speed

Mon Jun 23, 2008 9:25 pm



Quoting BlackProjects (Reply 1):
18 times the Speed of Light Methinks a Gremlin got into the CNN studios

Yea. About 0.000000025 times the speed of light was what I think they meant (assuming 17,500 mph orbit speed).

(speed of light about 300,00 km per sec; speed of shuttle about 7.8 km per sec)

BTW is there a speed of sound in space?
 
Blackprojects
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RE: Space Shuttle Reentry Speed

Mon Jun 23, 2008 9:37 pm

No NO Speed of Sound in Space thats why MACH Numbers get forgotten about once you reach Orbit as its not worth talking about as every thing is done in Miles / KMs a Second.

Also no Air Molicules to react to the Vehicle in Orbit so NO SONIC BOOM = No Sound in Spaceapart from that inside the Vehicles.
 
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Moose135
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RE: Space Shuttle Reentry Speed

Mon Jun 23, 2008 9:38 pm



Quoting Art (Reply 2):
BTW is there a speed of sound in space?

"In space no one can hear you scream."  Smile
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GST
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RE: Space Shuttle Reentry Speed

Mon Jun 23, 2008 10:21 pm



Quoting Moose135 (Reply 4):
"In space no one can hear you scream."

I have no idea but that just made me keel over laughing.

And I wouldnt say it was gremlins in CNN so much as a prank monkey of gorilla proportions.
 
Thorny
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RE: Space Shuttle Reentry Speed

Mon Jun 23, 2008 10:32 pm



Quoting GST (Reply 5):
And I wouldnt say it was gremlins in CNN so much as a prank monkey of gorilla proportions.

It was CNN's rushing to put the headline up in the minutes after the STS-107 accident in 2003, and not doing any proofreading first. Haste makes red face.
 
SlamClick
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RE: Space Shuttle Reentry Speed

Tue Jun 24, 2008 4:16 pm

Certainly not. Otherwise it would be very difficult to get pictures of it.  Smile

Quoting BlackProjects (Reply 3):
NO Speed of Sound in Space

The speed often quoted in relation to the space shuttle re-entry refers to the calculated mach number as it begins to encounter the sensible earth's atmosphere. These may start in the M 25 range and the one shuttle recovery I've seen they made a series of descending turns to scrub off energy so the chase planes could renezvous with them at about M1.0 or so in the stratosphere. During this set of maneuvers a sonic boom was a real possibility but certainly not while it is in orbit.
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mark5388916
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RE: Space Shuttle Reentry Speed

Tue Jun 24, 2008 4:54 pm

When it lands, it DEFINITLY makes a sonic boom, a double acturally. I've been in Lancaster when id landed at EDW and here in Riverside one time it landed in EDW after an app from the south. It makes a very clear boom-boom when it goes over.

Mark
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Confuscius
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RE: Space Shuttle Reentry Speed

Tue Jun 24, 2008 5:01 pm



Quoting BlackProjects (Reply 1):
Pointless as you are going so fast its Ludicrouse Speed!

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Thorny
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RE: Space Shuttle Reentry Speed

Tue Jun 24, 2008 5:10 pm

I've heard the boom from San Angelo, Texas, something like 1,000 miles uprange from KSC. It was a few minutes after a spectacular re-entry overflight. The boom was faint , but it was the middle of the night. Set the neighborhood dogs barking. That was STS-109 in March 2002.

With luck, we'll see/hear the same thing in October with STS-125 (another night launch/landing).
 
curlyheadboy
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RE: Space Shuttle Reentry Speed

Tue Jun 24, 2008 8:24 pm



Quoting Moose135 (Reply 4):
"In space no one can hear you scream."

Lol, Alien! Btw, the Nostromo descended through atmosphere without any drag heating and was VTOL, way better than the shuttle and it was a '70s design as well  Wink Big grin

Quoting Mark5388916 (Reply 8):
When it lands, it DEFINITLY makes a sonic boom, a double acturally. I've been in Lancaster when id landed at EDW and here in Riverside one time it landed in EDW after an app from the south. It makes a very clear boom-boom when it goes over.

Mark

Absolutely! Shuttle's nose and the tail break the sound barrier some 0.5 seconds apart, that's the 2 booms that are heard from the ground.
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HaveBlue
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RE: Space Shuttle Reentry Speed

Wed Jun 25, 2008 5:14 pm

I have heard the sonic booms many times, ever since I was a kid when the shuttle first started landing at nearby KSC. The first time I heard it it scared the sh*t out of me. And indeed is a double boom. Ever since the Columbia accident that has changed, now that the approach is from the SW across the gulf instead of across CA and on in. I live in Daytona Beach so the flightpath no longer crosses me.

And I would imagine that it starts creating a sonic boom audible to the ground whenever it gets in the 100,000' altitude or lower, as soon as the air is dense enough to carry that sound to the ground. The SR-71 flew around that altitude and I'm pretty sure that boom could be heard on the ground.
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SlamClick
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RE: Space Shuttle Reentry Speed

Wed Jun 25, 2008 6:10 pm



Quoting CURLYHEADBOY (Reply 11):
Shuttle's nose and the tail break the sound barrier some 0.5 seconds apart

That timing doesn't sound quite right. From nose to tail is only 122 feet (overall length) so if it was going its own length in 0.5 seconds that would only be 244 feet per second or about 145 knots - hardly sonic speed.

Quoting HaveBlue (Reply 12):
And indeed is a double boom.

I did not hear the sonic boom the one re-entry I saw. I was standing in a very noisy place quite a ways away. I have heard quite a few of them, though, dating back to the mid-1950s before there was any legislation regarding them. I think just about any time you are right under the footprint you will get that double boom effect from the nose and tail waves. Google Harry Gann's great photo of the transonic F-4 at El Toro! Last one I heard was from an SR-71 overhead Beale AFB at 15000.

Quoting HaveBlue (Reply 12):
The SR-71 flew around that altitude and I'm pretty sure that boom could be heard on the ground.

I have it on 'some authority' that by the time high-altitude shockwaves get to the ground the energy is so diffused that the human ear is not likely to perceive it as a boom. "Skyquake" anyone?
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787atPAE
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RE: Space Shuttle Reentry Speed

Thu Jun 26, 2008 12:54 am



Quoting BlackProjects (Reply 3):
No NO Speed of Sound in Space thats why MACH Numbers get forgotten about once you reach Orbit as its not worth talking about as every thing is done in Miles / KMs a Second.

Back when I was on the shuttle program, it was explained to me that above a certain altitude, NASA used 1000 fps as the reference for the speed of sound. It doesn't make sense to try to calculate the local speed of sound when there's only a couple molecules of stuff in your vicinity.
 
connies4ever
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RE: Space Shuttle Reentry Speed

Thu Jun 26, 2008 1:18 am



Quoting BlackProjects (Reply 3):
No NO Speed of Sound in Space thats why MACH Numbers get forgotten about once you reach Orbit as its not worth talking about as every thing is done in Miles / KMs a Second.

Also no Air Molicules to react to the Vehicle in Orbit so NO SONIC BOOM = No Sound in Spaceapart from that inside the Vehicles.

Actually there is: c (speed of sound) in classical mechanics is generally given as partial derivative of p over partial derivative of density, then you take the square root. Since there is measurable pressure in space, there is therefore density, and you can derive a value for c. Wouldn't be very much you.
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curlyheadboy
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RE: Space Shuttle Reentry Speed

Thu Jun 26, 2008 8:52 am



Quoting SlamClick (Reply 13):
Quoting CURLYHEADBOY (Reply 11):
Shuttle's nose and the tail break the sound barrier some 0.5 seconds apart

That timing doesn't sound quite right. From nose to tail is only 122 feet (overall length) so if it was going its own length in 0.5 seconds that would only be 244 feet per second or about 145 knots - hardly sonic speed.

I trust you Slam, though I remember to have read the half-second timing somewhere, did a search and found this:

Quote:
"The nose and tail shock waves are usually of similar strength. The time interval between the nose and tail shock waves is primarily dependent on the size of the aircraft and its altitude. Most people on the ground cannot distinguish between the two and they are usually heard as a single sonic boom. As the time interval increases, two booms are heard. A small fighter-type aircraft about 50 ft long will generate nose and tail shock waves of less than a tenth of a second (0.1 sec). The ear usually detects these as a single sonic boom."

"The interval between nose and tail shock waves on the Space Shuttles, which are 122 ft long, is about one-half of a second (0.50 sec), making the double boom very distinguishable."

You can access the entire document and much more at NASA Spacelink

John Haberman, Space Scientist
NASA/Goddard Space Flight Center

So I thought it was about right and posted it... maybe the factor is the altitude at which the orbiter breaks the sound barrier on its way down?  Smile
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HaveBlue
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RE: Space Shuttle Reentry Speed

Thu Jun 26, 2008 1:20 pm



Quoting SlamClick (Reply 13):
Google Harry Gann's great photo of the transonic F-4 at El Toro!

I've had this on my computer for quite some time, as part of an extensive collection of shockwave photos I have archived. As soon as you mentioned it, I knew what you were referencing Slam.

http://img262.imageshack.us/img262/6103/f4shockwavesvj3.jpg
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SlamClick
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RE: Space Shuttle Reentry Speed

Thu Jun 26, 2008 3:53 pm



Quoting CURLYHEADBOY (Reply 16):
So I thought it was about right and posted it... maybe the factor is the altitude at which the orbiter breaks the sound barrier on its way down?

Okay, at the point it reaches the ground a half-second? Perhaps. I have a great OLD video of a film Shell Oil made about supersonic flight, which I used to show my students. One useful thing, if you can picture this, because I can't post it, is that it talked about the shockwave being a pressure pulse, radiating out in all directions at once like ripples from a pebble tossed into a pond. Now picture each theoretical point on the airplane producing one of these little pressure waves of its own. Now that part of each wave that rolls away downward, toward the ground will be traveling at the speed of sound and if the airplane is also it will reach the ground at about a 45 degree point behind the airplane - but it will reach the ground simultaneously with all the other little pressure waves from each of the millions of little points on the airplane and they add themselves together to create a really BIG wave at that point.

Similar to a boat in the water, a plane makes a bow wave and a stern wave. I don't understand how the time increases between the two waves being formed and the two waves reaching the same spot on the ground but I'm sure there is rational explanation. Anyway I am certainly willing to accept what you posted there, even if I don't really understand why. Thanks.

Quoting HaveBlue (Reply 17):

That is the one! One of the all-time best airplane photos ever taken. Oh, and pretty cool that is Bob Hoover parked on the far side. That looks like a shockwave that might knock you down!

I used to fly with a guy who'd been in VX-4 but I don't think that was him flying. I'll have to ask one day. And I was wrong. I thought it was El Toro. Says it was Point Mugu, which makes more sense.
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