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Author
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Topic: Sonic booms and spacecraft reentries
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cspg
Member Posts: 6210
From: Geneva, Switzerland
Registered: May 2006
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posted 12-01-2008 12:16 AM
   
Watching the YouTube video of the STS-126 landing and hearing the sonic booms, a couple of questions came up. - Are sonic booms (supersonic to subsonic) apply to all space vehicles, irrespective of their shapes? In other words, were there sonic booms with the Apollo capsules? And shouldn't there be sonic boom at launch too?
- What implications, if any, such booms will have on the commercial space industry? Folks in New Mexico (and surrounding states) might not appreciate those booms... After all, Concorde wasn't allowed to fly supersonic over the US for that reason, no?
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GACspaceguy
Member Posts: 2474
From: Guyton, GA
Registered: Jan 2006
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posted 12-01-2008 08:30 AM
All shapes that move at the speed of sound or greater will produce a sonic boom. The acoustic signature of the vehicle is dependant on a number of variables and one is the configuration of the vehicle. Also it is important at what altitude the vehicle goes subsonic as this will determine speed of sound due to density, temperature and pressure. As far as the Shuttle going up hill, the sound of the boom would be insignificant compared to the SSME and SRBs sound signature.The issue with over flight of aircraft with a sonic boom is a commercial aircraft issue and may not apply to spacecraft as this would be a “new ocean”. The business aviation community is in work trying to get this rule changed so this may not be an issue once a commercial spacecraft enters into a regular service.
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mjanovec
Member Posts: 3811
From: Midwest, USA
Registered: Jul 2005
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posted 12-01-2008 08:34 AM
quote:
Originally posted by cspg:
And shouldn't there be sonic boom at launch too?
If you watch the footage of the Gemini 2 launch (found on the Spacecraft Films Gemini set), you'll hear a very definite sonic boom. |
cspg
Member Posts: 6210
From: Geneva, Switzerland
Registered: May 2006
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posted 12-01-2008 08:52 AM
quote:
Originally posted by GACspaceguy:
The acoustic signature of the vehicle is dependant on a number of variables and one is the configuration of the vehicle. Also it is important at what altitude the vehicle goes subsonic as this will determine speed of sound due to density, temperature and pressure.
And I guess that will determine whether the sonic boom will be heard or not. Just wondering if Apollo recovery crew heard a boom or not. quote:
As far as the Shuttle going up hill, the sound of the boom would be insignificant compared to the SSME and SRBs sound signature.
Ha-ha, haven't thought about that!  |
ea757grrl
Member Posts: 729
From: South Carolina
Registered: Jul 2006
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posted 12-01-2008 09:33 PM
quote:
Originally posted by cspg:
Just wondering if Apollo recovery crew heard a boom or not.
From "10:56:20 PM EDT 7/20/1969," here's what Ron Nessen, one of the television pool reporters aboard USS Hornet, said on live television as Apollo 11 descended: "There's the double sonic boom." (Nessen also made reference to "we should be hearing the double sonic boom as the spacecraft comes down.") |
spaceman1953
Member Posts: 953
From: South Bend, IN
Registered: Apr 2002
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posted 12-01-2008 11:32 PM
So can you verify that the sonic booms we heard as kids (1950s/1960s) in North Central Indiana were sonic booms from military aircraft (as we were told by our parents they were)? Certainly commercial aircraft did not/would not produce them, right? |
ea757grrl
Member Posts: 729
From: South Carolina
Registered: Jul 2006
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posted 12-02-2008 06:12 AM
quote:
Originally posted by spaceman1953:
Certainly commercial aircraft did not/would not produce them, right?
They wouldn't. The only commercial jet aircraft known to have intentionally broken the sound barrier (prior, obviously, to Concorde and Tu-144) was a Canadian Pacific DC-8 (CF-CPG, flying under Douglas test registration N9604Z) on a special, carefully-controlled test run over Edwards AFB in August, 1961. Concorde and Tu-144 broke the sound barrier many times over, but this single DC-8 is the only conventional passenger jet known to have done it. The conditions under which it did this — including operating at maximum takeoff thrust during the supersonic run — would have made normal operation at such speeds impractical. |
SpaceAholic
Member Posts: 4437
From: Sierra Vista, Arizona
Registered: Nov 1999
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posted 12-02-2008 07:39 AM
Their was a 747 also reported to have broken it (though not intentionally) back in the 80's after loss of flight control and entry into a steep dive... |
BMckay
Member Posts: 3218
From: MA, USA
Registered: Sep 2002
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posted 12-02-2008 07:57 AM
My favorite quote on a signed photo: "We only make the booms, not hear them." — Ken Cockrell, Astronaut |
ea757grrl
Member Posts: 729
From: South Carolina
Registered: Jul 2006
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posted 12-02-2008 08:32 AM
quote:
Originally posted by SpaceAholic:
Their was a 747 also reported to have broken it (though not intentionally) back in the 80's after loss of flight control and entry into a steep dive...
Yeah, I had meant to add the word "intentionally" to what I wrote above, but forgot... |
SpaceDust
Member Posts: 115
From: Louisville, Ky USA
Registered: Mar 2006
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posted 12-02-2008 12:00 PM
quote:
Originally posted by spaceman1953:
So can you verify that the sonic booms we heard as kids (1950s/1960s) in North Central Indiana were sonic booms from military aircraft (as we were told by our parents they were)?
I would say "yes"! I remember in the early 60's when we would hear the booms in Louisville and then run out to watch the jet scream across the sky. If they did it here I'm sure they did it in Indiana. Gee, I miss those days. |
Philip
Member Posts: 5952
From: Brussels, Belgium
Registered: Jan 2001
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posted 12-02-2008 12:10 PM
I believe the short shape of the orbiter causes the double sonic boom. |
SpaceAholic
Member Posts: 4437
From: Sierra Vista, Arizona
Registered: Nov 1999
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posted 12-02-2008 01:36 PM
They are successive bow and wake shocks generated by the vehicles blunt geometry. |
Robert Pearlman
Editor Posts: 42981
From: Houston, TX
Registered: Nov 1999
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posted 12-02-2008 01:48 PM
I once either read or was told that the shuttle actually trips three sonic booms, but two are so close together that you cannot discern the difference. The first is triggered by the nose, the second by the wings' leading edge and the third by the vertical stabilizer. It is the latter two that were said to blend together to form an audible single boom. Can someone confirm this as true (or false)? |
SpaceAholic
Member Posts: 4437
From: Sierra Vista, Arizona
Registered: Nov 1999
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posted 12-02-2008 02:45 PM
The second boom (wake shock) results from a process analogous to cavitation as air collapses back into the area in which it has been displaced by the bow shock. This occurs well aft of the flight vehicle. |
Rob Joyner
Member Posts: 1308
From: GA, USA
Registered: Jan 2004
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posted 12-02-2008 05:06 PM
quote:
Originally posted by Robert Pearlman:
Can someone confirm this as true (or false)?
I mentioned the three sonic booms here before but I can't recall where I first heard about it. Your info is correct as I remember it though, the first boom is from the nose and the second and third are from the wings and tail. |
SpaceAholic
Member Posts: 4437
From: Sierra Vista, Arizona
Registered: Nov 1999
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posted 12-02-2008 05:45 PM
Shuttle Length: 184 feet
Shuttle Velocity at time of Sonic Booms: greater then 1100 FPSFlight control surfaces travel at the same velocity as the rest of the spacecraft yet the two booms are displaced by at least 550 feet (minimum distance shuttle will have traveled in 1/2 second - its probably a lot further depending on actual altitude/airspeed) . Don't doubt that separate smaller inaudible shocks are produced on the rest of the airframe but cant see how that would account for the second ground detectable N-wave. |
ilbasso
Member Posts: 1522
From: Greensboro, NC USA
Registered: Feb 2006
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posted 12-02-2008 07:09 PM
quote:
Originally posted by SpaceDust:
I remember in the early 60's when we would hear the booms in Louisville and then run out to watch the jet scream across the sky.
Just about the only thing that was more fun than the sonic booms was riding my bike along behind the DDT fogging truck and breathing in the sweet, thick smoke. I'm surprised I'm still alive!! |
Jim Behling
Member Posts: 1463
From: Cape Canaveral, FL
Registered: Mar 2010
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posted 04-09-2012 09:22 AM
quote:
Originally posted by GACspaceguy:
As far as the Shuttle going up hill, the sound of the boom would be insignificant compared to the SSME and SRBs sound signature.
Sorry to open an old thread, but it came up in a search on sonic booms. The above statement is wrong. The shuttle and some other launch vehicles do have a sonic boom "issue" during launch, it just doesn't matter on the east coast. As the shuttle ascends and arcs over, the sonic boom gets focused in an area down range. Off of Florida, there isn't anything there. At Vandenberg Air Force Base, it would be an issue for the Channel Islands, which are seal breeding grounds. If the shuttle launched while the seals would be nursing, the sonic boom would have made them rush to the water, trampling the babies. There were thoughts of banning launches during this timeframe much like Japan and its fishing season. The issue got so much attention that there was a 62-A with a seal on it. |
Jay Chladek
Member Posts: 2272
From: Bellevue, NE, USA
Registered: Aug 2007
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posted 04-12-2012 05:36 PM
Concerning possible sonic booms over New Mexico, I doubt they would be too discernible given that the SpaceshipTwo vehicles are going to be going mach rather high up while ascending and the craft isn't that big compared to a commercial airliner anyway (so two booms will likely blend into one). When the feather gets deployed to slow down, it will slow down to subsonic speed rather quick. Besides, White Sands tested all sorts of rockets throughout the past six decades and nobody seemed to complain about the sonic booms coming from them.I managed to hear a sonic boom from shuttle once as STS-120 Discovery was doing a descending node reentry over the United States (first since 107 and I believe one of only two done for the final shuttle flights with the other being STS-131). The reentry path took it over east central Nebraska, so I drove west from Omaha to see if I could see it ending up near Seward, NE. I didn't see the plasma trail, but I heard a sudden dull rumble which was most certainly a boom. I went inside the building (an aircraft hangar) and mentioned it to the mechanics inside and they said "is that what that was?" since they heard it as well and thought something had exploded off in the distance. Consulting others later that day, it was heard around Omaha as well since the track took Discovery over Topeka, KS. It was not the distinctive "boom boom" but rather a combined rumble since the shuttle was still going so fast and it blended the shockwaves together together. It freaked me out a bit considered the orbiter would have been at around 200,000 feet going probably Mach 14 when it did that. When I got a chance to interview Pam Melroy almost a year later (STS-120's CDR), she was pleasantly surprised to hear that as she had a bet going with a couple of the other shuttle pilot/commanders in the astronaut office as to how much of a sonic boom could be heard far west in the track when the shuttle was very high up. She said my account was the furthest west sonic boom she was ever made aware of. I had hoped to hear one on STS-131's return, but due to a single orbit delay for weather, the reentry track went a bit too far south of Omaha for me to see or hear anything. If Discovery had reentered on that first orbit, she would have tracked just off to the north of Omaha and probably would have been very visible in the sky if one was looking in the right place. |
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