Hypersonic Aircraft: Flying from LA to NY in 30 mins?

  • Thread starter Char. Limit
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In summary: That's what causes the "sonic boom". So, to get back to your question, if a plane is flying along supersonically and then slows down to subsonic speeds, the shock is no longer being dragged off the back of the plane and so the "sonic boom" stops. (To be fair, you'll still have a (very) small boom from the nose of the plane as it goes from supersonic flow to subsonic flow there, but that's typically a lot less intense than the "sonic boom" from the shock.)In summary, a hypersonic passenger jet would be able to travel from Los Angeles to New York
  • #1
Char. Limit
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http://www.latimes.com/business/la-fi-hypersonic-20100527,0,764506.story

I found this to be awesome, although I wonder what size of sonic boom a hypersonic passenger jet would make... Nevertheless, imagine flying from Los Angeles to New York in 30 minutes... and we have the technology to go hypersonic, how long could it take to develop a hypersonic passenger jet?

In a word, awesome.
 
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  • #2
The supersonic jet didn't work out so well...
 
  • #3
They should put a camera on it and fly it by some reference points so we can see just how fast it's going. Like when I run through the hallway in my house, I'm like lightning. But when I get on a football field, I'm the slowest person there. What gives?
 
  • #4
Char. Limit said:
http://www.latimes.com/business/la-fi-hypersonic-20100527,0,764506.story

I found this to be awesome, although I wonder what size of sonic boom a hypersonic passenger jet would make... Nevertheless, imagine flying from Los Angeles to New York in 30 minutes... and we have the technology to go hypersonic, how long could it take to develop a hypersonic passenger jet?

In a word, awesome.
The sonic boom occurs when the aircraft passes through the 'sound barrier'. Once it goes through it's supersonic - actually transonic (~0.7 to 1.2). Supersonic generally applies to M >1.2 to 5. Hypersonic, M > 5.

Definition: Where there is mixed sub- and supersonic local flow (M = .6 or .7 to 1.2).
Note: Hypersonic vehicles with bow shocks necessarily have a region of subsonic flow
behind the shock, so there is an element of transonic flow in these cases also.
http://www.aoe.vt.edu/~mason/Mason_f/ConfigAeroTrans.pdf

Most people apparently define the transonic range M = 0.8 to 1.2.
http://aero-comlab.stanford.edu/Papers/SympTransIV_DACAJ.pdf
 
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  • #5
No Astronuc. A supersonic plane drags a shock wave behind it as it flies. What you describe is a Hollywood dramatization.

Also, the strength varies considerably with altitude so a hypersonic plane woulnt necessarily be audible from the ground.
 
  • #6
russ_watters said:
Also, the strength varies considerably with altitude so a hypersonic plane woulnt necessarily be audible from the ground.

That's what they thought back in the day but test showed that even at great altitudes the boom was 'still a problem'.

The amount of 'boom' is actually more of a function on wing span and the planes weight.
 
  • #7
I have a question.

What happens if you're traveling faster than the speed of sound... and then you slow down, passing the sound barrier again, back into the "traveling slower than the speed of sound" speeds?

Do you generate another sonic boom?
 
  • #8
There is no such thing as a sound barrier. However there are shock waves which remain there as long as the aircraft is supersonic or transsonic.
 
  • #9
Can someone clarify the "sonic boom" for me. As I understood it the boom doesn't just happen once. It would be progressing continually along the ground as the displaced air behind the aircraft rushed back together behind the aircraft. The boom wouldn't just happen once the aircraft passed the "barrier". It would be heard by whomever was under the aircraft when it passed overhead. Am I mistaken?
 
  • #10
Andre said:
There is no such thing as a sound barrier. However there are shock waves which remain there as long as the aircraft is supersonic or transsonic.

So you're saying that, the sonic boom noise "turns on" when the object travels faster than sound, and then "turns off" when it slows down to speeds lower than that of the sound..?
 
  • #11
Andre said:
There is no such thing as a sound barrier. However there are shock waves which remain there as long as the aircraft is supersonic or transsonic.

Ah, I think you answered my question as I was typing it.
 
  • #12
pivot said:
So you're saying that, the sonic boom noise "turns on" when the object travels faster than sound, and then "turns off" when it slows down to speeds lower than that of the sound..?
That is correct. A plane traveling faster than the speed of sound drags a cone-shaped shock wave behind it. The "boom" you hear is this cone shaped shock wave being dragged past you.
 
  • #13
Char. Limit said:
http://www.latimes.com/business/la-fi-hypersonic-20100527,0,764506.story

I found this to be awesome, although I wonder what size of sonic boom a hypersonic passenger jet would make... Nevertheless, imagine flying from Los Angeles to New York in 30 minutes... and we have the technology to go hypersonic, how long could it take to develop a hypersonic passenger jet?

In a word, awesome.

Wow, this is amazing! That thing can travel almost a mile in a single second!
 
  • #14
One more point on top of all of this:

The boom that we hear is associated with a certain type of pressure pulse. We call it in N wave. As the "sonic boom" passes the bystander on the ground, there is a sudden sharp increase in pressure, followed by a sudden sharp decrease (looks kind of like an N). It is this sharp change in pressure that sounds so loud.

NASA has been doing a lot of work to "smooth" out the N wave as to decrease the intensity of the sonic boom. However, I'm not so sure designs could incorporate both features to decrease the sound while enabling hypersonic flight.
 
  • #15
pivot said:
I have a question.

What happens if you're traveling faster than the speed of sound... and then you slow down, passing the sound barrier again, back into the "traveling slower than the speed of sound" speeds?

Do you generate another sonic boom?

One thing, just to give a word to your quoted phrase. I believe that speeds slower than the speed of sound are described as "subsonic".

Although I'm not sure what transsonic is... "beyond" the speed of sound?
 
  • #16
Char. Limit said:
Although I'm not sure what transsonic is... "beyond" the speed of sound?
Transonic is the speed range right around the speed of sound (around .8-1.2 or .9 to 1.1 mach, depending on the plane), where parts of an airplane are flying through subsonic air and parts of it are flying through supersonic air. In particular, as air travels over the top surface of a wing, it speeds up. At the point on the wing where it speeds-up to Mach 1, a shock wave forms. As the plane accelerates, this shock wave moves backwards on the wing until it reaches the trailing edge when the plane hits Mach 1. The reason this speed region is characterized by unstable flight and high drag is these shock waves are not stable and move around on the plane. For that reason, it is best for planes not to linger in this region, but to accelerate through it relatively quickly.

See diagrams halfway down this page: http://www.flightlearnings.com/high-speed-flight-shock-waves/480/
 
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  • #17
Char. Limit said:
Although I'm not sure what transsonic is... "beyond" the speed of sound?

Spanning the speed of sound, i.e. .8 to 1.2.


BTW, there are actually multiple booms, all very close together. There's a shock wave from each leading edge of a protrusion on a plane. Usually one can hear, at most, two booms, almost on top of each other - one from the nose, and another from the wing leading edge (or from the tail).

[PLAIN]http://blogs.discovery.com/news_space/images/2008/11/03/t38.jpg
 
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Related to Hypersonic Aircraft: Flying from LA to NY in 30 mins?

1. How does a hypersonic aircraft fly from LA to NY in just 30 minutes?

Hypersonic aircraft are able to achieve such high speeds because they travel at supersonic speeds, which is faster than the speed of sound. This means they can travel at speeds of Mach 5 or higher, which is more than 3,800 miles per hour. These high speeds allow the aircraft to cover long distances in a short amount of time.

2. What technology is used to power a hypersonic aircraft?

Hypersonic aircraft use advanced propulsion systems, such as scramjet engines, to reach such high speeds. These engines use the oxygen in the atmosphere to combust fuel, which generates thrust and propels the aircraft forward. This technology is still in development and has not yet been fully implemented in commercial aircraft.

3. How is a hypersonic aircraft able to withstand the extreme temperatures of hypersonic flight?

Hypersonic aircraft are designed with special materials and thermal protection systems to protect them from the intense heat generated by traveling at such high speeds. These materials can withstand temperatures of over 3,500 degrees Fahrenheit, which is necessary for successful hypersonic flight.

4. What are the potential benefits of using hypersonic aircraft for commercial travel?

Hypersonic aircraft have the potential to revolutionize air travel by drastically reducing travel time. This could lead to increased productivity, as well as reduced fuel consumption and emissions. It could also open up new opportunities for global trade and tourism.

5. Are there any safety concerns with hypersonic flight?

As with any new technology, there are still safety concerns that need to be addressed with hypersonic flight. These include potential risks from extreme temperatures and high speeds, as well as the need for advanced air traffic control systems. However, extensive research and testing are being conducted to ensure the safety of hypersonic flight in the future.

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