• Post Reply Bookmark Topic Watch Topic
  • New Topic
programming forums Java Mobile Certification Databases Caching Books Engineering Micro Controllers OS Languages Paradigms IDEs Build Tools Frameworks Application Servers Open Source This Site Careers Other Pie Elite all forums
this forum made possible by our volunteer staff, including ...
Marshals:
  • Campbell Ritchie
  • Jeanne Boyarsky
  • Ron McLeod
  • Paul Clapham
  • Liutauras Vilda
Sheriffs:
  • paul wheaton
  • Rob Spoor
  • Devaka Cooray
Saloon Keepers:
  • Stephan van Hulst
  • Tim Holloway
  • Carey Brown
  • Frits Walraven
  • Tim Moores
Bartenders:
  • Mikalai Zaikin

Seven Times the Speed of Sound

 
Ranch Hand
Posts: 2937
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
Pack you bags and go for a ride from Boston to San Francisco, -- it will take you about 37 minutes to cover that distance on a new NASA's experimental jet. If that's not impressive, get this, -- the jet has no moving parts and uses air for fuel. Air?! Are there cowboys with mechanical engineering background out there who can explain to me how this thing works? Most puzzling, why are we still talking about the record high gas prices, dependence on Middle East, and pollution?
 
Wanderer
Posts: 18671
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
I'm not an exert in this of course, and what follows may well contain errors. But here's what I've come up with, after a little research:

It is the first time a supersonic-combustion ramjet, or scramjet, which uses air for fuel, had traveled so fast, flight engineer Lawrence Huebner told reporters.


I suspect this is a misquote. Hueber probably just told them it was the first time a scramjet had traveled so fast, and the reporter inserted "which uses air for fuel", apparently based on a misunderstanding of what "air-breathing engine" meant.
The basic function of an aerospace engine - propeller, jet, or rocket - is to generate forward thrust by throwing some other mass in the opposite direction of travel. For this you need two things: something to throw, and a source of energy to throw it with. In the case of rockets, the rocket fuel provides both - it's a source of energy, and the fule itself is the mass that gets thrown backwards. This allows a rocket to operate in vacuum, which is cool, but it means that in order to have a lot thrust, you need to carry a large mass of fuel. Thus rockets tend to have big bulky fuel tanks associated with them. This is a major limitation as you try to go faster and faster with rockets - to go faster, you need more fuel, which icreases your mass, which means the acceleration you get by burning that fuel will decrease, since you're pushing more mass. You get a bad case of diminishing returns.
In the case of propellers and jets, the thing you throw backwards is air, which is readily available as long as you're not trying to go into space. But you still need a source of energy; that's where the fuel comes in. Since you don't need the fuel to have much mass, you can use fuel with higher energy/mass ratio than you would for a rocket; hydrogen seems to be the preferred choice here. Here's NASA's press release about the latest X-43A flight. Note it says nothing about using air for fuel, and does say that hydrogen is used as fuel. So, quoting from the original CNN article here, "The "air-breathing" jet was not bogged down with heavy fuel tanks." That doesn't mean there was no fuel, just that there was much less of it than there would have been for a rocket.
Most puzzling, why are we still talking about the record high gas prices, dependence on Middle East, and pollution?
Well there are people working on figuring out how to use hydrogen as an alternate fuel for, say, an automobile. But they're not there yet. It's expensive to create (electrolysis is fairly simple, but it takes a lot of electricity to get a little hydrogen). And it's difficult to store safely; as was discovered in the past. It would certainly be cool if we can move away from using fossil fuels, but there are still a few details to work out it seems...
[ March 28, 2004: Message edited by: Jim Yingst ]
 
John Smith
Ranch Hand
Posts: 2937
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
Jim: Since you don't need the fuel to have much mass, you can use fuel with higher energy/mass ratio than you would for a rocket; hydrogen seems to be the preferred choice here. Here's NASA's press release about the latest X-43A flight. Note it says nothing about using air for fuel, and does say that hydrogen is used as fuel.
BBC was a little more scientific than CNN: "Scramjets burn hydrogen but take their oxygen from the air, which is forced into the engine at very high speed".
So, the engine mixes hydrogen and oxygen, creates the continuous blasts, and uses the the resulting energy to propel the jet forward? Is that how it works? I've got and idea: do not discard H2O that is a product of this mix. Instead, break it into H and O, and use both again. Ain't that beatiful, -- the pollutent itself is the fuel? Oh, forgot one thing, -- what suorce of fuel would we use to break H2O?
 
Ranch Hand
Posts: 3404
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
I doubt any of us will be clambering abroad one of those in our lifetime.
How is this likely to change your lifestyle ?
Lower taxes, no nerd-like stopping for recharging and can go for much longer.

Completely reconceived, the gas/electric Prius offers all the power of a conventional vehicle, an unheard-of 55 estimated combined mpg,



Start driving the new, mid-size 2004 Prius with Hybrid Synergy Drive�. Completely reconceived, the gas/electric Prius offers all the power of a conventional vehicle, an unheard-of 55 estimated combined mpg, [2] available BluetoothTM [3] technology and an Advanced Technology Partial Zero Emission Vehicle (AT-PZEV) rating. [4] Prius buyers may also be eligible for a federal tax deduction. Finally, you never need to plug-in for recharging -- which makes the Prius a solution with no cords attached.
[ March 28, 2004: Message edited by: HS Thomas ]Advanced Technology Partial Zero Emission Vehicle (AT-PZEV)
[ March 29, 2004: Message edited by: HS Thomas ]
 
Yeah, but is it art? What do you think tiny ad?
a bit of art, as a gift, the permaculture playing cards
https://gardener-gift.com
reply
    Bookmark Topic Watch Topic
  • New Topic