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X-43A? (Score:5, Informative)
http://en.wikipedia.org/wiki/Boeing_X-43 [wikipedia.org]
This is cool, yes, but the emphasis on "first" seems a bit off.
Re:X-43A? (Score:5, Funny)
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Re:X-43A? (Score:4, Insightful)
Ah I see... as opposed to the many airbreathing scramjets ignited outside earths atmosphere.
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Re:X-43A? (Score:4, Insightful)
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100,000 feet is well within the atmosphere (Score:4, Informative)
The Stratosphere goes to 160,000ft. You have to go above 50 miles (264,000ft) to be considered an astronaut, and atmospheric effects are noticeable at 400,000ft during reentry.
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Scramjets need an atmosphere (Score:5, Informative)
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Re: (Score:3, Informative)
Re:Scramjets need an atmosphere (Score:5, Informative)
Explaining the turbojet is easier after explaining the ramjet. Ramjet performance suffers below Mach 1 because you can't get enough compression for efficient combustion. The turbojet adds a compressor to add work to the flow so you can get the desired pressure ratio coming into the burner. Then you have to go through the turbine such that you can power the compressor.
Engines with compressors are far more interesting as they can be pushed to the point (whether by power setting or flight condition) such that the compressor can stall and flame will shoot out the front of the engine. It's something pretty important in compressor design since they operate with an adverse pressure gradient (pressure out > pressure in). This is why you see compressors with 10+ stages powered by only 1-2 turbine stages. It's really quite interesting.
You basic principle explanation isn't great for non-engineers. Try using "Suck, squeeze, bang, blow." I explained that to some friends of mine and they were way more interested. They not only laughed but they then wanted to hear more detail. But solid explanations on your part, I just wanted to nitpick a couple things since I'm a propulsion guy.
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Re: (Score:3, Interesting)
Reversal depends on the engine type (turbojet, turbofan, etc..) and the manufacturer. I've seen some information that one manufacturer blocks the bypass nozzle and redirects the flow out to reverse thrust. Pretty much, the fan still operates as usual but the bypass air is used and not the core flow (through the burner). It sounds like you have some mild confusion as to engine classes/terminology so I'll provide some details
Gah. Once more, with formatting (Score:5, Informative)
Pretty much all 3 are the same jet engine, more or less. A turbojet uses a compressor in the front to push the air into the engine. A ramjet relies on the fact that if you fly fast enough to start with, you get air pushed into the engine anyway. (Plus some clever design of the intake so the flame doesn't go in both directions.) But the air is slowed down to a subsonic speed at the point where the fuel is injected and lit. A scramjet is a ramjet where the air does flow at supersonic speed through the engine, so basically it's choked. You can add the fuel past the choke point and, since waves can't move backwards in a supersonic flow, whatever pressure you generate there by burning fuel can only go towards the back engine. The front of the engine can't "notice" the higher pressure in the back half because a pressure wave would have to travel through that air faster than sound speed, which isn't possible.
Another rough description would be that a scramjet is like a turbojet with an afterburner, only without the turbojet. (Sorta like the sound of one hand clapping, I guess;) Instead of having the turbojet push air through a nozzle and add extra fuel to it, the engine _is_ the nozzle and the airplane's existing speed is what pushes air to it. So you just add the fuel and light it. It's an afterburner without a turbojet.
Downside: a turbojet can start at zero speed, ramjets and scramjets need enough airspeed to start. Hence all these experiments involve booster rockets.
But in the end all 3 engines work by the same basic principle: air comes through the front, fuel is added, hot air comes out the back. No air, no flame, the engine stops.
The plans to use a scramjet to get to a highe enough orbit or even leave the planet, involve getting enough speed while still having enough air for the scramjet, or as boosters in addition to the normal rocket engines, or both.
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Re:Gah. Once more, with formatting (Score:5, Funny)
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Gah. Once more, with formatting (Score:5, Funny)
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HyShot, HyCAUSE and HiFire (Score:5, Informative)
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"First ever scramjet" ...? (Score:2, Informative)
http://en.wikipedia.org/wiki/Hyper-X [wikipedia.org]
Is there something I'm just not getting here?
Altitude of 330 miles??? (Score:2)
Re:Altitude of 330 miles??? (Score:5, Informative)
This is an experiment. Scramjets are still in the "data-gathering" phase, not the "let's make a realistic engine" phase, nor the "let's make a scramjet-powered craft" phase.
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Re: (Score:3, Informative)
Not only that, scramjets need an additional propulsion system in order to reach working speeds. Usually, yes, conventional rockets [wikipedia.org] are used. This is one of the major drawbacks in these type of designs.
Just ask CIA/Skunk works, area51 (Score:2)
Hell, they made the SR71 back in the old days, imagine what they have NOW!!!
They wont say ever!!! Stupid top secret morons, showing it off will not hamper anything. I bet Boeing just wants to make another $500billion to $1500 billion selling conventional aircraft for
the next 25 years, then they will bring online the new models later.
Good article at http://www.americanantigravity.com/documents/NASA- TM-2006-214547.pdf [americanantigravity.com]
"NASA Memo
Re: (Score:3, Interesting)
Dude, you can reach an altitude of 330 miles just fine with a perfectly low speed. There's nothing unphysical about it that requires the invocation of holy cows. It is also true that with the lack of a *horizontal* velocity of about mach 30 (at ~100km, you'd need less if you get as far as 330 miles high), you fall back down (well, not back to the same place, you may have traveled halfway around the w
Re: (Score:3, Insightful)
Oddly enough I was looking at a scramjet model at around this time in 1987. Subsequent revisions used less fuel and had other advantages - but while it's relatively cheap to do computer modelling and to build a shock tunnel to test these things at mach 8 on the ground it costs a lot to launch a rocket to get the higher speeds. It's not that surprising that it has taken over 20 years on a shoesting budget in a relatively small
Actually, it could be done (Score:3, Insightful)
That's actually one thing that makes scramjets tempting: the fact that it doesn't cap lower than that orbital velocity, and it can work with rather thin atmosphere too. So if you can go upwards at all with it, and modify the trajectory to have enough air for mor
Oxygen (Score:2)
Bzzzt. Wrong! (Score:5, Informative)
Scamjets use oxygen from the atmosphere as an oxydizer unlike traditional rocket engines which need to carry their oxydizer. Scramjets still need to carry fuel.
No. I am not a rocket scintist.
Re: (Score:2)
Not for me (Score:2)
</sarcasm>
Why was the altitude changed? (Score:5, Insightful)
So why was the summary changed by slashdot editors to the imperial unit?
Firstly, not everyone who reads this site is American, and secondly, this is an audience of nerds. I think we can handle kilometres! Even the USA's NASA is all metric now.
The scientists who developed this scramjet used metric, the country it was tested in used metric, the newspaper that reported it used metric, so how about we keep it that way?
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Re:Why was the altitude changed? (Score:5, Funny)
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Only old farts, MAINSTREAM idiots use MILES (Score:4, Insightful)
No self respecting scientist or nerd would ever use the word MILES in their own documents.
Slashdot is NOT mainstream, get back to being NERDY!!!
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Re: (Score:3, Funny)
Mostly just to piss people like you off.
Re:Why was the altitude changed? (Score:5, Informative)
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Re:Why was the altitude changed? (Score:5, Insightful)
Not to mention that the US has been butchering proper English spelling and grammar ever since Webster. Just switch to Metric measurements and the Celsius temperature scale already. The rest of the world is getting tired of having to convert measurements for the sole purposes of dealing with the US. [/troll]
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Suborbital trajectories? (Score:5, Interesting)
Off-topic, Ben Rich says in his book that the codename Aurora that everyone likes to think refers to some hypersonic aircraft, was actually the codename placed on the B-2 project as Lockheed and Northrop were competing for the contract. It's funny to think that to this day, folks still hang onto this and imagine some mythical hypersonic airplane. Which never existed. Or does it?
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Re: (Score:3, Informative)
Often, though, for simplicity sake, we use terms like "mach 10" to mean mach 10 at sea level
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Re:Suborbital trajectories? (Score:5, Insightful)
I wouldn't rule out the concept of hypersonic travel just because heat resistant materials are expensive today. If the rest of the tech is there and is affordable, and there is sufficient demand... who knows? The airline industry is bloody huge and there is lots of money to be made by faster travel, so it could draw a lot of R&D money if the other tech looks good.
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Re: (Score:3, Informative)
I think you're confusing the Dreamliner with the WhaleJet.... Dreamliner hasn't had any delays.
Military, not Civilian applications (Score:4, Insightful)
However since that does not excite public positively, they are instead fooling the public talking about civilian use.
What might be possible some day is to deliver a bomb from Sydney to London in very short time. Not human passangers.
The inherent heat problems are about 100 times easier to solve, if you imagine
the payload is 50kg of plutonium instead of 5000 kg of humans.
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Re: (Score:3, Interesting)
capable of using oxygen from air and not having to carry it,
is only an advantage over rocket-engines.
Jet engines already use oxygen from the air.
In civilian travel there is great need for fuel-efficiency.
If their biggest problem is excess heat,
it automatically means they are wasting huge amounts of fuel to create that heat.
Only military can afford this wasted fuel.
Also there is a huge problem in take-off and landing from ground.
Ramjet is not going t
Obligitory Spinal Tap joke: (Score:2)
This one goes to 11!
Okay, now my funny bone has been buried....
Kudos to these people. It may have only been for some seconds, but at least they are forging onward, and I salute their work!
Proving theory is usually no easy task, a working prototype seems to be 3/4 of the battle.
Seriously, hat's off!!!
330 miles is well beyond the Kármán line (Score:4, Informative)
Re:330 miles is well beyond the Kármán l (Score:5, Funny)
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Mach unit valid in space? (Score:2)
Re: (Score:3, Funny)
Re:Relativity in a Dark Place (Score:5, Funny)
Oh no
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SCRAM has been done, The real trick will be ... (Score:4, Insightful)
2 hours (Score:5, Funny)
330 miles ? (Score:3, Insightful)
Six seconds of flight (Score:3, Interesting)
Scramjets look good on paper. The thin air coming in is compressed by a series of standing shock waves. Unfortunately, the geometry of these shock waves can easily be upset by small distortions in the engine, which in turn can lead to changes in the stresses with in the engine, which - to cut a long story short - can mean the engine spectacularly demolishes itself when faced with real bits of atmosphere with unpredictable air currents. I found the flight time in...
http://www.abc.net.au/science/slab/hyshot/default. htm [abc.net.au]
It may not sound like much, but six seconds is very respectable for a scramjet. Yay!
There is a lot of touting about how this would get you from London to Sydney in 40 minutes and stuff. I am not sure how true or economical this is, even if scramjets can be made safe. When you are flying fast, you can either take your oxidant with you (as rockets do) or you can scoop it up as you go along. Scooping it up as you go along means taking in air that was initially at rest and getting to move at the speed the engine is currently going. As only 20% of the air is actually the oxygen you want, this is not necessarily an effective thing to do. It becomes most effective when the oxidant (oxygen) is a lot heavier than the reductant (fuel - and hydrogen is particularly light), so scooping it up as you go takes a lot off the take-off weight.
The other London to Sydney option is to get just beyond the atmosphere using a conventional rocket, then going ballistic and weightless for the main distance, and re-entering and gliding, a lot like the space shuttle. While being weightless is fun, being weightless for 20 minutes makes most people puke, so a large passenger jet might skip the atmosphere and retain a little gravity. A scramjet might be used for this.
Nevertheless, yay!