A Million Bucks, Mach 7.6, Straight Down

Dspiral writes "At the Canadian publication, The Globe and Mail, they write about the scramjet. A jet engine, with theoretical speeds over 8000 Kph, and pollution free!" Zero pollution because its fuel is hydrogen (a scramjet takes its oxygen from the air). The HyShot homepage is amazing; the beast has been built on a shoestring, barely over a million dollars Australian, and my favorite part is their planned test: "...shooting an engine into the atmosphere on a rocket, and hoping it will ignite as it plunges back down to Earth. Mr. Paull's speed objective is Mach 7.6, and the engine should ignite 23-35 kilometres off the ground."

Comments

This is old, and written by an idiot.

[Tau Zero]

Scramjet articles have been running around since the NASP and before. You can also tell that the author is a scientific illiterate, because he wrote the following:

But the Australian version of the engine, which will use the rush of air at high speeds to ignite pollution-free hydrogen...

Hydrogen is not inherently pollution-free; hydrogen combustion easily creates nitrogen oxides due to the high temperature. Nitrogen oxides are one of the catalyst chemicals which destroy ozone.

On top of that, the article is so short on facts (not even any links to more information in the article body - don't these nitwits understand what hypertext is about?) that it's hardly worth reading. News for nerds? I think not.
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Knowledge is power
Power corrupts
Study hard

The meaning of SCRAMJET

[evanbd]

Is more than "it operates above Mach 1"

It means that the combustion occurs above mach 1. A normal ramjet is quite capable of operation above mach 1. However, the incoming air is slowed down and pressurized before combustion. In a scramjet, the air is still moving at supersonic speeds relative to the combustion chamber and fuel injectors. I've seen trying to keep a hydrogen/gasoline/whatever flame alive in those conditions (at the qantities of fuel burned by standard jet engines and more) compared to keeping a candle lit in a hurricane. It's difficult. No, REALLY. The benefit of a scramjet is that it can operate at REALLY high speeds. A ramjet loses too much energy slowing the air down to work above about mach 3-5. The concept is *similar* but fundamentally different.

More Details

[maggard]

There's more then the Australian project, the USA's NASA has been working on this in-house for years. Originally the National Aerospace Plane (NASP) program it was retooled into the Hyper-X program when NASP proved to be infeasible; too many blue-sky ideas in one box, all stepping on each other's toes. Here are some Hyper-X links:

Overview:

Hypersonic Experimental Vehicle

More details:

Hyper-X Images on Dryden's Research Aircraft Photo Server Hyper-X Images on NASA Langley's LISAR Server Quicktime Movies: Hyper-X Launch and Flight Animation NASA Langley Research Center's Aerothermodynamics Branch

Now, before everyone goes getting all starry-eyed over this stuff there's a few caveats: There's a 20-30 year evolution period in civil aviation. This is not a plug-and-play technology. It won't bolt on to anything we've got flying now like a new turbo-prop might. It requires all new hardware from the airframe up. You'll likely to see this technology developed first for militaries then later adapted for civilian use. However it is likely that an unmanned "courier" version will be used before anything carrying folks for when it really-really "absolutely positively has to get there overnight" (or depending on locations even yesterday.) There are legitimate questions about how much material the upper atmosphere can absorb. Pumping out quantities of hot steam at high altitude may have a negative long-term impact. There's already a good deal of evidence that civil and military contrails lead to increased cloud-formation, what effects would be at even higher altitudes is not yet known. There's also the question of long-term economics: Will it really be cost-effective to build a craft with the various types of engines and structure and cooling required to get it to a height and altitude where these motors can operate to get around the planet in half to an eith the time it might take otherwise? Supersonic aircraft have yet to prove economically viable (the Concord only flies due to it's development being underwritten at great loss by the UK & France.) Next, yes these aircraft are a staple of many SF stories, we've all read them too thank you very much, no need to recite from your favorites (I hate when every freshman feels a need to relate every /. article to a Gibson et al story.) All of that aside this is really neat technology. I admit however I wonder where this material will land? Is there a nice rabbit warren the Aussies have picked out for ground-zero? Mmmm, impacted coney a la hydrogen flambé?

One problem with scramjets...

[hpa]

One problem with scramjets is that they must operate at or above some low-integer Mach number (usually 2-4). The "sc" stands for supersonic combustion. This, obviously, means that some other engine has to be used to bring it up to those speeds.

Conventional turbine engines can of course be used, but they don't really like getting all the way up into the scramjet operating range. Thus, there has been a lot of research into engines that can work both as ramjets (subsonic combustion) and scramjets (supersonic combustion). Whereas they would still need to be moving around Mach 1 before they can start operating, it means conventional engines would be used for less of the flight, OR that the use of rocket combustion (bring your own oxygen) for the initial part of the flight without a serious weight problem. After all, the whole point with this whole thing is to avoid the rocket weight problem of having to bring your own oxidizer and just use the O2 in the air. Since for an H2-fuelled engine the oxygen is 8/9 of the weight, the advantage is obvious.

(Did I mention that I really hate that Slashdot don't let you use <SUB> and <SUP>?!?)

Umm. hello?

[KFury]

Call me crazy (go ahead, do it) but I see a rocket going up really fast, turning over, coming down really fast in order to build up the speed to go down even faster (2 kilometers per second) and then it hits the ground (or whatever). Isn't anyone concerned about a system that has no uplink at all, using only internal instruments for navigation, with this kind of power? There's no way to turn it off once the launch pad umbilical is cut, and even if things go right, 2km/sec is faster than anything else I've ever seen hit the ground. Even the terminal velocity of meteors is often slower, because they aren't falling and pushing at the same time.

I'm worried, but I wanna see...

Kevin Fox
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As Chief Wiggum would say...

[JesseL]

"Thank God it landed in that smoking crater!"

This engine has no thrust..

[Blind RMS Groupie]

When I first read the post I thought "wow, this engine is going to propel this thing to mach 7.6 as it goes down!", but according to the article this is not the case. The engine is designed to provide readings that will help to calibrate supersonic wind tunnel tests and as such its optimal configuration for this purpose is one that doesn't produce any significant net thrust. Engines that produce thrust will come later.

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