New Jet Engine Tested

SpaceAdmiral writes "A revolutionary new jet engine has recently been tested in Australia. It is hoped that the engine, designed by UK defense firm QinetiQ and capable of Mach 7.6, will pave the way for ultra fast, intercontinental air travel. Scramjet (supersonic combustion ramjet) engines have no moving parts and take all of the oxygen they need (to burn hydrogen fuel) from the air, allowing for larger loads than rockets which must carry oxygen for fuel."

Comments

ALL of the oxygen?

[thirdrock]

Scramjet (supersonic combustion ramjet) engines have no moving parts and take all of the oxygen they need (to burn hydrogen fuel) from the air, allowing for larger loads than rockets which must carry oxygen for fuel.

All jet engines take the oxygen they need from the air. Only rocket engines leaving the atmosphere require an onboard source of oxygen. Even the U2, which flew at > 40,000ft got it's oxygen from the surrounding air.

And the Scramjet is a jet engine, not a rocket engine. The difference you were looking for is that scramjet engines do not require a turbine to compress the surrounding air. This allows the engine to move at a much faster speed because turbine engines have an upper speed limit before the stresses pull them apart.

Also, theoretically if the compression was high enough the scramjet could burn jet fuel (kerosene) but there is probably technical difficulties with injection (ie. avoiding hot spots and detonation).

Re:Flight Data: San Francisco to London

[Tyler Eaves]

Hardly. An acceleration of 0.25g, which you could barely feel, would get you from 0 to Mach 7 in about 15 minutes.

Re:Flight Data: San Francisco to London

[susano_otter]

since it doesn't have enough oxygen in the system below mach five for the oxidation of the fuel

This has always bothered me: If the jet must already be traveling at high speed to operate, then how does it get up to high speed in the first place?

pointlless travel

[Anonymous Coward]

Instead of getting people to consume more (faster) travel and burning up the ever decreasing oxygene of the atmosphere in the process, maybe the emphasis should be directed more on things like *reducing* the need for air travel? Just like instead of encouraging road travel, the opposite should be happening. Global warming, remember? Overly dependence on foreign oil etc?

Besides, when there were problems with making the Concorde profitable that flew at a mere mach 2, how in the hell is it going to be possible to create an aircraft that would be stable enough on ground level to take off and land, and still be profitable? The quantum leaps the material science has to make to meet such needs are huge.

Re:A solution in search of a problem.

[MeepMeep]

Furthermore - a scramjet is nearly useless as the first stage of an orbital launcher, because it wants to cruise at a steady speed. An orbital launcher wants to be steadily accelerating.

I'm no rocket scientist but I thought scramjets actually want to maintain a steady speed RELATIVE to the air density (i.e. in thinner air, it has to move faster).

Sure, if it was going HORIZONTALLY it would optimally maintain the same speed, but wouldn't the decreasing air density as one moved up in the atmosphere naturally cause the scramjet to "want" to go faster?

MeepMeep

A post in search of a reply

[jd]

ARLA - an alternative rocket launch assist system - uses a ramjet as the second "stage" (the first stage is given as a gas cannon, but a magnetic linear accelerator would work better for manned flight). They propose a rocket on top of the ramjet, but you could easily have a scramjet on the ramjet, then a rocket on top of that.

You don't need turbines to get a ramjet to sufficient speed. A ramjet will operate at 400mph - well within the limits of a propeller engine (I believe the Rolls Royce Merlin could manage over 500 in World War II). You simply fold the propellers inwards when the ramjet hits activation speeds.

You're also assuming ramjets are solely for Earth use. Let's say you want to have a flying aircraft operate on Titan. Nice, methane atmosphere. You're extremely limited in the weight you can lug over there, so the less you carry the better. In that case, you'd have an oxygen "fuel" and use your scramjet to pull in the methane. An electrical engine would be an alternative, but you'd have trouble keeping it hot enough to function. A glider would also be good, but you've no thermals of significance.

Back on Earth, a scramjet would be valuable in the event of an emergency. There's an island off the African coast, I believe, which - when (not if) it falls into the ocean, will create a tsunami capable of wiping out the entire eastern seaboard of the Americas for several hundred miles. There simply isn't any combination of aircraft, mass transit or shipping currently in existence capable of getting more than a small percent of people to safety.

The west coast is in as much danger from faultlines, volcanoes and other disaster-causing events, but it probably isn't going to be in danger at the same time.

Thus, a simple mechanism for ferrying massive numbers of people very rapidly from coast to coast would likely eliminate most of the potential for fatalities. True, this does mean that supersonic and hypersonic aircraft will need to fly over populated areas. Oh wah. The RAF do low-level supersonic flights in populated areas all the time. Hasn't killed me ye...ughhhh..

(Seriously, I'd rather have to worry about not getting much sleep during a disaster, if on an evacuation flightpath, than getting permanent sleep if living within a hundred miles of a coastline.)