Scramjet Test Successful

An Anonymous Coward writes: "The Sacramento Bee is running this story about the first powered device to achieve "hypersonic" speeds in the Earth's atmosphere. In a series of DARPA-sponsored tests, at Arnold Air Force Base in Tennessee, a scramjet engine, encased in a titanium projectile, was fired from a 130-foot cannon, at an initial velocity of Mach 7.1. The scramjet's engines then ignited, and the object moved another 260 feet, in just 30 milliseconds, before it came to rest in a series of steel plates designed to halt the flight. Peak acceleration: about 10,000 G's. Elapsed time, including cigarettes & pillowtalk: less than a second. PS: According to this nifty page at NASA, Mach 7.1 is about 5406 MPH, whereas 260 ft, per 0.03 seconds, is about 5909 MPH."

Comments

I can see my first flight on one these babies now

[case_igl]

Ladies and gentlemen, welcome aboard LotsaCashSpentDevelopingThis Airways.

Flight Attendant #1:
"Once we reach our cruising altitude we will begin our complimentary beverage service. Coke products are free while beer, wine, and liquor may be purchased for..."

(interrupted by Flight Attendant #2):

"LotsaCashSpentDevelopingThis Airways welcomes you to Paris DeGaulle Airport. The local time is 12:14pm."

intended use

[rneches]

The idea behind these sorts of technologies (scramjets and ramjets) is to fly very efficently, especially in the higher atmosphear. The technology to beat, in this case, is non-air breathing propultion (a.k.a. rockets). Because scramjets are air breathing, it is not neccesary to bring along an oxidizer, allowing for considerable weight savings.

Because of this, scramjets are critical for efficent, practical single-stage-to-orbit vehicles. The idea is that you operate in scramjet mode until the atmosphear thins out too much to sustain combustion, and then you start adding your own oxidizer. This will effectively turn the engine into a rocket motor. With scramjets, you could build a shuttle that would actually be fairly inexpensive to operate. Also, since the most expensive part of any mission is boosting into low earth orbit, any savings in the first stages of flight would dramatically bring down to costs for any mission, but especially heavy ones (like a manned mission to Mars).

The other reason to develop scramjets is for their raw efficenty. The use fuel at a fantastic rate, but at Mach 7, the fuel per unit distance is exceedingly good. Instead of supersonic (in this case hypersonic) flight being a luxury reserved for Concorde flyers, it would become the cheap, practical way of getting around. Of course, it would only make sense for the really long flights (like Chicago to Sidny), but the implications could be trans-global flights that cost less than regional flights.

Scramjets are very, very cool, and not just because they go fast.

Re:intended use

[gizmo_mathboy]

While the thought of having a hypersonic commercial vehicle is enticing, I think the intended use of scramjets are more for the military than anything. Remember this is a DARPA project. There isn't many DARPA projects that made it into the commercial realm. Well, I can think of at least one. ;-)

Heck, just a hypersonic projectile and/or missile would really change the landscape for Ballistic Missle Defense. Having a velocity several times faster than your target is a major advantage.

It wasn't mentioned in the article but the projectile used gaseous ethylene at 1000 psi, not hydgrogen, as its fuel. I love my Aviation Week subscription. :-)

As mentioned in another posting hydrogen embrittlement would be a concern in a larger vehicle, this is a 20% scale model. The biggest barrier is heating. Atmospheric heating is a big deal at Mach 7+.

A more detailed article can be found here at Aviation Weeks online site.

The cannon is more interesting

[redelm]

I can see how this short test worked, and how they can get some scramjet performace data in the 30 ms of free flight. Ain't microelectronics wonderful?

But frankly, I'm more interested in that super cannon. Mach 7.1 is 7,500 ft/s (2,300 m/s) which is extremely high. It would have a max range (neglecting aerodrag) of 300 miles! Did they use a gas-gun?

Re:The cannon is more interesting

[KFury]

Sorry, there's a big difference between 'sending things into outer space' and 'achieving escape velocity.' The first simply means it could shoot something outside the atmosphere, or around 90 miles up. Having reached outer space, it can fall back down to Earth.

Reaching escape veolcity means that, ignoring aerodynamic drag while departing the atmosphere, the object has enough velocity to fully escape Earth's gravity well, so that it'll never come back. This is a couple orders of magnitude faster.

As for the replies to the post talking about sending things into orbit, that presents a different problem, because you couldn't stabilize an orbit without a burn at the apogee of the flight, to stabilize the flight path from a parabola, which would come back and slam into the earth, to a circular or elliptical orbit. So in addition to having to protect the electronics from the tremendous G-forces (or making it all out of a ferrous metal, so you can pile it through a railgun and not have to worry about it because every piece of the craft is being accellerated identically) you also have to put in enough fuel and an engine to make that stabilizing burn. Of course, ferrous fuel is hard to find...

stupid question?

[Marcus Brody]

From the article:


Scramjets, or supersonic combustion ramjets, burn hydrocarbon fuel but scoop oxygen out of the atmosphere to combust it....


...The Pentagon and National Aeronautics and Space Administration are both studying scramjet technology since it would allow missiles or spacecraft to travel longer distances and carry larger payloads than rockets.

I'm sure i'm missing something fundamental here, but where the hell are spacecrafts supposed to get the oxygen from?
I guess they must just mean using scramjet untill leaving the atmosphere, and then use onboard oxygen, but it is a little misleading

Re:stupid question?

[maggard]

Missiles and spacecraft are launched from down here at the bottom of the soup. If they can take advantage of the ambient gasses along the way (up, down, sideways) as an oxidizer then there's that much less material they have to lug along. Yes once in space a Scramjet isn't much use but to and from arbitrary "space" the majority of most trajectories are within enough atmosphere that Scramjets would be useful.

Imagine if your car/bus had to haul along it's own oxidizer in a honking big tank of super-cooled special-purpose gas next to the fuel tank, which is what all liquid-fuel rockets do today. Now imagine someone announced an engine that could possibly dispense with that heavy complex oxidizer tank that's been weighing down your car/bus and instead let the motor just suck in outside air - pretty exciting news eh?

Right now Scramjets are a tricky exotic tech requiring special materials and designs that push the envelopes for those fields. On the other hand the same was true for jet engines when they were developed yet all large and/or long distance aircraft use them pretty much exclusively today. This may be a technological blind alley or it may never be commercially viable but it's interesting stuff nonetheless, indeed exciting for the aerospace-heads.