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.