Slashdot Mirror
Second Hypersonic X43 Scramjet Ready for Testing
Dan writes "I am sure most of you remember how NASA was forced destroy their first hypersonic X43 seconds in it's maiden flight, which was a big setback for the american hypersonic scramjet program. Well NASA just finished one of the final tests and is preparing to launch it as early as February 21! I wish them the best."
Comment removed based on user account deletion
Happy Trails,
Erick
http://www.busyweather.com/
I think scramjets are really the solution to low cost travel, including to low-earth orbit and space. I only hope that travel with scramjets will not end up going the way of the Concorde...
...though I bet Bush will fund it so he can land one on an aircraft carrier!! *rimshot*
webpage
This is great technology, but remember, it's not for *us*, it's for the military. Faster jets, bigger killing radius, when will this benefit freedom and peace?
"Who are in control, they are not in control of anything - they don't even control themselves!" - Glen Beck
Looks like they were forced to destroy their server on its maiden Slashdot voyage.
I don't know for you, but I find manned high speed flights (X1, X15) much more exciting to witness from a human perspective than those remote-controlled ones. I realize the objective is to test an engine and that there's no need to put a human being in danger to achieve that anymore, but it doesn't produce heroic stories and certainly doesn't make children dream like it used to.
I find the old crappy 1969 b/w pictures of the first man on the moon much more appealing than the Spirit panoramas, yet the probe went much further than Armstrong, and probably did a lot more science. But still, it's not the same thing, and NASA should send actually people up-diddly-up instead of drones, just because (1) there would be volunteers and (2) they would strike the public's imagination and generate sympathy for that kind of research, which in turn would turn into funding...
"A door is what a dog is perpetually on the wrong side of" - Ogden Nash
...as a scramjet takes in the oxygen it needs for combustion (whereas solid rocket boosters hold the oxygen as part of their solid fuel). Would they use the scramjet to get to such a high speed (at altitudes where there is still oxygen available) that you break free from the earths gravitational pull?
I am NaN
Clickey-clickey
"A door is what a dog is perpetually on the wrong side of" - Ogden Nash
For the several earlier posters who seem to think that this is the Holy Grail of Earth-to-orbit transportation -- well, maybe they're right in that it's about equally unattainable. Rockets work a hell of a lot better - as has been demonstrated by almost 47 years of orbital flight.
Any airbreathing technology suffers a couple of fundamental flaws when it comes to suborbital, let alone orbital, transport. Most obvious, the air is mighty thin up there -- so you've got to stay where the air is thicker to support combustion. (Which basically means you can't make orbit with out at least some kind of apogee kick rocket).
Secondly, pushing through all that air creates drag. Now, you either aggravate the problem by slowing the relative airspeed enough to support combustion -- meaning increasing the drag on that air (supersonic combustion alleviates this somewhat), or you don't slow it down (relatively, actually you're speeding the air up), have a harder time maintaining combustion, and more significantly, have a much lower momentum delta in the exhaust -- meaning less push to the vehicle.
Scramjets have some limited use for high speed short range flight but rockets are far more efficient and the only practical way to get to orbit.
(And while I may not be a rocket scientist, I've had long talks about just this with some very expert rocket scientists, such as Max Hunter.)
-- Alastair
this will be THE means to get to a station in Earth orbit, and from there, nuclear rockets out into the farther reaches of the solar system. I'd love to see colonies on Mars as much as the next geek, but until we get it through our heads that we need to have stepping stones along the way, we aren't going to be successful. It is simply too damn expensive to develop an entirely new system for every "space objective". We need a new way into Earth orbit... and a space station whose primary objective is to be a way station where deep space nuclear propulsion systems can launch for the rest of the solar system without contaminating the environment here on earth. Maybe someday materials science will make possible the space elevator (and it may be closer than I think, but until they're spinning line, I'm not counting on it....) but until then, we need a different solution beyond out brute force approach. This could be the technology that opens up just these sorts of possibilities.
Supersonic is Mach 1.0 to 4.9, Hypersonic is Mach 5.0+. I'm not an aerospace engineer, but I vaguely remember an article in Popular Science that talked about how over Mach 4, the airflow through the engine would disrupt combustion.
Have you been touched by his noodly appendage?
Fucking space terrorists. Thank God we're being proactive with this looming threat.
Hammer of Truth
Scramjets combust the air at supersonic velocities rather than diffusing it prior to combustion the way most other engines in supersonic vehicles do. There's a lot of promise here. But in a society that can't make the Concorde profitable, will it be worth it in the end? I'd love to be able to fly to the other side of the world in something less than 24 hours. The economics of the situation seem to be against us, though.
"You can never have too many elephants on your team."
Been there done that.
The liquid fueled rockets that nasa uses today use liquid hydrogen and liquid oxygen in the reaction:
2 H2 + O2 -> 2 H2O
Which means that by mass modern rockets use about 8 times as much oxygen as they use hydrogen.
red rocket, Red Rocket, RED ROCKET, Red Rocket!!!
at that speed air becomes very different due to frictional heating. the aerodynamics are also somewhat different than supersonic flight which are much different than subsonic.
the main problems are heat though. the SR-71 flew around mach 3 and heat was its biggest enemy. also keeping the engines going at that speed was a challenge - few jet engines operate with those air speeds without self destructing.
-
This one, IIRC, is built for use by Halliburton to deliver water to Iraq.
It's all no-bid, hush-hush, very patriotic and stuff.
A feeling of having made the same mistake before: Deja Foobar
I work for the Air Force, everything I do goes into this mad, mad machine. It pays my bills, but in a way it is like a drug. I work with the best technology, but as much as I love the toys, I hate the end. I guess that makes me a whore. I accept it, but I don't like it.
"Who are in control, they are not in control of anything - they don't even control themselves!" - Glen Beck
So, why carry the oxygen, why not get oxygen from the air? For LH2-LO2, that eliminates most of the mass and solves the mass fraction problem right away. The 1960's Aerospaceplane project originally considered liquifying the O2 from the air -- careful tweaking can be enriched on LO2 over LN2 on account of boiling point differences. You used (boiled off) some of your LH2 to get the coolant.
The trouble with LACE (liquid air cycle engine) is that you have to slow down the air rushing into the inlet (or speed it up to your rushing vehicle). If you are going fast enough relative to orbital velocity, slowing the O2 down in the inlet will heat it so much that you cannot burn it with H2 and get any energy -- the stagnation temperature of the shock front gets higher than your flame temperature. Hey, if this were not the case, orbital velocity would be low compared to rocket exhaust velocity and mass fraction would not be a problem.
Ah, the scramjet, and scramjet was also considered for Aerospaceplane. It is literally the taking a drink from a fire hose. You only slow down the inlet air stream a little bit so you get some compression, and burn H2 in that hypersonic air blast and 1) hope that the flame doesn't blow out and 2) hope that you get any positive net thrust out of the works.
If you could get any single-stage-to-orbit vehicle built that had reasonable engineering margins, you could fly it like an airplane, and even if it had a very small payload, you could fly it often enough to make a profit. NASA blew a wad in the late 80's, early 90's with National Aero Space Plane (NASP) and pulled the plug. But forget the scramjet -- if you could build a rocket out of composite materials, you could get the mass fraction. NASA blew a wad in the late 90's on the X-33 and then pulled the plug.
Jerry Pournelle states that the Strategic Defense Office (which needed a way to loft Star Wars into orbit) could have done the job -- the DC-X demonstrated the control of vertical-takeoff vertical-landing (lands tail first on rocket flames just like in Buck Rogers -- maybe not so wasteful of fuel because reentry is mainly aerobraking and landing is to last applying the brakes on a mainly empty vehicle), and he talks about a program called Have Region (don't know the source of Air Force code names, although NASA these days seems to have projects code named Have Boner) that proved that the mass fraction target was achievable and one didn't need scramjets.
... because scramjets don't work at subsonic speeds, you'd need something BEFORE the scramjets to get to mach, what, 7.
I'm sorry, i'm not seeing this as a solution to the cost of space travel at all.
Does anyone else think that the X43 looks like a death star? Am I going crazy or have I been hanging around the Comp Sci labs too much?
in girum imus nocte et consumimur igni
This is only relevant for scramjets that use hydrogen as a fuel. If there were a scramjet which used jet fuel B, then that type of savings would be much smaller.
However, the X-43A vehicle does indeed use hydrogen for its fuel. (Perhaps for that very reason?)
Whoever modded this as interesting knows even less about physics and aerospace technology than did the writer. The heat generated by friction at high speed is an issue that must be addressed, but while there will be drag it's not going to rip anything apart unless it's not designed properly in the first place. That's one of the things wind tunnels and computer modeling help deal with long before a model is test-flown.
The SR-71's fusalage expanded from heat, true. The material is going to have to deal with heat, true. The NASA shuttle deals with the heat of mach 25 on re-entry, and it is not torn apart by drag unless something goes wrong, but the same happens when a commecial airliner gets seriously out of shape in-flight. Like the one that lost its rudder over Long Island Sound a couple years ago.
The stealth bomber (B-2) is subsonic. Carbon fiber is used due to its strength-to-weight and radio-frequency transparency, not heat resistance. I would be looking at exotic metal alloys, metal composites, ceramics (which is what the space shuttle tiles are) and use of circulating fuel for cooling of critical areas. The flight profile for a long duration hypersonic craft would probably involve extended flight at altitudes where drag is less of an issue, further reducing friction heating.
To hear the gods laugh tell them your plans.
A very large portion of the overall mass (and price) of current space transport is just the fuel to get out of the atmosphere.
A perfect statement of one of the most persistent and erroneous misconceptions in astronautics. Price it out: rockets typically burn on the order of 200kg fuel to put a kg payload into orbit (double this for manned, halve it for simplest payloads). LOX is around $0.16 (USD)/kg and kerosene around $0.40 (USD)/kg. Burning 2.5:1, you pay $0.22/kg fuel, or $45 per kg into orbit. Now add tankage, engines/motors (hella pricey, used once and tossed or essentially rebuilt), systems integration, logistics, infrastructure, admin overhead, and you get ~$9,000/kg delivered. Fuel is only 0.5% of the total cost. It is left as an exercise to the reader to figure out why our space program is so inefficient.
To recap this week's lesson for rocket scientists and voters: know some numbers before throwing your weight behind multibillion USD expenditures.
Sources: astronautix.com; Wertz, Space Mission Analysis and Design, 2nd ed., Microcosm: 1992, p. 731.
There's an interesting write-up on the SR-71 here which talks about the thermal expansion problems. Choice quote - "It was discovered during a Lockheed Skunk Works study to see how much money and development it would take to get the SR to go faster than it's designed top speed (mach 3.2-3.5) that the metal divider between the windshield was heating up so much above mach 3.5 that it was affecting the integrity of the windshield, and at that point they had stretched the glass technology to the maximum."
One of these days I'm moving to Theory - everything works there
I understand that supersonic combustion is a neat trick, basically the flamefront has to keep up with the aircraft as it moves through the air. Since normally a flamefront is limited in its speed by the speed with which the molecules can contact each other and thus react chemically, getting that flamefront to keep up with the aircraft involves getting the local pressure high enough that molecules can bump together at "supersonic" speed (I doubt it is actually supersonic in the region and under the temperature/pressure conditions of the combustion).
But how does one exert pressure against something that is not there? Imagine the classic balloon we blow up and then release. The pressure differential between the front of the ballon and the area where the air is escaping causes the balloon to move. Pop the balloon with a pin and it goes nowhere, because the pressure is released everywhere at once. A ramjet compresses purely from the ramming of air into the combustion pipe. Without a compressor against which to enclose the combusting mixture, how is thrust generated?
Something I'm missing. We know it works, we've seen it. It just doesn't make sense yet.
To hear the gods laugh tell them your plans.
Scramjet technology began around the 1950's. It has been since the 1970's research in to plasma torches in supersonic flows. The plasma torch servers as an igniter and combustion enhancer. Plasma torches offer a couple of advanrages. The plasma torch servers as an ignition source for the fuel and combustion enhancing radicals produced by the plasma torch.
Scramjets also use the hypersonic shock wave for compression. A high compression "point" is where the forebody and engine fence shock waves cross. One of the problems faced it is how to design the inlets to maximise the compression. To keep things simple many scramjet engines are designed as 2D engines.
Designs my attempt to use air stream swirl to enhance fuel and oxidizing air mixing.
For more details please see http://citeseer.nj.nec.com/cache/papers/cs/3623/ft p:zSzzSztechreports.larc.nasa.govzSzpubzSztechrepo rtszSzlarczSz1998zSzaiaazSzNASA-aiaa-98-2506.pdf/r ogers98experimental.pdf
I am an vegan and my Ike you is
Wat was the queschin?
Those who sacrifice security to condemn liberty deserve to repeat history or something. - Benjamin Santayana
Sure, there is a modest up-front cost, but once it's built, transportation to geo, HEO, and beyond will be relatively inexpensive.
It may sound unfeasible at the present time, but the US congress is funding research on it.
Those who sacrifice security to condemn liberty deserve to repeat history or something. - Benjamin Santayana
And as for the Nazis developing the first jet engine, Sir Frank Whittle might have an argument with that. (Although the Germans may have had a jet -powered aircraft in the air first.) :)
IIRC, according to "Inventions that changed the world", Whittle patented his jet engine quite early on (I think before he'd built a working version) which meant that it became public knowledge.
It's quite possible that the Nazis saw this patent and, of course, probably didn't feel the need to pay any licencing fees for their development
I think these names are cool, but these names for the electronic warriors are very different from the more macho names for the gun and bomb warriors.
Nope. That's the stochiometric ratio, nothing like that is ever used. Actually it's more like:
4 H2 + O2 -> 2H20 + 2 H2
(Actually, it's much messier than that, you really get a bunch of HO's O's H's H2O2's but that's the gist of it).
The point is rockets run very fuel rich, because that gives a much higher exhaust velocity (the hydrogen has less places to hide energy than complex molecules- you want as much energy as possible to be in kinetic form), the scramjet would do the same thing. So your fuel/oxidiser ratio is way off.
-WolfWithoutAClause
"Gravity is only a theory, not a fact!"