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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."
Clickey-clickey
"A door is what a dog is perpetually on the wrong side of" - Ogden Nash
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?
Been there done that.
But they will get you through the most energy demanding part of the trip without having to carry the oxygen. It is as you observed though, to get "into orbit" a hypersonic space plane will need one final kick from a rocket carrying it's own oxygen. This is a far cry from the massive quantities of oxidizers currently carried to launch the shuttles, both in thier liquid fuel and mixed as a solid in the external boosters.
Basically, yes.
The thing about getting to orbit isn't so much the vertical velocity required, its your horizontal velocity. Rockets going to orbit don't go straight up; if they did they would end up coming straight back down... The trick is getting enough horizontal velocity so that as gravity pulls you down towards the earth you are moving fowards fast enough that you are continually "falling over the edge" of the horizon.
With a scramjet you only need half the fuel of a traditional rocket, as you burn oxygen from the atmosphere instead of carrying it all with you. Yes, a traditional rocket IS needed to get you out of the atmosphere, but using a scramjet for the initial acceleration would end up saving a lot of fuel, and hence weight.
The two biggest drivers for innovation and invention are the military and religion.
Look at all of the effort people have used to build pyramids and cathedrals - really wonders of their ages - and all in the name of religion.
Same with the military - People just don't put forth the effort required to make breakthroughs like this without some greater need (national protection or God).
A fine is a tax you pay for doing wrong and a tax is a fine you pay for doing all right.
I'm not sure whether you're high, or the History channel. The Messerschmitt 262 was the first warbird with jet engines, and had it entered the fray just a few months earlier, it might have changed the course of history. The jet engine was eminently useful in that application at that time.
Thinking outside my Head
Scramjets don't push through the air. They suck it in for combustion.
Horses were still the only practical means of getting around when the first steam engines were being developed. Times change. Technology improves. Chemical fuel rockets will one day be considered as archaic as steam engines.
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.
here you go....scramjet takes ship up..when the jet ceases combustion, rocket goes off and takes it into orbit.
the rocket can be small in this case since the scram jet is going fast enough that it could get enough oxygen from the atmosphere at very high altitudes to burn.
I am the Alpha and the Omega-3
Humans will not be free until they have stopped being afraid of death and the scare tactics used to control the weak religious minded, such as belief in heaven, hell, judgement day, etc. nothing good will happen. All are used as tools by the Leaders and Pontiffs to keep the masses in line.
Until the substitution of reason and thought for blind faith happens nothing will ever change.
But honor the 2 biggest killers of mankind - the military class and religion as advancers of society? Fuck, no. They are the biggest millstones around the human condition.
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.
Rockets only work better if you consider the mechanical efficiency.
Thank you, at least somebody recognizes that.
If you throw cost into the deal, rockets fall apart. They're disposable for the most part.
They don't have to be disposable. The X-15 was a fine example of a reusable rocket -- 199 flights for the 3 vehicles, several of them high enough to earn the pilots their astronaut wings. That was 40-50 year old technology. The DC-X was a great example of a reusable rocket that could take off from the ground and land under its own power.
-- Alastair
Scramjets don't push through the air. They suck it in for combustion.
ROFL!
That is just wrong on so many levels. You do realize, don't you, that it is impossible to suck air to a speed greater than Mach 1? (Well, unless you're sucking it into a huge vacuum chamber through a DeLaval nozzle, but only until the pressures equalize, and then only in the divergent section of the nozzle.)
Chemical fuel rockets will one day be considered as archaic as steam engines.
We all look forward to that day -- but air-breathing jets are no more advanced than rockets, and in fact they're rather Rube Goldbergish. Using jets and wings to get to space is equivalent to the "horseless carriage" era of automobiles -- or worse. It's like trying to come up with a 100MPH, 200 HP vehicle by inventing a harness that will let you hook up 200 actual horses, because they can "forage for themselves" rather than just building in a gas tank and engine.
-- Alastair
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
The big expense is reaching Mach-25 (roughly orital speed), not going 100 miles up. If the plain can reach mach-25, it'll be out of the atmosphere in a very short time, and only need a relatively small rocket impulse to put itself into a circular rather than atmosphere-re-entering-elliptical orbit. There are a lot of *engineering* hurdles to a spaceplane, but the physics is pretty compelling.
The Junkers Jumo 004 jet engine used in the Me-262 had an engine life of little more than 10 hours. The main problem was the low quality of the steel that was available to the manufacturer. See here for more details. The engine was marginally acceptable for wartime use.
Mea navis aericumbens anguillis abundat
That's not entirely correct. The O2 is a third of the mass. Keep in mind that in addition to eliminating the weight of the 02, scramjets push such an amazing amount of air out the back that they are far more efficient than rocket engines.
The main problem with space launches is the initial climb and acceleration, when you are pushing forward all of the craft's stages and fuel. By eliminating the 02, it translates into vastly, vastly smaller requirements.
Better to simply make the fuel and oxidizer tanks bigger (because fuel and oxidizer is -so- much a -tiny- part of a launch cost) and stick bigger engines on it.
Scramjets are far simpler than rocket engines. It would be much cheaper to build boosters that use a scramjet as a first stage as opposed to a rocket engine. The fuel savings, the increased payload, and the cheaper cost all make the scramjet a superior option.
If you don't understand any of my sayings, come to me in private and I shall take you in my German mouth.
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
So what were all those jets flying in the 50s? UFOs?
Both military and civilian jet aircraft were doing well in the 1950s.
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.)
-- Alastair
Don't forget that the hydrogen takes up a lot more volume, though, thus accounting for a greater proportion of the weight of non-fuel items like the storage tanks and other support structure. Still, the fuel's the main mass component, as you say.
Eh, I wouldn't say "we", just you. (Don't mean to be rude, but you really shouldn't try to speak for all us when you're really just expressing a personal opinion.) A (sc)ramjet has a combustion chamber just like any other fancy jet engine. Just like a rocket, it's energy injected by combustion which causes the air to expand which is directed out the back and gives you the thrust.
Whether or not the compressor is mechanical (as in a normal jet engine) or some funky aerodynamic thing (as in a (sc)ramjet) is immaterial (although the compressor stage in a modern turbofan jet engine increases the amount of thrust by moving a whole lot more air through a bypass besides just that generated in the combustion chamber--however, this just means the turbojet is more efficient, not that the (sc)ramjet doesn't work).
It basically boils down to the same thing that happens with rockets not having anything to "push" against... it's just an action/reaction thing. If you want a short answer, it "pushes" against the combustion chamber.
Same thing we launched all the first X planes with. For test flights you don't build a fully operational fighter jet. You test the engine in a small frame.
Two roads diverged in a wood, and I - I took the one the bus load of girls just went down.
That's not entirely correct. The O2 is a third of the mass.
...twice as many hydrogens as oxygen but
I'm not sure what relavence the % of Oxygen's mass is. The main point is that the mass doesn't matter if it is fuel/oxidizer mass. Typically you want -more- of it because it makes life so simple if you can have more powerful engines that consume it in large quantities.
--You are both wrong. In a Liquid Hydrogen/Liquid Oxygen rocket, 8 times as much oxygen mass is needed compared to hydrogen mass.
4H + O2 => 2H2O
Oxygen is 16 times more massive.
Rocket engines are -very- efficient, but of course they have to push their own oxidizer along.
--I dont know how you define efficiency but in my aproximation having to lift 20x the payload mass because of extra fuel is an inefficency.
Vastly smaller requirements for what? O2 which is amazingly cheap? Why bother?
--Going back to the previous point. Its not a matter of the price of oxygen, but the bulk that it causes to carry it. This results in hugely more complex lift vehical, which is... um... huge, and expensive.
You don't get very far up before you run out of oxygen to power a scramjet
--In fact it cant operate at low altituteds because there is too much oxygen.
scramjet... weighs quite a bit itself.
--Compared to fuel weight ???? Are you nutts ?
Sir, I dont think you understand this at all.
Im not here now... Im out KILLING pepperoni
A few?
In earlier history, virually the only reason for engineering was for military purposes.
Military:
Bronse processes
Iron processes
Steal processes
Basic Physics
Boats
Radio Communication advances
Planes
Atomic Physics
Rockets/Space vehicles
Satalites
Computers
The Internet
Religion:
Architecture
Printing Press
Mathematics
Im not here now... Im out KILLING pepperoni
The current thinking is so:
Use turbojet stage for takeoff.
Bring in Ramjet stage at transsonic speeds, transitioning to full ramjet about Mach 1.5 to Mach 2.
Bring in Scramjet stage from Mach 3-4, transitioning to full scramjet at Mach 5-7.
Bring in Rocket stage at mach 10-12, transitioning to full rocket at Mach 14-16.
You see, that it's rare that any single stage is purely one thing or the other. Scramjets are not the solution to space travel. They're one piece of the puzzle. Reducing the cost of flight to space by 5% is something which would still be worthwhile, and airbreathing flight certainly has great promise to do far more than that.
The problem is that at the moment it's only that: promise. These tests are to see if we can turn promise into reality.
It's hardly fair to say that religion has been the largest cause of death and misery across the world for all time.
You may be right, but to put another spin on the Iraq war:
Did Bush Say God Told Him To Go To War?
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
A railgun launch would be possible, but also has a lot of associated problems. You want a trajectory to orbit where the speed is increasing as the altitude is increasing (basically a constant Pitot pressure ascent). This means that the heat and pressure loads are basically constant over the flight. If you have a heat and pressure load peak, as will probably be caused by a high-speed rail launch, then you need extra structure and shielding, which will increase the flying weight of the vehicle.
Obviously there are a lot of people studying whether the trade off comes off positive or negative for the cost to orbit.
Here is a picture (rendering) of this X43.
Sure, the fuel has a positive ROI on its energy budget--but that's not the whole story. You also have to lift the tanks, insulation, and pumps.
You'll note that they accelerate the damn test article with a rocket.
Why is this a strike against scramjets? By definition, they only operate at supersonic speeds. If you're trying to prove the concept there's only a limited number of ways to get the engine up into that speed regime. Guess what--the Air Force isn't going to lend NASA an SR-71 so that they can blow it up when the test goes bad.
Designing a ramjet that can transition to scramjet operation would be a monumental accomplishment, but we're not there yet. NASA is doing the sensible thing by testing the engine that they've got--and consequently testing their engineering assumptions and theoretical models.
~Idarubicin
Ahem. That's what's called the stochiometric ratio, which is NOT used for rockets. Rockets burn very fuel rich; because (to oversimplify somewhat) the light, hot, hydrogen gives better thrust than the water (less places to hide the energy in simple molecules like hydrogen- rockets want the energy to go into kinetic energy of the molecules rather than internal vibration modes of the molecules).
The upshot is that rockets typically run with about 2/3 by mass of the propellent oxygen, with the rest made up of the fuel.
IRC This translates in the case of Apollo as 6 moles of hydrogen per mole of oxygen- but 8 gives a higher exhaust velocity, but hydrogen tanks are too heavy so the *vehicle* optimises at a lower ratio.
I dont know how you define efficiency but in my aproximation having to lift 20x the payload mass because of extra fuel is an inefficency.
It's so not as simple as that though- scramjets suffer from incredible heating effects from going mach 8 in the atmosphere, they suffer enormous drag effects, they end up using more *fuel* (as opposed to propellent), and the scramjet engine is bigger and heavier than a rocket engine for the same payload- furthermore engines cost money, whereas LOX and LOX tanks don't. (Fuel is pretty cheap too in fact).
This results in hugely more complex lift vehical, which is... um... huge, and expensive.
No. Perversely perhaps, it's bigger, but cheaper; because 60% of the mass is LOX, and the rocket engines are smaller and cheaper.
-WolfWithoutAClause
"Gravity is only a theory, not a fact!"the incoming flow is compressed within the scramjet combustion chamber by the slight taper.
Lighting one off is a problem, once it's running the combustion process itself tend to push back against the incoming flow to provide additional compression and make combustion more efficient.
The balance between incoming flow, compression from the taper and compression from the combustion process itself is difficult to maintain across a broad speed range without adaptive sections within the engine.
Oxygen has an atomic weight of 8, Hydrogen 1.
Oxygen has an atomic number of eight - and an atomic weight of 15.9994 - against Hydrogen, atomic weight 1.00794.
-Chris