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How We Might Have Scramjets Sooner than Expected
loralai writes "Recent breakthroughs in scramjet engines could mean two-hour flights from New York to Tokyo. This technology, decades in the making, could redefine our understanding of air travel and military encounters. 'To put things in context, the world's fastest jet, the Air Force's SR-71 Blackbird spy plane, set a speed record of Mach 3.3 in 1990 when it flew from Los Angeles to Washington, D.C., in just over an hour. That's about the limit for jet engines; the fastest fighter planes barely crack Mach 1.6. Scramjets, on the other hand, can theoretically fly as fast as Mach 15--nearly 10,000 mph.'"
I feel compelled to point out that's the unclassified speed record. Its actual top speed is still speculative.
Don't worry, between the security line, customs, delays, and waiting on the tarmac, you'll still be garunteed at least 10 hours at the airport for any trip.
I still have more fans than freaks. WTF is wrong with you people?
. . . and fusion power in 10 . . .
F-16 top speed at altitude: Mach 2+
F-22 top speed at altitude: Mach 2.42 (officially...it's reported it can exceed Mach 4)
F-18 top speed at altitude: Mach 1.8+
I actually couldn't find a modern jet fighter that COULDN'T exceed 1.6 (at least within my aforementioned 2 seconds of research)
Of course, that doesn't diminish the insanity of Mach-15, but still.
Oh yeah, if you turn, your heart will forcibly exit your body via your anus before exploding. Have fun.
Nobody expects the scramjet engine!
The enemies of Democracy are
The Concorde didn't have many routes because there was a NiMBY problem. Nobody wanted the plane flying out of their airports because of the sonic booms. Opposition to airport expansion is already bad as it is. I can't imagine how hard it will be to convince people to allow these scramjets on commercial flights, even if they were limited to trans-oceanic flights.
The incredible cost of fuel required to slam one of these puppies through the atmosphere is more than compensated for by the savings to the airline due to not having to serve more than one round of beverages.
Birds aren't usually a problem @ 100,000 feet ;-)
"False hope is why we'll never run out of natural resources!" - Lewis Black
1) Mach 3.3 speed record by SR-71 -> official speed record. NASA's X-15 set an unofficial one of Mach 6.7.
2) So.. 3.3 is NOWHERE NEAR the limit for jet engines.
Neither the SR-71 or the X-15 have conventional jet engines- the X-15 had a rocket and the SR-71 has ramjets
Well, I said fact-checking was *your* friend. Not mine. :P
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Maybe where YOU come from.
Does it make you happy you're so strange?
Huh?
MiG 29 - Mach 2.3
F-14 - Mach 2.5+
Kfir - Mach 2.3
JAS 39 Gripen - Mach 2.0
The original poster is grossly incorrect regarding the max speeds of current fighters. The venerable F-15 has a very achievable basic airframe limit of mach 2.5. It is rarely flown at that speeds for various reasons, however the engines and basic aircraft are quite capable of reaching that speed. One of the biggest limiting factors, as with all high speed aircraft, is heat buildup. Stuff simply starts melting when you get going that fast and sustain it.
Keep in mind that the mach 1.6 speed quoted is generally tied to the F-16, not the F-15, even though both aircraft use essentially the same engines. The difference is that the F-15 uses a complex variable geometry inlet design while the F-16 uses a fixed inlet. There are very good reasons why each aircraft uses one design or the other, but it has nothing to do with the available technology. It has to do mostly with how much cost we are willing to put up with in order to get the plane to perform up to requirements. The F-15, as our primary air superiority fighter, needed to be able to go very fast yet retain good performance at all speeds and altitudes. So the cost and weight penalty of a complex inlet design was warranted. The F-16 on the other hand, was designed from the start to be a lower cost multi-role fighter, and the cost and weight associated with a variable inlet was not justified by the performance requirements for that aircraft's role.
A similar tradeoff was made with the B-1 design. One of the big differences between the original B-1A design and the production B-1B design was the elimination of the costly and complex engine inlets that were needed to make the B-1 a high supersonic design. The B-1B has much simpler inlets and is therefore speed restricted below the original design specs.
Again, this has nothing to do with the available technology. Rather, it's the result of the basic truism that any speed freak knows, even in automotive racing, that going faster costs more. Almost any design can be pushed to a higher speed, but it's going to cost you and at some point you're throwing a whole lot of money to get marginal speed increases.
The original post's point that we haven't seen a breakthrough in this area in a long time is valid, but anyone following hypersonic technology research knows that in the last few years there have been multiple programs flying actual demonstration hardware with some success. The progress is fairly slow in part because this is considered low priority research since there simply isn't much firm demand for faster air-breathing vehicles (expecially ones that burn petrochemicals and therefore create more pollution than slower, more mature, and more efficient designs) however the research continues in the face of the harsh fact that speed is expensive.
Yes, infact I knew someone who use to fly those things and they weren't allowed to fully throttle up. He also said that during normal missions the plane would damage itself when going the faster speeds. Now of course this is all at someones word, so I have no written proof.
I heard the same thing from an SR-71 pilot, the damage was melting the nose and other leading edges. So advances in materials, not necessarily thrust, would presumably allow for greater speeds.
Never underestimate the bandwidth of a scramjet full of DVDs...
Real Daleks don't climb stairs - they level the building.
Gotta love the flight from City A to far-away City B comparisons. Except you need to be going Mach 3+ before Scramjets get past minimal stall speed, and the only way to get to Mach 3 right now is with a rocket-assisted takeoff. The neighbors around airports are going to love that, I'm sure.
I wonder if Scramjets would increase or decrease condensation trails, which are known to have a dimming and cooling effect on everything below them. Decreasing would mean more sunlight hitting the ground, but also more heat, which would only heat up the Earth at ground level that much more. If it increases, it means more cooling, but also more dimming.
Interesting times.
- A need to go that fast.
- An economic way to pay for it.
- A structure that can tolerate the heat.
- Engines that can run for a long time.
- A structure that can hold all the required fuel, and still have low drag.
As far as I know, if you want to go above Mach 2.X, you have to switch to titanium alloys as aluminum softens at about that amount of friction. Mucho $$$ and much bother in construction and maintenance.Also scramjet engines tend to burn out really quickly-- the temperatures you need in there are beyond the ability of most metals, at least for longevity.
There's a heck of a safety issue too-- scramjets can flame-out and are not easily restarted.
It's also a challenge to stuff as much fuel as you need into a low-drag airframe. You need long range as there's no point in short hops when it's going to take many kilomiles to get up to speed and altitude. But people don't like cramped cabins, so you need more fuel to allow a bigger fuselage.
Also it's going to be hard to find people willing to pay maybe 15 times the usual amount to get there a few hours faster.
Airships for non-time-critical journeys? That's a very intriguing idea. It reminds me of a paradigm shift I experienced recently.
My wife and I bought our first robot, a roomba naturally. We watched it intensely as it cleaned for the first hour. When it finished it docked itself to recharge. My wife then noted that there was still some fuzzies on the carpet and that it didn't seem to pick everything up. I told her that it would probably pick it up on its next run.
After a couple days of running the roomba when we would leave the house, the carpets suddenly are cleaner than they have ever been. So clean in fact that our allergies seem to have improved (probably placebo, but that roomba does pick up the dust).
I realized that our house cleaning robots don't work like the Jetsons led us to believe they would, where they clean the house 10 times faster; they in fact take 10 times as long. They are, however, 100 times more meticulous and therefore they clean the house 10 times as well. I think this is a paradigm shift.
Perhaps there is indeed similar benefits to be reaped from a similar shift in the transportation/aerospace sector.
Very thought-provoking.
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No one said we were. So what?
The increase in the price of oil may contribute to making alternatives feasible, but what that really means is that the number of hours of human labor that need to be exchanged for energy in any form will increase, which increases the cost of, pretty much, everything compared to labor.
No, it will be in lockstep with production; there aren't substantial stockpiles to draw down, and there isn't substantial use of stockpiled fuel, so consumption is pretty tightly chained to production.
Unlikely. The only reason demand (not consumption which is "quantity demand", a different thing from the demand curve) changes lag behind supply (not production, which is "quantity supplied") changes is that there are transition costs and barriers on the demand side. And that's what drives the price increases. Even as those are overcome, its more likely that demand approximately catches up to supply, dropping prices back from their peak to something like the prior levels with ongoing gradual increase than that things switch over and demand radically plummets.
The mother of a friend of mine was a top executive at Dow Chemical, at the time the company's highest-paid woman. She always flew Concorde when she could because the company was paying her salary during her flight.
Being able to get across the ocean with time left in the work day meant that Dow actually saved money paying for a Concorde ticket.
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I suppose that would depend on whether the collision occurred while overtaking the duck or head-on. In the first case, the duck's velocity would have to be subtracted from that of the airplane. In the latter, the velocities would be added.
Have gnu, will travel.
I work at a major university medical center, and we often take care of pilots (current and retired) with diseases/problems not handled by the base doctors.
All of them are calm like a brick, not even a flinch when told they had cancer.
"OK Doc, what do I do next?"
One of my senior partners who was a flight surgeon told me that that's what all the fighter pilots are like - almost unemotional, even when being shot down. All that stuff on TV, with the pilots screaming "WE'VE BEEN SHOT!!!! MAYDAY MAYDAY!!!" is not at all what these guys are like.
Yes, I guess the guy could calmly express that he wanted all the gays/commies/people who don't sweep their sidewalk killed, but I don't think that that type of thinking usually lends itself to calmly expressing those thoughts - they usually come at you like a shotgun.
..........FULL STOP.