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NASA to Attempt Mach 10 Flight Next Week
Dirak writes "NASA intends to break its own aircraft-speed record for the second time this year by flying X43a scramjet ten times faster than sound. On November 15 the X-43A supersonic-combustion ramjet - or scramjet - will again take to the skies aiming for Mach 10."
I'm tired of hearing people yap about tax money when they waste money on frivolous things. Not to say that video games are bad, but do you know how much health care or education $125 Million will purchase? And the general public dropped that in one day! Do you know how much good research $125 M will purchase? I haven't looked it up, but I'm guessing the X-43A project is on the same order of magnitude cost-wise as what the public spent on this one single video game.
"There are a dozen opinions on a matter until you know the truth. Then there is only one." - CS Lewis (paraprhase)
From the article:
The final flight in the Hyper-X program is scheduled to take place in October, when another X-43A aircraft will attempt to fly at Mach 10 -- ten times the speed of sound -- or 7,200 mph.
So if 10x the speed of sound is 7,200 mph, then the speed of sound is roughly 720 mph.
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I think there is little to no interest in this as far as combat aircraft. NASA's main interest is in using scramjets to produce aircraft like vehicles that can "fly" into space affordably. As I understand it aside from their ability to operate at high speeds more efficiently than rockets, they also allow for much higher altitude functionality than a standard jet engine. This would allow a space plane to get high in the atmosphere, then use a small rocket boost to get into orbit.
I believe the idea behind a functional vehicle would be something like a standard jet engine getting a craft up to mach 1 or 2, then a ramjet taking over and getting a craft up to mach 5 or so, and then a scramjet taking a ship up to mach 10-15, at which point a rocket boost pushes it through the last bit of thin atmosphere into orbit. I may be wrong, as my knowledge on this was material read 4-5 years ago, but that seems to be what I remember.
Supposedly a nother great thing about scramjets is their simplicity, very few moving parts, which allows for high reliability. Or as high reliability as can be expected for something working under the strain of Mach 10.
It's a record for an air-breathing engine. The SS get's lofted into orbit by self-contained solid rocket boosters that carry fuel and oxidizer together and burn it without air and then drops out of orbit. An air-breathing engine carries fuel with it and adds that to the surrounding air and pushes it all through it's combustion chamber.
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Just like 1 Atmosphere is air pressure at sea level, Mach 1 is the speed of sound at sea level.
Interestingly enough, according to Google Math, Mach 10 is ~127 miles a minute. Assuming it takes them at least 5 or 10 minutes to achieve Mach 10 (I have no frigging idea), they are going to cover some serious distance. Sheesh.
At Mach 10, you will circle the Earth in under 200 minutes.
Damn I love Google math.
The speed of sound in a gas is related to the temperature of the gas and the gas properties molecular weight and heat capacity (cp/cv).
The relationship is:
c = sqrt(j * R * T / M)
where:
c = speed of sound
j = ratio of heat capacity (cp/cv)
R = Universal gas constant
T = Temperature (for gases always use absolute temperature)
M = Molecular weight
The Mach number is the ratio of the speed of an object over the speed of sound of the medium that the object is moving trough.
The X-43A will be released at 40,000 ft and climb to 110,000. I am not very sure about the temperature at this altitude but I think is about -100 C or 173K. At that temperature speed of sound is:
264 m/sec
So Mach 10 would be:
2640 m/sec or 5900 mph
If X-43 could fly that fast lets say at, 1000 ft, mach 10 would be about 3400 m/s or 7600 mph. Unfortunately the air density at 1000 ft would not allow X-43 to go that fast.
Mach "speed" is expressed as a ratio and is usually relative to the local environment. You can increase your Mach ratio either by climbing at a constant absolute speed or by accelerating at a constant altitude (although climbing at an increasing absolute speed works best :-P).
The problem with using altitude to improve your Mach ratio is that it decreases your indicated airspeed (the air felt by the wings). There comes a certain point with some high-performance aircraft where the indicated airspeed is just above stall and the Mach ratio is just below the aircraft's design limit. This is called the "coffin corner" because once you reach that speed/altitude it's virtually impossible to descend or slow down without losing control of (or destroying) the aircraft.
Rutan's Space Ship One solved this problem by intentionally stalling the aircraft in a stable high-drag attitude and staying in that configuration until safely back into the flight envelope.