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NASA Provides Results Of Scramjet Test
Guinnessy writes "Last March, NASA carried out the world's first test flight of a scramjet-powered aircraft. The Industrial Physicist has the latest results from this test. According to the article scramjet-powered missiles and aircraft could be in mass production as early as 2010. This piece is also a good introduction for those unfamilar with scramjet technology."
Any aerospace engineers in the know want to comment?
Well, I am not an expert in reentry, but I'll take a crack at your question. I think the important thing is not maximum heating, but rather some integral of heating over time. If the shuttle or other vehicle entered more gradually, it may be that it would actually reach a higher temperature because it would have more time to soak up the heat from the plasma around it. No matter how well you insulate something, eventually it has to reach practically the same temperature as its surroundings. You hope to get on the ground long before that happens.
Wings are heavy and delicate, and it would be hard to imagine that they could be large enough to significantly lift the craft at high altitude and lower speed and still survive the heating. (The heavier the wings are, the more kinetic energy you need to dissipate to slow down--and the more heating you get.) IMHO wings are a dumb thing to carry into space with you. Lifting bodies are better.
Is it possible to build a craft that can use wing lift all the way up to LEO?
.1:1 to keep accelerating.
Maybe.
In a real gas, aerodynamic lift is always accompanied by aerodynamic drag, and the ratio of the two is not dependent upon density or pressure or altitude. Until the point at which you actually achieve orbit, if you are relying upon aerodynamic lift to keep you in the sky, there's a certain amount of drag you have to overcome just to keep accelerating, and you can't make that problem go away by playing with the altitude.
The absolute best hypersonic lifting body designs anyone's been able to come up with, even theoretically on paper, have lift:drag ratios on the order of 10:1, so you need a thrust:weight ratio of at least
Not exactly, it was carried atop a regular airplay at several hundred miles per hour, then the rocket booster kicked it up to the cruising altitude and THEN the scramjet engine was engaged for the 10 second burn.
It's damned impressive but it's not like it accellerated to 5000 mph from a standstill.
LK
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Nearly everyone in the world (including the richest and poorest areas) has benefited greatly from all the satellites we use for communications. They were made possible by technological spinoffs from all the rocketry programs.
That is about 23 Gs. MAYBE a human could survive it, for a mere 10 seconds, with proper cushioning. No way in hell a human could be piloting it at that acceleration.
From the article:
The supersonic combustion ramjet, or scramjet, uses no rotating parts. In a conventional ramjet, the incoming supersonic airflow is slowed to subsonic speeds by multiple shock waves, created by back-pressuring the engine. Fuel is added to the subsonic airflow, the mixture combusts, and exhaust gases accelerate through a narrow throat, or mechanical choke, to supersonic speeds. By contrast, the airflow in a pure scramjet remains supersonic throughout the combustion process and does not require a choking mechanism, which provides optimal performance over a wider operating range of Mach numbers. Modern scramjet engines can function as both a ramjet and scramjet and seamlessly make the transition between the two.
Get the pdf version here
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However, how much lift does it actually get? Is it possible to build a craft that can use wing lift all the way up to LEO? If so, could it then be possible to obtain a flight envelope on the way back down?
This depends entirely in how you define leo. In order to reach what is generally considered space (100km+) you will be outside 99% of the atmosphere. This means that the atmospheric density is extremely low. So low that the normal rules of fluid mechanics are invalid and you have to treat air as a rarified gas. This is statistics based rather than standard calculus based. The extremely low density effectively means that lift from the wings/lifting body is essentially zero unless you have an extremely large surface area. In fact, at this point, drag and the erosion from atomic oxygen and free hydrogen are much more prevalent than the force of lift. As a result, once you reach this point lift is essentially zero although the engines would continually accelerate you to the necessary orbital velocity.
In other words, lift would be dependent on your surface area of the wings. This will get you to the top of the atmosphere. At which point, you have to use pure thrust to reach orbit. In addition, once you reach a certain point the O2 levels drop to the point where a scramjet is useless and you need to use conventional rockets.
Orbit is more a function of speed than a function of lift or drag. ISS uses reboosts periodically to compensate for the fact that LEO actually exists within the upper atmosphere and it's subject to a drag force.
Planetes
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I remember hearing about them doing this (or at least something very very similar) on the radio a couple of months ago. And that was Australian radio, I always thought Australia was the last place news reached.
Did they re-do the experiment/is it something new? Or is slashdot the last place news reaches?
interesting read, if anybody is looking for more info nasa has a good writeup on scramjets...
NASA - What's a Scramjet?
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The Soviets did it on Zond 6 (part of the Lunar L1 program), and it was heavily studied for Apollo and subsequent vehicles. Peak heating is lower than other entry methods, but only slightly, and the degree of precision required for the same ultimate landing position accuracy is much higher.
From http://www.space.edu/projects/book/chapter20.html
On November 6, 1968 a Proton rocket launched Zond 6 to within 2420 km of the Moon's surface. Cameras aboard photographed the Earth rising over the bleak lunar terrain; however, on the way back a gasket failed which would have killed any cosmonauts on board. Zond 6 performed a complex skip maneuver, decelerating to 7.6 km/sec over India then skipping back into space and landing in the Soviet Union. The parachute failed during landing and, once again, any human occupants would have perished. After this disaster, any thoughts of sending a cosmonaut to the Moon before January 1969 faded as Apollo 8 accomplished its historic lunar mission. There were three more Zond flights after Zond 6; a potential Zond failed on the 20th of January 1969 when its Proton booster failed. On August 8, 1969 after the successful Apollo 11, Zond 7 successfully orbited the Moon and returned. The last flight, Zond 8, was flown a little more than a year later successfully around the Moon, but landed in the Indian Ocean rather than back in Russia.