Posted on 11/10/2004 9:31:28 AM PST by the_gospel_of_thomas
To be honest, you do make a very good point. I swear.....I don't give a rip about how much money she has.......I couldn't get drunk enough...........
Actually you are describing a Ramjet. A Scramjet technically is a Supersonic Combustion Ramjet, thus a Ramjet where combusion is accomplished without the inlet airflow slowing down to subsonic velocities. Ramjet missiles have flown supersonically since the 50s (Bomarc), but when you don't have to slow the inlet airflow down to subsonic inside the engine, you can gain even faster exit flows, thus faster vehicle speeds.
The benefits of Ramjets and Scramjets over rocket engines is that you don't have to carry your oxidizer with you. Bad thing is that once you get to the upper atmoshere, you don't have much oxygen to scoop up. Going at high mach numbers in the lower atmosphere produces a lot of drag friction heating. And if your goal is to go orbital, you still have to reach exit velocity, which is a lot faster than any Scramjet can go.
Gee, I knew that degree in aerospace would be good for something after all. :)
I always wondered about that. Please explain how a centrifuge can accelerate tubes of whole blood to tens if not hundreds of gravities and the fragile red blood cells are not the least bit damaged. Still viable, usable. Why is a person in a tank of water any different? Seems acceleration would cause the perceived density of the water (perceived pressure) to go higher, but the relative density of the person would not cause excessive pressure against the bottom of the tank.
It's the ditching in the deep blue Pacific that we all have in mind here.
If that's the case, then one of my original assumptions was wrong - oops.
Simplistic - yes. Based on wrong assumptions of hiho hiho's understanding - yes. Wrong? yes and no. In truth, I hadn't even considered the acceleration required to fly at a constant altitude at Mach 10 when I spouted off. As a SWAG, it works out to be a little less than 0.2g Interesting, thanks.
Wasn't the German "buzz bomb" of the 40's considered a ramjet? In any case it was the first "cruise missile".
Undeterred by my earlier misjudgements, and partially in my own defense, I'll give it a go.
The original reply mentioned immunity from the effects of acceleration to which I objected, adding the word cushion. In hindsight, the first two people I replied to probably had a better understanding than I assumed.
In the blood cell example you raised, there are two things going on: low mass and force distribution. Blood cells don't have much mass to begin with so 100X doesn't amount to much. Plus, they're really small so the resulting forces don't have much leverage.
Putting a body against a soft cushion or in a liquid during acceleration spreads out the distribution of forces imparted. As a generalization, it's not force that breaks stuff, it's pressure.
I've seen the same principles at work in optical encoder components that undergo very high shocks. They don't break because they're really small, really light, and there's a drop of gorilla snot inside each one.
Camels and tents : watch out...
BUMP
With 'Scramjet,' NASA Shoots for Mach 10
http://www.freerepublic.com/focus/f-news/1276446/posts
Wow! That's MOVIN'!!
Yeah, I've read that the scramjets won't have very useful civilian applications, they will be great for cruise missiles though. I think the odds of us seeing a passenger jet based on one of these are about as great as seeing a passenger space shuttle taking tourists to LEO.
Save your money to buy a ticket on Virgin Galactic.....
This should be easy to test. Put a volunteer, or a chimpanzee, into a centrifuge with breathing apparatus suitable for REALLY high pressure diving. Fill the compartment with... not water, but something as close to the density of a human body as possible.
Then... SPIN!
I'd bet the subject could withstand at least 30 G's.
No, what I described was a Scramjet. Just because the flow passes through a shockwave (or a series of shockwaves) does not mean it slows to subsonic speeds (as in a ramjet). For an oblique shockwave, only the component of the flow normal to the shock is slowed to subsonic. So the flow will be slower than before, but it can still be supersonic. It all depends on the internal geometry of the engine.
Technically you are right, but I was trying to keep the explaination at a level that non-aero-heads would understand. :)
53 - Considering that centrifuges are used to separate things of different densitites, putting an animal in liquid in a centrifuge should work pretty well, like a human. And after centrifuging at 30 g's or what ever, the teeth should be in one level, the bones in another level, the lungs and stomach at another level, and the blood and plasma at another level, etc.
Sounds interesting, and yes, the teeth and bones would probably survive.
the densities aren't that different. You're 99% water... more or less.
Really, though, I'm not that familiar with jet engines. Reciprocating and rotaries I think I understand but not jets. What's the advantage to moving air through the engine faster - does one get higher thrust out of it? How does one start one of these - wouldn't the air have to already be moving through the engine at that speed before turning it on?
If they can get it into a small package, ten seconds would be plenty for an air-launched anti-ship missile. Less fuel weight equals more warhead size for the same total weight
57 - "the densities aren't that different. You're 99% water... more or less."
Mostly less, here are two quotes from the net, you can find more, but, one thing is certain, the human body is not 99% water, and each organ has different densities, and don't forget air. Just how dense are your lungs, mouth, stomach, esophagus, intestines, etc, and how much would they compress and separate.
Quotes:
- Up to 60 percent of the human body is water, the brain is 75 percent water, blood is 82 percent water, and lungs are nearly 90 percent water.
"Twenty five percent of the human body is solid matter and 75 percent is water states F. Batmanghelidj, MD, author of 'Your Body's Many Cries For Water'. "The brain is said to be 85 percent water." Human blood is 90% water, muscles are 75% water, the liver is 82% water and our bones are 22%"
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