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Doubts If ATO will be working

Posted by: Ekkehard Augustin - Sun Sep 04, 2005 11:37 am
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Doubts If ATO will be working 
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Post    Posted on: Thu Nov 24, 2005 1:58 pm
This may be a dumb question, but does the ascender ever go hypersonic?

AFAICR, the speed of sound increases with decreased air density. So as you get higher, you need to be travelling faster to remain supersonic. If your rate of climb is matched to acceleration, you could remain just below supersonic all the way in to orbit. Same happens when coming down.

If you remain below supersonic the high drag problems ayt hyperspeed goers away, and heating issues on the way down decrease. You need less thrust to keep accererating past supersonic speed because you in effect never reach supersonic, even though you reach orbital velocity.

It's a balancing act, but does it work?

I am prepared to crash and burn on this one...

James


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Post    Posted on: Thu Nov 24, 2005 2:03 pm
Hello, James Hughes,

you are speaking of the Ascender. Sometimes Ascender and ATO seem to be confused with each other.

Since the Ascender is the vehicle going up from ground to the DSS and thus is moving vertically only it seems to me that it never will move supersonically nor it is intended to.

The ATO is required to go supersonically since its destiny is the orbit.



Dipl.-Volkswirt (bdvb) Augustin (Political Economist)


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Post    Posted on: Thu Nov 24, 2005 2:54 pm
JamesHughes: Well, I would have thought that too, so I don't blame you. Turns out, the speed of sound is related to the average speed of air molecules, which is given by the temperature. Now, different gasses (and liquids and solids too) at the same temperature do have different speeds of sound, with the speed of sound increasing with density. So you were close. Unfortunately, it means that the speed of sound in the upper atmosphere doesn't change a lot (not as much as density), and isn't that far from what it is down here.

One other thing: I agree that it would be best if the ship could rise to orbital altitude or nearly so while staying below the speed of sound. I think, in fact, that may be the only way to go. But as Ekkehard said, the ship is going to need to pick up some real speed higher up to get into orbit, and maybe quite a bit at a lower altitude when there is a need to replace aerodynamic lift with centrifugal force. So it will need to operate super and probably hypersonic, but I disagree with nilihadrem who says that most of the flight must be conducted above the speed of sound.

LEt me see something for a minute: if you are going 5x the speed of sound in a very low density atmosphere, there's going to be very little of air molecules impacting the down-wind sides of your craft (like the back side of the balloon arms), and lots of impacting on the front side and bottom. Seems to me that in these ranges, air will not really follow the curvature of the wing like Bernoulli's principle needs it to, and so you don't have to make a nice airfoil shape to get lift. All you need to do is present a sloped surface to the air and deflect it down. Normally, that would be bad b/c of a vortex created above the surface at the leading edge, which is why you through in the top half of the wing (the nice smooth curve). BUt if you are going hypersonic, and being in that low density, seems like you won't need to worry about that, all you'd need to do is fly a boilerplate at an angle of attack to get lift. More like skipping a stone than anything else. Maybe the ATO can get a good L/D after all.

Lourens: yes, that's a good name for it: the outboard plasma drive. Now, if you have the drive set up away from the body of the of the ship, maybe in a ducted assembly or just some big grids hanging somewhere, I think that will be extremely impractical. Do a google search on 'HV lifters' and see what kind of thrust these type of ion wind craft get. Not spectacular, not enough thrust to lift an HV power supply, let alone an energy source. You'd be better of using propellors than an outboard ion drive, I think.

But if you're ion drive interacts with the air directly around the ship, perhaps utilizing the ionization as you suggested, I think we might really get somewhere. With the outboard drive, you are pushing the craft forward against the drag of the skin. With a good skin-based propulsion, you could basically lubricate the ship and pull it along by accelerating just the air that touches it.

Hmm, I think someone on this forum was looking into a skin-effect magnetohydrodynamic propulsion or lubrication. I'm going to go look him up. [/b]


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Post    Posted on: Thu Nov 24, 2005 3:04 pm
I think rather than Bernoulli, its the Coanda effect that give you the most lift from a surface.

http://jef.raskincenter.org/published/c ... ffect.html


James


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Post    Posted on: Mon Nov 28, 2005 9:13 pm
LukeSkywalker wrote:
Hmm, I think someone on this forum was looking into a skin-effect magnetohydrodynamic propulsion or lubrication. I'm going to go look him up.
This is the thread you are looking for:
http://www.spacefellowship.com/Forum/ab ... asc-0.html


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Post    Posted on: Tue Nov 29, 2005 12:52 am
Yeah, it's been a while since we've heard from timallard -- a pity, since he was doing some pretty interesting stuff.

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Post    Posted on: Wed Nov 30, 2005 2:28 pm
JamesHuges: yes, I've read about that. I personally prefer this analysis, though: http://www.aa.washington.edu/faculty/eberhardt/lift.htm I figured everyone would be familiar with the Bernoulli concept, though.

Campbell: yup, you found it. It is a pity he isn't around here still.


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Post    Posted on: Wed Nov 30, 2005 5:15 pm
His name is still in the member list, as is his web site. http://www.mallard-design.com/ Has anyone tried contacting him directly?


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Post    Posted on: Wed Dec 14, 2005 1:59 pm
I just noticed this BBC news story about a new, higher-thrust ion drive. It seems that the ESA homepage on it is here. Could this be useful for ATO?


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Post    Posted on: Wed Dec 14, 2005 2:16 pm
:idea: :roll: :twisted: Or an other great news source: http://www.spacefellowship.com/News/?p=1331

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Post    Posted on: Wed Dec 14, 2005 4:35 pm
Haha poor sigurd feels like his news is never read :(

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Post    Posted on: Wed Dec 14, 2005 7:18 pm
Doh! Sorry :). If you had an RSS feed I'd add it to my live bookmarks, which would greatly increase the chances of me reading...


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Post    Posted on: Wed Dec 14, 2005 9:02 pm
http://www.spacefellowship.com/wp-rss2.php :idea:

And no prob ;), :roll: but always hoping for more visitors to the site :wink:

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Post    Posted on: Thu Dec 15, 2005 6:23 pm
Ah, excellent. Space.com, consider yourself replaced. And none too soon either, even with Firefox and all defences up that site is obnoxious to the point of being unwatchable.

*starts reading*


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Post    Posted on: Fri Dec 16, 2005 3:15 am
Yay! That's now set as my screensaver. I love OSX Tiger.

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