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How high can a rocket go?

Posted by: roygrif - Tue Oct 12, 2004 2:07 am
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How high can a rocket go? 
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Post    Posted on: Thu Oct 14, 2004 5:59 pm
Well, the space shuttle is probably the best example we have of such a craft, although it's nose and leading wing edges still take most of the heat.

I believe the numbers for the space shuttle is a 20 degree re-entry angle, but the descent is only at about 1.5 degrees, so that they expose the underside of the shuttle as much as possible for maximum drag and heat spreading, whilst still taking a long time to decend through the atmosphere.

Giant parachutes deployed before you hit the bulk of the atmosphere might also help, although I have no idea how thick the upper atmosphere is, so it's impossible for me to calculate if this is actually a practical measure.

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Post    Posted on: Fri Oct 15, 2004 12:57 am
if you're going to deploy giant parachutes with carbon nanotube tethers holding them to the spaceship (the only way they could be used practically at high speed), i'd think the biggest question would be whether you'd wind up slowing down too rapidly. much beyond 5gs and, while the ship might get down fine, the people wouldn't!

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Post    Posted on: Fri Oct 15, 2004 6:34 am
Sev,

then I would prefer the Shuttle to be modified.

1. Its landing distance of 8000 miles should be much longer if possible.
2. I have problems to recognize the feathering in its wings - but I might be wrong. If I compare SS1 and the Shuttle then SS1 is going down vertical nearly and the folded wings are parallel to the atmosphere nearly but the Shuttle is going down not so vertically but its wings are parallel to the atmosphere nearly too. This looks like a difference - especially because SS1's wings are vertical to the direction of SS1's movement and the Shuttle's wings are parallel to the direction of the Shuttle's movement. Shouldn't the last constellation be changed? Shouldn't in the case of the Shuttle the feathering act more parallel instead of vertically?



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Post    Posted on: Fri Oct 15, 2004 10:59 am
Right, they both use the wings to increase drag on re-entry, but in different ways. I'm going to assume you know what both craft look like :)

In SpaceShipOne, when it re-enters (feathered) the wings are pointing in the direction it is travelling, or close to it. This means the wings themselves create very little drag (they are cutting through the air). But what the feather does, is it means that the craft itself - where the pilot sits - is not pointing directly at the air. In fact, the underside of the craft is what creates most of the drag, and cuts through the air. The underside of the craft, with it's large surface area, is what then creates the drag to slow down the aircraft, whilst also spreading the heat generated over a larger area.

The Space Shuttle does the opposite. Instead it tilts the whole ship by about 20-25%, so that the entire underside of the craft, wings included, creates drag and dissipates the energy. It's not quite as elegent as SS1's solution, but it also works.

The main difference in the methods is actually in terms of their in-atmosphere flight capabilities. The Space Shuttle's wings are not big enough to generate enough lift to keep it flying comfortably on it's own, whereas since SS1's wings fold they can be as big as it needs, and so it glides a lot more easily. Also, re-entry is more carefree since with the wings feathered it's perfect re-entry angle is also the natural angle it will take, where as the Space Shuttle has to be forced to re-enter at 20%. If the Space Shuttle was just left to drop out of space, it would drop nose first.

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Post    Posted on: Fri Oct 15, 2004 11:14 am
Thank you, Sev,

your post is improving my understanding of the physics of SS1 as well as it shows that my understanding of the Shuttle's physics isn't quite wrong.

The problem with the Shuttle seems to be that the wings would be too large if they were made big enough - second problem because velocity at reentry is the main problem I suppose.

Or are there ways to increase the Shuttle's wings and to provide feathering?



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