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Maglev launch

Posted by: Garnetstar - Thu Sep 11, 2003 1:24 am
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Maglev launch 
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Post    Posted on: Sun Jan 07, 2007 1:52 pm
Not that much cheaper than big low cost launchers like Sea Dragon, and you have to spend a lot of time and effort (read fuel and man-space-hours) putting the pieces together. That could reduce the effective payload enormously.


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Post    Posted on: Sun Jan 07, 2007 4:24 pm
The time to put the things together can't be no valid criterion regarding the launch method - they have to put together on Earth as well which takes a lot of time also like the components of the ISS show.

The payloads launched via Launchpoint Technologies' maglev can be launched so that they all arrive at the same or similar distance to the place they are needed at. They then could be caught up together by something waiting close to that "place".

There only would have to be a simple store - which is no problem.

This method is the same as when bulding is built on Earth. It simply is a matter of organization, coordination and logistics - in the sense of Enterprise Economics.

And it seems to be clear that a payload launched by that magley doesn't need fuel - fuel is an additional option. Fuel would be required in LEO but organisation etc. can keep that optimal - like is done regarding transportation on Earth via road, river/sea and air.

Manpower in space is not that problem too -the longer one and the same man stays in space the more the costs to carry him there are degressing over time.



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Post    Posted on: Mon Jan 08, 2007 12:05 am
Maybe I'm still missing something. You accelerate an object to 27,500 kph inside a vacuum ring. Then you send it out through some air lock where it runs splat into the lower atmosphere. What is going to keep it from getting incinerated? Has anybody done any calculations about what the air resistance would actually be? Hitting a wall of air at sea level while going 27,500 kph would be like hitting a brick wall. The force exerted on an object by drag is proportional to the density of the fluid and to the square of the velocity. The density of the atmosphere at sea level is about 1000 times greater than at the altitude where meteors and spent boosters burn up. Since the velocities are similar, that means the maglev projectile would encounter a drag force roughly 1000 times greater. I bet it would be vaporized instantly.

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Post    Posted on: Mon Jan 08, 2007 4:39 am
Exactly. Even if it didn't vaporize it would decelerate so quickly that it would never make orbit.


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Post    Posted on: Mon Jan 08, 2007 9:36 am
Hello, Enthusiast,

as far as I know everything requires a bit of time until it is getting burnt.

The tiles of the Space Shuttle as well as the material covered by the tiles first begin to glow before something starts to be burnt - and the tiles need very long time until they are burnt.

Next the Shuttle needs a long time from reentry until touch down - compared to the time a projectile or 100 kg-payload launched by Launchpoint Technologies' maglev requires.

Asteroids enter the atmosphere at velocities above 27,500 km/h.

A more essential difference seems to be that nearly all objects - natural as well as artificial - entering the atmosphere do that with a large surface area ahead to the surface (like the Apollo capsules did). In difference to that Burt Rutan/Scaled Composites as well as t/Space prefer reentry with the smallest surface area ahead.

And there are significant differences between passing the atmosphere from surface to space and the reverse direction:

- The atmosphere is held down near the surface by gravity. So reentering objects compress it while leaving objects don't do that - the atmosphere simply can float aside and down then.

- Reentering objects are faced to ever and ever thicker regions of the atmosphere while leaving objects are faced to continuesly thinner regions of the atmosphere.

In so far - and that's what I wanted to illustrate - things are asymmetric. If a vehicle launches smallest surface ahead firtion is reduced and I suppose that a maglev-launched object will be shaped similar to rockets.

Plus WannabeSpaceCadet's hint that air drag might be a problem for a few seconds only.

And I myself already got the hnt in other threads that air is compressible...



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Post    Posted on: Mon Jan 08, 2007 11:54 am
Ekkehard your last post is wrong on so many levels, I scarcely know where to begin:

1) If the kinetic energy converted to thermal enegry is great enough, an object wil vapourize in much less than a second, let alone burn.

2) The space shuttle re-enters at 27,500 kph at > 60 km where the atmosphere is 1000 times less dense than at sea level. Heating is much much slower.

3) Asteroids also enter in low density.

4) Direction of movement has no effect on air resistance, except for ground effects at a few metres above the surface.

5) Blunt re-entry vehicles induce a shock wave in the air aheadof the vehicle to keep the hot air away.

6) SpaceshipOne feathered it's wings to present the maximum surface area and drag for re-entry

7) The T/Space capsule, based on the old Corona vehicle, also presents a blunt, high drag surface. It is just slightly narrower than the other end, so that the vehicle will automatically stabilize in the correct orientation.

And on you previous post:

1) Maglev cannot launch to a stable circular orbit. Just to an elliptical orbit that intersects the Earth's surface. Each payload needs it's own rocket motor to circularize the orbit (one that can survive the massive g's), or needs another vehicle to pick it up and move it to a stable orbit.

2) A space shuttle has 14 days max in space, so each hour costs about $2 million. It would take at least several hours for it to rendezvous with & pickup each maglev payload. And would require fuel weighing much, much more than the payload. Obviously you wouldn't use the shuttle, but any vehicle is going to find it hard to break even.

3) Each maglev launch does not even end up in the same orbit.


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Post    Posted on: Mon Jan 08, 2007 12:16 pm
Ekkehard Augustin wrote:
as far as I know everything requires a bit of time until it is getting burnt.


The projectile from a rail gun becomes a blob of molten metal as it is accelerated along the rails (normally a few milli-seconds), although this is more to do with current passing through it rather than air friction. :)

If you think of a bullet leaving a rifle (not sure what the acceleration would be), it will normally only carry for a mile or 2 so the chances of a projectile getting to orbit from sea level without further assistance seems a bit slim to me. Even a shell fired from a large gun on a ship for instance will only make 20 miles distance and that is in an arc falling to the ground, not sure what altitude they will reach but it cant be more than a couple of miles.

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Post    Posted on: Mon Jan 08, 2007 12:31 pm
Hello, WannabeSpaceCadet,

instead of applying simply your understanding of my posts you should ask how they are meant, if your understanding is correct and the like. To do so and to behave like that was part of the formerly higher standard of talk here - from my point of experience and view. It avoids misunderstandings and problems.

It is quite problematic - scientifically as well as normally - to have only one personal view of something and base all judgements about what a company in the engineering and technology industry does on this personal view.

First others - in particular others that are educated in the same science like those possibly employed at Launchpoint Technologies for example or publishing article at space.com perhaps - might have other personal views that are as well based and confirmed as yours.

Second as a scientific educated person you should doubt even your own results and issues - even if you talk to someone who is educated in another science or in no science. Else you mustn't wonder if someone answers like me here.

Third your answer sounds a bit as if misunderstandings are involved and you didn't take my answer to Enthusiast as Whole.

Some comments:

Quote:
1) If the kinetic energy converted to thermal enegry is great enough, an object wil vapourize in much less than a second, let alone burn.


The essential word or term here is If . I can't neither remeber nor find informations about the kinetic energy to be converted - so it might be that the kinetic energy converted is insufficient. Nothing against the term "If" - it's urgently required in science. I didn't say though that my issues you comment are generally or globally (in the mathematical sense of that word) valid.

Quote:
2) The space shuttle re-enters at 27,500 kph at > 60 km where the atmosphere is 1000 times less dense than at sea level. Heating is much much slower.


What of what I said is contradictory to that?

Quote:
3) Asteroids also enter in low density.


What of what I said is contradictory to that?

Quote:
4) Direction of movement has no effect on air resistance, except for ground effects at a few metres above the surface.


I simply said that the direction from surface up into space means that first the thicker regions and later the thiner regions of the atmosphere are passed while the direction down from space to the surface means that first the thinner regions and later the thicker regions are passed

Quote:
5) Blunt re-entry vehicles induce a shock wave in the air aheadof the vehicle to keep the hot air away.


To what you are responding here?

Quote:
6) SpaceshipOne feathered it's wings to present the maximum surface area and drag for re-entry

7) The T/Space capsule, based on the old Corona vehicle, also presents a blunt, high drag surface. It is just slightly narrower than the other end, so that the vehicle will automatically stabilize in the correct orientation.


I wasn't talking about the surface in general - I know well what you say because I long ago asked posters about it and got very reasonable answers at the standard high level I am missing since some time. I simly was concentrating on that portion of the surface that is faced directly to the destination. The portions parallel or nearly parallel to the path of motion are NOt faced directly to that destination.

Quote:
1) Maglev cannot launch to a stable circular orbit. Just to an elliptical orbit that intersects the Earth's surface. Each payload needs it's own rocket motor to circularize the orbit (one that can survive the massive g's), or needs another vehicle to pick it up and move it to a stable orbit.


This up to now is a statement by yours - but nothing officially is said that means that this statement would be true necessaryly. This I say regarding the intersection of the Earth's surface. But I do NOT say that the orbit will be circular.

Quote:
2) A space shuttle has 14 days max in space, so each hour costs about $2 million. It would take at least several hours for it to rendezvous with & pickup each maglev payload. And would require fuel weighing much, much more than the payload. Obviously you wouldn't use the shuttle, but any vehicle is going to find it hard to break even.


I didn't speak of no Shuttle, no ISS, no already existing artificial object. And if a vehicle can break even or not is NOT dertemined by Physics only because costs are determined by more factors than only physical ones (which should be discussed not here but in the Views-thread.

Quote:
3) Each maglev launch does not even end up in the same orbit.


I didn't say something like that.



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

By the way: Please urgently keep in mind my reactions to campbelp2002...


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Post    Posted on: Tue Jan 09, 2007 1:39 pm
Ekkehard, you obviously cannot read & comprehend your own posts, let alone those of others. Nor can you differentiate between speculative opinion and basic high school science. So I give up. I won't be responding to your posts anymore. :(


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Post    Posted on: Tue Jan 09, 2007 2:28 pm
Hello, WannabeSpaceCadet,

of course I checked my own post you were responding too before I posted my previous answer:

My previous answer simply is a list of facts about the environment launched objects or even reentering objects pass through.

My previous answer is NOT a scientific issue about all the consequences that environment has.

Do I have to assume that from your point of view the atmosphere is NOT held down by gravity? (for example) Do I have to assume that from your point of view reentering objects are faced to the thicker regions of the atmosphere first when they leave space and reach thinner regions of the atmosphere later only when they are close to the ground???

You may have been interpreting into that post that I would have concluded something from the list - and you may have interpreted conclusions that are wrong. But these wrong conclusions aren't the only possible ones - and I didn't have no particular conclusions in mind.

I had in mind the list simply and a few things I know.



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EDIT:

I sent him a PM that I accept his refusal to talk to me furthermore but also offers opportunities to clarify the links and connections between his yesterday post and my previous post which simply is a perhaps incomplete description of the environment that may include irrelevant properties or aspects.


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Post    Posted on: Tue Jan 09, 2007 6:45 pm
I think it's just a language problem between you two.

I did read the same story from your post as wannabe did Ekkehard.


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Post    Posted on: Wed Jan 10, 2007 9:15 am
Hello, IrquiM,

the problem is not how WannabeSpaceCadet read or understood my post(s) but that he has no doubts that he read or understood it correct. He has no doubts and he insists on being correct. In particular the issue
Quote:
Ekkehard, you obviously cannot read & comprehend your own posts
is inacceptable - I think very well about what I have in mind or think and how to express it before I post it. A few moments later I got a call from another Economist of my federation and told him about the experience - he at once recognized what had happened and identified WannabeSpaceCadet's behaviour as improper and even bad. He mentioned a case where such a behaviour caused damage to a large group of people.

The human language is not 100% precise and the context of an issue is of meaning for what an issue means - it mustn't be broken off the context, off the whole.

In the Moon-related thread in the General Armadillo Aerospace Forum section I fixed the problem and pointed to it.

Misunderstandings are possible allways - and there are ways to handle them properly which avoids problems like that between WannabeSpaceCadet and me as well as those between campbelp2002 and me which I in between avoid by refusing to talk to campbelp2002.

Thos too simply refuse to apply the ways to handle misunderstandings properly.

Your post instead handles them: You say that you read my posts like WannabeSpaceCadet but now seem to accept my statement that that is a misunderstanding.



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

EDIT: I remember very well that formerly a lot of misunderstandings have been handled proper ways - be a lot of others as well as by me. This was one component of the formerly higher standard and level of communication here. in those times problems like those I now had or have with campbelp2002 and WannabeSpaceCadet didn't occur.


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Post    Posted on: Wed Jan 10, 2007 12:50 pm
Ekkehard Augustin wrote:
Your post instead handles them: You say that you read my posts like WannabeSpaceCadet but now seem to accept my statement that that is a misunderstanding.


No, I do not accept your statements, but I do however know that German and English are two different languages, with completely different ways of building a sentence (speak both to some extend), so I believe you mean something other than what I read.


It's alot easier to reenter then atmosphere, than to escape it, thus those cannot be compared...


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Post    Posted on: Thu Jan 11, 2007 5:46 am
I've been doing some calculations to shed some light on the feasibility of maglev launch. I've calculated the drag force and integrated it to figure out how quickly the speed will drop off after launch. My equations include the effect of decreasing atmospheric density with altitude. Unfortunately, the heat transfer problem is pretty sophisticated and I couldn't find the equations I needed by googling. So I can't address the question of how rapidly a projectile would heat up. I can tell you, however, that a tremendous amount of energy gets dissipated very quickly. And, as we expected, at such high speeds in the lower atmosphere the drag forces are astronomical. Velocities drop to almost zero in seconds. The bigger and heavier the projectile the higher it gets before it slows down.

To get a feel for the numbers, I tried several scenarios. In each case, I calculated how high the projectile would get before the speed had declined to Mach 1. (The equation I'm using is for hypersonic velocities, so it wouldn't make sense to use it for the subsonic region.) Here are a couple of examples:

1. Launch a 1 meter sphere with the density of water (525 kg)
t0 = 0 s
v0 = 5000 m/s
h0 = 0 m
initial deceleration = 1355 g

t1 = 8.2 s
v1 = 330 m/s
h1 = 7072 m

2. Launch a 10 cm sphere with the density of steel (4.1 kg)
t0 = 0 s
v0 = 5000 m/s
h0 = 0 m
initial deceleration = 1720 g

t1 = 5.8 s
v1 = 330 m/s
h1 = 5129 m

3. Launch a 1 cm sphere with the density of lead (5.9 g)
t0 = 0 s
v0 = 5000 m/s
h0 = 0 m
initial deceleration = 11950 g

t1 = 0.62 s
v1 = 330 m/s
h1 = 594 m

Just in terms of ballistics, if you make the thing large enough and heavy enough and give it a high enough initial velocity, I'm sure you could get to space if the projectile is not destroyed by the g forces and the heating. I think those are some pretty big ifs. And I don't see how you could get into orbit. It doesn't seem like this would ever be a practical launch system for use on Earth.

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Post    Posted on: Thu Jan 11, 2007 8:00 am
Hello, Enthusiast,

this I find very positive. You are doing calculations and listing the results. This is on the level I am used from former times here.

Very, very good.

One point I am wondering about because of my earlier description of the environment in the form of the list is what effect it might have that a portion of the heat caused by friction might be radiated away. If the vehicle would move by constant velocity - which I suppose not to be the case - then the higher the altitude reached the less the heat added by friction because the air is thinner I suppose (I might be wrong!). As far as I understand it from other threads and posts from 2004 and from my Physics classes the higher the altitude reached the easier and more quickly heat is radiated away. The assumption that the vehicle/projectile would move by constant velocity is wrong - it would be interesting what the heat of the vehicle will be at alternative altitudes and what portion of it will be radiated away if at all.

Another question coming up to me is which impact alternative geometries of the projectile have.



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