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Crazy Idea

Posted by: Texan - Sun Jun 27, 2004 9:28 pm
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Space Walker
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Post    Posted on: Tue Aug 03, 2004 3:49 pm
Why use air resistance to slow you down, when another rocket burn opposite to your direction of travel will do the same? Only problem is, you need fuel. Not quite the same quantity that was needed to put you up there in the first place, but a lot none the less. Maybe half to slow you enough to then fly the rest of the way home comfortably. The added benefit is that the plume of exhause gases are cooler than the atmospheric friction would be, so you can also use the exhaust as a heat shield too. Well, that's what I've gathered from others. Please correct me if I'm wrong.

So perhaps orbital tankers will be the way forward. BP in space anybody?

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Post    Posted on: Tue Aug 03, 2004 5:19 pm
*heh* My uncle is a BP executive. I think he'd be all for it :lol:

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Post    Posted on: Wed Aug 04, 2004 2:23 pm
I have been considering orbital tanking too but I'm not sure, wether the costs really will be less than in the case of launching the deceleration propellant together with the passengers. But it might be.

The tanking spacecraft should be unmanned and robotical. Having reached to orbit it should be nothing else than a tank - in principle.

I have in mind that the engine of SS1 is changeable. This might be a basis for simply removing the exhausted launch tank into the inner spacecraft and moving the unmanned arriving full tank to the place of the exhausted.

Besides - this changability of the engine is a kind of modularization.



Might it be possible to change the orbit from a circle to an elliptical orbit with apogee-velocity significant less than the velocity at the original orbit and around apogee deforming the orbit to suborbital trajectoy? Might that provide a possibility to decelerate more costlessly before reentry? What about deceleration by reentering and a little bit later leaving the atmosphere again to cool down at less velocity and then repeat this procedure? The velocity might be reduced then, the highest temperatures not reached etc.



Migh ther be hidden a solution?



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Post    Posted on: Wed Aug 04, 2004 2:57 pm
Okay. Please keep in mind that I'm not in the least a physisist or engineer. I'm a computer programmer and haven't had a science class in 20 something years.

If I understand orbit trajectory correctly, it's precisely the velocity that keeps the craft in a specified orbit. So the instant a craft slows down, the orbit decays. SS1 doesn't need more heat shielding because it never travels at the velocities required for orbit.

I can imagine that if you wanted to drop back to earth from an orbit in such a way that you had almost 0 forward velocity when you hit the atmosphere, you would have to have some sort of massive force to decellerate almost instantaneously. Something like Bugs Bunny's air brakes. And then you've got the problem of the incredible G forces inside the craft. I think you'd be squashed like a bug.

Someone tell me how wrong I am and I'll go back to writting code... :D

Your suggestion about changing to an eliptical orbit sounds interesting. But I don't see how that will help. It seems like the law of conservation would suggest that the amount of energy needed to change the orbit (so that the velocity is lower at apogee) plus the amount of energy needed to actually "stall out" would still equal the amount of energy you would need just to stall out in the first place (minus, of course, whatever miniscule drag you would experience). I guess it would help the squashed like a bug part, though.

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Post    Posted on: Wed Aug 04, 2004 4:12 pm
No fella, you're not wrong. Turn your ship around and fire your main engines. Most space craft only slow their velocity a little and use the atmosphere to decelerate the rest of the way. The problem is down to fuel. You accelerated up to that speed, now you have to decellerate. Look how much fuel the shuttle has to use. Now imagine how much more would be required to not only have enough to use for braking, but the extra needed to lift that extra fuel. I think the shuttle, at take off is something like eighty or ninety percent fuel. Is that right? If so, that's why traditionally we brake atmospherically, cos it's just too damn expensive.

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Post    Posted on: Wed Aug 04, 2004 6:39 pm
Hello, JustMeKevin,

there's no reason to go back to writing code.

The idea concerning the apogee and the velocity at apogee is as follows:

At circular orbit velocity is constant. It is possible to change the orbit to elliptical as usually is done to place a satellite at geostationary orbit. For the purposes discussed here it will be sufficient to reach an elliptical orbit with an apogee 1000 Km above the fromer circular orbit. At apogee (for example) the spacecraft migth be decelerated by short firing of the enigine. Then the elliptical orbit will become a liitle bit mor elliptical with pergee at less altitude than the former circular orbit.

The thrust at apogee doesn't need to be as strong as required for decelrating from Mach28 to - for example Mach 10 or so.

Each time apogee is reached there might be an additional thrust. The perigee altutde will be reduced more and more and at least it will reach the most upper atmosphere - Sean, there will be atmospherically braking now, but only for a short moment if the elliptical orbit is shaped correctly. In that short moment the spaccraft will fly a significant shorter distance through the atmosphere than the Shuttles are gliding to land. And it won't dive deep into the atmosphere.

Because of being in the atmosphere only a short moment the spacecraft will be decelerated a bit and there will be heating - but the heating will be last a shorter tiem as in the case of landing at once and it will not lead to those high temperatures reached in lower parts of the atmosphere. So after leaving the atmosphere again temperature will be lost into space and the cooling neede will be less as if it were diving deeper.

Now apogee will be reduced but decelerating by short thrust will be repeated.

The spacecraft now has lost velocity and the next perigee will be a little bit deep in the atmosphere. But because of the previous decelration the temperature and the forces will be less as in the case of the Shuttle. And so on. It will be repeated and perhaps by this combinations of rocket and atmospheric braking a velocity might be reached at which renetry will become possible at SS1-velocity and faethering becomes possible. This requires an additional reshaping of the trajectory near perigee.

Might that work? Is that technically possible and might there be advantages concerning the amount of propellant required?

The repetition of diving into the atmosphere and leaving again might be interesting for tourists - especially if plasma is to be seen.

Sean there is another point. I don't know wether you have been thinking of the Space Shuttle while writing your post. Let's consider the following point: When the Shuttle is in orbit its whole mass is payload. The payload mass of SS1 is much less. Because of this to a suborbital spacecraft able to carry a pilot and two additional persons might be added the differenc between the mass of the Shuttle and the mass of SS! as deceleration propellant.

What about that? Might the amount of propellnat required for breaking be less than the payload mass difference between Shuttle and SS1?

All this is sounding very very crazy I think - but I am playing only at the search for solutions. The relevant question is wether it is possible in principle and wether it has advantages compared to do all braking by rocket and wether it has advantages compared to atmaspherically braking too. Is it combining advantages? Might it be a compromise? Is it possible to make something acceptable of this possibly terrifying thoughts?

To prevent a misundertsanding - the idea is not to do this with SS1 -SS1 only is used as an illustration of volume and mass.

If it works the heat protection shields might be less extended and less costly as in the case of the Shuttle and the propeelant requirements perhaps don't remove that advantage.

Might all be huge nonsense - It#S only a trial to serach for solutions fit for private use.



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Post    Posted on: Thu Aug 05, 2004 5:17 pm
Assembling things in space isn't that crazy. It depends on what you assemble and for what purpose.

For safety reasons, the spacecraft that goes up should have an adequate heat shield.
If it wasn't for safety or if safety doesn't matter, one could send up spacecraft without thermal protection. In the future, in case something needs to come down, they could get a heat-shield or an automated re-entry vehicle (build on the moon for instance) from a supplier and use this way to bring it back down.

Re-useable orbital engines and some other equipment (solar cels, communcation and navigation equipment, etc.) could be left in space, remaining in orbit. This would allow new spacecraft to be launched without this extra weight, to unite with the necessary equipment already in space and to disconnect from it for re-entry.

Maybe we could see in the future some large spaceships staying in space and some launch / re-entry pods with only the minimum necessary equipment, launched from several sites on earth connecting to these spaceships.


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