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Fluid Freefall from Orbit

04/05/2010 9:09 PM

If Rocket fuel were poured out from geosynchronous orbit, and allowed to freefall to earth, what would happen? Flames, vapourization, precipitation?

What would different fluids behave like? (ie; Liquid Oxygen? Kerosene? Hydrazine? etc.) Is there a safe liquid that would work?

Is there any possibility a vehicle like a ramjet could use it to boost to orbit?

just curious...

Chris

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#1

Re: Fluid Freefall from Orbit

04/05/2010 10:06 PM

I had to look, but April first has gone.

You can't pour anything while in geosynchronous orbit, gravity is neutralized by the centripetal force. If you squirted it, it would stay in orbit. I imagine it will vaporize although the lack of heat on the dark side might keep it together.

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#4
In reply to #1

Re: Fluid Freefall from Orbit

04/05/2010 10:57 PM

Oops, yes you are right!

I was focusing too much on how I wanted the fuel to come straight down... but that isn't going to work. If the fuel satellite is moving, the fuel will come down in an arc.. but that might work too.

Chris

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#24
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Re: Fluid Freefall from Orbit

04/06/2010 11:39 PM

No! Gravity is NOT neutralized by the centripetal force! Gravity IS the centripetal force, and its just the right amount to keep anything in that same circular orbit at that same speed.

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#26
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Re: Fluid Freefall from Orbit

04/07/2010 2:56 AM

I thought centripetal force was at right angles to a tangent line of the arc the object traveled. If so, wouldn't gravity be the opposite direction as the centripetal force, and when they are equal and opposite is when you get free fall near a gravity well.

Drew

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#28
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Re: Fluid Freefall from Orbit

04/07/2010 4:36 AM

Centripetal force is indeed at right angles to the tangent to the arc, and pointed directly toward the center of that arc. In the absence of all forces, the object would continue in a straight line along that tangent, with the same velocity it already had. By following that tangent, it would go flying off into space, leaving the current orbit. For an object in geostationary orbit, the velocity is such that the object takes exactly one day to make one full orbit in a perfect (or very nearly perfect) circle around the Earth, and the center of that circle is the center of gravity of the Earth. The gravitational attraction between the Earth and the satellite ('gravity') is a force which is always perpendicular to the instantaneous velocity of the satellite, directed toward the center of that circle. That force ('gravity') causes the satellite to curve away from the tangent and toward the Earth, just enough to keep the satellite at the same distance from the Earth.

The satellite is always 'falling' toward Earth. There is no force 'counteracting' gravity, for an object in circular orbit.

On a merry-go-round, a person 'feels' like he is being thrown away from center, and the fictitious force thought to be doing the throwing is commonly called centrifugal force. The 'fug' is the same base as in fugitive, meaning to escape (away from center). This is a fictitious force, because in fact the person' body is simply trying to follow that tangent. A real force toward the center is required to keep the person following the curved (circular) path, and that force is called centripetal force. the Latin origin of 'pet' in this word isn't as obvious but it means 'seeking', so a centripetal force is a force toward center.

At least passingtongreen used the correct term!

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#32
In reply to #28

Re: Fluid Freefall from Orbit

04/07/2010 11:02 AM

Ok, so by saying centripetal force you mean gravity is acting like the string when you spin a weight around and the force is the tension from the string that is keeping you in a curved arc around the center.

Now I get it I thought for a second you were out in left field with a tin hat saying it was the other way around . Now I realize it is my misunderstanding, thanks for clarifying.

Drew

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#33
In reply to #32

Re: Fluid Freefall from Orbit

04/07/2010 11:13 AM

You got it! I like your weight-on-a-string example better than my merry-go-round. For a satellite, gravity is the string.

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#42
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Re: Fluid Freefall from Orbit

04/09/2010 8:15 AM

I like the Newtonian explanation; if you fire a cannon from the top of a mountain, the cannonball will start to go tangentially, but gravity will pull it down to Earth. If you increase the explosive power, it will travel further before it hits the ground. Increase it to just the right amount and it will fall towards Earth but never get any closer, it will be in orbit.

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#43
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Re: Fluid Freefall from Orbit

04/09/2010 10:14 AM

Unfortunately, that orbit passes through the Earth, so it's not truly an orbit, just a trajectory. Even ignoring all the air friction isues, it still needs a final horizontal boost when it reaches altitude in order to maintain that altitude (that is to change the orbit from one that passes through the Earth, to one that doesn't).

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#44
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Re: Fluid Freefall from Orbit

04/09/2010 10:44 AM

Holy Spaghetti monster.

It is assumed to be from the highest mountain on an airless planet, then it doesn't have to pass through anything if the cannon is immediately removed. It does not have to climb, this is not a geosynchronous orbit, it is in the orbit the moment it is fired horizontally. At just the right velocity, it is in circular orbit, less and it falls to ground, more and it goes into an elliptical orbit, more still and it escapes into space.

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#45
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Re: Fluid Freefall from Orbit

04/09/2010 12:47 PM

That point at which the trajectory becomes circular, and at which you will shoot yourself in the back of the head, (duck! ) is technically called "Zero Circular Orbit". (I believe this was in a book I had by Willy Ley. I don't have the book to hand. its in ontario. but I did just find this gem while searching..)

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#30
In reply to #26

Re: Fluid Freefall from Orbit

04/07/2010 9:33 AM

You are mixing Centripetal (Toward the centre) and centrifugal (Away from the centre.Gravity pulls (centripetal force) while the orbiting speed creates a centrifugal force to counter the gravity pul. {Centrifugal = running away from the centre)..

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#2

Re: Fluid Freefall from Orbit

04/05/2010 10:10 PM

Depends on how much of what whether you might even get a light show. Even meteors have to be of a certain size, and composition to hold together enough to catch our notice. I can't think of a gas or liquid that wouldn't have to be packaged or frozen, that wouldn't be dissipated by friction mostly with little notice or affect. Guess you could call it vaporization.

Not sure what work you want the liquid to do?

I forget which planes have the capacity to do fuel dumps when overladen they suffer on takeoff engine failures. Think the 707 could do that, and think some did.

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#31
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Re: Fluid Freefall from Orbit

04/07/2010 10:01 AM

All the planes I was familiar with (that made carrier based takeoffs and landings) had the ability to dump fuel.

In fact, the planes would be fully loaded with fuel, be launched, dump fuel and do "touch and goes" for practice.

The planes would dump any excess fuel not used during a mission before landing.

The impact from an arrested landing was tremendous, and I suppose any reduction in weight would mean a reduction of forces involved.

All of this meant thousands of gallons of fuel dispersed over the oceans.

Testimony to this was the fact that the electronic "sniffers" our planes were equipped with for the purpose of detecting diesel combustion byproducts, were useless.

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#3

Re: Fluid Freefall from Orbit

04/05/2010 10:31 PM

The textbooks say 'nature abhors a vacuum'. Your liquids will disperse as fast as they can. They can't burn, no oxygen at the right mix, no spark, basic three elements of fire. They would not be close enough to Earth to fall, geo is way up there, and like already said, they are in orbit.

Trying to leave something to feed ramjets is just silly. They zip past so fast, they would miss most of the fuel.

Looks like you need another hobby. Check out smallblimps.lefora.com , we are trying to make a personal blimp, going in circles.

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#5
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Re: Fluid Freefall from Orbit

04/05/2010 11:04 PM

Mike & Trans,

Now that we've figured out that it can't be geosynchronous, the fuel will come down. So Mike, you are saying it will turn into a rapidly expanding fuel cloud as it descends?

There is a sci-fi engine proposition called the Bussard Ramjet that uses a huge magnetic field to scoop up interstellar hydrogen. I'm thinking that if there is a cloud of fuel that is laid out along the trajectory of the rising craft, that it might save fuel.. but obviously its a catch-22, because how did the fuel get up there in the first place.. so maybe this is an exercise in futility...

But we are not making much progress with conventional methods in terms of getting off planet with lots of mass, so I'm really trying to brainstorm different methods. Not all are going to work obviously.

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#8
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Re: Fluid Freefall from Orbit

04/05/2010 11:45 PM

Well, now we get down to what you really want to do.

Getting stuff in orbit is a good challenge. NASA has been going straight up for a long time, but I don't like it. They say they looked at other options, but I don't believe them, isn't that awful?

NASA used to drop X-15s from B-52s and send them up, almost to orbit. The Blackbird almost made orbit on it's own power, some say.

Sir Richard Branson is about to launch another ship for a quick shot way up there. Not orbit, just way up there.

Orbit is fifteen thousand miles per hour. Maybe more, 17.5? Whoa, that's fast.

I like the 'fly up' scenario best. Have a mother ship that can go really fast, a used SST would be nice. It carries the next stage, a nice little scramjet model that carries it's own fuel and oxidizer. It launches at max speed and altitude of the SST, a lot more than the B-52. The scramjet pops into orbit and does whatever it can. It's not real big, so things are limited.

The real trick is getting back down. The Shuttle has just enough fuel for a slight braking maneuver, so it has to have a heat shield. The scramjet has enough fuel to slow down enough for a safe re-entry at flying speeds.

That's enough for a good sci-fi story. Next week I'll show you the Pike's Peak Model, or the hydrogen airship model, but the math isn't as good on them.

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#22
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Re: Fluid Freefall from Orbit

04/06/2010 11:16 PM

Not to worry, Chris. With all the earthquakes we have been having lately, it appears the earth is coming apart at the seams, and we are all likely to be floating about on small chunks of it in the not too distant future...We won't need to launch a lot of mass from the earth, because earth will launch us...

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#6

Re: Fluid Freefall from Orbit

04/05/2010 11:23 PM

The fluid would vaporize instantly.

PUT THAT JOINT OUT NOW! YOU'VE HAD TOO MUCH!!!!

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#7
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Re: Fluid Freefall from Orbit

04/05/2010 11:37 PM

I gave that up years ago..

so by vapourize, you mean it would turn into a gas.. it would spread out.. but no oxygen would be added.. until it gets into the atmosphere. I agree it would. Is that bad? I think that might must make the fuel more usable. How much would it spread out? How much Oxygen is in the upper atmosphere?

It (the fuel) has the same mass, even spread out, so would continue to be accelerated by gravity. It would still fall to the earth. spreading out would actually prevent it from igniting don't you think? (until entrained by my new super-duper radial ramjet and converted to propulsion)

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#12
In reply to #7

Re: Fluid Freefall from Orbit

04/06/2010 2:46 AM

Prototype Radial Ramjet 01

8 rigid "Bernoulli Effect" shaped stators to conduct fuel-air composition into compression zone for combustion. If it is big enough, and if there is fuel mixed with the air, it will assist the ramjet combustion. The combustion can be augmented of course with Ox/Fuel carried on board. (sprayed from nose based nozzles)

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#19
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Re: Fluid Freefall from Orbit

04/06/2010 7:46 PM

Ram jets only operate at very high speed. The stators you show would have too much drag for those speeds, in atmosphere. The idea of collecting hydrogen from space probably would have too small a return for any appreciable power.

There is progress being made in plasma and ion drive. That's why I advise collecting all the space junk. It's already up there, and would be fuel for those drives. Just get your ship and drive up there, all that mass is free for the collecting.

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#20
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Re: Fluid Freefall from Orbit

04/06/2010 8:55 PM

okay thanks mike

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#9

Re: Fluid Freefall from Orbit

04/05/2010 11:56 PM

Grasshopper,

How would you get the, " Rocket fuel" up in to geosynchronous orbit? Assuming you could get a couple of tons in orbit, what would it do? It's late where I am.

I'll sleep on it.

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#10

Re: Fluid Freefall from Orbit

04/06/2010 12:08 AM

The hydrogen magnet you described only works on H1 because it is polar and thus attracted by a magnet. In space there is hydrogen, but it is not like the H2 we work with here. I assume because it only has one electron it will be just as instable and readily combine with Oxygen making H20 and .... (crap cant remember other product). Anyway, any hydrogen you release will probably be in the form of H2 and not magnetically attractive.

Vaporization would occur, and if moving less than orbital velocity it would disperse like any gas (or gasified liquid) released in a vacuum. It would descend into the atmosphere according to the gas laws and its own specific gravity. Hydrogen being light would stay higher, oxides, hydrocarbons and other molecules would settle according to their terminal velocities. Point is they would spread too far and wide to be useful for fueling.

I like the idea of using the friction, lift and traction offered by the atmosphere then a switch to rockets once sufficient altitude and velocity are achieved.

I also liked the idea of using a rail gun sled to launch up the side of a large mountain, so you are at altitude and speed before you ever start using fuel.

Drew

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#11
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Re: Fluid Freefall from Orbit

04/06/2010 1:00 AM

I like that.Going up the side of A mountain with a rail gun type launcher.

Seems Maglev trains would move a pretty large mass pretty darn fast,like you said,BEFORE using any Rocket Fuel.

In fact this all sounds so good,I wonder why someone isn't using it?

Joe in Texas

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#16
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Re: Fluid Freefall from Orbit

04/06/2010 11:47 AM

that one is fairly well laid out in Marshall Savage's Bi-Frost plan in his book "The Millenial Project: Colonizing The Galaxy In Eight Easy Steps" I espcially like the use of ice blasted with Lasers for the final boost phase.

Check out the project Orion Nuclear Rocket animation on this site. very interesting.

http://www.projectrho.com/rocket/rocket3ay.html

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#18
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Re: Fluid Freefall from Orbit

04/06/2010 7:28 PM

Seriously cool link. Thanks

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#15
In reply to #10

Re: Fluid Freefall from Orbit

04/06/2010 11:12 AM

I sort of like this idea set as it closes up myself. However I'm not the rocket scientist of the group. Usually I rely on Bhankii and Rhabe and AH in these areas. I was under the impression that some of what NASA and the Russians did was done partly because it worked, and not because there weren't better ways.

I did speak once with a SR71 pilot who said he had had to push down on the yoke to keep from completely leaving Earth.

I myself recommend a robust near earth orbit space system for both commercial applications, planet defense, and pure scientific research. Early in my life I rejected the Space Elevator concept, but I have warmed to it since carbon nanotube development may enable it.

Of course to build even that we will need semi heavy lift space vehicles and since we are dealing with Earth Atmosphere and no atmosphere hybrid systems are called for, for whatever has to work in both. This rail assist system is attractive to me.

I wonder if the numbers add up correctly?

Far as fuel, and living in outerspace, and what work needs to be done in outerspace, well there is a need for a Planet Defense System, and possibly fuel for that can be at least made by robots on the moon.

Some say we need to mine Asteroids and the Moon. I'm not sure if that will anytime soon at least be profitable. I sort of wonder if we wouldn't be better off making things out of sand instead of metals at some point. Certainly plastics are dependent on Oil, so the use of glass is recommended, also due to environmental problems in the food chain come from all this plastic floating and flying around.

Anyway I was simply caused to think about these things, and sure admit I am only good for some generalities.

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#23
In reply to #15

Re: Fluid Freefall from Orbit

04/06/2010 11:25 PM

We already make a whole lot of things out of sand- like the innards of this computer, and photovoltaic solar cells and plain old window glass...

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#37
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Re: Fluid Freefall from Orbit

04/07/2010 8:26 PM

I was thinking about engines made of glass, and further substitution of glass for metals, or plastics, beyond current use. I probably ought to look at the Corning site, to see what they've got going these days. Seems like I remember from years ago seeing images of IC engines made of glass, instead of Aluminum, or iron and steel.

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#27
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Re: Fluid Freefall from Orbit

04/07/2010 3:44 AM

launch up the side of a large mountain

Kilimanjaro must be favourite.

It would be handy if you could extend a tube further into the lower atmosphere, and, pump as much air out as possible ('course this would need to be a continuous process). Maybe Dyson's blade-less fan will come into its own in this application, I wonder what the max. diameter is.

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#13

Re: Fluid Freefall from Orbit

04/06/2010 7:23 AM

It would vaporise, as the pressure would render it above its boiling temperature. It would then expand and be blown away by the Solar Wind.

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#14

Re: Fluid Freefall from Orbit

04/06/2010 10:45 AM

I don't know how you are going to get the stuff up there in the first place, but have you considered pellets of solid fuel? Like a trail of match heads aimed back toward Earth, they would form a spiral path, at least until the first ones reached the atmosphere where the friction would light them up, so to speak.

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#17

Re: Fluid Freefall from Orbit

04/06/2010 3:07 PM

I imagine it would behave similarly to the urine that used to get dumped from Apollo capsules - it vaporizes into little ice crystals which give a nice show in the sunlight.

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#21

Re: Fluid Freefall from Orbit

04/06/2010 10:35 PM

well, a solid fuel would accelerate towards the earth and would experience a situation where the earth soon started to turn away from it. The orbital velocity in synchronous orbit is about 3400 miles per hour. Just above the atmosphere it is about 18,000 miles per hour. The sum of kinetic energy and potential energy being the same.

So it would soon speed up and experience a side force and have a complex path before hitting the air and getting very hot.

Most liquid fuels would boil off into the vacuum of space and disperse widely with a long mean free path. The average velocity and random mean free path would mean few would reach the earth. The solar wind would drive most away. Few would encounter a reactive moleclue to react with and in fact might get ionized.

If you had an item held stationary far up, as the earth spun, it would eccelerate in and reach close to escape velocity (reach from a fall from infinity)

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#25

Re: Fluid Freefall from Orbit

04/06/2010 11:51 PM

Hydrogen will only exist as a stable gas as H2. Ditto oxygen. Dump them out into space and they rapidly disperse to concentrations approaching the naturally-occurring ones. Liquid hydrocarbons will freeze and then sublimate. Also dispersing to naturally occurring concentrations.

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#29

Re: Fluid Freefall from Orbit

04/07/2010 6:11 AM

I am not sure that they would not freeze until they burned in the atomssphere upon rentry.

someone sent me this link years ago, from NASA, that explains some of it.

NASA explains shooting stars

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#34
In reply to #29

Re: Fluid Freefall from Orbit

04/07/2010 12:04 PM

that's hilarious! ga

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#35

Re: Fluid Freefall from Orbit

04/07/2010 1:23 PM

Dear Mr.Chrisq 288,

At a very very high altitude the fuel poured out will no longer be liquid since the temperature there will be very much, much below ZERO.

Probably below the freezing point of fuel and becomes solid and NEWTON's Ist Law takes care of the solid motion. It will move in an orbit as for as motion is concerned which will have an APOGEE and PERIGEE, and the speed will be governed by KEPLER's LAW, which states that for a given time , the area swept will be equal in the ELLIPTICAL ORBIT.

The apogee and perigee are governed by several factors.

DHAYANANDHAN.S,

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#36
In reply to #35

Re: Fluid Freefall from Orbit

04/07/2010 1:52 PM

Thank you. I think this is true.

Does anyone know or can calculate at what height above sea level the solid fuel will liquify due to friction? and subsequently vapuourize and flash?

Chris

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#38
In reply to #36

Re: Fluid Freefall from Orbit

04/08/2010 2:46 AM

Why would you expect it to freeze so rapidly? It's only way to lose heat is through radiation.

Don't forget that the pressure is zero so almost anything will boil. Even small droplets which are left frozen will probably sublimate (from solid to gas) long before they get anywhere near the earths atmosphere.

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#39
In reply to #38

Re: Fluid Freefall from Orbit

04/08/2010 11:39 AM

just because it was pointed out that urine from the Apollo units froze almost instantly. I agree that fuel might not freeze so quickly.

Chris

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#40
In reply to #39

Re: Fluid Freefall from Orbit

04/08/2010 12:13 PM

Did the Greek God Apollo have more than one unit?

Is this where McDonald's got their idea for the "Golden Arches"?

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#41
In reply to #40

Re: Fluid Freefall from Orbit

04/08/2010 1:30 PM

1) yes, he was the god of the spaceships. plural.

2) McDonald may have been the scottish god of yellow snow. M is the easiest letter to write and most used in scotch (every word starts with Mc), so scotsmen have the most practice with with their 'penmanship'. I bet you didn't know that the scottish variant of that god is McApollo, (Zeus is of course, Big Mac) and he invented wearing Kilts for the obvious reason. (something to do with the tartan rocket )

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#46
In reply to #36

Re: Fluid Freefall from Orbit

04/09/2010 1:15 PM

Dear Mr.Chrisg 288,

Solid fuel at high altitudes will never become liiquid, unless gas is liquified and further cooled, or liquid is cooed to a great extent below its freezing point. Then fuel burning may pose a problem.

dhayanandhan.s,

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INDIA

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