Is the Space Hose a Viable Solution for the N-Prize Challenge?

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The discussion centers around a proposed low-cost Space Tower concept called the Space Hose, which utilizes a lightweight hose made from PE foil to generate lift through frictional forces from flowing air. The idea aims to address the N-prize challenge of launching a 9.99-gram satellite into orbit for nine days while adhering to a strict budget. Participants debate the feasibility of maintaining a satellite at 100 km altitude, with concerns about achieving the necessary orbital velocity and the structural integrity of the hose under such conditions. The conversation also touches on the definition of orbit and the challenges of stability and pressure at high altitudes. Overall, the concept raises intriguing questions about innovative approaches to space launch technology, despite significant technical hurdles.
  • #91
N-Prize said:
That still leaves the option of rewording the rules to demand that something stays up there by means of orbit "or other means".
Yes, though let's note that the space hose is in every way equivalent to a standard-issue space tower. The fact that the last inch or so of the space hose is gaseous rather than solid is irrelevant to the rules.

i.e. as soon as you allow the space hose, the door is open for any space tower.


And once the door is open for space towers, you might as well just drop the whole "reaching orbital speed" requirement altogether. Any entrant who has a choice of winning the prize by building a tower rather than building an orbital launch platform, is going to build the tower.



N-Prize said:
You may find that you can play with more than £999.99, especially if the hose can be wound in and re-deployed (what goes up should come down, right?)

Seems to me one solution could be to rewrite the rules to include multiple trips rather than just the one, then set the cost to cover the total. That way, entrants might come up with ingenious ways to re-use components to keep costs down in bulk. But that might be whole other contest...
 
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  • #92
well, we/Paul could simply make an NT-prize to build a 100km Tower within the budget able to lift at least 9,99 gram - then the disussion would be over ;-)

The reason why Paul created the prize was to enforce creativity and not demotivate it by the prize rules. So I simply decided to take myself this freedom and asked him if it meets the spirit.

There was no intention from my side to cheat, use a loophole or something, or rewrite the orbit definition (but there is still some room for interpretation - but let's NOT start this discussion again)

PS: If I would actually win I would donate the money to a children care organisation anyway.

gutemine
 
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  • #93
gutemine said:
well, we could simply make an NT-prize to build a 100km Tower within the budget able to lift at least 9,99 gram - then the disussion would be over ;-)
Pretty much, yep.

Unfortunately, that is the almost inevitable outcome if they accept the space-hose as an entry. (Because the rules will need to be rewritten to eliminate the word 'orbit'.)

gutemine said:
The reason why Paul created the prize was to enforce creativity and not demotivate it by the rules. So I simply decided to take myself this freedom and asked him it it meets the spirit. There was no intention to cheat or something.
Good lord, no one thinks you were trying to cheat.

In fact, it is your responsibility as an entrant to push the rules as hard as you can. The challenge set out by the N-prize is huge; it will not be won without some very creative thinking such as this.

gutemine said:
PS: If I would actually win I would donate the money to a children care organisation anyway

Or perhaps the local space agency?
 
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  • #94
Look, I've read the Inflatable Space Tower patents and also their papers and presentation at the space elevator conference.

They spent quite some money and time on patenting it, but they still missed the point that air provides an easier method of producing lift then filling inflatables with helium (which runs out of buoyancy too early) or build them huge to withstand the pressure. So the N-prize limit was exactly the driver to TRY to avoid this problem - If it works we owe Paul a lot - just by pushing people into the desert and let them dig for water where nobody tried before.

I personally decided just to have fun and find out if it works but make the space hose idea public so that it is not patentable by anyone anymore !

And I'm not looking for fortune and fame either - so don't think that I try to market or sell you the space hose idea. I just like it (like my other children) and want it to prosper.

PS: And as I already said - if somebody is willing to try it out - I'll bring the beer.

gutemine
 
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  • #95
DaveC426913 said:
Unfortunately, that is the almost inevitable outcome if they accept the space-hose as an entry. (Because the rules will need to be rewritten to eliminate the word 'orbit'.)

No, they won't. The N-Prize organizers have already spoken on this matter (you can't have missed this fact, as it's been mentioned several times in this thread).

You continue to confuse the difference between free-floating orbit and anchored orbit. To illustrate, let's take the example of an equitorially-anchored (tethered) space station at 42,164 m semi-major axis with a space-tether counter-weight of x kg at y km distant (immaterial to my point). Is it in "orbit" according to your definition? Certainly. In fact, according to your definition, it's in geosynchronous orbit. Mine too..

Let's move the counterweight out a bit while moving the space station in just one foot. According to your definition, it's no longer in "orbit."

Phooey!

Put simply, the N-Prize organizers came up with their own definition of "orbit" and have defendend their position, along with the funds. If you'd like to come up with your own definition, just start your own competition and front your own funds. :)

Put simply, your definition involves only that of a free-wheeling, totally untethered body. Meanwhile, the N-Prize folks have already ruled gutamines entry complied with their rules. They don't want anything "attached," but they've already ruled that balancing on a column of air is not "attached."

So who are you really, Dave? Are you the N-Prize coordinator himself? If so, please put up. If not, I've had it up to hear with your attempts to usurp the response of the N-Prize coordinators in terms of denouncing his idea based on your very narrow concept of the term "orbit."

Good-day.

- Mugs
 
  • #96
well, the real problem with all orbit definitions is that they were not specified with any tower/elevator construct in mind. Some contain gravtiy and/or speed - some do not, etc.

If you build the classical 72.000km space tower with a counterweight asteroid at the end then only about 1 inch in the middle (which would not even need to be the mass center) would actually be in orbit if you hammer the definitions in stone - because only this inch would rotate exactly with the obital speed at 36000km of 7,something km/sec.

The part below would be too slow, and the part above would be too fast and actually fly away without the tether or the tower.

BTW if there would be people having to stand on the counter weight asteroide, they would need to do this on the Earth facing side - or they would be in big problems (calculate the acceleration then and then decide if it is a comfortable space)

My suggested 100km Space hose would have the same speed profile then the first 100km of the 72000km Space Elevator - so where is the point not to accept it as an achievment (in case it would work) and an approach worth discussing and analyzing.

The nice thing about a real orbit is that you are weightlessness - but this is not a must to be in space, and can be also a pain - so why thinking bad about avoiding it !

So can we please keep this orbit discussion aside for the moment - believe me if such a tower is really built the orbit definitions will be adapted, optimized or what so ever - and that's also what Paul suggested - which I think is a pretty clever approach to maybe get the wanted results of his N-prize competition to find an ultra cheap way to space and discuss the solution later (with or without prize money paid out is not even the point).

gutemine
 
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  • #97
gutemine said:
well, the real problem with all orbit definitions is that they were not specified with any tower/elevator construct in mind. Some contain gravtiy and/or speed - some do not, etc.

If you build the classical 72.000km space tower with a counterweight asteroid at the end then only about 1 inch in the middle (which would not even need to be the mass center) would actually be in orbit if you hammer the definitions in stone - because only this inch would rotate exactly with the obital speed at 36000km of 7,something km/sec.

The part below would be too slow, and the part above would be too fast and actually fly away without the tether or the tower.

I think you're missing the point here. The launch system is not constrained by any but the broadest terms (such as budget). Nobody cares what the launch system does.

The 72,000km tall space elevator is only the launch system for the satellite. The point of the 72,000km tall space tower is that is has the ability to launch the satellite. Which is all the N-prize cares about.
 
  • #98
gutemine said:
My suggested 100km Space hose would have the same speed profile then the first 100km of the 72000km Space Elevator - so where is the point not to accept it as an achievment (in case it would work) and an approach worth discussing and analyzing.

... an ultra cheap way to space...

Because it's not "a way to space". Sitting on top of a very tall tower is not the same thing as being in space, just like pushing your car out into the driveway is not the same thing as putting an engine in it and driving it to the racetrack.

What advantages specifically (other than access to partial vacuum) are conferred from being at the top of a tall tower?


Orbit is not about weightlessness. Orbit is
1] freedom to roam over the Earth as needed, fuel free
2] the doorway to leaving Earth altogether.
 
  • #99
Space is a location - not dependent on the speed !

I'm in space if I'm 70.000km away from Earth and don't have any speed at all. Then I' will spend the next hours/days to fall back to Earth - but I'm definitely in space!

If you are in Paris it doesn't make a difference if you are on top of Eiffel tower, in a cab or a TGV entering Gare del'Est or sitting at the Seine and eating a baguette.

If you are in London (and have not even passed the Channel) you are definitely not in Paris !

This starts to become almost a fight comparable to geocentric vs. holocentric. If you are standing still compared to Earth and are 100km high above you still orbit the Sun at amazing speed, and together with the sun you orbit the milkieway at another pretty high speed.

BTW Einstein spent quite a time of his life to explain that motion/time and speed dramatically depend on the observing point.

If I would follow this argument landing on the moon would have been a waste of time and the real achievment would have been Apollo 8 which orbited the first time the moon (something the Russians achived before if I remember right)

And orbit is also a lock-in as stiting on a tower - it costs fuel and time and needs acceleration to change height, direction,... try to make a polar orbit out of an equatorial - then you will know.

I have now written already 3 times that if air flow friction works to lift and keep a tower up to 100km it would work also for 36000km - and then you would have your orbital speed too.

Let's try it from the human view point - as a current space torist I have to pay about 20-30 Millon $ to see the Earth from 350km (=ISS) from space (orbiting, I know). Do you think the people paid for the orbiting part/velocity - or for the view ?

If a space hose could offer a launch vehicle beeing able to bring you to space (as a loation !) for an infinitely time (if you stay on top) with a much smaller budget you think this is something nobody would care ?

If you can read everywhere that the current space elevators and towers have a problem because of no material supporting them, and you then find a way where a continuous support reliefs this material problem - then this is useless, because somebody planns to build only a 100km prototype ?

Maybe I simply misunderstand your point and apologize if my reply sounds impolite, but I really have a porblem understanding why this part is so important for trying out something and get some proove of concept by competing in a Prize which will get nobody rich ?

gutemine
 
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  • #100
mugaliens said:
No, they won't. The N-Prize organizers have already spoken on this matter (you can't have missed this fact, as it's been mentioned several times in this thread).

You continue to confuse the difference between free-floating orbit and anchored orbit. To illustrate, let's take the example of an equitorially-anchored (tethered) space station at 42,164 m semi-major axis with a space-tether counter-weight of x kg at y km distant (immaterial to my point). Is it in "orbit" according to your definition? Certainly. In fact, according to your definition, it's in geosynchronous orbit. Mine too..

Let's move the counterweight out a bit while moving the space station in just one foot. According to your definition, it's no longer in "orbit."

Phooey!

Put simply, the N-Prize organizers came up with their own definition of "orbit" and have defendend their position, along with the funds. If you'd like to come up with your own definition, just start your own competition and front your own funds. :)

Put simply, your definition involves only that of a free-wheeling, totally untethered body. Meanwhile, the N-Prize folks have already ruled gutamines entry complied with their rules. They don't want anything "attached," but they've already ruled that balancing on a column of air is not "attached."

So who are you really, Dave? Are you the N-Prize coordinator himself? If so, please put up. If not, I've had it up to hear with your attempts to usurp the response of the N-Prize coordinators in terms of denouncing his idea based on your very narrow concept of the term "orbit."

Good-day.

- Mugs

If you were to tether a space station, it is classed as in geosynchronous orbit so long as it maintains orbital velocity and holds it's position above the earth.

By having the counterweight, you shift the CoG to a point central to the both units. It is this point that must remain at the geosynchronous orbit altitude (36000km) and the velocity must be that of a geosynchronous orbit

If you think of it, the tethered weight would be traveling far slower than the station due to having a shorter orbital period (height within 36000km and station outside of). It is the point at 36000km that needs to be at geosynchronous orbital velocity and the CoG of the two counteracting objects.

Even if you forget geosynchronous orbit, as long as both units move as one, they would require the correct orbital velocity for whatever altitude you set them at. If you don't overcome gravity with a velocity greater than that of geosynchronous, you will fall to Earth (when orbit < 36000km) and if your velocity is greater than that of geosynchronous you will slingshot away (for an orbit > 36000km). The lower altitude object travels slower than required orbital velocity and the higher object travels faster than required orbital velocity. They counteract each other and provide a stable orbit, with a point central to both (the effective CoG) traveling at the correct orbital velocity for the altitude it is holding.

You cannot separate the two elements because they function as one. Individually, if you cut the tether, without the counterweight, the station would require a different velocity in order to maintain it's altitude and position over the earth.

When it comes to 100km, there is no such thing as free floating orbit. If you do not maintain the required orbital velocity around earth, the satellite will be pulled towards the planet. Holding something on top of a tower, you have simply extended the Earth's surface to that altitude and placed something on top. Not an orbit by any means.

Anyway, I think this point has been hammered into the ground now and we should perhaps concentrate on the physics of the device?

EDIT: sorry for so many corrections, completely misread your post the first time.
 
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  • #101
jarednjames said:
Anyway, I think this point has been hammered into the ground now and we should perhaps concentrate on the physics of the device?

I like this sentence :-)

Did you have already some progress on (re-)checking the structural strength needed ?

I already shared all the data and calculation I have on this subject - which doesn't look that bad in my understanding, but at the moment it is just patched together out of classical engineering formulas and some assumptions.

If PE foil combined with Dyneema can hold all possible stresses (pressure AND pull) put onto the structure because of it's strange diameter to length to thickness to weight ratio (hopefully my English teacher will never see this sentence) this would be already some kind of confirmation to proceed with this concept.

As the slides say - I hate to wait for carbon nano tubes !

On the other hand if the physics would not work to provide the lift force and handle the gas flow this would be still only half of the lunch.

So we would need urgently somebody also beeing able to put some light on the suggested gas dynamics - If nobody here can help out on this - what would you suggest ?

gutemine
 
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  • #102
I have the dimensions from your slides, can you provide me with a link to the exact materials you plan to use (or provide me with some datasheets on them) so I can be sure I'm looking at the right stuff?
 
  • #103
jarednjames said:
I have the dimensions from your slides, can you provide me with a link to the exact materials you plan to use (or provide me with some datasheets on them) so I can be sure I'm looking at the right stuff?

For Dyneema Material you should start with the Manufacturer:

http://www.dyneema.com/en_US/public/dyneema/page/about/Material.htm

For getting the strength and weight numbers I checked the (German) Wiki:

http://de.wikipedia.org/wiki/Dyneema

But if you Google with Dyneema and strength the numbers should be easily verifyable.

Also the English Wiki on Dyneema contains links to some tearing test studies.

http://en.wikipedia.org/wiki/Ultra-high-molecular-weight_polyethylene

And this one is also a good source if you look for material data:

http://www.matbase.com/material/fibres/synthetic/dyneema/properties

For PE foil you can check the homepage of some of the manufacturers which are producing such PE foil hoses as cheap packaging material.

I got the strength values again from the (German) Wikipedia:

http://de.wikipedia.org/wiki/Polyethylen

or here:

http://www.matbase.com/material/polymers/commodity/hdpe/properties

Lots of PE foil manufacturers also give the tearing strength and weight numbers and for PE-HD the 20N/mm² for tearing strength we should be on the low side. For plain/cheap PE 10N/mm² is more realistic.

http://www.matbase.com/material/polymers/commodity/ldpe/properties

So in general the used numbers should be in line to what they advertise :-)

gutemine
 
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  • #104
gutemine said:
Space is a location - not dependent on the speed !
So is your driveway, but it's a looooong way from pole position at the racetrack.

gutemine said:
I'm in space if I'm 70.000km away from Earth and don't have any speed at all. Then I' will spend the next hours/days to fall back to earth
It takes less than an hour. And much of that is in pretty thick atmo.
gutemine said:
- but I'm definitely in space!
Actually, no. You're surrounded by atmo.




gutemine said:
If you are in Paris it doesn't make a difference if you are on top of Eiffel tower, in a cab or a TGV entering Gare del'Est or sitting at the Seine and eating a baguette.
If you are in London (and have not even passed the Channel) you are definitely not in Paris !
Terrible analogy.
gutemine said:
This starts to become almost a fight comparable to geocentric vs. holocentric. If you are standing still compared to Earth and are 100km high above you still orbit the Sun at amazing speed, and together with the sun you orbit the milkieway at another pretty high speed.
Which I am still doing on the ground in my bed, asleep. You're really losing perspective now.

gutemine said:
If I would follow this argument landing on the moon would have been a waste of time and the real achievment would have been Apollo 8 which orbited the first time the moon (something the Russians achived before if I remember right)
No, That is quite an achievement. It is out of Earth's very deep gravity well.
gutemine said:
And orbit is also a lock-in as stiting on a tower - it costs fuel and time and needs acceleration to change height, direction,... try to make a polar orbit out of an equatorial - then you will know.
The amount of energy required to get from 0 to 100km with zero residual velocity is vanishingly small compared to teh amount of energy required to get anywhere beyond that that is not simply on top of a taller tower.

gutemine said:
If a space hose could offer a launch vehicle beeing able to bring you to space (as a loation !) for an infinitely time (if you stay on top) with a much smaller budget you think this is something nobody would care ?
Absolutely they would care.

I'm not trying to discourage you. I just think it requires some perspective.

gutemine said:
If you can read everywhere that the current space elevators and towers have a problem because of no material supporting them, and you then find a way where a continuous support reliefs this material problem - then this is useless, because somebody planns to build only a 100km prototype ?

Maybe I simply misunderstand your point and apologize if my reply sounds impolite, but I really have a porblem understanding why this part is so important for trying out something and get some proove of concept by competing in a Prize which will get nobody rich ?

I agree it would make a great protoype and a great achievement.
 
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  • #105
DaveC426913 said:
It takes less than an hour. And much of that is in pretty thick atmo.

Actually, no. You're surrounded by atmo.
Maybe we have a misunderstanding here - I'm pretty sure that 70.000km away from Earth I will not be surrounded by air.

Even in 100km pressure is down to something 100Pa which is already pretty low. At 350km height (where ISS hangs around) it is down to something about 1Pa. The quality of such a vacuum is already pretty good.

Regariding the falling time from 70.000km the law about freefall goes like this:

s=gt²/2 then t= squareroot from 2s/g

For 70.000 km this gives (yes, I know that g is not 9,81 anymore that far out) 3777sec - so I agree with the <1h and the frist part of the sentence (sorry fro not doing the math when I replied) but speed is:

v=squareroot from 2gh which gives for 70.000km 11721m/sec or 42189km/h on the ground- which means you will spend only a few seconds in what you could call an atmosphere - while you are probably burnt to ashes - so 'much of that' is a kind of heavy understatement.

But it looks like we have to break the gasdynamics elephant down a little bit for eating it:

Question 1:

Is the gasdynamics calculation of moving 1m³ from sea level to 100km right (using the known pressure and temperatures at these 2 points and the ideal gas law to calculate the Volume) so that it expandes that heavily as the slides suggest ?

pV/T = constant for 1m³ at 20 degree Celsius means 100000*1/293=341 the same for 100Pa at 100km and T is -90 Degree Celsius would need a V of 625m³ (!) to give the same number: 625*100/183=341

PS: If somebody wants to watch Paul's Interview on the N-prize:



gutemine
 
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  • #106
gutemine said:
Maybe we have a misunderstanding here - I'm pretty sure that 70.000km away from Earth I will not be surrounded by air.
Wait. When you say 70.000km you mean 70, right? Not 70,000? Why would we be talking about 70,000km altitude?


gutemine said:
v=squareroot from 2gh which gives for 70.000km 11721m/sec or 42189km/h on the ground- which means you will spend only a few seconds in what you could call an atmosphere - while you are probably burnt to ashes - so 'much of that' is a kind of heavy understatement.
I don't think that's the case. I don't think you're accounting for terrminal velocity which will lengthen the lower half of the trip. There will be no terminal velocity for the first part of the trip, since the atmo is pretty thin. You'll fall pretty fast; it is only when you hit the thicker atmo that you'll slow down. I don't have any calcs to show but I think the bulk of the fall will be spent in the lower half of the 100km.

BTW, I also don't think there's much burning to a crisp happening. Spaceships use heat shields because they're slowing from 17,000mph, not from a few hundred mph.




Anyway, this is all beside the point. It is derailing you from your R&D for the space hose.

Carry on.
 
  • #107
My original Post was 70000km (and you even citated it with km). The number came up because of the 2x36000km of the space elevator with asteroid counterweight. If you are there without speed you are still in space (at least for the next 50 something minutes) but not in orbit.

And yes, the Paris example was a bad one - but it was just to illustrate that if you are at a place the speed is not the point (unless you want to know how long you will stay there).

Anyway, let's see if we can fix and clarify also the other questions.

Because I still have a huge problem understanding what would go on in such a long hose. All the typical formulas and examples are either isobar (which would be the hose laying on the ground, but then you don't have gas expansion due to decreasing pressure) or frictionless (expansion from a pressurized boiler to vacuum (to calculate maximum blowout speed)

If you mix up all these you endup with the concept I proposed, but I'm not sure if I mixed it right.

So probably looking at the ingredients/formulars before mixing them at all is not such a bad idea :-)

My real problem is that I'm already pretty late for the N-prize and unless the concept hasn't been verfied at least to some extent I would not send the application form and waste Paul's and your time.

On the other hand if it is feasible and the available/suggested materialy can do the job (not orders of magnitudes away in strenght or available length,...) I will definitely proceed - just for the fun of it (as Paul states in his interview on YouTube).

PS: Paul signs his e-mails as Chief Optimist - maybe I'm the CTO (Chief Technology Optimist) but then I need Pessimists to do a good job.

PPS: Space ships are entering the atmosphere tangentially - so the time to heat up is longer. If you go trough vertically probably no heat shield would be able to do this (better ask a meteor) and the negative acceleration would be a nightmare and probably break you also.

gutemine
 
  • #108
Just a thought, a firehose is made of a strong material and is subjected to high pressure water being pumped through it. They use two people to control it. If they let the hose go, it swings wildly around.

Why wouldn't this be the case with the space hose? Unless the hose is kept perfectly vertical any lateral movement would result in this wild swinging motion. The higher the flow velocity in the hose, the worse the problem.
 
  • #109
jarednjames said:
Just a thought, a firehose is made of a strong material and is subjected to high pressure water being pumped through it. They use two people to control it. If they let the hose go, it swings wildly around.

Why wouldn't this be the case with the space hose? Unless the hose is kept perfectly vertical any lateral movement would result in this wild swinging motion. The higher the flow velocity in the hose, the worse the problem.

This works also with a garden hose and is the example how you usually explain to kids how rockets work - the momentum of the water leaving the hose creates a push back force on the nozzle and hose in reverse direction of the outflowing water (=backwards).

BUT If you put an steel plate 10cm upfront of the nozzel which is connected via steel wires to the nozzle and turn on the water the water and its momentum will be going circular from the hose and hence equal itself out. Then the firemen could hold the hose with a single hand (but it would be hard to put out the fire)

If you use a cone instead of a plate so that the water is reflected slightly backwards on the fir men - then besides that they get wet the hose will be pulled out of their fingers if the don't hold it properly.

Look at the 'design thoughts' slide - this is exactly what the diffusor on top should do - recovering some of the pressure of the outflowing air and changing its direction to blowing slightly downwards to get a pull on the hose instead of a push (and hold its own and the N-SAT weight too as an option). Even the famous bouncing ball in a fountain works that way by using the impact pressure to hold their own weight.

You can even use this pull force for erecting the hose and to stabilize the whole thing when upright. Such a downward blowing diffusor is the pneumatic replacement for the top counterweight suggested for a standard space elevator.

If the diffusor would be held vertical by a static pendulum mass underneath and the diffusor plate beeing not fixed (or a gyroscope - because the diffusor could be also a propeller mass rotating in the outflowing air and maybe even produce electricity). Then as soon as the hose bows to one side the diffusor plate will be lifted on this side and allows to blow out more gas on this side, which will then create a backword force moving it upright again until the momentum is balanced again.

The force which acts on a rocket is:

F=A*density*v²

Meaning if the hose would be very short then near the ground the force resulting out of the asumed possible flowspeed of 3,5m/s would be (if the blowdown area is equal to the hose area to prevent pressure/speed changes):

F=0,05*1,29*3.5²=0,79N - enough to balanace the weight of the suggested N-SAT

What scares me a little bit is that because of ideal gas law if the volume on the top should be is 625x higher and hence the density 625x lower (see one of my previous replies on this),

BUT because of continuity law this would mean that if the diameter of the hose is unchanged the air speed could be up to 625 times higher, meaning 3,5x625 which gives approximately 2200m/sec (30% of cosmic speed) ??

Because the force goes with the square of the speed this would mean that the theoretically available force on top from blowing downwards could be *625²/625=625x higher =493N - which would be sufficient to hold 50kg ?!

But changing the direction of the outflowing air to side/downwards also recovers some of the cinetic energy as pressure on the diffusor, so the exact calculation probably is not that simple

This is the reason why the slides say that at 100km the diffusor should blow down only slightly :-)

Put this probably would be question 3) - as soon as we have a decision on question 1) and because we also need to find out what 2) the friction does to the airflow.

gutemine
 
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  • #110
Hi !

Just a small update:

With the re-calculation of the previous replies I found an error in the presentation on the first page:

The Line with the ideal gas formula between bottom and top should read:

Q on top =(100000*0,17/293)*183/100 = 106,18 m³/s

This means when blowing out trough the same diameter then on the bottom (0,05m²) would give only 2253,16m/sec theoretical blowout speed not the 5367m/sec on the slides.

This would be about 30% of the first cosmic speed needed for orbit which still seems to be pretty unrealistic. This means the Diameter of the Blowout nozzle would need to be changed by a factor of the squareoot of 3 or the blowing speed at the bottom changed to 10m/s to reach 7400m/sec in case this would be needed.

But the real speed gradient is still under discussion, I known :-)

Thanks for pointing out this error !

gutemine
 
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  • #111
gutemine said:
well, the real problem with all orbit definitions is that they were not specified with any tower/elevator construct in mind. Some contain gravtiy and/or speed - some do not, etc.

If you build the classical 72.000km space tower with a counterweight asteroid at the end then only about 1 inch in the middle (which would not even need to be the mass center) would actually be in orbit if you hammer the definitions in stone - because only this inch would rotate exactly with the obital speed at 36000km of 7,something km/sec.

And that inch would be 35,786 km above the Earth's surface, right? With an orbital semi-major axis of 42,164 km?

gutemine said:
Space is a location - not dependent on the speed!

Bingo. It's a fact which you get, I get, NASA gets*, Rutan's SpaceShipOne got by winning the $10 Million http://en.wikipedia.org/wiki/Ansari_X_Prize" , and which the N-Prize organizers get as evidenced by their acceptance of your idea.

*13 of the flights (by eight pilots) met the USAF spaceflight criteria by exceeding the altitude of 50 miles (80.47 km, 264,000 ft), thus qualifying the pilots for astronaut status.

There is a huge difference between an orbit and a zero-g orbit. All aspects of a space tower, pos-g to neg-g areas will be in orbit, while only free-floating satellites are in zero-g orbit.

I haven't a clue as to why anyone, particularly a scientist, is incapable of fathoming this concept when so many scientists and engineers before him/her over the last 48 years of space travel have accepted it completely.

If anyone continues to harp on the issue, I suggest you ignore them.

In the meantime, press on! You're doing a great job. :)
 
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  • #112
mugaliens said:
*13 of the flights (by eight pilots) met the USAF spaceflight criteria by exceeding the altitude of 50 miles (80.47 km, 264,000 ft), thus qualifying the pilots for astronaut status.

I haven't a clue as to why anyone, particularly a scientist, is incapable of fathoming this concept when so many scientists and engineers before him/her over the last 48 years of space travel have accepted it completely.

Just because it's in space, does not make it in orbit. That is the key difference. If the N-Prize said that they simply had to put something in space, then boom he's there. But the rules are specific in that it must orbit 9 times. Definitions aside, in simple terms that means the satellite must remain in space (unattached to the tower) long enough to complete 9 rotations of the Earth's axis with at least 100km altitude (from sea level).

I've tried to drop the orbit issue about three times now and focus on the maths, but people just keep bringing it up again...
 
  • #113
jarednjames said:
If the N-Prize said...

They have said. Repeatedly. Gutamine has contacted them. They have responded.
 
  • #114
mugaliens said:
Bingo. It's a fact which you get, I get, NASA gets*, Rutan's SpaceShipOne got by winning the $10 Million http://en.wikipedia.org/wiki/Ansari_X_Prize" , and which the N-Prize organizers get...
Um, you do recognize that the difference between the N and X prizes is at the X prize was to get into space and the N prize orbit, right? Thus this space hose idea would satisfy the X prize, but not the N prize.
...as evidenced by their acceptance of your idea.
Clearly, they were deceived: they were not told that the object is intended to be supported by the tower.
If anyone continues to harp on the issue, I suggest you ignore them.
Dave keeps harping on it because it is a simple issue that several people are blindly ignoring. He feels the need to correct people when they are wrong, in keeping with the spirit of the forum.
 
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  • #115
DaveC426913 said:
Update

You will be astonished as I am.

I have been in contact with the N-prize judge myself. Here is the transcript:


Q: Hello. Can you please define your use the the term 'orbit'.

For example, some who might wish to interpret your rules as liberally as possible might consider a satellite sitting on top of a 100km tall tower to be in "orbit" (since it will ultimately go around the Earth once every 24 hours). Would this qualify?
A: As long as it's at 100km without touching anything else, it would qualify. ... So, if you had a "tower" but could somehow hold the satellite there at the top without touching the tower itself, that would be OK.

Q: " without touching anything else": does that include, say, a column of air?
A: Ah, yes, could be. As for "touching" - I think that's OK. ... the air pressure at the "orbital" point would be very close to the external pressure at 100km anyway, so no problem.

Q: This tower does not move, which means the satellite will *not* orbit the Earth 9 times (one of the N-prize requirements) unless you very liberally allow Earth's own daily rotation to count. Does that still qualify?
A: As for "orbits" - the Earth's own rotation does count, so as long as it stays up for 9 days...

:eek:

It would appear that the N-prize judge is perfectly happy to allow this non-orbit to qualify, despite the requirement in the rules.
I'm not so sure I agree, Dave - you were trying to constrain your questions to the context of this thread and as a result there are some physical impossibilities represented there. The first answer you got is particularly nonsensical. It's possible that the person you were talking to doesn't understand the concept of an orbit very well (who runs this thing anyway?), but when push comes to shove, I'm sure the letter of the law will rule.
 
  • #116
mugaliens said:
They have said. Repeatedly. Gutamine has contacted them. They have responded.

Yes, and as per the posts on this very forum, it has been made clear. The satellite cannot touch the tower = orbital velocity required. So far no way to achieve this.

There is potential that the tower idea with the satellite supported on a column of air will be accepted into the competition, but nothing set in stone and it is subject to the approval of all other competitors (as the N-Prize representative pointed out, it's not just the judges who decide). I'm sure they'll have something to say about it.

Regardless, I think we should just help with the calculations and let this slide.

EDIT: russ, you may want to read the N-Prize posts directly from the organisation itself. They clear things up far better. (https://www.physicsforums.com/showthread.php?p=2885614#post2885614)
 
  • #118
russ_watters said:
Thanks, I didn't see that we had an N-Prize organizer here.

He arrived about six hours after I started bombarding him with my requests for clarification... :wink:
 
  • #119
russ_watters said:
Thanks, I didn't see that we had an N-Prize organizer here.

Hiding behind a name like N-Prize, he could have fooled anyone :biggrin:
 
  • #120
Honestly Dave, you're a minute ahead of me on every bloody post! :cry:
 

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