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The Space Hose

by gutemine
Tags: hose, space
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mugaliens
#19
Sep13-10, 04:07 AM
P: 595
gutemine, I read through you posts and slides. Your proposal meets the N-prize rules. In summary, the object rides the moving column of air to the 100 km point, where it exits, and is thus outside, but remains attached. Technically, it's in geostationary orbit. Nine days later it's completed 9 orbits.

I do wish people would stop focusing on the rules and respond to your question of whether or not it's feasible. I'm an aero guy, and your numbers look ok to me, but it's been decades since I crunched fluid flows.

My concern is the stability of column in turbulent flow. This video shows what usually happens, although your dynamics are somewhat different (higher pressure, a diffuser/thruster at the top...) Obviously the column of air will loose pressure as it rises, just as does the atmosphere.

Also, I don't recall your final numbers on internal pressure, but if we assume it's at twice ambient pressure all the way to the top, however, your 10" column of air will itself weigh 2,309 lbs, though half will be supported by ambient, which leaves us with 1,154 lbs of additional mass to support. That'll be supported by the increased internal pressure, of course, but the bag will have to support 2 ATM along its entire length.

I'd say give it a trial run with perhaps a 500' column and see how it behaves.
russ_watters
#20
Sep13-10, 05:30 AM
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Quote Quote by mugaliens View Post
gutemine, I read through you posts and slides. Your proposal meets the N-prize rules. In summary, the object rides the moving column of air to the 100 km point, where it exits, and is thus outside, but remains attached. Technically, it's in geostationary orbit. Nine days later it's completed 9 orbits.
No, "technically", it is sitting on top of a tower. It is not in orbit.
russ_watters
#21
Sep13-10, 05:33 AM
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Quote Quote by mugaliens View Post
gutemine, I read through you posts and slides. Your proposal meets the N-prize rules. In summary, the object rides the moving column of air to the 100 km point, where it exits, and is thus outside, but remains attached. Technically, it's in geostationary orbit. Nine days later it's completed 9 orbits.
No, "technically", it is sitting on top of a tower. It is not in orbit.

When something is in orbit, there is no external force holding it up - there is only gravity pulling it down.
gutemine
#22
Sep13-10, 05:35 AM
P: 59
Maybe let's use a neutral example to end the discussion about orbit:

For thousands of years mankind accepted the rule that water is not able to flow uphill. Then Achimedes invented his screw. You could argument that now the water is pumped, but it definitely is a continuous upwards flow. So maybe Achimedes would not have gotten any prize money either, but that wouldn't have made his invention one inch smaller.

Regarding the air pressure weight - that's the good thing about pneumatics - the weigth of the air is not a problem (if there is not pressure surplus) because the hydrostatic pressure is the same inside and outside the hose if there is no air flow. Which means there is nothing the hose needs to balance with its strength. Which is especially true if the hose is open on the other end (=top). On sea level air has a hydrostatic pressure of approx 100000N/mē which would make even Atlas crack if he would have to hold it on his shoulders. But there is no problem with this, because our body is under the same pressure and feels pretty comfortable with that. A hose has the same pressure relief, so you may only need to hold the surpressure of the resistance pressure 'loss' - but I'm not even sure about this, because it is a flexible hose and not a fixed pipe.

The slides contain also the worst case pressure needed if the hose is closed and all the weigth at the top (about 0,6 bar) which is nothing modern materials would not be able to hold (not the thin PE foil, I agree, but the suggested Dyneema string srengthening like the Polyamid in your garden hose should be sufficient). The formular to calculate the needed strength of the walls of a tank is pretty simple and easy to use. And the diameter is not the optimization point - you get linear force increase, but also linear weight increase when the pressure and wall thickness is the same.

The 10" were only to make it within the N-prize budget, a real space hose for doing something usefull would be either bigger or a straw pack of such hoses (BTW I would prefere the later)

Maybe I should ask the question on my math more generic:

If I blow trough a very long hose from 1 bar into vaccum (and are ignoring friction), what pressure will the hose (not a fixed wall pipe) have ?

I already know that speed on the vacuum side will not be infinite (I think it is about 740m/sec because of ideal gas law in case of normal room temperature in the vacuum, real case calculation at -90 degree Celsius is in the slides)

Then you make the hose go upwards, and the hydrostatic pressure adds, but gets balanced from outside as already described.

Then your add friction and what pressure do you get then ?

gutemine

PS: If I have a rocket with enough fuel to continuously blow also downwards I can fly around earth as slow as I want at any height - and you want to tell me that this is suddenly not an orbit ? If yes, then this is OK with me - no problem from my side !

PPS: An electron is also orbiting the atom core, and the orbital 'speed' is determined by the electromagnetic forces (and some quantum mechanics so it is not really speed) and not the gravitational one. This is why lots of orbit definitions even lack the word gravitation

Quote Quote by russ_watters View Post
A particular altitude is not part of the definition of an "orbit".
The N-prize rules are asking for the 100km height to reach 'space' - in general you are right, otherwise cyling earth with a bicycle 9x would also get you the prize money, or simply waiting for 9 days. - BTW I liked the space garage approach. And thanks for the offered help on the strength calculation - as soon as we agree on the pressure gradient in the hose I will have to re-do that.
DaveC426913
#23
Sep13-10, 12:31 PM
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Quote Quote by mugaliens View Post
gutemine, I read through you posts and slides. Your proposal meets the N-prize rules. In summary, the object rides the moving column of air to the 100 km point, where it exits, and is thus outside, but remains attached. Technically, it's in geostationary orbit. Nine days later it's completed 9 orbits.
Yeah, mug where are you getting this from? It is not in orbit at all.

By your logic, I could sit in my basement, suspending a pingpong ball using my vacuum cleaner, and claim, not only that it is in orbit, but that it will orbit the Earth every 24 hours.
By your logic, a hover mower, which rides on a cushion of air, is in orbit.


That's ridiculous.
DaveC426913
#24
Sep13-10, 12:34 PM
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Quote Quote by gutemine View Post
PS: If I have a rocket with enough fuel to continuously blow also downwards I can fly around earth as slow as I want at any height - and you want to tell me that this is suddenly not an orbit ? If yes, then this is OK with me - no problem from my side !
Correct. That is not an orbit.

See above examples of other comparable setpups that are also not orbits.

And the N-prize judges will agree. I guarantee it.




Quote Quote by gutemine View Post
PPS: An electron is also orbiting the atom core
No it isn't.

Quote Quote by gutemine View Post
The N-prize rules are asking for the 100km height to reach 'space' - in general you are right, otherwise cyling earth with a bicycle 9x would also get you the prize money, or simply waiting for 9 days. - BTW I liked the space garage approach. And thanks for the offered help on the strength calculation - as soon as we agree on the pressure gradient in the hose I will have to re-do that.
Your idea does not meet the criteria for orbit. Ask the judges at N-prize.

Do this before putting any more time into your proposal.
gutemine
#25
Sep13-10, 12:51 PM
P: 59
Well, I already checkd with Paul (who IS the 'jury' - because he invented the prize and took care of the funding). He agreed that my proposal meets the spirit of the competition and I would be allowed to partizipate with this approach. And yes, I have sent him the slides and he said the space hose would qualify as a launch device to space!

He sent me the forms already to officially join - I just would need to fill them out, sign them and send back to officially participate. That doesn't mean that I could make and win the prize money - but the other competitors have pretty the same problem. If their broadcasting device fails and they could not proove the 9 orbits they would not get their prize money either - even if their N-SAT would perfectly orbit infinitely.

With the planned approach and materials I probably could do a 1-2km 'test flight' within a few weeks - 90% of the other partitcipants have not even an idea when they could do their first test flight. And if it would make only a few hundred meters - where is the problem - most of the home-brewn rockets have the same first launch (if they are lucky and make a lift-off at all)

I'm not planning to cheat and ask your for permission - I'm simply creative in solving the puzzle, and try to have fun while doing so.
I'm also trying to be honest and open minded by sharing my (bad) math and (weird) assumptions and ask clever people for feedback if and what I have done (awfully) wrong - to prevent missing something and waste all our time,

If I'm doing this already - then I'm simply sorry.

gutemine

PS: In your basement you could at least claim that you are orbiting the sun.

PPS: I just checked the orbit definition at the NASA Homepage (which in my understanding are pretty competent in this field):

An orbit is a regular, repeating path that one object in space (!) takes around another one.
And according to the NASA definition space starts at 100km above surface.

http://www.nasa.gov/audience/forstud...ature_5-8.html

And yes, later their explaination gets lost with orbital speed, and gravitational forces (which is OK with me) - but that doesn't change the basic words of their own definition. If I would follow your argument even a space elevator 36000 km (or even 2x) long with a geostationary counterweight would not reach orbit either because it is still connected to the planet (and the first 100km would move identical to my proposal).
DaveC426913
#26
Sep13-10, 01:07 PM
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Quote Quote by gutemine View Post
Well, I already checkd with Paul (who IS the 'jury' - because he invented the prize and took care of the funding). He agreed that my proposal meets the spirit of the competition and I would be allowed to partizipate with this approach. And yes, I have sent him the slides!
Your proposal does meet the criteria - because it contains a passage addressing horizontal velocity. Whether it addresses it realistically, on the other hand, is your problem, not his.

I am simply saying you'll have to get that part working. So far, it is just a single speculative passage in your notes - but that part is going to be by far your biggest challenge.

Again, I feel you're concentrating on pushing your racecar out of the garage. As for getting it moving toward the racetrack, your proposal merely says "there is the possibility that we may be able to put some sort of engine in it at some point in the future."


Quote Quote by gutemine View Post
I'm not planning to cheat and ask your for permission - I'm simply creative in solving the puzzle, and try to have fun while doing so.
I'm also trying to be honest and open minded by sharing my (bad) math and (weird) assumptions and ask clever people for feedback if and what I have done (awfully) wrong - to prevent missing something and waste all our time,
Yep. And we're giving you feedback about the missing piece.

I am trying to help, even if it risks discouraging you by having you see get some perspective on how far you need to go from here.

Don't discount that 'getting up to orbital velocity' requirement.
DaveC426913
#27
Sep13-10, 01:12 PM
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Quote Quote by gutemine View Post
...gets lost with orbital speed, and gravitational forces...
"...gets lost..."???

Quote Quote by gutemine View Post
. If I would follow your argument even a space elevator 36000 km (or even 2x) long with a geostationary counterweight would not reach orbit either because it is still connected to the planet (and the first 100km would move identical to my proposal).
The space elevator has that orbital velocity component. That is how it will impart it to the satellite (remember, the definitions for 'satellite' and 'launch mechanism' are carefully defined as separate in the N-prize rules).

Yours does not have that velocity component to impart to the satellite because it is 35,786-100 = 35,686km too short.
gutemine
#28
Sep13-10, 01:15 PM
P: 59
The mssing piece in my understanding is not the defintion of orbit - there are plenty.

Achimedes didn't concentrate on the meaning of the world flow either. He simply solved the problem to make it go upwards.

I already realized that I asked for too much at one time, so I tried to ask simple questions like 'what pressure will have a long frictionless hose blowing from 1 bar to vaccum' - and I didn't get any answer (yet).

If you want to eat an elephant you have to start somewhere, but it tastes the same no matter what his name was when he was alive (but don't tell me that we are trying to eat Dumbo - my childrean would be into tears)

And there are quite a lot of people enjoying getting their cars (and other weird devices) out of their garage on a daily basis.

If the space hose would work only for 1000m - this manmande built structure would be already higher then the tower at the gulf (with I am sure had a bigger construction budget) - and if it would be fun to try it, I don't have a problem to proceed.

To prevent misunderstandings - I'm not discounting or ignoring the orbital velocity component, the slides even suggest that with a de La Val nozzle in such a low pressure you maybe could even blow out a small object at orbital speed. But beeing 100km above surface (= space) already has a big schientific value (besides that you would NOT be weightless there which would make the stay probably even more comfortable if we would be able to put humans there this way), and could be used for things like low cost broadcasting, telemetry, air traffic control,...

In the halbakery I started already a thread that the real energy for 1kg beeing (!) in orbit is amazingly low (if you just add the needed height and kinetic energy). It is only a poor 32MJ more then on the surface (and yes, at orbital speed) - which is about the equivalent of burning 730g of Jet fuel. The energy is wasted in getting there, not for beeing there, so why not solving one problem after the other ?

And I already explained that if the friction = lift approach would work at 100km it maybe would work also up to 36000km

gutemine
russ_watters
#29
Sep13-10, 06:07 PM
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Quote Quote by gutemine View Post
Regarding the air pressure weight - that's the good thing about pneumatics - the weigth of the air is not a problem (if there is not pressure surplus) because the hydrostatic pressure is the same inside and outside the hose if there is no air flow. Which means there is nothing the hose needs to balance with its strength. Which is especially true if the hose is open on the other end (=top). On sea level air has a hydrostatic pressure of approx 100000N/mē which would make even Atlas crack if he would have to hold it on his shoulders. But there is no problem with this, because our body is under the same pressure and feels pretty comfortable with that. A hose has the same pressure relief, so you may only need to hold the surpressure of the resistance pressure 'loss' - but I'm not even sure about this, because it is a flexible hose and not a fixed pipe.
Before you can say strength is not an issue, you need to actually calculate the pressure required inside the hose at the bottom. Of one thing I can guarantee you without doing the calculation: the pressure will not be trivial. It will matter.
If I blow trough a very long hose from 1 bar into vaccum (and are ignoring friction), what pressure will the hose (not a fixed wall pipe) have ?
The question is so badly conceived as to be unanswerable. If you supply 1 bar of pressure at the bottom of the hose, no air will flow because that's the static pressure of the column of air. You need to provide greater than 1 bar of pressure to make the air flow.
And thanks for the offered help on the strength calculation - as soon as we agree on the pressure gradient in the hose I will have to re-do that.
Without the weight of the hose, you can't calculate the pressure gradient. So you need to select a possible material first, find its weight, then calculate the required friction force to hold it up.
Well, I already checkd with Paul (who IS the 'jury' - because he invented the prize and took care of the funding). He agreed that my proposal meets the spirit of the competition and I would be allowed to partizipate with this approach. And yes, I have sent him the slides and he said the space hose would qualify as a launch device to space!
Based on what you said in your second post, it sounds like you deceived him. Did you tell him that it was at 100 km altitude and supported by the hose? Because in your second post, you said "being outside of the launch device" which makes it sound like it isn't still supported by the hose.

In the rules, it says the satellite cannot be attached to the launch vehicle. So it is clear to me that just sitting on top of a tower - at any altitude - does not qualify.
The mssing piece in my understanding is not the defintion of orbit - there are plenty.

Achimedes didn't concentrate on the meaning of the world flow either. He simply solved the problem to make it go upwards.
You're missing the point: just achieving 100km of altitude and sitting on a tower doesn't solve the problem they are trying to solve. Getting into orbit is a big problem and solving it is the goal of the N-Prize. Just sitting on a 100km tower - as daunting a challenge as that is - is much easier than getting into orbit. Once you are clear with the N-Prize organizers about the concept, they will realize that your device does not meet their criteria.
DaveC426913
#30
Sep13-10, 06:18 PM
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Quote Quote by gutemine View Post
The mssing piece in my understanding is not the defintion of orbit - there are plenty.
The judges of the the N-prize will be crystal clear about what they consider an orbit.

Ask them. Eliminate the confounding details in your propsoal - just tell them you plan to suspend the satellite on a tower 100km up, over a fixed point on Earth.

See what they say.

I will wager one jillion dollars on the answer.
mugaliens
#31
Sep14-10, 05:04 AM
P: 595
Quote Quote by DaveC426913 View Post
Yeah, mug where are you getting this from?
From the source. To wit: "10. Acceptable Methods of Attaining Orbit
Any method of attaining orbit is acceptable, provided it does not breach the rules or spirit of the N-Prize Challenge. Examples might include (but are by no means limited to) conventional rockets; balloon-launched rockets (rockoons); gun-launched projectiles; or combinations of these or other methods. All entrants are strongly advised to contact the organisers at the outset to ensure that their proposal falls within the rules and spirit of the N-Prize Challenge."

Quote Quote by DaveC426913 View Post
Ask them. Eliminate the confounding details in your propsoal - just tell them you plan to suspend the satellite on a tower 100km up, over a fixed point on Earth.
Gutemine reported he's already done that, and that they confirmed his concept meets their rules with respect to their definition of the term "orbit."

ETA: If you find something in the rules which specifically disqualifies his idea, I'm all ears. The rules appear, however, to encourage out of the box thinking.
JaredJames
#32
Sep14-10, 11:17 AM
P: 3,387
So by the logic I'm seeing here, everything is orbiting the planet earth, plants, animals, pebbles, the ocean.... (you get the idea).

Anyway, if my understanding of what Gutemine is saying, if you were to build a skyscraper 100km high, he (and apparently the N-Prize judges) would consider anyone on the top floor to be in orbit. And if they were to fly a kite that would be considered a successful satellite launch and orbit (despite still being attached). Am I correct?
Which means they must also consider a person in a 1km skyscraper (or any of the above examples) to be in orbit. The only reason they can't win is because of the "must be above 100km" rule. I think that's a fair assessment of the situation here. This 'space hose' is simply an extension of the earth in the same way as Mount Everest, in fact, why not just deploy from atop such a mountain so you don't need such a long pipe.

On a more serious note, where would you get 100km of such a hose within the budget? What would you use to pressurise it? I've never heard of any systems that could apply a suitable pressure over 100km, especially not vertically into space.
DaveC426913
#33
Sep14-10, 12:23 PM
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Quote Quote by mugaliens View Post
ETA: If you find something in the rules which specifically disqualifies his idea, I'm all ears.
Yes. Their use of the term orbit.


Let me be clear:

1] Orbit means its path is bound by gravity, not by a supporting force such as a tower. Don't take my word for it. There are many ways to word the definiton of an orbit, but none of them involve being supported on top of a tower (and yes, that includes the space tower).

2] N-prize judges are OK with the OP's proposal because the submission itself actually does address the orbit requirement. It poses an idea for "blowing out" the satellite tangentially (though it is only one line, it is enough).

3] However, the OP, in his discussion with us, is changing his goalposts. He now thinks that he doesn't need that tangential velocity to meet the requirements.

4] If he updated his proposal such that it claimed to do nothing more than sit at the top of the tower, I guarantee the N-prize judges will tell him it does not meet the criteria.
JaredJames
#34
Sep14-10, 12:47 PM
P: 3,387
Quote Quote by mugaliens View Post
ETA: If you find something in the rules which specifically disqualifies his idea, I'm all ears. The rules appear, however, to encourage out of the box thinking.
11. The Satellite
The satellite must have a mass of between 9.99 and 19.99 grams, including the weight of any propellant or fuel. The organisers reserve the right to weigh the satellite before launch (or to have it weighed by a third party) to ensure compliance. The satellite must be a single object; for example, a cloud of un-connected co-orbiting particles does not count. The satellite may include (for example) shielding or fuel that takes its weight over the 19.99 gram limit, but orbits will not count toward the 9 orbit target until such over-weight items have been jettisoned or consumed. As noted, other items (spent rockets; shielding etc) may enter orbit with the satellite, but must not remain attached to it. Nor may the satellite be dependent upon the co-orbiting items in any way (for example, for relaying communications) during the nine qualifying orbits.

According to the above rule, the satellite must either:
a) not remain attached to the launch hose, which means that on detachment from the space hose the satellite must be travelling fast enough to overcome earths gravity and remain in orbit (as pointed out previously), which it would not be.
b) remain connected to the tower (assuming they allow the whole system to be classified as the satellite), which purely based on the rule above, the 'satellite' (if you can call it that) would (massively) weigh over the maximum 19.99 grams (satellite + hose + whatever supplies air pressure to the hose), therefore excluding it from the prize.

That, is how the rules say you can't do this, without the need to debate the definition of orbit.
gutemine
#35
Sep14-10, 04:23 PM
P: 59
Sorry for not answering earlier, but I will try to reply on your feedback and valuable inputs (but I have to do this step by step, so again sorry for editing this reply multiply)

First of all I'm aware that all of you are trying to help, and you are definitely not discouraging me. As I already explained from the enery perspective the difference between beeing in orbit and gettign their is so irritating (and to the disadvantage of teh step of getting there - which includes reasonable speed and height) that I thought solving one after the other would be a good engineering approach.

The problem with convential approaches (like simply building a smaller rocket for a smaller payload) don't work too good either - some pieces (like the weight of the tanks for holding pressurized fuel, size of an efficient rocket motor or fuel pump, or even a simple communication device to say 'I'm here, are not easy scalable - so the Idea of the N-prize is also about new and crazy ideas (which maybe would scale back to the real problem).

Let me maybe make another simple example: Instead of trying to build a smallweight powerfull radio transmitter maybe even with a GPS Receiver to log the location why not just using 1mē of aluminium foil. Just becasue Sputnik started the 'I broadcast, so I'm here' business doesn't mean that this is the only way to proof.

1mē of aluminium foil properly expanded could produce enough radar reflection so that it is tracable from earth - without emmiting anything actively.

NASA can trace far smaller pieces in space and does this on a daily basis. And 1mē of aliminium are easy to get within the budget and weight limit.

But this is just to illustrate that a different solutin doesn't mean to be a bad one, or one against 'the rules'.

The Wright brothers also preffered to solve one problem after the other - first the steering (patented) then the wings (self tested and optimized) then the propellor (self tested) the engine (self built), then the flyer, then the suitable testing/launching place - and then they had a lift off and the entire problem was solved. If they would have been told 'without an engine/propellor your wings will not fly' the problem maybe would have been solved by somebody else.

But back to the problem ...
JaredJames
#36
Sep14-10, 04:26 PM
P: 3,387
Gutemine, I see little point in you replying to anything else regarding your entry into the N-Prize unless you can explain how you will get around rule 11 as I have pointed out above.

Anything???

In the rules it say's you have to prove it completes 9 orbits and that they have to be satisfied with the evidence. The "I broadcast, so I am here" business let's you know exactly what it is you are tracking, a simple radar reflection does not.

Besides, how would you deploy 1m^2 of foil with less than 19.99 grams to work with? A simple transmitter and battery would take far less than any device for constructing a foil sheet.

First you remove orbit by sitting it on a tower and then you plan to use foil to track it, I think you are making far too many assumptions about what is "within the spirit of the n-prize" and what they will accept as orbiting and proof of 9 days worth of orbital existence.


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