Exploring the N-Prize Problem with a Space Hose Solution

[JaredJames]

I know you can do it, I've done it myself.

I meant, first you have to get thing up there, let's assume you've done that. Then you have to balance it there. Now on a relatively still system, yes, you could do it. I just can't see how you could keep the top of that tower still enough to hold it there. You're talking of keeping a 100km tower stable and upright. I know it's a poor comparison, but given what they have to do to keep sky scrapers steady (counter balancing weights) I'd say it ain't so easy and I'd be very interested in a solution to this problem.

 

[mugaliens]

You will be astonished as I am.

DaveC, thank you for your forthrightness.

Lol, I know it doesn't meet our long-held definition of "orbit," but let's consider a couple of things, beginning with the goal of the N-prize. It wasn't necessarily to place something into a traditional orbit, but to elevate something useful, even if it's only 19.99 grams, to a sustainable "orbital" altitude. From what I've read, the original idea was 99 orbits, but I think their shortening it to 9 orbits makes sense, as orbital decay for a 15 gram object at 100 km is rather fast.

Now, that being said, the N-prize rule-writers are still wrong. They cannot make up their own definition of a existing word and use it in their rules more than a half dozen times.

Well, they're the ones fronting the money, which is actually not very much. Have you considered fronting a somewhat more reasonable amount, say, 10,000 pounds, in the hopes someone might achieve a more technically accurate definition of "orbit at 100 km?"

Evan that may be contrary to the N-Prize goals. Have you considered the fact that the actual goal wasn't to get people to come up with a NASA-ideal solution at all, but to kick them very, very far out of the box, to weed out all the rest, so as to come up with one or two truly innovative solutions which bear absolutely no resemblance to anything like what we've ever seen before?

Wouldn't that be something! Imagine if Westinghouse had said in the 1900s, "we're offering an E-Prize for anyone who can illuminate a room with the same degree of illumination as a 100W light bulb, but with just 33 W, and the light bulb must last 5,000 hours.

Naturally, everyone would dive on the idea of using an incandescent, and perhaps halogen varients might have been quickly realized, but would any of them have come up with a CFL in 1900?

Hmm... I've spend the last two days working on the logistics of a multiple balloon and parachute-supported trebuchet-like system which might be able to fling a 100 lb payload to 200,000 feet.

I got the idea from http://www.gamasutra.com/php-bin/news_index.php?story=25264", which itself encourages people to think outside the box. Most of the issues can be solved via straight-foward mechanical engineering, but some of the solutions I've found on Youtube are utterly, incomprehensibly brilliant - unlike anything I've ever seen!

I have little doubt that most of us could muddle our way through the FC 1, 2, and 3 problems, but what I'm really interested in are the incredibly insightful and totally out-of-the-box solutions I find on YouTube. Absolutely unbelievable! Totally beyond the bounds of what could possibly conceive! Make no mistake, though - they deliver the payload to the target area. They achieve the objective.

I think this was the N-Prize creators' objective. We know how to spend $1B dollars and put a payload in orbit. Heck, I can do that with $1M using a very large rail gun and a solid rocket orbital insertion module.

But for $2,000?

There is simply no way to get there from here using conventional technology, and that's precisely their point: Don't use conventional technology. Instead, achieve the objective and call it a day.

 

[mugaliens]

Here's another idea along the lines of thinking outside the box: Using the absolute best fiber for the money, hoist a weight with a balloon carried aloft which tensions a line connected to a small rocket. You'd have to optimax the solution such that the balloon, the line, the weight, and the rocket would all meet cost specs. However, when the rocket, connected to the weight via a pully, was released, while the balloon was downwindon a trajactory of perhaps 45 to 60 deg, the balloon wouldn't fall much (ballutes? ancilliary rockets?), the line wouldn't break, and the rocket, up reaching umpteen thousand feet (perhaps 180,000 feet? Would be traveling fast enough for orbital insertion with minimal burn.

Lots of technical challenges to overcome, to be sure, but there always are! At least we're thinking outside the box.

 

[JaredJames]

mugaliens, your ideas would truly insert a satellite into orbit.

however, gutemines does not. if you accept that his solution does actually put something into orbit then you also believe that aside from the 100km rule in the n-prize, that a person on top of a skyscraper is also in orbit. they are not.

the spirit of the n-prize is clearly indicated in the rules "to put a satellite into orbit using pretty much whatever way you like" - but the word orbit is used multiple times throughout. they do not imply they want a satellite 'placed at an altitude greater than 100km and to remain there for at least 9 days". no, they say they want the satellite placed into an orbit of at least 100km and it must complete at least 9 orbits to win the prize. there is a significant difference between the two.

I am happy to let this go seeing as the n-prize judges have decided to redefine what orbit actually is, and concentrate on the physics of the proposal. so far as this thread goes, i think that is for the best.

So far, I accept the column of air idea to hold the satellite in position above the 100km mark, however I am unconvinced that the 'hose' can remain stable enough to allow the column of air to be consistent and relatively steady to hold the satellite.
I think the key here is calculating the required hose pressure to support such a tower and once you can be assured of rigidity, look at ways of maintaining the vertical altitude. deal with the sattelite issue last (although I think some consideration needs to be made wrt it now as you don't want any surprises later on).

EDIT: I'd also like to see some half decent costings for materials and whatever will be used for supplying the pressure to the system. So far gutemine has assumed a cost of 1c / metre giving a cost of $1000, and there is another quote based on actual prices giving a total cost of $6000, a rather large leap in my books and way outside the prize budget (although I'm sure they can redefine £999.99 to somewhere in the required region... )

 

[gutemine]

Hi !

Thanks for all your usefull input.

In the slides I actually calculated the pressure to support a PE foil hose that long (0,6 bar for the 4 micrometer foil, multiples of that if you use 12/25/50/100 my foil. This is pretty simple because if you assume worst case - all the weigth on the top then you can use simply the piston formula - weight*9,81 = gives the force in Netwon, then divide with the area of the hose (r²Pi) and you get the pressure - all hydrostatic pressure of the inside is balanced from outside.

300*9,81/0,05=58860N/m² which is less then 0,6 bar. Actually it should be much less, because most of the weight of the hose is not on top. AND it is a hose - so there is no 'piston' at all.

If you then take a 1m long part of the hose at the bottom the force on one half of the hose will be this pressure * height * diameter = 58860*1*0,25=14715N (approximately 1,5t of weight equivalent trying to tear the 1m hose piece)

This has to be held bei the 2m of foil (2 sides of the hose each 1m long) 4 micrometer thick

Stress in the foil will therefore be force/(2*height*thickness)
14715/(2*1*0,000004)=1839375000N/m²

Normaly strengt of a material is given in N/mm² so wie have to divide by 1.000.0000 - gives a stress in the foil of 1840N/mm² This is approximately 100x what normal PE foil can hold.

Dyneema, which is a kind of ultra long PE chain fabric now can hold 3000-4000N/mm² before tearing apart.

And now the good story - if you use thicker foil, the pressure goes up lineray, but also the foil strength, meaning it should work in all sizes.

But this is actually the calculation for an inflatable space tower (and they suggest to use kevlar which has compareable strength)

If you have an open hose the math should be different. If you are open, there should be not a pressure surpluss - how should it build up without friction ? So maybe you would not need any Dyneema strength :-)

Then you add friction and calculate the pressure drop it causes - and then you face the problem what really happens. And that is exactly the point when I put the math on the slides and posted them tpo ask for help and better understanding.

gutemine

PS: And don't worry too much about the cost of the foil (and even the Dyneema) - I will not buy 100km on the first try anyway. If I have the feeling that 1c/m is not ways off or 100x too low then I can live with that for the moment (NASA also overruns their budget regulary - so I have good company). Escpecially as long as I don't know how thick the foil really has to be, and if I need the Dyneema strenght because of the pressure or not or only for holding the pull forces for stability. Be also aware that all these parts of the hose are theoretically reusable and have also quite a scrap value (pure PE is recycleable) - so the purchasing cost is maybe not even fully counting in the calculation. If I borrow a standard industrial fan it is very likely that I would need to include only the energy cost and not the fan cost - and for 10 days the energy bill actually looks amazingly low.

 

[gutemine]

Here's another idea along the lines of thinking outside the box: Using the absolute fiber for the money, hoist a weight with a balloon carried aloft which tensions a line connected to a small rocket. You'd have to optimax the solution such that the balloon, the line, the weight, and the rocket would all meet cost specs. However, when the rocket, connected to the weight via a pully, was released, while the balloon was downwindon a trajactory of perhaps 45 to 60 deg, the balloon wouldn't fall much (ballutes? ancilliary rockets?), the line wouldn't break, and the rocket, up reaching umpteen thousand feet (perhaps 180,000 feet? Would be traveling fast enough for orbital insertion with minimal burn.

Lots of technical challenges to overcome, to be sure, but there always are! At least we're thinking outside the box.

A lot of the other teams at teh N-prize go for this approach, but I see some problems.

Ballons don't work beyond 20-40km (depending how expensive you build them - even Red Bull stratos only goes for 36km - and they don't have a budget limit - N-proze has) And launching a rocket at such low pressure penduling under a balloon is not that easy (unfortunatley there it is pretty cold - so it can freeze). During start in sich a thin atmosphere any finns on the rocket wil not stabilize until you reach reasonable speed and then it could be too late. If you try to stabilize with gyroscopes, or rotating rockets you end up with a pretty complex apparatus which is likely to fail.

The space hose has all moving parts of the engine on the ground, and because PE foil is very flexible it can store lots of pressure on this lenght, which would support stability. And blowing out the air on the top downwards can create a nize stabilizing pull without the need of a counterweight in >36000km

But as long as we haven't solved the friction/pressure puzzle I cann't tell you how much pressure/speed the air would have on the top. If you have this calculationg how much pull this could produce when blowing downwards is not that difficult. The calculation in the slides with the ideal gas formula only gives an idea - which scared me :-)

But as you wrote - lots of challanges, but why not solving one after the other ?

gutemine

 

[JaredJames]

Sounds interesting, although I would point out, the prize is requiring a specific budget to be eligible, if you go over it too much then the spirit of the prize is lost. Whether NASA go over budget or not is irrelevant, they are not chasing a prize. I do agree, if the foil isn't damaged it could be reused and so the cost offset.

I'd like to do a few calculations myself, could you confirm for me that the space hose you propose is like the one in your report? A cone shaped device or is there another design you were looking to use? This is purely to aid in the calcs.

 

[gutemine]

Sounds interesting, although I would point out, the prize is requiring a specific budget to be eligible, if you go over it too much then the spirit of the prize is lost. Whether NASA go over budget or not is irrelevant, they are not chasing a prize. I do agree, if the foil isn't damaged it could be reused and so the cost offset.

I'd like to do a few calculations myself, could you confirm for me that the space hose you propose is like the one in your report? A cone shaped device or is there another design you were looking to use? This is purely to aid in the calcs.

Don't take my NASA jokes too serious - check the scrap value of PE, and don't forget that you can even burn it - it's pure oil more or less (and not as dangerous as burning PVC)

As long as nobody helps on the gasdynamic friction calculation I will stay with a fixed diameter approach. Because that is the cheapest way to manufacture AND the easiest to calculate.

As the slides suggest if we could agree on the pressure / flow speed behaviour it would need to be re-calculated with a kind of finitel elements method - calculating 100m pieces of the hose in a spreadsheet programm with the existing formulas (I don't have any better until you help me out) and see what is the real outcome. You there simply feed the pressure and flow from one calculating 100m piece to the next one and becauset he bordervalues (pressure and temperature outside) are known for the atmosphere you can easily solve this puzzle. It will not be 100% accurate either - but much better then what I did so far.

But for building such a mathematical model (where you then can optimize flowspeed, diameter, foil thicknes,..) you have to use correct formulas and at least the assumptions should be correct too - eg friction energy loss to keep the hose upright is supplied by pressure surpluss or only by cinetic energy of the flowing air, does it really go hypersonic,...

But I asked for checking my math (and maybe do a better one on your own instead of duplicating my mistakes), so please proceed, and if anything in my slides or math is unclear feel free to ask.

gutemine

 

[JaredJames]

So you are going with fixed diameter, immediately this screams to me of problems.

Think of it like this:

You are trying to balance a 100km broom handle on it's end.

Hate to be so blunt, but do you have a plan for maintaining stability, if not, then any maths completed on pressure doesn't matter.

 

[gutemine]

So you are going with fixed diameter, immediately this screams to me of problems.

Think of it like this:

You are trying to balance a 100km broom handle on it's end.

Do you have a plan for maintaining stability, if not, then any maths completed on pressure doesn't matter.

If a broom handle HANGS from the top it balances pretty well. And that is what you can achieve if you blow out at the top in the right direction (which is needed anyway or it would push the hose downwards as the wiggeling petrol station device does for entertaining the people watching)

But I have read the study that the inflatable space tower people did on stabilty (link is further up in the thread) and they got away with things like gyroscopes and 150m diameters just for a 20km structure - really scaring, but good to read and understand the problem - and come up with a better solution. The whole space hose came up by looking at the existing space elevator approaches and try to eleminate their problems by creatively combining them and use the typical disadvantage (friction, leakage) to its advantage.

Originally I thought I would have to match this paper by going for a straw pack approach with multiple hoses bundled to provide bowing stability, but the feedback at the half bakery actually pointet me in the right direction to actually accept the bow and benefit from it (if hose bows the vertical component of the outside wind actually provides additional lift and you can reduce the blowing). Because in an inflatable space tower powing converts to pressure - in a hose it converts to pull - and this is holdable by strings instead of more hoses/inflatables.

If the friction and wall effect should be able to balance the weight of the ultra light broom, then you only need a pretty small pull to keep it stable. Don't forget that if you have a small pressure surplus in the hose because of the diffusor you store also a lot of elastizity in such a PE hose and inside is air which provides also damping to any oscillation.

Regarding the winds problem you find some math further up the thread (wind at equator mainly goes unwards, and beyond 15km it is going down dramatically), and by putting it on the typical 5km equatorial mountain you can get the problem even down to 10km or less.

BTW jet stream windstreams of 500km/h sound pretty high - but at 10-15km you have 1/4 to 1/8 of the pressure on ground, meaning the actual pressure is not that worse as it sounds on the first glance - otherwise planes there could fly backwards.

And a hose pulled from the top actually can bow without anyreal problem. The inflatable tower should not and has no blowing air to provide the pull force either. If we really want to do a blowout launch it actually would need to bow at least it's head for something like 20-30 degree, or the needed speed would be too high compared to pure orbital sidewards speed.

The whole think is a little bit like a clothesline - the heavy pullover/wind in our case is lukily hanging close to one pole. And the other pole is flexibly pulling instead of beeing fixed. And Dyneema strings can hold their own weight for up to 400km - meaning by just adding 3 of them to the hose they would only doble-triple the weigth (which is holdbale by increasing blow speed only by the sqaure root of this factor) and then you can really hold a lot of sidewards forces with a reasonable security margin.

Worst case is the hose bows like the clothesline and ends up in exponentional or parabolic shape from the ground but with only pulling forces, meaning the 80% of the hose outside of the wind zone would be still almost straight and just lower in height on a windy day .-)

But such a curve is perfect to keep the hose intact when these forces are transferred to the Dyneema strings, then the foil only needs to hold the dynamic pressure which is not that bad:

Let us calculate it for a 50km/h wind (not a breeze anymore) = 13,88m/sec

dynamic pressure = airdensitiy * v²/2 = 1,2*13,88²/2=116Pa - so my assumed 100 Pa surplus should be suffient for up to 40km/h of wind to prevent the hose from collapsing - not bad, but a 200-300Pa surplus would be definitely better!

That's why I liked the pravda picture in the slides so much - actually the illustrator's string idea is pretty good. It is not his fault that you don't see the foil on the black and white picture :-)

Even the SAT inside is correct and could be lifttet from the airflow as already explained, and because of gas expansion due to the decreasing (hydrostatic) pressure it would even accelerate while going upwards.

So the NASA climber problem is also solved with such an pneumatic approach (at least for an N(ano)-SAT) - no need for beaming energy with lasers anymore. BTW the current climber challange asks for 5m/sec - I calculated with 3,6m/s but this was just an asumption to get an idea how high the friction forces would be. 5-10m/sec is probably more realistic due to the extra weight for the strengthening as explained above.

gutemine

 

[N-Prize]

Hi, I'm Paul from the N-Prize.

Things here are getting heated, I appreciate. I have also been in contact by email with various people (including some in this discussion).

First, let me say that no team has yet registered with a space-hose proposal. I have also not made a final decision on the validity of such an approach. My first reaction was "yes", but I can also see very good arguments for "no". If and when it looks as though someone is likely to register a proposal involving a space hose, then a final decision will, of course, have to be made.

Regarding the capriciousness of the N-Prize rules - yes they are! Any rules which try to pin down all possibilities from the outset will be open to argument and subject to unforeseen circumstances, and I am very willing to accept that I can be wrong. (This is borne out by the other, much larger space prizes, which have led to all kinds of arguments despite rules which were twenty times more detailed than those of the N-Prize.)

The best I can offer is that (a) I will try to be fair; and that (b) nobody is compelled to enter.

Personally, I love the space hose as an idea, and I believe that a successful demonstration would be tremendously significant, well beyond the terms of the N-Prize itself.

As to eligibility for the N-Prize, a final decision has not been made. As I have indicated in some emails, one compromise option is to use a space-hose as a launch platform for a satellite which then orbits completely independently. This of course requires imparting orbital velocity to the satellite, which is no mean feat. On the other hand, given the low mass of the N-Prize satellite, this would not be the most difficult part of any mission: the main engineering problems for all of the existing teams lie in the ascent, which the space hose bypasses.

If people would like a final decision on this, the best way to force it will be to ask to register, whereupon I will be compelled to say yay or nay. In doing so, I will also discuss the topic more widely amongst the existing teams, and will try to come to a fair decision. Who knows, I may even offer an independent prize for a hose/tether/mountain system.

So, if this is becoming a serious issue, please do feel free to ask to register. There's no cost, and about 10 seconds-worth of paperwork.

 

[gutemine]

Hi !

Thanks for explaining. One of the reasons why I asked here and also in the halfbakery and the N-prize forum for help

 

[DaveC426913]

This is almost like a government operation now - we spend 6 pages discussing the legal stuff and nobody did the real construction and research job :-)

Well, another way of looking at that is "don't work harder, work smarter".

You want to make sure that, when you do sit down to work, the "should I be doing this at all" part is rock-solid.

Otherwise you might spend all that engineering time barking up the wrong dead end, chasing a red herring.

 

[DaveC426913]

Hi, I'm Paul from the N-Prize.

Things here are getting heated, I appreciate. I have also been in contact by email with various people (including some in this discussion).

First, let me say that no team has yet registered with a space-hose proposal. I have also not made a final decision on the validity of such an approach. My first reaction was "yes", but I can also see very good arguments for "no". If and when it looks as though someone is likely to register a proposal involving a space hose, then a final decision will, of course, have to be made.

Regarding the capriciousness of the N-Prize rules - yes they are! Any rules which try to pin down all possibilities from the outset will be open to argument and subject to unforeseen circumstances, and I am very willing to accept that I can be wrong. (This is borne out by the other, much larger space prizes, which have led to all kinds of arguments despite rules which were twenty times more detailed than those of the N-Prize.)

The best I can offer is that (a) I will try to be fair; and that (b) nobody is compelled to enter.

Personally, I love the space hose as an idea, and I believe that a successful demonstration would be tremendously significant, well beyond the terms of the N-Prize itself.

As to eligibility for the N-Prize, a final decision has not been made. As I have indicated in some emails, one compromise option is to use a space-hose as a launch platform for a satellite which then orbits completely independently. This of course requires imparting orbital velocity to the satellite, which is no mean feat. On the other hand, given the low mass of the N-Prize satellite, this would not be the most difficult part of any mission: the main engineering problems for all of the existing teams lie in the ascent, which the space hose bypasses.

If people would like a final decision on this, the best way to force it will be to ask to register, whereupon I will be compelled to say yay or nay. In doing so, I will also discuss the topic more widely amongst the existing teams, and will try to come to a fair decision. Who knows, I may even offer an independent prize for a hose/tether/mountain system.

So, if this is becoming a serious issue, please do feel free to ask to register. There's no cost, and about 10 seconds-worth of paperwork.

Thanks Paul. I too appreciate you weighing in with the N-Prize take on the rules. (I was one of the ones that reached out to you for clarity.)

IMO, there's nothing wrong with the N-prize allowing space tower-esque submissions, it's just that the N-prize rules need to be re-worded to make plain that "orbit" is not required. Currently, all physics buffs who consider vying for the prize are reading "orbit" in the rules and (rightfully) assuming the standard definition, which means they disqualify any space-tower-esque ideas before ever approaching you. To then let one in because the term "orbit" is being misused in the rules will have contenders outraged.

 

[gutemine]

Well, another way of looking at that is "don't work harder, work smarter".

You want to make sure that, when you do sit down to work, the "should I be doing this at all" part is rock-solid.

Otherwise you might spend all that engineering time barking up the wrong dead end, chasing a red herring.

Thanks for the motivation !

Please try to see it also from my point of view.

The critical part is if a hose would works like suggested (an open hose using friction to produce lift) - and we are still circling this question without a real answer.

As you might already have realized gutemine works different, I prefere to solve one problem after the other (the Wright example is a pretty good one that there is a fair chance to succeed with such an approach). And yes I'm aware of the other problems, that's why I tried to anser also your inputs and concerns as good as possible. BUT they don't scare me or prevent me from proceeding.

Especially because I have thought about them too and also checked a lot of them (stability, wind,...). And discussing these parts (including the orbital speed part which would be nice but is not really a must for the moment) is OK with me, but not the full story.

For me the pneumatic part is not on a much higher level then the typical high school physics (actually if you have a good teacher there most of the math I used should look pretty familiar) - so why do we have problems coming on this point to a real discussion ?

Or is this really rocket science which needs lots of egg heads and tonns of computing power to solve the unsolvable ? Then maybe I didn't realize that I accidentially stepped into quantum mechanics and am stuck in the process of building a particle accelerator with superconducting :-)

Every journey starts with the first step, and you often only know the destination, but you don't know for sure what the last step will look like until you have already done it.

gutemine

 

[JaredJames]

Hi, I'm Paul from the N-Prize.
...
As I have indicated in some emails, one compromise option is to use a space-hose as a launch platform for a satellite which then orbits completely independently. This of course requires imparting orbital velocity to the satellite, which is no mean feat. On the other hand, given the low mass of the N-Prize satellite, this would not be the most difficult part of any mission: the main engineering problems for all of the existing teams lie in the ascent, which the space hose bypasses.

Thank you Paul, your insight is much appreciated.

I have quoted this small section and highlighted what I believe to be an important factor that cannot be overlooked and some consideration given to before dedicating yourself to your 'space hose'.

The satellite must orbit independently I think is the key, so the hose must be the launcher. This means you need to attain orbital velocity or hold a ballistic trajectory with altitude > 100km for a period of nine days (although I wouldn't class that as an orbit, it would seem to suffice here).

 

[gutemine]

I'm aware of this inherent limitation which I don't see as a problem and I don't see this as a threat or a roadblock either - I see this as an opportunity.

I already explained that it is not such a bad idea to solve the height and speed problem individually - the ballloon and rocket guys actually try the same - only 70km lower where it is much more difficult because the 70km remain also.

Hence the disadvantage of the hose actually still is an advantage in my opinion. You have the needed height and lots of air to work with on the remaining part of the problem. Which is exactly what you do as a partizipating N-prize team - hoping to succeed.

Nobody really commented so far on problem that the ideal gas formula would actually SUGGEST that the gas there already should blow out at (almost) orbital speed - the slides contain already the math and I already explained that this even would be even logically to some extent.

The slides already say unrealistic - but WHY and what is the CORRECT speed we would face there ?

And No is a comment, but I hoped for more ;-)

PS: Sorry for the capital letters - I don't want to be impolite, and I would also accept a 'we don't know' - if you help me finding somebody who does.

gutemine

 

[N-Prize]

Hi again all,

Sorry, I've been trying to sleep off a monster cold (well, it's "man flu", and we all know how serious that can be...). I'm also up to my ears in epinephrine, paracetamol and every other substance available, so apologies if my answers are as fuzzy as my head.

As far as the physics of the space hose goes, I wish I could help more, but my physics falls wayyyy short of being able to make a useful contribution. I've also tried to track down physicists who might be able to help, but with no real luck. (I'm a biologist, oddly enough.)

But as to the topic of viability/legality etc under the current rules - all your points are well taken. And yes, I can see many valid objections to broadening "orbit" to include something sitting atop a space hose. That still leaves the option of rewording the rules to demand that something stays up there by means of orbit "or other means". I do reserve the right to make such changes, but in this case I would seek the opinions of the existing teams.

My big mistake was in giving a positive opinion on the "legality" of the space hose before thinking out the consequences - for which I apologise.

If plans can move towards using the space hose as a launch platform for a free-orbiting satellite, that would solve many problems and would be a stunning outcome! (The kinetic energy of a 20g mass orbiting at 100km, incidentally, is about the same as the energy available from a teaspoon of petrol - which you doubtless already know but which always amazes me.)

As regards budgets, I will have to re-read the rules carefully to see how the hose, used as a "platform", would count. 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?). But let me think more on this before putting my foot in it again.

Yours,
Paul

 

[JaredJames]

Despite my previous comments regarding the legal side of things, I'm actually quite interested in whether or not such a system could work (if not on a realistic scale, at least for the N-Prize).

I am currently trying to look at stability issues with the hose, I'm not sure if you've quoted any before, but what sort of dimensions are you looking at using for the hose?

As I said previously, without a good support structure a constant diameter tube extended 100km vertically would be extremely unstable. Could you provide those numbers plus a reference for this material you want to use for the hose?

 

[gutemine]

If you look at the slides you have most of the numbers with which I started my calculations.

The 10" choosen diameter was just to have a commercially available dimension as a starting point and to be able to do a few km 'test launches' without manufacturing any special. If you want to launch something beyond an N-SAT probably bigger dimensions would be better.

The wind pressure calculation for the first 15km (beyond this jet streams are over and pressure is already pretty low) is already in the thread (I think 1-2 pages up) with a 50km 'breeze' as an example. You will find also the stagnation pressure of the hose under such a wind there. If you calculate the WORST case - eg whole force als pull on the bottom of the hose you get the 1800N/mm² - normal PE has only 20-30N/mm² but Dyneema has 3000-4000N/mm² tearing strength. And because the dimension of the foil is so low a single 8mm Dyneema string can hold this. I would prefere 3-4 strings with 4mm² to balance better and prevent spiralling of the hose.

See this as a kind of huge sail - hight tech sails are nowaday available from woven Dyneema and the strings to hold it are also Dyneema ones. And this on sea with rain, saltwater, low temperatures. The sail area of the space hose is not so much bigger (as calculated already above) but a cylinder has a pretty good friction coefficient if blown from the side (I used 0,1 - a sail is 1 or biger because it is desinged to catch windforce)

A hose under a reasonable pull force is like a giant spring or better a rubber band (with huge damping because of the air filling and light pressure surpluss) so it is not such a bad device to withstand forces - because it is small, so the forces are limited. And you still could use the straw pack approach that the inflatable space tower people suggest. PE can be flexible up to 10% before tearing apart, but we need much less in this case if you have a few Dyneema strings taking the pull force. The Pravda picture approach copied into the slides is not that bad from the enigineering perspective.

And as I already outlined - bowing is WELCOME for a hose pulled from the top, because it is a pretty flexible structure and should not be harmed. Worst case is the top going down a few km if the wind is heavy.

Finally the good thing about windforce is that it is a pretty continuous force and not a punctual one. So you can use existing engineering formulas to calculate the caused tension - I simply asumed the worst that the entire force is taken from the bottom as pull - which is still holdable

But please check and do your own math - EVERY input is welcome and valuable. And if we can verify the strength and stability part the penumatic one can wait (the slides actually suggest to ask an engineer AND a physics)

gutemine

 

[DaveC426913]

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.

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...

 

[gutemine]

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

 

[DaveC426913]

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'.)

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.

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

Or perhaps the local space agency?

 

[gutemine]

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

 

[mugaliens]

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

 

[gutemine]

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

 

[DaveC426913]

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.

 

[DaveC426913]

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.

 

[gutemine]

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

 

[JaredJames]

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.

 

[gutemine]

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

 

[JaredJames]

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?

 

[gutemine]

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

 

[DaveC426913]

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.

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.

- but I'm definitely in space!

Actually, no. You're surrounded by atmo.

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.

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.

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.

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.

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.

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.

 

[gutemine]

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