Inflatable "space elevator"!

[RainDreamer]

News:

http://economictimes.indiatimes.com/news/international/business/canadian-firm-patents-20-km-high-inflatable-space-elevator/articleshow/48502218.cms

http://www.gizmag.com/canadian-firm-patents-inflatable-space-elevator/38773/

http://www.telegraph.co.uk/news/science/science-news/11805987/Inflatable-space-elevator-invented-by-scientists.html

The patent itself: https://www.google.com/patents/US20100163683

A canadian company goes by Thoth Technology Inc. has just recieve the US patent for an inflatable space elevator. Now, this "space elevator" is not exactly one in the traditional sense - it doesn't actually reach space and allow a straight up trip to geosynchronous orbit. Rather, it is only 20 km high, and acts as a port for SSTO vehicles, a place where people can launch, land, and refuel them. The tower itself is stabilized using a series of gyroscopic wheels, which may also be adapted as compressors to pressurize the tower and keep it steady above its foot print. To get up there, elevators inside the core of the tower or running along the side has been suggested.

Thoth President and CEO, Caroline Roberts, made a reference to space X in an announcement:

“Landing on a barge at sea level is a great demonstration, but landing at 12 miles above sea level will make space flight more like taking a passenger jet.â€Â

So, after all that, what do you think? Pipe dream or something that will actually work?

[Nibb31]

Launching and landing from an altitude of 20km does nothing to reduce propellant requirements. To reach orbit, you still need to accelerate from 0 to 26000 km/h, which is still going to take the same amount of energy, minus some drag.

On the diagram, their platform has a runway for winged vehicles. What's the point of landing a winged vehicle if you are supposed to be trying to benefit from not having drag? Reducing drag also means reducing lift, and therefore reducing the reason for having wings.

Edited August 17, 2015 by Nibb31

[YNM]

You'd be needing something with the shape and proportion of a U2 to gain any lift at >FL600. Landing... Talk about coffin corner and come back again.

[RainDreamer]

Launching and landing from an altitude of 20km does nothing to reduce propellant requirements. To reach orbit, you still need to accelerate from 0 to 26000 km/h, which is still going to take the same amount of energy, minus some drag.

From the news section of the company website, they boast: "The technology offers an exciting new way to access space using completely reusable hardware and saving more than 30% of the fuel of a conventional rocket."

Not sure where they are pulling their number from though.

[Shpaget]

Such a cosmic lift would move payloads much more efficiently at an estimated cost of US$220 per kg ($100 per lb), which is a considerable saving on present costs of $25,000 per kg ($11,000 per lb).

While 20 km may not seem like much compared to 36,000 km, it's still 20 times higher than any other manmade structure and high enough to shave a third off of launching costs.

Eh? Does not compute.

the company has proposed using a series of flywheels to provide dynamic stability, and to act as compressors to pressurize the tower. By adjusting pressure and spin, the flywheels can compensate for any bending of the tower and keep it fixed over its footprint.

No, flywheels most certainly can not do that. They can help with rotation, not translation, and when wind shears and jet streams start to flop it around you get a giant Wacky Waving Inflatable Arm Flailing Tube Man.

[Streetwind]

Yeah, I'd love to see their math.

I mean, due to maxQ being vastly lower you can probably have rockets that fly an aggressive pitchover into a very flat trajectory, and on top of that accelerate harder, which would reduce gravity losses significantly - and in contrast to drag losses, gravity losses are actually a meaningfully large chunk.

But on the other hand, how much harder do you want to accelerate? Unmanned rockets already push G's that would be severely uncomfortable for manned flight. You wouldn't get any acceleration benefit for manned flights, because you don't want to push that hard with them. So that leaves the flatter trajectory. Can it really save 30%? I personally doubt it.

This of course assumes that you're launching staged rockets, which to this day are still cheaper and more feasible than SSTO spaceplanes (AKA rockets exist, SSTO spaceplanes don't). I find it very difficult to imagine what advantages a high runway location offers to winged vehicles. Takeoff and landing is going to be complicated massively due to the reduced lift. Remember, 20km is twice the cruising altitude of commercial airliners, and spaceplanes generally opt for lower wing areas to reduce dry mass. How are you going to take off and land subsonic at this altitude?

I don't see this proposal working out, tbh, and that's without even looking at the structure itself. Whether they can build it or not is not relevant if there's no business case, and I don't see one.

[Nibb31]

If altitude was important, something like the Stratolaunch carrier plane would be much cheaper (and more flexible) than a fixed 20km tower. But even Stratolaunch doesn't make any sense.

Edited August 17, 2015 by Nibb31

[KSK]

I don't even have words for this. Correction - I do have words but most of them aren't suitable for this forum.

The patent is unadulterated tripe, consisting of nothing more than a vaguely described wishlist of features backed up by some sketchy and highly dubious looking maths, that utterly fails at telling a 'person skilled in the art' how to practice the invention.

A 20 kilometre inflatable tower, strung with heavy spinning wheels along it's length and topped with a structure capable of withstanding rocket launches. What could possibly go wrong? I guess the Kerbin Space Agency might be interested in this but I hope to which deity takes your fancy that no Earth-bound investors take this even remotely seriously.

[Godot]

Considering the fact that air pressure at 20 km altitude is just ~5% of that at sea level, I think that the savings (in terms of fuel) you get by not having to fight drag, would be considerable.

You might also use rocket engines with nozzles shaped for (near) vacuum at this altitude instead of needing to have a prior stage with nozzles that give a high Isp for atmospheric use (or having to use dual purpose engines).

The big question however is, as mentioned in the thread, if the structure can be made reliable enough to withstand bad weather/storms and whether the landing on such a structure may be reliable/safe enough

The other question is, if the operation costs of such a structure would be lower or higher than the savings you get due to reducing the size/mass of space bound vehicles that use this structure as a starting/landing platform.

[RainDreamer]

I was checking the company holding the patent, and well, they have been developing satellites and providing some services for space missions, but I have seen nothing to suggest that they have any capability for something in this scale. I guess they are just doing patent trolling.

[Streetwind]

Considering the fact that air pressure at 20 km altitude is just ~5% of that at sea level, I think that the savings (in terms of fuel) you get by not having to fight drag, would be considerable.

I don't think so. Let me explain:

Cost to go to low Earth orbit: ca. 10,000 m/s

Breakdown (rough estimate)

- Orbital velocity: ca. 7,500 m/s

- Gravity losses: ca. 2,000 m/s

- Drag losses: ca. 500 m/s

- Steering losses: negligible (a small handful of m/s)

I just made this 4:1 split up on the spot, but it will serve to illustrate the point. Try launching a rocket in KSP and let MechJeb tally up the losses, you'll see it ending up maybe not exactly that but reasonably similar.

If the entirety of drag losses are 5% of the full budget required, how do you save "a third off of launch costs", like the patent claims, by reducing them? At bare minimum, you need to significantly reduce gravity losses through a flatter trajectory. Then you're talking a value that actually matters, and you might indeed shave some 10% off of launch costs, because the tyranny of the rocket equation is working in your favor. That is, if your spaceport is cost competitive with traditional ground based ones in terms of launch fees. Which is going to be a tough sell if you need to pay maintenance and R&D for a 20km tall inflatable experimental structure in addition to the spaceport that's sitting on top.

And that's also ignoring that the customer must somehow haul their rocket - an object the size of a large building, weighting hundreds of tons even empty - up a 20km tall inflatable experimental structure. No, that's not going to work. Not even in parts - because then your customer would need to rent a rocket factory on top of your 20km tall inflatable experimental structure which has preciously little space available to rent. And still haul up the parts.

The concept clearly calls for spaceplanes, which are built on the ground and then flown up. Unfortunately no spaceplanes are currently flying, the only two spaceplanes that ever went to space required humongous rockets to carry them there, and these planes would have to land and take off at extremely unsafe (potentially supersonic) speeds in order to have lift. And your runway would have to be gigantic. The space shuttle required no less than four kilometers - at sea level, for landing only, with drag chutes!

This proposal reads so poorly, I'm afraid, that it's easy to poke holes into it without even thinking about the construction of the structure. We don't even need to go there to prove it unfeasible.

Edited August 17, 2015 by Streetwind

[Kinglet]

If you want to save fuel by having SSTO planes take off from a higher place, just ditch the SSTO label and put cheap droptanks on them.

[KSK]

I was checking the company holding the patent, and well, they have been developing satellites and providing some services for space missions, but I have seen nothing to suggest that they have any capability for something in this scale. I guess they are just doing patent trolling.

I wish them the very best of luck with their trolling. I seriously doubt that any company is going to get into the Huge Inflatable Tower market within the next twenty years, at which the patent expires anyway. (I haven't checked the expiry date of this thing - it's probably more like 16-17 years before it expires but whatever). And if some company does decide to throw sufficient cash at the idea to make it work (which is also highly unlikely) then spending a little more money to have the patent thrown out would be a trivial extra expense.

[AngelLestat]

Yeah I already read this, but its kinda pointless, you may have real advantage to launch from 20km, but you will have much more advantage if you use an airship enoght big to do the same task.

With the benefic that you can launch from the equator or any place in the planet convenient for the orbit, also you can be positioned so the first stage can go down on base without waste much fuel in retro burn.

You need also a lot less energy to keep it in one place against the wind.

[pincushionman]

No, you have much more advantage by building a bigger rocket, which is what we're all doing now. The losses you overcome with a tall launch platform (or one on a mountain; we've discussed these before) or an airship are more than offset by the support costs for your assembly and launch infrastructure.

[AngelLestat]

It will depend, imagine that you can build a 1 stage to orbit vehicle, but to include enoght payload to be viable, it should launch from 20 km height in the equator.

Then an Airship makes sense, also your launch vehicle weight is reduce but a lot which reduce the airship cost.

Edited August 17, 2015 by AngelLestat

[vger]

In other news, terrorist organizations around the world have taken a sudden interest in sewing pins.

[mardlamock]

You are forgetting about the tyranny of the rocket equation people, the delta v used to compensate for gravity losses equates to a lot of propellant and a much larger vehicle overall.

[More Boosters]

You are forgetting about the tyranny of the rocket equation people, the delta v used to compensate for gravity losses equates to a lot of propellant and a much larger vehicle overall.

Streetwind referred to that by name at his post at the top of this page.

[FleshJeb]

From the news section of the company website, they boast: "The technology offers an exciting new way to access space using completely reusable hardware and saving more than 30% of the fuel of a conventional rocket."

Not sure where they are pulling their number from though.

While I think the general idea is absurd, I wanted to run some back-of-the-envelope math on this. How much dV would you have to save to get a 30% mass reduction?

Assumptions (source Wikipedia):

dV to LEO = 9400 m/s

Ve = 4400 m/s (Bipropellant engine, Isp=450s)

Plugging these into Tsiolkovsky (single stage assumed):

M0 is 8.47*M1

30% savings = M0/1.30

M0'=6.51*M1

dV'=8246 m/s

dV-dV' = 1154 m/s (So to get 30% mass savings, we only need to save 14% on the dV.)

-------------------

Is this a rational number for a 20km higher launch? What is the gravity drag savings?

I just looked at a Shuttle ascent profile, and it hits 20km in about 75s. 9.81m/s*75s = 736m/s

Could atmo drag account for the remaining 418m/s? Someone else do the math on this, but it seems order-of-magnitude reasonable ;-)

So, not accounting for those pesky logistical and safety concerns, Fleshjeb is gonna have to call this one "Plausible".

Source chart for Shuttle ascent:

Edited August 18, 2015 by FleshJeb

[Streetwind]

Could atmo drag account for the remaining 418m/s? Someone else do the math on this, but it seems order-of-magnitude reasonable ;-)

Unfortunately "order-of-magnitude reasonable" is still the difference between 418 m/s and 41.8 m/s, and the latter is clearly not going to do it

We can approximate things within an order of magnitude or two in cosmology, where the error turns out to be insignificant enough; but in engineering at human scales, even one 1/100th of that error is often too much.

Also, by the time the space shuttle is at 20 km, it is already moving at a good clip - between 650 and 700 m/s, according to that chart. Whereas if it launched from a platform 20km up, it would be at the same altitude, but with no velocity. Therefore you cannot just make the assumption that you can "cut off" the gravity losses from the first 75 seconds of flight; your actual savings are going to be significantly less than that. You still have to launch vertically and pitch over slowly, or you'll flatten out too quickly and not go to space today. How quickly you can pitch over is going to be highly dependant on your liftoff TWR. Since gravity is only ~2% lower at that altitude than at sea level, it's not going to make much of a difference. You'd need to purpose-engineer the vehicle to take advantage, and even then I still don't think you can hit 30% reduction overall.

[lajoswinkler]

Pile of poop.

We don't have the technology to build slender structures of this height. Yes, we could reach 20 km, but it would take unpractically thick and wide lower parts.

Patent trolling, that's it.

[Belphegor]

apart from all the questions that arise about the possibility if this thing if it would actually exist.. how the feg will they handle construction? typically they would use a heavy duty helicopter or a roof mounted crane that moves up as more segments are added.. helicopter is obviously out of the question so good luck finding any kind of gyroscope thingy that can balance a tower with 20km worth of steel cable + building materials hanging off the side. who will put it together, how will they pull that off wearing a full atmospheric suit, and where are they going to find contractors willing to send employees into a huge unfinished experimental tower like this..

even if they manage keep the tower straight what kind of structural material is not going to buckle under the immense weight and how will this in any way be 'inflatable' and stable at the same time? they can never ensure that it won't bend as there is always the chance of minor technical problems or a power outage which would be catastrophical.

how about the temperature differences? over 20km length with variating temperatures there should be massive tolerances (combined) to allow for stretching/shrinking of materials which in turn cause structural weakness.

and what kind of behemoth pump are they going to use to get water/fuel/air up there? the pressure inside the plumbing will be enormous and thus the plumbing will have to be extremely heavy only adding to the problems

i'm not an expert or engineer but i don't see this happening, it's physically impossibru with building materials found on earth. maybe not to create a 20km tall structure, but one that's perfectly stable and can support a lot of weight, no.

Edited August 18, 2015 by Belphegor

[RainDreamer]

how the feg will they handle construction?

Copy and paste from the patent for your viewing pleasure. Doesn't mean it is possible, mind you, just that this is how they thought they will build the thing:

FIGS. 7A and 7B illustrate methods of constructing the space elevator tower 10. It is to be appreciated that the construction methods of the present invention are not limited to the following examples, and that features of the following configurations may be combined to produce further variations of the construction methods without departing from the scope of the present invention.

In the method shown in FIG. 7A, the elevator core structure 12 is erected vertically using a mechanism that extrudes core segments 14. Pods 24 containing control and stabilization machinery are embedded in the elevator core structure 12 as it is extruded by a roller system 995 from a stack of similar pods 24. Gas and power conduits 964 are lifted with each pod 24. The core segment walls and pressure compartments are formed as an extrusion molding of a liquid core material 996. Optionally, a winding mechanism 998 embeds fibers into the elevator core structure 12 in order to increase the elastic resistance of the structure. Pneumatic pressure and a roller mechanism may be used to raise and lower core sections.

FIG. 7B shows an alternative construction approach where core segments 14 are raised by means of a climbing construction elevator 899 that grips the external surface of the existing elevator core structure 12 as it raises and installs segments section by section. Advantageously, core segments 14 equipped with stabilization systems (not shown) may be energized by means of an umbilical connector 897 such that the new core segment 14 may be raised completely above the construction elevator 899 and installed on the existing elevator core structure 12 by means of a horizontal track (not shown) installed on the top of the construction elevator 999. The center of mass of the combined system may be adjusted actively during the core segment installation in order to maintain it over the elevator core structure's 12 surface footprint and to provide support for the elevator core structure 12 in the presence of external disturbance torques.

[Belphegor]

Copy and paste from the patent for your viewing pleasure. Doesn't mean it is possible, mind you, just that this is how they thought they will build the thing:

interesting. i think that the people they put in charge of designing all these 'mechanisms' and putting them to practice is going to have a permanent headache after this project