Feb 11, 17 / Pis 14, 01 05:55 UTC

Re: A new type of material for building space ships and space elevators!  

Even graphene. A few miles of it pushing into the same spot isn't clever, so will need to spread that force over a wide surface area. To avoid it toppling, this is also likely to require to be set deep into the ground. Really deep, at least 1/3 it's total length. To resist torsional sway, it'll need to sculpted to allow the wind to pass - especially as the wind at different heights can be different directions. It's also going to require to be rediculously thick at the base, tapering thinner upper - adding to total weight.

Resonance of a structure that long alone would be problematic and represent a engineering problem I'd not like ot solve. Earthquakes would be almost impossible to counter.

As a material graphene has many potential uses, and can enhance multiple existing technologies - but I don't see it buliding a space elevator any time soon - building something that long, and keeping it straight is too much of a headache.

Feb 11, 17 / Pis 14, 01 14:13 UTC

EyeR, that's one of the reasons we are building Asgardia, to unite thinkers, scientists and many ideas and step forward on solving those problems. Graphene is a great material but the point today isn't the engineering issues, but the cost of production and quantity of resources make it.

Feb 11, 17 / Pis 14, 01 22:44 UTC

For now, just ignore the getting that much graphene together, and making it the right shape - just consider the core concept. Let's aim for the Kármán line - the commonly accepted boundary of "space". We're talking 100Km long elevator shaft. Sure, graphene is light but I'd not want to be under 100Km of it.

Realistically you'll probably want another 30Km or so into the floor to prevent topple which also raises problems, but we'll ignore them and just focus on the pressure from all that weight. It needs spreading, and over some serious surface area.

Wind. Different heights will be hit from different directions, preventing buckle or torsion due to this will represent several challenges, as does resonance(which increases in amplitude across the length of a structure. A tiny wobble from an earthquake will turn into savage rocking in much less than a kilometer) and atmospheric drag/friction against the structure at the upper isn't good either.

Space elevator most unlikely to be rendered feasible, IMHO. The only solutions to some of those problems are not sensible to attempt to impliment. And this isn't all the problems... temperatures change etc.

Graphene itself could be muchly better purposed, high quality graphene can make for reasonable to good room temperature supercapacitors. It might be a good bulkhead/crossmember etc for structural purposes in craft/vessels etc. Production can be made a lot cheaper, if existing processes are scaled to industrial proportions. Ultimately, all you should require is a good source of carbon - but some starting points are "easier" than others.

  Updated  on Feb 11, 17 / Pis 14, 01 22:47 UTC, Total number of edits: 1 time
Reason: typo

Feb 13, 17 / Pis 16, 01 09:21 UTC

Maybe we could also consider the design? Maybe something with less resistance, for example something more rounded edges and triagular shaped at the top.

Feb 13, 17 / Pis 16, 01 11:06 UTC

A 100km tall Eiffel Tower? The base would have to be around 35km wide, tie down anchor cables on mini-towers about 30-40km tall at all four corners, if not at 8 points to stabilize it against crosswinds at different altitudes and to prevent sway (still I highly doubt this will eliminate all sway). Anti-vibration stabilizers every 100-200 meters to keep the structure from shaking itself to pieces. As EyeR said, you will need ground anchors, with geothermal gradient being roughly an additional 25*C/km that you dig down. A root structure instead of vertical boreholes might work, but testing for a structure that size would be needed before hand. Regardless of the material used to build it, the sheer amount of material would be enough to build a city in its own rights. This is just for the elevator "shaft", you still have to figure in "car" weight, mechanics used to lift the car (which in my opinion a climbing motor built into the car would be far lighter than the hundreds of km of cable and weight of counterweight needed to offset the car, but carries its own set of risks), as well as any payload going up with it.

Feb 13, 17 / Pis 16, 01 17:54 UTC

"rounded edges" are not enough, it needs to be calculated curvature in order to redirect the wind - and thusly the forces that hits it. kind of like a "air screw" - in an up/down motion more than left/right. The overall shape would also be somewhat oval(like ½ a prop, or the profile cross-section of an aircraft wing) and more than likely heliptical across the 100Km length. Torsional forces over the extent of the 100Km are likely to become problematic, especially at or about the jet stream.

A 35Km wide base sounds about right to me, and like the eifel tower it'd taper inwards as it moves up. A lot of the lower materials can be more conventional to reduce the cost, as well as the geothermal gradient that needs to be countered, there's a thermal gradient in the atmosphere too - it steadily gets colder up until about the mesospause, where the average air temperature moves from -85°C or so up to a possible +1500°C in some parts of the thermosphere, cooling back off again once towards the exosphere.

A "climbing car" could be done easily. The mechanics can be set so in event of failure it locks in place. Servicing/rescue could be interesting. It definitely makes more sense than 100KM+ of cable, and would make it significantly more realistic.

Feb 14, 17 / Pis 17, 01 03:04 UTC

I'd definitely be going climbing car more than cable. Less headache.

Geostatic orbit is densly populated, and would likely pose significant collision risks. 37 klicks sounds a little low to me, the Kármán line, the accepted boundary into space, is at 100 klicks. But a third of the way into space could certainly help. I wager we can get a launchpad floated that high on baloon tho. That should cost a lot less, and be easier to build.

Feb 14, 17 / Pis 17, 01 14:54 UTC

35000km, not 37km, geostationary is extremely far out (relative to other common orbits). You don't have to worry about geostationary collisions, as anything there is static with regards to everything else in that orbit. You would have to worry about collisions with satellites in lower orbits however, as the cable might stretch through their paths.

From what I've read, as seems to be agreement here, materials haven't advanced far enough yet to make this possible.

Feb 14, 17 / Pis 17, 01 18:22 UTC

My bad, misread the comma as a full stop. 37,000 sounds much better. lol.

Still think trying to cover much of the distance with cable - or at least a single one(but multiple introduces complexity and points of failure) - isn't the "best option". I'm not thinking a structure that size is sensible to build, even if it was feasible to build it, honestly. It's likely to have some unforseen impact. Worst case, in the event of structural failure the upper sections - even if light graphene - travelling to the floor should gather enough kinetic energy to cause significant damages. From 100km up it's going to be spreading far.

Something obiting lowering some sort of platform a few km to land in on and be winched up is potentially feasible. But it's still lacking in length to be of realistic usability. Combined with a baloon lifted launch platform it could certainly significantly reduce the requirement for propellant use. Especially if after being winched up a centrafuge was used to launch it up futher. Such a system would kind of perform the function of an "elevator" without any of the associated headaches of the structure, just two smaller, and easier to encompass headaches of the floating launchpad and the orbital platform.

Feb 15, 17 / Pis 18, 01 11:26 UTC

Skyhook is a good proposal to some of the discussed issues https://en.wikipedia.org/wiki/Skyhook_(structure). Basically a big arm that rotates into the upper atmosphere to catch rockets/payloads on the way up, then swings back out of atmo.

Balloon launches (rockoons) can work with very small rockets, but the main downside is they get blown off course quickly, and the size of balloon you'd need for a couple tons of payload would be huge.

Feb 16, 17 / Pis 19, 01 03:54 UTC

The HAV304/Airlander 10 is huge. Have it automated, you can strip some weight in the pressurised hull for humans, controls, seats etc, Use materials like graphene in the structure, take out the V8 weasle lumps and replace them with some electical motors fed by an on-demand hydrogen generator to reduce it's weight from 10 tonnes even futher - cut 5 tonnes off it's payload capacity and you can build a launchpad and add extra renforcements to the cells to it can get to about 30-40 klicks safely. It'd obviously need to be a v. different shape, but long story short, massive floating structures can happen. Blown "off course" is an issue, but it's possible to maintain position "good enough".

  Updated  on Feb 16, 17 / Pis 19, 01 03:55 UTC, Total number of edits: 1 time
Reason: typo

Feb 16, 17 / Pis 19, 01 13:51 UTC

It can only hold 7 tons at a couple of miles up https://en.wikipedia.org/wiki/Hybrid_Air_Vehicles_HAV_304_Airlander_10#Overview, max payload of 15 tons. A standard rocket weighs around 3-500 tons. Something bigger like the delta 4 heavy is up to 700+tons. Like I said, it might be feasible for small rockets, but I doubt it would be useful enough to put sizeable payloads into orbit.

The wind factor will add fuel weight as the rocket would have to correct for being in the wrong place, and the slower the floating platform rises, the more corrections you'd need. All resolvable, but obviously at the cost of extra weight/time/money etc.

Feb 16, 17 / Pis 19, 01 18:24 UTC

"Fuel" can be just five of litres of water, which should run the four 25kg hydrogen generators for about four and a half weeks. If that's too short for your tastes, we could use a bigger resevior or more of them. After putting all the effort in to reduce weight, what's a few more kilo. A full launch cycle - floor»air»launch»floor - should be able to take place in much less than 24hrs.

It currently has a low operational ceiling but this is why you make it a few tonnes lighter, and then still skim off it's SLW - to be able to add reinforcements to the helium cells so it can operate in much lower pressures - ie: greater heights. It's not completely unfeasible to expect a maxium possible ceiling of the mesopause. Realistically I think we can get it ½ way into the mesosphere.

The wind as previously mentioned can be countered with electrical turbines, This can also be used to provide more thrust and reduce lift times. A standard rocket might weigh 300+ tonnes, but how much of that is used just moving the entire mass from the floor? I'd suggest at least 200 tonnes of that is spent just getting it going. By starting a lot higher up, and only launching say 2½tonnes of rocket/fuel with 2½tonnes of payload, LEO should be quite easy. Comparing to a traditional chemical launch, at these sort of heights it's going to be a lot slower, but it also weighs significantly less. The thrust is lower, but the thrust to weight ratio is higher - and that really matters. muchly. There's also lesser air resistence due to lesser density and the effect of gravity reduces with distance, it's only 0.2 or so lower but that helps too.

Such is unlikely to be useful for "sizeable payloads" but it'd certainly have uses with reducing cost to leaving atmosphere, for a lot of other applications which is 2/3 the headache. It's also going to be a lot cheaper than the SLS, Delta or Falcon(and an elevator).

Feb 17, 17 / Pis 20, 01 10:41 UTC


Elon Musk, Royal Aeronautical Society, November 16, 2012:

"…it seems like...you're high up there and so surely that's good and you're going at...0.7 or 0.8 Mach and you've got some speed and altitude, you can use a higher expansion ratio on the nozzle, doesn't all that add up to a meaningful improvement in payload to orbit?

"The answer is no, it does not, unfortunately. It's quite a small improvement. It's maybe a 5% improvement in payload to orbit..."

Feb 17, 17 / Pis 20, 01 11:25 UTC

For a completely different "air launch system". Though I had be toying with the idea of electromagetically assisting the launch.

The goal isn't "improved payload to orbit" either, that almost certainly wouldn't be provided by an elevator. The goal, as I understood it, was reduced cost to. Preferably re-usable.