what kind of space mission would cause the same buzz as apollo?

[hamster_nz]

Nice perpetual motion machine they have there! Are they actually serious?

I would expect that any tidal effects in a 40,000km long ring would rip it all apart. It would also be inherently unstable - any slight deviation from perfect will cause thing to do downhill very quickly.

How do people get the money and time to propose such things?

It's not perpetual, it requires energy to keep the inner ring spinning.  This is not about cheap, it's about what's possible with today's materials and known physics.  Launch costs aside, it is still easier than a space elevator which needs a material longer than the distance to geostationary orbit with a cable with the tensile strength to make it that far.

Quick back-of-the-head calculations, ignoring that the whole thing would be dynamically unstable...

- Carbon fiber density is about 2 grams per cm^3

- A 1m x 1m box section, with paper-thin (0.1mm) walls is about 5cm^2 in cross sectional area, so would be about 0.8 kg per linear meter. Call it 1kg per meter, or 1 ton per km.

- The earth's equator is 40,075 km - 40,075,000 m.

- The weight of a paper-thin 1m x 1m box section to go around the world is 40,075,000 kg.

-  Falcon 9 can lift 22,000 kg to LEO, at a cost of $50M per launch. Assume that all of this payload can be used to build the ring.

- It will take ~1,800 launches, at a cost of $90 billion, to get the raw material for a 1m square paper-thin orbital ring into Low earth orbit.

Once it is built and you have 40,000 tons in orbit. You want to speed it up to support any wright that may be  'hung' from it.

Because centripetal acceleration is  f=v^2/r, you have to move something 1.4x as fast to speed to double the acceleration/force. Low earth orbit is ~8 km/s, so this 40,000 ton paper-thin structure would need to be accelerated to ~11 km/s.

After all this work, each meter of of ring would only be able to generate 1 kg of 'lifting' force. It it is at altitude similar to the ISS, the lifting force from 400km of ring would be needed to support the weight of a 400km box section that touches the ground. 

-

[cdev]

This is why a space elevator is so appealing if some way can be thought of to make it a reality, the cost suddenly becomes affordable.

Of course it's appealing, but... the laws of physics are against it. It's not just finding a material that can hold up its own weight, how would you install it. You can't start at the ground and work upwards and you can't start in space and work downwards.

(maybe they can start from the top of a really tall mountain)

A rail gun in a really deep shaft might be a better idea for launching heavy stuff. With a rail gun a rocket could be moving at several times the speed of sound before it even needs to fire its engine. It's like taking away a whole booster stage from a conventional rocket.

Its like they say, the devil is in the details!

[Nominal Animal]

But don't you think its a bit like not building steam technology because someone thought direct combustion technology was possible?

I would think all the knowledge accumulated of space logistics, control systems and materials would still be useful if fusion power was developed for space propulsion uses.

Oh, I definitely think we should research both fusion and fission technology; the materials physics advancements are probably worth the effort alone!

As an example, raw natural gas is pumped using pumps that are essentially milled from solid blocks (of about a cubic meter) of monocrystalline aluminium; not cheap. It is reasonably resistant to the corrosion (there's all sort of corrosive gases and gunk in the raw natural gas), and its lightness allows the turbine to rotate at high RPMs without tearing itself apart.  Many of the needs for materials used for such turbines are the same as the needs in both fission and fusion reactors.  Simply put, if you find a material that works for one, it will almost certainly be useful for the others, too.

For residential areas, I'd much prefer smaller self-contained nuclear reactors, dug into ground, than long high-voltage transmission lines.  Perhaps it is not feasible on Earth because we need to worry about crazies that wish to harm and kill innocents, but on the Moon or on an asteroid, such fission reactor tech is an absolute must.  (If you mined asteroids for heavier elements -- and that makes sense if you just somehow get to high Earth orbit first -- you'd probably find enough fissile materials to power such reactors "for free".)

As to getting into orbit, NASA's goal of less than $100 USD (per kilogram of payload to Earth orbit by 2040 is optimistic, but not completely unrealistic.  22.8 metric tons to LEO cost $50M USD on the Falcon 9 in 2018, or about $2200 per kg.  It was ten times that in 2000, and almost ten times that again in 1980, so something like $200 per kg to LEO in 2040 is in line with the developments during the last sixty years or so.  If we were smart, we'd launch small tugs that could redirect small metallic asteroids (fragments more like) to high Earth orbit, for use in orbital manufacturing in a decade or so.

[Mr. Scram]

Quick back-of-the-head calculations, ignoring that the whole thing would be dynamically unstable...

- Carbon fiber density is about 2 grams per cm^3

- A 1m x 1m box section, with paper-thin (0.1mm) walls is about 5cm^2 in cross sectional area, so would be about 0.8 kg per linear meter. Call it 1kg per meter, or 1 ton per km.

- The earth's equator is 40,075 km - 40,075,000 m.

- The weight of a paper-thin 1m x 1m box section to go around the world is 40,075,000 kg.

-  Falcon 9 can lift 22,000 kg to LEO, at a cost of $50M per launch. Assume that all of this payload can be used to build the ring.

- It will take ~1,800 launches, at a cost of $90 billion, to get the raw material for a 1m square paper-thin orbital ring into Low earth orbit.

Once it is built and you have 40,000 tons in orbit. You want to speed it up to support any wright that may be  'hung' from it.

Because centripetal acceleration is  f=v^2/r, you have to move something 1.4x as fast to speed to double the acceleration/force. Low earth orbit is ~8 km/s, so this 40,000 ton paper-thin structure would need to be accelerated to ~11 km/s.

After all this work, each meter of of ring would only be able to generate 1 kg of 'lifting' force. It it is at altitude similar to the ISS, the lifting force from 400km of ring would be needed to support the weight of a 400km box section that touches the ground. 

-

I don't think the idea is to shoot everything up there from Earth. There's plenty of stuff up there without insane launch costs. Not needing to go through an atmosphere and escape a somewhat deep gravity well makes a huge difference.

[Fungus]

Quick back-of-the-head calculations, ignoring that the whole thing would be dynamically unstable...

Would they whiplash the planet when they break up?

[hamster_nz]

Quick back-of-the-head calculations, ignoring that the whole thing would be dynamically unstable...

- Carbon fiber density is about 2 grams per cm^3

- A 1m x 1m box section, with paper-thin (0.1mm) walls is about 5cm^2 in cross sectional area, so would be about 0.8 kg per linear meter. Call it 1kg per meter, or 1 ton per km.

- The earth's equator is 40,075 km - 40,075,000 m.

- The weight of a paper-thin 1m x 1m box section to go around the world is 40,075,000 kg.

-  Falcon 9 can lift 22,000 kg to LEO, at a cost of $50M per launch. Assume that all of this payload can be used to build the ring.

- It will take ~1,800 launches, at a cost of $90 billion, to get the raw material for a 1m square paper-thin orbital ring into Low earth orbit.

Once it is built and you have 40,000 tons in orbit. You want to speed it up to support any wright that may be  'hung' from it.

Because centripetal acceleration is  f=v^2/r, you have to move something 1.4x as fast to speed to double the acceleration/force. Low earth orbit is ~8 km/s, so this 40,000 ton paper-thin structure would need to be accelerated to ~11 km/s.

After all this work, each meter of of ring would only be able to generate 1 kg of 'lifting' force. It it is at altitude similar to the ISS, the lifting force from 400km of ring would be needed to support the weight of a 400km box section that touches the ground. 

-

I don't think the idea is to shoot everything up there from Earth. There's plenty of stuff up there without insane launch costs. Not needing to go through an atmosphere and escape a somewhat deep gravity well makes a huge difference.

Still doesn't help.

Moving something in orbit uses non-trivial amounts of energy. As an extreme case, something that is in Polar orbit needs all it's momentum moved into a different plane, and that takes more energy than getting something into orbit from a standstill.  Likewise dropping something down from a higher orbit needs to have the excess kinetic energy removed.

As an example, once in orbit a 110,00kg Space Shuttle Orbiter with 21,660kg of OMS fuel would use it all (including the stuff it needs to deorbit and come home) to change the orbital inclination by around 3 degrees.

So using space junk is more of a fantasy than actually launching stuff.

[Kilrah]

This is not restricted to space missions. Looks like nothing much get people excited over great human achievements anymore. Except maybe the FIFA world cup.

A lot of the need for fantasy imagination has been removed from the population since the Apollo days. These days people can sit down in front of a 50" screen and see almost anything without the need to fill in any details mentally.

Even more importantly, higher levels of education and access to information. Back then you could "wow" anyone even with trivial things since they'd never have heard of it and wouldn't have a way to dig into a subject without months of studying. Nowadays people are more aware of what's around them and you can get detailed info on just about anything in a minute. And with everything that has been achieved everybody now knows that anything is possible if you throw enough money and time at it, so the "magic" aspect is lost.

Also, Apollo was just a multi billion dollar marketing operation of such a massive scale that no one has ever repeated. Pretty sure an equivalent could be done with just about any subject if presented the right way with the same massive communication investment, but no one's seen a reason to go at it again.

[Mr. Scram]

Still doesn't help.

Moving something in orbit uses non-trivial amounts of energy. As an extreme case, something that is in Polar orbit needs all it's momentum moved into a different plane, and that takes more energy than getting something into orbit from a standstill.  Likewise dropping something down from a higher orbit needs to have the excess kinetic energy removed.

As an example, once in orbit a 110,00kg Space Shuttle Orbiter with 21,660kg of OMS fuel would use it all (including the stuff it needs to deorbit and come home) to change the orbital inclination by around 3 degrees.

So using space junk is more of a fantasy than actually launching stuff.

Changing inclination is relatively expensive, especially when done at higher speeds. LEO is rather high speed in that regard. Higher orbits are much more efficient. Once you're up there, getting around is much easier.

[rdl]

Changing inclination is relatively expensive, especially when done at higher speeds. LEO is rather high speed in that regard. Higher orbits are much more efficient. Once you're up there, getting around is much easier.

Those charts illustrate pretty well what I said earlier that getting onto low Earth orbit is actually the hard part, at least as far as delta V is concerned. Of course, anyone that has played with Kerbal Space Program has known this for years.

[Nominal Animal]

As an example, once in orbit a 110,00kg Space Shuttle Orbiter with 21,660kg of OMS fuel would use it all (including the stuff it needs to deorbit and come home) to change the orbital inclination by around 3 degrees.

So using space junk is more of a fantasy than actually launching stuff.

No, you've got it bass-ackwards, kinda.  Earth is a significant gravity well, and the Sun is even bigger one, and you can use that to your advantage when tugboating stuff from the asteroid belt. Essentially, you initially need to reduce their orbital velocity to get them to an orbit that passes close enough to Earth for orbital capture. It would be easier if we could use Earths atmosphere for aerobraking, but humans tend to dislike having big stones hurled at their planet; Mars and Venus are alternatives, but the tugboat needs pretty fine control then.  Similarly for the outgoing trajectories and gravity assists.

Look into Interplanetary transport network (silly name, good paper) and Hohmann transfer orbits.

Simply put, for some of the asteroid belt asteroids, the cost of tugging one back to Earth is basically a function of how fast you want it.  If you are willing to wait a decade or two, the cost (for the entire endeavour) is likely to be rather small, something like a manned moon landing perhaps for a hill-sized asteroid; but it depends highly on the asteroid chosen.

[hamster_nz]

Changing inclination is relatively expensive, especially when done at higher speeds. LEO is rather high speed in that regard. Higher orbits are much more efficient. Once you're up there, getting around is much easier.

Sure, but it doesn't make the Orbital Rings any more feasible.

Add another 5,277 tonnes of material to this 1m x 1m x 40,000,000 m hoop, pushing the ring out from 160km to 1,000km above the Earth (just about where the radiation belts starts - any higher and you will be in an intense radiation zone). This reduces orbital velocity a little from 7.8km/s to about 7.35km/s. Even though it is slower it still takes more energy to lift material into this orbit, and now the towers used to access the ring need to be 1,000 km tall...

The other thing is stresses in the Ring. The ring needs to be spinning a little faster than orbital velocity, so it is pulling 'outwards' evenly around the hoop and can do lifting. Say we spin it 5% faster, so each kilogram of hoop will have 1N of force away from the earth. If you sum up all the forces in the ring they balance out to zero, so at first glance it seems to be very nice.

Now imagine cutting the planet-sized ring in half and sum up the the force vectors for each kg of each half. This will quickly convince you that this paper-thin structure has massive internal stresses - I can't be bothered to do the math, but it will be of the order of 20,000,000 N of force in the 1m x 1m section (with its 0.1mm paper-thin walls). This ~10x more than pure carbon fiber can withstand, and is about the strength of carbon nanotubes in reported tensile in mm-scale experiments. Definitely not achievable by using salvaging space junk, or captured piles of rock.

And given all this 40,000 tons of stuff in space, the Orbital Ring is still mostly naked.

Not convinced -  still looks like pure fantasy to me!

[coppercone2]

what if you made a giant reel of the carbon material so it can be pulled up to orbit slowly? is this feasible at all? like unraveled. Then you would not need high peak power, only some thursters to prevent your construction platform from being pulled down?

can it be spliced if damaged during transit?

[Domagoj T]

Pulled up from Earth surface? Pulled by what? That would imply either a preexisting cable attached to a "fixed" point in geostationary orbit (a huge mass), or an extremely high specific impulse rocket with high thrust capable of efficiently running in atmosphere for a long time. Neither exists.

As for the original question, of what would it take to create a buzz, I have an answer. Launch a couple of those Kardassians. They seem to interest the masses. Once the viewership ratings drop, just blow up a rocket.

[coppercone2]

you are going to need some kind of flying factory to make something that orbits the earth.

i assume trying to pull up carbon fiber with all the wind and everything would still require alot of energy. maybe you can reduce it some what by using a intermediate flying platform like a nuclear powered airplane. And beam microwave/laser energy to the platform or put a reactor on it to power some ion thursters (but I think they are too weak atm). Not sure how many you would need. But you can put them on something stiff for a wide area platform that has some pull on it.

nothing in this thread exists. what is your point in saying that

[Fungus]

what if you made a giant reel of the carbon material so it can be pulled up to orbit slowly? is this feasible at all? like unraveled. Then you would not need high peak power, only some thursters to prevent your construction platform from being pulled down?

Doesn't matter how it goes up, the total energy needed is the same.

Having a long string being pulled on by wind sounds more difficult though.

[coppercone2]

can't you get higher efficiency at low impulses though?

there are no insane power demands if you can get a balanced system going, so normal energy can be used rather then big rockets.

if you get a big nuclear powered flying platform (think like a big version of the airforce nuclear reactor powered b52) you could avoid the thicker winds. And deliver stuff to the platform as it flies around.

nuclear reactors, electric motors and ion thrusters might be safer, more environmental and cheaper then giant rocket barrages.

even if you threw massive money into rockets think of all the pollution from combustion. I think you need the power of the atom.

Also no wasteful gigantic super capacitor banks for earth based rail guns and stuff. maybe you can shoot stuff to high altitudes to be captured by some kind of skyhook system to save fuel and lessen energy requirements. Recycle the parachutes or whatever. I don't know how high a nuclear powered space platform could fly, like 50000 feet? so you shoot stuff up 60k and have it be captured by drones that bring it to the reel system.

you deliver material to be hoisted to the flying platform like mid-air refueling or ballistic midair skyhook recovery and then it gets mechanically transferred to the space platform. It would need to be far away enough to match the air platform speed, then the materials can be woven into the ring or whatever else you wanna build up there and moved around in zero gravity.

If you have a flying platform and transfer material through some kind of railgun that is drone captured you eliminate alot of flight hours, risk, maintenance, etc.

Then you can also possibly make solar panels in space made out of the carbon material (they have CNT solar panels right?) too. then you start to get some kind of dyson ring orbiting earth eventually that can adjust itself with ion thursters that use the tubes as fuel. It would be like a big yarn powered machine.

You can make all sorts of shit in orbit from pulled up CNT. Electronics, solar panels, structural stuff, fuel. You can even add small amounts of materials on it to be hoisted up there and carefully removed (i.e. required for semiconductor doping, etc).. if there is high flow you might be able to get a big of payload on the string itself. You would just need efficient machines to get it off.

I dunno if you can tie hot dogs to a string of carbon nanotubes to pull them into orbit but maybe vienna sausages? 

If it really gets going you can put ion spray machines to put some coatings on them maybe? i dunno how tight the spec is with the tensile strength, I assume you can jury rig something if they considered making a ridiculous space elevator with this. I am not saying coat the thing but maybe introduce a few meters (no idea on the limits here) that have palladium spray or whatever you need on it.

[apis]

Once you're out of the atmosphere you can use skyhooks to move up and down in the gravity well.

Production will be done in space, and on the moon. That's why we need a moon base, it's much easier to operate from the moon. 

https://en.wikipedia.org/wiki/StarTram 

https://en.wikipedia.org/wiki/Launch_loop

For $30 billion, with a larger power generation capacity, the loop would be capable of launching 6 million metric tons per year, and given a five-year payback period, the costs for accessing space with a launch loop could be as low as $3/kg.[5]

[apis]

The only comparable technical change that has occurred in the fifty years since is the microelectronics revolution.  Which when you get right down to it isn't all that exciting.  You can replace stop motion animation, be bugged on the phone at all hours, and type your own documents instead of having a professional do it.  You can listen to music in your car and watch TV at home in higher and higher resolution so you can see a higher percentage of advertisements done in higher resolution.

That's a bit unfair isn't it? People now walk around with super computers in their pockets, wirelessly connected to a global international data network, there are self driving cars around the corner, etc.

Medical science has made lots of breakthroughs, DNA sequencing of the human genome for example, we are beginning to understand how the cells work on a molecular level which opens up the possibility of curing cancer etc.

Maybe not as amazing as it was back then, but some things are pretty exciting now as well.

The vast majority of those pocket supercomputers are running Facebook, Instagram and YouTube, while the two way wrist radio that effectively is transmitting and endless stream of natter.

The global data network has enabled, not quashed the various anti-vaxxers, flat earthers, Holocaust deniers and the like.

Is it really exciting to gossip with people all over the world instead of just those in your neighborhood?  Except for weirdos like us who don't find similar interests locally.

Was it different before though? Wasn't lots of people misguided and misinformed before? What noble and enlightened activities did people end up using their transistor radios, televisions, t-fords, aircrafts, wristwatches and nuclear power for? People haven't changed for thousands of years, it's just knowledge and technology that keeps improving.

You wrote that "They had watched the diseases that killed their brothers and sisters in childhood driven into retreat" and that is still true today, and it's pretty exciting to be cured of various ailments that would have killed you 30 years ago.

And I do think it's pretty exciting to carry around the equivalent of several libraries in my pocket and to be able to search and find relatively accurate information about almost anything in less than a minute. You can also find inaccurate information about almost anything, but if you manage to sift through the noise it's pretty amazing. In combination with GPS I can get a map/satellite image showing exactly where I am and the shortest route to where I'm going. Navigation used to be non-trivial.

This forum is full of people from every continent (Antarctica?) having casual discussions about electronics and technology. Pretty amazing. My father might have travelled abroad before but he never really talked (or talks) to anyone outside the town where he lives. There is still a language barrier though, so it's mostly from English speaking countries, but maybe machine translation get good enough soon that it is possible to have a multi language forum?

[T3sl4co1l]

As an example, raw natural gas is pumped using pumps that are essentially milled from solid blocks (of about a cubic meter) of monocrystalline aluminium; not cheap. It is reasonably resistant to the corrosion (there's all sort of corrosive gases and gunk in the raw natural gas), and its lightness allows the turbine to rotate at high RPMs without tearing itself apart.  Many of the needs for materials used for such turbines are the same as the needs in both fission and fusion reactors.  Simply put, if you find a material that works for one, it will almost certainly be useful for the others, too.

I'd like to hear more about this -- I know single-crystal castings are used with superalloys for extremely demanding purposes, e.g. turbine parts.  The Fe-Ni-Co-etc. superalloys are homogeneous (solid solution) alloys, so this works nicely despite the large alloying percentages.  I wasn't aware it was used (or useful) with aluminum.  It seems to me, aluminum tends to have poor solubility for alloying elements, hence most alloys contain intermetallic grains which provide the strength.  Is it really worthwhile to make a single crystal with what little will dissolve in it?  Once made, though, I can see precipitation hardening being very effective.

Offhand, I see a few search results offering 99.999% single crystal aluminum, which is going to be about as strong as butter (literally).  Don't think that's what's being used here.

Also a bit surprised that something more conventional isn't used, like Inconel, maybe with a plating like pure nickel, or a ceramic coating or something.  Well, anything that has to be coated, would be more prone to flaking or damage and eventual failure than a bulk-resistant material, of course.

Tim

[In Vacuo Veritas]

Veritas Vacuo, your stupidity and trolling is becoming highly annoying.

Yes, you are right. I must become intelligent by babbling sci-fi nonsense like you. This is the path to intelligence.

Space Elevators. Space manufacturing! Asteroid mining!

I can feel my IQ rising already! Oh those silly people with their real-world practical engineering! So myopic!

We, the readers of sci-fi, know The Truth (tm). We have the Real Knowledge, given to us by sci-fi writers in high school.

Thank you for setting me on the Right Path to Holy Salvation In Space.

I will immediately print out leaflets and go door to door to tell people the Good News!

Hey poor, you don't need to be poor anymore! Space is here!

Just like OTRAG in the 1970s! Oh wait.... Just like Solaren! Oh wait... Just like the 1997 Space Hotel! Oh wait...

[cdev]

Have you ever read "The Sirens of Titan" by Kurt Vonnegut, Vacuo?

I think you'd enjoy it, from what you just said.

[apis]

Silly man



yet it moves.

[Fungus]

Production will be done in space, and on the moon. That's why we need a moon base, it's much easier to operate from the moon. 

Good point.

(although factories to make all the stuff needed will somehow have to be sent to the moon first)

[coppercone2]

the nature of in vacuo verditas posts in this thread remind me of the movie "carnosaur 2"

its like violent ambushes combined with weird annoying whistling noises and generally low quality, potentially a rip off of a good argument. it has some structure and a script but you can't take it seriously because he did not do any work (i.e. inserting rubber dinosaur costumes in place of xenomorphs in the little known alien ripoff).

a classic troll using a flow chart.

[apis]

Production will be done in space, and on the moon. That's why we need a moon base, it's much easier to operate from the moon. 

Good point.

(although factories to make all the stuff needed will somehow have to be sent to the moon first)

Yes, the difficulty is to get the ball rolling. There is a lot of raw material on the moon though, so you don't need to harvest asteroids in the beginning. Energy shouldn't be that hard either (solar is obviously possible, maybe fission if you can find uranium). There are some pretty amazing manufacturing machines today (MIT fab lab!), if you could get a few of them to the moon you might be able to begin building up a basic infrastructure. Small parts can be brought up from earth.