Which proposed space technology do you find the most ridiculous/impossible?

[p1t1o]

6 minutes ago, Bill Phil said:

More than 50, about 80%. It's crazy, but if you over-engineer it enough, it would work, and that's the insane part. Even a small Orion has great performance, and there is a variant called "mini-mag Orion" that doesn't use bombs.

Yes I thought I saw 80% quoted somewhere but wasn't confident enough in that memory to quote it.

I've seen the papers and things that support it, but I am having a bit of a crisis of faith, if you like, it just doesnt "ring true" like most sciencey things do. Consider what it means - that of the whole sphere, somehow only 20% of the detonation energy is released from approx 90% of that sphere, and the remaining *80%* concentrated into the small arc towards the pusher. Its far more complicated than that, I know, but even so...

My brain no be happy with this!

Am completely aware that I might just have to live with it , am 100% prepared to accept that it works despite my point of view...what kind of scientist would I make otherwise? But they're gonna have to actually build one before I can really get behind it - Or just off to the side preferably

Mini-mag seems to be a different propulsion concept altogether really, have no similar qualms with that one.

For me, its Daedalus or bust!

[Bill Phil]

11 hours ago, p1t1o said:

Yes I thought I saw 80% quoted somewhere but wasn't confident enough in that memory to quote it.

I've seen the papers and things that support it, but I am having a bit of a crisis of faith, if you like, it just doesnt "ring true" like most sciencey things do. Consider what it means - that of the whole sphere, somehow only 20% of the detonation energy is released from approx 90% of that sphere, and the remaining *80%* concentrated into the small arc towards the pusher. Its far more complicated than that, I know, but even so...

My brain no be happy with this!

Am completely aware that I might just have to live with it , am 100% prepared to accept that it works despite my point of view...what kind of scientist would I make otherwise? But they're gonna have to actually build one before I can really get behind it - Or just off to the side preferably

Mini-mag seems to be a different propulsion concept altogether really, have no similar qualms with that one.

For me, its Daedalus or bust!

Well, you'd probably need to be a nuclear physicist to fully understand the forces at work in the bombs... And even that may not be enough.

Edited October 6, 2016 by Bill Phil

[mikegarrison]

The thing about the Orion is that using chemistry to propel manned spaceships is not very practical for anywhere beyond LEO. Just look at Apollo. Consider that massive stack of rockets necessary to send three guys crammed into a couple of aluminum cans to the moon for a few days.

So if we are ever going to send sufficiently large ships to anywhere, we're going to need to use nuclear power. Orion is the only known propulsion system that can provide high thrust and high ISP together. More than that, it actually works better as the mass of the ship increases.

It all sounds crazy, but unless we have some kind of real breakthrough, it may be our best option.

[todofwar]

10 hours ago, mikegarrison said:

The thing about the Orion is that using chemistry to propel manned spaceships is not very practical for anywhere beyond LEO. Just look at Apollo. Consider that massive stack of rockets necessary to send three guys crammed into a couple of aluminum cans to the moon for a few days.

So if we are ever going to send sufficiently large ships to anywhere, we're going to need to use nuclear power. Orion is the only known propulsion system that can provide high thrust and high ISP together. More than that, it actually works better as the mass of the ship increases.

It all sounds crazy, but unless we have some kind of real breakthrough, it may be our best option.

But it involves dumping tons of radiation into the atmosphere. Also, a Physicist(tm) told me that it can't really work in vacuum because the heat has nothing to expand against. Well, I guess unless you shoved a tank of liquid nitrogen around the nuke, then the gasses can expand and act like the atmosphere. edit: ignore that part.  If Orion becomes a thing, it will only launch a half dozen times max, and even then it will leave a section of the earth uninhabitable. So maybe if we have a comet coming towards earth and we have enough time to attempt a generation ship or some kind of weird scenario like that.

Edited October 8, 2016 by todofwar

[Nuke]

as much as i wanted to go with em drive i went with the space elevator. em drive is hit or miss, either it works or it dont. they are really both sides of the same coin. theory says the space elevator can work, but its insanely impractical. meanwhile em drive shouldn't work at all in theory, and if it does it will make a damn fine probe engine. if it doesnt work you can chuck it out the rear and get some meaningful thrust out of it.

[KerikBalm]

EM drive seems patently impossible and ridiculous.

In other cases, some things seem more "impossible" than others, despite what Nibs says. If one device needs a tensile strength 5% higher than anything we know of, and one needs a tensile strength 500% higher than anything we know of, one is clearly more impossible. If we look at the margins, the one with the least negative margin is the least impossible of the impossible ones.

The launch loop doesn't seem impossible, just very very ridiculous to build. As to the instability when going from 0m/2 to operating velocity... if we imagine a massive amount of rocket vehicles attached to the track thrusting and contributing active stability, it may be possible to build.

A space fountain also seems quite ridiculous, but not impossible. Thentheres the space elevator... even if we managed to make materials strong enough to build one, construction would be a nightmare. Then once built... it wouldn't be very practical because it would take a looooong time to ascend and descent to GSO. The number of cars on it would be limited due to stability concerns....

For the magntide of effort for a space elevator, I prefer something like a space gun with a very high elevation exit. Could be magnetic, could have a ramjet vehicle inside, whatever, this one I don't think is as absurd as the others.

Orion: Not on earth... maybe with pure fusion bombs and a ground based laser to detonate them....

But no one has mentioned my favorite, an orbital ring:

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

Basically a cable going around the earth at faster than orbital velocity, held in place and stabilized by various tethers that are essentially mini-space elevators. The required tensile strength is much much lower: Steel cable would work fine. The system could also have built in redundancy.

Numerous stations all around the world + shorter distance up = much more capacity than what you cna get with a space ladder/elevator.

Of course, it would be massively complicated to build

[todofwar]

4 hours ago, KerikBalm said:

EM drive seems patently impossible and ridiculous.

In other cases, some things seem more "impossible" than others, despite what Nibs says. If one device needs a tensile strength 5% higher than anything we know of, and one needs a tensile strength 500% higher than anything we know of, one is clearly more impossible. If we look at the margins, the one with the least negative margin is the least impossible of the impossible ones.

The launch loop doesn't seem impossible, just very very ridiculous to build. As to the instability when going from 0m/2 to operating velocity... if we imagine a massive amount of rocket vehicles attached to the track thrusting and contributing active stability, it may be possible to build.

A space fountain also seems quite ridiculous, but not impossible. Thentheres the space elevator... even if we managed to make materials strong enough to build one, construction would be a nightmare. Then once built... it wouldn't be very practical because it would take a looooong time to ascend and descent to GSO. The number of cars on it would be limited due to stability concerns....

For the magntide of effort for a space elevator, I prefer something like a space gun with a very high elevation exit. Could be magnetic, could have a ramjet vehicle inside, whatever, this one I don't think is as absurd as the others.

Orion: Not on earth... maybe with pure fusion bombs and a ground based laser to detonate them....

But no one has mentioned my favorite, an orbital ring:

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

Basically a cable going around the earth at faster than orbital velocity, held in place and stabilized by various tethers that are essentially mini-space elevators. The required tensile strength is much much lower: Steel cable would work fine. The system could also have built in redundancy.

Numerous stations all around the world + shorter distance up = much more capacity than what you cna get with a space ladder/elevator.

Of course, it would be massively complicated to build

But would such a ring be stable? I thought those kinds of things will ultimately crash into what they're orbiting. Or maybe that's none rotating disks. .. rotational reference frames were always my weakest subject in physics for some reason, some kind of mental block. 

[Emperor of the Titan Squid]

On October 8, 2016 at 9:31 AM, todofwar said:

But it involves dumping tons of radiation into the atmosphere. Also, a Physicist(tm) told me that it can't really work in vacuum because the heat has nothing to expand against. Well, I guess unless you shoved a tank of liquid nitrogen around the nuke, then the gasses can expand and act like the atmosphere. edit: ignore that part.  If Orion becomes a thing, it will only launch a half dozen times max, and even then it will leave a section of the earth uninhabitable. So maybe if we have a comet coming towards earth and we have enough time to attempt a generation ship or some kind of weird scenario like that.

The idea is that there would be propellant on the front of the bomb, which would be vaporized and blasted against the pusher plate. Also, the general idea is to construct it in lunar orbit, and launch it from there. SSTOs would be good as space access systems, mainly for people, because of rapid turnaround.

Edited October 9, 2016 by Emperor of the Titan Squid

[magnemoe]

1 hour ago, todofwar said:

But would such a ring be stable? I thought those kinds of things will ultimately crash into what they're orbiting. Or maybe that's none rotating disks. .. rotational reference frames were always my weakest subject in physics for some reason, some kind of mental block. 

Ring would be stable, its meta-stable as it is and the elevators would stabilize it. 
Yes the obvious issue is the rotating core or magelv train, the entire thing sounds like an train wreck larger than earth. 

Then dealing with dangerous systems you want it to fail safe. In many cases like an flying plane you build in redundancy like multiple engines, multiple control systems. an APU, Still you have plane crashes, More dangerous systems like nuclear power plants has even more level of redundancy. You are not talking belt and suspenders here, Put an coverall on top then an long dress. 

Now the orbital ring can not have fails in the magelv track or its power supply. Any fail would have the rest of the train hit the impact site. 
The kinetic energy of the crash would make it very hard to contain it.
 

[KerikBalm]

Its true that just a single solid ring orbiting something (like a ringworld) is not stable. The tethers to the ground are what keep it stable. In theory, you only need 2 such cables 180 degrees apart.

Luckily, as everything is going faster than escape velocity, if theire is a failure, everything goes outward... perhaps to escape velocity, except for the stationary maglev stations, which would spectacularly fall to the ground.

It would need to be designed such that one station could fail without taking the whole ring with it. If the maglev and backups on one stationed failed, you'd have to let that station fall to the ground without impacting the ring in such a way as to destroy the ring... which would make every other station fall as well and release the ring(or what used ot be a ring) as space debris.

Its basicall a launch loop extended all the way around the planet into a ring. Unlike a launch loop, you could start your construction in orbit with a "constellation" of cable spool satellites, you would then link up the satelittes into a ring and use active stability (like ion thrusters) to keep it going, and accelerate the ring... at this point you need some amazingly fast connection to prebuilt ground stations before your propellant runs out.

So as you accelerate the ring, you already have small maglev stations on it that "go backwards" relative to the ring's rotation, backwards fast enough to be geostationary.... at this point the ring is very small, not going so fast, and the magleve stations are very small. The small maglev station drop cables (lets say... 400 miles of cable? 500?) and those get secured to the prebuilt ground stations... stabilizing the ring.

At this point, it "bootstraps" itself as you then use the small orbital ring infrastructure to lift up thicker cables for the ring, parts for bigger maglev stations, etc etc...to build a more robust higher capacity orbital ring.

The scale is much bigger than a launch loop, but the ability to do a lot of stuff in orbit seems to me to make the construction actually maybe easier than a launch loop.

 

But for a launch loop, I wonder if you couldn't have a sort of ground track where you spin the cable up, and then past a certain speed, the cable will start to rise on its own?

Then you use maglev stations to attach all the stabilizing cables you want for when you put it at an even higher speed and add payload to it?

For active stability in the lower atmosphere, these stations can stabilize simply using fans for thrust