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Magnetic Ring Could Launch Satellites, Weapons
Posted by
kdawson
on Tue Oct 03, 2006 01:44 PM
from the round-and-round-it-goes dept.
from the round-and-round-it-goes dept.
MattSparkes writes, "A new study funded by the US Air Force has suggested a cheaper method of sending satellites (possibly missile weapons) into orbit. A 2-km-wide ring of superconducting magnets would contain and propel a payload, accelerating it over a period of hours, before suddenly flinging the satellite into space at 23 times the speed of sound. The satellites would be engineered to withstand the g-forces encountered (2,000 g), and be cased in an aerodynamic shell. A two-year study has been commisioned and will begin within a few weeks at LaunchPoint Technologies in Goleta, California." New Scientist points out that if such a launch ring were built, it would instantly become "one of the most important targets on the planet."
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"Moon is a Harsh Mistress" anybody?? (Score:5, Insightful)
Re: (Score:3, Interesting)
a_c = - \omega^2 r (Score:5, Informative)
Unless the circle was ridiculously large (probably the size of a continent or better), you're not going to be able to get up to escape velocity before you'd (as a human being) would be crushed by the effects of the centripetal acceleration.
I'm not going to do the math right now, but I'm pretty confident that of the 6,000 Gs they're quoting, most of them are in the radial direction and not in the tangential, so that even if you brought the payload up to speed slowly, you'd still be crushed. It would be just like being in a centrifuge.
Parent
Re:a_c = - \omega^2 r (Score:5, Informative)
The speed of sound at sea level is 330 m/s, and a = v*2/r, so at 23*330 = 7590 m/s you would need r ~ 600 km to get a under 10 g.
Of course, there's going to be a bit of bump when the capsule hits the atmosphere, and there's also the bit of a trick about getting the thing oriented so the capsule if flung upward...
As a satelite launcher this sounds like a great technology, although I'm not sure who would be "targeting" it or for what purpose...advertisers, maybe? Painting thier logos on it or something? Or some guy hiding in a cave someplace that we're supposed to be all afear'd of?
Parent
Re:a_c = - \omega^2 r (Score:5, Insightful)
You don't need to fling the capsule upwards, you need to fling it horizontally such that it doesn't hit anything. To get into orbit you do not go "up", you go sideways as fast as you can. The advantages of being high up are:
Being "in orbit" is essentially falling without ever hitting the ground.
MJCParent
Re:a_c = - \omega^2 r (Score:5, Informative)
The reason why I mentioned pointing it up is that there is a big advantage to passing through the atmosphere as quickly as possible. Firing a capsule out normal to the local vertical will result in minutes being spent in getting to the top of the atmosphere, by which time you will have lost most of the initial velocity, to say nothing of broken all the windows for kilometers around. If you do the math, it takes about 13 seconds to travel 100 km at Mach 23 (just under 8 km/s). So a 30 degree incline nearly doubles that (you get some benefit from the curvature of the Earth) and things get rapidly worse from there on.
As the whole point of my calculation was to show how big the thing would have to be to keep the acceleration below 10 g there is no way a 30 degree incline is going to happen--you've have to have a curve so long that the top of it really would be above a significant fraction of the atmosphere.
Parent
Re:"Moon is a Harsh Mistress" anybody?? (Score:5, Insightful)
Parent
Re:"Moon is a Harsh Mistress" anybody?? (Score:5, Insightful)
Parent
Re:"Moon is a Harsh Mistress" anybody?? (Score:5, Interesting)
Parent
Re:"Moon is a Harsh Mistress" anybody?? (Score:5, Informative)
Peak for shuttle launch is 3Gs, and for Apollo reentry, exceeded 7Gs (source paper with cited sources [ufl.edu]). For a launch abort on the Apollo design, stress would have exceeded 16Gs, and this was deemed uncomfortable, but survivable (albeit with an assumed inability to operate controls during the process). (source LBJ Space Center [nasa.gov].)
So limiting it to 2Gs of total stress is very arbitrary and unnecessary.
Parent
Re: (Score:3)
Re: (Score:3, Informative)
Who says they can't? It could just be that a straight-line version would be prohibitively expensive because instead of needing C magnets to span the circumference of the ring, they'd need N * C magnets to span the distance covered by the circumference times the number of revolutions.
Re:"Moon is a Harsh Mistress" anybody?? (Score:4, Informative)
So they are making a longer track.
The reason the payload has to be built to withstand X,000 G's is because at some point or another, it is going to go off the track and run into a wall of air at very high speed.
Parent
Ablative coating (Score:5, Interesting)
Any compentent aeroshell engineer could design a case that would protect the payload (such as a capsule covered with the stuff they use for ablatively cooling rocket nozzles). The big concern usually with burning through airframes isn't that we don't have materials that can withstand the heat and friction; it is that those materials typically aren't very light-weight or are too expensive.
Besides, once the track is set up, it should be easy to try out new aeroshell designs! One of the stumbling blocks right now is trying to accellerate a test article to high enough speeds. Very often, they stick a test article on a sounding rocket that sends back data during re-entry.
And yes, IAARS.
Parent
Re:"Moon is a Harsh Mistress" anybody?? (Score:5, Interesting)
The track design is based on particle colliders, so the entire thing is evacuated. Part of it is a rough vacuum and part is a hard vaccum (the actual track). The rough vacuum is because they have to limit thermal transfer to their super-cooled superconducting magnets.
The acceleration is actually not linear- it's radial. Going around a 2km track at 10km/s has some hefty acceleration associated with it. When ejected into the atmosphere, the projectile shouldn't immediately slow a great deal, although it will lose a lot of momentum before leaving the atmosphere. The design is a very long and skinny cone, to reduce thermal heating and drag force.
The best thing about this design for a launcher is that it doesn't require a lot of instantaneous power, unlike a linear accelerator. You can accelerate slowly.
Also, did anyone else immediately think of Xenogears when they saw this?
Parent
Re:"Moon is a Harsh Mistress" anybody?? (Score:4, Insightful)
but since we're going in a circle, speed would have a very important effect. the acceleration pushing you back in your seat (the 2-3 gees you mentioned) might not be harmful, but the centrifigural acceleration pushing you out from the centre of the circle could be, as going by the article, you'd be moving at about 28,000 kph, so i would imagine that force could be rather substantial.
Parent
New ad campaign (Score:5, Funny)
Federal Express, when it absolutely, positively has to be there at 23 times the speed of sound *
* Disclaimer: 23 X speed of sound service available between limited destinations. May be subject to 2000g so please wrap delicate items approprately.
Parent
Arrrgh! (Score:5, Funny)
Parent
"Moon is a Harsh Mistress" (Score:4, Interesting)
In the launch-ring article, I noticed the air-resistance problem being mentioned, during the initial acceleration phase.
I might suggest this idea [halfbakery.com] as pointing out a solution to that problem.
Parent
Re:Arrrgh! (Score:4, Funny)
Just a thought; Maybe a good test site might at Crawford Texas?
Parent
Re:"Moon is a Harsh Mistress" anybody?? (Score:5, Informative)
Of modern ballistic launch mechanisms, there are lots of neat options ranging from light gas guns [wikipedia.org] to ram accelerators [wikipedia.org]. I also find the concept of ballistically-launched scramjets [af.mil] to be pretty nifty.
Parent
Lost in space (Score:5, Interesting)
Space burials (presumably of cremated remains). At $200 each (plus cremation) I am sure they could sell a few thousand of these per year. Now if they could only figure out a way to allow living people to withstand 2000g of acceleration, space tourism might actually be affordable.
Re:Lost in space (Score:5, Insightful)
Well, a few thousand cremated bodies would probably fit inside one single launch, so you would need millions to get that price. Because I seriously doubt the $189/kg figure assumes 1 kg payload/launch.
Parent
Re:Lost in space (Score:5, Insightful)
Indeed. Also, accelerating it in a 2km circle over several hours to 23 times the speed of sound is not fraught with peril.
Parent
Re:Lost in space (Score:5, Insightful)
Plus, the containers are already going to have to be strong just to survive normal stresses. I wouldn't be surprised that they already will be specced to survive most catastrophic releases.
I say this because it's important that people not think that radioactive waste is so magically dangerous that we always need to add "just one more layer" of protection before we're somehow 100% from the radioactivity bogeyman, and thus never take advantage of one of the better energy sources we have. It's an engineering problem, nothing more.
Ultimately, this point is moot, because the general public already does see radioactivity as magically dangerous and the magical thinkers are going to put themselves into the situation where they'd rather have the (magically dangerous) waste with them on the planet, but out of sight, rather than actually removed from our living space, but briefly and highly-visibly in the air.
Parent
Re:Lost in space (Score:5, Informative)
Parent
Sounds Good, except (Score:3, Insightful)
that gauss density could be fatal and/or affect instruments.
I know there's a relationship between bird migration and magnetic fields, too, as a lot of them blindly smack into the brick walls at a local MRI center.
Re:Sounds Good, except (Score:5, Informative)
Cute, but you gotta be kidding. I work with a 3T research MRI magnetic. Both the machine and the facility are heavily shielded, and the field drop-off is very steep. While the isocenter of the bore is at 3 Tesla (30,000 Gauss), the 5 Gauss line is only a few meters (about 5 in the axial direction, 3 in the radial direction) from the isocenter. By comparison, a kitchen magnet is maybe 100-250 Gauss.
Parent
How cool is that? Intercontinental catapults (Score:5, Funny)
Mass drivers RULE! (Score:5, Funny)
Yes!
As for it being a target, fuck that. Full steam ahead.
If we're not driving payloads into space at Mach 23 within 10 years, the terrorists have already won. Or something.
"one of the most important targets on the planet" (Score:5, Funny)
Gauss Vs. Glue (Score:5, Funny)
"
Not a rail gun. (Score:5, Informative)
A rail gun is a parallel, non-touching pair of conductive rails, joined at the back-end by a partial circuit capable of generating an extremely high current flow (amps) of electicity in a very, very short time. A conductive projectile is injected into the gap between the rails (so that it touches both rails at once), which completes the circuit. As current flows from one rail to the other, through the projectile, it generates a powerful magnetic field. The Lorentz force causes the projectile to be pushed toward the far end of the rails--the magnitude of the force depends on the current flow.
Rail guns can achieve extremely high velocities, far higher than conventional explosive-charge guns. The velocity of a firearm projectile is limited by the velocity of the expanding explosive gasses that propel it out of the barrel; the gas velocity is in turn limited by the speed of sound in the gas medium, which has a physical upper limit for any type of explosive. Rail guns don't suffer from this limitation.
I have seen references to a 'Gauss gun' which consists of a series of solenoids stationed along a tube barrel, timed to trigger so that a ferrous metal projectile will be pulled faster and faster down the barrel by each of the solenoids in turn. I don't know how valid this terminology is, though.
Parent
First deployment should be.... (Score:5, Funny)
Suggestion for the first test: Enter it in next year's Punkin Chunkin' [punkinchunkin.com] contest!
one ring to launch them all (Score:5, Funny)
A few points (Score:5, Insightful)
New Scientist points out that if such a launch ring were built, it would instantly become "one of the most important targets on the planet.
What a moronic comment.
You have a STATIC launcher.
It can toss things into ballistic trajectories.
One at a time.
With a warm-up of TENS OF HOURS.
I don't know if New Scientist realized this, but we have launch technologies that are
a) less vulnerable
b) more accurate
c) mobile
and
d) a little quicker to fire than that.
On another note, and not that this will mollify the crowd that fears a weapon in every technology, but in regards to the difficulty of punching something through the atmosphere at Mach 23, I seem to recall SDI experiments where a high-power laser was used to heat a 'track' through the atmosphere (in that case, to fire a particle beam weapon down the track with less atmospheric attenuation ). Couldn't a similar idea significantly reduce the air resistance for this sort of a projectile?
Why not reduce acceleration? (Score:3, Interesting)
"When the sled had been accelerated to its top speed of 10 kilometres per second, laser and pyrotechnic devices would be used to separate the cone from the sled. Then, the cone would skid into a side tunnel, losing some speed due to friction with the tunnel's walls. The tunnel would direct the cone to a ramp angled at 30 to the horizon, where the cone would launch towards space at about 8 kilometres per second, or more than 23 times the speed of sound. ... Anything launched in this way would have to be able to survive enormous accelerations - more than 2000 times the acceleration due to gravity (2000g)."
They claim that the payload would be accelerated slowly around the ring. The huge acceleration occurs when the payload's trajectory is changed to angle it up 30 degrees towards the sky. Why wouldn't they angle the ring itself at 30 degrees, releasing the payload at the point where the tangent points up at 30 degrees? They wouldn't need a ramp at all, just a piece that moves out of the way before the payload swings around the loop again.
Re:Why not reduce acceleration? (Score:5, Insightful)
Parent
Most important target.... (Score:5, Insightful)
Anywhere the capability exists to put a payload into orbit is a target.
That "most important target" bit was a simple piece of scaremongering.
Gerald Bull (Score:4, Insightful)
Gerald Bull had a vision and an obsession, a vision that led to estrangement from his native Canada, prison in America, and ultimately assassination by Israel. His vision was of an entirely new way to get into space: small rockets boosted by giant guns. To achieve it he worked for some of the worst regimes on earth: South Africa, China, and ultimately Iraq. His work affected the course of two modern wars and revived the ancient field of artillery.
It's not for people or sensitive electronics (Score:5, Interesting)
Bad math? (Score:5, Informative)
The acceleration equation for circular motion is: a = v^2 / r
We are given:
Velocity: 10 kilometers/s
Width of ring = 2 kilometers, so radius = 1 kilometer
So:
v = 10,000 m/s
r = 1,000 m
a = (10,000 m/s * 10,000 m/s) / (1,000 meters) = 100,000 m/s^2
The acceleration due to gravity is about 10 m/s^2
This gives: (100,000 m/s^2) / (10 m/s^2) = 10,000 g
So it seems that their 2,000 g is way off. Even if we use 2 km for the radius it is still 5,000 g.
Re:Bad math? (Score:5, Informative)
Parent
Fuel and Water (Score:5, Interesting)
The down fall is that the privatization world will probably be a bit upset about this.
Fast dead mass is still REALLY useful if its cheap (Score:4, Informative)
This method saves a lot of reaction mass in a heavy lifter because you can aim for a high alitutde but a suborbital trajectory. IE it's easier to shoot straight up than curve towards an orbital path at sufficient speed. For instance the X prize is all about sub-orbital. LEO is much harder and GEO is even harder still.
Re: (Score:3, Interesting)
I don't know the numbers, but the bulk of a conventional rocket fuel us used up getting the last bit of fuel to near orbit. So the for example, the first 100kg of fuel is used lifting the last 10kg of fuel.
With this ring type of accelerator, there is no basically no fuel onboard to used to enter orbit, so you don't need the resulting mass to acc
If they build two... (Score:3, Funny)
Here: (Score:5, Informative)
Now you're aware...
Parent
Re: (Score:3, Informative)
The laser designator for the Copperheads was quite large, the ones I saw
Re: (Score:3, Insightful)
You forget that it's circular. It's accelerating by changing direction as well as increasing speed.